Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback design to work with QEMU and rust-vmm vhost-user backend without require any changes. Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com> Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9
author: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com> 2023-10-10 11:40:56 +0000
committer: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com> 2023-10-10 11:40:56 +0000
commit: e02cda008591317b1625707ff8e115a4841aa889 (patch)
tree: aee302e3cf8b59ec2d32ec481be3d1afddfc8968 /nbd
parent: cc668e6b7e0ffd8c9d130513d12053cf5eda1d3b (diff)
8 files changed, 5066 insertions, 0 deletions
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
new file mode 100644
index 000000000..695f85575
--- /dev/null
+++ b/nbd/client-connection.c
@@ -0,0 +1,389 @@
+/*
+ * QEMU Block driver for  NBD
+ *
+ * Copyright (c) 2021 Virtuozzo International GmbH.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/nbd.h"
+
+#include "qapi/qapi-visit-sockets.h"
+#include "qapi/clone-visitor.h"
+
+struct NBDClientConnection {
+    /* Initialization constants, never change */
+    SocketAddress *saddr; /* address to connect to */
+    QCryptoTLSCreds *tlscreds;
+    NBDExportInfo initial_info;
+    bool do_negotiation;
+    bool do_retry;
+
+    QemuMutex mutex;
+
+    /*
+     * @sioc and @err represent a connection attempt.  While running
+     * is true, they are only used by the connection thread, and mutex
+     * locking is not needed.  Once the thread finishes,
+     * nbd_co_establish_connection then steals these pointers while
+     * under the mutex.
+     */
+    NBDExportInfo updated_info;
+    QIOChannelSocket *sioc;
+    QIOChannel *ioc;
+    Error *err;
+
+    /* All further fields are accessed only under mutex */
+    bool running; /* thread is running now */
+    bool detached; /* thread is detached and should cleanup the state */
+
+    /*
+     * wait_co: if non-NULL, which coroutine to wake in
+     * nbd_co_establish_connection() after yield()
+     */
+    Coroutine *wait_co;
+};
+
+/*
+ * The function isn't protected by any mutex, only call it when the client
+ * connection attempt has not yet started.
+ */
+void nbd_client_connection_enable_retry(NBDClientConnection *conn)
+{
+    conn->do_retry = true;
+}
+
+NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
+                                               bool do_negotiation,
+                                               const char *export_name,
+                                               const char *x_dirty_bitmap,
+                                               QCryptoTLSCreds *tlscreds)
+{
+    NBDClientConnection *conn = g_new(NBDClientConnection, 1);
+
+    object_ref(OBJECT(tlscreds));
+    *conn = (NBDClientConnection) {
+        .saddr = QAPI_CLONE(SocketAddress, saddr),
+        .tlscreds = tlscreds,
+        .do_negotiation = do_negotiation,
+
+        .initial_info.request_sizes = true,
+        .initial_info.structured_reply = true,
+        .initial_info.base_allocation = true,
+        .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
+        .initial_info.name = g_strdup(export_name ?: "")
+    };
+
+    qemu_mutex_init(&conn->mutex);
+
+    return conn;
+}
+
+static void nbd_client_connection_do_free(NBDClientConnection *conn)
+{
+    if (conn->sioc) {
+        qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
+        object_unref(OBJECT(conn->sioc));
+    }
+    error_free(conn->err);
+    qapi_free_SocketAddress(conn->saddr);
+    object_unref(OBJECT(conn->tlscreds));
+    g_free(conn->initial_info.x_dirty_bitmap);
+    g_free(conn->initial_info.name);
+    g_free(conn);
+}
+
+/*
+ * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
+ * are given @outioc is returned. @outioc is provided only on success.  The call
+ * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
+ */
+static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
+                       NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
+                       QIOChannel **outioc, Error **errp)
+{
+    int ret;
+
+    if (outioc) {
+        *outioc = NULL;
+    }
+
+    ret = qio_channel_socket_connect_sync(sioc, addr, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
+
+    if (!info) {
+        return 0;
+    }
+
+    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
+                                tlscreds ? addr->u.inet.host : NULL,
+                                outioc, info, errp);
+    if (ret < 0) {
+        /*
+         * nbd_receive_negotiate() may setup tls ioc and return it even on
+         * failure path. In this case we should use it instead of original
+         * channel.
+         */
+        if (outioc && *outioc) {
+            qio_channel_close(QIO_CHANNEL(*outioc), NULL);
+            object_unref(OBJECT(*outioc));
+            *outioc = NULL;
+        } else {
+            qio_channel_close(QIO_CHANNEL(sioc), NULL);
+        }
+
+        return ret;
+    }
+
+    return 0;
+}
+
+static void *connect_thread_func(void *opaque)
+{
+    NBDClientConnection *conn = opaque;
+    int ret;
+    bool do_free;
+    uint64_t timeout = 1;
+    uint64_t max_timeout = 16;
+
+    qemu_mutex_lock(&conn->mutex);
+    while (!conn->detached) {
+        assert(!conn->sioc);
+        conn->sioc = qio_channel_socket_new();
+
+        qemu_mutex_unlock(&conn->mutex);
+
+        error_free(conn->err);
+        conn->err = NULL;
+        conn->updated_info = conn->initial_info;
+
+        ret = nbd_connect(conn->sioc, conn->saddr,
+                          conn->do_negotiation ? &conn->updated_info : NULL,
+                          conn->tlscreds, &conn->ioc, &conn->err);
+
+        /*
+         * conn->updated_info will finally be returned to the user. Clear the
+         * pointers to our internally allocated strings, which are IN parameters
+         * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
+         * shoudn't be interested in these fields.
+         */
+        conn->updated_info.x_dirty_bitmap = NULL;
+        conn->updated_info.name = NULL;
+
+        qemu_mutex_lock(&conn->mutex);
+
+        if (ret < 0) {
+            object_unref(OBJECT(conn->sioc));
+            conn->sioc = NULL;
+            if (conn->do_retry && !conn->detached) {
+                qemu_mutex_unlock(&conn->mutex);
+
+                sleep(timeout);
+                if (timeout < max_timeout) {
+                    timeout *= 2;
+                }
+
+                qemu_mutex_lock(&conn->mutex);
+                continue;
+            }
+        }
+
+        break;
+    }
+
+    /* mutex is locked */
+
+    assert(conn->running);
+    conn->running = false;
+    if (conn->wait_co) {
+        aio_co_wake(conn->wait_co);
+        conn->wait_co = NULL;
+    }
+    do_free = conn->detached;
+
+    qemu_mutex_unlock(&conn->mutex);
+
+    if (do_free) {
+        nbd_client_connection_do_free(conn);
+    }
+
+    return NULL;
+}
+
+void nbd_client_connection_release(NBDClientConnection *conn)
+{
+    bool do_free = false;
+
+    if (!conn) {
+        return;
+    }
+
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        assert(!conn->detached);
+        if (conn->running) {
+            conn->detached = true;
+        } else {
+            do_free = true;
+        }
+        if (conn->sioc) {
+            qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
+                                 QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+        }
+    }
+
+    if (do_free) {
+        nbd_client_connection_do_free(conn);
+    }
+}
+
+/*
+ * Get a new connection in context of @conn:
+ *   if the thread is running, wait for completion
+ *   if the thread already succeeded in the background, and user didn't get the
+ *     result, just return it now
+ *   otherwise the thread is not running, so start a thread and wait for
+ *     completion
+ *
+ * If @blocking is false, don't wait for the thread, return immediately.
+ *
+ * If @info is not NULL, also do nbd-negotiation after successful connection.
+ * In this case info is used only as out parameter, and is fully initialized by
+ * nbd_co_establish_connection(). "IN" fields of info as well as related only to
+ * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
+ * include/block/nbd.h).
+ */
+QIOChannel *coroutine_fn
+nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
+                            bool blocking, Error **errp)
+{
+    QemuThread thread;
+
+    if (conn->do_negotiation) {
+        assert(info);
+    }
+
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        /*
+         * Don't call nbd_co_establish_connection() in several coroutines in
+         * parallel. Only one call at once is supported.
+         */
+        assert(!conn->wait_co);
+
+        if (!conn->running) {
+            if (conn->sioc) {
+                /* Previous attempt finally succeeded in background */
+                if (conn->do_negotiation) {
+                    memcpy(info, &conn->updated_info, sizeof(*info));
+                    if (conn->ioc) {
+                        /* TLS channel now has own reference to parent */
+                        object_unref(OBJECT(conn->sioc));
+                        conn->sioc = NULL;
+
+                        return g_steal_pointer(&conn->ioc);
+                    }
+                }
+
+                assert(!conn->ioc);
+
+                return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
+            }
+
+            conn->running = true;
+            error_free(conn->err);
+            conn->err = NULL;
+            qemu_thread_create(&thread, "nbd-connect",
+                               connect_thread_func, conn, QEMU_THREAD_DETACHED);
+        }
+
+        if (!blocking) {
+            error_setg(errp, "No connection at the moment");
+            return NULL;
+        }
+
+        conn->wait_co = qemu_coroutine_self();
+    }
+
+    /*
+     * We are going to wait for connect-thread finish, but
+     * nbd_co_establish_connection_cancel() can interrupt.
+     */
+    qemu_coroutine_yield();
+
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        if (conn->running) {
+            /*
+             * The connection attempt was canceled and the coroutine resumed
+             * before the connection thread finished its job.  Report the
+             * attempt as failed, but leave the connection thread running,
+             * to reuse it for the next connection attempt.
+             */
+            error_setg(errp, "Connection attempt cancelled by other operation");
+            return NULL;
+        } else {
+            error_propagate(errp, conn->err);
+            conn->err = NULL;
+            if (!conn->sioc) {
+                return NULL;
+            }
+            if (conn->do_negotiation) {
+                memcpy(info, &conn->updated_info, sizeof(*info));
+                if (conn->ioc) {
+                    /* TLS channel now has own reference to parent */
+                    object_unref(OBJECT(conn->sioc));
+                    conn->sioc = NULL;
+
+                    return g_steal_pointer(&conn->ioc);
+                }
+            }
+
+            assert(!conn->ioc);
+
+            return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
+        }
+    }
+
+    abort(); /* unreachable */
+}
+
+/*
+ * nbd_co_establish_connection_cancel
+ * Cancel nbd_co_establish_connection() asynchronously.
+ *
+ * Note that this function neither directly stops the thread nor closes the
+ * socket, but rather safely wakes nbd_co_establish_connection() which is
+ * sleeping in yield()
+ */
+void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
+{
+    Coroutine *wait_co;
+
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        wait_co = g_steal_pointer(&conn->wait_co);
+    }
+
+    if (wait_co) {
+        aio_co_wake(wait_co);
+    }
+}
diff --git a/nbd/client.c b/nbd/client.c
new file mode 100644
index 000000000..30d5383cb
--- /dev/null
+++ b/nbd/client.c
@@ -0,0 +1,1512 @@
+/*
+ *  Copyright (C) 2016-2019 Red Hat, Inc.
+ *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
+ *
+ *  Network Block Device Client Side
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; under version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/queue.h"
+#include "trace.h"
+#include "nbd-internal.h"
+#include "qemu/cutils.h"
+
+/* Definitions for opaque data types */
+
+static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
+
+/* That's all folks */
+
+/* Basic flow for negotiation
+
+   Server         Client
+   Negotiate
+
+   or
+
+   Server         Client
+   Negotiate #1
+                  Option
+   Negotiate #2
+
+   ----
+
+   followed by
+
+   Server         Client
+                  Request
+   Response
+                  Request
+   Response
+                  ...
+   ...
+                  Request (type == 2)
+
+*/
+
+/* Send an option request.
+ *
+ * The request is for option @opt, with @data containing @len bytes of
+ * additional payload for the request (@len may be -1 to treat @data as
+ * a C string; and @data may be NULL if @len is 0).
+ * Return 0 if successful, -1 with errp set if it is impossible to
+ * continue. */
+static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
+                                   uint32_t len, const char *data,
+                                   Error **errp)
+{
+    ERRP_GUARD();
+    NBDOption req;
+    QEMU_BUILD_BUG_ON(sizeof(req) != 16);
+
+    if (len == -1) {
+        req.length = len = strlen(data);
+    }
+    trace_nbd_send_option_request(opt, nbd_opt_lookup(opt), len);
+
+    stq_be_p(&req.magic, NBD_OPTS_MAGIC);
+    stl_be_p(&req.option, opt);
+    stl_be_p(&req.length, len);
+
+    if (nbd_write(ioc, &req, sizeof(req), errp) < 0) {
+        error_prepend(errp, "Failed to send option request header: ");
+        return -1;
+    }
+
+    if (len && nbd_write(ioc, (char *) data, len, errp) < 0) {
+        error_prepend(errp, "Failed to send option request data: ");
+        return -1;
+    }
+
+    return 0;
+}
+
+/* Send NBD_OPT_ABORT as a courtesy to let the server know that we are
+ * not going to attempt further negotiation. */
+static void nbd_send_opt_abort(QIOChannel *ioc)
+{
+    /* Technically, a compliant server is supposed to reply to us; but
+     * older servers disconnected instead. At any rate, we're allowed
+     * to disconnect without waiting for the server reply, so we don't
+     * even care if the request makes it to the server, let alone
+     * waiting around for whether the server replies. */
+    nbd_send_option_request(ioc, NBD_OPT_ABORT, 0, NULL, NULL);
+}
+
+
+/* Receive the header of an option reply, which should match the given
+ * opt.  Read through the length field, but NOT the length bytes of
+ * payload. Return 0 if successful, -1 with errp set if it is
+ * impossible to continue. */
+static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
+                                    NBDOptionReply *reply, Error **errp)
+{
+    QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
+    if (nbd_read(ioc, reply, sizeof(*reply), "option reply", errp) < 0) {
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    reply->magic = be64_to_cpu(reply->magic);
+    reply->option = be32_to_cpu(reply->option);
+    reply->type = be32_to_cpu(reply->type);
+    reply->length = be32_to_cpu(reply->length);
+
+    trace_nbd_receive_option_reply(reply->option, nbd_opt_lookup(reply->option),
+                                   reply->type, nbd_rep_lookup(reply->type),
+                                   reply->length);
+
+    if (reply->magic != NBD_REP_MAGIC) {
+        error_setg(errp, "Unexpected option reply magic");
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    if (reply->option != opt) {
+        error_setg(errp, "Unexpected option type %u (%s), expected %u (%s)",
+                   reply->option, nbd_opt_lookup(reply->option),
+                   opt, nbd_opt_lookup(opt));
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    return 0;
+}
+
+/*
+ * If reply represents success, return 1 without further action.  If
+ * reply represents an error, consume the optional payload of the
+ * packet on ioc.  Then return 0 for unsupported (so the client can
+ * fall back to other approaches), where @strict determines if only
+ * ERR_UNSUP or all errors fit that category, or -1 with errp set for
+ * other errors.
+ */
+static int nbd_handle_reply_err(QIOChannel *ioc, NBDOptionReply *reply,
+                                bool strict, Error **errp)
+{
+    ERRP_GUARD();
+    g_autofree char *msg = NULL;
+
+    if (!(reply->type & (1 << 31))) {
+        return 1;
+    }
+
+    if (reply->length) {
+        if (reply->length > NBD_MAX_BUFFER_SIZE) {
+            error_setg(errp, "server error %" PRIu32
+                       " (%s) message is too long",
+                       reply->type, nbd_rep_lookup(reply->type));
+            goto err;
+        }
+        msg = g_malloc(reply->length + 1);
+        if (nbd_read(ioc, msg, reply->length, NULL, errp) < 0) {
+            error_prepend(errp, "Failed to read option error %" PRIu32
+                          " (%s) message: ",
+                          reply->type, nbd_rep_lookup(reply->type));
+            goto err;
+        }
+        msg[reply->length] = '\0';
+        trace_nbd_server_error_msg(reply->type,
+                                   nbd_reply_type_lookup(reply->type), msg);
+    }
+
+    if (reply->type == NBD_REP_ERR_UNSUP || !strict) {
+        trace_nbd_reply_err_ignored(reply->option,
+                                    nbd_opt_lookup(reply->option),
+                                    reply->type, nbd_rep_lookup(reply->type));
+        return 0;
+    }
+
+    switch (reply->type) {
+    case NBD_REP_ERR_POLICY:
+        error_setg(errp, "Denied by server for option %" PRIu32 " (%s)",
+                   reply->option, nbd_opt_lookup(reply->option));
+        break;
+
+    case NBD_REP_ERR_INVALID:
+        error_setg(errp, "Invalid parameters for option %" PRIu32 " (%s)",
+                   reply->option, nbd_opt_lookup(reply->option));
+        break;
+
+    case NBD_REP_ERR_PLATFORM:
+        error_setg(errp, "Server lacks support for option %" PRIu32 " (%s)",
+                   reply->option, nbd_opt_lookup(reply->option));
+        break;
+
+    case NBD_REP_ERR_TLS_REQD:
+        error_setg(errp, "TLS negotiation required before option %" PRIu32
+                   " (%s)", reply->option, nbd_opt_lookup(reply->option));
+        error_append_hint(errp, "Did you forget a valid tls-creds?\n");
+        break;
+
+    case NBD_REP_ERR_UNKNOWN:
+        error_setg(errp, "Requested export not available");
+        break;
+
+    case NBD_REP_ERR_SHUTDOWN:
+        error_setg(errp, "Server shutting down before option %" PRIu32 " (%s)",
+                   reply->option, nbd_opt_lookup(reply->option));
+        break;
+
+    case NBD_REP_ERR_BLOCK_SIZE_REQD:
+        error_setg(errp, "Server requires INFO_BLOCK_SIZE for option %" PRIu32
+                   " (%s)", reply->option, nbd_opt_lookup(reply->option));
+        break;
+
+    default:
+        error_setg(errp, "Unknown error code when asking for option %" PRIu32
+                   " (%s)", reply->option, nbd_opt_lookup(reply->option));
+        break;
+    }
+
+    if (msg) {
+        error_append_hint(errp, "server reported: %s\n", msg);
+    }
+
+ err:
+    nbd_send_opt_abort(ioc);
+    return -1;
+}
+
+/* nbd_receive_list:
+ * Process another portion of the NBD_OPT_LIST reply, populating any
+ * name received into *@name. If @description is non-NULL, and the
+ * server provided a description, that is also populated. The caller
+ * must eventually call g_free() on success.
+ * Returns 1 if name and description were set and iteration must continue,
+ *         0 if iteration is complete (including if OPT_LIST unsupported),
+ *         -1 with @errp set if an unrecoverable error occurred.
+ */
+static int nbd_receive_list(QIOChannel *ioc, char **name, char **description,
+                            Error **errp)
+{
+    NBDOptionReply reply;
+    uint32_t len;
+    uint32_t namelen;
+    g_autofree char *local_name = NULL;
+    g_autofree char *local_desc = NULL;
+    int error;
+
+    if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
+        return -1;
+    }
+    error = nbd_handle_reply_err(ioc, &reply, true, errp);
+    if (error <= 0) {
+        return error;
+    }
+    len = reply.length;
+
+    if (reply.type == NBD_REP_ACK) {
+        if (len != 0) {
+            error_setg(errp, "length too long for option end");
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        return 0;
+    } else if (reply.type != NBD_REP_SERVER) {
+        error_setg(errp, "Unexpected reply type %u (%s), expected %u (%s)",
+                   reply.type, nbd_rep_lookup(reply.type),
+                   NBD_REP_SERVER, nbd_rep_lookup(NBD_REP_SERVER));
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
+        error_setg(errp, "incorrect option length %" PRIu32, len);
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    if (nbd_read32(ioc, &namelen, "option name length", errp) < 0) {
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    len -= sizeof(namelen);
+    if (len < namelen || namelen > NBD_MAX_STRING_SIZE) {
+        error_setg(errp, "incorrect name length in server's list response");
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    local_name = g_malloc(namelen + 1);
+    if (nbd_read(ioc, local_name, namelen, "export name", errp) < 0) {
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    local_name[namelen] = '\0';
+    len -= namelen;
+    if (len) {
+        if (len > NBD_MAX_STRING_SIZE) {
+            error_setg(errp, "incorrect description length in server's "
+                       "list response");
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        local_desc = g_malloc(len + 1);
+        if (nbd_read(ioc, local_desc, len, "export description", errp) < 0) {
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        local_desc[len] = '\0';
+    }
+
+    trace_nbd_receive_list(local_name, local_desc ?: "");
+    *name = g_steal_pointer(&local_name);
+    if (description) {
+        *description = g_steal_pointer(&local_desc);
+    }
+    return 1;
+}
+
+
+/*
+ * nbd_opt_info_or_go:
+ * Send option for NBD_OPT_INFO or NBD_OPT_GO and parse the reply.
+ * Returns -1 if the option proves the export @info->name cannot be
+ * used, 0 if the option is unsupported (fall back to NBD_OPT_LIST and
+ * NBD_OPT_EXPORT_NAME in that case), and > 0 if the export is good to
+ * go (with the rest of @info populated).
+ */
+static int nbd_opt_info_or_go(QIOChannel *ioc, uint32_t opt,
+                              NBDExportInfo *info, Error **errp)
+{
+    ERRP_GUARD();
+    NBDOptionReply reply;
+    uint32_t len = strlen(info->name);
+    uint16_t type;
+    int error;
+    char *buf;
+
+    /* The protocol requires that the server send NBD_INFO_EXPORT with
+     * a non-zero flags (at least NBD_FLAG_HAS_FLAGS must be set); so
+     * flags still 0 is a witness of a broken server. */
+    info->flags = 0;
+
+    assert(opt == NBD_OPT_GO || opt == NBD_OPT_INFO);
+    trace_nbd_opt_info_go_start(nbd_opt_lookup(opt), info->name);
+    buf = g_malloc(4 + len + 2 + 2 * info->request_sizes + 1);
+    stl_be_p(buf, len);
+    memcpy(buf + 4, info->name, len);
+    /* At most one request, everything else up to server */
+    stw_be_p(buf + 4 + len, info->request_sizes);
+    if (info->request_sizes) {
+        stw_be_p(buf + 4 + len + 2, NBD_INFO_BLOCK_SIZE);
+    }
+    error = nbd_send_option_request(ioc, opt,
+                                    4 + len + 2 + 2 * info->request_sizes,
+                                    buf, errp);
+    g_free(buf);
+    if (error < 0) {
+        return -1;
+    }
+
+    while (1) {
+        if (nbd_receive_option_reply(ioc, opt, &reply, errp) < 0) {
+            return -1;
+        }
+        error = nbd_handle_reply_err(ioc, &reply, true, errp);
+        if (error <= 0) {
+            return error;
+        }
+        len = reply.length;
+
+        if (reply.type == NBD_REP_ACK) {
+            /*
+             * Server is done sending info, and moved into transmission
+             * phase for NBD_OPT_GO, but make sure it sent flags
+             */
+            if (len) {
+                error_setg(errp, "server sent invalid NBD_REP_ACK");
+                return -1;
+            }
+            if (!info->flags) {
+                error_setg(errp, "broken server omitted NBD_INFO_EXPORT");
+                return -1;
+            }
+            trace_nbd_opt_info_go_success(nbd_opt_lookup(opt));
+            return 1;
+        }
+        if (reply.type != NBD_REP_INFO) {
+            error_setg(errp, "unexpected reply type %u (%s), expected %u (%s)",
+                       reply.type, nbd_rep_lookup(reply.type),
+                       NBD_REP_INFO, nbd_rep_lookup(NBD_REP_INFO));
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        if (len < sizeof(type)) {
+            error_setg(errp, "NBD_REP_INFO length %" PRIu32 " is too short",
+                       len);
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        if (nbd_read16(ioc, &type, "info type", errp) < 0) {
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        len -= sizeof(type);
+        switch (type) {
+        case NBD_INFO_EXPORT:
+            if (len != sizeof(info->size) + sizeof(info->flags)) {
+                error_setg(errp, "remaining export info len %" PRIu32
+                           " is unexpected size", len);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (nbd_read64(ioc, &info->size, "info size", errp) < 0) {
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (nbd_read16(ioc, &info->flags, "info flags", errp) < 0) {
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (info->min_block &&
+                !QEMU_IS_ALIGNED(info->size, info->min_block)) {
+                error_setg(errp, "export size %" PRIu64 " is not multiple of "
+                           "minimum block size %" PRIu32, info->size,
+                           info->min_block);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
+            break;
+
+        case NBD_INFO_BLOCK_SIZE:
+            if (len != sizeof(info->min_block) * 3) {
+                error_setg(errp, "remaining export info len %" PRIu32
+                           " is unexpected size", len);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (nbd_read32(ioc, &info->min_block, "info minimum block size",
+                           errp) < 0) {
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (!is_power_of_2(info->min_block)) {
+                error_setg(errp, "server minimum block size %" PRIu32
+                           " is not a power of two", info->min_block);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (nbd_read32(ioc, &info->opt_block, "info preferred block size",
+                           errp) < 0)
+            {
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (!is_power_of_2(info->opt_block) ||
+                info->opt_block < info->min_block) {
+                error_setg(errp, "server preferred block size %" PRIu32
+                           " is not valid", info->opt_block);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (nbd_read32(ioc, &info->max_block, "info maximum block size",
+                           errp) < 0)
+            {
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            if (info->max_block < info->min_block) {
+                error_setg(errp, "server maximum block size %" PRIu32
+                           " is not valid", info->max_block);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            trace_nbd_opt_info_block_size(info->min_block, info->opt_block,
+                                          info->max_block);
+            break;
+
+        default:
+            /*
+             * Not worth the bother to check if NBD_INFO_NAME or
+             * NBD_INFO_DESCRIPTION exceed NBD_MAX_STRING_SIZE.
+             */
+            trace_nbd_opt_info_unknown(type, nbd_info_lookup(type));
+            if (nbd_drop(ioc, len, errp) < 0) {
+                error_prepend(errp, "Failed to read info payload: ");
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            break;
+        }
+    }
+}
+
+/* Return -1 on failure, 0 if wantname is an available export. */
+static int nbd_receive_query_exports(QIOChannel *ioc,
+                                     const char *wantname,
+                                     Error **errp)
+{
+    bool list_empty = true;
+    bool found_export = false;
+
+    trace_nbd_receive_query_exports_start(wantname);
+    if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
+        return -1;
+    }
+
+    while (1) {
+        char *name;
+        int ret = nbd_receive_list(ioc, &name, NULL, errp);
+
+        if (ret < 0) {
+            /* Server gave unexpected reply */
+            return -1;
+        } else if (ret == 0) {
+            /* Done iterating. */
+            if (list_empty) {
+                /*
+                 * We don't have enough context to tell a server that
+                 * sent an empty list apart from a server that does
+                 * not support the list command; but as this function
+                 * is just used to trigger a nicer error message
+                 * before trying NBD_OPT_EXPORT_NAME, assume the
+                 * export is available.
+                 */
+                return 0;
+            } else if (!found_export) {
+                error_setg(errp, "No export with name '%s' available",
+                           wantname);
+                nbd_send_opt_abort(ioc);
+                return -1;
+            }
+            trace_nbd_receive_query_exports_success(wantname);
+            return 0;
+        }
+        list_empty = false;
+        if (!strcmp(name, wantname)) {
+            found_export = true;
+        }
+        g_free(name);
+    }
+}
+
+/*
+ * nbd_request_simple_option: Send an option request, and parse the reply.
+ * @strict controls whether ERR_UNSUP or all errors produce 0 status.
+ * return 1 for successful negotiation,
+ *        0 if operation is unsupported,
+ *        -1 with errp set for any other error
+ */
+static int nbd_request_simple_option(QIOChannel *ioc, int opt, bool strict,
+                                     Error **errp)
+{
+    NBDOptionReply reply;
+    int error;
+
+    if (nbd_send_option_request(ioc, opt, 0, NULL, errp) < 0) {
+        return -1;
+    }
+
+    if (nbd_receive_option_reply(ioc, opt, &reply, errp) < 0) {
+        return -1;
+    }
+    error = nbd_handle_reply_err(ioc, &reply, strict, errp);
+    if (error <= 0) {
+        return error;
+    }
+
+    if (reply.type != NBD_REP_ACK) {
+        error_setg(errp, "Server answered option %d (%s) with unexpected "
+                   "reply %" PRIu32 " (%s)", opt, nbd_opt_lookup(opt),
+                   reply.type, nbd_rep_lookup(reply.type));
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    if (reply.length != 0) {
+        error_setg(errp, "Option %d ('%s') response length is %" PRIu32
+                   " (it should be zero)", opt, nbd_opt_lookup(opt),
+                   reply.length);
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    return 1;
+}
+
+static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
+                                        QCryptoTLSCreds *tlscreds,
+                                        const char *hostname, Error **errp)
+{
+    int ret;
+    QIOChannelTLS *tioc;
+    struct NBDTLSHandshakeData data = { 0 };
+
+    ret = nbd_request_simple_option(ioc, NBD_OPT_STARTTLS, true, errp);
+    if (ret <= 0) {
+        if (ret == 0) {
+            error_setg(errp, "Server don't support STARTTLS option");
+            nbd_send_opt_abort(ioc);
+        }
+        return NULL;
+    }
+
+    trace_nbd_receive_starttls_new_client();
+    tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
+    if (!tioc) {
+        return NULL;
+    }
+    qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
+    data.loop = g_main_loop_new(g_main_context_default(), FALSE);
+    trace_nbd_receive_starttls_tls_handshake();
+    qio_channel_tls_handshake(tioc,
+                              nbd_tls_handshake,
+                              &data,
+                              NULL,
+                              NULL);
+
+    if (!data.complete) {
+        g_main_loop_run(data.loop);
+    }
+    g_main_loop_unref(data.loop);
+    if (data.error) {
+        error_propagate(errp, data.error);
+        object_unref(OBJECT(tioc));
+        return NULL;
+    }
+
+    return QIO_CHANNEL(tioc);
+}
+
+/*
+ * nbd_send_meta_query:
+ * Send 0 or 1 set/list meta context queries.
+ * Return 0 on success, -1 with errp set for any error
+ */
+static int nbd_send_meta_query(QIOChannel *ioc, uint32_t opt,
+                               const char *export, const char *query,
+                               Error **errp)
+{
+    int ret;
+    uint32_t export_len = strlen(export);
+    uint32_t queries = !!query;
+    uint32_t query_len = 0;
+    uint32_t data_len;
+    char *data;
+    char *p;
+
+    data_len = sizeof(export_len) + export_len + sizeof(queries);
+    assert(export_len <= NBD_MAX_STRING_SIZE);
+    if (query) {
+        query_len = strlen(query);
+        data_len += sizeof(query_len) + query_len;
+        assert(query_len <= NBD_MAX_STRING_SIZE);
+    } else {
+        assert(opt == NBD_OPT_LIST_META_CONTEXT);
+    }
+    p = data = g_malloc(data_len);
+
+    trace_nbd_opt_meta_request(nbd_opt_lookup(opt), query ?: "(all)", export);
+    stl_be_p(p, export_len);
+    memcpy(p += sizeof(export_len), export, export_len);
+    stl_be_p(p += export_len, queries);
+    if (query) {
+        stl_be_p(p += sizeof(queries), query_len);
+        memcpy(p += sizeof(query_len), query, query_len);
+    }
+
+    ret = nbd_send_option_request(ioc, opt, data_len, data, errp);
+    g_free(data);
+    return ret;
+}
+
+/*
+ * nbd_receive_one_meta_context:
+ * Called in a loop to receive and trace one set/list meta context reply.
+ * Pass non-NULL @name or @id to collect results back to the caller, which
+ * must eventually call g_free().
+ * return 1 if name is set and iteration must continue,
+ *        0 if iteration is complete (including if option is unsupported),
+ *        -1 with errp set for any error
+ */
+static int nbd_receive_one_meta_context(QIOChannel *ioc,
+                                        uint32_t opt,
+                                        char **name,
+                                        uint32_t *id,
+                                        Error **errp)
+{
+    int ret;
+    NBDOptionReply reply;
+    char *local_name = NULL;
+    uint32_t local_id;
+
+    if (nbd_receive_option_reply(ioc, opt, &reply, errp) < 0) {
+        return -1;
+    }
+
+    ret = nbd_handle_reply_err(ioc, &reply, false, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+
+    if (reply.type == NBD_REP_ACK) {
+        if (reply.length != 0) {
+            error_setg(errp, "Unexpected length to ACK response");
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        return 0;
+    } else if (reply.type != NBD_REP_META_CONTEXT) {
+        error_setg(errp, "Unexpected reply type %u (%s), expected %u (%s)",
+                   reply.type, nbd_rep_lookup(reply.type),
+                   NBD_REP_META_CONTEXT, nbd_rep_lookup(NBD_REP_META_CONTEXT));
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    if (reply.length <= sizeof(local_id) ||
+        reply.length > NBD_MAX_BUFFER_SIZE) {
+        error_setg(errp, "Failed to negotiate meta context, server "
+                   "answered with unexpected length %" PRIu32,
+                   reply.length);
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+
+    if (nbd_read32(ioc, &local_id, "context id", errp) < 0) {
+        return -1;
+    }
+
+    reply.length -= sizeof(local_id);
+    local_name = g_malloc(reply.length + 1);
+    if (nbd_read(ioc, local_name, reply.length, "context name", errp) < 0) {
+        g_free(local_name);
+        return -1;
+    }
+    local_name[reply.length] = '\0';
+    trace_nbd_opt_meta_reply(nbd_opt_lookup(opt), local_name, local_id);
+
+    if (name) {
+        *name = local_name;
+    } else {
+        g_free(local_name);
+    }
+    if (id) {
+        *id = local_id;
+    }
+    return 1;
+}
+
+/*
+ * nbd_negotiate_simple_meta_context:
+ * Request the server to set the meta context for export @info->name
+ * using @info->x_dirty_bitmap with a fallback to "base:allocation",
+ * setting @info->context_id to the resulting id. Fail if the server
+ * responds with more than one context or with a context different
+ * than the query.
+ * return 1 for successful negotiation,
+ *        0 if operation is unsupported,
+ *        -1 with errp set for any other error
+ */
+static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
+                                             NBDExportInfo *info,
+                                             Error **errp)
+{
+    /*
+     * TODO: Removing the x_dirty_bitmap hack will mean refactoring
+     * this function to request and store ids for multiple contexts
+     * (both base:allocation and a dirty bitmap), at which point this
+     * function should lose the term _simple.
+     */
+    int ret;
+    const char *context = info->x_dirty_bitmap ?: "base:allocation";
+    bool received = false;
+    char *name = NULL;
+
+    if (nbd_send_meta_query(ioc, NBD_OPT_SET_META_CONTEXT,
+                            info->name, context, errp) < 0) {
+        return -1;
+    }
+
+    ret = nbd_receive_one_meta_context(ioc, NBD_OPT_SET_META_CONTEXT,
+                                       &name, &info->context_id, errp);
+    if (ret < 0) {
+        return -1;
+    }
+    if (ret == 1) {
+        if (strcmp(context, name)) {
+            error_setg(errp, "Failed to negotiate meta context '%s', server "
+                       "answered with different context '%s'", context,
+                       name);
+            g_free(name);
+            nbd_send_opt_abort(ioc);
+            return -1;
+        }
+        g_free(name);
+        received = true;
+
+        ret = nbd_receive_one_meta_context(ioc, NBD_OPT_SET_META_CONTEXT,
+                                           NULL, NULL, errp);
+        if (ret < 0) {
+            return -1;
+        }
+    }
+    if (ret != 0) {
+        error_setg(errp, "Server answered with more than one context");
+        nbd_send_opt_abort(ioc);
+        return -1;
+    }
+    return received;
+}
+
+/*
+ * nbd_list_meta_contexts:
+ * Request the server to list all meta contexts for export @info->name.
+ * return 0 if list is complete (even if empty),
+ *        -1 with errp set for any error
+ */
+static int nbd_list_meta_contexts(QIOChannel *ioc,
+                                  NBDExportInfo *info,
+                                  Error **errp)
+{
+    int ret;
+    int seen_any = false;
+    int seen_qemu = false;
+
+    if (nbd_send_meta_query(ioc, NBD_OPT_LIST_META_CONTEXT,
+                            info->name, NULL, errp) < 0) {
+        return -1;
+    }
+
+    while (1) {
+        char *context;
+
+        ret = nbd_receive_one_meta_context(ioc, NBD_OPT_LIST_META_CONTEXT,
+                                           &context, NULL, errp);
+        if (ret == 0 && seen_any && !seen_qemu) {
+            /*
+             * Work around qemu 3.0 bug: the server forgot to send
+             * "qemu:" replies to 0 queries. If we saw at least one
+             * reply (probably base:allocation), but none of them were
+             * qemu:, then run a more specific query to make sure.
+             */
+            seen_qemu = true;
+            if (nbd_send_meta_query(ioc, NBD_OPT_LIST_META_CONTEXT,
+                                    info->name, "qemu:", errp) < 0) {
+                return -1;
+            }
+            continue;
+        }
+        if (ret <= 0) {
+            return ret;
+        }
+        seen_any = true;
+        seen_qemu |= strstart(context, "qemu:", NULL);
+        info->contexts = g_renew(char *, info->contexts, ++info->n_contexts);
+        info->contexts[info->n_contexts - 1] = context;
+    }
+}
+
+/*
+ * nbd_start_negotiate:
+ * Start the handshake to the server.  After a positive return, the server
+ * is ready to accept additional NBD_OPT requests.
+ * Returns: negative errno: failure talking to server
+ *          0: server is oldstyle, must call nbd_negotiate_finish_oldstyle
+ *          1: server is newstyle, but can only accept EXPORT_NAME
+ *          2: server is newstyle, but lacks structured replies
+ *          3: server is newstyle and set up for structured replies
+ */
+static int nbd_start_negotiate(AioContext *aio_context, QIOChannel *ioc,
+                               QCryptoTLSCreds *tlscreds,
+                               const char *hostname, QIOChannel **outioc,
+                               bool structured_reply, bool *zeroes,
+                               Error **errp)
+{
+    ERRP_GUARD();
+    uint64_t magic;
+
+    trace_nbd_start_negotiate(tlscreds, hostname ? hostname : "<null>");
+
+    if (zeroes) {
+        *zeroes = true;
+    }
+    if (outioc) {
+        *outioc = NULL;
+    }
+    if (tlscreds && !outioc) {
+        error_setg(errp, "Output I/O channel required for TLS");
+        return -EINVAL;
+    }
+
+    if (nbd_read64(ioc, &magic, "initial magic", errp) < 0) {
+        return -EINVAL;
+    }
+    trace_nbd_receive_negotiate_magic(magic);
+
+    if (magic != NBD_INIT_MAGIC) {
+        error_setg(errp, "Bad initial magic received: 0x%" PRIx64, magic);
+        return -EINVAL;
+    }
+
+    if (nbd_read64(ioc, &magic, "server magic", errp) < 0) {
+        return -EINVAL;
+    }
+    trace_nbd_receive_negotiate_magic(magic);
+
+    if (magic == NBD_OPTS_MAGIC) {
+        uint32_t clientflags = 0;
+        uint16_t globalflags;
+        bool fixedNewStyle = false;
+
+        if (nbd_read16(ioc, &globalflags, "server flags", errp) < 0) {
+            return -EINVAL;
+        }
+        trace_nbd_receive_negotiate_server_flags(globalflags);
+        if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
+            fixedNewStyle = true;
+            clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
+        }
+        if (globalflags & NBD_FLAG_NO_ZEROES) {
+            if (zeroes) {
+                *zeroes = false;
+            }
+            clientflags |= NBD_FLAG_C_NO_ZEROES;
+        }
+        /* client requested flags */
+        clientflags = cpu_to_be32(clientflags);
+        if (nbd_write(ioc, &clientflags, sizeof(clientflags), errp) < 0) {
+            error_prepend(errp, "Failed to send clientflags field: ");
+            return -EINVAL;
+        }
+        if (tlscreds) {
+            if (fixedNewStyle) {
+                *outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
+                if (!*outioc) {
+                    return -EINVAL;
+                }
+                ioc = *outioc;
+                if (aio_context) {
+                    qio_channel_set_blocking(ioc, false, NULL);
+                    qio_channel_attach_aio_context(ioc, aio_context);
+                }
+            } else {
+                error_setg(errp, "Server does not support STARTTLS");
+                return -EINVAL;
+            }
+        }
+        if (fixedNewStyle) {
+            int result = 0;
+
+            if (structured_reply) {
+                result = nbd_request_simple_option(ioc,
+                                                   NBD_OPT_STRUCTURED_REPLY,
+                                                   false, errp);
+                if (result < 0) {
+                    return -EINVAL;
+                }
+            }
+            return 2 + result;
+        } else {
+            return 1;
+        }
+    } else if (magic == NBD_CLIENT_MAGIC) {
+        if (tlscreds) {
+            error_setg(errp, "Server does not support STARTTLS");
+            return -EINVAL;
+        }
+        return 0;
+    } else {
+        error_setg(errp, "Bad server magic received: 0x%" PRIx64, magic);
+        return -EINVAL;
+    }
+}
+
+/*
+ * nbd_negotiate_finish_oldstyle:
+ * Populate @info with the size and export flags from an oldstyle server,
+ * but does not consume 124 bytes of reserved zero padding.
+ * Returns 0 on success, -1 with @errp set on failure
+ */
+static int nbd_negotiate_finish_oldstyle(QIOChannel *ioc, NBDExportInfo *info,
+                                         Error **errp)
+{
+    uint32_t oldflags;
+
+    if (nbd_read64(ioc, &info->size, "export length", errp) < 0) {
+        return -EINVAL;
+    }
+
+    if (nbd_read32(ioc, &oldflags, "export flags", errp) < 0) {
+        return -EINVAL;
+    }
+    if (oldflags & ~0xffff) {
+        error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
+        return -EINVAL;
+    }
+    info->flags = oldflags;
+    return 0;
+}
+
+/*
+ * nbd_receive_negotiate:
+ * Connect to server, complete negotiation, and move into transmission phase.
+ * Returns: negative errno: failure talking to server
+ *          0: server is connected
+ */
+int nbd_receive_negotiate(AioContext *aio_context, QIOChannel *ioc,
+                          QCryptoTLSCreds *tlscreds,
+                          const char *hostname, QIOChannel **outioc,
+                          NBDExportInfo *info, Error **errp)
+{
+    ERRP_GUARD();
+    int result;
+    bool zeroes;
+    bool base_allocation = info->base_allocation;
+
+    assert(info->name && strlen(info->name) <= NBD_MAX_STRING_SIZE);
+    trace_nbd_receive_negotiate_name(info->name);
+
+    result = nbd_start_negotiate(aio_context, ioc, tlscreds, hostname, outioc,
+                                 info->structured_reply, &zeroes, errp);
+
+    info->structured_reply = false;
+    info->base_allocation = false;
+    if (tlscreds && *outioc) {
+        ioc = *outioc;
+    }
+
+    switch (result) {
+    case 3: /* newstyle, with structured replies */
+        info->structured_reply = true;
+        if (base_allocation) {
+            result = nbd_negotiate_simple_meta_context(ioc, info, errp);
+            if (result < 0) {
+                return -EINVAL;
+            }
+            info->base_allocation = result == 1;
+        }
+        /* fall through */
+    case 2: /* newstyle, try OPT_GO */
+        /* Try NBD_OPT_GO first - if it works, we are done (it
+         * also gives us a good message if the server requires
+         * TLS).  If it is not available, fall back to
+         * NBD_OPT_LIST for nicer error messages about a missing
+         * export, then use NBD_OPT_EXPORT_NAME.  */
+        result = nbd_opt_info_or_go(ioc, NBD_OPT_GO, info, errp);
+        if (result < 0) {
+            return -EINVAL;
+        }
+        if (result > 0) {
+            return 0;
+        }
+        /* Check our desired export is present in the
+         * server export list. Since NBD_OPT_EXPORT_NAME
+         * cannot return an error message, running this
+         * query gives us better error reporting if the
+         * export name is not available.
+         */
+        if (nbd_receive_query_exports(ioc, info->name, errp) < 0) {
+            return -EINVAL;
+        }
+        /* fall through */
+    case 1: /* newstyle, but limited to EXPORT_NAME */
+        /* write the export name request */
+        if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, info->name,
+                                    errp) < 0) {
+            return -EINVAL;
+        }
+
+        /* Read the response */
+        if (nbd_read64(ioc, &info->size, "export length", errp) < 0) {
+            return -EINVAL;
+        }
+
+        if (nbd_read16(ioc, &info->flags, "export flags", errp) < 0) {
+            return -EINVAL;
+        }
+        break;
+    case 0: /* oldstyle, parse length and flags */
+        if (*info->name) {
+            error_setg(errp, "Server does not support non-empty export names");
+            return -EINVAL;
+        }
+        if (nbd_negotiate_finish_oldstyle(ioc, info, errp) < 0) {
+            return -EINVAL;
+        }
+        break;
+    default:
+        return result;
+    }
+
+    trace_nbd_receive_negotiate_size_flags(info->size, info->flags);
+    if (zeroes && nbd_drop(ioc, 124, errp) < 0) {
+        error_prepend(errp, "Failed to read reserved block: ");
+        return -EINVAL;
+    }
+    return 0;
+}
+
+/* Clean up result of nbd_receive_export_list */
+void nbd_free_export_list(NBDExportInfo *info, int count)
+{
+    int i, j;
+
+    if (!info) {
+        return;
+    }
+
+    for (i = 0; i < count; i++) {
+        g_free(info[i].name);
+        g_free(info[i].description);
+        for (j = 0; j < info[i].n_contexts; j++) {
+            g_free(info[i].contexts[j]);
+        }
+        g_free(info[i].contexts);
+    }
+    g_free(info);
+}
+
+/*
+ * nbd_receive_export_list:
+ * Query details about a server's exports, then disconnect without
+ * going into transmission phase. Return a count of the exports listed
+ * in @info by the server, or -1 on error. Caller must free @info using
+ * nbd_free_export_list().
+ */
+int nbd_receive_export_list(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
+                            const char *hostname, NBDExportInfo **info,
+                            Error **errp)
+{
+    int result;
+    int count = 0;
+    int i;
+    int rc;
+    int ret = -1;
+    NBDExportInfo *array = NULL;
+    QIOChannel *sioc = NULL;
+
+    *info = NULL;
+    result = nbd_start_negotiate(NULL, ioc, tlscreds, hostname, &sioc, true,
+                                 NULL, errp);
+    if (tlscreds && sioc) {
+        ioc = sioc;
+    }
+
+    switch (result) {
+    case 2:
+    case 3:
+        /* newstyle - use NBD_OPT_LIST to populate array, then try
+         * NBD_OPT_INFO on each array member. If structured replies
+         * are enabled, also try NBD_OPT_LIST_META_CONTEXT. */
+        if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
+            goto out;
+        }
+        while (1) {
+            char *name;
+            char *desc;
+
+            rc = nbd_receive_list(ioc, &name, &desc, errp);
+            if (rc < 0) {
+                goto out;
+            } else if (rc == 0) {
+                break;
+            }
+            array = g_renew(NBDExportInfo, array, ++count);
+            memset(&array[count - 1], 0, sizeof(*array));
+            array[count - 1].name = name;
+            array[count - 1].description = desc;
+            array[count - 1].structured_reply = result == 3;
+        }
+
+        for (i = 0; i < count; i++) {
+            array[i].request_sizes = true;
+            rc = nbd_opt_info_or_go(ioc, NBD_OPT_INFO, &array[i], errp);
+            if (rc < 0) {
+                goto out;
+            } else if (rc == 0) {
+                /*
+                 * Pointless to try rest of loop. If OPT_INFO doesn't work,
+                 * it's unlikely that meta contexts work either
+                 */
+                break;
+            }
+
+            if (result == 3 &&
+                nbd_list_meta_contexts(ioc, &array[i], errp) < 0) {
+                goto out;
+            }
+        }
+
+        /* Send NBD_OPT_ABORT as a courtesy before hanging up */
+        nbd_send_opt_abort(ioc);
+        break;
+    case 1: /* newstyle, but limited to EXPORT_NAME */
+        error_setg(errp, "Server does not support export lists");
+        /* We can't even send NBD_OPT_ABORT, so merely hang up */
+        goto out;
+    case 0: /* oldstyle, parse length and flags */
+        array = g_new0(NBDExportInfo, 1);
+        array->name = g_strdup("");
+        count = 1;
+
+        if (nbd_negotiate_finish_oldstyle(ioc, array, errp) < 0) {
+            goto out;
+        }
+
+        /* Send NBD_CMD_DISC as a courtesy to the server, but ignore all
+         * errors now that we have the information we wanted. */
+        if (nbd_drop(ioc, 124, NULL) == 0) {
+            NBDRequest request = { .type = NBD_CMD_DISC };
+
+            nbd_send_request(ioc, &request);
+        }
+        break;
+    default:
+        goto out;
+    }
+
+    *info = array;
+    array = NULL;
+    ret = count;
+
+ out:
+    qio_channel_shutdown(ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+    qio_channel_close(ioc, NULL);
+    object_unref(OBJECT(sioc));
+    nbd_free_export_list(array, count);
+    return ret;
+}
+
+#ifdef __linux__
+int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
+             Error **errp)
+{
+    unsigned long sector_size = MAX(BDRV_SECTOR_SIZE, info->min_block);
+    unsigned long sectors = info->size / sector_size;
+
+    /* FIXME: Once the kernel module is patched to honor block sizes,
+     * and to advertise that fact to user space, we should update the
+     * hand-off to the kernel to use any block sizes we learned. */
+    assert(!info->request_sizes);
+    if (info->size / sector_size != sectors) {
+        error_setg(errp, "Export size %" PRIu64 " too large for 32-bit kernel",
+                   info->size);
+        return -E2BIG;
+    }
+
+    trace_nbd_init_set_socket();
+
+    if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 0) {
+        int serrno = errno;
+        error_setg(errp, "Failed to set NBD socket");
+        return -serrno;
+    }
+
+    trace_nbd_init_set_block_size(sector_size);
+
+    if (ioctl(fd, NBD_SET_BLKSIZE, sector_size) < 0) {
+        int serrno = errno;
+        error_setg(errp, "Failed setting NBD block size");
+        return -serrno;
+    }
+
+    trace_nbd_init_set_size(sectors);
+    if (info->size % sector_size) {
+        trace_nbd_init_trailing_bytes(info->size % sector_size);
+    }
+
+    if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
+        int serrno = errno;
+        error_setg(errp, "Failed setting size (in blocks)");
+        return -serrno;
+    }
+
+    if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) info->flags) < 0) {
+        if (errno == ENOTTY) {
+            int read_only = (info->flags & NBD_FLAG_READ_ONLY) != 0;
+            trace_nbd_init_set_readonly();
+
+            if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
+                int serrno = errno;
+                error_setg(errp, "Failed setting read-only attribute");
+                return -serrno;
+            }
+        } else {
+            int serrno = errno;
+            error_setg(errp, "Failed setting flags");
+            return -serrno;
+        }
+    }
+
+    trace_nbd_init_finish();
+
+    return 0;
+}
+
+int nbd_client(int fd)
+{
+    int ret;
+    int serrno;
+
+    trace_nbd_client_loop();
+
+    ret = ioctl(fd, NBD_DO_IT);
+    if (ret < 0 && errno == EPIPE) {
+        /* NBD_DO_IT normally returns EPIPE when someone has disconnected
+         * the socket via NBD_DISCONNECT.  We do not want to return 1 in
+         * that case.
+         */
+        ret = 0;
+    }
+    serrno = errno;
+
+    trace_nbd_client_loop_ret(ret, strerror(serrno));
+
+    trace_nbd_client_clear_queue();
+    ioctl(fd, NBD_CLEAR_QUE);
+
+    trace_nbd_client_clear_socket();
+    ioctl(fd, NBD_CLEAR_SOCK);
+
+    errno = serrno;
+    return ret;
+}
+
+int nbd_disconnect(int fd)
+{
+    ioctl(fd, NBD_CLEAR_QUE);
+    ioctl(fd, NBD_DISCONNECT);
+    ioctl(fd, NBD_CLEAR_SOCK);
+    return 0;
+}
+
+#endif /* __linux__ */
+
+int nbd_send_request(QIOChannel *ioc, NBDRequest *request)
+{
+    uint8_t buf[NBD_REQUEST_SIZE];
+
+    trace_nbd_send_request(request->from, request->len, request->handle,
+                           request->flags, request->type,
+                           nbd_cmd_lookup(request->type));
+
+    stl_be_p(buf, NBD_REQUEST_MAGIC);
+    stw_be_p(buf + 4, request->flags);
+    stw_be_p(buf + 6, request->type);
+    stq_be_p(buf + 8, request->handle);
+    stq_be_p(buf + 16, request->from);
+    stl_be_p(buf + 24, request->len);
+
+    return nbd_write(ioc, buf, sizeof(buf), NULL);
+}
+
+/* nbd_receive_simple_reply
+ * Read simple reply except magic field (which should be already read).
+ * Payload is not read (payload is possible for CMD_READ, but here we even
+ * don't know whether it take place or not).
+ */
+static int nbd_receive_simple_reply(QIOChannel *ioc, NBDSimpleReply *reply,
+                                    Error **errp)
+{
+    int ret;
+
+    assert(reply->magic == NBD_SIMPLE_REPLY_MAGIC);
+
+    ret = nbd_read(ioc, (uint8_t *)reply + sizeof(reply->magic),
+                   sizeof(*reply) - sizeof(reply->magic), "reply", errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    reply->error = be32_to_cpu(reply->error);
+    reply->handle = be64_to_cpu(reply->handle);
+
+    return 0;
+}
+
+/* nbd_receive_structured_reply_chunk
+ * Read structured reply chunk except magic field (which should be already
+ * read).
+ * Payload is not read.
+ */
+static int nbd_receive_structured_reply_chunk(QIOChannel *ioc,
+                                              NBDStructuredReplyChunk *chunk,
+                                              Error **errp)
+{
+    int ret;
+
+    assert(chunk->magic == NBD_STRUCTURED_REPLY_MAGIC);
+
+    ret = nbd_read(ioc, (uint8_t *)chunk + sizeof(chunk->magic),
+                   sizeof(*chunk) - sizeof(chunk->magic), "structured chunk",
+                   errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    chunk->flags = be16_to_cpu(chunk->flags);
+    chunk->type = be16_to_cpu(chunk->type);
+    chunk->handle = be64_to_cpu(chunk->handle);
+    chunk->length = be32_to_cpu(chunk->length);
+
+    return 0;
+}
+
+/* nbd_read_eof
+ * Tries to read @size bytes from @ioc.
+ * Returns 1 on success
+ *         0 on eof, when no data was read (errp is not set)
+ *         negative errno on failure (errp is set)
+ */
+static inline int coroutine_fn
+nbd_read_eof(BlockDriverState *bs, QIOChannel *ioc, void *buffer, size_t size,
+             Error **errp)
+{
+    bool partial = false;
+
+    assert(size);
+    while (size > 0) {
+        struct iovec iov = { .iov_base = buffer, .iov_len = size };
+        ssize_t len;
+
+        len = qio_channel_readv(ioc, &iov, 1, errp);
+        if (len == QIO_CHANNEL_ERR_BLOCK) {
+            qio_channel_yield(ioc, G_IO_IN);
+            continue;
+        } else if (len < 0) {
+            return -EIO;
+        } else if (len == 0) {
+            if (partial) {
+                error_setg(errp,
+                           "Unexpected end-of-file before all bytes were read");
+                return -EIO;
+            } else {
+                return 0;
+            }
+        }
+
+        partial = true;
+        size -= len;
+        buffer = (uint8_t*) buffer + len;
+    }
+    return 1;
+}
+
+/* nbd_receive_reply
+ *
+ * Decreases bs->in_flight while waiting for a new reply. This yield is where
+ * we wait indefinitely and the coroutine must be able to be safely reentered
+ * for nbd_client_attach_aio_context().
+ *
+ * Returns 1 on success
+ *         0 on eof, when no data was read (errp is not set)
+ *         negative errno on failure (errp is set)
+ */
+int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc,
+                                   NBDReply *reply, Error **errp)
+{
+    int ret;
+    const char *type;
+
+    ret = nbd_read_eof(bs, ioc, &reply->magic, sizeof(reply->magic), errp);
+    if (ret <= 0) {
+        return ret;
+    }
+
+    reply->magic = be32_to_cpu(reply->magic);
+
+    switch (reply->magic) {
+    case NBD_SIMPLE_REPLY_MAGIC:
+        ret = nbd_receive_simple_reply(ioc, &reply->simple, errp);
+        if (ret < 0) {
+            break;
+        }
+        trace_nbd_receive_simple_reply(reply->simple.error,
+                                       nbd_err_lookup(reply->simple.error),
+                                       reply->handle);
+        break;
+    case NBD_STRUCTURED_REPLY_MAGIC:
+        ret = nbd_receive_structured_reply_chunk(ioc, &reply->structured, errp);
+        if (ret < 0) {
+            break;
+        }
+        type = nbd_reply_type_lookup(reply->structured.type);
+        trace_nbd_receive_structured_reply_chunk(reply->structured.flags,
+                                                 reply->structured.type, type,
+                                                 reply->structured.handle,
+                                                 reply->structured.length);
+        break;
+    default:
+        error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", reply->magic);
+        return -EINVAL;
+    }
+    if (ret < 0) {
+        return ret;
+    }
+
+    return 1;
+}
+
diff --git a/nbd/common.c b/nbd/common.c
new file mode 100644
index 000000000..ddfe7d118
--- /dev/null
+++ b/nbd/common.c
@@ -0,0 +1,250 @@
+/*
+ *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
+ *
+ *  Network Block Device Common Code
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; under version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "trace.h"
+#include "nbd-internal.h"
+
+/* Discard length bytes from channel.  Return -errno on failure and 0 on
+ * success */
+int nbd_drop(QIOChannel *ioc, size_t size, Error **errp)
+{
+    ssize_t ret = 0;
+    char small[1024];
+    char *buffer;
+
+    buffer = sizeof(small) >= size ? small : g_malloc(MIN(65536, size));
+    while (size > 0) {
+        ssize_t count = MIN(65536, size);
+        ret = nbd_read(ioc, buffer, MIN(65536, size), NULL, errp);
+
+        if (ret < 0) {
+            goto cleanup;
+        }
+        size -= count;
+    }
+
+ cleanup:
+    if (buffer != small) {
+        g_free(buffer);
+    }
+    return ret;
+}
+
+
+void nbd_tls_handshake(QIOTask *task,
+                       void *opaque)
+{
+    struct NBDTLSHandshakeData *data = opaque;
+
+    qio_task_propagate_error(task, &data->error);
+    data->complete = true;
+    g_main_loop_quit(data->loop);
+}
+
+
+const char *nbd_opt_lookup(uint32_t opt)
+{
+    switch (opt) {
+    case NBD_OPT_EXPORT_NAME:
+        return "export name";
+    case NBD_OPT_ABORT:
+        return "abort";
+    case NBD_OPT_LIST:
+        return "list";
+    case NBD_OPT_STARTTLS:
+        return "starttls";
+    case NBD_OPT_INFO:
+        return "info";
+    case NBD_OPT_GO:
+        return "go";
+    case NBD_OPT_STRUCTURED_REPLY:
+        return "structured reply";
+    case NBD_OPT_LIST_META_CONTEXT:
+        return "list meta context";
+    case NBD_OPT_SET_META_CONTEXT:
+        return "set meta context";
+    default:
+        return "<unknown>";
+    }
+}
+
+
+const char *nbd_rep_lookup(uint32_t rep)
+{
+    switch (rep) {
+    case NBD_REP_ACK:
+        return "ack";
+    case NBD_REP_SERVER:
+        return "server";
+    case NBD_REP_INFO:
+        return "info";
+    case NBD_REP_META_CONTEXT:
+        return "meta context";
+    case NBD_REP_ERR_UNSUP:
+        return "unsupported";
+    case NBD_REP_ERR_POLICY:
+        return "denied by policy";
+    case NBD_REP_ERR_INVALID:
+        return "invalid";
+    case NBD_REP_ERR_PLATFORM:
+        return "platform lacks support";
+    case NBD_REP_ERR_TLS_REQD:
+        return "TLS required";
+    case NBD_REP_ERR_UNKNOWN:
+        return "export unknown";
+    case NBD_REP_ERR_SHUTDOWN:
+        return "server shutting down";
+    case NBD_REP_ERR_BLOCK_SIZE_REQD:
+        return "block size required";
+    default:
+        return "<unknown>";
+    }
+}
+
+
+const char *nbd_info_lookup(uint16_t info)
+{
+    switch (info) {
+    case NBD_INFO_EXPORT:
+        return "export";
+    case NBD_INFO_NAME:
+        return "name";
+    case NBD_INFO_DESCRIPTION:
+        return "description";
+    case NBD_INFO_BLOCK_SIZE:
+        return "block size";
+    default:
+        return "<unknown>";
+    }
+}
+
+
+const char *nbd_cmd_lookup(uint16_t cmd)
+{
+    switch (cmd) {
+    case NBD_CMD_READ:
+        return "read";
+    case NBD_CMD_WRITE:
+        return "write";
+    case NBD_CMD_DISC:
+        return "disconnect";
+    case NBD_CMD_FLUSH:
+        return "flush";
+    case NBD_CMD_TRIM:
+        return "trim";
+    case NBD_CMD_CACHE:
+        return "cache";
+    case NBD_CMD_WRITE_ZEROES:
+        return "write zeroes";
+    case NBD_CMD_BLOCK_STATUS:
+        return "block status";
+    default:
+        return "<unknown>";
+    }
+}
+
+
+const char *nbd_reply_type_lookup(uint16_t type)
+{
+    switch (type) {
+    case NBD_REPLY_TYPE_NONE:
+        return "none";
+    case NBD_REPLY_TYPE_OFFSET_DATA:
+        return "data";
+    case NBD_REPLY_TYPE_OFFSET_HOLE:
+        return "hole";
+    case NBD_REPLY_TYPE_BLOCK_STATUS:
+        return "block status";
+    case NBD_REPLY_TYPE_ERROR:
+        return "generic error";
+    case NBD_REPLY_TYPE_ERROR_OFFSET:
+        return "error at offset";
+    default:
+        if (type & (1 << 15)) {
+            return "<unknown error>";
+        }
+        return "<unknown>";
+    }
+}
+
+
+const char *nbd_err_lookup(int err)
+{
+    switch (err) {
+    case NBD_SUCCESS:
+        return "success";
+    case NBD_EPERM:
+        return "EPERM";
+    case NBD_EIO:
+        return "EIO";
+    case NBD_ENOMEM:
+        return "ENOMEM";
+    case NBD_EINVAL:
+        return "EINVAL";
+    case NBD_ENOSPC:
+        return "ENOSPC";
+    case NBD_EOVERFLOW:
+        return "EOVERFLOW";
+    case NBD_ENOTSUP:
+        return "ENOTSUP";
+    case NBD_ESHUTDOWN:
+        return "ESHUTDOWN";
+    default:
+        return "<unknown>";
+    }
+}
+
+
+int nbd_errno_to_system_errno(int err)
+{
+    int ret;
+    switch (err) {
+    case NBD_SUCCESS:
+        ret = 0;
+        break;
+    case NBD_EPERM:
+        ret = EPERM;
+        break;
+    case NBD_EIO:
+        ret = EIO;
+        break;
+    case NBD_ENOMEM:
+        ret = ENOMEM;
+        break;
+    case NBD_ENOSPC:
+        ret = ENOSPC;
+        break;
+    case NBD_EOVERFLOW:
+        ret = EOVERFLOW;
+        break;
+    case NBD_ENOTSUP:
+        ret = ENOTSUP;
+        break;
+    case NBD_ESHUTDOWN:
+        ret = ESHUTDOWN;
+        break;
+    default:
+        trace_nbd_unknown_error(err);
+        /* fallthrough */
+    case NBD_EINVAL:
+        ret = EINVAL;
+        break;
+    }
+    return ret;
+}
diff --git a/nbd/meson.build b/nbd/meson.build
new file mode 100644
index 000000000..b26d70565
--- /dev/null
+++ b/nbd/meson.build
@@ -0,0 +1,8 @@
+block_ss.add(files(
+  'client.c',
+  'client-connection.c',
+  'common.c',
+))
+blockdev_ss.add(files(
+  'server.c',
+))
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
new file mode 100644
index 000000000..1b2141ab4
--- /dev/null
+++ b/nbd/nbd-internal.h
@@ -0,0 +1,86 @@
+/*
+ * NBD Internal Declarations
+ *
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef NBD_INTERNAL_H
+#define NBD_INTERNAL_H
+#include "block/nbd.h"
+#include "sysemu/block-backend.h"
+#include "io/channel-tls.h"
+
+#include "qemu/coroutine.h"
+#include "qemu/iov.h"
+
+#ifndef _WIN32
+#include <sys/ioctl.h>
+#endif
+#ifdef HAVE_SYS_IOCCOM_H
+#include <sys/ioccom.h>
+#endif
+
+#ifdef __linux__
+#include <linux/fs.h>
+#endif
+
+#include "qemu/bswap.h"
+
+/* This is all part of the "official" NBD API.
+ *
+ * The most up-to-date documentation is available at:
+ * https://github.com/yoe/nbd/blob/master/doc/proto.md
+ */
+
+/* Size of all NBD_OPT_*, without payload */
+#define NBD_REQUEST_SIZE            (4 + 2 + 2 + 8 + 8 + 4)
+/* Size of all NBD_REP_* sent in answer to most NBD_OPT_*, without payload */
+#define NBD_REPLY_SIZE              (4 + 4 + 8)
+/* Size of reply to NBD_OPT_EXPORT_NAME */
+#define NBD_REPLY_EXPORT_NAME_SIZE  (8 + 2 + 124)
+/* Size of oldstyle negotiation */
+#define NBD_OLDSTYLE_NEGOTIATE_SIZE (8 + 8 + 8 + 4 + 124)
+
+#define NBD_INIT_MAGIC              0x4e42444d41474943LL /* ASCII "NBDMAGIC" */
+#define NBD_REQUEST_MAGIC           0x25609513
+#define NBD_OPTS_MAGIC              0x49484156454F5054LL /* ASCII "IHAVEOPT" */
+#define NBD_CLIENT_MAGIC            0x0000420281861253LL
+#define NBD_REP_MAGIC               0x0003e889045565a9LL
+
+#define NBD_SET_SOCK                _IO(0xab, 0)
+#define NBD_SET_BLKSIZE             _IO(0xab, 1)
+#define NBD_SET_SIZE                _IO(0xab, 2)
+#define NBD_DO_IT                   _IO(0xab, 3)
+#define NBD_CLEAR_SOCK              _IO(0xab, 4)
+#define NBD_CLEAR_QUE               _IO(0xab, 5)
+#define NBD_PRINT_DEBUG             _IO(0xab, 6)
+#define NBD_SET_SIZE_BLOCKS         _IO(0xab, 7)
+#define NBD_DISCONNECT              _IO(0xab, 8)
+#define NBD_SET_TIMEOUT             _IO(0xab, 9)
+#define NBD_SET_FLAGS               _IO(0xab, 10)
+
+/* nbd_write
+ * Writes @size bytes to @ioc. Returns 0 on success.
+ */
+static inline int nbd_write(QIOChannel *ioc, const void *buffer, size_t size,
+                            Error **errp)
+{
+    return qio_channel_write_all(ioc, buffer, size, errp) < 0 ? -EIO : 0;
+}
+
+struct NBDTLSHandshakeData {
+    GMainLoop *loop;
+    bool complete;
+    Error *error;
+};
+
+
+void nbd_tls_handshake(QIOTask *task,
+                       void *opaque);
+
+int nbd_drop(QIOChannel *ioc, size_t size, Error **errp);
+
+#endif
diff --git a/nbd/server.c b/nbd/server.c
new file mode 100644
index 000000000..4630dd732
--- /dev/null
+++ b/nbd/server.c
@@ -0,0 +1,2745 @@
+/*
+ *  Copyright (C) 2016-2021 Red Hat, Inc.
+ *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
+ *
+ *  Network Block Device Server Side
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; under version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/export.h"
+#include "qapi/error.h"
+#include "qemu/queue.h"
+#include "trace.h"
+#include "nbd-internal.h"
+#include "qemu/units.h"
+
+#define NBD_META_ID_BASE_ALLOCATION 0
+#define NBD_META_ID_ALLOCATION_DEPTH 1
+/* Dirty bitmaps use 'NBD_META_ID_DIRTY_BITMAP + i', so keep this id last. */
+#define NBD_META_ID_DIRTY_BITMAP 2
+
+/*
+ * NBD_MAX_BLOCK_STATUS_EXTENTS: 1 MiB of extents data. An empirical
+ * constant. If an increase is needed, note that the NBD protocol
+ * recommends no larger than 32 mb, so that the client won't consider
+ * the reply as a denial of service attack.
+ */
+#define NBD_MAX_BLOCK_STATUS_EXTENTS (1 * MiB / 8)
+
+static int system_errno_to_nbd_errno(int err)
+{
+    switch (err) {
+    case 0:
+        return NBD_SUCCESS;
+    case EPERM:
+    case EROFS:
+        return NBD_EPERM;
+    case EIO:
+        return NBD_EIO;
+    case ENOMEM:
+        return NBD_ENOMEM;
+#ifdef EDQUOT
+    case EDQUOT:
+#endif
+    case EFBIG:
+    case ENOSPC:
+        return NBD_ENOSPC;
+    case EOVERFLOW:
+        return NBD_EOVERFLOW;
+    case ENOTSUP:
+#if ENOTSUP != EOPNOTSUPP
+    case EOPNOTSUPP:
+#endif
+        return NBD_ENOTSUP;
+    case ESHUTDOWN:
+        return NBD_ESHUTDOWN;
+    case EINVAL:
+    default:
+        return NBD_EINVAL;
+    }
+}
+
+/* Definitions for opaque data types */
+
+typedef struct NBDRequestData NBDRequestData;
+
+struct NBDRequestData {
+    QSIMPLEQ_ENTRY(NBDRequestData) entry;
+    NBDClient *client;
+    uint8_t *data;
+    bool complete;
+};
+
+struct NBDExport {
+    BlockExport common;
+
+    char *name;
+    char *description;
+    uint64_t size;
+    uint16_t nbdflags;
+    QTAILQ_HEAD(, NBDClient) clients;
+    QTAILQ_ENTRY(NBDExport) next;
+
+    BlockBackend *eject_notifier_blk;
+    Notifier eject_notifier;
+
+    bool allocation_depth;
+    BdrvDirtyBitmap **export_bitmaps;
+    size_t nr_export_bitmaps;
+};
+
+static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
+
+/* NBDExportMetaContexts represents a list of contexts to be exported,
+ * as selected by NBD_OPT_SET_META_CONTEXT. Also used for
+ * NBD_OPT_LIST_META_CONTEXT. */
+typedef struct NBDExportMetaContexts {
+    NBDExport *exp;
+    size_t count; /* number of negotiated contexts */
+    bool base_allocation; /* export base:allocation context (block status) */
+    bool allocation_depth; /* export qemu:allocation-depth */
+    bool *bitmaps; /*
+                    * export qemu:dirty-bitmap:<export bitmap name>,
+                    * sized by exp->nr_export_bitmaps
+                    */
+} NBDExportMetaContexts;
+
+struct NBDClient {
+    int refcount;
+    void (*close_fn)(NBDClient *client, bool negotiated);
+
+    NBDExport *exp;
+    QCryptoTLSCreds *tlscreds;
+    char *tlsauthz;
+    QIOChannelSocket *sioc; /* The underlying data channel */
+    QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
+
+    Coroutine *recv_coroutine;
+
+    CoMutex send_lock;
+    Coroutine *send_coroutine;
+
+    bool read_yielding;
+    bool quiescing;
+
+    QTAILQ_ENTRY(NBDClient) next;
+    int nb_requests;
+    bool closing;
+
+    uint32_t check_align; /* If non-zero, check for aligned client requests */
+
+    bool structured_reply;
+    NBDExportMetaContexts export_meta;
+
+    uint32_t opt; /* Current option being negotiated */
+    uint32_t optlen; /* remaining length of data in ioc for the option being
+                        negotiated now */
+};
+
+static void nbd_client_receive_next_request(NBDClient *client);
+
+/* Basic flow for negotiation
+
+   Server         Client
+   Negotiate
+
+   or
+
+   Server         Client
+   Negotiate #1
+                  Option
+   Negotiate #2
+
+   ----
+
+   followed by
+
+   Server         Client
+                  Request
+   Response
+                  Request
+   Response
+                  ...
+   ...
+                  Request (type == 2)
+
+*/
+
+static inline void set_be_option_rep(NBDOptionReply *rep, uint32_t option,
+                                     uint32_t type, uint32_t length)
+{
+    stq_be_p(&rep->magic, NBD_REP_MAGIC);
+    stl_be_p(&rep->option, option);
+    stl_be_p(&rep->type, type);
+    stl_be_p(&rep->length, length);
+}
+
+/* Send a reply header, including length, but no payload.
+ * Return -errno on error, 0 on success. */
+static int nbd_negotiate_send_rep_len(NBDClient *client, uint32_t type,
+                                      uint32_t len, Error **errp)
+{
+    NBDOptionReply rep;
+
+    trace_nbd_negotiate_send_rep_len(client->opt, nbd_opt_lookup(client->opt),
+                                     type, nbd_rep_lookup(type), len);
+
+    assert(len < NBD_MAX_BUFFER_SIZE);
+
+    set_be_option_rep(&rep, client->opt, type, len);
+    return nbd_write(client->ioc, &rep, sizeof(rep), errp);
+}
+
+/* Send a reply header with default 0 length.
+ * Return -errno on error, 0 on success. */
+static int nbd_negotiate_send_rep(NBDClient *client, uint32_t type,
+                                  Error **errp)
+{
+    return nbd_negotiate_send_rep_len(client, type, 0, errp);
+}
+
+/* Send an error reply.
+ * Return -errno on error, 0 on success. */
+static int GCC_FMT_ATTR(4, 0)
+nbd_negotiate_send_rep_verr(NBDClient *client, uint32_t type,
+                            Error **errp, const char *fmt, va_list va)
+{
+    ERRP_GUARD();
+    g_autofree char *msg = NULL;
+    int ret;
+    size_t len;
+
+    msg = g_strdup_vprintf(fmt, va);
+    len = strlen(msg);
+    assert(len < NBD_MAX_STRING_SIZE);
+    trace_nbd_negotiate_send_rep_err(msg);
+    ret = nbd_negotiate_send_rep_len(client, type, len, errp);
+    if (ret < 0) {
+        return ret;
+    }
+    if (nbd_write(client->ioc, msg, len, errp) < 0) {
+        error_prepend(errp, "write failed (error message): ");
+        return -EIO;
+    }
+
+    return 0;
+}
+
+/*
+ * Return a malloc'd copy of @name suitable for use in an error reply.
+ */
+static char *
+nbd_sanitize_name(const char *name)
+{
+    if (strnlen(name, 80) < 80) {
+        return g_strdup(name);
+    }
+    /* XXX Should we also try to sanitize any control characters? */
+    return g_strdup_printf("%.80s...", name);
+}
+
+/* Send an error reply.
+ * Return -errno on error, 0 on success. */
+static int GCC_FMT_ATTR(4, 5)
+nbd_negotiate_send_rep_err(NBDClient *client, uint32_t type,
+                           Error **errp, const char *fmt, ...)
+{
+    va_list va;
+    int ret;
+
+    va_start(va, fmt);
+    ret = nbd_negotiate_send_rep_verr(client, type, errp, fmt, va);
+    va_end(va);
+    return ret;
+}
+
+/* Drop remainder of the current option, and send a reply with the
+ * given error type and message. Return -errno on read or write
+ * failure; or 0 if connection is still live. */
+static int GCC_FMT_ATTR(4, 0)
+nbd_opt_vdrop(NBDClient *client, uint32_t type, Error **errp,
+              const char *fmt, va_list va)
+{
+    int ret = nbd_drop(client->ioc, client->optlen, errp);
+
+    client->optlen = 0;
+    if (!ret) {
+        ret = nbd_negotiate_send_rep_verr(client, type, errp, fmt, va);
+    }
+    return ret;
+}
+
+static int GCC_FMT_ATTR(4, 5)
+nbd_opt_drop(NBDClient *client, uint32_t type, Error **errp,
+             const char *fmt, ...)
+{
+    int ret;
+    va_list va;
+
+    va_start(va, fmt);
+    ret = nbd_opt_vdrop(client, type, errp, fmt, va);
+    va_end(va);
+
+    return ret;
+}
+
+static int GCC_FMT_ATTR(3, 4)
+nbd_opt_invalid(NBDClient *client, Error **errp, const char *fmt, ...)
+{
+    int ret;
+    va_list va;
+
+    va_start(va, fmt);
+    ret = nbd_opt_vdrop(client, NBD_REP_ERR_INVALID, errp, fmt, va);
+    va_end(va);
+
+    return ret;
+}
+
+/* Read size bytes from the unparsed payload of the current option.
+ * If @check_nul, require that no NUL bytes appear in buffer.
+ * Return -errno on I/O error, 0 if option was completely handled by
+ * sending a reply about inconsistent lengths, or 1 on success. */
+static int nbd_opt_read(NBDClient *client, void *buffer, size_t size,
+                        bool check_nul, Error **errp)
+{
+    if (size > client->optlen) {
+        return nbd_opt_invalid(client, errp,
+                               "Inconsistent lengths in option %s",
+                               nbd_opt_lookup(client->opt));
+    }
+    client->optlen -= size;
+    if (qio_channel_read_all(client->ioc, buffer, size, errp) < 0) {
+        return -EIO;
+    }
+
+    if (check_nul && strnlen(buffer, size) != size) {
+        return nbd_opt_invalid(client, errp,
+                               "Unexpected embedded NUL in option %s",
+                               nbd_opt_lookup(client->opt));
+    }
+    return 1;
+}
+
+/* Drop size bytes from the unparsed payload of the current option.
+ * Return -errno on I/O error, 0 if option was completely handled by
+ * sending a reply about inconsistent lengths, or 1 on success. */
+static int nbd_opt_skip(NBDClient *client, size_t size, Error **errp)
+{
+    if (size > client->optlen) {
+        return nbd_opt_invalid(client, errp,
+                               "Inconsistent lengths in option %s",
+                               nbd_opt_lookup(client->opt));
+    }
+    client->optlen -= size;
+    return nbd_drop(client->ioc, size, errp) < 0 ? -EIO : 1;
+}
+
+/* nbd_opt_read_name
+ *
+ * Read a string with the format:
+ *   uint32_t len     (<= NBD_MAX_STRING_SIZE)
+ *   len bytes string (not 0-terminated)
+ *
+ * On success, @name will be allocated.
+ * If @length is non-null, it will be set to the actual string length.
+ *
+ * Return -errno on I/O error, 0 if option was completely handled by
+ * sending a reply about inconsistent lengths, or 1 on success.
+ */
+static int nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length,
+                             Error **errp)
+{
+    int ret;
+    uint32_t len;
+    g_autofree char *local_name = NULL;
+
+    *name = NULL;
+    ret = nbd_opt_read(client, &len, sizeof(len), false, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+    len = cpu_to_be32(len);
+
+    if (len > NBD_MAX_STRING_SIZE) {
+        return nbd_opt_invalid(client, errp,
+                               "Invalid name length: %" PRIu32, len);
+    }
+
+    local_name = g_malloc(len + 1);
+    ret = nbd_opt_read(client, local_name, len, true, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+    local_name[len] = '\0';
+
+    if (length) {
+        *length = len;
+    }
+    *name = g_steal_pointer(&local_name);
+
+    return 1;
+}
+
+/* Send a single NBD_REP_SERVER reply to NBD_OPT_LIST, including payload.
+ * Return -errno on error, 0 on success. */
+static int nbd_negotiate_send_rep_list(NBDClient *client, NBDExport *exp,
+                                       Error **errp)
+{
+    ERRP_GUARD();
+    size_t name_len, desc_len;
+    uint32_t len;
+    const char *name = exp->name ? exp->name : "";
+    const char *desc = exp->description ? exp->description : "";
+    QIOChannel *ioc = client->ioc;
+    int ret;
+
+    trace_nbd_negotiate_send_rep_list(name, desc);
+    name_len = strlen(name);
+    desc_len = strlen(desc);
+    assert(name_len <= NBD_MAX_STRING_SIZE && desc_len <= NBD_MAX_STRING_SIZE);
+    len = name_len + desc_len + sizeof(len);
+    ret = nbd_negotiate_send_rep_len(client, NBD_REP_SERVER, len, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    len = cpu_to_be32(name_len);
+    if (nbd_write(ioc, &len, sizeof(len), errp) < 0) {
+        error_prepend(errp, "write failed (name length): ");
+        return -EINVAL;
+    }
+
+    if (nbd_write(ioc, name, name_len, errp) < 0) {
+        error_prepend(errp, "write failed (name buffer): ");
+        return -EINVAL;
+    }
+
+    if (nbd_write(ioc, desc, desc_len, errp) < 0) {
+        error_prepend(errp, "write failed (description buffer): ");
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+/* Process the NBD_OPT_LIST command, with a potential series of replies.
+ * Return -errno on error, 0 on success. */
+static int nbd_negotiate_handle_list(NBDClient *client, Error **errp)
+{
+    NBDExport *exp;
+    assert(client->opt == NBD_OPT_LIST);
+
+    /* For each export, send a NBD_REP_SERVER reply. */
+    QTAILQ_FOREACH(exp, &exports, next) {
+        if (nbd_negotiate_send_rep_list(client, exp, errp)) {
+            return -EINVAL;
+        }
+    }
+    /* Finish with a NBD_REP_ACK. */
+    return nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
+}
+
+static void nbd_check_meta_export(NBDClient *client)
+{
+    if (client->exp != client->export_meta.exp) {
+        client->export_meta.count = 0;
+    }
+}
+
+/* Send a reply to NBD_OPT_EXPORT_NAME.
+ * Return -errno on error, 0 on success. */
+static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
+                                            Error **errp)
+{
+    ERRP_GUARD();
+    g_autofree char *name = NULL;
+    char buf[NBD_REPLY_EXPORT_NAME_SIZE] = "";
+    size_t len;
+    int ret;
+    uint16_t myflags;
+
+    /* Client sends:
+        [20 ..  xx]   export name (length bytes)
+       Server replies:
+        [ 0 ..   7]   size
+        [ 8 ..   9]   export flags
+        [10 .. 133]   reserved     (0) [unless no_zeroes]
+     */
+    trace_nbd_negotiate_handle_export_name();
+    if (client->optlen > NBD_MAX_STRING_SIZE) {
+        error_setg(errp, "Bad length received");
+        return -EINVAL;
+    }
+    name = g_malloc(client->optlen + 1);
+    if (nbd_read(client->ioc, name, client->optlen, "export name", errp) < 0) {
+        return -EIO;
+    }
+    name[client->optlen] = '\0';
+    client->optlen = 0;
+
+    trace_nbd_negotiate_handle_export_name_request(name);
+
+    client->exp = nbd_export_find(name);
+    if (!client->exp) {
+        error_setg(errp, "export not found");
+        return -EINVAL;
+    }
+
+    myflags = client->exp->nbdflags;
+    if (client->structured_reply) {
+        myflags |= NBD_FLAG_SEND_DF;
+    }
+    trace_nbd_negotiate_new_style_size_flags(client->exp->size, myflags);
+    stq_be_p(buf, client->exp->size);
+    stw_be_p(buf + 8, myflags);
+    len = no_zeroes ? 10 : sizeof(buf);
+    ret = nbd_write(client->ioc, buf, len, errp);
+    if (ret < 0) {
+        error_prepend(errp, "write failed: ");
+        return ret;
+    }
+
+    QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
+    blk_exp_ref(&client->exp->common);
+    nbd_check_meta_export(client);
+
+    return 0;
+}
+
+/* Send a single NBD_REP_INFO, with a buffer @buf of @length bytes.
+ * The buffer does NOT include the info type prefix.
+ * Return -errno on error, 0 if ready to send more. */
+static int nbd_negotiate_send_info(NBDClient *client,
+                                   uint16_t info, uint32_t length, void *buf,
+                                   Error **errp)
+{
+    int rc;
+
+    trace_nbd_negotiate_send_info(info, nbd_info_lookup(info), length);
+    rc = nbd_negotiate_send_rep_len(client, NBD_REP_INFO,
+                                    sizeof(info) + length, errp);
+    if (rc < 0) {
+        return rc;
+    }
+    info = cpu_to_be16(info);
+    if (nbd_write(client->ioc, &info, sizeof(info), errp) < 0) {
+        return -EIO;
+    }
+    if (nbd_write(client->ioc, buf, length, errp) < 0) {
+        return -EIO;
+    }
+    return 0;
+}
+
+/* nbd_reject_length: Handle any unexpected payload.
+ * @fatal requests that we quit talking to the client, even if we are able
+ * to successfully send an error reply.
+ * Return:
+ * -errno  transmission error occurred or @fatal was requested, errp is set
+ * 0       error message successfully sent to client, errp is not set
+ */
+static int nbd_reject_length(NBDClient *client, bool fatal, Error **errp)
+{
+    int ret;
+
+    assert(client->optlen);
+    ret = nbd_opt_invalid(client, errp, "option '%s' has unexpected length",
+                          nbd_opt_lookup(client->opt));
+    if (fatal && !ret) {
+        error_setg(errp, "option '%s' has unexpected length",
+                   nbd_opt_lookup(client->opt));
+        return -EINVAL;
+    }
+    return ret;
+}
+
+/* Handle NBD_OPT_INFO and NBD_OPT_GO.
+ * Return -errno on error, 0 if ready for next option, and 1 to move
+ * into transmission phase.  */
+static int nbd_negotiate_handle_info(NBDClient *client, Error **errp)
+{
+    int rc;
+    g_autofree char *name = NULL;
+    NBDExport *exp;
+    uint16_t requests;
+    uint16_t request;
+    uint32_t namelen = 0;
+    bool sendname = false;
+    bool blocksize = false;
+    uint32_t sizes[3];
+    char buf[sizeof(uint64_t) + sizeof(uint16_t)];
+    uint32_t check_align = 0;
+    uint16_t myflags;
+
+    /* Client sends:
+        4 bytes: L, name length (can be 0)
+        L bytes: export name
+        2 bytes: N, number of requests (can be 0)
+        N * 2 bytes: N requests
+    */
+    rc = nbd_opt_read_name(client, &name, &namelen, errp);
+    if (rc <= 0) {
+        return rc;
+    }
+    trace_nbd_negotiate_handle_export_name_request(name);
+
+    rc = nbd_opt_read(client, &requests, sizeof(requests), false, errp);
+    if (rc <= 0) {
+        return rc;
+    }
+    requests = be16_to_cpu(requests);
+    trace_nbd_negotiate_handle_info_requests(requests);
+    while (requests--) {
+        rc = nbd_opt_read(client, &request, sizeof(request), false, errp);
+        if (rc <= 0) {
+            return rc;
+        }
+        request = be16_to_cpu(request);
+        trace_nbd_negotiate_handle_info_request(request,
+                                                nbd_info_lookup(request));
+        /* We care about NBD_INFO_NAME and NBD_INFO_BLOCK_SIZE;
+         * everything else is either a request we don't know or
+         * something we send regardless of request */
+        switch (request) {
+        case NBD_INFO_NAME:
+            sendname = true;
+            break;
+        case NBD_INFO_BLOCK_SIZE:
+            blocksize = true;
+            break;
+        }
+    }
+    if (client->optlen) {
+        return nbd_reject_length(client, false, errp);
+    }
+
+    exp = nbd_export_find(name);
+    if (!exp) {
+        g_autofree char *sane_name = nbd_sanitize_name(name);
+
+        return nbd_negotiate_send_rep_err(client, NBD_REP_ERR_UNKNOWN,
+                                          errp, "export '%s' not present",
+                                          sane_name);
+    }
+
+    /* Don't bother sending NBD_INFO_NAME unless client requested it */
+    if (sendname) {
+        rc = nbd_negotiate_send_info(client, NBD_INFO_NAME, namelen, name,
+                                     errp);
+        if (rc < 0) {
+            return rc;
+        }
+    }
+
+    /* Send NBD_INFO_DESCRIPTION only if available, regardless of
+     * client request */
+    if (exp->description) {
+        size_t len = strlen(exp->description);
+
+        assert(len <= NBD_MAX_STRING_SIZE);
+        rc = nbd_negotiate_send_info(client, NBD_INFO_DESCRIPTION,
+                                     len, exp->description, errp);
+        if (rc < 0) {
+            return rc;
+        }
+    }
+
+    /* Send NBD_INFO_BLOCK_SIZE always, but tweak the minimum size
+     * according to whether the client requested it, and according to
+     * whether this is OPT_INFO or OPT_GO. */
+    /* minimum - 1 for back-compat, or actual if client will obey it. */
+    if (client->opt == NBD_OPT_INFO || blocksize) {
+        check_align = sizes[0] = blk_get_request_alignment(exp->common.blk);
+    } else {
+        sizes[0] = 1;
+    }
+    assert(sizes[0] <= NBD_MAX_BUFFER_SIZE);
+    /* preferred - Hard-code to 4096 for now.
+     * TODO: is blk_bs(blk)->bl.opt_transfer appropriate? */
+    sizes[1] = MAX(4096, sizes[0]);
+    /* maximum - At most 32M, but smaller as appropriate. */
+    sizes[2] = MIN(blk_get_max_transfer(exp->common.blk), NBD_MAX_BUFFER_SIZE);
+    trace_nbd_negotiate_handle_info_block_size(sizes[0], sizes[1], sizes[2]);
+    sizes[0] = cpu_to_be32(sizes[0]);
+    sizes[1] = cpu_to_be32(sizes[1]);
+    sizes[2] = cpu_to_be32(sizes[2]);
+    rc = nbd_negotiate_send_info(client, NBD_INFO_BLOCK_SIZE,
+                                 sizeof(sizes), sizes, errp);
+    if (rc < 0) {
+        return rc;
+    }
+
+    /* Send NBD_INFO_EXPORT always */
+    myflags = exp->nbdflags;
+    if (client->structured_reply) {
+        myflags |= NBD_FLAG_SEND_DF;
+    }
+    trace_nbd_negotiate_new_style_size_flags(exp->size, myflags);
+    stq_be_p(buf, exp->size);
+    stw_be_p(buf + 8, myflags);
+    rc = nbd_negotiate_send_info(client, NBD_INFO_EXPORT,
+                                 sizeof(buf), buf, errp);
+    if (rc < 0) {
+        return rc;
+    }
+
+    /*
+     * If the client is just asking for NBD_OPT_INFO, but forgot to
+     * request block sizes in a situation that would impact
+     * performance, then return an error. But for NBD_OPT_GO, we
+     * tolerate all clients, regardless of alignments.
+     */
+    if (client->opt == NBD_OPT_INFO && !blocksize &&
+        blk_get_request_alignment(exp->common.blk) > 1) {
+        return nbd_negotiate_send_rep_err(client,
+                                          NBD_REP_ERR_BLOCK_SIZE_REQD,
+                                          errp,
+                                          "request NBD_INFO_BLOCK_SIZE to "
+                                          "use this export");
+    }
+
+    /* Final reply */
+    rc = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
+    if (rc < 0) {
+        return rc;
+    }
+
+    if (client->opt == NBD_OPT_GO) {
+        client->exp = exp;
+        client->check_align = check_align;
+        QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
+        blk_exp_ref(&client->exp->common);
+        nbd_check_meta_export(client);
+        rc = 1;
+    }
+    return rc;
+}
+
+
+/* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the
+ * new channel for all further (now-encrypted) communication. */
+static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
+                                                 Error **errp)
+{
+    QIOChannel *ioc;
+    QIOChannelTLS *tioc;
+    struct NBDTLSHandshakeData data = { 0 };
+
+    assert(client->opt == NBD_OPT_STARTTLS);
+
+    trace_nbd_negotiate_handle_starttls();
+    ioc = client->ioc;
+
+    if (nbd_negotiate_send_rep(client, NBD_REP_ACK, errp) < 0) {
+        return NULL;
+    }
+
+    tioc = qio_channel_tls_new_server(ioc,
+                                      client->tlscreds,
+                                      client->tlsauthz,
+                                      errp);
+    if (!tioc) {
+        return NULL;
+    }
+
+    qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-server-tls");
+    trace_nbd_negotiate_handle_starttls_handshake();
+    data.loop = g_main_loop_new(g_main_context_default(), FALSE);
+    qio_channel_tls_handshake(tioc,
+                              nbd_tls_handshake,
+                              &data,
+                              NULL,
+                              NULL);
+
+    if (!data.complete) {
+        g_main_loop_run(data.loop);
+    }
+    g_main_loop_unref(data.loop);
+    if (data.error) {
+        object_unref(OBJECT(tioc));
+        error_propagate(errp, data.error);
+        return NULL;
+    }
+
+    return QIO_CHANNEL(tioc);
+}
+
+/* nbd_negotiate_send_meta_context
+ *
+ * Send one chunk of reply to NBD_OPT_{LIST,SET}_META_CONTEXT
+ *
+ * For NBD_OPT_LIST_META_CONTEXT @context_id is ignored, 0 is used instead.
+ */
+static int nbd_negotiate_send_meta_context(NBDClient *client,
+                                           const char *context,
+                                           uint32_t context_id,
+                                           Error **errp)
+{
+    NBDOptionReplyMetaContext opt;
+    struct iovec iov[] = {
+        {.iov_base = &opt, .iov_len = sizeof(opt)},
+        {.iov_base = (void *)context, .iov_len = strlen(context)}
+    };
+
+    assert(iov[1].iov_len <= NBD_MAX_STRING_SIZE);
+    if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
+        context_id = 0;
+    }
+
+    trace_nbd_negotiate_meta_query_reply(context, context_id);
+    set_be_option_rep(&opt.h, client->opt, NBD_REP_META_CONTEXT,
+                      sizeof(opt) - sizeof(opt.h) + iov[1].iov_len);
+    stl_be_p(&opt.context_id, context_id);
+
+    return qio_channel_writev_all(client->ioc, iov, 2, errp) < 0 ? -EIO : 0;
+}
+
+/*
+ * Return true if @query matches @pattern, or if @query is empty when
+ * the @client is performing _LIST_.
+ */
+static bool nbd_meta_empty_or_pattern(NBDClient *client, const char *pattern,
+                                      const char *query)
+{
+    if (!*query) {
+        trace_nbd_negotiate_meta_query_parse("empty");
+        return client->opt == NBD_OPT_LIST_META_CONTEXT;
+    }
+    if (strcmp(query, pattern) == 0) {
+        trace_nbd_negotiate_meta_query_parse(pattern);
+        return true;
+    }
+    trace_nbd_negotiate_meta_query_skip("pattern not matched");
+    return false;
+}
+
+/*
+ * Return true and adjust @str in place if it begins with @prefix.
+ */
+static bool nbd_strshift(const char **str, const char *prefix)
+{
+    size_t len = strlen(prefix);
+
+    if (strncmp(*str, prefix, len) == 0) {
+        *str += len;
+        return true;
+    }
+    return false;
+}
+
+/* nbd_meta_base_query
+ *
+ * Handle queries to 'base' namespace. For now, only the base:allocation
+ * context is available.  Return true if @query has been handled.
+ */
+static bool nbd_meta_base_query(NBDClient *client, NBDExportMetaContexts *meta,
+                                const char *query)
+{
+    if (!nbd_strshift(&query, "base:")) {
+        return false;
+    }
+    trace_nbd_negotiate_meta_query_parse("base:");
+
+    if (nbd_meta_empty_or_pattern(client, "allocation", query)) {
+        meta->base_allocation = true;
+    }
+    return true;
+}
+
+/* nbd_meta_qemu_query
+ *
+ * Handle queries to 'qemu' namespace. For now, only the qemu:dirty-bitmap:
+ * and qemu:allocation-depth contexts are available.  Return true if @query
+ * has been handled.
+ */
+static bool nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta,
+                                const char *query)
+{
+    size_t i;
+
+    if (!nbd_strshift(&query, "qemu:")) {
+        return false;
+    }
+    trace_nbd_negotiate_meta_query_parse("qemu:");
+
+    if (!*query) {
+        if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
+            meta->allocation_depth = meta->exp->allocation_depth;
+            if (meta->exp->nr_export_bitmaps) {
+                memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
+            }
+        }
+        trace_nbd_negotiate_meta_query_parse("empty");
+        return true;
+    }
+
+    if (strcmp(query, "allocation-depth") == 0) {
+        trace_nbd_negotiate_meta_query_parse("allocation-depth");
+        meta->allocation_depth = meta->exp->allocation_depth;
+        return true;
+    }
+
+    if (nbd_strshift(&query, "dirty-bitmap:")) {
+        trace_nbd_negotiate_meta_query_parse("dirty-bitmap:");
+        if (!*query) {
+            if (client->opt == NBD_OPT_LIST_META_CONTEXT &&
+                meta->exp->nr_export_bitmaps) {
+                memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
+            }
+            trace_nbd_negotiate_meta_query_parse("empty");
+            return true;
+        }
+
+        for (i = 0; i < meta->exp->nr_export_bitmaps; i++) {
+            const char *bm_name;
+
+            bm_name = bdrv_dirty_bitmap_name(meta->exp->export_bitmaps[i]);
+            if (strcmp(bm_name, query) == 0) {
+                meta->bitmaps[i] = true;
+                trace_nbd_negotiate_meta_query_parse(query);
+                return true;
+            }
+        }
+        trace_nbd_negotiate_meta_query_skip("no dirty-bitmap match");
+        return true;
+    }
+
+    trace_nbd_negotiate_meta_query_skip("unknown qemu context");
+    return true;
+}
+
+/* nbd_negotiate_meta_query
+ *
+ * Parse namespace name and call corresponding function to parse body of the
+ * query.
+ *
+ * The only supported namespaces are 'base' and 'qemu'.
+ *
+ * Return -errno on I/O error, 0 if option was completely handled by
+ * sending a reply about inconsistent lengths, or 1 on success. */
+static int nbd_negotiate_meta_query(NBDClient *client,
+                                    NBDExportMetaContexts *meta, Error **errp)
+{
+    int ret;
+    g_autofree char *query = NULL;
+    uint32_t len;
+
+    ret = nbd_opt_read(client, &len, sizeof(len), false, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+    len = cpu_to_be32(len);
+
+    if (len > NBD_MAX_STRING_SIZE) {
+        trace_nbd_negotiate_meta_query_skip("length too long");
+        return nbd_opt_skip(client, len, errp);
+    }
+
+    query = g_malloc(len + 1);
+    ret = nbd_opt_read(client, query, len, true, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+    query[len] = '\0';
+
+    if (nbd_meta_base_query(client, meta, query)) {
+        return 1;
+    }
+    if (nbd_meta_qemu_query(client, meta, query)) {
+        return 1;
+    }
+
+    trace_nbd_negotiate_meta_query_skip("unknown namespace");
+    return 1;
+}
+
+/* nbd_negotiate_meta_queries
+ * Handle NBD_OPT_LIST_META_CONTEXT and NBD_OPT_SET_META_CONTEXT
+ *
+ * Return -errno on I/O error, or 0 if option was completely handled. */
+static int nbd_negotiate_meta_queries(NBDClient *client,
+                                      NBDExportMetaContexts *meta, Error **errp)
+{
+    int ret;
+    g_autofree char *export_name = NULL;
+    /* Mark unused to work around https://bugs.llvm.org/show_bug.cgi?id=3888 */
+    g_autofree G_GNUC_UNUSED bool *bitmaps = NULL;
+    NBDExportMetaContexts local_meta = {0};
+    uint32_t nb_queries;
+    size_t i;
+    size_t count = 0;
+
+    if (client->opt == NBD_OPT_SET_META_CONTEXT && !client->structured_reply) {
+        return nbd_opt_invalid(client, errp,
+                               "request option '%s' when structured reply "
+                               "is not negotiated",
+                               nbd_opt_lookup(client->opt));
+    }
+
+    if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
+        /* Only change the caller's meta on SET. */
+        meta = &local_meta;
+    }
+
+    g_free(meta->bitmaps);
+    memset(meta, 0, sizeof(*meta));
+
+    ret = nbd_opt_read_name(client, &export_name, NULL, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+
+    meta->exp = nbd_export_find(export_name);
+    if (meta->exp == NULL) {
+        g_autofree char *sane_name = nbd_sanitize_name(export_name);
+
+        return nbd_opt_drop(client, NBD_REP_ERR_UNKNOWN, errp,
+                            "export '%s' not present", sane_name);
+    }
+    meta->bitmaps = g_new0(bool, meta->exp->nr_export_bitmaps);
+    if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
+        bitmaps = meta->bitmaps;
+    }
+
+    ret = nbd_opt_read(client, &nb_queries, sizeof(nb_queries), false, errp);
+    if (ret <= 0) {
+        return ret;
+    }
+    nb_queries = cpu_to_be32(nb_queries);
+    trace_nbd_negotiate_meta_context(nbd_opt_lookup(client->opt),
+                                     export_name, nb_queries);
+
+    if (client->opt == NBD_OPT_LIST_META_CONTEXT && !nb_queries) {
+        /* enable all known contexts */
+        meta->base_allocation = true;
+        meta->allocation_depth = meta->exp->allocation_depth;
+        if (meta->exp->nr_export_bitmaps) {
+            memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
+        }
+    } else {
+        for (i = 0; i < nb_queries; ++i) {
+            ret = nbd_negotiate_meta_query(client, meta, errp);
+            if (ret <= 0) {
+                return ret;
+            }
+        }
+    }
+
+    if (meta->base_allocation) {
+        ret = nbd_negotiate_send_meta_context(client, "base:allocation",
+                                              NBD_META_ID_BASE_ALLOCATION,
+                                              errp);
+        if (ret < 0) {
+            return ret;
+        }
+        count++;
+    }
+
+    if (meta->allocation_depth) {
+        ret = nbd_negotiate_send_meta_context(client, "qemu:allocation-depth",
+                                              NBD_META_ID_ALLOCATION_DEPTH,
+                                              errp);
+        if (ret < 0) {
+            return ret;
+        }
+        count++;
+    }
+
+    for (i = 0; i < meta->exp->nr_export_bitmaps; i++) {
+        const char *bm_name;
+        g_autofree char *context = NULL;
+
+        if (!meta->bitmaps[i]) {
+            continue;
+        }
+
+        bm_name = bdrv_dirty_bitmap_name(meta->exp->export_bitmaps[i]);
+        context = g_strdup_printf("qemu:dirty-bitmap:%s", bm_name);
+
+        ret = nbd_negotiate_send_meta_context(client, context,
+                                              NBD_META_ID_DIRTY_BITMAP + i,
+                                              errp);
+        if (ret < 0) {
+            return ret;
+        }
+        count++;
+    }
+
+    ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
+    if (ret == 0) {
+        meta->count = count;
+    }
+
+    return ret;
+}
+
+/* nbd_negotiate_options
+ * Process all NBD_OPT_* client option commands, during fixed newstyle
+ * negotiation.
+ * Return:
+ * -errno  on error, errp is set
+ * 0       on successful negotiation, errp is not set
+ * 1       if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
+ *         errp is not set
+ */
+static int nbd_negotiate_options(NBDClient *client, Error **errp)
+{
+    uint32_t flags;
+    bool fixedNewstyle = false;
+    bool no_zeroes = false;
+
+    /* Client sends:
+        [ 0 ..   3]   client flags
+
+       Then we loop until NBD_OPT_EXPORT_NAME or NBD_OPT_GO:
+        [ 0 ..   7]   NBD_OPTS_MAGIC
+        [ 8 ..  11]   NBD option
+        [12 ..  15]   Data length
+        ...           Rest of request
+
+        [ 0 ..   7]   NBD_OPTS_MAGIC
+        [ 8 ..  11]   Second NBD option
+        [12 ..  15]   Data length
+        ...           Rest of request
+    */
+
+    if (nbd_read32(client->ioc, &flags, "flags", errp) < 0) {
+        return -EIO;
+    }
+    trace_nbd_negotiate_options_flags(flags);
+    if (flags & NBD_FLAG_C_FIXED_NEWSTYLE) {
+        fixedNewstyle = true;
+        flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE;
+    }
+    if (flags & NBD_FLAG_C_NO_ZEROES) {
+        no_zeroes = true;
+        flags &= ~NBD_FLAG_C_NO_ZEROES;
+    }
+    if (flags != 0) {
+        error_setg(errp, "Unknown client flags 0x%" PRIx32 " received", flags);
+        return -EINVAL;
+    }
+
+    while (1) {
+        int ret;
+        uint32_t option, length;
+        uint64_t magic;
+
+        if (nbd_read64(client->ioc, &magic, "opts magic", errp) < 0) {
+            return -EINVAL;
+        }
+        trace_nbd_negotiate_options_check_magic(magic);
+        if (magic != NBD_OPTS_MAGIC) {
+            error_setg(errp, "Bad magic received");
+            return -EINVAL;
+        }
+
+        if (nbd_read32(client->ioc, &option, "option", errp) < 0) {
+            return -EINVAL;
+        }
+        client->opt = option;
+
+        if (nbd_read32(client->ioc, &length, "option length", errp) < 0) {
+            return -EINVAL;
+        }
+        assert(!client->optlen);
+        client->optlen = length;
+
+        if (length > NBD_MAX_BUFFER_SIZE) {
+            error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",
+                       length, NBD_MAX_BUFFER_SIZE);
+            return -EINVAL;
+        }
+
+        trace_nbd_negotiate_options_check_option(option,
+                                                 nbd_opt_lookup(option));
+        if (client->tlscreds &&
+            client->ioc == (QIOChannel *)client->sioc) {
+            QIOChannel *tioc;
+            if (!fixedNewstyle) {
+                error_setg(errp, "Unsupported option 0x%" PRIx32, option);
+                return -EINVAL;
+            }
+            switch (option) {
+            case NBD_OPT_STARTTLS:
+                if (length) {
+                    /* Unconditionally drop the connection if the client
+                     * can't start a TLS negotiation correctly */
+                    return nbd_reject_length(client, true, errp);
+                }
+                tioc = nbd_negotiate_handle_starttls(client, errp);
+                if (!tioc) {
+                    return -EIO;
+                }
+                ret = 0;
+                object_unref(OBJECT(client->ioc));
+                client->ioc = QIO_CHANNEL(tioc);
+                break;
+
+            case NBD_OPT_EXPORT_NAME:
+                /* No way to return an error to client, so drop connection */
+                error_setg(errp, "Option 0x%x not permitted before TLS",
+                           option);
+                return -EINVAL;
+
+            default:
+                /* Let the client keep trying, unless they asked to
+                 * quit. Always try to give an error back to the
+                 * client; but when replying to OPT_ABORT, be aware
+                 * that the client may hang up before receiving the
+                 * error, in which case we are fine ignoring the
+                 * resulting EPIPE. */
+                ret = nbd_opt_drop(client, NBD_REP_ERR_TLS_REQD,
+                                   option == NBD_OPT_ABORT ? NULL : errp,
+                                   "Option 0x%" PRIx32
+                                   " not permitted before TLS", option);
+                if (option == NBD_OPT_ABORT) {
+                    return 1;
+                }
+                break;
+            }
+        } else if (fixedNewstyle) {
+            switch (option) {
+            case NBD_OPT_LIST:
+                if (length) {
+                    ret = nbd_reject_length(client, false, errp);
+                } else {
+                    ret = nbd_negotiate_handle_list(client, errp);
+                }
+                break;
+
+            case NBD_OPT_ABORT:
+                /* NBD spec says we must try to reply before
+                 * disconnecting, but that we must also tolerate
+                 * guests that don't wait for our reply. */
+                nbd_negotiate_send_rep(client, NBD_REP_ACK, NULL);
+                return 1;
+
+            case NBD_OPT_EXPORT_NAME:
+                return nbd_negotiate_handle_export_name(client, no_zeroes,
+                                                        errp);
+
+            case NBD_OPT_INFO:
+            case NBD_OPT_GO:
+                ret = nbd_negotiate_handle_info(client, errp);
+                if (ret == 1) {
+                    assert(option == NBD_OPT_GO);
+                    return 0;
+                }
+                break;
+
+            case NBD_OPT_STARTTLS:
+                if (length) {
+                    ret = nbd_reject_length(client, false, errp);
+                } else if (client->tlscreds) {
+                    ret = nbd_negotiate_send_rep_err(client,
+                                                     NBD_REP_ERR_INVALID, errp,
+                                                     "TLS already enabled");
+                } else {
+                    ret = nbd_negotiate_send_rep_err(client,
+                                                     NBD_REP_ERR_POLICY, errp,
+                                                     "TLS not configured");
+                }
+                break;
+
+            case NBD_OPT_STRUCTURED_REPLY:
+                if (length) {
+                    ret = nbd_reject_length(client, false, errp);
+                } else if (client->structured_reply) {
+                    ret = nbd_negotiate_send_rep_err(
+                        client, NBD_REP_ERR_INVALID, errp,
+                        "structured reply already negotiated");
+                } else {
+                    ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
+                    client->structured_reply = true;
+                }
+                break;
+
+            case NBD_OPT_LIST_META_CONTEXT:
+            case NBD_OPT_SET_META_CONTEXT:
+                ret = nbd_negotiate_meta_queries(client, &client->export_meta,
+                                                 errp);
+                break;
+
+            default:
+                ret = nbd_opt_drop(client, NBD_REP_ERR_UNSUP, errp,
+                                   "Unsupported option %" PRIu32 " (%s)",
+                                   option, nbd_opt_lookup(option));
+                break;
+            }
+        } else {
+            /*
+             * If broken new-style we should drop the connection
+             * for anything except NBD_OPT_EXPORT_NAME
+             */
+            switch (option) {
+            case NBD_OPT_EXPORT_NAME:
+                return nbd_negotiate_handle_export_name(client, no_zeroes,
+                                                        errp);
+
+            default:
+                error_setg(errp, "Unsupported option %" PRIu32 " (%s)",
+                           option, nbd_opt_lookup(option));
+                return -EINVAL;
+            }
+        }
+        if (ret < 0) {
+            return ret;
+        }
+    }
+}
+
+/* nbd_negotiate
+ * Return:
+ * -errno  on error, errp is set
+ * 0       on successful negotiation, errp is not set
+ * 1       if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
+ *         errp is not set
+ */
+static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
+{
+    ERRP_GUARD();
+    char buf[NBD_OLDSTYLE_NEGOTIATE_SIZE] = "";
+    int ret;
+
+    /* Old style negotiation header, no room for options
+        [ 0 ..   7]   passwd       ("NBDMAGIC")
+        [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
+        [16 ..  23]   size
+        [24 ..  27]   export flags (zero-extended)
+        [28 .. 151]   reserved     (0)
+
+       New style negotiation header, client can send options
+        [ 0 ..   7]   passwd       ("NBDMAGIC")
+        [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
+        [16 ..  17]   server flags (0)
+        ....options sent, ending in NBD_OPT_EXPORT_NAME or NBD_OPT_GO....
+     */
+
+    qio_channel_set_blocking(client->ioc, false, NULL);
+
+    trace_nbd_negotiate_begin();
+    memcpy(buf, "NBDMAGIC", 8);
+
+    stq_be_p(buf + 8, NBD_OPTS_MAGIC);
+    stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES);
+
+    if (nbd_write(client->ioc, buf, 18, errp) < 0) {
+        error_prepend(errp, "write failed: ");
+        return -EINVAL;
+    }
+    ret = nbd_negotiate_options(client, errp);
+    if (ret != 0) {
+        if (ret < 0) {
+            error_prepend(errp, "option negotiation failed: ");
+        }
+        return ret;
+    }
+
+    /* Attach the channel to the same AioContext as the export */
+    if (client->exp && client->exp->common.ctx) {
+        qio_channel_attach_aio_context(client->ioc, client->exp->common.ctx);
+    }
+
+    assert(!client->optlen);
+    trace_nbd_negotiate_success();
+
+    return 0;
+}
+
+/* nbd_read_eof
+ * Tries to read @size bytes from @ioc. This is a local implementation of
+ * qio_channel_readv_all_eof. We have it here because we need it to be
+ * interruptible and to know when the coroutine is yielding.
+ * Returns 1 on success
+ *         0 on eof, when no data was read (errp is not set)
+ *         negative errno on failure (errp is set)
+ */
+static inline int coroutine_fn
+nbd_read_eof(NBDClient *client, void *buffer, size_t size, Error **errp)
+{
+    bool partial = false;
+
+    assert(size);
+    while (size > 0) {
+        struct iovec iov = { .iov_base = buffer, .iov_len = size };
+        ssize_t len;
+
+        len = qio_channel_readv(client->ioc, &iov, 1, errp);
+        if (len == QIO_CHANNEL_ERR_BLOCK) {
+            client->read_yielding = true;
+            qio_channel_yield(client->ioc, G_IO_IN);
+            client->read_yielding = false;
+            if (client->quiescing) {
+                return -EAGAIN;
+            }
+            continue;
+        } else if (len < 0) {
+            return -EIO;
+        } else if (len == 0) {
+            if (partial) {
+                error_setg(errp,
+                           "Unexpected end-of-file before all bytes were read");
+                return -EIO;
+            } else {
+                return 0;
+            }
+        }
+
+        partial = true;
+        size -= len;
+        buffer = (uint8_t *) buffer + len;
+    }
+    return 1;
+}
+
+static int nbd_receive_request(NBDClient *client, NBDRequest *request,
+                               Error **errp)
+{
+    uint8_t buf[NBD_REQUEST_SIZE];
+    uint32_t magic;
+    int ret;
+
+    ret = nbd_read_eof(client, buf, sizeof(buf), errp);
+    if (ret < 0) {
+        return ret;
+    }
+    if (ret == 0) {
+        return -EIO;
+    }
+
+    /* Request
+       [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
+       [ 4 ..  5]   flags   (NBD_CMD_FLAG_FUA, ...)
+       [ 6 ..  7]   type    (NBD_CMD_READ, ...)
+       [ 8 .. 15]   handle
+       [16 .. 23]   from
+       [24 .. 27]   len
+     */
+
+    magic = ldl_be_p(buf);
+    request->flags  = lduw_be_p(buf + 4);
+    request->type   = lduw_be_p(buf + 6);
+    request->handle = ldq_be_p(buf + 8);
+    request->from   = ldq_be_p(buf + 16);
+    request->len    = ldl_be_p(buf + 24);
+
+    trace_nbd_receive_request(magic, request->flags, request->type,
+                              request->from, request->len);
+
+    if (magic != NBD_REQUEST_MAGIC) {
+        error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
+        return -EINVAL;
+    }
+    return 0;
+}
+
+#define MAX_NBD_REQUESTS 16
+
+void nbd_client_get(NBDClient *client)
+{
+    client->refcount++;
+}
+
+void nbd_client_put(NBDClient *client)
+{
+    if (--client->refcount == 0) {
+        /* The last reference should be dropped by client->close,
+         * which is called by client_close.
+         */
+        assert(client->closing);
+
+        qio_channel_detach_aio_context(client->ioc);
+        object_unref(OBJECT(client->sioc));
+        object_unref(OBJECT(client->ioc));
+        if (client->tlscreds) {
+            object_unref(OBJECT(client->tlscreds));
+        }
+        g_free(client->tlsauthz);
+        if (client->exp) {
+            QTAILQ_REMOVE(&client->exp->clients, client, next);
+            blk_exp_unref(&client->exp->common);
+        }
+        g_free(client->export_meta.bitmaps);
+        g_free(client);
+    }
+}
+
+static void client_close(NBDClient *client, bool negotiated)
+{
+    if (client->closing) {
+        return;
+    }
+
+    client->closing = true;
+
+    /* Force requests to finish.  They will drop their own references,
+     * then we'll close the socket and free the NBDClient.
+     */
+    qio_channel_shutdown(client->ioc, QIO_CHANNEL_SHUTDOWN_BOTH,
+                         NULL);
+
+    /* Also tell the client, so that they release their reference.  */
+    if (client->close_fn) {
+        client->close_fn(client, negotiated);
+    }
+}
+
+static NBDRequestData *nbd_request_get(NBDClient *client)
+{
+    NBDRequestData *req;
+
+    assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
+    client->nb_requests++;
+
+    req = g_new0(NBDRequestData, 1);
+    nbd_client_get(client);
+    req->client = client;
+    return req;
+}
+
+static void nbd_request_put(NBDRequestData *req)
+{
+    NBDClient *client = req->client;
+
+    if (req->data) {
+        qemu_vfree(req->data);
+    }
+    g_free(req);
+
+    client->nb_requests--;
+
+    if (client->quiescing && client->nb_requests == 0) {
+        aio_wait_kick();
+    }
+
+    nbd_client_receive_next_request(client);
+
+    nbd_client_put(client);
+}
+
+static void blk_aio_attached(AioContext *ctx, void *opaque)
+{
+    NBDExport *exp = opaque;
+    NBDClient *client;
+
+    trace_nbd_blk_aio_attached(exp->name, ctx);
+
+    exp->common.ctx = ctx;
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        qio_channel_attach_aio_context(client->ioc, ctx);
+
+        assert(client->nb_requests == 0);
+        assert(client->recv_coroutine == NULL);
+        assert(client->send_coroutine == NULL);
+    }
+}
+
+static void blk_aio_detach(void *opaque)
+{
+    NBDExport *exp = opaque;
+    NBDClient *client;
+
+    trace_nbd_blk_aio_detach(exp->name, exp->common.ctx);
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        qio_channel_detach_aio_context(client->ioc);
+    }
+
+    exp->common.ctx = NULL;
+}
+
+static void nbd_drained_begin(void *opaque)
+{
+    NBDExport *exp = opaque;
+    NBDClient *client;
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        client->quiescing = true;
+    }
+}
+
+static void nbd_drained_end(void *opaque)
+{
+    NBDExport *exp = opaque;
+    NBDClient *client;
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        client->quiescing = false;
+        nbd_client_receive_next_request(client);
+    }
+}
+
+static bool nbd_drained_poll(void *opaque)
+{
+    NBDExport *exp = opaque;
+    NBDClient *client;
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        if (client->nb_requests != 0) {
+            /*
+             * If there's a coroutine waiting for a request on nbd_read_eof()
+             * enter it here so we don't depend on the client to wake it up.
+             */
+            if (client->recv_coroutine != NULL && client->read_yielding) {
+                qemu_aio_coroutine_enter(exp->common.ctx,
+                                         client->recv_coroutine);
+            }
+
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static void nbd_eject_notifier(Notifier *n, void *data)
+{
+    NBDExport *exp = container_of(n, NBDExport, eject_notifier);
+
+    blk_exp_request_shutdown(&exp->common);
+}
+
+void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk)
+{
+    NBDExport *nbd_exp = container_of(exp, NBDExport, common);
+    assert(exp->drv == &blk_exp_nbd);
+    assert(nbd_exp->eject_notifier_blk == NULL);
+
+    blk_ref(blk);
+    nbd_exp->eject_notifier_blk = blk;
+    nbd_exp->eject_notifier.notify = nbd_eject_notifier;
+    blk_add_remove_bs_notifier(blk, &nbd_exp->eject_notifier);
+}
+
+static const BlockDevOps nbd_block_ops = {
+    .drained_begin = nbd_drained_begin,
+    .drained_end = nbd_drained_end,
+    .drained_poll = nbd_drained_poll,
+};
+
+static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
+                             Error **errp)
+{
+    NBDExport *exp = container_of(blk_exp, NBDExport, common);
+    BlockExportOptionsNbd *arg = &exp_args->u.nbd;
+    BlockBackend *blk = blk_exp->blk;
+    int64_t size;
+    uint64_t perm, shared_perm;
+    bool readonly = !exp_args->writable;
+    bool shared = !exp_args->writable;
+    strList *bitmaps;
+    size_t i;
+    int ret;
+
+    assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD);
+
+    if (!nbd_server_is_running()) {
+        error_setg(errp, "NBD server not running");
+        return -EINVAL;
+    }
+
+    if (!arg->has_name) {
+        arg->name = exp_args->node_name;
+    }
+
+    if (strlen(arg->name) > NBD_MAX_STRING_SIZE) {
+        error_setg(errp, "export name '%s' too long", arg->name);
+        return -EINVAL;
+    }
+
+    if (arg->description && strlen(arg->description) > NBD_MAX_STRING_SIZE) {
+        error_setg(errp, "description '%s' too long", arg->description);
+        return -EINVAL;
+    }
+
+    if (nbd_export_find(arg->name)) {
+        error_setg(errp, "NBD server already has export named '%s'", arg->name);
+        return -EEXIST;
+    }
+
+    size = blk_getlength(blk);
+    if (size < 0) {
+        error_setg_errno(errp, -size,
+                         "Failed to determine the NBD export's length");
+        return size;
+    }
+
+    /* Don't allow resize while the NBD server is running, otherwise we don't
+     * care what happens with the node. */
+    blk_get_perm(blk, &perm, &shared_perm);
+    ret = blk_set_perm(blk, perm, shared_perm & ~BLK_PERM_RESIZE, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    QTAILQ_INIT(&exp->clients);
+    exp->name = g_strdup(arg->name);
+    exp->description = g_strdup(arg->description);
+    exp->nbdflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH |
+                     NBD_FLAG_SEND_FUA | NBD_FLAG_SEND_CACHE);
+    if (readonly) {
+        exp->nbdflags |= NBD_FLAG_READ_ONLY;
+        if (shared) {
+            exp->nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
+        }
+    } else {
+        exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES |
+                          NBD_FLAG_SEND_FAST_ZERO);
+    }
+    exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE);
+
+    for (bitmaps = arg->bitmaps; bitmaps; bitmaps = bitmaps->next) {
+        exp->nr_export_bitmaps++;
+    }
+    exp->export_bitmaps = g_new0(BdrvDirtyBitmap *, exp->nr_export_bitmaps);
+    for (i = 0, bitmaps = arg->bitmaps; bitmaps;
+         i++, bitmaps = bitmaps->next) {
+        const char *bitmap = bitmaps->value;
+        BlockDriverState *bs = blk_bs(blk);
+        BdrvDirtyBitmap *bm = NULL;
+
+        while (bs) {
+            bm = bdrv_find_dirty_bitmap(bs, bitmap);
+            if (bm != NULL) {
+                break;
+            }
+
+            bs = bdrv_filter_or_cow_bs(bs);
+        }
+
+        if (bm == NULL) {
+            ret = -ENOENT;
+            error_setg(errp, "Bitmap '%s' is not found", bitmap);
+            goto fail;
+        }
+
+        if (bdrv_dirty_bitmap_check(bm, BDRV_BITMAP_ALLOW_RO, errp)) {
+            ret = -EINVAL;
+            goto fail;
+        }
+
+        if (readonly && bdrv_is_writable(bs) &&
+            bdrv_dirty_bitmap_enabled(bm)) {
+            ret = -EINVAL;
+            error_setg(errp,
+                       "Enabled bitmap '%s' incompatible with readonly export",
+                       bitmap);
+            goto fail;
+        }
+
+        exp->export_bitmaps[i] = bm;
+        assert(strlen(bitmap) <= BDRV_BITMAP_MAX_NAME_SIZE);
+    }
+
+    /* Mark bitmaps busy in a separate loop, to simplify roll-back concerns. */
+    for (i = 0; i < exp->nr_export_bitmaps; i++) {
+        bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], true);
+    }
+
+    exp->allocation_depth = arg->allocation_depth;
+
+    /*
+     * We need to inhibit request queuing in the block layer to ensure we can
+     * be properly quiesced when entering a drained section, as our coroutines
+     * servicing pending requests might enter blk_pread().
+     */
+    blk_set_disable_request_queuing(blk, true);
+
+    blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
+
+    blk_set_dev_ops(blk, &nbd_block_ops, exp);
+
+    QTAILQ_INSERT_TAIL(&exports, exp, next);
+
+    return 0;
+
+fail:
+    g_free(exp->export_bitmaps);
+    g_free(exp->name);
+    g_free(exp->description);
+    return ret;
+}
+
+NBDExport *nbd_export_find(const char *name)
+{
+    NBDExport *exp;
+    QTAILQ_FOREACH(exp, &exports, next) {
+        if (strcmp(name, exp->name) == 0) {
+            return exp;
+        }
+    }
+
+    return NULL;
+}
+
+AioContext *
+nbd_export_aio_context(NBDExport *exp)
+{
+    return exp->common.ctx;
+}
+
+static void nbd_export_request_shutdown(BlockExport *blk_exp)
+{
+    NBDExport *exp = container_of(blk_exp, NBDExport, common);
+    NBDClient *client, *next;
+
+    blk_exp_ref(&exp->common);
+    /*
+     * TODO: Should we expand QMP NbdServerRemoveNode enum to allow a
+     * close mode that stops advertising the export to new clients but
+     * still permits existing clients to run to completion? Because of
+     * that possibility, nbd_export_close() can be called more than
+     * once on an export.
+     */
+    QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
+        client_close(client, true);
+    }
+    if (exp->name) {
+        g_free(exp->name);
+        exp->name = NULL;
+        QTAILQ_REMOVE(&exports, exp, next);
+    }
+    blk_exp_unref(&exp->common);
+}
+
+static void nbd_export_delete(BlockExport *blk_exp)
+{
+    size_t i;
+    NBDExport *exp = container_of(blk_exp, NBDExport, common);
+
+    assert(exp->name == NULL);
+    assert(QTAILQ_EMPTY(&exp->clients));
+
+    g_free(exp->description);
+    exp->description = NULL;
+
+    if (exp->common.blk) {
+        if (exp->eject_notifier_blk) {
+            notifier_remove(&exp->eject_notifier);
+            blk_unref(exp->eject_notifier_blk);
+        }
+        blk_remove_aio_context_notifier(exp->common.blk, blk_aio_attached,
+                                        blk_aio_detach, exp);
+        blk_set_disable_request_queuing(exp->common.blk, false);
+    }
+
+    for (i = 0; i < exp->nr_export_bitmaps; i++) {
+        bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], false);
+    }
+}
+
+const BlockExportDriver blk_exp_nbd = {
+    .type               = BLOCK_EXPORT_TYPE_NBD,
+    .instance_size      = sizeof(NBDExport),
+    .create             = nbd_export_create,
+    .delete             = nbd_export_delete,
+    .request_shutdown   = nbd_export_request_shutdown,
+};
+
+static int coroutine_fn nbd_co_send_iov(NBDClient *client, struct iovec *iov,
+                                        unsigned niov, Error **errp)
+{
+    int ret;
+
+    g_assert(qemu_in_coroutine());
+    qemu_co_mutex_lock(&client->send_lock);
+    client->send_coroutine = qemu_coroutine_self();
+
+    ret = qio_channel_writev_all(client->ioc, iov, niov, errp) < 0 ? -EIO : 0;
+
+    client->send_coroutine = NULL;
+    qemu_co_mutex_unlock(&client->send_lock);
+
+    return ret;
+}
+
+static inline void set_be_simple_reply(NBDSimpleReply *reply, uint64_t error,
+                                       uint64_t handle)
+{
+    stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC);
+    stl_be_p(&reply->error, error);
+    stq_be_p(&reply->handle, handle);
+}
+
+static int nbd_co_send_simple_reply(NBDClient *client,
+                                    uint64_t handle,
+                                    uint32_t error,
+                                    void *data,
+                                    size_t len,
+                                    Error **errp)
+{
+    NBDSimpleReply reply;
+    int nbd_err = system_errno_to_nbd_errno(error);
+    struct iovec iov[] = {
+        {.iov_base = &reply, .iov_len = sizeof(reply)},
+        {.iov_base = data, .iov_len = len}
+    };
+
+    trace_nbd_co_send_simple_reply(handle, nbd_err, nbd_err_lookup(nbd_err),
+                                   len);
+    set_be_simple_reply(&reply, nbd_err, handle);
+
+    return nbd_co_send_iov(client, iov, len ? 2 : 1, errp);
+}
+
+static inline void set_be_chunk(NBDStructuredReplyChunk *chunk, uint16_t flags,
+                                uint16_t type, uint64_t handle, uint32_t length)
+{
+    stl_be_p(&chunk->magic, NBD_STRUCTURED_REPLY_MAGIC);
+    stw_be_p(&chunk->flags, flags);
+    stw_be_p(&chunk->type, type);
+    stq_be_p(&chunk->handle, handle);
+    stl_be_p(&chunk->length, length);
+}
+
+static int coroutine_fn nbd_co_send_structured_done(NBDClient *client,
+                                                    uint64_t handle,
+                                                    Error **errp)
+{
+    NBDStructuredReplyChunk chunk;
+    struct iovec iov[] = {
+        {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+    };
+
+    trace_nbd_co_send_structured_done(handle);
+    set_be_chunk(&chunk, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_NONE, handle, 0);
+
+    return nbd_co_send_iov(client, iov, 1, errp);
+}
+
+static int coroutine_fn nbd_co_send_structured_read(NBDClient *client,
+                                                    uint64_t handle,
+                                                    uint64_t offset,
+                                                    void *data,
+                                                    size_t size,
+                                                    bool final,
+                                                    Error **errp)
+{
+    NBDStructuredReadData chunk;
+    struct iovec iov[] = {
+        {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+        {.iov_base = data, .iov_len = size}
+    };
+
+    assert(size);
+    trace_nbd_co_send_structured_read(handle, offset, data, size);
+    set_be_chunk(&chunk.h, final ? NBD_REPLY_FLAG_DONE : 0,
+                 NBD_REPLY_TYPE_OFFSET_DATA, handle,
+                 sizeof(chunk) - sizeof(chunk.h) + size);
+    stq_be_p(&chunk.offset, offset);
+
+    return nbd_co_send_iov(client, iov, 2, errp);
+}
+
+static int coroutine_fn nbd_co_send_structured_error(NBDClient *client,
+                                                     uint64_t handle,
+                                                     uint32_t error,
+                                                     const char *msg,
+                                                     Error **errp)
+{
+    NBDStructuredError chunk;
+    int nbd_err = system_errno_to_nbd_errno(error);
+    struct iovec iov[] = {
+        {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+        {.iov_base = (char *)msg, .iov_len = msg ? strlen(msg) : 0},
+    };
+
+    assert(nbd_err);
+    trace_nbd_co_send_structured_error(handle, nbd_err,
+                                       nbd_err_lookup(nbd_err), msg ? msg : "");
+    set_be_chunk(&chunk.h, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_ERROR, handle,
+                 sizeof(chunk) - sizeof(chunk.h) + iov[1].iov_len);
+    stl_be_p(&chunk.error, nbd_err);
+    stw_be_p(&chunk.message_length, iov[1].iov_len);
+
+    return nbd_co_send_iov(client, iov, 1 + !!iov[1].iov_len, errp);
+}
+
+/* Do a sparse read and send the structured reply to the client.
+ * Returns -errno if sending fails. bdrv_block_status_above() failure is
+ * reported to the client, at which point this function succeeds.
+ */
+static int coroutine_fn nbd_co_send_sparse_read(NBDClient *client,
+                                                uint64_t handle,
+                                                uint64_t offset,
+                                                uint8_t *data,
+                                                size_t size,
+                                                Error **errp)
+{
+    int ret = 0;
+    NBDExport *exp = client->exp;
+    size_t progress = 0;
+
+    while (progress < size) {
+        int64_t pnum;
+        int status = bdrv_block_status_above(blk_bs(exp->common.blk), NULL,
+                                             offset + progress,
+                                             size - progress, &pnum, NULL,
+                                             NULL);
+        bool final;
+
+        if (status < 0) {
+            char *msg = g_strdup_printf("unable to check for holes: %s",
+                                        strerror(-status));
+
+            ret = nbd_co_send_structured_error(client, handle, -status, msg,
+                                               errp);
+            g_free(msg);
+            return ret;
+        }
+        assert(pnum && pnum <= size - progress);
+        final = progress + pnum == size;
+        if (status & BDRV_BLOCK_ZERO) {
+            NBDStructuredReadHole chunk;
+            struct iovec iov[] = {
+                {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+            };
+
+            trace_nbd_co_send_structured_read_hole(handle, offset + progress,
+                                                   pnum);
+            set_be_chunk(&chunk.h, final ? NBD_REPLY_FLAG_DONE : 0,
+                         NBD_REPLY_TYPE_OFFSET_HOLE,
+                         handle, sizeof(chunk) - sizeof(chunk.h));
+            stq_be_p(&chunk.offset, offset + progress);
+            stl_be_p(&chunk.length, pnum);
+            ret = nbd_co_send_iov(client, iov, 1, errp);
+        } else {
+            ret = blk_pread(exp->common.blk, offset + progress,
+                            data + progress, pnum);
+            if (ret < 0) {
+                error_setg_errno(errp, -ret, "reading from file failed");
+                break;
+            }
+            ret = nbd_co_send_structured_read(client, handle, offset + progress,
+                                              data + progress, pnum, final,
+                                              errp);
+        }
+
+        if (ret < 0) {
+            break;
+        }
+        progress += pnum;
+    }
+    return ret;
+}
+
+typedef struct NBDExtentArray {
+    NBDExtent *extents;
+    unsigned int nb_alloc;
+    unsigned int count;
+    uint64_t total_length;
+    bool can_add;
+    bool converted_to_be;
+} NBDExtentArray;
+
+static NBDExtentArray *nbd_extent_array_new(unsigned int nb_alloc)
+{
+    NBDExtentArray *ea = g_new0(NBDExtentArray, 1);
+
+    ea->nb_alloc = nb_alloc;
+    ea->extents = g_new(NBDExtent, nb_alloc);
+    ea->can_add = true;
+
+    return ea;
+}
+
+static void nbd_extent_array_free(NBDExtentArray *ea)
+{
+    g_free(ea->extents);
+    g_free(ea);
+}
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(NBDExtentArray, nbd_extent_array_free);
+
+/* Further modifications of the array after conversion are abandoned */
+static void nbd_extent_array_convert_to_be(NBDExtentArray *ea)
+{
+    int i;
+
+    assert(!ea->converted_to_be);
+    ea->can_add = false;
+    ea->converted_to_be = true;
+
+    for (i = 0; i < ea->count; i++) {
+        ea->extents[i].flags = cpu_to_be32(ea->extents[i].flags);
+        ea->extents[i].length = cpu_to_be32(ea->extents[i].length);
+    }
+}
+
+/*
+ * Add extent to NBDExtentArray. If extent can't be added (no available space),
+ * return -1.
+ * For safety, when returning -1 for the first time, .can_add is set to false,
+ * further call to nbd_extent_array_add() will crash.
+ * (to avoid the situation, when after failing to add an extent (returned -1),
+ * user miss this failure and add another extent, which is successfully added
+ * (array is full, but new extent may be squashed into the last one), then we
+ * have invalid array with skipped extent)
+ */
+static int nbd_extent_array_add(NBDExtentArray *ea,
+                                uint32_t length, uint32_t flags)
+{
+    assert(ea->can_add);
+
+    if (!length) {
+        return 0;
+    }
+
+    /* Extend previous extent if flags are the same */
+    if (ea->count > 0 && flags == ea->extents[ea->count - 1].flags) {
+        uint64_t sum = (uint64_t)length + ea->extents[ea->count - 1].length;
+
+        if (sum <= UINT32_MAX) {
+            ea->extents[ea->count - 1].length = sum;
+            ea->total_length += length;
+            return 0;
+        }
+    }
+
+    if (ea->count >= ea->nb_alloc) {
+        ea->can_add = false;
+        return -1;
+    }
+
+    ea->total_length += length;
+    ea->extents[ea->count] = (NBDExtent) {.length = length, .flags = flags};
+    ea->count++;
+
+    return 0;
+}
+
+static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
+                                  uint64_t bytes, NBDExtentArray *ea)
+{
+    while (bytes) {
+        uint32_t flags;
+        int64_t num;
+        int ret = bdrv_block_status_above(bs, NULL, offset, bytes, &num,
+                                          NULL, NULL);
+
+        if (ret < 0) {
+            return ret;
+        }
+
+        flags = (ret & BDRV_BLOCK_DATA ? 0 : NBD_STATE_HOLE) |
+                (ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0);
+
+        if (nbd_extent_array_add(ea, num, flags) < 0) {
+            return 0;
+        }
+
+        offset += num;
+        bytes -= num;
+    }
+
+    return 0;
+}
+
+static int blockalloc_to_extents(BlockDriverState *bs, uint64_t offset,
+                                 uint64_t bytes, NBDExtentArray *ea)
+{
+    while (bytes) {
+        int64_t num;
+        int ret = bdrv_is_allocated_above(bs, NULL, false, offset, bytes,
+                                          &num);
+
+        if (ret < 0) {
+            return ret;
+        }
+
+        if (nbd_extent_array_add(ea, num, ret) < 0) {
+            return 0;
+        }
+
+        offset += num;
+        bytes -= num;
+    }
+
+    return 0;
+}
+
+/*
+ * nbd_co_send_extents
+ *
+ * @ea is converted to BE by the function
+ * @last controls whether NBD_REPLY_FLAG_DONE is sent.
+ */
+static int nbd_co_send_extents(NBDClient *client, uint64_t handle,
+                               NBDExtentArray *ea,
+                               bool last, uint32_t context_id, Error **errp)
+{
+    NBDStructuredMeta chunk;
+    struct iovec iov[] = {
+        {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+        {.iov_base = ea->extents, .iov_len = ea->count * sizeof(ea->extents[0])}
+    };
+
+    nbd_extent_array_convert_to_be(ea);
+
+    trace_nbd_co_send_extents(handle, ea->count, context_id, ea->total_length,
+                              last);
+    set_be_chunk(&chunk.h, last ? NBD_REPLY_FLAG_DONE : 0,
+                 NBD_REPLY_TYPE_BLOCK_STATUS,
+                 handle, sizeof(chunk) - sizeof(chunk.h) + iov[1].iov_len);
+    stl_be_p(&chunk.context_id, context_id);
+
+    return nbd_co_send_iov(client, iov, 2, errp);
+}
+
+/* Get block status from the exported device and send it to the client */
+static int nbd_co_send_block_status(NBDClient *client, uint64_t handle,
+                                    BlockDriverState *bs, uint64_t offset,
+                                    uint32_t length, bool dont_fragment,
+                                    bool last, uint32_t context_id,
+                                    Error **errp)
+{
+    int ret;
+    unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
+    g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
+
+    if (context_id == NBD_META_ID_BASE_ALLOCATION) {
+        ret = blockstatus_to_extents(bs, offset, length, ea);
+    } else {
+        ret = blockalloc_to_extents(bs, offset, length, ea);
+    }
+    if (ret < 0) {
+        return nbd_co_send_structured_error(
+                client, handle, -ret, "can't get block status", errp);
+    }
+
+    return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
+}
+
+/* Populate @ea from a dirty bitmap. */
+static void bitmap_to_extents(BdrvDirtyBitmap *bitmap,
+                              uint64_t offset, uint64_t length,
+                              NBDExtentArray *es)
+{
+    int64_t start, dirty_start, dirty_count;
+    int64_t end = offset + length;
+    bool full = false;
+
+    bdrv_dirty_bitmap_lock(bitmap);
+
+    for (start = offset;
+         bdrv_dirty_bitmap_next_dirty_area(bitmap, start, end, INT32_MAX,
+                                           &dirty_start, &dirty_count);
+         start = dirty_start + dirty_count)
+    {
+        if ((nbd_extent_array_add(es, dirty_start - start, 0) < 0) ||
+            (nbd_extent_array_add(es, dirty_count, NBD_STATE_DIRTY) < 0))
+        {
+            full = true;
+            break;
+        }
+    }
+
+    if (!full) {
+        /* last non dirty extent, nothing to do if array is now full */
+        (void) nbd_extent_array_add(es, end - start, 0);
+    }
+
+    bdrv_dirty_bitmap_unlock(bitmap);
+}
+
+static int nbd_co_send_bitmap(NBDClient *client, uint64_t handle,
+                              BdrvDirtyBitmap *bitmap, uint64_t offset,
+                              uint32_t length, bool dont_fragment, bool last,
+                              uint32_t context_id, Error **errp)
+{
+    unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
+    g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
+
+    bitmap_to_extents(bitmap, offset, length, ea);
+
+    return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
+}
+
+/* nbd_co_receive_request
+ * Collect a client request. Return 0 if request looks valid, -EIO to drop
+ * connection right away, -EAGAIN to indicate we were interrupted and the
+ * channel should be quiesced, and any other negative value to report an error
+ * to the client (although the caller may still need to disconnect after
+ * reporting the error).
+ */
+static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,
+                                  Error **errp)
+{
+    NBDClient *client = req->client;
+    int valid_flags;
+    int ret;
+
+    g_assert(qemu_in_coroutine());
+    assert(client->recv_coroutine == qemu_coroutine_self());
+    ret = nbd_receive_request(client, request, errp);
+    if (ret < 0) {
+        return  ret;
+    }
+
+    trace_nbd_co_receive_request_decode_type(request->handle, request->type,
+                                             nbd_cmd_lookup(request->type));
+
+    if (request->type != NBD_CMD_WRITE) {
+        /* No payload, we are ready to read the next request.  */
+        req->complete = true;
+    }
+
+    if (request->type == NBD_CMD_DISC) {
+        /* Special case: we're going to disconnect without a reply,
+         * whether or not flags, from, or len are bogus */
+        return -EIO;
+    }
+
+    if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE ||
+        request->type == NBD_CMD_CACHE)
+    {
+        if (request->len > NBD_MAX_BUFFER_SIZE) {
+            error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",
+                       request->len, NBD_MAX_BUFFER_SIZE);
+            return -EINVAL;
+        }
+
+        if (request->type != NBD_CMD_CACHE) {
+            req->data = blk_try_blockalign(client->exp->common.blk,
+                                           request->len);
+            if (req->data == NULL) {
+                error_setg(errp, "No memory");
+                return -ENOMEM;
+            }
+        }
+    }
+
+    if (request->type == NBD_CMD_WRITE) {
+        if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data",
+                     errp) < 0)
+        {
+            return -EIO;
+        }
+        req->complete = true;
+
+        trace_nbd_co_receive_request_payload_received(request->handle,
+                                                      request->len);
+    }
+
+    /* Sanity checks. */
+    if (client->exp->nbdflags & NBD_FLAG_READ_ONLY &&
+        (request->type == NBD_CMD_WRITE ||
+         request->type == NBD_CMD_WRITE_ZEROES ||
+         request->type == NBD_CMD_TRIM)) {
+        error_setg(errp, "Export is read-only");
+        return -EROFS;
+    }
+    if (request->from > client->exp->size ||
+        request->len > client->exp->size - request->from) {
+        error_setg(errp, "operation past EOF; From: %" PRIu64 ", Len: %" PRIu32
+                   ", Size: %" PRIu64, request->from, request->len,
+                   client->exp->size);
+        return (request->type == NBD_CMD_WRITE ||
+                request->type == NBD_CMD_WRITE_ZEROES) ? -ENOSPC : -EINVAL;
+    }
+    if (client->check_align && !QEMU_IS_ALIGNED(request->from | request->len,
+                                                client->check_align)) {
+        /*
+         * The block layer gracefully handles unaligned requests, but
+         * it's still worth tracing client non-compliance
+         */
+        trace_nbd_co_receive_align_compliance(nbd_cmd_lookup(request->type),
+                                              request->from,
+                                              request->len,
+                                              client->check_align);
+    }
+    valid_flags = NBD_CMD_FLAG_FUA;
+    if (request->type == NBD_CMD_READ && client->structured_reply) {
+        valid_flags |= NBD_CMD_FLAG_DF;
+    } else if (request->type == NBD_CMD_WRITE_ZEROES) {
+        valid_flags |= NBD_CMD_FLAG_NO_HOLE | NBD_CMD_FLAG_FAST_ZERO;
+    } else if (request->type == NBD_CMD_BLOCK_STATUS) {
+        valid_flags |= NBD_CMD_FLAG_REQ_ONE;
+    }
+    if (request->flags & ~valid_flags) {
+        error_setg(errp, "unsupported flags for command %s (got 0x%x)",
+                   nbd_cmd_lookup(request->type), request->flags);
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+/* Send simple reply without a payload, or a structured error
+ * @error_msg is ignored if @ret >= 0
+ * Returns 0 if connection is still live, -errno on failure to talk to client
+ */
+static coroutine_fn int nbd_send_generic_reply(NBDClient *client,
+                                               uint64_t handle,
+                                               int ret,
+                                               const char *error_msg,
+                                               Error **errp)
+{
+    if (client->structured_reply && ret < 0) {
+        return nbd_co_send_structured_error(client, handle, -ret, error_msg,
+                                            errp);
+    } else {
+        return nbd_co_send_simple_reply(client, handle, ret < 0 ? -ret : 0,
+                                        NULL, 0, errp);
+    }
+}
+
+/* Handle NBD_CMD_READ request.
+ * Return -errno if sending fails. Other errors are reported directly to the
+ * client as an error reply. */
+static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
+                                        uint8_t *data, Error **errp)
+{
+    int ret;
+    NBDExport *exp = client->exp;
+
+    assert(request->type == NBD_CMD_READ);
+
+    /* XXX: NBD Protocol only documents use of FUA with WRITE */
+    if (request->flags & NBD_CMD_FLAG_FUA) {
+        ret = blk_co_flush(exp->common.blk);
+        if (ret < 0) {
+            return nbd_send_generic_reply(client, request->handle, ret,
+                                          "flush failed", errp);
+        }
+    }
+
+    if (client->structured_reply && !(request->flags & NBD_CMD_FLAG_DF) &&
+        request->len)
+    {
+        return nbd_co_send_sparse_read(client, request->handle, request->from,
+                                       data, request->len, errp);
+    }
+
+    ret = blk_pread(exp->common.blk, request->from, data, request->len);
+    if (ret < 0) {
+        return nbd_send_generic_reply(client, request->handle, ret,
+                                      "reading from file failed", errp);
+    }
+
+    if (client->structured_reply) {
+        if (request->len) {
+            return nbd_co_send_structured_read(client, request->handle,
+                                               request->from, data,
+                                               request->len, true, errp);
+        } else {
+            return nbd_co_send_structured_done(client, request->handle, errp);
+        }
+    } else {
+        return nbd_co_send_simple_reply(client, request->handle, 0,
+                                        data, request->len, errp);
+    }
+}
+
+/*
+ * nbd_do_cmd_cache
+ *
+ * Handle NBD_CMD_CACHE request.
+ * Return -errno if sending fails. Other errors are reported directly to the
+ * client as an error reply.
+ */
+static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *request,
+                                         Error **errp)
+{
+    int ret;
+    NBDExport *exp = client->exp;
+
+    assert(request->type == NBD_CMD_CACHE);
+
+    ret = blk_co_preadv(exp->common.blk, request->from, request->len,
+                        NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
+
+    return nbd_send_generic_reply(client, request->handle, ret,
+                                  "caching data failed", errp);
+}
+
+/* Handle NBD request.
+ * Return -errno if sending fails. Other errors are reported directly to the
+ * client as an error reply. */
+static coroutine_fn int nbd_handle_request(NBDClient *client,
+                                           NBDRequest *request,
+                                           uint8_t *data, Error **errp)
+{
+    int ret;
+    int flags;
+    NBDExport *exp = client->exp;
+    char *msg;
+    size_t i;
+
+    switch (request->type) {
+    case NBD_CMD_CACHE:
+        return nbd_do_cmd_cache(client, request, errp);
+
+    case NBD_CMD_READ:
+        return nbd_do_cmd_read(client, request, data, errp);
+
+    case NBD_CMD_WRITE:
+        flags = 0;
+        if (request->flags & NBD_CMD_FLAG_FUA) {
+            flags |= BDRV_REQ_FUA;
+        }
+        ret = blk_pwrite(exp->common.blk, request->from, data, request->len,
+                         flags);
+        return nbd_send_generic_reply(client, request->handle, ret,
+                                      "writing to file failed", errp);
+
+    case NBD_CMD_WRITE_ZEROES:
+        flags = 0;
+        if (request->flags & NBD_CMD_FLAG_FUA) {
+            flags |= BDRV_REQ_FUA;
+        }
+        if (!(request->flags & NBD_CMD_FLAG_NO_HOLE)) {
+            flags |= BDRV_REQ_MAY_UNMAP;
+        }
+        if (request->flags & NBD_CMD_FLAG_FAST_ZERO) {
+            flags |= BDRV_REQ_NO_FALLBACK;
+        }
+        ret = blk_pwrite_zeroes(exp->common.blk, request->from, request->len,
+                                flags);
+        return nbd_send_generic_reply(client, request->handle, ret,
+                                      "writing to file failed", errp);
+
+    case NBD_CMD_DISC:
+        /* unreachable, thanks to special case in nbd_co_receive_request() */
+        abort();
+
+    case NBD_CMD_FLUSH:
+        ret = blk_co_flush(exp->common.blk);
+        return nbd_send_generic_reply(client, request->handle, ret,
+                                      "flush failed", errp);
+
+    case NBD_CMD_TRIM:
+        ret = blk_co_pdiscard(exp->common.blk, request->from, request->len);
+        if (ret >= 0 && request->flags & NBD_CMD_FLAG_FUA) {
+            ret = blk_co_flush(exp->common.blk);
+        }
+        return nbd_send_generic_reply(client, request->handle, ret,
+                                      "discard failed", errp);
+
+    case NBD_CMD_BLOCK_STATUS:
+        if (!request->len) {
+            return nbd_send_generic_reply(client, request->handle, -EINVAL,
+                                          "need non-zero length", errp);
+        }
+        if (client->export_meta.count) {
+            bool dont_fragment = request->flags & NBD_CMD_FLAG_REQ_ONE;
+            int contexts_remaining = client->export_meta.count;
+
+            if (client->export_meta.base_allocation) {
+                ret = nbd_co_send_block_status(client, request->handle,
+                                               blk_bs(exp->common.blk),
+                                               request->from,
+                                               request->len, dont_fragment,
+                                               !--contexts_remaining,
+                                               NBD_META_ID_BASE_ALLOCATION,
+                                               errp);
+                if (ret < 0) {
+                    return ret;
+                }
+            }
+
+            if (client->export_meta.allocation_depth) {
+                ret = nbd_co_send_block_status(client, request->handle,
+                                               blk_bs(exp->common.blk),
+                                               request->from, request->len,
+                                               dont_fragment,
+                                               !--contexts_remaining,
+                                               NBD_META_ID_ALLOCATION_DEPTH,
+                                               errp);
+                if (ret < 0) {
+                    return ret;
+                }
+            }
+
+            for (i = 0; i < client->exp->nr_export_bitmaps; i++) {
+                if (!client->export_meta.bitmaps[i]) {
+                    continue;
+                }
+                ret = nbd_co_send_bitmap(client, request->handle,
+                                         client->exp->export_bitmaps[i],
+                                         request->from, request->len,
+                                         dont_fragment, !--contexts_remaining,
+                                         NBD_META_ID_DIRTY_BITMAP + i, errp);
+                if (ret < 0) {
+                    return ret;
+                }
+            }
+
+            assert(!contexts_remaining);
+
+            return 0;
+        } else {
+            return nbd_send_generic_reply(client, request->handle, -EINVAL,
+                                          "CMD_BLOCK_STATUS not negotiated",
+                                          errp);
+        }
+
+    default:
+        msg = g_strdup_printf("invalid request type (%" PRIu32 ") received",
+                              request->type);
+        ret = nbd_send_generic_reply(client, request->handle, -EINVAL, msg,
+                                     errp);
+        g_free(msg);
+        return ret;
+    }
+}
+
+/* Owns a reference to the NBDClient passed as opaque.  */
+static coroutine_fn void nbd_trip(void *opaque)
+{
+    NBDClient *client = opaque;
+    NBDRequestData *req;
+    NBDRequest request = { 0 };    /* GCC thinks it can be used uninitialized */
+    int ret;
+    Error *local_err = NULL;
+
+    trace_nbd_trip();
+    if (client->closing) {
+        nbd_client_put(client);
+        return;
+    }
+
+    if (client->quiescing) {
+        /*
+         * We're switching between AIO contexts. Don't attempt to receive a new
+         * request and kick the main context which may be waiting for us.
+         */
+        nbd_client_put(client);
+        client->recv_coroutine = NULL;
+        aio_wait_kick();
+        return;
+    }
+
+    req = nbd_request_get(client);
+    ret = nbd_co_receive_request(req, &request, &local_err);
+    client->recv_coroutine = NULL;
+
+    if (client->closing) {
+        /*
+         * The client may be closed when we are blocked in
+         * nbd_co_receive_request()
+         */
+        goto done;
+    }
+
+    if (ret == -EAGAIN) {
+        assert(client->quiescing);
+        goto done;
+    }
+
+    nbd_client_receive_next_request(client);
+    if (ret == -EIO) {
+        goto disconnect;
+    }
+
+    if (ret < 0) {
+        /* It wans't -EIO, so, according to nbd_co_receive_request()
+         * semantics, we should return the error to the client. */
+        Error *export_err = local_err;
+
+        local_err = NULL;
+        ret = nbd_send_generic_reply(client, request.handle, -EINVAL,
+                                     error_get_pretty(export_err), &local_err);
+        error_free(export_err);
+    } else {
+        ret = nbd_handle_request(client, &request, req->data, &local_err);
+    }
+    if (ret < 0) {
+        error_prepend(&local_err, "Failed to send reply: ");
+        goto disconnect;
+    }
+
+    /* We must disconnect after NBD_CMD_WRITE if we did not
+     * read the payload.
+     */
+    if (!req->complete) {
+        error_setg(&local_err, "Request handling failed in intermediate state");
+        goto disconnect;
+    }
+
+done:
+    nbd_request_put(req);
+    nbd_client_put(client);
+    return;
+
+disconnect:
+    if (local_err) {
+        error_reportf_err(local_err, "Disconnect client, due to: ");
+    }
+    nbd_request_put(req);
+    client_close(client, true);
+    nbd_client_put(client);
+}
+
+static void nbd_client_receive_next_request(NBDClient *client)
+{
+    if (!client->recv_coroutine && client->nb_requests < MAX_NBD_REQUESTS &&
+        !client->quiescing) {
+        nbd_client_get(client);
+        client->recv_coroutine = qemu_coroutine_create(nbd_trip, client);
+        aio_co_schedule(client->exp->common.ctx, client->recv_coroutine);
+    }
+}
+
+static coroutine_fn void nbd_co_client_start(void *opaque)
+{
+    NBDClient *client = opaque;
+    Error *local_err = NULL;
+
+    qemu_co_mutex_init(&client->send_lock);
+
+    if (nbd_negotiate(client, &local_err)) {
+        if (local_err) {
+            error_report_err(local_err);
+        }
+        client_close(client, false);
+        return;
+    }
+
+    nbd_client_receive_next_request(client);
+}
+
+/*
+ * Create a new client listener using the given channel @sioc.
+ * Begin servicing it in a coroutine.  When the connection closes, call
+ * @close_fn with an indication of whether the client completed negotiation.
+ */
+void nbd_client_new(QIOChannelSocket *sioc,
+                    QCryptoTLSCreds *tlscreds,
+                    const char *tlsauthz,
+                    void (*close_fn)(NBDClient *, bool))
+{
+    NBDClient *client;
+    Coroutine *co;
+
+    client = g_new0(NBDClient, 1);
+    client->refcount = 1;
+    client->tlscreds = tlscreds;
+    if (tlscreds) {
+        object_ref(OBJECT(client->tlscreds));
+    }
+    client->tlsauthz = g_strdup(tlsauthz);
+    client->sioc = sioc;
+    object_ref(OBJECT(client->sioc));
+    client->ioc = QIO_CHANNEL(sioc);
+    object_ref(OBJECT(client->ioc));
+    client->close_fn = close_fn;
+
+    co = qemu_coroutine_create(nbd_co_client_start, client);
+    qemu_coroutine_enter(co);
+}
diff --git a/nbd/trace-events b/nbd/trace-events
new file mode 100644
index 000000000..c4919a2dd
--- /dev/null
+++ b/nbd/trace-events
@@ -0,0 +1,75 @@
+# See docs/devel/tracing.rst for syntax documentation.
+
+# client.c
+nbd_send_option_request(uint32_t opt, const char *name, uint32_t len) "Sending option request %" PRIu32" (%s), len %" PRIu32
+nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t type, const char *typename, uint32_t length) "Received option reply %" PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32
+nbd_server_error_msg(uint32_t err, const char *type, const char *msg) "server reported error 0x%" PRIx32 " (%s) with additional message: %s"
+nbd_reply_err_ignored(uint32_t option, const char *name, uint32_t reply, const char *reply_name) "server failed request %" PRIu32 " (%s) with error 0x%" PRIx32 " (%s), attempting fallback"
+nbd_receive_list(const char *name, const char *desc) "export list includes '%s', description '%s'"
+nbd_opt_info_go_start(const char *opt, const char *name) "Attempting %s for export '%s'"
+nbd_opt_info_go_success(const char *opt) "Export is ready after %s request"
+nbd_opt_info_unknown(int info, const char *name) "Ignoring unknown info %d (%s)"
+nbd_opt_info_block_size(uint32_t minimum, uint32_t preferred, uint32_t maximum) "Block sizes are 0x%" PRIx32 ", 0x%" PRIx32 ", 0x%" PRIx32
+nbd_receive_query_exports_start(const char *wantname) "Querying export list for '%s'"
+nbd_receive_query_exports_success(const char *wantname) "Found desired export name '%s'"
+nbd_receive_starttls_new_client(void) "Setting up TLS"
+nbd_receive_starttls_tls_handshake(void) "Starting TLS handshake"
+nbd_opt_meta_request(const char *optname, const char *context, const char *export) "Requesting %s %s for export %s"
+nbd_opt_meta_reply(const char *optname, const char *context, uint32_t id) "Received %s mapping of %s to id %" PRIu32
+nbd_start_negotiate(void *tlscreds, const char *hostname) "Receiving negotiation tlscreds=%p hostname=%s"
+nbd_receive_negotiate_magic(uint64_t magic) "Magic is 0x%" PRIx64
+nbd_receive_negotiate_server_flags(uint32_t globalflags) "Global flags are 0x%" PRIx32
+nbd_receive_negotiate_name(const char *name) "Requesting NBD export name '%s'"
+nbd_receive_negotiate_size_flags(uint64_t size, uint16_t flags) "Size is %" PRIu64 ", export flags 0x%" PRIx16
+nbd_init_set_socket(void) "Setting NBD socket"
+nbd_init_set_block_size(unsigned long block_size) "Setting block size to %lu"
+nbd_init_set_size(unsigned long sectors) "Setting size to %lu block(s)"
+nbd_init_trailing_bytes(int ignored_bytes) "Ignoring trailing %d bytes of export"
+nbd_init_set_readonly(void) "Setting readonly attribute"
+nbd_init_finish(void) "Negotiation ended"
+nbd_client_loop(void) "Doing NBD loop"
+nbd_client_loop_ret(int ret, const char *error) "NBD loop returned %d: %s"
+nbd_client_clear_queue(void) "Clearing NBD queue"
+nbd_client_clear_socket(void) "Clearing NBD socket"
+nbd_send_request(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name) "Sending request to server: { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) }"
+nbd_receive_simple_reply(int32_t error, const char *errname, uint64_t handle) "Got simple reply: { .error = %" PRId32 " (%s), handle = %" PRIu64" }"
+nbd_receive_structured_reply_chunk(uint16_t flags, uint16_t type, const char *name, uint64_t handle, uint32_t length) "Got structured reply chunk: { flags = 0x%" PRIx16 ", type = %d (%s), handle = %" PRIu64 ", length = %" PRIu32 " }"
+
+# common.c
+nbd_unknown_error(int err) "Squashing unexpected error %d to EINVAL"
+
+# server.c
+nbd_negotiate_send_rep_len(uint32_t opt, const char *optname, uint32_t type, const char *typename, uint32_t len) "Reply opt=%" PRIu32 " (%s), type=%" PRIu32 " (%s), len=%" PRIu32
+nbd_negotiate_send_rep_err(const char *msg) "sending error message \"%s\""
+nbd_negotiate_send_rep_list(const char *name, const char *desc) "Advertising export name '%s' description '%s'"
+nbd_negotiate_handle_export_name(void) "Checking length"
+nbd_negotiate_handle_export_name_request(const char *name) "Client requested export '%s'"
+nbd_negotiate_send_info(int info, const char *name, uint32_t length) "Sending NBD_REP_INFO type %d (%s) with remaining length %" PRIu32
+nbd_negotiate_handle_info_requests(int requests) "Client requested %d items of info"
+nbd_negotiate_handle_info_request(int request, const char *name) "Client requested info %d (%s)"
+nbd_negotiate_handle_info_block_size(uint32_t minimum, uint32_t preferred, uint32_t maximum) "advertising minimum 0x%" PRIx32 ", preferred 0x%" PRIx32 ", maximum 0x%" PRIx32
+nbd_negotiate_handle_starttls(void) "Setting up TLS"
+nbd_negotiate_handle_starttls_handshake(void) "Starting TLS handshake"
+nbd_negotiate_meta_context(const char *optname, const char *export, uint32_t queries) "Client requested %s for export %s, with %" PRIu32 " queries"
+nbd_negotiate_meta_query_skip(const char *reason) "Skipping meta query: %s"
+nbd_negotiate_meta_query_parse(const char *query) "Parsed meta query '%s'"
+nbd_negotiate_meta_query_reply(const char *context, uint32_t id) "Replying with meta context '%s' id %" PRIu32
+nbd_negotiate_options_flags(uint32_t flags) "Received client flags 0x%" PRIx32
+nbd_negotiate_options_check_magic(uint64_t magic) "Checking opts magic 0x%" PRIx64
+nbd_negotiate_options_check_option(uint32_t option, const char *name) "Checking option %" PRIu32 " (%s)"
+nbd_negotiate_begin(void) "Beginning negotiation"
+nbd_negotiate_new_style_size_flags(uint64_t size, unsigned flags) "advertising size %" PRIu64 " and flags 0x%x"
+nbd_negotiate_success(void) "Negotiation succeeded"
+nbd_receive_request(uint32_t magic, uint16_t flags, uint16_t type, uint64_t from, uint32_t len) "Got request: { magic = 0x%" PRIx32 ", .flags = 0x%" PRIx16 ", .type = 0x%" PRIx16 ", from = %" PRIu64 ", len = %" PRIu32 " }"
+nbd_blk_aio_attached(const char *name, void *ctx) "Export %s: Attaching clients to AIO context %p"
+nbd_blk_aio_detach(const char *name, void *ctx) "Export %s: Detaching clients from AIO context %p"
+nbd_co_send_simple_reply(uint64_t handle, uint32_t error, const char *errname, int len) "Send simple reply: handle = %" PRIu64 ", error = %" PRIu32 " (%s), len = %d"
+nbd_co_send_structured_done(uint64_t handle) "Send structured reply done: handle = %" PRIu64
+nbd_co_send_structured_read(uint64_t handle, uint64_t offset, void *data, size_t size) "Send structured read data reply: handle = %" PRIu64 ", offset = %" PRIu64 ", data = %p, len = %zu"
+nbd_co_send_structured_read_hole(uint64_t handle, uint64_t offset, size_t size) "Send structured read hole reply: handle = %" PRIu64 ", offset = %" PRIu64 ", len = %zu"
+nbd_co_send_extents(uint64_t handle, unsigned int extents, uint32_t id, uint64_t length, int last) "Send block status reply: handle = %" PRIu64 ", extents = %u, context = %d (extents cover %" PRIu64 " bytes, last chunk = %d)"
+nbd_co_send_structured_error(uint64_t handle, int err, const char *errname, const char *msg) "Send structured error reply: handle = %" PRIu64 ", error = %d (%s), msg = '%s'"
+nbd_co_receive_request_decode_type(uint64_t handle, uint16_t type, const char *name) "Decoding type: handle = %" PRIu64 ", type = %" PRIu16 " (%s)"
+nbd_co_receive_request_payload_received(uint64_t handle, uint32_t len) "Payload received: handle = %" PRIu64 ", len = %" PRIu32
+nbd_co_receive_align_compliance(const char *op, uint64_t from, uint32_t len, uint32_t align) "client sent non-compliant unaligned %s request: from=0x%" PRIx64 ", len=0x%" PRIx32 ", align=0x%" PRIx32
+nbd_trip(void) "Reading request"
diff --git a/nbd/trace.h b/nbd/trace.h
new file mode 100644
index 000000000..233d08fdd
--- /dev/null
+++ b/nbd/trace.h
@@ -0,0 +1 @@
+#include "trace/trace-nbd.h"
author	Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>	2023-10-10 11:40:56 +0000
committer	Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>	2023-10-10 11:40:56 +0000
commit	e02cda008591317b1625707ff8e115a4841aa889 (patch)
tree	aee302e3cf8b59ec2d32ec481be3d1afddfc8968 /nbd
parent	cc668e6b7e0ffd8c9d130513d12053cf5eda1d3b (diff)