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

14 files changed, 2452 insertions, 0 deletions

diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c
new file mode 100644
index 000000000..a1c9beddd
--- /dev/null
+++ b/fsdev/9p-iov-marshal.c
@@ -0,0 +1,306 @@
+/*
+ * 9p backend
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include <glib/gprintf.h>
+#include <utime.h>
+
+#include "9p-iov-marshal.h"
+#include "qemu/bswap.h"
+
+static ssize_t v9fs_packunpack(void *addr, struct iovec *sg, int sg_count,
+                               size_t offset, size_t size, int pack)
+{
+    int i = 0;
+    size_t copied = 0;
+    size_t req_size = size;
+
+
+    for (i = 0; size && i < sg_count; i++) {
+        size_t len;
+        if (offset >= sg[i].iov_len) {
+            /* skip this sg */
+            offset -= sg[i].iov_len;
+            continue;
+        } else {
+            len = MIN(sg[i].iov_len - offset, size);
+            if (pack) {
+                memcpy(sg[i].iov_base + offset, addr, len);
+            } else {
+                memcpy(addr, sg[i].iov_base + offset, len);
+            }
+            size -= len;
+            copied += len;
+            addr += len;
+            if (size) {
+                offset = 0;
+                continue;
+            }
+        }
+    }
+    if (copied < req_size) {
+        /*
+         * We copied less that requested size. error out
+         */
+        return -ENOBUFS;
+    }
+    return copied;
+}
+
+static ssize_t v9fs_unpack(void *dst, struct iovec *out_sg, int out_num,
+                           size_t offset, size_t size)
+{
+    return v9fs_packunpack(dst, out_sg, out_num, offset, size, 0);
+}
+
+ssize_t v9fs_pack(struct iovec *in_sg, int in_num, size_t offset,
+                  const void *src, size_t size)
+{
+    return v9fs_packunpack((void *)src, in_sg, in_num, offset, size, 1);
+}
+
+ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                            int bswap, const char *fmt, va_list ap)
+{
+    int i;
+    ssize_t copied = 0;
+    size_t old_offset = offset;
+
+    for (i = 0; fmt[i]; i++) {
+        switch (fmt[i]) {
+        case 'b': {
+            uint8_t *valp = va_arg(ap, uint8_t *);
+            copied = v9fs_unpack(valp, out_sg, out_num, offset, sizeof(*valp));
+            break;
+        }
+        case 'w': {
+            uint16_t val, *valp;
+            valp = va_arg(ap, uint16_t *);
+            copied = v9fs_unpack(&val, out_sg, out_num, offset, sizeof(val));
+            if (bswap) {
+                *valp = le16_to_cpu(val);
+            } else {
+                *valp = val;
+            }
+            break;
+        }
+        case 'd': {
+            uint32_t val, *valp;
+            valp = va_arg(ap, uint32_t *);
+            copied = v9fs_unpack(&val, out_sg, out_num, offset, sizeof(val));
+            if (bswap) {
+                *valp = le32_to_cpu(val);
+            } else {
+                *valp = val;
+            }
+            break;
+        }
+        case 'q': {
+            uint64_t val, *valp;
+            valp = va_arg(ap, uint64_t *);
+            copied = v9fs_unpack(&val, out_sg, out_num, offset, sizeof(val));
+            if (bswap) {
+                *valp = le64_to_cpu(val);
+            } else {
+                *valp = val;
+            }
+            break;
+        }
+        case 's': {
+            V9fsString *str = va_arg(ap, V9fsString *);
+            copied = v9fs_iov_unmarshal(out_sg, out_num, offset, bswap,
+                                        "w", &str->size);
+            if (copied > 0) {
+                offset += copied;
+                str->data = g_malloc(str->size + 1);
+                copied = v9fs_unpack(str->data, out_sg, out_num, offset,
+                                     str->size);
+                if (copied >= 0) {
+                    str->data[str->size] = 0;
+                } else {
+                    v9fs_string_free(str);
+                }
+            }
+            break;
+        }
+        case 'Q': {
+            V9fsQID *qidp = va_arg(ap, V9fsQID *);
+            copied = v9fs_iov_unmarshal(out_sg, out_num, offset, bswap,
+                                        "bdq", &qidp->type, &qidp->version,
+                                        &qidp->path);
+            break;
+        }
+        case 'S': {
+            V9fsStat *statp = va_arg(ap, V9fsStat *);
+            copied = v9fs_iov_unmarshal(out_sg, out_num, offset, bswap,
+                                        "wwdQdddqsssssddd",
+                                        &statp->size, &statp->type,
+                                        &statp->dev, &statp->qid,
+                                        &statp->mode, &statp->atime,
+                                        &statp->mtime, &statp->length,
+                                        &statp->name, &statp->uid,
+                                        &statp->gid, &statp->muid,
+                                        &statp->extension,
+                                        &statp->n_uid, &statp->n_gid,
+                                        &statp->n_muid);
+            break;
+        }
+        case 'I': {
+            V9fsIattr *iattr = va_arg(ap, V9fsIattr *);
+            copied = v9fs_iov_unmarshal(out_sg, out_num, offset, bswap,
+                                        "ddddqqqqq",
+                                        &iattr->valid, &iattr->mode,
+                                        &iattr->uid, &iattr->gid,
+                                        &iattr->size, &iattr->atime_sec,
+                                        &iattr->atime_nsec,
+                                        &iattr->mtime_sec,
+                                        &iattr->mtime_nsec);
+            break;
+        }
+        default:
+            g_assert_not_reached();
+        }
+        if (copied < 0) {
+            return copied;
+        }
+        offset += copied;
+    }
+
+    return offset - old_offset;
+}
+
+ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                           int bswap, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vunmarshal(out_sg, out_num, offset, bswap, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+ssize_t v9fs_iov_vmarshal(struct iovec *in_sg, int in_num, size_t offset,
+                          int bswap, const char *fmt, va_list ap)
+{
+    int i;
+    ssize_t copied = 0;
+    size_t old_offset = offset;
+
+    for (i = 0; fmt[i]; i++) {
+        switch (fmt[i]) {
+        case 'b': {
+            uint8_t val = va_arg(ap, int);
+            copied = v9fs_pack(in_sg, in_num, offset, &val, sizeof(val));
+            break;
+        }
+        case 'w': {
+            uint16_t val = va_arg(ap, int);
+            if (bswap) {
+                val = cpu_to_le16(val);
+            }
+            copied = v9fs_pack(in_sg, in_num, offset, &val, sizeof(val));
+            break;
+        }
+        case 'd': {
+            uint32_t val = va_arg(ap, uint32_t);
+            if (bswap) {
+                val = cpu_to_le32(val);
+            }
+            copied = v9fs_pack(in_sg, in_num, offset, &val, sizeof(val));
+            break;
+        }
+        case 'q': {
+            uint64_t val = va_arg(ap, uint64_t);
+            if (bswap) {
+                val = cpu_to_le64(val);
+            }
+            copied = v9fs_pack(in_sg, in_num, offset, &val, sizeof(val));
+            break;
+        }
+        case 's': {
+            V9fsString *str = va_arg(ap, V9fsString *);
+            copied = v9fs_iov_marshal(in_sg, in_num, offset, bswap,
+                                      "w", str->size);
+            if (copied > 0) {
+                offset += copied;
+                copied = v9fs_pack(in_sg, in_num, offset, str->data, str->size);
+            }
+            break;
+        }
+        case 'Q': {
+            V9fsQID *qidp = va_arg(ap, V9fsQID *);
+            copied = v9fs_iov_marshal(in_sg, in_num, offset, bswap, "bdq",
+                                      qidp->type, qidp->version,
+                                      qidp->path);
+            break;
+        }
+        case 'S': {
+            V9fsStat *statp = va_arg(ap, V9fsStat *);
+            copied = v9fs_iov_marshal(in_sg, in_num, offset, bswap,
+                                      "wwdQdddqsssssddd",
+                                      statp->size, statp->type, statp->dev,
+                                      &statp->qid, statp->mode, statp->atime,
+                                      statp->mtime, statp->length,
+                                      &statp->name,
+                                      &statp->uid, &statp->gid, &statp->muid,
+                                      &statp->extension, statp->n_uid,
+                                      statp->n_gid, statp->n_muid);
+            break;
+        }
+        case 'A': {
+            V9fsStatDotl *statp = va_arg(ap, V9fsStatDotl *);
+            copied = v9fs_iov_marshal(in_sg, in_num, offset, bswap,
+                                      "qQdddqqqqqqqqqqqqqqq",
+                                      statp->st_result_mask,
+                                      &statp->qid, statp->st_mode,
+                                      statp->st_uid, statp->st_gid,
+                                      statp->st_nlink, statp->st_rdev,
+                                      statp->st_size, statp->st_blksize,
+                                      statp->st_blocks, statp->st_atime_sec,
+                                      statp->st_atime_nsec,
+                                      statp->st_mtime_sec,
+                                      statp->st_mtime_nsec,
+                                      statp->st_ctime_sec,
+                                      statp->st_ctime_nsec,
+                                      statp->st_btime_sec,
+                                      statp->st_btime_nsec, statp->st_gen,
+                                      statp->st_data_version);
+            break;
+        }
+        default:
+            g_assert_not_reached();
+        }
+        if (copied < 0) {
+            return copied;
+        }
+        offset += copied;
+    }
+
+    return offset - old_offset;
+}
+
+ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
+                         int bswap, const char *fmt, ...)
+{
+    ssize_t ret;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = v9fs_iov_vmarshal(in_sg, in_num, offset, bswap, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
diff --git a/fsdev/9p-iov-marshal.h b/fsdev/9p-iov-marshal.h
new file mode 100644
index 000000000..1fb501685
--- /dev/null
+++ b/fsdev/9p-iov-marshal.h
@@ -0,0 +1,18 @@
+#ifndef QEMU_9P_IOV_MARSHAL_H
+#define QEMU_9P_IOV_MARSHAL_H
+
+#include "9p-marshal.h"
+
+
+ssize_t v9fs_pack(struct iovec *in_sg, int in_num, size_t offset,
+                  const void *src, size_t size);
+ssize_t v9fs_iov_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                           int bswap, const char *fmt, ...);
+ssize_t v9fs_iov_marshal(struct iovec *in_sg, int in_num, size_t offset,
+                         int bswap, const char *fmt, ...);
+
+ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset,
+                            int bswap, const char *fmt, va_list ap);
+ssize_t v9fs_iov_vmarshal(struct iovec *in_sg, int in_num, size_t offset,
+                          int bswap, const char *fmt, va_list ap);
+#endif
diff --git a/fsdev/9p-marshal.c b/fsdev/9p-marshal.c
new file mode 100644
index 000000000..51881fe22
--- /dev/null
+++ b/fsdev/9p-marshal.c
@@ -0,0 +1,46 @@
+/*
+ * 9p backend
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include <glib/gprintf.h>
+#include <dirent.h>
+#include <utime.h>
+
+#include "9p-marshal.h"
+
+P9ARRAY_DEFINE_TYPE(V9fsString, v9fs_string_free);
+
+void v9fs_string_free(V9fsString *str)
+{
+    g_free(str->data);
+    str->data = NULL;
+    str->size = 0;
+}
+
+void GCC_FMT_ATTR(2, 3)
+v9fs_string_sprintf(V9fsString *str, const char *fmt, ...)
+{
+    va_list ap;
+
+    v9fs_string_free(str);
+
+    va_start(ap, fmt);
+    str->size = g_vasprintf(&str->data, fmt, ap);
+    va_end(ap);
+}
+
+void v9fs_string_copy(V9fsString *lhs, V9fsString *rhs)
+{
+    v9fs_string_free(lhs);
+    v9fs_string_sprintf(lhs, "%s", rhs->data);
+}
diff --git a/fsdev/9p-marshal.h b/fsdev/9p-marshal.h
new file mode 100644
index 000000000..f1abbe151
--- /dev/null
+++ b/fsdev/9p-marshal.h
@@ -0,0 +1,82 @@
+#ifndef QEMU_9P_MARSHAL_H
+#define QEMU_9P_MARSHAL_H
+
+#include "p9array.h"
+
+typedef struct V9fsString {
+    uint16_t size;
+    char *data;
+} V9fsString;
+P9ARRAY_DECLARE_TYPE(V9fsString);
+
+typedef struct V9fsQID {
+    uint8_t type;
+    uint32_t version;
+    uint64_t path;
+} V9fsQID;
+
+typedef struct V9fsStat {
+    int16_t size;
+    int16_t type;
+    int32_t dev;
+    V9fsQID qid;
+    int32_t mode;
+    int32_t atime;
+    int32_t mtime;
+    int64_t length;
+    V9fsString name;
+    V9fsString uid;
+    V9fsString gid;
+    V9fsString muid;
+    /* 9p2000.u */
+    V9fsString extension;
+    int32_t n_uid;
+    int32_t n_gid;
+    int32_t n_muid;
+} V9fsStat;
+
+typedef struct V9fsIattr {
+    int32_t valid;
+    int32_t mode;
+    int32_t uid;
+    int32_t gid;
+    int64_t size;
+    int64_t atime_sec;
+    int64_t atime_nsec;
+    int64_t mtime_sec;
+    int64_t mtime_nsec;
+} V9fsIattr;
+
+typedef struct V9fsStatDotl {
+    uint64_t st_result_mask;
+    V9fsQID qid;
+    uint32_t st_mode;
+    uint32_t st_uid;
+    uint32_t st_gid;
+    uint64_t st_nlink;
+    uint64_t st_rdev;
+    uint64_t st_size;
+    uint64_t st_blksize;
+    uint64_t st_blocks;
+    uint64_t st_atime_sec;
+    uint64_t st_atime_nsec;
+    uint64_t st_mtime_sec;
+    uint64_t st_mtime_nsec;
+    uint64_t st_ctime_sec;
+    uint64_t st_ctime_nsec;
+    uint64_t st_btime_sec;
+    uint64_t st_btime_nsec;
+    uint64_t st_gen;
+    uint64_t st_data_version;
+} V9fsStatDotl;
+
+static inline void v9fs_string_init(V9fsString *str)
+{
+    str->data = NULL;
+    str->size = 0;
+}
+void v9fs_string_free(V9fsString *str);
+void v9fs_string_sprintf(V9fsString *str, const char *fmt, ...);
+void v9fs_string_copy(V9fsString *lhs, V9fsString *rhs);
+
+#endif
diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
new file mode 100644
index 000000000..8fd89f044
--- /dev/null
+++ b/fsdev/file-op-9p.h
@@ -0,0 +1,162 @@
+/*
+ * 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef FILE_OP_9P_H
+#define FILE_OP_9P_H
+
+#include <dirent.h>
+#include <utime.h>
+#include <sys/vfs.h>
+#include "qemu-fsdev-throttle.h"
+#include "p9array.h"
+
+#define SM_LOCAL_MODE_BITS    0600
+#define SM_LOCAL_DIR_MODE_BITS    0700
+
+typedef struct FsCred {
+    uid_t   fc_uid;
+    gid_t   fc_gid;
+    mode_t  fc_mode;
+    dev_t   fc_rdev;
+} FsCred;
+
+typedef struct FsContext FsContext;
+typedef struct V9fsPath V9fsPath;
+
+typedef struct ExtendedOps {
+    int (*get_st_gen)(FsContext *, V9fsPath *, mode_t, uint64_t *);
+} ExtendedOps;
+
+/* export flags */
+#define V9FS_IMMEDIATE_WRITEOUT     0x00000001
+#define V9FS_PATHNAME_FSCONTEXT     0x00000002
+/*
+ * uid/gid set on fileserver files
+ */
+#define V9FS_SM_PASSTHROUGH         0x00000004
+/*
+ * uid/gid part of xattr
+ */
+#define V9FS_SM_MAPPED              0x00000008
+/*
+ * Server will try to set uid/gid.
+ * On failure ignore the error.
+ */
+#define V9FS_SM_NONE                0x00000010
+/*
+ * uid/gid part of .virtfs_meatadata namespace
+ */
+#define V9FS_SM_MAPPED_FILE         0x00000020
+#define V9FS_RDONLY                 0x00000040
+#define V9FS_PROXY_SOCK_FD          0x00000080
+#define V9FS_PROXY_SOCK_NAME        0x00000100
+/*
+ * multidevs option (either one of the two applies exclusively)
+ */
+#define V9FS_REMAP_INODES           0x00000200
+#define V9FS_FORBID_MULTIDEVS       0x00000400
+/*
+ * Disables certain performance warnings from being logged on host side.
+ */
+#define V9FS_NO_PERF_WARN           0x00000800
+
+#define V9FS_SEC_MASK               0x0000003C
+
+
+typedef struct FileOperations FileOperations;
+typedef struct XattrOperations XattrOperations;
+
+/*
+ * Structure to store the various fsdev's passed through command line.
+ */
+typedef struct FsDriverEntry {
+    char *fsdev_id;
+    char *path;
+    int export_flags;
+    FileOperations *ops;
+    FsThrottle fst;
+    mode_t fmode;
+    mode_t dmode;
+} FsDriverEntry;
+
+struct FsContext {
+    uid_t uid;
+    char *fs_root;
+    int export_flags;
+    XattrOperations **xops;
+    ExtendedOps exops;
+    FsThrottle *fst;
+    /* fs driver specific data */
+    void *private;
+    mode_t fmode;
+    mode_t dmode;
+};
+
+struct V9fsPath {
+    uint16_t size;
+    char *data;
+};
+P9ARRAY_DECLARE_TYPE(V9fsPath);
+
+typedef union V9fsFidOpenState V9fsFidOpenState;
+
+void cred_init(FsCred *);
+
+struct FileOperations {
+    int (*parse_opts)(QemuOpts *, FsDriverEntry *, Error **errp);
+    int (*init)(FsContext *, Error **errp);
+    void (*cleanup)(FsContext *);
+    int (*lstat)(FsContext *, V9fsPath *, struct stat *);
+    ssize_t (*readlink)(FsContext *, V9fsPath *, char *, size_t);
+    int (*chmod)(FsContext *, V9fsPath *, FsCred *);
+    int (*chown)(FsContext *, V9fsPath *, FsCred *);
+    int (*mknod)(FsContext *, V9fsPath *, const char *, FsCred *);
+    int (*utimensat)(FsContext *, V9fsPath *, const struct timespec *);
+    int (*remove)(FsContext *, const char *);
+    int (*symlink)(FsContext *, const char *, V9fsPath *,
+                   const char *, FsCred *);
+    int (*link)(FsContext *, V9fsPath *, V9fsPath *, const char *);
+    int (*setuid)(FsContext *, uid_t);
+    int (*close)(FsContext *, V9fsFidOpenState *);
+    int (*closedir)(FsContext *, V9fsFidOpenState *);
+    int (*opendir)(FsContext *, V9fsPath *, V9fsFidOpenState *);
+    int (*open)(FsContext *, V9fsPath *, int, V9fsFidOpenState *);
+    int (*open2)(FsContext *, V9fsPath *, const char *,
+                 int, FsCred *, V9fsFidOpenState *);
+    void (*rewinddir)(FsContext *, V9fsFidOpenState *);
+    off_t (*telldir)(FsContext *, V9fsFidOpenState *);
+    struct dirent * (*readdir)(FsContext *, V9fsFidOpenState *);
+    void (*seekdir)(FsContext *, V9fsFidOpenState *, off_t);
+    ssize_t (*preadv)(FsContext *, V9fsFidOpenState *,
+                      const struct iovec *, int, off_t);
+    ssize_t (*pwritev)(FsContext *, V9fsFidOpenState *,
+                       const struct iovec *, int, off_t);
+    int (*mkdir)(FsContext *, V9fsPath *, const char *, FsCred *);
+    int (*fstat)(FsContext *, int, V9fsFidOpenState *, struct stat *);
+    int (*rename)(FsContext *, const char *, const char *);
+    int (*truncate)(FsContext *, V9fsPath *, off_t);
+    int (*fsync)(FsContext *, int, V9fsFidOpenState *, int);
+    int (*statfs)(FsContext *s, V9fsPath *path, struct statfs *stbuf);
+    ssize_t (*lgetxattr)(FsContext *, V9fsPath *,
+                         const char *, void *, size_t);
+    ssize_t (*llistxattr)(FsContext *, V9fsPath *, void *, size_t);
+    int (*lsetxattr)(FsContext *, V9fsPath *,
+                     const char *, void *, size_t, int);
+    int (*lremovexattr)(FsContext *, V9fsPath *, const char *);
+    int (*name_to_path)(FsContext *, V9fsPath *, const char *, V9fsPath *);
+    int (*renameat)(FsContext *ctx, V9fsPath *olddir, const char *old_name,
+                    V9fsPath *newdir, const char *new_name);
+    int (*unlinkat)(FsContext *ctx, V9fsPath *dir, const char *name, int flags);
+};
+
+#endif
diff --git a/fsdev/meson.build b/fsdev/meson.build
new file mode 100644
index 000000000..adf57cc43
--- /dev/null
+++ b/fsdev/meson.build
@@ -0,0 +1,17 @@
+fsdev_ss = ss.source_set()
+fsdev_ss.add(files('qemu-fsdev-opts.c', 'qemu-fsdev-throttle.c'))
+fsdev_ss.add(when: 'CONFIG_ALL', if_true: files('qemu-fsdev-dummy.c'))
+fsdev_ss.add(when: ['CONFIG_FSDEV_9P'], if_true: files(
+  '9p-iov-marshal.c',
+  '9p-marshal.c',
+  'qemu-fsdev.c',
+), if_false: files('qemu-fsdev-dummy.c'))
+softmmu_ss.add_all(when: 'CONFIG_LINUX', if_true: fsdev_ss)
+
+if have_virtfs_proxy_helper
+  executable('virtfs-proxy-helper',
+             files('virtfs-proxy-helper.c', '9p-marshal.c', '9p-iov-marshal.c'),
+             dependencies: [qemuutil, libattr, libcap_ng],
+             install: true,
+             install_dir: get_option('libexecdir'))
+endif
diff --git a/fsdev/p9array.h b/fsdev/p9array.h
new file mode 100644
index 000000000..6aa25327c
--- /dev/null
+++ b/fsdev/p9array.h
@@ -0,0 +1,160 @@
+/*
+ * P9Array - deep auto free C-array
+ *
+ * Copyright (c) 2021 Crudebyte
+ *
+ * Authors:
+ *   Christian Schoenebeck <qemu_oss@crudebyte.com>
+ *
+ * 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.
+ */
+#ifndef QEMU_P9ARRAY_H
+#define QEMU_P9ARRAY_H
+
+#include "qemu/compiler.h"
+
+/**
+ * P9Array provides a mechanism to access arrays in common C-style (e.g. by
+ * square bracket [] operator) in conjunction with reference variables that
+ * perform deep auto free of the array when leaving the scope of the auto
+ * reference variable. That means not only is the array itself automatically
+ * freed, but also memory dynamically allocated by the individual array
+ * elements.
+ *
+ * Example:
+ *
+ * Consider the following user struct @c Foo which shall be used as scalar
+ * (element) type of an array:
+ * @code
+ * typedef struct Foo {
+ *     int i;
+ *     char *s;
+ * } Foo;
+ * @endcode
+ * and assume it has the following function to free memory allocated by @c Foo
+ * instances:
+ * @code
+ * void free_foo(Foo *foo) {
+ *     free(foo->s);
+ * }
+ * @endcode
+ * Add the following to a shared header file:
+ * @code
+ * P9ARRAY_DECLARE_TYPE(Foo);
+ * @endcode
+ * and the following to a C unit file:
+ * @code
+ * P9ARRAY_DEFINE_TYPE(Foo, free_foo);
+ * @endcode
+ * Finally the array may then be used like this:
+ * @code
+ * void doSomething(size_t n) {
+ *     P9ARRAY_REF(Foo) foos = NULL;
+ *     P9ARRAY_NEW(Foo, foos, n);
+ *     for (size_t i = 0; i < n; ++i) {
+ *         foos[i].i = i;
+ *         foos[i].s = calloc(4096, 1);
+ *         snprintf(foos[i].s, 4096, "foo %d", i);
+ *         if (...) {
+ *             return; // array auto freed here
+ *         }
+ *     }
+ *     // array auto freed here
+ * }
+ * @endcode
+ */
+
+/**
+ * Declares an array type for the passed @a scalar_type.
+ *
+ * This is typically used from a shared header file.
+ *
+ * @param scalar_type - type of the individual array elements
+ */
+#define P9ARRAY_DECLARE_TYPE(scalar_type) \
+    typedef struct P9Array##scalar_type { \
+        size_t len; \
+        scalar_type first[]; \
+    } P9Array##scalar_type; \
+    \
+    void p9array_new_##scalar_type(scalar_type **auto_var, size_t len); \
+    void p9array_auto_free_##scalar_type(scalar_type **auto_var); \
+
+/**
+ * Defines an array type for the passed @a scalar_type and appropriate
+ * @a scalar_cleanup_func.
+ *
+ * This is typically used from a C unit file.
+ *
+ * @param scalar_type - type of the individual array elements
+ * @param scalar_cleanup_func - appropriate function to free memory dynamically
+ *                              allocated by individual array elements before
+ */
+#define P9ARRAY_DEFINE_TYPE(scalar_type, scalar_cleanup_func) \
+    void p9array_new_##scalar_type(scalar_type **auto_var, size_t len) \
+    { \
+        p9array_auto_free_##scalar_type(auto_var); \
+        P9Array##scalar_type *arr = g_malloc0(sizeof(P9Array##scalar_type) + \
+            len * sizeof(scalar_type)); \
+        arr->len = len; \
+        *auto_var = &arr->first[0]; \
+    } \
+    \
+    void p9array_auto_free_##scalar_type(scalar_type **auto_var) \
+    { \
+        scalar_type *first = (*auto_var); \
+        if (!first) { \
+            return; \
+        } \
+        P9Array##scalar_type *arr = (P9Array##scalar_type *) ( \
+            ((char *)first) - offsetof(P9Array##scalar_type, first) \
+        ); \
+        for (size_t i = 0; i < arr->len; ++i) { \
+            scalar_cleanup_func(&arr->first[i]); \
+        } \
+        g_free(arr); \
+    } \
+
+/**
+ * Used to declare a reference variable (unique pointer) for an array. After
+ * leaving the scope of the reference variable, the associated array is
+ * automatically freed.
+ *
+ * @param scalar_type - type of the individual array elements
+ */
+#define P9ARRAY_REF(scalar_type) \
+    __attribute((__cleanup__(p9array_auto_free_##scalar_type))) scalar_type*
+
+/**
+ * Allocates a new array of passed @a scalar_type with @a len number of array
+ * elements and assigns the created array to the reference variable
+ * @a auto_var.
+ *
+ * @param scalar_type - type of the individual array elements
+ * @param auto_var - destination reference variable
+ * @param len - amount of array elements to be allocated immediately
+ */
+#define P9ARRAY_NEW(scalar_type, auto_var, len) \
+    QEMU_BUILD_BUG_MSG( \
+        !__builtin_types_compatible_p(scalar_type, typeof(*auto_var)), \
+        "P9Array scalar type mismatch" \
+    ); \
+    p9array_new_##scalar_type((&auto_var), len)
+
+#endif /* QEMU_P9ARRAY_H */
diff --git a/fsdev/qemu-fsdev-dummy.c b/fsdev/qemu-fsdev-dummy.c
new file mode 100644
index 000000000..8444a254b
--- /dev/null
+++ b/fsdev/qemu-fsdev-dummy.c
@@ -0,0 +1,21 @@
+/*
+ * 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Gautham R Shenoy <ego@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-fsdev.h"
+#include "qemu/config-file.h"
+
+int qemu_fsdev_add(QemuOpts *opts, Error **errp)
+{
+    return 0;
+}
diff --git a/fsdev/qemu-fsdev-opts.c b/fsdev/qemu-fsdev-opts.c
new file mode 100644
index 000000000..07a18c6e4
--- /dev/null
+++ b/fsdev/qemu-fsdev-opts.c
@@ -0,0 +1,106 @@
+/*
+ * 9p
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/config-file.h"
+#include "qemu/option.h"
+#include "qemu/module.h"
+#include "qemu/throttle-options.h"
+
+static QemuOptsList qemu_fsdev_opts = {
+    .name = "fsdev",
+    .implied_opt_name = "fsdriver",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_fsdev_opts.head),
+    .desc = {
+        {
+            .name = "fsdriver",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "path",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "security_model",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "writeout",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "readonly",
+            .type = QEMU_OPT_BOOL,
+        }, {
+            .name = "multidevs",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "socket",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "sock_fd",
+            .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "fmode",
+            .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "dmode",
+            .type = QEMU_OPT_NUMBER,
+        },
+
+        THROTTLE_OPTS,
+
+        { /*End of list */ }
+    },
+};
+
+static QemuOptsList qemu_virtfs_opts = {
+    .name = "virtfs",
+    .implied_opt_name = "fsdriver",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_virtfs_opts.head),
+    .desc = {
+        {
+            .name = "fsdriver",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "path",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "mount_tag",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "security_model",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "writeout",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "readonly",
+            .type = QEMU_OPT_BOOL,
+        }, {
+            .name = "multidevs",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "socket",
+            .type = QEMU_OPT_STRING,
+        }, {
+            .name = "sock_fd",
+            .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "fmode",
+            .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "dmode",
+            .type = QEMU_OPT_NUMBER,
+        },
+
+        { /*End of list */ }
+    },
+};
+
+static void fsdev_register_config(void)
+{
+    qemu_add_opts(&qemu_fsdev_opts);
+    qemu_add_opts(&qemu_virtfs_opts);
+}
+opts_init(fsdev_register_config);
diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c
new file mode 100644
index 000000000..5c83a1cc0
--- /dev/null
+++ b/fsdev/qemu-fsdev-throttle.c
@@ -0,0 +1,120 @@
+/*
+ * Fsdev Throttle
+ *
+ * Copyright (C) 2016 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Pradeep Jagadeesh <pradeep.jagadeesh@huawei.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.
+ *
+ * See the COPYING file in the top-level directory for details.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qemu-fsdev-throttle.h"
+#include "qemu/iov.h"
+#include "qemu/main-loop.h"
+#include "qemu/option.h"
+
+static void fsdev_throttle_read_timer_cb(void *opaque)
+{
+    FsThrottle *fst = opaque;
+    qemu_co_enter_next(&fst->throttled_reqs[false], NULL);
+}
+
+static void fsdev_throttle_write_timer_cb(void *opaque)
+{
+    FsThrottle *fst = opaque;
+    qemu_co_enter_next(&fst->throttled_reqs[true], NULL);
+}
+
+int fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp)
+{
+    throttle_config_init(&fst->cfg);
+    fst->cfg.buckets[THROTTLE_BPS_TOTAL].avg =
+        qemu_opt_get_number(opts, "throttling.bps-total", 0);
+    fst->cfg.buckets[THROTTLE_BPS_READ].avg  =
+        qemu_opt_get_number(opts, "throttling.bps-read", 0);
+    fst->cfg.buckets[THROTTLE_BPS_WRITE].avg =
+        qemu_opt_get_number(opts, "throttling.bps-write", 0);
+    fst->cfg.buckets[THROTTLE_OPS_TOTAL].avg =
+        qemu_opt_get_number(opts, "throttling.iops-total", 0);
+    fst->cfg.buckets[THROTTLE_OPS_READ].avg =
+        qemu_opt_get_number(opts, "throttling.iops-read", 0);
+    fst->cfg.buckets[THROTTLE_OPS_WRITE].avg =
+        qemu_opt_get_number(opts, "throttling.iops-write", 0);
+
+    fst->cfg.buckets[THROTTLE_BPS_TOTAL].max =
+        qemu_opt_get_number(opts, "throttling.bps-total-max", 0);
+    fst->cfg.buckets[THROTTLE_BPS_READ].max  =
+        qemu_opt_get_number(opts, "throttling.bps-read-max", 0);
+    fst->cfg.buckets[THROTTLE_BPS_WRITE].max =
+        qemu_opt_get_number(opts, "throttling.bps-write-max", 0);
+    fst->cfg.buckets[THROTTLE_OPS_TOTAL].max =
+        qemu_opt_get_number(opts, "throttling.iops-total-max", 0);
+    fst->cfg.buckets[THROTTLE_OPS_READ].max =
+        qemu_opt_get_number(opts, "throttling.iops-read-max", 0);
+    fst->cfg.buckets[THROTTLE_OPS_WRITE].max =
+        qemu_opt_get_number(opts, "throttling.iops-write-max", 0);
+
+    fst->cfg.buckets[THROTTLE_BPS_TOTAL].burst_length =
+        qemu_opt_get_number(opts, "throttling.bps-total-max-length", 1);
+    fst->cfg.buckets[THROTTLE_BPS_READ].burst_length  =
+        qemu_opt_get_number(opts, "throttling.bps-read-max-length", 1);
+    fst->cfg.buckets[THROTTLE_BPS_WRITE].burst_length =
+        qemu_opt_get_number(opts, "throttling.bps-write-max-length", 1);
+    fst->cfg.buckets[THROTTLE_OPS_TOTAL].burst_length =
+        qemu_opt_get_number(opts, "throttling.iops-total-max-length", 1);
+    fst->cfg.buckets[THROTTLE_OPS_READ].burst_length =
+        qemu_opt_get_number(opts, "throttling.iops-read-max-length", 1);
+    fst->cfg.buckets[THROTTLE_OPS_WRITE].burst_length =
+        qemu_opt_get_number(opts, "throttling.iops-write-max-length", 1);
+    fst->cfg.op_size =
+        qemu_opt_get_number(opts, "throttling.iops-size", 0);
+
+    return throttle_is_valid(&fst->cfg, errp) ? 0 : -1;
+}
+
+void fsdev_throttle_init(FsThrottle *fst)
+{
+    if (throttle_enabled(&fst->cfg)) {
+        throttle_init(&fst->ts);
+        throttle_timers_init(&fst->tt,
+                             qemu_get_aio_context(),
+                             QEMU_CLOCK_REALTIME,
+                             fsdev_throttle_read_timer_cb,
+                             fsdev_throttle_write_timer_cb,
+                             fst);
+        throttle_config(&fst->ts, QEMU_CLOCK_REALTIME, &fst->cfg);
+        qemu_co_queue_init(&fst->throttled_reqs[0]);
+        qemu_co_queue_init(&fst->throttled_reqs[1]);
+    }
+}
+
+void coroutine_fn fsdev_co_throttle_request(FsThrottle *fst, bool is_write,
+                                            struct iovec *iov, int iovcnt)
+{
+    if (throttle_enabled(&fst->cfg)) {
+        if (throttle_schedule_timer(&fst->ts, &fst->tt, is_write) ||
+            !qemu_co_queue_empty(&fst->throttled_reqs[is_write])) {
+            qemu_co_queue_wait(&fst->throttled_reqs[is_write], NULL);
+        }
+
+        throttle_account(&fst->ts, is_write, iov_size(iov, iovcnt));
+
+        if (!qemu_co_queue_empty(&fst->throttled_reqs[is_write]) &&
+            !throttle_schedule_timer(&fst->ts, &fst->tt, is_write)) {
+            qemu_co_queue_next(&fst->throttled_reqs[is_write]);
+        }
+    }
+}
+
+void fsdev_throttle_cleanup(FsThrottle *fst)
+{
+    if (throttle_enabled(&fst->cfg)) {
+        throttle_timers_destroy(&fst->tt);
+    }
+}
diff --git a/fsdev/qemu-fsdev-throttle.h b/fsdev/qemu-fsdev-throttle.h
new file mode 100644
index 000000000..a21aecddc
--- /dev/null
+++ b/fsdev/qemu-fsdev-throttle.h
@@ -0,0 +1,38 @@
+/*
+ * Fsdev Throttle
+ *
+ * Copyright (C) 2016 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Pradeep Jagadeesh <pradeep.jagadeesh@huawei.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.
+ *
+ * See the COPYING file in the top-level directory for details.
+ *
+ */
+
+#ifndef QEMU_FSDEV_THROTTLE_H
+#define QEMU_FSDEV_THROTTLE_H
+
+#include "block/aio.h"
+#include "qemu/coroutine.h"
+#include "qemu/throttle.h"
+
+typedef struct FsThrottle {
+    ThrottleState ts;
+    ThrottleTimers tt;
+    ThrottleConfig cfg;
+    CoQueue      throttled_reqs[2];
+} FsThrottle;
+
+int fsdev_throttle_parse_opts(QemuOpts *, FsThrottle *, Error **);
+
+void fsdev_throttle_init(FsThrottle *);
+
+void coroutine_fn fsdev_co_throttle_request(FsThrottle *, bool ,
+                                            struct iovec *, int);
+
+void fsdev_throttle_cleanup(FsThrottle *);
+
+#endif /* QEMU_FSDEV_THROTTLE_H */
diff --git a/fsdev/qemu-fsdev.c b/fsdev/qemu-fsdev.c
new file mode 100644
index 000000000..3da64e9f7
--- /dev/null
+++ b/fsdev/qemu-fsdev.c
@@ -0,0 +1,193 @@
+/*
+ * 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Gautham R Shenoy <ego@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu-fsdev.h"
+#include "qemu/queue.h"
+#include "qemu/config-file.h"
+#include "qemu/error-report.h"
+#include "qemu/option.h"
+
+/*
+ * A table to store the various file systems and their callback operations.
+ * -----------------
+ * fstype | ops
+ * -----------------
+ *  local | local_ops
+ *  .     |
+ *  .     |
+ *  .     |
+ *  .     |
+ * -----------------
+ *  etc
+ */
+typedef struct FsDriverTable {
+    const char *name;
+    FileOperations *ops;
+    const char **opts;
+} FsDriverTable;
+
+typedef struct FsDriverListEntry {
+    FsDriverEntry fse;
+    QTAILQ_ENTRY(FsDriverListEntry) next;
+} FsDriverListEntry;
+
+static QTAILQ_HEAD(, FsDriverListEntry) fsdriver_entries =
+    QTAILQ_HEAD_INITIALIZER(fsdriver_entries);
+
+#define COMMON_FS_DRIVER_OPTIONS "id", "fsdriver", "readonly"
+
+static FsDriverTable FsDrivers[] = {
+    {
+        .name = "local",
+        .ops = &local_ops,
+        .opts = (const char * []) {
+            COMMON_FS_DRIVER_OPTIONS,
+            "security_model",
+            "path",
+            "writeout",
+            "fmode",
+            "dmode",
+            "multidevs",
+            "throttling.bps-total",
+            "throttling.bps-read",
+            "throttling.bps-write",
+            "throttling.iops-total",
+            "throttling.iops-read",
+            "throttling.iops-write",
+            "throttling.bps-total-max",
+            "throttling.bps-read-max",
+            "throttling.bps-write-max",
+            "throttling.iops-total-max",
+            "throttling.iops-read-max",
+            "throttling.iops-write-max",
+            "throttling.bps-total-max-length",
+            "throttling.bps-read-max-length",
+            "throttling.bps-write-max-length",
+            "throttling.iops-total-max-length",
+            "throttling.iops-read-max-length",
+            "throttling.iops-write-max-length",
+            "throttling.iops-size",
+            NULL
+        },
+    },
+    {
+        .name = "synth",
+        .ops = &synth_ops,
+        .opts = (const char * []) {
+            COMMON_FS_DRIVER_OPTIONS,
+            NULL
+        },
+    },
+    {
+        .name = "proxy",
+        .ops = &proxy_ops,
+        .opts = (const char * []) {
+            COMMON_FS_DRIVER_OPTIONS,
+            "socket",
+            "sock_fd",
+            "writeout",
+            NULL
+        },
+    },
+};
+
+static int validate_opt(void *opaque, const char *name, const char *value,
+                        Error **errp)
+{
+    FsDriverTable *drv = opaque;
+    const char **opt;
+
+    for (opt = drv->opts; *opt; opt++) {
+        if (!strcmp(*opt, name)) {
+            return 0;
+        }
+    }
+
+    error_setg(errp, "'%s' is invalid for fsdriver '%s'", name, drv->name);
+    return -1;
+}
+
+int qemu_fsdev_add(QemuOpts *opts, Error **errp)
+{
+    int i;
+    struct FsDriverListEntry *fsle;
+    const char *fsdev_id = qemu_opts_id(opts);
+    const char *fsdriver = qemu_opt_get(opts, "fsdriver");
+    const char *writeout = qemu_opt_get(opts, "writeout");
+    bool ro = qemu_opt_get_bool(opts, "readonly", 0);
+
+    if (!fsdev_id) {
+        error_setg(errp, "fsdev: No id specified");
+        return -1;
+    }
+
+    if (fsdriver) {
+        for (i = 0; i < ARRAY_SIZE(FsDrivers); i++) {
+            if (strcmp(FsDrivers[i].name, fsdriver) == 0) {
+                break;
+            }
+        }
+
+        if (i == ARRAY_SIZE(FsDrivers)) {
+            error_setg(errp, "fsdev: fsdriver %s not found", fsdriver);
+            return -1;
+        }
+    } else {
+        error_setg(errp, "fsdev: No fsdriver specified");
+        return -1;
+    }
+
+    if (qemu_opt_foreach(opts, validate_opt, &FsDrivers[i], errp)) {
+        return -1;
+    }
+
+    fsle = g_malloc0(sizeof(*fsle));
+    fsle->fse.fsdev_id = g_strdup(fsdev_id);
+    fsle->fse.ops = FsDrivers[i].ops;
+    if (writeout) {
+        if (!strcmp(writeout, "immediate")) {
+            fsle->fse.export_flags |= V9FS_IMMEDIATE_WRITEOUT;
+        }
+    }
+    if (ro) {
+        fsle->fse.export_flags |= V9FS_RDONLY;
+    } else {
+        fsle->fse.export_flags &= ~V9FS_RDONLY;
+    }
+
+    if (fsle->fse.ops->parse_opts) {
+        if (fsle->fse.ops->parse_opts(opts, &fsle->fse, errp)) {
+            g_free(fsle->fse.fsdev_id);
+            g_free(fsle);
+            return -1;
+        }
+    }
+
+    QTAILQ_INSERT_TAIL(&fsdriver_entries, fsle, next);
+    return 0;
+}
+
+FsDriverEntry *get_fsdev_fsentry(char *id)
+{
+    if (id) {
+        struct FsDriverListEntry *fsle;
+
+        QTAILQ_FOREACH(fsle, &fsdriver_entries, next) {
+            if (strcmp(fsle->fse.fsdev_id, id) == 0) {
+                return &fsle->fse;
+            }
+        }
+    }
+    return NULL;
+}
diff --git a/fsdev/qemu-fsdev.h b/fsdev/qemu-fsdev.h
new file mode 100644
index 000000000..52a539777
--- /dev/null
+++ b/fsdev/qemu-fsdev.h
@@ -0,0 +1,22 @@
+/*
+ * 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Gautham R Shenoy <ego@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef QEMU_FSDEV_H
+#define QEMU_FSDEV_H
+#include "file-op-9p.h"
+
+int qemu_fsdev_add(QemuOpts *opts, Error **errp);
+FsDriverEntry *get_fsdev_fsentry(char *id);
+extern FileOperations local_ops;
+extern FileOperations synth_ops;
+extern FileOperations proxy_ops;
+#endif
diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c
new file mode 100644
index 000000000..15c0e79b0
--- /dev/null
+++ b/fsdev/virtfs-proxy-helper.c
@@ -0,0 +1,1161 @@
+/*
+ * Helper for QEMU Proxy FS Driver
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ * M. Mohan Kumar <mohan@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include <sys/resource.h>
+#include <getopt.h>
+#include <syslog.h>
+#include <sys/fsuid.h>
+#include <sys/vfs.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+#ifdef CONFIG_LINUX_MAGIC_H
+#include <linux/magic.h>
+#endif
+#include <cap-ng.h>
+#include "qemu-common.h"
+#include "qemu/sockets.h"
+#include "qemu/xattr.h"
+#include "9p-iov-marshal.h"
+#include "hw/9pfs/9p-proxy.h"
+#include "fsdev/9p-iov-marshal.h"
+
+#define PROGNAME "virtfs-proxy-helper"
+
+#ifndef XFS_SUPER_MAGIC
+#define XFS_SUPER_MAGIC  0x58465342
+#endif
+#ifndef EXT2_SUPER_MAGIC
+#define EXT2_SUPER_MAGIC 0xEF53
+#endif
+#ifndef REISERFS_SUPER_MAGIC
+#define REISERFS_SUPER_MAGIC 0x52654973
+#endif
+#ifndef BTRFS_SUPER_MAGIC
+#define BTRFS_SUPER_MAGIC 0x9123683E
+#endif
+
+static const struct option helper_opts[] = {
+    {"fd", required_argument, NULL, 'f'},
+    {"path", required_argument, NULL, 'p'},
+    {"nodaemon", no_argument, NULL, 'n'},
+    {"socket", required_argument, NULL, 's'},
+    {"uid", required_argument, NULL, 'u'},
+    {"gid", required_argument, NULL, 'g'},
+    {},
+};
+
+static bool is_daemon;
+static bool get_version; /* IOC getversion IOCTL supported */
+static char *prog_name;
+
+static void GCC_FMT_ATTR(2, 3) do_log(int loglevel, const char *format, ...)
+{
+    va_list ap;
+
+    va_start(ap, format);
+    if (is_daemon) {
+        vsyslog(LOG_CRIT, format, ap);
+    } else {
+        vfprintf(stderr, format, ap);
+    }
+    va_end(ap);
+}
+
+static void do_perror(const char *string)
+{
+    if (is_daemon) {
+        syslog(LOG_CRIT, "%s:%s", string, strerror(errno));
+    } else {
+        fprintf(stderr, "%s:%s\n", string, strerror(errno));
+    }
+}
+
+static int init_capabilities(void)
+{
+    /* helper needs following capabilities only */
+    int cap_list[] = {
+        CAP_CHOWN,
+        CAP_DAC_OVERRIDE,
+        CAP_FOWNER,
+        CAP_FSETID,
+        CAP_SETGID,
+        CAP_MKNOD,
+        CAP_SETUID,
+    };
+    int i;
+
+    capng_clear(CAPNG_SELECT_BOTH);
+    for (i = 0; i < ARRAY_SIZE(cap_list); i++) {
+        if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
+                         cap_list[i]) < 0) {
+            do_perror("capng_update");
+            return -1;
+        }
+    }
+    if (capng_apply(CAPNG_SELECT_BOTH) < 0) {
+        do_perror("capng_apply");
+        return -1;
+    }
+
+    /* Prepare effective set for setugid.  */
+    for (i = 0; i < ARRAY_SIZE(cap_list); i++) {
+        if (cap_list[i] == CAP_DAC_OVERRIDE) {
+            continue;
+        }
+
+        if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE,
+                         cap_list[i]) < 0) {
+            do_perror("capng_update");
+            return -1;
+        }
+    }
+    return 0;
+}
+
+static int socket_read(int sockfd, void *buff, ssize_t size)
+{
+    ssize_t retval, total = 0;
+
+    while (size) {
+        retval = read(sockfd, buff, size);
+        if (retval == 0) {
+            return -EIO;
+        }
+        if (retval < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            return -errno;
+        }
+        size -= retval;
+        buff += retval;
+        total += retval;
+    }
+    return total;
+}
+
+static int socket_write(int sockfd, void *buff, ssize_t size)
+{
+    ssize_t retval, total = 0;
+
+    while (size) {
+        retval = write(sockfd, buff, size);
+        if (retval < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            return -errno;
+        }
+        size -= retval;
+        buff += retval;
+        total += retval;
+    }
+    return total;
+}
+
+static int read_request(int sockfd, struct iovec *iovec, ProxyHeader *header)
+{
+    int retval;
+
+    /*
+     * read the request header.
+     */
+    iovec->iov_len = 0;
+    retval = socket_read(sockfd, iovec->iov_base, PROXY_HDR_SZ);
+    if (retval < 0) {
+        return retval;
+    }
+    iovec->iov_len = PROXY_HDR_SZ;
+    retval = proxy_unmarshal(iovec, 0, "dd", &header->type, &header->size);
+    if (retval < 0) {
+        return retval;
+    }
+    /*
+     * We can't process message.size > PROXY_MAX_IO_SZ.
+     * Treat it as fatal error
+     */
+    if (header->size > PROXY_MAX_IO_SZ) {
+        return -ENOBUFS;
+    }
+    retval = socket_read(sockfd, iovec->iov_base + PROXY_HDR_SZ, header->size);
+    if (retval < 0) {
+        return retval;
+    }
+    iovec->iov_len += header->size;
+    return 0;
+}
+
+static int send_fd(int sockfd, int fd)
+{
+    struct msghdr msg;
+    struct iovec iov;
+    int retval, data;
+    struct cmsghdr *cmsg;
+    union MsgControl msg_control;
+
+    iov.iov_base = &data;
+    iov.iov_len = sizeof(data);
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+    /* No ancillary data on error */
+    if (fd < 0) {
+        /* fd is really negative errno if the request failed  */
+        data = fd;
+    } else {
+        data = V9FS_FD_VALID;
+        msg.msg_control = &msg_control;
+        msg.msg_controllen = sizeof(msg_control);
+
+        cmsg = &msg_control.cmsg;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+    }
+
+    do {
+        retval = sendmsg(sockfd, &msg, 0);
+    } while (retval < 0 && errno == EINTR);
+    if (fd >= 0) {
+        close(fd);
+    }
+    if (retval < 0) {
+        return retval;
+    }
+    return 0;
+}
+
+static int send_status(int sockfd, struct iovec *iovec, int status)
+{
+    ProxyHeader header;
+    int retval, msg_size;
+
+    if (status < 0) {
+        header.type = T_ERROR;
+    } else {
+        header.type = T_SUCCESS;
+    }
+    header.size = sizeof(status);
+    /*
+     * marshal the return status. We don't check error.
+     * because we are sure we have enough space for the status
+     */
+    msg_size = proxy_marshal(iovec, 0, "ddd", header.type,
+                             header.size, status);
+    if (msg_size < 0) {
+        return msg_size;
+    }
+    retval = socket_write(sockfd, iovec->iov_base, msg_size);
+    if (retval < 0) {
+        return retval;
+    }
+    return 0;
+}
+
+/*
+ * from man 7 capabilities, section
+ * Effect of User ID Changes on Capabilities:
+ * If the effective user ID is changed from nonzero to 0, then the permitted
+ * set is copied to the effective set.  If the effective user ID is changed
+ * from 0 to nonzero, then all capabilities are are cleared from the effective
+ * set.
+ *
+ * The setfsuid/setfsgid man pages warn that changing the effective user ID may
+ * expose the program to unwanted signals, but this is not true anymore: for an
+ * unprivileged (without CAP_KILL) program to send a signal, the real or
+ * effective user ID of the sending process must equal the real or saved user
+ * ID of the target process.  Even when dropping privileges, it is enough to
+ * keep the saved UID to a "privileged" value and virtfs-proxy-helper won't
+ * be exposed to signals.  So just use setresuid/setresgid.
+ */
+static int setugid(int uid, int gid, int *suid, int *sgid)
+{
+    int retval;
+
+    *suid = geteuid();
+    *sgid = getegid();
+
+    if (setresgid(-1, gid, *sgid) == -1) {
+        return -errno;
+    }
+
+    if (setresuid(-1, uid, *suid) == -1) {
+        retval = -errno;
+        goto err_sgid;
+    }
+
+    if (uid == 0 && gid == 0) {
+        /* Linux has already copied the permitted set to the effective set.  */
+        return 0;
+    }
+
+    /*
+     * All capabilities have been cleared from the effective set.  However
+     * we still need DAC_OVERRIDE because we don't change supplementary
+     * group ids, and hence may be subject to DAC rules.  init_capabilities
+     * left the set of capabilities that we want in libcap-ng's state.
+     */
+    if (capng_apply(CAPNG_SELECT_CAPS) < 0) {
+        retval = -errno;
+        do_perror("capng_apply");
+        goto err_suid;
+    }
+    return 0;
+
+err_suid:
+    if (setresuid(-1, *suid, *suid) == -1) {
+        abort();
+    }
+err_sgid:
+    if (setresgid(-1, *sgid, *sgid) == -1) {
+        abort();
+    }
+    return retval;
+}
+
+/*
+ * This is used to reset the ugid back with the saved values
+ * There is nothing much we can do checking error values here.
+ */
+static void resetugid(int suid, int sgid)
+{
+    if (setresgid(-1, sgid, sgid) == -1) {
+        abort();
+    }
+    if (setresuid(-1, suid, suid) == -1) {
+        abort();
+    }
+}
+
+/*
+ * send response in two parts
+ * 1) ProxyHeader
+ * 2) Response or error status
+ * This function should be called with marshaled response
+ * send_response constructs header part and error part only.
+ * send response sends {ProxyHeader,Response} if the request was success
+ * otherwise sends {ProxyHeader,error status}
+ */
+static int send_response(int sock, struct iovec *iovec, int size)
+{
+    int retval;
+    ProxyHeader header;
+
+    /*
+     * If response size exceeds available iovec->iov_len,
+     * we return ENOBUFS
+     */
+    if (size > PROXY_MAX_IO_SZ) {
+        size = -ENOBUFS;
+    }
+
+    if (size < 0) {
+        /*
+         * In case of error we would not have got the error encoded
+         * already so encode the error here.
+         */
+        header.type = T_ERROR;
+        header.size = sizeof(size);
+        proxy_marshal(iovec, PROXY_HDR_SZ, "d", size);
+    } else {
+        header.type = T_SUCCESS;
+        header.size = size;
+    }
+    proxy_marshal(iovec, 0, "dd", header.type, header.size);
+    retval = socket_write(sock, iovec->iov_base, header.size + PROXY_HDR_SZ);
+    if (retval < 0) {
+        return retval;
+    }
+    return 0;
+}
+
+/*
+ * gets generation number
+ * returns -errno on failure and sizeof(generation number) on success
+ */
+static int do_getversion(struct iovec *iovec, struct iovec *out_iovec)
+{
+    uint64_t version;
+    int retval = -ENOTTY;
+#ifdef FS_IOC_GETVERSION
+    int fd;
+    V9fsString path;
+#endif
+
+
+    /* no need to issue ioctl */
+    if (!get_version) {
+        version = 0;
+        retval = proxy_marshal(out_iovec, PROXY_HDR_SZ, "q", version);
+        return retval;
+    }
+#ifdef FS_IOC_GETVERSION
+    retval = proxy_unmarshal(iovec, PROXY_HDR_SZ, "s", &path);
+    if (retval < 0) {
+        return retval;
+    }
+
+    fd = open(path.data, O_RDONLY);
+    if (fd < 0) {
+        retval = -errno;
+        goto err_out;
+    }
+    if (ioctl(fd, FS_IOC_GETVERSION, &version) < 0) {
+        retval = -errno;
+    } else {
+        retval = proxy_marshal(out_iovec, PROXY_HDR_SZ, "q", version);
+    }
+    close(fd);
+err_out:
+    v9fs_string_free(&path);
+#endif
+    return retval;
+}
+
+static int do_getxattr(int type, struct iovec *iovec, struct iovec *out_iovec)
+{
+    int size = 0, offset, retval;
+    V9fsString path, name, xattr;
+
+    v9fs_string_init(&xattr);
+    v9fs_string_init(&path);
+    retval = proxy_unmarshal(iovec, PROXY_HDR_SZ, "ds", &size, &path);
+    if (retval < 0) {
+        return retval;
+    }
+    offset = PROXY_HDR_SZ + retval;
+
+    if (size) {
+        xattr.data = g_malloc(size);
+        xattr.size = size;
+    }
+    switch (type) {
+    case T_LGETXATTR:
+        v9fs_string_init(&name);
+        retval = proxy_unmarshal(iovec, offset, "s", &name);
+        if (retval > 0) {
+            retval = lgetxattr(path.data, name.data, xattr.data, size);
+            if (retval < 0) {
+                retval = -errno;
+            } else {
+                xattr.size = retval;
+            }
+        }
+        v9fs_string_free(&name);
+        break;
+    case T_LLISTXATTR:
+        retval = llistxattr(path.data, xattr.data, size);
+        if (retval < 0) {
+            retval = -errno;
+        } else {
+            xattr.size = retval;
+        }
+        break;
+    }
+    if (retval < 0) {
+        goto err_out;
+    }
+
+    if (!size) {
+        proxy_marshal(out_iovec, PROXY_HDR_SZ, "d", retval);
+        retval = sizeof(retval);
+    } else {
+        retval = proxy_marshal(out_iovec, PROXY_HDR_SZ, "s", &xattr);
+    }
+err_out:
+    v9fs_string_free(&xattr);
+    v9fs_string_free(&path);
+    return retval;
+}
+
+static void stat_to_prstat(ProxyStat *pr_stat, struct stat *stat)
+{
+    memset(pr_stat, 0, sizeof(*pr_stat));
+    pr_stat->st_dev = stat->st_dev;
+    pr_stat->st_ino = stat->st_ino;
+    pr_stat->st_nlink = stat->st_nlink;
+    pr_stat->st_mode = stat->st_mode;
+    pr_stat->st_uid = stat->st_uid;
+    pr_stat->st_gid = stat->st_gid;
+    pr_stat->st_rdev = stat->st_rdev;
+    pr_stat->st_size = stat->st_size;
+    pr_stat->st_blksize = stat->st_blksize;
+    pr_stat->st_blocks = stat->st_blocks;
+    pr_stat->st_atim_sec = stat->st_atim.tv_sec;
+    pr_stat->st_atim_nsec = stat->st_atim.tv_nsec;
+    pr_stat->st_mtim_sec = stat->st_mtim.tv_sec;
+    pr_stat->st_mtim_nsec = stat->st_mtim.tv_nsec;
+    pr_stat->st_ctim_sec = stat->st_ctim.tv_sec;
+    pr_stat->st_ctim_nsec = stat->st_ctim.tv_nsec;
+}
+
+static void statfs_to_prstatfs(ProxyStatFS *pr_stfs, struct statfs *stfs)
+{
+    memset(pr_stfs, 0, sizeof(*pr_stfs));
+    pr_stfs->f_type = stfs->f_type;
+    pr_stfs->f_bsize = stfs->f_bsize;
+    pr_stfs->f_blocks = stfs->f_blocks;
+    pr_stfs->f_bfree = stfs->f_bfree;
+    pr_stfs->f_bavail = stfs->f_bavail;
+    pr_stfs->f_files = stfs->f_files;
+    pr_stfs->f_ffree = stfs->f_ffree;
+    pr_stfs->f_fsid[0] = stfs->f_fsid.__val[0];
+    pr_stfs->f_fsid[1] = stfs->f_fsid.__val[1];
+    pr_stfs->f_namelen = stfs->f_namelen;
+    pr_stfs->f_frsize = stfs->f_frsize;
+}
+
+/*
+ * Gets stat/statfs information and packs in out_iovec structure
+ * on success returns number of bytes packed in out_iovec structure
+ * otherwise returns -errno
+ */
+static int do_stat(int type, struct iovec *iovec, struct iovec *out_iovec)
+{
+    int retval;
+    V9fsString path;
+    ProxyStat pr_stat;
+    ProxyStatFS pr_stfs;
+    struct stat st_buf;
+    struct statfs stfs_buf;
+
+    v9fs_string_init(&path);
+    retval = proxy_unmarshal(iovec, PROXY_HDR_SZ, "s", &path);
+    if (retval < 0) {
+        return retval;
+    }
+
+    switch (type) {
+    case T_LSTAT:
+        retval = lstat(path.data, &st_buf);
+        if (retval < 0) {
+            retval = -errno;
+        } else {
+            stat_to_prstat(&pr_stat, &st_buf);
+            retval = proxy_marshal(out_iovec, PROXY_HDR_SZ,
+                                   "qqqdddqqqqqqqqqq", pr_stat.st_dev,
+                                   pr_stat.st_ino, pr_stat.st_nlink,
+                                   pr_stat.st_mode, pr_stat.st_uid,
+                                   pr_stat.st_gid, pr_stat.st_rdev,
+                                   pr_stat.st_size, pr_stat.st_blksize,
+                                   pr_stat.st_blocks,
+                                   pr_stat.st_atim_sec, pr_stat.st_atim_nsec,
+                                   pr_stat.st_mtim_sec, pr_stat.st_mtim_nsec,
+                                   pr_stat.st_ctim_sec, pr_stat.st_ctim_nsec);
+        }
+        break;
+    case T_STATFS:
+        retval = statfs(path.data, &stfs_buf);
+        if (retval < 0) {
+            retval = -errno;
+        } else {
+            statfs_to_prstatfs(&pr_stfs, &stfs_buf);
+            retval = proxy_marshal(out_iovec, PROXY_HDR_SZ,
+                                   "qqqqqqqqqqq", pr_stfs.f_type,
+                                   pr_stfs.f_bsize, pr_stfs.f_blocks,
+                                   pr_stfs.f_bfree, pr_stfs.f_bavail,
+                                   pr_stfs.f_files, pr_stfs.f_ffree,
+                                   pr_stfs.f_fsid[0], pr_stfs.f_fsid[1],
+                                   pr_stfs.f_namelen, pr_stfs.f_frsize);
+        }
+        break;
+    }
+    v9fs_string_free(&path);
+    return retval;
+}
+
+static int do_readlink(struct iovec *iovec, struct iovec *out_iovec)
+{
+    char *buffer;
+    int size, retval;
+    V9fsString target, path;
+
+    v9fs_string_init(&path);
+    retval = proxy_unmarshal(iovec, PROXY_HDR_SZ, "sd", &path, &size);
+    if (retval < 0) {
+        v9fs_string_free(&path);
+        return retval;
+    }
+    buffer = g_malloc(size);
+    v9fs_string_init(&target);
+    retval = readlink(path.data, buffer, size - 1);
+    if (retval > 0) {
+        buffer[retval] = '\0';
+        v9fs_string_sprintf(&target, "%s", buffer);
+        retval = proxy_marshal(out_iovec, PROXY_HDR_SZ, "s", &target);
+    } else {
+        retval = -errno;
+    }
+    g_free(buffer);
+    v9fs_string_free(&target);
+    v9fs_string_free(&path);
+    return retval;
+}
+
+/*
+ * create other filesystem objects and send 0 on success
+ * return -errno on error
+ */
+static int do_create_others(int type, struct iovec *iovec)
+{
+    dev_t rdev;
+    int retval = 0;
+    int offset = PROXY_HDR_SZ;
+    V9fsString oldpath, path;
+    int mode, uid, gid, cur_uid, cur_gid;
+
+    v9fs_string_init(&path);
+    v9fs_string_init(&oldpath);
+
+    retval = proxy_unmarshal(iovec, offset, "dd", &uid, &gid);
+    if (retval < 0) {
+        return retval;
+    }
+    offset += retval;
+    retval = setugid(uid, gid, &cur_uid, &cur_gid);
+    if (retval < 0) {
+        goto unmarshal_err_out;
+    }
+    switch (type) {
+    case T_MKNOD:
+        retval = proxy_unmarshal(iovec, offset, "sdq", &path, &mode, &rdev);
+        if (retval < 0) {
+            goto err_out;
+        }
+        retval = mknod(path.data, mode, rdev);
+        break;
+    case T_MKDIR:
+        retval = proxy_unmarshal(iovec, offset, "sd", &path, &mode);
+        if (retval < 0) {
+            goto err_out;
+        }
+        retval = mkdir(path.data, mode);
+        break;
+    case T_SYMLINK:
+        retval = proxy_unmarshal(iovec, offset, "ss", &oldpath, &path);
+        if (retval < 0) {
+            goto err_out;
+        }
+        retval = symlink(oldpath.data, path.data);
+        break;
+    }
+    if (retval < 0) {
+        retval = -errno;
+    }
+
+err_out:
+    resetugid(cur_uid, cur_gid);
+unmarshal_err_out:
+    v9fs_string_free(&path);
+    v9fs_string_free(&oldpath);
+    return retval;
+}
+
+/*
+ * create a file and send fd on success
+ * return -errno on error
+ */
+static int do_create(struct iovec *iovec)
+{
+    int ret;
+    V9fsString path;
+    int flags, mode, uid, gid, cur_uid, cur_gid;
+
+    v9fs_string_init(&path);
+    ret = proxy_unmarshal(iovec, PROXY_HDR_SZ, "sdddd",
+                          &path, &flags, &mode, &uid, &gid);
+    if (ret < 0) {
+        goto unmarshal_err_out;
+    }
+    ret = setugid(uid, gid, &cur_uid, &cur_gid);
+    if (ret < 0) {
+        goto unmarshal_err_out;
+    }
+    ret = open(path.data, flags, mode);
+    if (ret < 0) {
+        ret = -errno;
+    }
+
+    resetugid(cur_uid, cur_gid);
+unmarshal_err_out:
+    v9fs_string_free(&path);
+    return ret;
+}
+
+/*
+ * open a file and send fd on success
+ * return -errno on error
+ */
+static int do_open(struct iovec *iovec)
+{
+    int flags, ret;
+    V9fsString path;
+
+    v9fs_string_init(&path);
+    ret = proxy_unmarshal(iovec, PROXY_HDR_SZ, "sd", &path, &flags);
+    if (ret < 0) {
+        goto err_out;
+    }
+    ret = open(path.data, flags);
+    if (ret < 0) {
+        ret = -errno;
+    }
+err_out:
+    v9fs_string_free(&path);
+    return ret;
+}
+
+/* create unix domain socket and return the descriptor */
+static int proxy_socket(const char *path, uid_t uid, gid_t gid)
+{
+    int sock, client;
+    struct sockaddr_un proxy, qemu;
+    socklen_t size;
+
+    /* requested socket already exists, refuse to start */
+    if (!access(path, F_OK)) {
+        do_log(LOG_CRIT, "socket already exists\n");
+        return -1;
+    }
+
+    if (strlen(path) >= sizeof(proxy.sun_path)) {
+        do_log(LOG_CRIT, "UNIX domain socket path exceeds %zu characters\n",
+               sizeof(proxy.sun_path));
+        return -1;
+    }
+
+    sock = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sock < 0) {
+        do_perror("socket");
+        return -1;
+    }
+
+    /* mask other part of mode bits */
+    umask(7);
+
+    proxy.sun_family = AF_UNIX;
+    strcpy(proxy.sun_path, path);
+    if (bind(sock, (struct sockaddr *)&proxy,
+            sizeof(struct sockaddr_un)) < 0) {
+        do_perror("bind");
+        goto error;
+    }
+    if (chown(proxy.sun_path, uid, gid) < 0) {
+        do_perror("chown");
+        goto error;
+    }
+    if (listen(sock, 1) < 0) {
+        do_perror("listen");
+        goto error;
+    }
+
+    size = sizeof(qemu);
+    client = accept(sock, (struct sockaddr *)&qemu, &size);
+    if (client < 0) {
+        do_perror("accept");
+        goto error;
+    }
+    close(sock);
+    return client;
+
+error:
+    close(sock);
+    return -1;
+}
+
+static void usage(void)
+{
+    fprintf(stderr, "usage: %s\n"
+            " -p|--path <path> 9p path to export\n"
+            " {-f|--fd <socket-descriptor>} socket file descriptor to be used\n"
+            " {-s|--socket <socketname> socket file used for communication\n"
+            " \t-u|--uid <uid> -g|--gid <gid>} - uid:gid combination to give "
+            " access to this socket\n"
+            " \tNote: -s & -f can not be used together\n"
+            " [-n|--nodaemon] Run as a normal program\n",
+            prog_name);
+}
+
+static int process_reply(int sock, int type,
+                         struct iovec *out_iovec, int retval)
+{
+    switch (type) {
+    case T_OPEN:
+    case T_CREATE:
+        if (send_fd(sock, retval) < 0) {
+            return -1;
+        }
+        break;
+    case T_MKNOD:
+    case T_MKDIR:
+    case T_SYMLINK:
+    case T_LINK:
+    case T_CHMOD:
+    case T_CHOWN:
+    case T_TRUNCATE:
+    case T_UTIME:
+    case T_RENAME:
+    case T_REMOVE:
+    case T_LSETXATTR:
+    case T_LREMOVEXATTR:
+        if (send_status(sock, out_iovec, retval) < 0) {
+            return -1;
+        }
+        break;
+    case T_LSTAT:
+    case T_STATFS:
+    case T_READLINK:
+    case T_LGETXATTR:
+    case T_LLISTXATTR:
+    case T_GETVERSION:
+        if (send_response(sock, out_iovec, retval) < 0) {
+            return -1;
+        }
+        break;
+    default:
+        return -1;
+        break;
+    }
+    return 0;
+}
+
+static int process_requests(int sock)
+{
+    int flags;
+    int size = 0;
+    int retval = 0;
+    uint64_t offset;
+    ProxyHeader header;
+    int mode, uid, gid;
+    V9fsString name, value;
+    struct timespec spec[2];
+    V9fsString oldpath, path;
+    struct iovec in_iovec, out_iovec;
+
+    in_iovec.iov_base  = g_malloc(PROXY_MAX_IO_SZ + PROXY_HDR_SZ);
+    in_iovec.iov_len   = PROXY_MAX_IO_SZ + PROXY_HDR_SZ;
+    out_iovec.iov_base = g_malloc(PROXY_MAX_IO_SZ + PROXY_HDR_SZ);
+    out_iovec.iov_len  = PROXY_MAX_IO_SZ + PROXY_HDR_SZ;
+
+    while (1) {
+        /*
+         * initialize the header type, so that we send
+         * response to proper request type.
+         */
+        header.type = 0;
+        retval = read_request(sock, &in_iovec, &header);
+        if (retval < 0) {
+            goto err_out;
+        }
+
+        switch (header.type) {
+        case T_OPEN:
+            retval = do_open(&in_iovec);
+            break;
+        case T_CREATE:
+            retval = do_create(&in_iovec);
+            break;
+        case T_MKNOD:
+        case T_MKDIR:
+        case T_SYMLINK:
+            retval = do_create_others(header.type, &in_iovec);
+            break;
+        case T_LINK:
+            v9fs_string_init(&path);
+            v9fs_string_init(&oldpath);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ,
+                                     "ss", &oldpath, &path);
+            if (retval > 0) {
+                retval = link(oldpath.data, path.data);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&oldpath);
+            v9fs_string_free(&path);
+            break;
+        case T_LSTAT:
+        case T_STATFS:
+            retval = do_stat(header.type, &in_iovec, &out_iovec);
+            break;
+        case T_READLINK:
+            retval = do_readlink(&in_iovec, &out_iovec);
+            break;
+        case T_CHMOD:
+            v9fs_string_init(&path);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ,
+                                     "sd", &path, &mode);
+            if (retval > 0) {
+                retval = chmod(path.data, mode);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            break;
+        case T_CHOWN:
+            v9fs_string_init(&path);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ, "sdd", &path,
+                                     &uid, &gid);
+            if (retval > 0) {
+                retval = lchown(path.data, uid, gid);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            break;
+        case T_TRUNCATE:
+            v9fs_string_init(&path);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ, "sq",
+                                     &path, &offset);
+            if (retval > 0) {
+                retval = truncate(path.data, offset);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            break;
+        case T_UTIME:
+            v9fs_string_init(&path);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ, "sqqqq", &path,
+                                     &spec[0].tv_sec, &spec[0].tv_nsec,
+                                     &spec[1].tv_sec, &spec[1].tv_nsec);
+            if (retval > 0) {
+                retval = utimensat(AT_FDCWD, path.data, spec,
+                                   AT_SYMLINK_NOFOLLOW);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            break;
+        case T_RENAME:
+            v9fs_string_init(&path);
+            v9fs_string_init(&oldpath);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ,
+                                     "ss", &oldpath, &path);
+            if (retval > 0) {
+                retval = rename(oldpath.data, path.data);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&oldpath);
+            v9fs_string_free(&path);
+            break;
+        case T_REMOVE:
+            v9fs_string_init(&path);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ, "s", &path);
+            if (retval > 0) {
+                retval = remove(path.data);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            break;
+        case T_LGETXATTR:
+        case T_LLISTXATTR:
+            retval = do_getxattr(header.type, &in_iovec, &out_iovec);
+            break;
+        case T_LSETXATTR:
+            v9fs_string_init(&path);
+            v9fs_string_init(&name);
+            v9fs_string_init(&value);
+            retval = proxy_unmarshal(&in_iovec, PROXY_HDR_SZ, "sssdd", &path,
+                                     &name, &value, &size, &flags);
+            if (retval > 0) {
+                retval = lsetxattr(path.data,
+                                   name.data, value.data, size, flags);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            v9fs_string_free(&name);
+            v9fs_string_free(&value);
+            break;
+        case T_LREMOVEXATTR:
+            v9fs_string_init(&path);
+            v9fs_string_init(&name);
+            retval = proxy_unmarshal(&in_iovec,
+                                     PROXY_HDR_SZ, "ss", &path, &name);
+            if (retval > 0) {
+                retval = lremovexattr(path.data, name.data);
+                if (retval < 0) {
+                    retval = -errno;
+                }
+            }
+            v9fs_string_free(&path);
+            v9fs_string_free(&name);
+            break;
+        case T_GETVERSION:
+            retval = do_getversion(&in_iovec, &out_iovec);
+            break;
+        default:
+            goto err_out;
+            break;
+        }
+
+        if (process_reply(sock, header.type, &out_iovec, retval) < 0) {
+            goto err_out;
+        }
+    }
+err_out:
+    g_free(in_iovec.iov_base);
+    g_free(out_iovec.iov_base);
+    return -1;
+}
+
+int main(int argc, char **argv)
+{
+    int sock;
+    uid_t own_u;
+    gid_t own_g;
+    char *rpath = NULL;
+    char *sock_name = NULL;
+    struct stat stbuf;
+    int c, option_index;
+#ifdef FS_IOC_GETVERSION
+    int retval;
+    struct statfs st_fs;
+#endif
+
+    prog_name = g_path_get_basename(argv[0]);
+
+    is_daemon = true;
+    sock = -1;
+    own_u = own_g = -1;
+    while (1) {
+        option_index = 0;
+        c = getopt_long(argc, argv, "p:nh?f:s:u:g:", helper_opts,
+                        &option_index);
+        if (c == -1) {
+            break;
+        }
+        switch (c) {
+        case 'p':
+            rpath = g_strdup(optarg);
+            break;
+        case 'n':
+            is_daemon = false;
+            break;
+        case 'f':
+            sock = atoi(optarg);
+            break;
+        case 's':
+            sock_name = g_strdup(optarg);
+            break;
+        case 'u':
+            own_u = atoi(optarg);
+            break;
+        case 'g':
+            own_g = atoi(optarg);
+            break;
+        case '?':
+        case 'h':
+        default:
+            usage();
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    /* Parameter validation */
+    if ((sock_name == NULL && sock == -1) || rpath == NULL) {
+        fprintf(stderr, "socket, socket descriptor or path not specified\n");
+        usage();
+        return -1;
+    }
+
+    if (sock_name && sock != -1) {
+        fprintf(stderr, "both named socket and socket descriptor specified\n");
+        usage();
+        exit(EXIT_FAILURE);
+    }
+
+    if (sock_name && (own_u == -1 || own_g == -1)) {
+        fprintf(stderr, "owner uid:gid not specified, ");
+        fprintf(stderr,
+                "owner uid:gid specifies who can access the socket file\n");
+        usage();
+        exit(EXIT_FAILURE);
+    }
+
+    if (lstat(rpath, &stbuf) < 0) {
+        fprintf(stderr, "invalid path \"%s\" specified, %s\n",
+                rpath, strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    if (!S_ISDIR(stbuf.st_mode)) {
+        fprintf(stderr, "specified path \"%s\" is not directory\n", rpath);
+        exit(EXIT_FAILURE);
+    }
+
+    if (is_daemon) {
+        if (daemon(0, 0) < 0) {
+            fprintf(stderr, "daemon call failed\n");
+            exit(EXIT_FAILURE);
+        }
+        openlog(PROGNAME, LOG_PID, LOG_DAEMON);
+    }
+
+    do_log(LOG_INFO, "Started\n");
+    if (sock_name) {
+        sock = proxy_socket(sock_name, own_u, own_g);
+        if (sock < 0) {
+            goto error;
+        }
+    }
+
+    if (chroot(rpath) < 0) {
+        do_perror("chroot");
+        goto error;
+    }
+    if (chdir("/") < 0) {
+        do_perror("chdir");
+        goto error;
+    }
+
+    get_version = false;
+#ifdef FS_IOC_GETVERSION
+    /* check whether underlying FS support IOC_GETVERSION */
+    retval = statfs("/", &st_fs);
+    if (!retval) {
+        switch (st_fs.f_type) {
+        case EXT2_SUPER_MAGIC:
+        case BTRFS_SUPER_MAGIC:
+        case REISERFS_SUPER_MAGIC:
+        case XFS_SUPER_MAGIC:
+            get_version = true;
+            break;
+        }
+    }
+#endif
+
+    umask(0);
+    if (init_capabilities() < 0) {
+        goto error;
+    }
+
+    process_requests(sock);
+error:
+    g_free(rpath);
+    g_free(sock_name);
+    do_log(LOG_INFO, "Done\n");
+    closelog();
+    return 0;
+}