From: Alex Gonzalez <alex.gonzalez@digi.com>
Date: Fri, 7 Sep 2018 13:01:54 +0200
Subject: [PATCH] net: wireless: Add
 cfg80211_is_gratuitous_arp_unsolicited_na()

The QCA6564 driver makes use of this call when compiled with the
QCA_VENDOR_KERNEL flag.

Signed-off-by: Alex Gonzalez <alex.gonzalez@digi.com>
---
 include/net/cfg80211.h | 10 ++++++++++
 net/wireless/util.c    | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 3082f6bf047d..42445bd1c26a 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -6736,6 +6736,16 @@ void cfg80211_crit_proto_stopped(struct wireless_dev *wdev, gfp_t gfp);
 unsigned int ieee80211_get_num_supported_channels(struct wiphy *wiphy);
 
 /**
+ * cfg80211_is_gratuitous_arp_unsolicited_na - packet is grat. ARP/unsol. NA
+ * @skb: the input packet, must be an ethernet frame already
+ *
+ * Return: %true if the packet is a gratuitous ARP or unsolicited NA packet.
+ * This is used to drop packets that shouldn't occur because the AP implements
+ * a proxy service.
+ */
+bool cfg80211_is_gratuitous_arp_unsolicited_na(struct sk_buff *skb);
+
+/**
  * cfg80211_check_combinations - check interface combinations
  *
  * @wiphy: the wiphy
diff --git a/net/wireless/util.c b/net/wireless/util.c
index ec30e3732c7b..abcefae39e81 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -2061,3 +2061,55 @@ int ieee80211_get_vht_max_nss(struct ieee80211_vht_cap *cap,
 	return max_vht_nss;
 }
 EXPORT_SYMBOL(ieee80211_get_vht_max_nss);
+
+bool cfg80211_is_gratuitous_arp_unsolicited_na(struct sk_buff *skb)
+{
+	const struct ethhdr *eth = (void *)skb->data;
+
+	const struct {
+		struct arphdr hdr;
+		u8 ar_sha[ETH_ALEN];
+		u8 ar_sip[4];
+		u8 ar_tha[ETH_ALEN];
+		u8 ar_tip[4];
+	} __packed * arp;
+
+	const struct ipv6hdr *ipv6;
+	const struct icmp6hdr *icmpv6;
+
+	switch (eth->h_proto) {
+	case cpu_to_be16(ETH_P_ARP):
+		/* can't say - but will probably be dropped later anyway */
+		if (!pskb_may_pull(skb, sizeof(*eth) + sizeof(*arp)))
+			return false;
+
+		arp = (void *)(eth + 1);
+
+		if ((arp->hdr.ar_op == cpu_to_be16(ARPOP_REPLY) ||
+		     arp->hdr.ar_op == cpu_to_be16(ARPOP_REQUEST)) &&
+		    !memcmp(arp->ar_sip, arp->ar_tip, sizeof(arp->ar_sip)))
+			return true;
+		break;
+	case cpu_to_be16(ETH_P_IPV6):
+		/* can't say - but will probably be dropped later anyway */
+		if (!pskb_may_pull(skb, sizeof(*eth) + sizeof(*ipv6) +
+					sizeof(*icmpv6)))
+			return false;
+
+		ipv6 = (void *)(eth + 1);
+		icmpv6 = (void *)(ipv6 + 1);
+
+		if (icmpv6->icmp6_type == NDISC_NEIGHBOUR_ADVERTISEMENT &&
+		    !memcmp(&ipv6->saddr, &ipv6->daddr, sizeof(ipv6->saddr)))
+			return true;
+		break;
+	default:
+		/* no need to support other protocols, proxy service isn't
+		 * specified for any others
+		 */
+		break;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL(cfg80211_is_gratuitous_arp_unsolicited_na);