bridge: Add support for IEEE 802.11 Proxy ARP

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index ff95760..62a17e0 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -231,6 +231,7 @@  enum {
 	IFLA_BRPORT_FAST_LEAVE,	/* multicast fast leave    */
 	IFLA_BRPORT_LEARNING,	/* mac learning */
 	IFLA_BRPORT_UNICAST_FLOOD, /* flood unicast traffic */
+	IFLA_BRPORT_PROXYARP,	/* proxy ARP */
 	__IFLA_BRPORT_MAX
 };
 #define IFLA_BRPORT_MAX (__IFLA_BRPORT_MAX - 1)
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 056b67b..61d9edf 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -181,6 +181,11 @@  static void br_flood(struct net_bridge *br, struct sk_buff *skb,
 		/* Do not flood unicast traffic to ports that turn it off */
 		if (unicast && !(p->flags & BR_FLOOD))
 			continue;
+
+		/* Do not flood to ports that enable proxy ARP */
+		if (p->flags & BR_PROXYARP)
+			continue;
+
 		prev = maybe_deliver(prev, p, skb, __packet_hook);
 		if (IS_ERR(prev))
 			goto out;
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 366c436..a548fbf 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -16,6 +16,8 @@ 
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/netfilter_bridge.h>
+#include <linux/neighbour.h>
+#include <net/arp.h>
 #include <linux/export.h>
 #include <linux/rculist.h>
 #include "br_private.h"
@@ -57,6 +59,60 @@  static int br_pass_frame_up(struct sk_buff *skb)
 		       netif_receive_skb);
 }
 
+static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
+			    u16 vid)
+{
+	struct net_device *dev = br->dev;
+	struct neighbour *n;
+	struct arphdr *parp;
+	u8 *arpptr, *sha;
+	__be32 sip, tip;
+
+	if (dev->flags & IFF_NOARP)
+		return;
+
+	if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
+		dev->stats.tx_dropped++;
+		return;
+	}
+	parp = arp_hdr(skb);
+
+	if (parp->ar_pro != htons(ETH_P_IP) ||
+	    parp->ar_op != htons(ARPOP_REQUEST) ||
+	    parp->ar_hln != dev->addr_len ||
+	    parp->ar_pln != 4)
+		return;
+
+	arpptr = (u8 *)parp + sizeof(struct arphdr);
+	sha = arpptr;
+	arpptr += dev->addr_len;	/* sha */
+	memcpy(&sip, arpptr, sizeof(sip));
+	arpptr += sizeof(sip);
+	arpptr += dev->addr_len;	/* tha */
+	memcpy(&tip, arpptr, sizeof(tip));
+
+	if (ipv4_is_loopback(tip) ||
+	    ipv4_is_multicast(tip))
+		return;
+
+	n = neigh_lookup(&arp_tbl, &tip, dev);
+	if (n) {
+		struct net_bridge_fdb_entry *f;
+
+		if (!(n->nud_state & NUD_VALID)) {
+			neigh_release(n);
+			return;
+		}
+
+		f = __br_fdb_get(br, n->ha, vid);
+		if (f)
+			arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
+				 sha, n->ha, sha);
+
+		neigh_release(n);
+	}
+}
+
 /* note: already called with rcu_read_lock */
 int br_handle_frame_finish(struct sk_buff *skb)
 {
@@ -98,6 +154,10 @@  int br_handle_frame_finish(struct sk_buff *skb)
 	dst = NULL;
 
 	if (is_broadcast_ether_addr(dest)) {
+		if (p->flags & BR_PROXYARP &&
+		    skb->protocol == htons(ETH_P_ARP))
+			br_do_proxy_arp(skb, br, vid);
+
 		skb2 = skb;
 		unicast = false;
 	} else if (is_multicast_ether_addr(dest)) {
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index cb5fcf6..caa6857 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -60,7 +60,8 @@  static int br_port_fill_attrs(struct sk_buff *skb,
 	    nla_put_u8(skb, IFLA_BRPORT_PROTECT, !!(p->flags & BR_ROOT_BLOCK)) ||
 	    nla_put_u8(skb, IFLA_BRPORT_FAST_LEAVE, !!(p->flags & BR_MULTICAST_FAST_LEAVE)) ||
 	    nla_put_u8(skb, IFLA_BRPORT_LEARNING, !!(p->flags & BR_LEARNING)) ||
-	    nla_put_u8(skb, IFLA_BRPORT_UNICAST_FLOOD, !!(p->flags & BR_FLOOD)))
+	    nla_put_u8(skb, IFLA_BRPORT_UNICAST_FLOOD, !!(p->flags & BR_FLOOD)) ||
+	    nla_put_u8(skb, IFLA_BRPORT_PROXYARP, !!(p->flags & BR_PROXYARP)))
 		return -EMSGSIZE;
 
 	return 0;
@@ -335,6 +336,7 @@  static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
 	br_set_port_flag(p, tb, IFLA_BRPORT_PROTECT, BR_ROOT_BLOCK);
 	br_set_port_flag(p, tb, IFLA_BRPORT_LEARNING, BR_LEARNING);
 	br_set_port_flag(p, tb, IFLA_BRPORT_UNICAST_FLOOD, BR_FLOOD);
+	br_set_port_flag(p, tb, IFLA_BRPORT_PROXYARP, BR_PROXYARP);
 
 	if (tb[IFLA_BRPORT_COST]) {
 		err = br_stp_set_path_cost(p, nla_get_u32(tb[IFLA_BRPORT_COST]));
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index b6c04cb..666c6bc 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -172,6 +172,7 @@  struct net_bridge_port
 #define BR_FLOOD		0x00000040
 #define BR_AUTO_MASK (BR_FLOOD | BR_LEARNING)
 #define BR_PROMISC		0x00000080
+#define BR_PROXYARP		0x00000100
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 	struct bridge_mcast_own_query	ip4_own_query;
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index e561cd5..2de5d91 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -170,6 +170,7 @@  BRPORT_ATTR_FLAG(bpdu_guard, BR_BPDU_GUARD);
 BRPORT_ATTR_FLAG(root_block, BR_ROOT_BLOCK);
 BRPORT_ATTR_FLAG(learning, BR_LEARNING);
 BRPORT_ATTR_FLAG(unicast_flood, BR_FLOOD);
+BRPORT_ATTR_FLAG(proxyarp, BR_PROXYARP);
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t show_multicast_router(struct net_bridge_port *p, char *buf)
@@ -213,6 +214,7 @@  static const struct brport_attribute *brport_attrs[] = {
 	&brport_attr_multicast_router,
 	&brport_attr_multicast_fast_leave,
 #endif
+	&brport_attr_proxyarp,
 	NULL
 };