From: Linus Lüssing <linus.luessing@c0d3.blue>
Date: Sat, 5 Sep 2015 03:18:28 +0200
Subject: kernel: bridge, multicast-to-unicast: fix echoes on STA

Currently, multicast packets from an STA are sent to any according
multicast listener directly through the bridge multicast-to-unicast
feature. Unfortunately, so far this includes the originating STA, too,
resulting in multicast packets being echo'ed back to the originating STA
if it itself is a multicast listener for that group.

This behaviour breaks IPv6 duplicate address detection: An IPv6 Neighbor
Solicitation for IPv6 Duplicate Address Detection is being echo'ed back,
resulting in the host falsely detecting an address collision, which
makes the node unable to claim an IPv6 address and use IPv6 in general.

Mac80211 unfortunately only prevents the echoes for us for multicast
frames. For the multicast frames cast to a unicast destination we'll
need to take care of excluding the originator ourselves.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46765 3c298f89-4303-0410-b956-a3cf2f4a3e73

diff --git a/target/linux/generic/patches-3.18/645-bridge_multicast_to_unicast.patch b/target/linux/generic/patches-3.18/645-bridge_multicast_to_unicast.patch
index 6707b03..399f5c6 100644
--- a/target/linux/generic/patches-3.18/645-bridge_multicast_to_unicast.patch
+++ b/target/linux/generic/patches-3.18/645-bridge_multicast_to_unicast.patch
@@ -297,7 +297,7 @@
  	rcu_assign_pointer(*pp, p);
 --- a/net/bridge/br_forward.c
 +++ b/net/bridge/br_forward.c
-@@ -168,6 +168,29 @@ out:
+@@ -168,6 +168,34 @@ out:
  	return p;
  }
  
@@ -308,10 +308,15 @@
 +			      struct sk_buff *skb))
 +{
 +	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
++	const unsigned char *src = eth_hdr(skb)->h_source;
 +
 +	if (!should_deliver(p, skb))
 +		return prev;
 +
++	/* Even with hairpin, no soliloquies - prevent breaking IPv6 DAD */
++	if (skb->dev == p->dev && ether_addr_equal(src, addr))
++		return prev;
++
 +	skb = skb_copy(skb, GFP_ATOMIC);
 +	if (!skb) {
 +		dev->stats.tx_dropped++;
@@ -327,7 +332,7 @@
  /* called under bridge lock */
  static void br_flood(struct net_bridge *br, struct sk_buff *skb,
  		     struct sk_buff *skb0,
-@@ -232,6 +255,7 @@ static void br_multicast_flood(struct ne
+@@ -232,6 +260,7 @@ static void br_multicast_flood(struct ne
  	struct net_bridge_port *prev = NULL;
  	struct net_bridge_port_group *p;
  	struct hlist_node *rp;
@@ -335,7 +340,7 @@
  
  	rp = rcu_dereference(hlist_first_rcu(&br->router_list));
  	p = mdst ? rcu_dereference(mdst->ports) : NULL;
-@@ -242,10 +266,19 @@ static void br_multicast_flood(struct ne
+@@ -242,10 +271,19 @@ static void br_multicast_flood(struct ne
  		rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
  			     NULL;