af_packet: don't emit packet on orig fanout group

If a packet is emitted on one socket in one group of fanout sockets,
it is transmitted again. It is thus read again on one of the sockets
of the fanout group. This result in a loop for software which
generate packets when receiving one.
This retransmission is not the intended behavior: a fanout group
must behave like a single socket. The packet should not be
transmitted on a socket if it originates from a socket belonging
to the same fanout group.

This patch fixes the issue by changing the transmission check to
take fanout group info account.

Reported-by: Aleksandr Kotov <a1k@mail.ru>
Signed-off-by: Eric Leblond <eric@regit.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 2 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index a39354e..debd937 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1642,6 +1642,19 @@ static inline int deliver_skb(struct sk_buff *skb,
 	return pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
 }
 
+static inline bool skb_loop_sk(struct packet_type *ptype, struct sk_buff *skb)
+{
+	if (ptype->af_packet_priv == NULL)
+		return false;
+
+	if (ptype->id_match)
+		return ptype->id_match(ptype, skb->sk);
+	else if ((struct sock *)ptype->af_packet_priv == skb->sk)
+		return true;
+
+	return false;
+}
+
 /*
  *	Support routine. Sends outgoing frames to any network
  *	taps currently in use.
@@ -1659,8 +1672,7 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 		 * they originated from - MvS (miquels@drinkel.ow.org)
 		 */
 		if ((ptype->dev == dev || !ptype->dev) &&
-		    (ptype->af_packet_priv == NULL ||
-		     (struct sock *)ptype->af_packet_priv != skb->sk)) {
+		    (!skb_loop_sk(ptype, skb))) {
 			if (pt_prev) {
 				deliver_skb(skb2, pt_prev, skb->dev);
 				pt_prev = ptype;