af_packet: don't emit packet on orig fanout group

[ Upstream commit c0de08d04215031d68fa13af36f347a6cfa252ca ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index cd0d9bb2091..078fdffcd55 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1280,6 +1280,14 @@ static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
 	spin_unlock(&f->lock);
 }
 
+bool match_fanout_group(struct packet_type *ptype, struct sock * sk)
+{
+	if (ptype->af_packet_priv == (void*)((struct packet_sock *)sk)->fanout)
+		return true;
+
+	return false;
+}
+
 static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
 {
 	struct packet_sock *po = pkt_sk(sk);
@@ -1332,6 +1340,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
 		match->prot_hook.dev = po->prot_hook.dev;
 		match->prot_hook.func = packet_rcv_fanout;
 		match->prot_hook.af_packet_priv = match;
+		match->prot_hook.id_match = match_fanout_group;
 		dev_add_pack(&match->prot_hook);
 		list_add(&match->list, &fanout_list);
 	}