[Bug 270559] if_bridge: does not forward packets properly for vlan 1

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270559

--- Comment #15 from ben@desync.com ---
(In reply to Kristof Provost from comment #14)

Sure.  My apologies for being overly terse.

Create a bridge with IP address:
# ifconfig bridge create up
bridge0
# ifconfig bridge0 inet 10.0.0.1/30

Add an epair with the other end in a jail so we have something to ping:
# ifconfig epair create up
epair0a
# ifconfig bridge0 addm epair0a
# jail -ic persist vnet=new
1
# ifconfig epair0b vnet 1
# ifconfig -j 1 epair0b inet 10.0.0.2/30 up
# ifconfig -j 1 epair0b | grep ether
        ether 02:9d:22:b7:0a:0b

Start a ping and verify that the bridge learns the destination address:
# ping -q 10.0.0.2 &
# ifconfig bridge0 addr
02:9d:22:b7:0a:0b Vlan0 epair0a 1200 flags=0<>

Add some other interface to the bridge:
# ifconfig tap create up
tap0
# ifconfig bridge0 addm tap0
# cat /dev/tap0 >/dev/null &

See that unicast packets are being unexpectedly flooded to tap0 despite the
bridge table entry for the destination MAC:
# tcpdump -eni tap0
00:30:52.296892 58:9c:fc:00:ed:c1 > 02:9d:22:b7:0a:0b, ethertype IPv4 (0x0800),
length 98: 10.0.0.1 > 10.0.0.2: ICMP echo request, id 1572, seq 420, length 64

This fixes it for me:

diff --git a/sys/net/if_bridge.c b/sys/net/if_bridge.c
index d93bddf71ccb..9896c7a57191 100644
--- a/sys/net/if_bridge.c
+++ b/sys/net/if_bridge.c
@@ -2279,7 +2279,7 @@ bridge_transmit(struct ifnet *ifp, struct mbuf *m)
        eh = mtod(m, struct ether_header *);

        if (((m->m_flags & (M_BCAST|M_MCAST)) == 0) &&
-           (dst_if = bridge_rtlookup(sc, eh->ether_dhost, 1)) != NULL) {
+           (dst_if = bridge_rtlookup(sc, eh->ether_dhost, DOT1Q_VID_NULL)) !=
NULL) {
                error = bridge_enqueue(sc, dst_if, m);
        } else
                bridge_broadcast(sc, ifp, m, 0);

Thank you!

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