[Bridge] Multicast packets are not bridged from ethernet to wireless interface

saurav barik saurav.barik at gmail.com
Fri Jul 31 10:20:35 UTC 2015


Hello,

I am working on an Access Point device (AP1) running linux kernel 3.0.34 on
which my bridge configuration is as follows.

~ # brctl show
bridge name     bridge id               STP enabled     interfaces
mbr             8000.xxxxxxxx0271       no                eth1

wlan0

wlan0 is connected by a wlan link to another access point AP2. This mbr on
AP1 gets IP address via wlan0. I have a laptop connected to eth1 interface
and it too gets IP address via eth1-bridged-wlan0 (wlan0 is the only uplink
port). All the unicast packets (ping traffic) from the laptop via
eth1-bridged-wlan0 works fine. However when I start a multicast tx (iperf
multicast) from the laptop, the multicast packet reaches eth1 and then gets
dropped in the bridge module. I debugged and found the packets are dropped
at -

br_multicast_flood(struct net_bridge_mdb_entry *mdst, ....)
.... <code snippet>
        while (p || rp) {
....
        rp = rcu_dereference(hlist_first_rcu(&br->router_list));
        p = mdst ? rcu_dereference(mdst->ports) : NULL;
        }

        if (!prev)
        {
 /******* packets getting dropped here.  *********/
                goto out;
        }
........

The three pointers mdst, p and rp  are NULL. Prior to reaching here, the
packet traversed successfully via
br_handle_frame()->br_handle_frame_finish()->br_multicast_forward()->br_multicast_flood().
The source and multicast destination address in the skb look alright.

Additional Note: I have another ethernet interface on AP1 which is eth0. If
I remove wlan0 and add eth0, then multicast packets successfully pass from
eth1 to eth0 in the bridge module.

Could anybody share some pointer on this? Thank you.

With Regards,
Saurav
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