Hi. I have a Linux router running 3.18.23 with IPv6 as well as IPv4 interfaces. It doesn't seem to be hearing IPv6 multicast packets though.
For example, it won't hear and respond to either router or neighbour
discovery packets unless i put the interface in promiscuous mode with
tcpdump. I'm a bit stumped at what could cause that.
The interface that is not hearing the IPv6 multicast packets is a
bridge with an ethernet and wifi interfaces as members:
# brctl show br-lan
bridge name bridge id STP enabled interfaces
br-lan 7fff.26d42cb3eadf no eth0.1
wlan0
wlan1
The bridge does have the right multicast addresses configured in
/proc/net/dev_mcast:
8 br-lan 1 0 333300000001
8 br-lan 1 0 333300000002
8 br-lan 1 0 01005e000001
8 br-lan 1 0 3333ff000001
8 br-lan 1 0 3333ffb3eadf
8 br-lan 1 0 3333ff000000
8 br-lan 1 0 01005e000005
8 br-lan 1 0 01005e000006
But what is interesting is that the wlan{0,1} interfaces that are in
the br-lan bridge are in the /proc/net/dev_mcast also:
15 wlan1 2 0 333300000001
15 wlan1 2 0 333300000002
15 wlan1 2 0 01005e000001
15 wlan1 2 0 3333fff51e4c
15 wlan1 2 0 3333ff000000
16 wlan0 2 0 333300000001
16 wlan0 2 0 333300000002
16 wlan0 2 0 01005e000001
16 wlan0 2 0 3333fff51e4a
16 wlan0 2 0 3333ff000000
But the ethernet member, eth0.1 is not.
Is it sufficient to have a bridge interface in /proc/net/dev_mcast or
do all of it's member interfaces need the respective multicast
addresses listed in that file also? It just seems odd to me that the
wlan interfaces are there but the ethernet interface is not.
If it is sufficient to have just the bridge in /proc/net/dev_mcast what
else could be causing this "deafness" to multicast that is resolved by
putting the interface into promiscuous mode?
Cheers,
b.
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