Docker receiving multicast traffic

Question

We have a dockerized server application that is doing auto-discovery of physical appliances on the network by listening for multicast packets on port 6969. So we need our do

Answer 1

Try to enable multicast on your nics:

ip link set eth0 multicast on

echo 1 >/proc/sys/net/ipv4/ip_forward to turn on IP forwarding

You need to explicitly set or at least check that it is enabled on relevant interfaces.

net.ipv4.conf.all.mc_forwarding = 1
net.ipv4.conf.eth0.rp_filter=0

Allow the multicast traffic:

iptables -I INPUT -d 224.0.0.0/4 -j ACCEPT
iptables -I FORWARD -d 224.0.0.0/4 -j ACCEPT

Also you might need to add the route for multicast traffic:

route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0 

Change the TTL of the multicast sender:

iptables -t mangle -A OUTPUT -d <group> -j TTL --ttl-set 128
Where group is the multicast group address of the stream you want to change the TTL of.

Also you can start multicast proxy

PS:

You should try (if above doesn't help) to start docker container with --net=none option and use pipework with follow command:

pipework docker0 -i eth0 CONTAINER_ID IP_ADDRESS/IP_MASK@DEFAULT_ROUTE_IP 

which creates eth0 interface inside container with IFF_MULTICAST flag and defined IP address.