Multicast and overlay network

[auzias]

I am testing a application using multicast for the discovery. I created a Swarm cluster and a network create -d overlay swarm-net so the containers share the same LAN across the several Swarm agents hosts.

The discovery seemed to not be working, so I installed tshark. tshark shows the IP address node within which tshark is running and the multicast address for the packet being sent though tshark does not show any incoming multicast packet.

Note that, as I don't know a better way to do so, the container is run with --privileged to enable tshark.

Is the multicast blocked because of Docker iptable?
How to enable multicast in an overlay network?

Any help would be welcome. I don't know if it is a bug or just an obvious issue I can't debbug myself, this is also post on SO.

---

Environment details

docker version

Client:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.2
 Git commit:   a34a1d5
 Built:        Fri Nov 20 12:59:02 UTC 2015
 OS/Arch:      linux/amd64

Server:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.2
 Git commit:   a34a1d5
 Built:        Fri Nov 20 12:59:02 UTC 2015
 OS/Arch:      linux/amd64

docker info

Containers: 68
Images: 12
Server Version: 1.9.1
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 148
 Dirperm1 Supported: true
Execution Driver: native-0.2
Logging Driver: json-file
Kernel Version: 3.16.0-4-amd64
Operating System: Debian GNU/Linux 8 (jessie)
CPUs: 12
Total Memory: 47.25 GiB
Name: bugs20
ID: DVQZ:XBAT:IN4R:VLTP:2B4H:J4LX:4TDT:HXL7:U6QT:O3IQ:MB6E:XSRP
WARNING: No memory limit support
WARNING: No swap limit support
Cluster store: consul://127.0.0.1:8500
Cluster advertise: 192.168.196.20:2375

uname -a

Linux bugs20 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1+deb8u6 (2015-11-09) x86_64 GNU/Linux

docker -H tcp://0.0.0.0:5732 -v #swarm-docker -v

Docker version 1.9.1, build a34a1d5

consul -v

Consul v0.5.2
Consul Protocol: 2 (Understands back to: 1)

[chanwit]

Hi @auzias
I do not think an overlay network supports multicast.

cc @vieux @mavenugo

[auzias]

Really ?! 😨

Does the doc give details about it? I can't find anything about that. I really did not expect such drawback. Where can I find info about it without getting lost in the source code?

[chanwit]

@auzias maybe I'm wrong.

Please wait for @mavenugo or other libnetwork guys to answer this.
We still have some hope.

[chanwit]

@auzias Oh this is a bad news for you.
Libnetwork uses vxlan unicast.
moby/libnetwork#552.

But I think multicast will be implemented soon enough or maybe you can try some third-party plugins.

[auzias]

Any suggestion for third-party plugins?

I don't get the link between the moby/libnetwork#522 and mine.

[chanwit]

@auzias Sorry for my typo it's moby/libnetwork#552.

[mavenugo]

@auzias @chanwit, atm overlay driver doesn't support multicast. contributions welcome.

[auzias]

@mavenugo where should I start to contribute ?

[mavenugo]

@auzias moby/libnetwork#552

[nishanttotla]

Closing this issue since it's a libnetwork issue being discussed at moby/libnetwork#552.