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Cannot receive external multicast inside container #23659
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/cc @mavenugo |
Tested as well on Docker for Mac v1.12.0-rc2. Same result. |
anybody? |
This is likely because you don't specify the correct interface/source address on the host, and the network stack on the host side is selecting one (the wrong one) for you. |
What happens is that it looks like IGMP JOIN never leaves container's network stack. I tried monitoring all host network interfaces with |
224.0.0.0/8 is not a host prefix. |
Tried this just now. Same result - no multicast. On Thu, Aug 18, 2016 at 6:04 AM Justin Cormack notifications@github.com
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@combitel, are you figured out it? |
As of Docker 18 this is still an issue :( |
The issue here is more than just "external" multicast. Two containers on a single host attached to the same network (default bridge network or a user-defined network,) cannot send/receive multicast with each other. See this issue: Edit: Fixed link. Also, to clarify: my use has been with Docker for Windows running Linux containers (not LCOW). |
But how this is a docker problem?? this is almost a network stack problem.... |
There is also a ticket here moby/libnetwork#2397 which receives even less attention then this one. I'm not a network expert, but shouldn't docker be able to forward the multicast messages just like a multicast enabled router would? |
Output of
docker version
:Output of
docker info
:Steps to reproduce the issue:
docker run -it --name node1 ubuntu:14.04 /bin/bash
apt-get update && apt-get install iperf
iperf -s -u -B 224.0.55.55 -i 1
iperf -c 224.0.55.55 -u -T 32 -t 3 -i 1
Describe the results you received:
Multicast is not received by multicast listener inside container.
Describe the results you expected:
If application in container joins multicast group, then multicast traffic must be forwarded to container's NIC.
Additional information you deem important (e.g. issue happens only occasionally):
It works fine with --net host, but for various reasons it's not an option.
It looks like IGMP JOIN never leaves container's NIC. I checked it on host using
tcpdump -i any host 224.0.55.55
and get 0 packets when container joins 224.0.55.55 group.Any help or pointers is really appreciated.
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