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don't try to use default route MTU as container MTU #18108
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LGTM, but I'll wait until someone in the networking teams gives their 👍 |
I'm going to take a look at what mountkin mentioned. |
Yeah, I'm not able to reproduce any issues on GCE. Everything behaves exactly as it's supposed to. I launched a GCE box. Host MTU was 1460. Launched docker with
Notice the ICMP |
Thanks @phemmer for the test. |
thanks @phemmer ! Needs a rebase |
rebased |
LGTM |
Thanks @phemmer! I searched the docs, and it looks like https://github.com/docker/docker/blob/43077f9b6406e3d5e401a361b4c9742c00be528b/docs/userguide/networking/default_network/custom-docker0.md mentions setting the default based on the hosts interface, so that may need some changes. I don't think other sections of the documentation mention the default value currently. |
Signed-off-by: Patrick Hemmer <patrick.hemmer@gmail.com>
Documentation adjusted. |
Thanks @phemmer! LGTM |
don't try to use default route MTU as container MTU
Trying to use the default route's MTU as the container (bridge) MTU is a bad idea:
Aside from the issues trying to determine the MTU to use, it's also unnecessary. The kernel performs path MTU discovery to resolve this exact situation. So, this PR lets the kernel do its job.
It might even be a good idea to raise the default MTU to 9000. But this PR just fixes the bad behavior. We can improve things in another PR.
closes #7796