It... how... It's completely unrelated. It's not the same container, it's not the same network interface, the routing tables still look fine, AND I CAN PING. HOW DID THAT BREAK?
So now I've got to rip apart the network stack and see what it's doing. Figure out what exactly is going _wong_, and backtrack from there to identify which of the 8 gazillion strange and inadvisable things NFS is doing is triggering this behavior.
I despise NFS.
If I do a wget from the container, it works again. Doing an NFS mount horks the host's network context, and opening a normal network socket from the container's userspace fixes it.
This is epic levels of weird here. 100% reproducible. It happened in 2.6.37 and it's happening in current -git (darn near 2.6.38)...
Weeeeird... The funny thing is I'm ssh'ed into the box on the interface that's broken, and it continues to work fine while "broken", but I can't make _new_ network connections (either incoming or outgoing, I can't ssh a fresh session into the box) while it's screwed up. It's opening sockets, not sending packets, that's failing... Hmmm...