On Mon, 2013-12-30 at 16:41 -0500, Bob Tenty spake:
Is interface mtu 0 not discovery off? (as the path mtu was set to nopmtudisc)
This is part of the bug.
Maybe setting the interface mtu to a fixed value will solve your problem.
Setting the ttl to a fixed value did switch path mtu discovery on originally but maybe this new behaviour with interface mtu 0 is causing the problem you have?
If you have a Pi, please run the full wheezy update/upgrade and you'll experience what I and others who've emailed me offlist have seen. You can't "ifconfig <dev> mtu 0", it would be illogical and wouldn't let you do such anyway. The issue isn't so much with MTU anyway it's with ttl. Ip tunnel will NOT allow you to set a ttl to an interface named tunl0 but it will tunl1 or any other tunnel interface.
This does not prevent routing, it only prevents proper traceroutes. Even leaving MTU = 0, routing still works. It autosenses MTU required and adjusts per link request. TTL however is another story and you can NOT adjust it anymore. Prior to the update I could w/o issue.