Comment 35 for bug 1254085

Hi everybody,
this is coming up over and over again and not only on Ubuntu but on various Distributions.

As outlined before the error is an effect of broken path MTU discovery.
This could be Firewall, broken Router software, ... , bad local MTU config, ... many potential sources.

It is nothing that "openssh" nor Ubuntu's openssh packaging can really fix.

The real "fix" is to fixup the network configuration wherever it is broken for correct PMTU discovery (or fix the local net/mtu configuration if that is the issue).

The mentioned workaround is nice - thank you bs for the mentioning - as it gives user unable to configure the network a way to work around the issue. The way it works is that it switches the MTU discovery to different modes (https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt).

That said one might argue why the default mode is disabled, but look at since when this is the default: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=5d424d5a674f782d0659a3b66d951f412901faee
That is a decade ago and never changed (these days namespacified, but still 0).
So I think this as default is set in stone as much as everything else that survives that long.

All that outlined I think we have to mark the bug invalid/incomplete as it should be considered a local configuration issue IMHO. Please of you object please set it back to confirmed and explain why you think so - and if possible please also mention how you'd suggest to approach the case.