[PATCH] netlink: report why a packet is bad

Ian Jackson ijackson at chiark.greenend.org.uk
Wed Dec 28 00:46:59 GMT 2011

Earlier today I found that my VPN to my netbook was broken.  On
investigation with strace I found secnet blocked on write to fd 12.

This fd appeared to be one of its fds to the userv ipif farm.  I ran
out of time before I was able to strace the corresponding copy of cat
and determine which of the userv client's fds it corresponded to.  But
I think the fd must have been the one for transferring packet data
from secnet to the kernel.  The only reasonable explanation for
blocking on that fd would seem to be a kernel bug in the slip line
discipline.  I'm aware of bugs in the slip line discipline - I've seen
regular kernel oopses in slattach in some kernels, at least as
recently as lenny.

I have an experimental but as-yet-unreleased version of userv ipif
which uses tun rather than slattach.  I will try to prioritise
(a) releasing it and (b) installing it on chiark.

While I'm on these kind of subjects I noticed that the stderr output
from userv ipif doesn't seem to end up in ~secnet/live/log.


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