mpd5/Netgraph issues after upgrading to 7.4

[Gleb Smirnoff]

On Tue, Jul 10, 2012 at 12:03:36PM +0700, Eugene Grosbein wrote:
E> 10.07.2012 03:25, Ryan Stone пишет:
E> > On Mon, Jul 9, 2012 at 4:12 AM, Gleb Smirnoff <glebius at freebsd.org> wrote:
E> >> This looks very much related to a known race in ARP code.
E> >>
E> >> See this email and related thread:
E> >>
E> >> http://lists.freebsd.org/pipermail/freebsd-net/2012-March/031865.html
E> >>
E> >> Ryan didn't check in any patches since, and I failed to follow on this
E> >> problem due to ENOTIME.
E> >>
E> >> I've added Ryan to Cc. Ryan, what's the status of the problem at your
E> >> side? Did you come to any solution?
E> > 
E> > Unfortunately I was never able to come to a satisfactory solution.  As
E> > I recall, in the end I ran headlong into problems with making the
E> > locking sane.  The big problem was with arpresolve.  At one point it
E> > calls callout_reset to schedule the LLE's la_timer.  In my patch this
E> > would have to be done with a write lock help on the afdata lock.
E> > However, this acquisition would have to be done before taking the
E> > LLE_LOCK to prevent a LOR, and in the end you conclude that you have
E> > to take a write lock on the ifnet's afdata lock for every packet that
E> > goes through arpresolve, which was a non-starter.  That's the point
E> > that I reached before I got distracted by other things at $WORK.
E> > 
E> > As I recall, the in6 case was even worse, as the in6 equivalent of
E> > arptimer is significantly more complicated and likes to do crazy
E> > things like dropping locks.
E> 
E> It seems, Przemyslaw Frasunek uses proxyarp?
E> I have no such problems but I do not use proxyarp.
E> Could you get rid of it, Przemyslaw?

I'm not sure this is related. The race happens w/o proxy arp as well.

-- 
Totus tuus, Glebius.