Re: NFS lockup after UDP fragments getting lost (was: 8.1 tstile lockup after nfs send error 51)

[Hauke Fath <hauke%Espresso.Rhein-Neckar.DE@localhost>]

At 10:45 Uhr +0200 31.07.2019, Edgar Fuß wrote:
>Thanks to riastradh@, this tuned out to be caused by an (UDP, hard) HFS
>mount combined with a mis-configured IPFilter that blocked all but the
>first fragment of a fragmented NFS reply (e.g., readdir) combined with a
>NetBSD design error (or so Taylor says) that a vnode lock may be held
>accross I/O, in this case, network I/O.

I ran into a similar issue 2004ish, connecting RedHat Linux clients to a
(NetBSD) nfs (udp)  server through a (NetBSD, ipfilter) filtering router.
Darren back then told me Linux sends fragmented packets tail-first, which
ipfilter was not prepared to deal with.

I switched to pf, which was able deal with the scenario just fine, and
didn't look back.

Cheerio,
hauke


--
"It's never straight up and down"     (DEVO)