From: Tom Smyth <tom.smyth@wirelessconnect.eu>
Subject: Re: bgpd: properly discard pfkey error messages
To: tech@openbsd.org
Date: Fri, 12 Sep 2025 13:00:59 +0100

Hi Theo, Claudio
Thanks for fix diff and the review.

Much obliged,
Tom Smyth


On Fri, 12 Sept 2025 at 12:44, Theo Buehler <tb@theobuehler.org> wrote:
>
> On Fri, Sep 12, 2025 at 01:34:34PM +0200, Claudio Jeker wrote:
> > pfkey_reply() needs to discard any error message (including those for
> > ESRCH). The fix I did in 1.64 was not quite right since for the ESRCH
> > case the message remained in the socket and that results into a busy
> > loop in the bgpd main event loop since a ESRCH message is newer flushed
> > from the socket.
> >
> > This is a fix for the busy loop Tom Smyth reported on bugs@.
> > Thanks to Tom for providing me with a ktrace of bgpd that made me find the
> > bug in less than 5min.
>
> Fortunately the diff is as easy to review as it was to find the fix.
> Definitely looks like something a diligent reviewer might've caught...
>
> ok tb
>
> > --
> > :wq Claudio
> >
> > Index: pfkey.c
> > ===================================================================
> > RCS file: /cvs/src/usr.sbin/bgpd/pfkey.c,v
> > diff -u -p -r1.72 pfkey.c
> > --- pfkey.c   27 Feb 2025 14:03:32 -0000      1.72
> > +++ pfkey.c   12 Sep 2025 11:27:44 -0000
> > @@ -453,13 +453,15 @@ pfkey_reply(int sd, uint32_t *spi)
> >
> >       if (hdr.sadb_msg_errno != 0) {
> >               errno = hdr.sadb_msg_errno;
> > +
> > +             /* discard error message */
> > +             if (read(sd, &hdr, sizeof(hdr)) == -1)
> > +                     log_warn("pfkey read");
> > +
> >               if (errno == ESRCH)
> >                       return (0);
> >               else {
> >                       log_warn("pfkey");
> > -                     /* discard error message */
> > -                     if (read(sd, &hdr, sizeof(hdr)) == -1)
> > -                             log_warn("pfkey read");
> >                       return (-1);
> >               }
> >       }
> >
>


--
Kindest regards,
Tom Smyth.