On Mon, Aug 17, 2015 at 08:26:21PM +0200, Alexander Bluhm wrote:
> When running my pf regression tests, I triggered netcat hanging in
> write(2). This is bit strange as poll(2) should check that the socket
> is writeable.
Disregard the netstat diff, fix poll(2) in the kernel instead.
bluhm
Index: netinet/tcp_usrreq.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_usrreq.c,v
retrieving revision 1.126
diff -u -p -r1.126 tcp_usrreq.c
--- netinet/tcp_usrreq.c 15 Jul 2015 22:16:42 -0000 1.126
+++ netinet/tcp_usrreq.c 18 Aug 2015 19:57:48 -0000
@@ -980,6 +980,14 @@ tcp_update_sndspace(struct tcpcb *tp)
nmax = MIN(sb_max, so->so_snd.sb_wat + tp->snd_max -
tp->snd_una);
+ /* a writable socket must be preserved because of poll(2) semantics */
+ if (sbspace(&so->so_snd) >= so->so_snd.sb_lowat) {
+ if (nmax < so->so_snd.sb_cc + so->so_snd.sb_lowat)
+ nmax = so->so_snd.sb_cc + so->so_snd.sb_lowat;
+ if (nmax * 2 < so->so_snd.sb_mbcnt + so->so_snd.sb_lowat)
+ nmax = (so->so_snd.sb_mbcnt+so->so_snd.sb_lowat+1) / 2;
+ }
+
/* round to MSS boundary */
nmax = roundup(nmax, tp->t_maxseg);
@@ -1011,6 +1019,11 @@ tcp_update_rcvspace(struct tcpcb *tp)
nmax = MIN(sb_max, so->so_rcv.sb_hiwat +
tcp_autorcvbuf_inc);
}
+
+ /* a readable socket must be preserved because of poll(2) semantics */
+ if (so->so_rcv.sb_cc >= so->so_rcv.sb_lowat &&
+ nmax < so->so_snd.sb_lowat)
+ nmax = so->so_snd.sb_lowat;
if (nmax == so->so_rcv.sb_hiwat)
return;
