untrusted comment: signature from openbsd 5.7 base secret key
RWSvUZXnw9gUb1W0cLwIa4jEVqEbfbRAGS88N9kYbqEIPQoOeEh4Pc+hQ0bFi3PPqyyPKzSvWUqZM4EgYQiyqB5UbOi/TwjyLg4=
OpenBSD 5.7 errata 10, July 14, 2015
A TCP socket can become confused and not properly cleanup resources.
cd /usr/src/sys/arch/`machine`/conf
KK=`sysctl -n kern.osversion | cut -d# -f1`
config $KK
cd ../compile/$KK
make
make install
Index: sys/netinet/tcp_output.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_output.c,v
retrieving revision 1.108
diff -u -p -r1.108 tcp_output.c
--- sys/netinet/tcp_output.c 19 Dec 2014 17:14:40 -0000 1.108
+++ sys/netinet/tcp_output.c 13 Jul 2015 16:09:43 -0000
@@ -1008,6 +1008,32 @@ send:
tp->t_rxtshift = 0;
}
}
+
+ if (len == 0 && so->so_snd.sb_cc &&
+ TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
+ TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
+ /*
+ * Avoid a situation where we do not set persist timer
+ * after a zero window condition. For example:
+ * 1) A -> B: packet with enough data to fill the window
+ * 2) B -> A: ACK for #1 + new data (0 window
+ * advertisement)
+ * 3) A -> B: ACK for #2, 0 len packet
+ *
+ * In this case, A will not activate the persist timer,
+ * because it chose to send a packet. Unless tcp_output
+ * is called for some other reason (delayed ack timer,
+ * another input packet from B, socket syscall), A will
+ * not send zero window probes.
+ *
+ * So, if you send a 0-length packet, but there is data
+ * in the socket buffer, and neither the rexmt or
+ * persist timer is already set, then activate the
+ * persist timer.
+ */
+ tp->t_rxtshift = 0;
+ tcp_setpersist(tp);
+ }
} else
if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
tp->snd_max = tp->snd_nxt + len;
