Hm, one correction to that patch.  Otherwise we might kick in silly
window avoidance on the second packet.


Index: tcp_output.c
===================================================================
RCS file: /cvsroot/syssrc/sys/netinet/tcp_output.c,v
retrieving revision 1.83
diff -u -r1.83 tcp_output.c
--- tcp_output.c	2002/06/13 16:31:05	1.83
+++ tcp_output.c	2002/07/16 18:12:50
@@ -230,6 +230,7 @@
 #ifdef INET6
 	struct in6pcb *in6p = tp->t_in6pcb;
 #endif
+	struct socket *so;
 	struct rtentry *rt;
 	struct ifnet *ifp;
 	int size;
@@ -258,12 +259,16 @@
 
 	rt = NULL;
 #ifdef INET
-	if (inp)
+	if (inp) {
 		rt = in_pcbrtentry(inp);
+		so = inp->inp_socket;
+	}
 #endif
 #ifdef INET6
-	if (in6p)
+	if (in6p) {
 		rt = in6_pcbrtentry(in6p);
+		so = in6p->in6p_socket;
+	}
 #endif
 	if (rt == NULL) {
 		size = tcp_mssdflt;
@@ -350,6 +355,15 @@
 	 * I'm not quite sure about this (could someone comment).
 	 */
 	*txsegsizep = min(tp->t_peermss - optlen, size);
+	/*
+	 * Never send more than half a buffer full.  This insures that we can
+	 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
+	 * therefore acks will never be delayed unless we run out of data to
+	 * transmit.
+	 */
+	if (so)
+		*txsegsizep = min((so->so_snd.sb_hiwat >> 1) - optlen,
+		    *txsegsizep);
 	*rxsegsizep = min(tp->t_ourmss - optlen, size);
 
 	if (*txsegsizep != tp->t_segsz) {