2 files changed, 15 insertions, 4 deletions

diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index b1b209daa9e9..84d3c1070dfa 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -1014,9 +1014,15 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 		if (to->to_flags & TOF_SCALE) {
 			int wscale = 0;
 
-			/* Compute proper scaling value from buffer space */
+			/*
+			 * Compute proper scaling value from buffer space.
+			 * Leave enough room for the socket buffer to grow
+			 * with auto sizing.  This allows us to scale the
+			 * receive buffer over a wide range while not losing
+			 * any efficiency or fine granularity.
+			 */
 			while (wscale < TCP_MAX_WINSHIFT &&
-			    (TCP_MAXWIN << wscale) < sb_hiwat)
+			    (0x1 << wscale) < tcp_minmss)
 				wscale++;
 			sc->sc_requested_r_scale = wscale;
 			sc->sc_requested_s_scale = to->to_requested_s_scale;
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index fa522b4e5ca9..35536617b78c 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -1131,9 +1131,14 @@ tcp_connect(tp, nam, td)
 	inp->inp_laddr = laddr;
 	in_pcbrehash(inp);
 
-	/* Compute window scaling to request.  */
+	/*
+	 * Compute window scaling to request:
+	 * Scale to fit into sweet spot.  See tcp_syncache.c.
+	 * XXX: This should move to tcp_output().
+	 * XXX: This should be based on the actual MSS.
+	 */
 	while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
-	    (TCP_MAXWIN << tp->request_r_scale) < so->so_rcv.sb_hiwat)
+	    (0x1 << tp->request_r_scale) < tcp_minmss)
 		tp->request_r_scale++;
 
 	soisconnecting(so);