[PATCH] Don't over-clamp window in tcp_clamp_window()

Handle better the case where the sender sends full sized
frames initially, then moves to a mode where it trickles
out small amounts of data at a time.

This known problem is even mentioned in the comments
above tcp_grow_window() in tcp_input.c, specifically:

...
 * The scheme does not work when sender sends good segments opening
 * window and then starts to feed us spagetti. But it should work
 * in common situations. Otherwise, we have to rely on queue collapsing.
...

When the sender gives full sized frames, the "struct sk_buff" overhead
from each packet is small.  So we'll advertize a larger window.
If the sender moves to a mode where small segments are sent, this
ratio becomes tilted to the other extreme and we start overrunning
the socket buffer space.

tcp_clamp_window() tries to address this, but it's clamping of
tp->window_clamp is a wee bit too aggressive for this particular case.

Fix confirmed by Ion Badulescu.

Signed-off-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Chris Wright <chrisw@osdl.org>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 53a8a5399f1e6e6de3b13a05d691612c533f433c..5557c338b56d452d0d8aebaf4432a9b7539314d2 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -350,8 +350,6 @@ static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
                        app_win -= tp->ack.rcv_mss;
                app_win = max(app_win, 2U*tp->advmss);
 
-               if (!ofo_win)
-                       tp->window_clamp = min(tp->window_clamp, app_win);
                tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
        }
 }