[PATCH 10/10] [TCP]: Dont over-clamp window in tcp_clamp_window()

[Chris Wright <chrisw@osdl.org>]

-stable review patch.  If anyone has any objections, please let us know.
------------------

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>
---
 net/ipv4/tcp_input.c |    2 --
 1 files changed, 2 deletions(-)

Index: linux-2.6.13.y/net/ipv4/tcp_input.c
===================================================================
--- linux-2.6.13.y.orig/net/ipv4/tcp_input.c
+++ linux-2.6.13.y/net/ipv4/tcp_input.c
@@ -350,8 +350,6 @@ static void tcp_clamp_window(struct sock
 			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);
 	}
 }

--
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