[TCP]: Limit window scaling if window is clamped.

This small change allows for easy per-route workarounds for broken hosts or
middleboxes that are not compliant with TCP standards for window scaling.
Rather than having to turn off window scaling globally. This patch allows
reducing or disabling window scaling if window clamp is present.

Example: Mark Lord reported a problem with 2.6.17 kernel being unable to
access http://www.everymac.com

# ip route add 216.145.246.23/32 via 10.8.0.1 window 65535

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 507adefbc17cdf18d1b7a814630711fbaca5cf81..b4f3ffe1b3b4423211dd9f4e13e42f3d6ecbe230 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -201,6 +201,7 @@ void tcp_select_initial_window(int __space, __u32 mss,
                 * See RFC1323 for an explanation of the limit to 14 
                 */
                space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
+               space = min_t(u32, space, *window_clamp);
                while (space > 65535 && (*rcv_wscale) < 14) {
                        space >>= 1;
                        (*rcv_wscale)++;