--- linux-2.6-2.6.15/net/ipv4/tcp_output.c.orig 2006-01-02 19:21:10.000000000
-0800
+++ linux-2.6-2.6.15/net/ipv4/tcp_output.c 2006-03-09 10:41:46.000000000
-0800
@@ -45,6 +45,11 @@
/* People can turn this off for buggy TCP's found in printers etc. */
int sysctl_tcp_retrans_collapse = 1;
+/* People can turn this on to work with those rare, broken TCPs that
+ * interpret the window field as a signed quantity.
+ */
+int sysctl_tcp_workaround_signed_windows = 0;
+
/* This limits the percentage of the congestion window which we
* will allow a single TSO frame to consume. Building TSO frames
* which are too large can cause TCP streams to be bursty.
@@ -171,12 +176,18 @@ void tcp_select_initial_window(int __spa
space = (space / mss) * mss;
/* NOTE: offering an initial window larger than 32767
- * will break some buggy TCP stacks. We try to be nice.
- * If we are not window scaling, then this truncates
- * our initial window offering to 32k. There should also
- * be a sysctl option to stop being nice.
+ * will break some buggy TCP stacks. If the admin tells us
+ * it is likely we could be speaking with such a buggy stack
+ * we will truncate our initial window offering to 32K-1
+ * unless the remote has sent us a window scaling option,
+ * which we interpret as a sign the remote TCP is not
+ * misinterpreting the window field as a signed quantity.
*/
- (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+ if (sysctl_tcp_workaround_signed_windows)
+ (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+ else
+ (*rcv_wnd) = space;
+
(*rcv_wscale) = 0;
if (wscale_ok) {
/* Set window scaling on max possible window
@@ -235,7 +246,7 @@ static __inline__ u16 tcp_select_window(
/* Make sure we do not exceed the maximum possible
* scaled window.
*/
- if (!tp->rx_opt.rcv_wscale)
+ if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
new_win = min(new_win, MAX_TCP_WINDOW);
else
new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
--- linux-2.6-2.6.15/include/net/tcp.h.orig 2006-02-28 13:40:33.000000000
-0800
+++ linux-2.6-2.6.15/include/net/tcp.h 2006-03-09 10:34:40.000000000 -0800
@@ -219,6 +219,7 @@ extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
extern int sysctl_tcp_abc;
+extern int sysctl_tcp_workaround_signed_windows;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
--- linux-2.6-2.6.15/include/linux/sysctl.h.orig 2006-02-28
13:40:46.000000000 -0800
+++ linux-2.6-2.6.15/include/linux/sysctl.h 2006-03-09 10:35:06.000000000
-0800
@@ -390,6 +390,7 @@ enum
NET_IPV4_ICMP_ERRORS_USE_INBOUND_IFADDR=109,
NET_TCP_CONG_CONTROL=110,
NET_TCP_ABC=111,
+ NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=112,
};
enum {
--- linux-2.6-2.6.15/net/ipv4/sysctl_net_ipv4.c.orig 2006-03-01
17:45:46.000000000 -0800
+++ linux-2.6-2.6.15/net/ipv4/sysctl_net_ipv4.c 2006-03-09 10:35:43.000000000
-0800
@@ -653,7 +653,14 @@ ctl_table ipv4_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
-
+ {
+ .ctl_name = NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS,
+ .procname = "tcp_workaround_signed_windows",
+ .data = &sysctl_tcp_workaround_signed_windows,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec
+ },
{ .ctl_name = 0 }
};
--- linux-2.6-2.6.15/Documentation/networking/ip-sysctl.txt.orig
2006-01-02 19:21:10.000000000 -0800
+++ linux-2.6-2.6.15/Documentation/networking/ip-sysctl.txt 2006-03-09
10:36:18.000000000 -0800
@@ -332,6 +332,13 @@ somaxconn - INTEGER
Defaults to 128. See also tcp_max_syn_backlog for additional tuning
for TCP sockets.
+tcp_workaround_signed_windows - BOOLEAN
+ If set, assume no receipt of a window scaling option means the
+ remote TCP is broken and treats the window as a signed quantity.
+ If unset, assume the remote TCP is not broken even if we do
+ not receive a window scaling option from them.
+ Default: 0
+
IP Variables:
ip_local_port_range - 2 INTEGERS
-
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