[TCP]: sysctl to allow TCP window > 32767 sans wscale

Back in the dark ages, we had to be conservative and only allow 15-bit
window fields if the window scale option was not negotiated.  Some
ancient stacks used a signed 16-bit quantity for the window field of
the TCP header and would get confused.

Those days are long gone, so we can use the full 16-bits by default
now.

There is a sysctl added so that we can still interact with such old
stacks

Signed-off-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 1 deletions

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index ebf2e0b363c4..6b6c3adfcf00 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -680,7 +680,14 @@ 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 }
 };