[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>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 8754568a75d7..76eaeff76f82 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -402,6 +402,7 @@ enum
         NET_IPV4_IPFRAG_MAX_DIST=112,
         NET_TCP_MTU_PROBING=113,
         NET_TCP_BASE_MSS=114,
+        NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=115,
 };
 
 enum {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 16879fa560de..457e224de468 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -224,6 +224,7 @@ extern int sysctl_tcp_tso_win_divisor;
 extern int sysctl_tcp_abc;
 extern int sysctl_tcp_mtu_probing;
 extern int sysctl_tcp_base_mss;
+extern int sysctl_tcp_workaround_signed_windows;
 
 extern atomic_t tcp_memory_allocated;
 extern atomic_t tcp_sockets_allocated;