From a0478dcafb1cdef899fba2679def53713c919b9f Mon Sep 17 00:00:00 2001
From: Phil Oester <kernel@linuxace.com>
Date: Tue, 4 Jun 2013 05:09:27 +0000
Subject: [PATCH] --- yaml --- r: 377003 b: refs/heads/master c:
 409b545ac10d9548929557a75ad86540f59a2c83 h: refs/heads/master i:   377001:
 487b23886e43e1924204dc187d6e9971a133933b   376999:
 586477df4ed15aa857dc409f2c1729a325e28d73 v: v3

---
 [refs]                          | 2 +-
 trunk/net/netfilter/xt_TCPMSS.c | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 0747381da2c6..f20bf70969db 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 37bc4f8dfa72fb43b84381abca39cfdbbc8ff2df
+refs/heads/master: 409b545ac10d9548929557a75ad86540f59a2c83
diff --git a/trunk/net/netfilter/xt_TCPMSS.c b/trunk/net/netfilter/xt_TCPMSS.c
index a75240f0d42b..afaebc766933 100644
--- a/trunk/net/netfilter/xt_TCPMSS.c
+++ b/trunk/net/netfilter/xt_TCPMSS.c
@@ -125,6 +125,12 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 
 	skb_put(skb, TCPOLEN_MSS);
 
+	/* RFC 879 states that the default MSS is 536 without specific
+	 * knowledge that the destination host is prepared to accept larger.
+	 * Since no MSS was provided, we MUST NOT set a value > 536.
+	 */
+	newmss = min(newmss, (u16)536);
+
 	opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
 	memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));