--- zzzz-none-000/linux-2.4.17/net/ipv4/netfilter/ipt_TCPMSS.c	2001-12-21 17:42:05.000000000 +0000
+++ sangam-fb-322/linux-2.4.17/net/ipv4/netfilter/ipt_TCPMSS.c	2004-11-24 13:22:08.000000000 +0000
@@ -45,7 +45,7 @@
 	const struct ipt_tcpmss_info *tcpmssinfo = targinfo;
 	struct tcphdr *tcph;
 	struct iphdr *iph;
-	u_int16_t tcplen, newtotlen, oldval, newmss;
+	u_int16_t tcplen, newtotlen, oldval, newmss, srcmss;
 	unsigned int i;
 	u_int8_t *opt;
 
@@ -93,6 +93,9 @@
 		}
 
 		newmss = (*pskb)->dst->pmtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
+		srcmss = in->mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
+		if(srcmss < newmss)
+			newmss = srcmss;
 	} else
 		newmss = tcpmssinfo->mss;