patch-2.4.20 linux-2.4.20/net/ipv6/route.c

• Lines: 73
• Date: Thu Nov 28 15:53:15 2002
• Orig file: linux-2.4.19/net/ipv6/route.c
• Orig date: Fri Dec 21 09:42:05 2001

diff -urN linux-2.4.19/net/ipv6/route.c linux-2.4.20/net/ipv6/route.c
@@ -976,7 +976,11 @@
 		if (net_ratelimit())
 			printk(KERN_DEBUG "rt6_pmtu_discovery: invalid MTU value %d\n",
 			       pmtu);
-		return;
+		/* According to RFC1981, the PMTU is set to the IPv6 minimum
+		   link MTU if the node receives a Packet Too Big message
+		   reporting next-hop MTU that is less than the IPv6 minimum MTU.
+		 */	
+		pmtu = IPV6_MIN_MTU;
 	}
 
 	rt = rt6_lookup(daddr, saddr, dev->ifindex, 0);
@@ -1014,7 +1018,13 @@
 		nrt = rt6_cow(rt, daddr, saddr);
 		if (!nrt->u.dst.error) {
 			nrt->u.dst.pmtu = pmtu;
-			dst_set_expires(&rt->u.dst, ip6_rt_mtu_expires);
+			/* According to RFC 1981, detecting PMTU increase shouldn't be
+			   happened within 5 mins, the recommended timer is 10 mins.
+			   Here this route expiration time is set to ip6_rt_mtu_expires 
+			   which is 10 mins. After 10 mins the decreased pmtu is expired
+			   and detecting PMTU increase will be automatically happened.
+			 */
+			dst_set_expires(&nrt->u.dst, ip6_rt_mtu_expires);
 			nrt->rt6i_flags |= RTF_DYNAMIC|RTF_EXPIRES;
 			dst_release(&nrt->u.dst);
 		}
@@ -1026,7 +1036,7 @@
 		nrt->rt6i_dst.plen = 128;
 		nrt->u.dst.flags |= DST_HOST;
 		nrt->rt6i_nexthop = neigh_clone(rt->rt6i_nexthop);
-		dst_set_expires(&rt->u.dst, ip6_rt_mtu_expires);
+		dst_set_expires(&nrt->u.dst, ip6_rt_mtu_expires);
 		nrt->rt6i_flags |= RTF_DYNAMIC|RTF_CACHE|RTF_EXPIRES;
 		nrt->u.dst.pmtu = pmtu;
 		rt6_ins(nrt);
@@ -1380,15 +1390,32 @@
 static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
 {
 	struct rt6_mtu_change_arg *arg = (struct rt6_mtu_change_arg *) p_arg;
-
+	struct inet6_dev *idev;
 	/* In IPv6 pmtu discovery is not optional,
 	   so that RTAX_MTU lock cannot disable it.
 	   We still use this lock to block changes
 	   caused by addrconf/ndisc.
 	*/
+	idev = __in6_dev_get(arg->dev);
+	/* For administrative MTU increase, there is no way to discover 
+	   IPv6 PMTU increase, so PMTU increase should be updated here.
+	   Since RFC 1981 doesn't include administrative MTU increase
+	   update PMTU increase is a MUST. (i.e. jumbo frame)
+	 */
+	/*
+	   If new MTU is less than route PMTU, this new MTU will be the 
+	   lowest MTU in the path, update the route PMTU to refect PMTU 
+	   decreases; if new MTU is greater than route PMTU, and the 
+	   old MTU is the lowest MTU in the path, update the route PMTU 
+	   to refect the increase. In this case if the other nodes' MTU
+	   also have the lowest MTU, TOO BIG MESSAGE will be lead to 
+	   PMTU discouvery. 
+	 */
 	if (rt->rt6i_dev == arg->dev &&
-	    rt->u.dst.pmtu > arg->mtu &&
-	    !(rt->u.dst.mxlock&(1<<RTAX_MTU)))
+	    !(rt->u.dst.mxlock&(1<<RTAX_MTU)) &&
+	      (rt->u.dst.pmtu > arg->mtu ||
+	       (rt->u.dst.pmtu < arg->mtu &&
+		rt->u.dst.pmtu == idev->cnf.mtu6)))
 		rt->u.dst.pmtu = arg->mtu;
 	rt->u.dst.advmss = max_t(unsigned int, arg->mtu - 60, ip6_rt_min_advmss);
 	if (rt->u.dst.advmss > 65535-20)