[IPV4/IPV6]: Take IPsec overhead into account in tunnels

This patch uses dst_mtu instead of dst_pmtu in the various tunnel
implementations.  As it is they simply ignore the IPsec overhead.
This leads to bogus MTU values inside the tunnels.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -511,7 +511,7 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
 
 	/* change mtu on this route */
 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-		if (rel_info > dst_pmtu(skb2->dst)) {
+		if (rel_info > dst_mtu(skb2->dst)) {
 			kfree_skb(skb2);
 			return;
 		}
@@ -764,9 +764,9 @@ static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	df = tiph->frag_off;
 	if (df)
-		mtu = dst_pmtu(&rt->u.dst) - tunnel->hlen;
+		mtu = dst_mtu(&rt->u.dst) - tunnel->hlen;
 	else
-		mtu = skb->dst ? dst_pmtu(skb->dst) : dev->mtu;
+		mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
 
 	if (skb->dst)
 		skb->dst->ops->update_pmtu(skb->dst, mtu);
@@ -785,7 +785,7 @@ static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	else if (skb->protocol == htons(ETH_P_IPV6)) {
 		struct rt6_info *rt6 = (struct rt6_info*)skb->dst;
 
-		if (rt6 && mtu < dst_pmtu(skb->dst) && mtu >= IPV6_MIN_MTU) {
+		if (rt6 && mtu < dst_mtu(skb->dst) && mtu >= IPV6_MIN_MTU) {
 			if ((tunnel->parms.iph.daddr && !MULTICAST(tunnel->parms.iph.daddr)) ||
 			    rt6->rt6i_dst.plen == 128) {
 				rt6->rt6i_flags |= RTF_MODIFIED;

net/ipv4/ipip.c

@@ -436,7 +436,7 @@ static void ipip_err(struct sk_buff *skb, void *__unused)
 
 	/* change mtu on this route */
 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-		if (rel_info > dst_pmtu(skb2->dst)) {
+		if (rel_info > dst_mtu(skb2->dst)) {
 			kfree_skb(skb2);
 			return;
 		}
@@ -569,9 +569,9 @@ static int ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	if (tiph->frag_off)
-		mtu = dst_pmtu(&rt->u.dst) - sizeof(struct iphdr);
+		mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
 	else
-		mtu = skb->dst ? dst_pmtu(skb->dst) : dev->mtu;
+		mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
 
 	if (mtu < 68) {
 		tunnel->stat.collisions++;

net/ipv6/ip6_tunnel.c

@@ -689,14 +689,14 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 			       t->parms.name);
 		goto tx_err_dst_release;
 	}
-	mtu = dst_pmtu(dst) - sizeof (*ipv6h);
+	mtu = dst_mtu(dst) - sizeof (*ipv6h);
 	if (opt) {
 		max_headroom += 8;
 		mtu -= 8;
 	}
 	if (mtu < IPV6_MIN_MTU)
 		mtu = IPV6_MIN_MTU;
-	if (skb->dst && mtu < dst_pmtu(skb->dst)) {
+	if (skb->dst && mtu < dst_mtu(skb->dst)) {
 		struct rt6_info *rt = (struct rt6_info *) skb->dst;
 		rt->rt6i_flags |= RTF_MODIFIED;
 		rt->u.dst.metrics[RTAX_MTU-1] = mtu;

net/ipv6/sit.c

@@ -500,9 +500,9 @@ static int ipip6_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	if (tiph->frag_off)
-		mtu = dst_pmtu(&rt->u.dst) - sizeof(struct iphdr);
+		mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
 	else
-		mtu = skb->dst ? dst_pmtu(skb->dst) : dev->mtu;
+		mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
 
 	if (mtu < 68) {
 		tunnel->stat.collisions++;