ipv6: Fragment locally generated tunnel-mode IPSec6 packets as needed.

This patch modifies IPsec6 to fragment IPv6 packets that are
locally generated as needed.

This version of the patch only fragments in tunnel mode, so that fragment
headers will not be obscured by ESP in transport mode.
Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_route.h

@@ -164,5 +164,15 @@ static inline int ipv6_unicast_destination(struct sk_buff *skb)
 	return rt->rt6i_flags & RTF_LOCAL;
 }
 
+int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
+
+static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
+{
+	struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+
+	return (np && np->pmtudisc == IPV6_PMTUDISC_PROBE) ?
+	       skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
+}
+
 #endif
 #endif

net/ipv6/ip6_output.c

@@ -56,7 +56,7 @@
 #include <net/checksum.h>
 #include <linux/mroute6.h>
 
-static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
+int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
 
 int __ip6_local_out(struct sk_buff *skb)
 {
@@ -145,14 +145,6 @@ static int ip6_finish_output2(struct sk_buff *skb)
 	return -EINVAL;
 }
 
-static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
-{
-	struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
-
-	return (np && np->pmtudisc == IPV6_PMTUDISC_PROBE) ?
-	       skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
-}
-
 static int ip6_finish_output(struct sk_buff *skb)
 {
 	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
@@ -601,7 +593,7 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 	return offset;
 }
 
-static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
+int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 {
 	struct sk_buff *frag;
 	struct rt6_info *rt = (struct rt6_info*)skb_dst(skb);

net/ipv6/xfrm6_output.c

@@ -17,6 +17,7 @@
 #include <linux/netfilter_ipv6.h>
 #include <net/dst.h>
 #include <net/ipv6.h>
+#include <net/ip6_route.h>
 #include <net/xfrm.h>
 
 int xfrm6_find_1stfragopt(struct xfrm_state *x, struct sk_buff *skb,
@@ -88,8 +89,21 @@ static int xfrm6_output_finish(struct sk_buff *skb)
 	return xfrm_output(skb);
 }
 
+static int __xfrm6_output(struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+	struct xfrm_state *x = dst->xfrm;
+
+	if ((x && x->props.mode == XFRM_MODE_TUNNEL) &&
+	    ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
+		dst_allfrag(skb_dst(skb)))) {
+			return ip6_fragment(skb, xfrm6_output_finish);
+	}
+	return xfrm6_output_finish(skb);
+}
+
 int xfrm6_output(struct sk_buff *skb)
 {
 	return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, skb, NULL,
-		       skb_dst(skb)->dev, xfrm6_output_finish);
+		       skb_dst(skb)->dev, __xfrm6_output);
 }