[IPSEC]: Add ICMP host relookup support

RFC 4301 requires us to relookup ICMP traffic that does not match any
policies using the reverse of its payload.  This patch implements this
for ICMP traffic that originates from or terminates on localhost.

This is activated on outbound with the new policy flag XFRM_POLICY_ICMP,
and on inbound by the new state flag XFRM_STATE_ICMP.

On inbound the policy check is now performed by the ICMP protocol so
that it can repeat the policy check where necessary.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 56 insertions, 4 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 93c96cf..c0bea7b 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -63,6 +63,7 @@
 #include <net/ip6_route.h>
 #include <net/addrconf.h>
 #include <net/icmp.h>
+#include <net/xfrm.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -86,7 +87,7 @@ static int icmpv6_rcv(struct sk_buff *skb);
 
 static struct inet6_protocol icmpv6_protocol = {
 	.handler	=	icmpv6_rcv,
-	.flags		=	INET6_PROTO_FINAL,
+	.flags		=	INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
 };
 
 static __inline__ int icmpv6_xmit_lock(void)
@@ -310,8 +311,10 @@ void icmpv6_send(struct sk_buff *skb, int type, int code, __u32 info,
 	struct ipv6_pinfo *np;
 	struct in6_addr *saddr = NULL;
 	struct dst_entry *dst;
+	struct dst_entry *dst2;
 	struct icmp6hdr tmp_hdr;
 	struct flowi fl;
+	struct flowi fl2;
 	struct icmpv6_msg msg;
 	int iif = 0;
 	int addr_type = 0;
@@ -418,9 +421,42 @@ void icmpv6_send(struct sk_buff *skb, int type, int code, __u32 info,
 		goto out_dst_release;
 	}
 
-	if ((err = xfrm_lookup(&dst, &fl, sk, 0)) < 0)
+	/* No need to clone since we're just using its address. */
+	dst2 = dst;
+
+	err = xfrm_lookup(&dst, &fl, sk, 0);
+	switch (err) {
+	case 0:
+		if (dst != dst2)
+			goto route_done;
+		break;
+	case -EPERM:
+		dst = NULL;
+		break;
+	default:
+		goto out;
+	}
+
+	if (xfrm_decode_session_reverse(skb, &fl2, AF_INET6))
+		goto out;
+
+	if (ip6_dst_lookup(sk, &dst2, &fl))
 		goto out;
 
+	err = xfrm_lookup(&dst2, &fl, sk, XFRM_LOOKUP_ICMP);
+	if (err == -ENOENT) {
+		if (!dst)
+			goto out;
+		goto route_done;
+	}
+
+	dst_release(dst);
+	dst = dst2;
+
+	if (err)
+		goto out;
+
+route_done:
 	if (ipv6_addr_is_multicast(&fl.fl6_dst))
 		hlimit = np->mcast_hops;
 	else
@@ -608,6 +644,22 @@ static int icmpv6_rcv(struct sk_buff *skb)
 	struct icmp6hdr *hdr;
 	int type;
 
+	if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb) &&
+	    skb->sp->xvec[skb->sp->len - 1]->props.flags & XFRM_STATE_ICMP) {
+		int nh;
+
+		if (!pskb_may_pull(skb, sizeof(*hdr) + sizeof(*orig_hdr)))
+			goto drop_no_count;
+
+		nh = skb_network_offset(skb);
+		skb_set_network_header(skb, sizeof(*hdr));
+
+		if (!xfrm6_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
+			goto drop_no_count;
+
+		skb_set_network_header(skb, nh);
+	}
+
 	ICMP6_INC_STATS_BH(idev, ICMP6_MIB_INMSGS);
 
 	saddr = &ipv6_hdr(skb)->saddr;
@@ -630,8 +682,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
 		}
 	}
 
-	if (!pskb_pull(skb, sizeof(struct icmp6hdr)))
-		goto discard_it;
+	__skb_pull(skb, sizeof(*hdr));
 
 	hdr = icmp6_hdr(skb);
 
@@ -717,6 +768,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
 
 discard_it:
 	ICMP6_INC_STATS_BH(idev, ICMP6_MIB_INERRORS);
+drop_no_count:
 	kfree_skb(skb);
 	return 0;
 }