ipv6: Make icmp route lookup code a bit clearer.

The route lookup code in icmpv6_send() is slightly tricky as a result of
having to handle all of the requirements of RFC 4301 host relookups.

Pull the route resolution into a seperate function, so that the error
handling and route reference counting is hopefully easier to see and
contained wholly within this new routine.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 66 insertions, 51 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index a31d91b04c8..e332bae104e 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -300,6 +300,70 @@ static void mip6_addr_swap(struct sk_buff *skb)
 static inline void mip6_addr_swap(struct sk_buff *skb) {}
 #endif
 
+static struct dst_entry *icmpv6_route_lookup(struct net *net, struct sk_buff *skb,
+                                             struct sock *sk, struct flowi *fl)
+{
+        struct dst_entry *dst, *dst2;
+        struct flowi fl2;
+        int err;
+
+        err = ip6_dst_lookup(sk, &dst, fl);
+        if (err)
+                return ERR_PTR(err);
+
+        /*
+         * We won't send icmp if the destination is known
+         * anycast.
+         */
+        if (((struct rt6_info *)dst)->rt6i_flags & RTF_ANYCAST) {
+                LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: acast source\n");
+                dst_release(dst);
+                return ERR_PTR(-EINVAL);
+        }
+
+        /* No need to clone since we're just using its address. */
+        dst2 = dst;
+
+        err = xfrm_lookup(net, &dst, fl, sk, 0);
+        switch (err) {
+        case 0:
+                if (dst != dst2)
+                        return dst;
+                break;
+        case -EPERM:
+                dst = NULL;
+                break;
+        default:
+                return ERR_PTR(err);
+        }
+
+        err = xfrm_decode_session_reverse(skb, &fl2, AF_INET6);
+        if (err)
+                goto relookup_failed;
+
+        err = ip6_dst_lookup(sk, &dst2, &fl2);
+        if (err)
+                goto relookup_failed;
+
+        err = xfrm_lookup(net, &dst2, &fl2, sk, XFRM_LOOKUP_ICMP);
+        switch (err) {
+        case 0:
+                dst_release(dst);
+                dst = dst2;
+                break;
+        case -EPERM:
+                dst_release(dst);
+                return ERR_PTR(err);
+        default:
+                goto relookup_failed;
+        }
+
+relookup_failed:
+        if (dst)
+                return dst;
+        return ERR_PTR(err);
+}
+
 /*
  *      Send an ICMP message in response to a packet in error
  */
@@ -312,10 +376,8 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 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;
@@ -408,57 +470,10 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
         if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst))
                 fl.oif = np->mcast_oif;
 
-        err = ip6_dst_lookup(sk, &dst, &fl);
-        if (err)
-                goto out;
-
-        /*
-         * We won't send icmp if the destination is known
-         * anycast.
-         */
-        if (((struct rt6_info *)dst)->rt6i_flags & RTF_ANYCAST) {
-                LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: acast source\n");
-                goto out_dst_release;
-        }
-
-        /* No need to clone since we're just using its address. */
-        dst2 = dst;
-
-        err = xfrm_lookup(net, &dst, &fl, sk, 0);
-        switch (err) {
-        case 0:
-                if (dst != dst2)
-                        goto route_done;
-                break;
-        case -EPERM:
-                dst = NULL;
-                break;
-        default:
+        dst = icmpv6_route_lookup(net, skb, sk, &fl);
+        if (IS_ERR(dst))
                 goto out;
-        }
-
-        if (xfrm_decode_session_reverse(skb, &fl2, AF_INET6))
-                goto relookup_failed;
-
-        if (ip6_dst_lookup(sk, &dst2, &fl2))
-                goto relookup_failed;
-
-        err = xfrm_lookup(net, &dst2, &fl2, sk, XFRM_LOOKUP_ICMP);
-        switch (err) {
-        case 0:
-                dst_release(dst);
-                dst = dst2;
-                break;
-        case -EPERM:
-                goto out_dst_release;
-        default:
-relookup_failed:
-                if (!dst)
-                        goto out;
-                break;
-        }
 
-route_done:
         if (ipv6_addr_is_multicast(&fl.fl6_dst))
                 hlimit = np->mcast_hops;
         else