ipv4: Make icmp route lookup code a bit clearer.

The route lookup code in icmp_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>

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index ad2bcf1..2a86c89 100644 (file)
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -369,6 +369,98 @@ out_unlock:
        icmp_xmit_unlock(sk);
 }
 
+static struct rtable *icmp_route_lookup(struct net *net, struct sk_buff *skb_in,
+                                       struct iphdr *iph,
+                                       __be32 saddr, u8 tos,
+                                       int type, int code,
+                                       struct icmp_bxm *param)
+{
+       struct flowi fl = {
+               .fl4_dst = (param->replyopts.srr ?
+                           param->replyopts.faddr : iph->saddr),
+               .fl4_src = saddr,
+               .fl4_tos = RT_TOS(tos),
+               .proto = IPPROTO_ICMP,
+               .fl_icmp_type = type,
+               .fl_icmp_code = code,
+       };
+       struct rtable *rt, *rt2;
+       int err;
+
+       security_skb_classify_flow(skb_in, &fl);
+       err = __ip_route_output_key(net, &rt, &fl);
+       if (err)
+               return ERR_PTR(err);
+
+       /* No need to clone since we're just using its address. */
+       rt2 = rt;
+
+       if (!fl.fl4_src)
+               fl.fl4_src = rt->rt_src;
+
+       err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0);
+       switch (err) {
+       case 0:
+               if (rt != rt2)
+                       return rt;
+               break;
+       case -EPERM:
+               rt = NULL;
+               break;
+       default:
+               return ERR_PTR(err);
+       }
+
+       err = xfrm_decode_session_reverse(skb_in, &fl, AF_INET);
+       if (err)
+               goto relookup_failed;
+
+       if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) {
+               err = __ip_route_output_key(net, &rt2, &fl);
+       } else {
+               struct flowi fl2 = {};
+               unsigned long orefdst;
+
+               fl2.fl4_dst = fl.fl4_src;
+               err = ip_route_output_key(net, &rt2, &fl2);
+               if (err)
+                       goto relookup_failed;
+               /* Ugh! */
+               orefdst = skb_in->_skb_refdst; /* save old refdst */
+               err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src,
+                                    RT_TOS(tos), rt2->dst.dev);
+
+               dst_release(&rt2->dst);
+               rt2 = skb_rtable(skb_in);
+               skb_in->_skb_refdst = orefdst; /* restore old refdst */
+       }
+
+       if (err)
+               goto relookup_failed;
+
+       err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL,
+                         XFRM_LOOKUP_ICMP);
+       switch (err) {
+       case 0:
+               dst_release(&rt->dst);
+               rt = rt2;
+               break;
+       case -EPERM:
+               return ERR_PTR(err);
+       default:
+               if (!rt)
+                       return ERR_PTR(err);
+               break;
+       }
+
+
+       return rt;
+
+relookup_failed:
+       if (rt)
+               return rt;
+       return ERR_PTR(err);
+}
 
 /*
  *     Send an ICMP message in response to a situation
@@ -506,86 +598,11 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
        ipc.opt = &icmp_param.replyopts;
        ipc.tx_flags = 0;
 
-       {
-               struct flowi fl = {
-                       .fl4_dst = icmp_param.replyopts.srr ?
-                                  icmp_param.replyopts.faddr : iph->saddr,
-                       .fl4_src = saddr,
-                       .fl4_tos = RT_TOS(tos),
-                       .proto = IPPROTO_ICMP,
-                       .fl_icmp_type = type,
-                       .fl_icmp_code = code,
-               };
-               int err;
-               struct rtable *rt2;
-
-               security_skb_classify_flow(skb_in, &fl);
-               if (__ip_route_output_key(net, &rt, &fl))
-                       goto out_unlock;
-
-               /* No need to clone since we're just using its address. */
-               rt2 = rt;
-
-               if (!fl.nl_u.ip4_u.saddr)
-                       fl.nl_u.ip4_u.saddr = rt->rt_src;
-
-               err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0);
-               switch (err) {
-               case 0:
-                       if (rt != rt2)
-                               goto route_done;
-                       break;
-               case -EPERM:
-                       rt = NULL;
-                       break;
-               default:
-                       goto out_unlock;
-               }
-
-               if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET))
-                       goto relookup_failed;
-
-               if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL)
-                       err = __ip_route_output_key(net, &rt2, &fl);
-               else {
-                       struct flowi fl2 = {};
-                       unsigned long orefdst;
-
-                       fl2.fl4_dst = fl.fl4_src;
-                       if (ip_route_output_key(net, &rt2, &fl2))
-                               goto relookup_failed;
-
-                       /* Ugh! */
-                       orefdst = skb_in->_skb_refdst; /* save old refdst */
-                       err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src,
-                                            RT_TOS(tos), rt2->dst.dev);
-
-                       dst_release(&rt2->dst);
-                       rt2 = skb_rtable(skb_in);
-                       skb_in->_skb_refdst = orefdst; /* restore old refdst */
-               }
-
-               if (err)
-                       goto relookup_failed;
-
-               err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL,
-                                 XFRM_LOOKUP_ICMP);
-               switch (err) {
-               case 0:
-                       dst_release(&rt->dst);
-                       rt = rt2;
-                       break;
-               case -EPERM:
-                       goto ende;
-               default:
-relookup_failed:
-                       if (!rt)
-                               goto out_unlock;
-                       break;
-               }
-       }
+       rt = icmp_route_lookup(net, skb_in, iph, saddr, tos,
+                              type, code, &icmp_param);
+       if (IS_ERR(rt))
+               goto out_unlock;
 
-route_done:
        if (!icmpv4_xrlim_allow(net, rt, type, code))
                goto ende;