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>

1 files changed, 96 insertions, 79 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index ad2bcf1b69ae..2a86c8951dcd 100644
--- 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;