ipv6: introduce ip6_rt_put()

As suggested by Eric, we could introduce a helper function
for ipv6 too, to avoid checking if rt is NULL before
dst_release().

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -213,6 +213,15 @@ static inline void rt6_set_from(struct rt6_info *rt, struct rt6_info *from)
 	dst_hold(new);
 }
 
+static inline void ip6_rt_put(struct rt6_info *rt)
+{
+	/* dst_release() accepts a NULL parameter.
+	 * We rely on dst being first structure in struct rt6_info
+	 */
+	BUILD_BUG_ON(offsetof(struct rt6_info, dst) != 0);
+	dst_release(&rt->dst);
+}
+
 struct fib6_walker_t {
 	struct list_head lh;
 	struct fib6_node *root, *node;

net/ipv6/addrconf.c

@@ -699,7 +699,7 @@ void inet6_ifa_finish_destroy(struct inet6_ifaddr *ifp)
 		pr_warn("Freeing alive inet6 address %p\n", ifp);
 		return;
 	}
-	dst_release(&ifp->rt->dst);
+	ip6_rt_put(ifp->rt);
 
 	kfree_rcu(ifp, rcu);
 }
@@ -951,7 +951,7 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp)
 				rt6_set_expires(rt, expires);
 			}
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	/* clean up prefsrc entries */
@@ -2027,8 +2027,7 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
 			addrconf_prefix_route(&pinfo->prefix, pinfo->prefix_len,
 					      dev, expires, flags);
 		}
-		if (rt)
-			dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	/* Try to figure out our local address for this prefix */

net/ipv6/anycast.c

@@ -84,7 +84,7 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 		rt = rt6_lookup(net, addr, NULL, 0, 0);
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		} else if (ishost) {
 			err = -EADDRNOTAVAIL;
 			goto error;

net/ipv6/fib6_rules.c

@@ -100,7 +100,7 @@ static int fib6_rule_action(struct fib_rule *rule, struct flowi *flp,
 		goto out;
 	}
 again:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	rt = NULL;
 	goto out;
 

net/ipv6/ip6_gre.c

@@ -1069,7 +1069,7 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
 					dev->mtu = IPV6_MIN_MTU;
 			}
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	t->hlen = addend;

net/ipv6/ip6_output.c

@@ -755,7 +755,7 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 		if (err == 0) {
 			IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
 				      IPSTATS_MIB_FRAGOKS);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return 0;
 		}
 
@@ -767,7 +767,7 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 
 		IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
 			      IPSTATS_MIB_FRAGFAILS);
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 		return err;
 
 slow_path_clean:

net/ipv6/ip6_tunnel.c

@@ -663,8 +663,7 @@ ip6ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
 		icmpv6_send(skb2, rel_type, rel_code, rel_info);
 
-		if (rt)
-			dst_release(&rt->dst);
+		ip6_rt_put(rt);
 
 		kfree_skb(skb2);
 	}
@@ -1208,7 +1207,7 @@ static void ip6_tnl_link_config(struct ip6_tnl *t)
 			if (dev->mtu < IPV6_MIN_MTU)
 				dev->mtu = IPV6_MIN_MTU;
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 }
 

net/ipv6/mcast.c

@@ -163,7 +163,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 		rt = rt6_lookup(net, addr, NULL, 0, 0);
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		}
 	} else
 		dev = dev_get_by_index_rcu(net, ifindex);
@@ -260,7 +260,7 @@ static struct inet6_dev *ip6_mc_find_dev_rcu(struct net *net,
 
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		}
 	} else
 		dev = dev_get_by_index_rcu(net, ifindex);

net/ipv6/ndisc.c

@@ -1145,7 +1145,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 			ND_PRINTK(0, err,
 				  "RA: %s got default router without neighbour\n",
 				  __func__);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return;
 		}
 	}
@@ -1170,7 +1170,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 			ND_PRINTK(0, err,
 				  "RA: %s got default router without neighbour\n",
 				  __func__);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return;
 		}
 		neigh->flags |= NTF_ROUTER;
@@ -1326,8 +1326,7 @@ skip_routeinfo:
 		ND_PRINTK(2, warn, "RA: invalid RA options\n");
 	}
 out:
-	if (rt)
-		dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	if (neigh)
 		neigh_release(neigh);
 }

net/ipv6/netfilter/ip6t_rpfilter.c

@@ -67,7 +67,7 @@ static bool rpfilter_lookup_reverse6(const struct sk_buff *skb,
 	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
 		ret = true;
  out:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	return ret;
 }
 

net/ipv6/route.c

@@ -732,7 +732,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 		else
 			rt6_set_expires(rt, jiffies + HZ * lifetime);
 
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 	return 0;
 }
@@ -948,7 +948,7 @@ restart:
 	else
 		goto out2;
 
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	rt = nrt ? : net->ipv6.ip6_null_entry;
 
 	dst_hold(&rt->dst);
@@ -965,7 +965,7 @@ restart:
 	 * Race condition! In the gap, when table->tb6_lock was
 	 * released someone could insert this route.  Relookup.
 	 */
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	goto relookup;
 
 out:
@@ -1576,7 +1576,7 @@ int ip6_route_add(struct fib6_config *cfg)
 				goto out;
 			if (dev) {
 				if (dev != grt->dst.dev) {
-					dst_release(&grt->dst);
+					ip6_rt_put(grt);
 					goto out;
 				}
 			} else {
@@ -1587,7 +1587,7 @@ int ip6_route_add(struct fib6_config *cfg)
 			}
 			if (!(grt->rt6i_flags & RTF_GATEWAY))
 				err = 0;
-			dst_release(&grt->dst);
+			ip6_rt_put(grt);
 
 			if (err)
 				goto out;
@@ -1673,7 +1673,7 @@ static int __ip6_del_rt(struct rt6_info *rt, struct nl_info *info)
 	write_unlock_bh(&table->tb6_lock);
 
 out:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	return err;
 }
 
@@ -2732,7 +2732,7 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr* nlh, void
 
 	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
 	if (!skb) {
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 		err = -ENOBUFS;
 		goto errout;
 	}