ipv6: Handle all fib6_nh in a nexthop in rt6_device_match

Add a hook in rt6_device_match to handle nexthop struct in a fib6_info.
The new rt6_nh_dev_match uses nexthop_for_each_fib6_nh to walk each
fib6_nh in a nexthop and call __rt6_device_match. On match,
rt6_nh_dev_match returns the fib6_nh and rt6_device_match uses it to
setup fib6_result.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -490,6 +490,45 @@ static bool __rt6_device_match(struct net *net, const struct fib6_nh *nh,
 	return false;
 }
 
+struct fib6_nh_dm_arg {
+	struct net		*net;
+	const struct in6_addr	*saddr;
+	int			oif;
+	int			flags;
+	struct fib6_nh		*nh;
+};
+
+static int __rt6_nh_dev_match(struct fib6_nh *nh, void *_arg)
+{
+	struct fib6_nh_dm_arg *arg = _arg;
+
+	arg->nh = nh;
+	return __rt6_device_match(arg->net, nh, arg->saddr, arg->oif,
+				  arg->flags);
+}
+
+/* returns fib6_nh from nexthop or NULL */
+static struct fib6_nh *rt6_nh_dev_match(struct net *net, struct nexthop *nh,
+					struct fib6_result *res,
+					const struct in6_addr *saddr,
+					int oif, int flags)
+{
+	struct fib6_nh_dm_arg arg = {
+		.net   = net,
+		.saddr = saddr,
+		.oif   = oif,
+		.flags = flags,
+	};
+
+	if (nexthop_is_blackhole(nh))
+		return NULL;
+
+	if (nexthop_for_each_fib6_nh(nh, __rt6_nh_dev_match, &arg))
+		return arg.nh;
+
+	return NULL;
+}
+
 static void rt6_device_match(struct net *net, struct fib6_result *res,
 			     const struct in6_addr *saddr, int oif, int flags)
 {
@@ -510,8 +549,19 @@ static void rt6_device_match(struct net *net, struct fib6_result *res,
 	}
 
 	for (spf6i = f6i; spf6i; spf6i = rcu_dereference(spf6i->fib6_next)) {
-		nh = spf6i->fib6_nh;
-		if (__rt6_device_match(net, nh, saddr, oif, flags)) {
+		bool matched = false;
+
+		if (unlikely(spf6i->nh)) {
+			nh = rt6_nh_dev_match(net, spf6i->nh, res, saddr,
+					      oif, flags);
+			if (nh)
+				matched = true;
+		} else {
+			nh = spf6i->fib6_nh;
+			if (__rt6_device_match(net, nh, saddr, oif, flags))
+				matched = true;
+		}
+		if (matched) {
 			res->f6i = spf6i;
 			goto out;
 		}