1 files changed, 21 insertions, 2 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index baa9b289d7ab..844a9ef60dbd 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2232,8 +2232,27 @@ static int rt_fill_info(struct net *net,  __be32 dst, __be32 src,
         error = rt->dst.error;
 
         if (rt_is_input_route(rt)) {
-                if (nla_put_u32(skb, RTA_IIF, rt->rt_iif))
-                        goto nla_put_failure;
+#ifdef CONFIG_IP_MROUTE
+                if (ipv4_is_multicast(dst) && !ipv4_is_local_multicast(dst) &&
+                    IPV4_DEVCONF_ALL(net, MC_FORWARDING)) {
+                        int err = ipmr_get_route(net, skb,
+                                                 fl4->saddr, fl4->daddr,
+                                                 r, nowait);
+                        if (err <= 0) {
+                                if (!nowait) {
+                                        if (err == 0)
+                                                return 0;
+                                        goto nla_put_failure;
+                                } else {
+                                        if (err == -EMSGSIZE)
+                                                goto nla_put_failure;
+                                        error = err;
+                                }
+                        }
+                } else
+#endif
+                        if (nla_put_u32(skb, RTA_IIF, rt->rt_iif))
+                                goto nla_put_failure;
         }
 
         if (rtnl_put_cacheinfo(skb, &rt->dst, 0, expires, error) < 0)