--- sys/netinet/in_mcast.c	2017-04-20 15:01:10.786840000 +0700
+++ sys/netinet/in_mcast.c	2017-06-17 18:24:34.034823000 +0700
@@ -1338,6 +1338,7 @@ static int
 inp_block_unblock_source(struct inpcb *inp, struct sockopt *sopt)
 {
 	struct group_source_req		 gsr;
+	struct rm_priotracker		 in_ifa_tracker;
 	sockunion_t			*gsa, *ssa;
 	struct ifnet			*ifp;
 	struct in_mfilter		*imf;
@@ -1375,9 +1376,11 @@ inp_block_unblock_source(struct inpcb *i
 		ssa->sin.sin_len = sizeof(struct sockaddr_in);
 		ssa->sin.sin_addr = mreqs.imr_sourceaddr;
 
-		if (!in_nullhost(mreqs.imr_interface))
+		if (!in_nullhost(mreqs.imr_interface)) {
+			IN_IFADDR_RLOCK(&in_ifa_tracker);
 			INADDR_TO_IFP(mreqs.imr_interface, ifp);
-
+			IN_IFADDR_RUNLOCK(&in_ifa_tracker);
+		}
 		if (sopt->sopt_name == IP_BLOCK_SOURCE)
 			doblock = 1;
 
@@ -1873,7 +1876,6 @@ inp_getmoptions(struct inpcb *inp, struc
  *
  * Returns NULL if no ifp could be found.
  *
- * SMPng: TODO: Acquire the appropriate locks for INADDR_TO_IFP.
  * FUTURE: Implement IPv4 source-address selection.
  */
 static struct ifnet *
@@ -1891,7 +1893,9 @@ inp_lookup_mcast_ifp(const struct inpcb 
 
 	ifp = NULL;
 	if (!in_nullhost(ina)) {
+		IN_IFADDR_RLOCK(&in_ifa_tracker);
 		INADDR_TO_IFP(ina, ifp);
+		IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 	} else {
 		fibnum = inp ? inp->inp_inc.inc_fibnum : 0;
 		if (fib4_lookup_nh_basic(fibnum, gsin->sin_addr, 0, 0, &nh4)==0)
@@ -2223,6 +2227,7 @@ inp_leave_group(struct inpcb *inp, struc
 {
 	struct group_source_req		 gsr;
 	struct ip_mreq_source		 mreqs;
+	struct rm_priotracker		 in_ifa_tracker;
 	sockunion_t			*gsa, *ssa;
 	struct ifnet			*ifp;
 	struct in_mfilter		*imf;
@@ -2281,9 +2286,11 @@ inp_leave_group(struct inpcb *inp, struc
 		 * XXX NOTE WELL: The RFC 3678 API is preferred because
 		 * using an IPv4 address as a key is racy.
 		 */
-		if (!in_nullhost(mreqs.imr_interface))
+		if (!in_nullhost(mreqs.imr_interface)) {
+			IN_IFADDR_RLOCK(&in_ifa_tracker);
 			INADDR_TO_IFP(mreqs.imr_interface, ifp);
-
+			IN_IFADDR_RUNLOCK(&in_ifa_tracker);
+		}
 		CTR3(KTR_IGMPV3, "%s: imr_interface = 0x%08x, ifp = %p",
 		    __func__, ntohl(mreqs.imr_interface.s_addr), ifp);
 
@@ -2443,6 +2450,7 @@ out_inp_locked:
 static int
 inp_set_multicast_if(struct inpcb *inp, struct sockopt *sopt)
 {
+	struct rm_priotracker	 in_ifa_tracker;
 	struct in_addr		 addr;
 	struct ip_mreqn		 mreqn;
 	struct ifnet		*ifp;
@@ -2481,7 +2489,9 @@ inp_set_multicast_if(struct inpcb *inp, 
 		if (in_nullhost(addr)) {
 			ifp = NULL;
 		} else {
+			IN_IFADDR_RLOCK(&in_ifa_tracker);
 			INADDR_TO_IFP(addr, ifp);
+			IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 			if (ifp == NULL)
 				return (EADDRNOTAVAIL);
 		}