Index: sys/net/route.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/route.c,v
diff -u -p -u -p -r1.438 route.c
--- sys/net/route.c	3 Jan 2025 21:27:40 -0000	1.438
+++ sys/net/route.c	13 Jan 2025 22:55:12 -0000
@@ -557,7 +557,7 @@ rt_setgwroute(struct rtentry *rt, const 
 	 * If the MTU of next hop is 0, this will reset the MTU of the
 	 * route to run PMTUD again from scratch.
 	 */
-	if (!ISSET(rt->rt_locks, RTV_MTU)) {
+	if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU)) {
 		u_int mtu, nhmtu;
 
 		mtu = atomic_load_int(&rt->rt_mtu);
Index: sys/net/route.h
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/route.h,v
diff -u -p -u -p -r1.211 route.h
--- sys/net/route.h	3 Jan 2025 21:27:40 -0000	1.211
+++ sys/net/route.h	13 Jan 2025 22:55:12 -0000
@@ -38,6 +38,7 @@
 /*
  * Locks used to protect struct members in this file:
  *	I	immutable after creation
+ *	a	atomic operations
  *	N	net lock
  *	X	exclusive net lock, or shared net lock + kernel lock
  *	R	art (rtable) lock
@@ -60,7 +61,7 @@
 struct rt_kmetrics {
 	u_int64_t	rmx_pksent;	/* packets sent using this route */
 	int64_t		rmx_expire;	/* lifetime for route, e.g. redirect */
-	u_int		rmx_locks;	/* Kernel must leave these values */
+	u_int		rmx_locks;	/* [a] Kernel must leave these values */
 	u_int		rmx_mtu;	/* [a] MTU for this path */
 };
 #endif
Index: sys/net/rtsock.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/rtsock.c,v
diff -u -p -u -p -r1.377 rtsock.c
--- sys/net/rtsock.c	9 Jan 2025 18:20:29 -0000	1.377
+++ sys/net/rtsock.c	13 Jan 2025 22:55:12 -0000
@@ -1198,8 +1198,9 @@ change:
 		}
 		if_group_routechange(info->rti_info[RTAX_DST],
 		    info->rti_info[RTAX_NETMASK]);
-		rt->rt_locks &= ~(rtm->rtm_inits);
-		rt->rt_locks |= (rtm->rtm_inits & rtm->rtm_rmx.rmx_locks);
+		atomic_clearbits_int(&rt->rt_locks, rtm->rtm_inits);
+		atomic_setbits_int(&rt->rt_locks,
+		     rtm->rtm_inits & rtm->rtm_rmx.rmx_locks);
 		NET_UNLOCK();
 		break;
 	case RTM_GET:
@@ -1344,7 +1345,7 @@ route_cleargateway(struct rtentry *rt, v
 	struct rtentry *nhrt = arg;
 
 	if (ISSET(rt->rt_flags, RTF_GATEWAY) && rt->rt_gwroute == nhrt &&
-	    !ISSET(rt->rt_locks, RTV_MTU))
+	    !ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU))
 		atomic_store_int(&rt->rt_mtu, 0);
 
 	return (0);
@@ -1420,7 +1421,7 @@ rtm_getmetrics(const struct rtentry *rt,
 	}
 
 	bzero(out, sizeof(*out));
-	out->rmx_locks = in->rmx_locks;
+	out->rmx_locks = atomic_load_int(&in->rmx_locks);
 	out->rmx_mtu = atomic_load_int(&in->rmx_mtu);
 	out->rmx_expire = expire;
 	out->rmx_pksent = in->rmx_pksent;
Index: sys/netinet/ip_icmp.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/ip_icmp.c,v
diff -u -p -u -p -r1.198 ip_icmp.c
--- sys/netinet/ip_icmp.c	3 Jan 2025 21:27:40 -0000	1.198
+++ sys/netinet/ip_icmp.c	13 Jan 2025 22:55:12 -0000
@@ -1054,9 +1054,9 @@ icmp_mtudisc(struct icmp *icp, u_int rta
 	 *	  on a route.  We should be using a separate flag
 	 *	  for the kernel to indicate this.
 	 */
-	if ((rt->rt_locks & RTV_MTU) == 0) {
+	if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU)) {
 		if (mtu < 296 || mtu > ifp->if_mtu)
-			rt->rt_locks |= RTV_MTU;
+			atomic_setbits_int(&rt->rt_locks, RTV_MTU);
 		else if (rtmtu > mtu || rtmtu == 0)
 			atomic_cas_uint(&rt->rt_mtu, rtmtu, mtu);
 	}
@@ -1090,7 +1090,7 @@ icmp_mtudisc_timeout(struct rtentry *rt,
 			(*ctlfunc)(PRC_MTUINC, sintosa(&sin),
 			    rtableid, NULL);
 	} else {
-		if ((rt->rt_locks & RTV_MTU) == 0)
+		if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU))
 			atomic_store_int(&rt->rt_mtu, 0);
 	}
 
Index: sys/netinet/ip_output.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/ip_output.c,v
diff -u -p -u -p -r1.402 ip_output.c
--- sys/netinet/ip_output.c	3 Jan 2025 21:27:40 -0000	1.402
+++ sys/netinet/ip_output.c	13 Jan 2025 22:55:12 -0000
@@ -384,7 +384,7 @@ sendit:
 	 * the route's MTU is locked.
 	 */
 	if ((flags & IP_MTUDISC) && ro && ro->ro_rt &&
-	    (ro->ro_rt->rt_locks & RTV_MTU) == 0)
+	    (!ISSET(atomic_load_int(&ro->ro_rt->rt_locks), RTV_MTU)))
 		ip->ip_off |= htons(IP_DF);
 
 #ifdef IPSEC
@@ -471,7 +471,7 @@ sendit:
 		 */
 		if (rtisvalid(ro->ro_rt) &&
 		    ISSET(ro->ro_rt->rt_flags, RTF_HOST) &&
-		    !(ro->ro_rt->rt_locks & RTV_MTU)) {
+		    !ISSET(atomic_load_int(&ro->ro_rt->rt_locks), RTV_MTU)) {
 			u_int rtmtu;
 
 			rtmtu = atomic_load_int(&ro->ro_rt->rt_mtu);
Index: sys/netinet/tcp_subr.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/tcp_subr.c,v
diff -u -p -u -p -r1.204 tcp_subr.c
--- sys/netinet/tcp_subr.c	3 Jan 2025 17:23:51 -0000	1.204
+++ sys/netinet/tcp_subr.c	13 Jan 2025 22:55:12 -0000
@@ -868,7 +868,8 @@ tcp_mtudisc(struct inpcb *inp, int errno
 
 	rt = in_pcbrtentry(inp);
 	if (rt != NULL) {
-		unsigned int orig_mtulock = (rt->rt_locks & RTV_MTU);
+		unsigned int orig_mtulock =
+		    (atomic_load_int(&rt->rt_locks) & RTV_MTU);
 
 		/*
 		 * If this was not a host route, remove and realloc.
@@ -878,7 +879,7 @@ tcp_mtudisc(struct inpcb *inp, int errno
 			if ((rt = in_pcbrtentry(inp)) == NULL)
 				return;
 		}
-		if (orig_mtulock < (rt->rt_locks & RTV_MTU))
+		if (orig_mtulock < (atomic_load_int(&rt->rt_locks) & RTV_MTU))
 			change = 1;
 	}
 	tcp_mss(tp, -1);
Index: sys/netinet/tcp_timer.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/tcp_timer.c,v
diff -u -p -u -p -r1.80 tcp_timer.c
--- sys/netinet/tcp_timer.c	5 Jan 2025 12:18:48 -0000	1.80
+++ sys/netinet/tcp_timer.c	13 Jan 2025 22:55:12 -0000
@@ -282,7 +282,7 @@ tcp_timer_rexmt(void *arg)
 		rt = in_pcbrtentry(inp);
 		/* Check if path MTU discovery is disabled already */
 		if (rt && (rt->rt_flags & RTF_HOST) &&
-		    (rt->rt_locks & RTV_MTU))
+		    ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU))
 			goto leave;
 
 		rt = NULL;
@@ -303,8 +303,8 @@ tcp_timer_rexmt(void *arg)
 		}
 		if (rt != NULL) {
 			/* Disable path MTU discovery */
-			if ((rt->rt_locks & RTV_MTU) == 0) {
-				rt->rt_locks |= RTV_MTU;
+			if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU)) {
+				atomic_setbits_int(&rt->rt_locks, RTV_MTU);
 				in_rtchange(inp, 0);
 			}
 
Index: sys/netinet6/icmp6.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/icmp6.c,v
diff -u -p -u -p -r1.256 icmp6.c
--- sys/netinet6/icmp6.c	3 Jan 2025 21:27:40 -0000	1.256
+++ sys/netinet6/icmp6.c	13 Jan 2025 22:55:12 -0000
@@ -1016,7 +1016,7 @@ icmp6_mtudisc_update(struct ip6ctlparam 
 	rt = icmp6_mtudisc_clone(&sin6, m->m_pkthdr.ph_rtableid, 0);
 
 	if (rt != NULL && ISSET(rt->rt_flags, RTF_HOST) &&
-	    !(rt->rt_locks & RTV_MTU)) {
+	    !ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU)) {
 		u_int rtmtu;
 
 		rtmtu = atomic_load_int(&rt->rt_mtu);
@@ -1851,7 +1851,7 @@ icmp6_mtudisc_timeout(struct rtentry *rt
 	if ((rt->rt_flags & (RTF_DYNAMIC|RTF_HOST)) == (RTF_DYNAMIC|RTF_HOST)) {
 		rtdeletemsg(rt, ifp, rtableid);
 	} else {
-		if (!(rt->rt_locks & RTV_MTU))
+		if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU))
 			atomic_store_int(&rt->rt_mtu, 0);
 	}
 
Index: sys/netinet6/ip6_output.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/ip6_output.c,v
diff -u -p -u -p -r1.294 ip6_output.c
--- sys/netinet6/ip6_output.c	3 Jan 2025 21:27:40 -0000	1.294
+++ sys/netinet6/ip6_output.c	13 Jan 2025 22:55:12 -0000
@@ -1047,7 +1047,7 @@ ip6_getpmtu(struct rtentry *rt, struct i
 			 * field isn't locked).
 			 */
 			mtu = ifp->if_mtu;
-			if (!(rt->rt_locks & RTV_MTU))
+			if (!ISSET(atomic_load_int(&rt->rt_locks), RTV_MTU))
 				atomic_cas_uint(&rt->rt_mtu, rtmtu, mtu);
 		}
 	} else {