Index: sys/arch/amd64/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/amd64/conf/GENERIC.MP,v
diff -u -p -u -p -r1.16 GENERIC.MP
--- sys/arch/amd64/conf/GENERIC.MP	9 Feb 2021 14:06:19 -0000	1.16
+++ sys/arch/amd64/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -4,6 +4,6 @@ include "arch/amd64/conf/GENERIC"
 
 option	MULTIPROCESSOR
 #option	MP_LOCKDEBUG
-#option	WITNESS
+option	WITNESS
 
 cpu*		at mainbus?
Index: sys/arch/arm64/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/arm64/conf/GENERIC.MP,v
diff -u -p -u -p -r1.5 GENERIC.MP
--- sys/arch/arm64/conf/GENERIC.MP	1 Jul 2018 21:05:07 -0000	1.5
+++ sys/arch/arm64/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -4,6 +4,6 @@ include "arch/arm64/conf/GENERIC"
 
 option	MULTIPROCESSOR
 #option	MP_LOCKDEBUG
-#option	WITNESS
+option	WITNESS
 
 cpu*		at mainbus?
Index: sys/arch/i386/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/i386/conf/GENERIC.MP,v
diff -u -p -u -p -r1.11 GENERIC.MP
--- sys/arch/i386/conf/GENERIC.MP	3 Jun 2018 05:18:33 -0000	1.11
+++ sys/arch/i386/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -7,6 +7,6 @@ include "arch/i386/conf/GENERIC"
 
 option		MULTIPROCESSOR	# Multiple processor support
 #option		MP_LOCKDEBUG
-#option		WITNESS
+option		WITNESS
 
 cpu*		at mainbus?
Index: sys/arch/macppc/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/macppc/conf/GENERIC.MP,v
diff -u -p -u -p -r1.2 GENERIC.MP
--- sys/arch/macppc/conf/GENERIC.MP	15 Apr 2020 08:09:33 -0000	1.2
+++ sys/arch/macppc/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -4,6 +4,6 @@ include "arch/macppc/conf/GENERIC"
 
 option	MULTIPROCESSOR
 #option	MP_LOCKDEBUG
-#option	WITNESS
+option	WITNESS
 
 cpu*	at mainbus?
Index: sys/arch/powerpc64/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/powerpc64/conf/GENERIC.MP,v
diff -u -p -u -p -r1.1 GENERIC.MP
--- sys/arch/powerpc64/conf/GENERIC.MP	21 Jul 2020 21:38:31 -0000	1.1
+++ sys/arch/powerpc64/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -4,6 +4,6 @@ include "arch/powerpc64/conf/GENERIC"
 
 option	MULTIPROCESSOR
 #option	MP_LOCKDEBUG
-#option	WITNESS
+option	WITNESS
 
 cpu*		at mainbus?
Index: sys/arch/riscv64/conf/GENERIC.MP
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/arch/riscv64/conf/GENERIC.MP,v
diff -u -p -u -p -r1.1 GENERIC.MP
--- sys/arch/riscv64/conf/GENERIC.MP	29 Jun 2021 21:27:52 -0000	1.1
+++ sys/arch/riscv64/conf/GENERIC.MP	15 Feb 2024 00:17:33 -0000
@@ -4,6 +4,6 @@ include "arch/riscv64/conf/GENERIC"
 
 option	MULTIPROCESSOR
 #option	MP_LOCKDEBUG
-#option	WITNESS
+option	WITNESS
 
 cpu*		at mainbus?
Index: sys/net/route.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/route.c,v
diff -u -p -u -p -r1.432 route.c
--- sys/net/route.c	13 Feb 2024 12:22:09 -0000	1.432
+++ sys/net/route.c	15 Feb 2024 00:17:25 -0000
@@ -202,7 +202,8 @@ route_init(void)
 }
 
 int
-route_cache(struct route *ro, struct in_addr addr, u_int rtableid)
+route_cache(struct route *ro, struct in_addr dst, const struct in_addr *src,
+    u_int rtableid)
 {
 	u_long gen;
 
@@ -213,28 +214,37 @@ route_cache(struct route *ro, struct in_
 	    ro->ro_generation == gen &&
 	    ro->ro_tableid == rtableid &&
 	    ro->ro_dstsa.sa_family == AF_INET &&
-	    ro->ro_dstsin.sin_addr.s_addr == addr.s_addr) {
-		ipstat_inc(ips_rtcachehit);
-		return (0);
+	    ro->ro_dstsin.sin_addr.s_addr == dst.s_addr) {
+		if (src == NULL ||
+		    !ISSET(ro->ro_rt->rt_flags, RTF_MPATH) ||
+		    (ISSET(ro->ro_flags, RTF_MPATH) &&
+		    ro->ro_srcin.s_addr == src->s_addr)) {
+			ipstat_inc(ips_rtcachehit);
+			return (0);
+		}
 	}
 
 	ipstat_inc(ips_rtcachemiss);
 	rtfree(ro->ro_rt);
-	ro->ro_rt = NULL;
+	memset(ro, 0, sizeof(*ro));
 	ro->ro_generation = gen;
 	ro->ro_tableid = rtableid;
 
-	memset(&ro->ro_dst, 0, sizeof(ro->ro_dst));
 	ro->ro_dstsin.sin_family = AF_INET;
 	ro->ro_dstsin.sin_len = sizeof(struct sockaddr_in);
-	ro->ro_dstsin.sin_addr = addr;
+	ro->ro_dstsin.sin_addr = dst;
+	if (src != NULL) {
+		ro->ro_srcin = *src;
+		SET(ro->ro_flags, RTF_MPATH);
+	}
 
 	return (ESRCH);
 }
 
 #ifdef INET6
 int
-route6_cache(struct route *ro, const struct in6_addr *addr, u_int rtableid)
+route6_cache(struct route *ro, const struct in6_addr *dst,
+    const struct in6_addr *src, u_int rtableid)
 {
 	u_long gen;
 
@@ -245,21 +255,29 @@ route6_cache(struct route *ro, const str
 	    ro->ro_generation == gen &&
 	    ro->ro_tableid == rtableid &&
 	    ro->ro_dstsa.sa_family == AF_INET6 &&
-	    IN6_ARE_ADDR_EQUAL(&ro->ro_dstsin6.sin6_addr, addr)) {
-		ip6stat_inc(ip6s_rtcachehit);
-		return (0);
+	    IN6_ARE_ADDR_EQUAL(&ro->ro_dstsin6.sin6_addr, dst)) {
+		if (src == NULL ||
+		    !ISSET(ro->ro_rt->rt_flags, RTF_MPATH) ||
+		    (ISSET(ro->ro_flags, RTF_MPATH) &&
+		    IN6_ARE_ADDR_EQUAL(&ro->ro_srcin6, src))) {
+			ip6stat_inc(ip6s_rtcachehit);
+			return (0);
+		}
 	}
 
 	ip6stat_inc(ip6s_rtcachemiss);
 	rtfree(ro->ro_rt);
-	ro->ro_rt = NULL;
+	memset(ro, 0, sizeof(*ro));
 	ro->ro_generation = gen;
 	ro->ro_tableid = rtableid;
 
-	memset(&ro->ro_dst, 0, sizeof(ro->ro_dst));
 	ro->ro_dstsin6.sin6_family = AF_INET6;
 	ro->ro_dstsin6.sin6_len = sizeof(struct sockaddr_in6);
-	ro->ro_dstsin6.sin6_addr = *addr;
+	ro->ro_dstsin6.sin6_addr = *dst;
+	if (src != NULL) {
+		ro->ro_srcin6 = *src;
+		SET(ro->ro_flags, RTF_MPATH);
+	}
 
 	return (ESRCH);
 }
Index: sys/net/route.h
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/route.h,v
diff -u -p -u -p -r1.206 route.h
--- sys/net/route.h	13 Feb 2024 12:22:09 -0000	1.206
+++ sys/net/route.h	15 Feb 2024 00:17:25 -0000
@@ -400,6 +400,13 @@ struct route {
 #define ro_dstsa	ro_dst.rod_sa
 #define ro_dstsin	ro_dst.rod_sin
 #define ro_dstsin6	ro_dst.rod_sin6
+	union {
+		struct	in_addr		ros_in;
+		struct	in6_addr	ros_in6;
+	} ro_src;
+#define ro_srcin	ro_src.ros_in
+#define ro_srcin6	ro_src.ros_in6
+	u_int		ro_flags;
 };
 
 #endif /* __BSD_VISIBLE */
@@ -462,8 +469,10 @@ struct if_ieee80211_data;
 struct bfd_config;
 
 void	 route_init(void);
-int	 route_cache(struct route *, struct in_addr, u_int);
-int	 route6_cache(struct route *, const struct in6_addr *, u_int);
+int	 route_cache(struct route *, struct in_addr, const struct in_addr *,
+	    u_int);
+int	 route6_cache(struct route *, const struct in6_addr *,
+	    const struct in6_addr *, u_int);
 void	 rtm_ifchg(struct ifnet *);
 void	 rtm_ifannounce(struct ifnet *, int);
 void	 rtm_bfd(struct bfd_config *);
Index: sys/netinet/in_pcb.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/in_pcb.c,v
diff -u -p -u -p -r1.293 in_pcb.c
--- sys/netinet/in_pcb.c	13 Feb 2024 12:22:09 -0000	1.293
+++ sys/netinet/in_pcb.c	15 Feb 2024 00:17:25 -0000
@@ -919,7 +919,8 @@ in_pcbrtentry(struct inpcb *inp)
 
 	if (inp->inp_faddr.s_addr == INADDR_ANY)
 		return (NULL);
-	if (route_cache(ro, inp->inp_faddr, inp->inp_rtableid)) {
+	if (route_cache(ro, inp->inp_faddr, &inp->inp_laddr,
+	    inp->inp_rtableid)) {
 		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa,
 		    &inp->inp_laddr.s_addr, ro->ro_tableid);
 	}
@@ -982,7 +983,7 @@ in_pcbselsrc(struct in_addr *insrc, stru
 	 * If route is known or can be allocated now,
 	 * our src addr is taken from the i/f, else punt.
 	 */
-	if (route_cache(ro, sin->sin_addr, rtableid)) {
+	if (route_cache(ro, sin->sin_addr, NULL, rtableid)) {
 		/* No route yet, so try to acquire one */
 		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa, NULL, ro->ro_tableid);
 	}
Index: sys/netinet/ip_input.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/ip_input.c,v
diff -u -p -u -p -r1.389 ip_input.c
--- sys/netinet/ip_input.c	13 Feb 2024 12:22:09 -0000	1.389
+++ sys/netinet/ip_input.c	15 Feb 2024 00:17:25 -0000
@@ -1491,7 +1491,7 @@ ip_forward(struct mbuf *m, struct ifnet 
 	}
 
 	ro.ro_rt = NULL;
-	route_cache(&ro, ip->ip_dst, m->m_pkthdr.ph_rtableid);
+	route_cache(&ro, ip->ip_dst, &ip->ip_src, m->m_pkthdr.ph_rtableid);
 	if (!rtisvalid(rt)) {
 		rtfree(rt);
 		rt = rtalloc_mpath(&ro.ro_dstsa, &ip->ip_src.s_addr,
Index: sys/netinet/ip_output.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet/ip_output.c,v
diff -u -p -u -p -r1.395 ip_output.c
--- sys/netinet/ip_output.c	13 Feb 2024 12:22:09 -0000	1.395
+++ sys/netinet/ip_output.c	15 Feb 2024 00:17:25 -0000
@@ -166,7 +166,7 @@ reroute:
 	 * If there is a cached route, check that it is to the same
 	 * destination and is still up.  If not, free it and try again.
 	 */
-	route_cache(ro, ip->ip_dst, m->m_pkthdr.ph_rtableid);
+	route_cache(ro, ip->ip_dst, &ip->ip_src, m->m_pkthdr.ph_rtableid);
 	dst = &ro->ro_dstsin;
 
 	if ((IN_MULTICAST(ip->ip_dst.s_addr) ||
Index: sys/netinet6/in6_pcb.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/in6_pcb.c,v
diff -u -p -u -p -r1.138 in6_pcb.c
--- sys/netinet6/in6_pcb.c	13 Feb 2024 12:22:09 -0000	1.138
+++ sys/netinet6/in6_pcb.c	15 Feb 2024 00:17:25 -0000
@@ -565,7 +565,8 @@ in6_pcbrtentry(struct inpcb *inp)
 
 	if (IN6_IS_ADDR_UNSPECIFIED(&inp->inp_faddr6))
 		return (NULL);
-	if (route6_cache(ro, &inp->inp_faddr6, inp->inp_rtableid)) {
+	if (route6_cache(ro, &inp->inp_faddr6, &inp->inp_laddr6,
+	    inp->inp_rtableid)) {
 		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa,
 		    &inp->inp_laddr6.s6_addr32[0], ro->ro_tableid);
 	}
Index: sys/netinet6/in6_src.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/in6_src.c,v
diff -u -p -u -p -r1.94 in6_src.c
--- sys/netinet6/in6_src.c	13 Feb 2024 12:22:09 -0000	1.94
+++ sys/netinet6/in6_src.c	15 Feb 2024 00:17:25 -0000
@@ -179,8 +179,8 @@ in6_pcbselsrc(const struct in6_addr **in
 	 * If route is known or can be allocated now,
 	 * our src addr is taken from the i/f, else punt.
 	 */
-	if (route6_cache(ro, dst, rtableid)) {
-		ro->ro_rt = rtalloc(&ro->ro_dstsa, RT_RESOLVE, ro->ro_tableid);
+	if (route6_cache(ro, dst, NULL, rtableid)) {
+		ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa, NULL, ro->ro_tableid);
 	}
 
 	/*
@@ -304,7 +304,7 @@ in6_selectroute(const struct in6_addr *d
 	 * a new one.
 	 */
 	if (ro) {
-		if (route6_cache(ro, dst, rtableid)) {
+		if (route6_cache(ro, dst, NULL, rtableid)) {
 			/* No route yet, so try to acquire one */
 			ro->ro_rt = rtalloc_mpath(&ro->ro_dstsa, NULL,
 			    ro->ro_tableid);
Index: sys/netinet6/ip6_forward.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/ip6_forward.c,v
diff -u -p -u -p -r1.114 ip6_forward.c
--- sys/netinet6/ip6_forward.c	13 Feb 2024 12:22:09 -0000	1.114
+++ sys/netinet6/ip6_forward.c	15 Feb 2024 00:17:25 -0000
@@ -166,7 +166,8 @@ reroute:
 #endif /* IPSEC */
 
 	ro.ro_rt = NULL;
-	route6_cache(&ro, &ip6->ip6_dst, m->m_pkthdr.ph_rtableid);
+	route6_cache(&ro, &ip6->ip6_dst, &ip6->ip6_src,
+	    m->m_pkthdr.ph_rtableid);
 	dst = &ro.ro_dstsa;
 	if (!rtisvalid(rt)) {
 		rtfree(rt);
Index: sys/netinet6/ip6_output.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/netinet6/ip6_output.c,v
diff -u -p -u -p -r1.286 ip6_output.c
--- sys/netinet6/ip6_output.c	13 Feb 2024 12:22:09 -0000	1.286
+++ sys/netinet6/ip6_output.c	15 Feb 2024 00:17:25 -0000
@@ -480,7 +480,7 @@ reroute:
 			goto bad;
 		}
 	} else {
-		route6_cache(ro, &ip6->ip6_dst, m->m_pkthdr.ph_rtableid);
+		route6_cache(ro, &ip6->ip6_dst, NULL, m->m_pkthdr.ph_rtableid);
 	}
 
 	if (rt && (rt->rt_flags & RTF_GATEWAY) &&