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	28 Jan 2025 15:59:16 -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	28 Jan 2025 15:59:16 -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	28 Jan 2025 15:59:16 -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	28 Jan 2025 15:59:16 -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	28 Jan 2025 15:59:16 -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	28 Jan 2025 15:59:16 -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/if.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/if.c,v
diff -u -p -u -p -r1.725 if.c
--- sys/net/if.c	25 Jan 2025 10:53:36 -0000	1.725
+++ sys/net/if.c	28 Jan 2025 15:59:14 -0000
@@ -975,7 +975,7 @@ if_output_local(struct ifnet *ifp, struc
 
 	ifiq = ifp->if_iqs[flow % ifp->if_niqs];
 
-	return (ifiq_enqueue(ifiq, m) == 0 ? 0 : ENOBUFS);
+	return (ifiq_enqueue_qlim(ifiq, m, 8192) == 0 ? 0 : ENOBUFS);
 }
 
 void
Index: sys/net/ifq.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/ifq.c,v
diff -u -p -u -p -r1.55 ifq.c
--- sys/net/ifq.c	20 Nov 2024 02:18:45 -0000	1.55
+++ sys/net/ifq.c	28 Jan 2025 15:59:14 -0000
@@ -796,9 +796,10 @@ ifiq_add_data(struct ifiqueue *ifiq, str
 }
 
 int
-ifiq_enqueue(struct ifiqueue *ifiq, struct mbuf *m)
+ifiq_enqueue_qlim(struct ifiqueue *ifiq, struct mbuf *m, unsigned int qlim)
 {
 	struct ifnet *ifp = ifiq->ifiq_if;
+	unsigned int len;
 #if NBPFILTER > 0
 	caddr_t if_bpf = ifp->if_bpf;
 #endif
@@ -825,9 +826,21 @@ ifiq_enqueue(struct ifiqueue *ifiq, stru
 	mtx_enter(&ifiq->ifiq_mtx);
 	ifiq->ifiq_packets++;
 	ifiq->ifiq_bytes += m->m_pkthdr.len;
-	ifiq->ifiq_enqueues++;
-	ml_enqueue(&ifiq->ifiq_ml, m);
+
+	if (qlim && ((len = ml_len(&ifiq->ifiq_ml) >= qlim))) {
+		ifiq->ifiq_qdrops++;
+	} else {
+		ifiq->ifiq_enqueues++;
+		ml_enqueue(&ifiq->ifiq_ml, m);
+		m = NULL;
+	}
+
 	mtx_leave(&ifiq->ifiq_mtx);
+
+	if (m) {
+		m_freem(m);
+		return (0);
+	}
 
 	task_add(ifiq->ifiq_softnet, &ifiq->ifiq_task);
 
Index: sys/net/ifq.h
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/net/ifq.h,v
diff -u -p -u -p -r1.42 ifq.h
--- sys/net/ifq.h	20 Nov 2024 02:18:45 -0000	1.42
+++ sys/net/ifq.h	28 Jan 2025 15:59:14 -0000
@@ -488,11 +488,18 @@ ifq_idx(struct ifqueue *ifq, unsigned in
 void		 ifiq_init(struct ifiqueue *, struct ifnet *, unsigned int);
 void		 ifiq_destroy(struct ifiqueue *);
 int		 ifiq_input(struct ifiqueue *, struct mbuf_list *);
-int		 ifiq_enqueue(struct ifiqueue *, struct mbuf *);
+int		 ifiq_enqueue_qlim(struct ifiqueue *, struct mbuf *,
+		     unsigned int);
 void		 ifiq_add_data(struct ifiqueue *, struct if_data *);
 
 #define ifiq_len(_ifiq)		READ_ONCE(ml_len(&(_ifiq)->ifiq_ml))
 #define ifiq_empty(_ifiq)	(ifiq_len(_ifiq) == 0)
+
+static inline int
+ifiq_enqueue(struct ifiqueue *ifiq, struct mbuf *m)
+{
+	return ifiq_enqueue_qlim(ifiq, m, 0);
+}
 
 #endif /* _KERNEL */