--- if_ovpn.c.orig	2023-11-10 07:07:53.000000000 +0700
+++ if_ovpn.c	2024-01-19 22:30:53.478336000 +0700
@@ -48,6 +48,7 @@
 #include <sys/socketvar.h>
 #include <sys/sockio.h>
 #include <sys/sysctl.h>
+#include <sys/syslog.h>
 #include <sys/time.h>
 
 #include <machine/atomic.h>
@@ -276,6 +277,12 @@ SYSCTL_INT(_net_link_openvpn, OID_AUTO, netisr_queue,
 	CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(async_netisr_queue), 0,
 	"Use netisr_queue() rather than netisr_dispatch().");
 
+VNET_DEFINE_STATIC(int, debug) = 0;
+#define	V_debug		VNET(debug)
+SYSCTL_INT(_net_link_openvpn, OID_AUTO, debug,
+	CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(debug), 0,
+	"Enable debug log");
+
 static int
 ovpn_peer_compare(struct ovpn_kpeer *a, struct ovpn_kpeer *b)
 {
@@ -1412,7 +1419,10 @@ ovpn_ioctl_get(struct ifnet *ifp, struct ifdrv *ifd)
 		if (len > ifd->ifd_len) {
 			free(packed, M_NVLIST);
 			nvlist_destroy(nvl);
-			return (ENOSPC);
+			if (V_debug)
+			  log(LOG_DEBUG, "if_ovpn: len(%ju) > ifd->ifd_len(%ju)\n",
+			    (uintmax_t)len, (uintmax_t)ifd->ifd_len);
+			return (ENOBUFS);
 		}
 
 		error = copyout(packed, ifd->ifd_data, len);