diff --git a/sys/net/bpf.h b/sys/net/bpf.h
--- a/sys/net/bpf.h
+++ b/sys/net/bpf.h
@@ -410,11 +410,6 @@
 struct bpf_if;
 CK_LIST_HEAD(bpfd_list, bpf_d);
 
-struct bpf_if_ext {
-	CK_LIST_ENTRY(bpf_if)	bif_next;	/* list of all interfaces */
-	struct bpfd_list	bif_dlist;	/* descriptor list */
-};
-
 void	bpf_bufheld(struct bpf_d *d);
 int	bpf_validate(const struct bpf_insn *, int);
 void	bpf_tap(struct bpf_if *, u_char *, u_int);
@@ -435,12 +430,12 @@
 u_int	bpf_filter(const struct bpf_insn *, u_char *, u_int, u_int);
 
 static __inline bool
-bpf_peers_present(struct bpf_if *bpf)
+bpf_peers_present(const struct bpf_if *bpf)
 {
-	struct bpf_if_ext *ext;
+	const struct bpfd_list *dlist;
 
-	ext = (struct bpf_if_ext *)bpf;
-	return (!CK_LIST_EMPTY(&ext->bif_dlist));
+	dlist = (const struct bpfd_list *)bpf;
+	return (!CK_LIST_EMPTY(dlist));
 }
 
 #define BPF_TAP(_ifp, _pkt, _pktlen)				\
diff --git a/sys/net/bpf.c b/sys/net/bpf.c
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -98,14 +98,11 @@
 
 MALLOC_DEFINE(M_BPF, "BPF", "BPF data");
 
-static const struct bpf_if_ext dead_bpf_if = {
-	.bif_dlist = CK_LIST_HEAD_INITIALIZER()
-};
+static const struct bpfd_list dead_bpf_if = CK_LIST_HEAD_INITIALIZER();
 
 struct bpf_if {
-#define	bif_next	bif_ext.bif_next
-#define	bif_dlist	bif_ext.bif_dlist
-	struct bpf_if_ext bif_ext;	/* public members */
+	struct bpfd_list	bif_dlist;	/* list of all interfaces */
+	CK_LIST_ENTRY(bpf_if)	bif_next;	/* descriptor list */
 	u_int		bif_dlt;	/* link layer type */
 	u_int		bif_hdrlen;	/* length of link header */
 	struct bpfd_list bif_wlist;	/* writer-only list */
@@ -115,7 +112,9 @@
 	struct epoch_context epoch_ctx;
 };
 
-CTASSERT(offsetof(struct bpf_if, bif_ext) == 0);
+/* See bpf_peers_present() in bpf.h. */
+_Static_assert(offsetof(struct bpf_if, bif_dlist) == 0,
+    "bpf_if shall start with bif_dlist");
 
 struct bpf_program_buffer {
 	struct epoch_context	epoch_ctx;