From 8cf7d6358cc885ac8fa66bc9942ba511fdc40f42 Mon Sep 17 00:00:00 2001
From: dlg <dlg@openbsd.org>
Date: Fri, 14 Nov 2025 21:47:31 +0000
Subject: [PATCH] only try BIOCLOCK against bpf if tcpdump is using bpf.

fixes tcpdump -r pcapfile, which is getting packets from a file,
not the kernel via bpf.

problem found by bluhm@ and regress tests
ok deraadt@
---
 usr.sbin/tcpdump/privsep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/usr.sbin/tcpdump/privsep.c b/usr.sbin/tcpdump/privsep.c
index 514be6c7e51..5b978e3365f 100644
--- a/usr.sbin/tcpdump/privsep.c
+++ b/usr.sbin/tcpdump/privsep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: privsep.c,v 1.58 2025/11/13 20:46:39 deraadt Exp $	*/
+/*	$OpenBSD: privsep.c,v 1.59 2025/11/14 21:47:31 dlg Exp $	*/
 
 /*
  * Copyright (c) 2003 Can Erkin Acar
@@ -476,7 +476,7 @@ impl_init_done(int fd, int *bpfd)
 	logmsg(LOG_DEBUG, "[priv]: msg PRIV_INIT_DONE received");
 
 	/* lock the descriptor */
-	if (ioctl(*bpfd, BIOCLOCK, NULL) == -1)
+	if (*bpfd != -1 && ioctl(*bpfd, BIOCLOCK, NULL) == -1)
 		err(1, "BIOCLOCK");
 
 	ret = 0;