diff --git a/tests/sys/net/Makefile b/tests/sys/net/Makefile
--- a/tests/sys/net/Makefile
+++ b/tests/sys/net/Makefile
@@ -21,8 +21,11 @@
 TEST_METADATA+=	is_exclusive=true
 
 ${PACKAGE}FILES+=	\
+		dhclient_pcp.conf \
+		pcp.py \
 		stp.py
 
+${PACKAGE}FILESMODE_pcp.py=		0555
 ${PACKAGE}FILESMODE_stp.py=		0555
 
 MAN=
diff --git a/tests/sys/net/dhclient_pcp.conf b/tests/sys/net/dhclient_pcp.conf
new file mode 100644
--- /dev/null
+++ b/tests/sys/net/dhclient_pcp.conf
@@ -0,0 +1 @@
+vlan-pcp 6;
diff --git a/tests/sys/net/if_vlan.sh b/tests/sys/net/if_vlan.sh
--- a/tests/sys/net/if_vlan.sh
+++ b/tests/sys/net/if_vlan.sh
@@ -210,6 +210,52 @@
 	vnet_cleanup
 }
 
+atf_test_case "bpf_pcp" "cleanup"
+bpf_pcp_head()
+{
+	atf_set descr 'Set VLAN PCP through BPF'
+	atf_set require.config 'allow_sysctl_side_effects'
+	atf_set require.user root
+	atf_set require.progs scapy
+}
+
+bpf_pcp_body()
+{
+	vnet_init
+
+	epair=$(vnet_mkepair)
+
+	ifconfig ${epair}a up
+
+	vnet_mkjail alcatraz ${epair}b
+	vlan=$(jexec alcatraz ifconfig vlan create)
+	jexec alcatraz ifconfig ${vlan} vlan 42 vlandev ${epair}b
+	jexec alcatraz ifconfig ${vlan} up
+	jexec alcatraz ifconfig ${epair}b up
+
+	sysctl net.link.vlan.mtag_pcp=1
+
+	jexec alcatraz dhclient ${vlan} &
+	atf_check -s exit:1 -o ignore -e ignore $(atf_get_srcdir)/pcp.py \
+		--expect-pcp 6 \
+		--recvif ${epair}a
+
+	jexec alcatraz killall dhclient
+	sleep 1
+
+	jexec alcatraz dhclient -c $(atf_get_srcdir)/dhclient_pcp.conf ${vlan} &
+	atf_check -s exit:0 -o ignore -e ignore $(atf_get_srcdir)/pcp.py \
+		--expect-pcp 6 \
+		--recvif ${epair}a
+}
+
+bpf_pcp_cleanup()
+{
+	sysctl net.link.vlan.mtag_pcp=0
+	jexec alcatraz killall dhclient
+	vnet_cleanup
+}
+
 atf_init_test_cases()
 {
 	atf_add_test_case "basic"
@@ -217,4 +263,5 @@
 	atf_add_test_case "qinq_deep"
 	atf_add_test_case "qinq_legacy"
 	atf_add_test_case "qinq_dot"
+	atf_add_test_case "bpf_pcp"
 }
diff --git a/tests/sys/netpfil/common/sniffer.py b/tests/sys/net/pcp.py
copy from tests/sys/netpfil/common/sniffer.py
copy to tests/sys/net/pcp.py
--- a/tests/sys/netpfil/common/sniffer.py
+++ b/tests/sys/net/pcp.py
@@ -1,8 +1,8 @@
-# $FreeBSD$
+#!/usr/bin/env python3
 #
-# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+# SPDX-License-Identifier: BSD-2-Clause
 #
-# Copyright (c) 2017 Kristof Provost <kp@FreeBSD.org>
+# Copyright (c) 2021 Rubicon Communications, LLC (Netgate).
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -24,31 +24,51 @@
 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 # SUCH DAMAGE.
-#
 
-import threading
+import argparse
+import logging
+logging.getLogger("scapy").setLevel(logging.CRITICAL)
 import scapy.all as sp
+import sys
+import os
+curdir = os.path.dirname(os.path.realpath(__file__))
+netpfil_common = curdir + "/../netpfil/common"
+sys.path.append(netpfil_common)
+from sniffer import Sniffer
+
+def check_pcp(args, packet):
+	vlan = packet.getlayer(sp.Dot1Q)
+
+	if vlan is None:
+		return False
+
+	if not packet.getlayer(sp.BOOTP):
+		return False
+
+	if vlan.prio == int(args.expect_pcp[0]):
+		return True
+
+	return False
+
+def main():
+	parser = argparse.ArgumentParser("pcp.py",
+		description="PCP test tool")
+	parser.add_argument('--recvif', nargs=1,
+		required=True,
+		help='The interface where to look for packets to check')
+	parser.add_argument('--expect-pcp', nargs=1,
+		help='The expected PCP value on VLAN packets')
+
+	args = parser.parse_args()
+
+	sniffer = Sniffer(args, check_pcp, recvif=args.recvif[0], timeout=20)
+
+	sniffer.join()
+
+	if sniffer.foundCorrectPacket:
+		sys.exit(0)
+
+	sys.exit(1)
 
-class Sniffer(threading.Thread):
-	def __init__(self, args, check_function, recvif=None):
-		threading.Thread.__init__(self)
-
-		self._args = args
-		if recvif is not None:
-			self._recvif = recvif
-		else:
-			self._recvif = args.recvif[0]
-		self._check_function = check_function
-		self.foundCorrectPacket = False
-
-		self.start()
-
-	def _checkPacket(self, packet):
-		ret = self._check_function(self._args, packet)
-		if ret:
-			self.foundCorrectPacket = True
-		return ret
-
-	def run(self):
-		self.packets = sp.sniff(iface=self._recvif,
-				stop_filter=self._checkPacket, timeout=3)
+if __name__ == '__main__':
+	main()
diff --git a/tests/sys/netpfil/common/sniffer.py b/tests/sys/netpfil/common/sniffer.py
--- a/tests/sys/netpfil/common/sniffer.py
+++ b/tests/sys/netpfil/common/sniffer.py
@@ -28,12 +28,14 @@
 
 import threading
 import scapy.all as sp
+import sys
 
 class Sniffer(threading.Thread):
-	def __init__(self, args, check_function, recvif=None):
+	def __init__(self, args, check_function, recvif=None, timeout=3):
 		threading.Thread.__init__(self)
 
 		self._args = args
+		self._timeout = timeout
 		if recvif is not None:
 			self._recvif = recvif
 		else:
@@ -50,5 +52,9 @@
 		return ret
 
 	def run(self):
-		self.packets = sp.sniff(iface=self._recvif,
-				stop_filter=self._checkPacket, timeout=3)
+		self.packets = []
+		try:
+			self.packets = sp.sniff(iface=self._recvif,
+					stop_filter=self._checkPacket, timeout=self._timeout)
+		except Exception as e:
+			print(e, file=sys.stderr)