diff --git a/tests/sys/netpfil/pf/syncookie.sh b/tests/sys/netpfil/pf/syncookie.sh
index 8a4005d0fc6d..d85beac1a4d1 100644
--- a/tests/sys/netpfil/pf/syncookie.sh
+++ b/tests/sys/netpfil/pf/syncookie.sh
@@ -1,176 +1,226 @@
 # $FreeBSD$
 #
 # SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 #
 # Copyright (c) 2021 Modirum MDPay
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1. Redistributions of source code must retain the above copyright
 #    notice, this list of conditions and the following disclaimer.
 # 2. Redistributions in binary form must reproduce the above copyright
 #    notice, this list of conditions and the following disclaimer in the
 #    documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 # ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 # 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.
 
 . $(atf_get_srcdir)/utils.subr
 
 common_dir=$(atf_get_srcdir)/../common
 
 atf_test_case "basic" "cleanup"
 basic_head()
 {
 	atf_set descr 'Basic syncookie test'
 	atf_set require.user root
 }
 
 basic_body()
 {
 	pft_init
 
 	epair=$(vnet_mkepair)
 
 	vnet_mkjail alcatraz ${epair}b
 	jexec alcatraz ifconfig ${epair}b 192.0.2.1/24 up
 	jexec alcatraz /usr/sbin/inetd -p inetd-alcatraz.pid \
 	    $(atf_get_srcdir)/echo_inetd.conf
 
 	ifconfig ${epair}a 192.0.2.2/24 up
 
 	jexec alcatraz pfctl -e
 	pft_set_rules alcatraz \
 		"set syncookies always" \
 		"pass in" \
 		"pass out"
 
 	# Sanity check
 	atf_check -s exit:0 -o ignore ping -c 1 192.0.2.1
 
 	reply=$(echo foo | nc -N -w 5 192.0.2.1 7)
 	if [ "${reply}" != "foo" ];
 	then
 		atf_fail "Failed to connect to syncookie protected echo daemon"
 	fi
 }
 
 basic_cleanup()
 {
 	rm -f inetd-alcatraz.pid
 	pft_cleanup
 }
 
 atf_test_case "forward" "cleanup"
 forward_head()
 {
 	atf_set descr 'Syncookies for forwarded hosts'
 	atf_set require.user root
 }
 
 forward_body()
 {
 	pft_init
 
 	epair_in=$(vnet_mkepair)
 	epair_out=$(vnet_mkepair)
 
 	vnet_mkjail fwd ${epair_in}b ${epair_out}a
 	vnet_mkjail srv ${epair_out}b
 
 	jexec fwd ifconfig ${epair_in}b 192.0.2.1/24 up
 	jexec fwd ifconfig ${epair_out}a 198.51.100.1/24 up
 	jexec fwd sysctl net.inet.ip.forwarding=1
 
 	jexec srv ifconfig ${epair_out}b 198.51.100.2/24 up
 	jexec srv route add default 198.51.100.1
 	jexec srv /usr/sbin/inetd -p inetd-alcatraz.pid \
 	    $(atf_get_srcdir)/echo_inetd.conf
 
 	ifconfig ${epair_in}a 192.0.2.2/24 up
 	route add -net 198.51.100.0/24 192.0.2.1
 
 	jexec fwd pfctl -e
 	pft_set_rules fwd \
 		"set syncookies always" \
 		"pass in" \
 		"pass out"
 
 	# Sanity check
 	atf_check -s exit:0 -o ignore ping -c 1 198.51.100.2
 
 	reply=$(echo foo | nc -N -w 5 198.51.100.2 7)
 	if [ "${reply}" != "foo" ];
 	then
 		atf_fail "Failed to connect to syncookie protected echo daemon"
 	fi
 }
 
 forward_cleanup()
 {
 	rm -f inetd-alcatraz.pid
 	pft_cleanup
 }
 
 atf_test_case "nostate" "cleanup"
 nostate_head()
 {
 	atf_set descr 'Ensure that we do not create until SYN|ACK'
 	atf_set require.user root
 	atf_set require.progs scapy
 }
 
 nostate_body()
 {
 	pft_init
 
 	epair=$(vnet_mkepair)
 	ifconfig ${epair}a 192.0.2.2/24 up
 
 	vnet_mkjail alcatraz ${epair}b
 	jexec alcatraz ifconfig ${epair}b 192.0.2.1/24 up
 
 	jexec alcatraz pfctl -e
 	pft_set_rules alcatraz \
 		"set syncookies always" \
 		"pass in" \
 		"pass out"
 
 	# Sanity check
 	atf_check -s exit:0 -o ignore ping -c 1 192.0.2.1
 
 	# Now syn flood to create many states
 	${common_dir}/pft_synflood.py \
 		--sendif ${epair}a \
 		--to 192.0.2.2 \
 		--count 20
 
 	states=$(jexec alcatraz pfctl -ss | grep tcp)
 	if [ -n "$states" ];
 	then
 		echo "$states"
 		atf_fail "Found unexpected state"
 	fi
 }
 
 nostate_cleanup()
 {
 	pft_cleanup
 }
 
+atf_test_case "adaptive" "cleanup"
+adaptive_head()
+{
+	atf_set descr 'Adaptive mode test'
+	atf_set require.user root
+	atf_set require.progs scapy
+}
+
+adaptive_body()
+{
+	pft_init
+
+	epair=$(vnet_mkepair)
+	ifconfig ${epair}a 192.0.2.2/24 up
+
+	vnet_mkjail alcatraz ${epair}b
+	jexec alcatraz ifconfig ${epair}b 192.0.2.1/24 up
+
+	jexec alcatraz pfctl -e
+	pft_set_rules alcatraz \
+		"set limit states 100" \
+		"set syncookies adaptive (start 10%%, end 5%%)" \
+		"pass in" \
+		"pass out"
+
+	# Sanity check
+	atf_check -s exit:0 -o ignore ping -c 1 192.0.2.1
+
+	# Now syn flood to create many states
+	${common_dir}/pft_synflood.py \
+		--sendif ${epair}a \
+		--to 192.0.2.2 \
+		--count 100
+
+	# Adaptive mode should kick in and stop us from creating more than
+	# about 10 states
+	states=$(jexec alcatraz pfctl -ss | grep tcp | wc -l)
+	if [ "$states" -gt 20 ];
+	then
+		echo "$states"
+		atf_fail "Found unexpected states"
+	fi
+}
+
+adaptive_cleanup()
+{
+	pft_cleanup
+}
+
 atf_init_test_cases()
 {
 	atf_add_test_case "basic"
 	atf_add_test_case "forward"
 	atf_add_test_case "nostate"
+	atf_add_test_case "adaptive"
 }