pf tests: Forwarding syncookie test

Test syncookies on a forwarding host. That is, in a setup where the
machine (or vnet) running pf is not the same as the machine (or vnet)
running the server it's protecting.

MFC after:	1 week
Sponsored by:	Modirum MDPay
Differential Revision:	https://reviews.freebsd.org/D31141

tests/sys/netpfil/pf/Makefile

@@ -26,6 +26,7 @@ ATF_TESTS_SH+=	altq \
 		set_skip \
 		set_tos \
 		src_track \
+		syncookie \
 		synproxy \
 		table \
 		tos

tests/sys/netpfil/pf/syncookie.sh

@@ -0,0 +1,84 @@
+# $FreeBSD$
+#
+# 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.
+
+. $(atf_get_srcdir)/utils.subr
+
+atf_test_case "forward" "cleanup"
+forward_head()
+{
+	atf_set descr 'Syncookies for forwarded hosts'
+	atf_set require.user root
+}
+
+forward_body()
+{
+	pft_init
+
+	epair_in=$(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_init_test_cases()
+{
+	atf_add_test_case "forward"
+}