pf tests: ensure we don't confuse different ICMP types

When creating a state for ICMP (v4 or v6) packets we only used the ID, which
means that we could confuse different ICMP types. For example, if we allowed
neighbour discovery but not ICMPv6 echo requests an ND packet could create a
state that the echo request would match.

Test that this is now fixed.

Reported by:	Enrico Bassetti <e.bassetti@tudelft.nl>
MFC after:	1 day
Sponsored by:	Rubicon Communications, LLC ("Netgate")

(cherry picked from commit b9f0dbc3d006e0b904ee4275d54459f4edd65bb8)

tests/sys/netpfil/pf/Makefile

@@ -16,6 +16,7 @@ ATF_TESTS_SH+=	altq \
 		fragmentation_no_reassembly \
 		get_state \
 		icmp \
+		icmp6 \
 		killstate \
 		macro \
 		map_e \

tests/sys/netpfil/pf/icmp6.sh

@@ -0,0 +1,89 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2024 Rubicon Communications, LLC (Netgate)
+#
+# 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 "zero_id" "cleanup"
+zero_id_head()
+{
+	atf_set descr 'Test ICMPv6 echo with ID 0 keep being blocked'
+	atf_set require.user root
+	atf_set require.progs scapy
+}
+
+zero_id_body()
+{
+	pft_init
+
+	epair=$(vnet_mkepair)
+	ifconfig ${epair}a inet6 2001:db8::2/64 up no_dad
+
+	vnet_mkjail alcatraz ${epair}b
+	jexec alcatraz ifconfig ${epair}b inet6 2001:db8::1/64 up no_dad
+
+	# Sanity check
+	atf_check -s exit:0 -o ignore \
+	    ping -c 1 2001:db8::1
+
+	jexec alcatraz pfctl -e
+	pft_set_rules alcatraz \
+		"set block-policy drop" \
+		"antispoof quick for { egress ${epair}b }" \
+		"block all" \
+		"pass out" \
+		"pass in quick inet6 proto IPV6-ICMP icmp6-type 135" \
+		"pass in quick inet6 proto IPV6-ICMP icmp6-type 136" \
+		"pass out quick inet6 proto IPV6 from self to any"
+
+	# Now we can't ping
+	atf_check -s exit:2 -o ignore \
+	    ping -c 1 2001:db8::1
+
+	# Force neighbour discovery
+	ndp -d 2001:db8::1
+
+	# Verify that we don't confuse echo request with ID 0 for neighbour discovery
+	atf_check -s exit:1 -o ignore \
+	     ${common_dir}/pft_ping.py \
+	         --sendif ${epair}a \
+	         --to 2001:db8::1 \
+	         --replyif ${epair}a
+
+	jexec alcatraz pfctl -ss -vv
+	jexec alcatraz pfctl -sr -vv
+}
+
+zero_id_cleanup()
+{
+	pft_cleanup
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case "zero_id"
+}