selftests: netfilter: add fib test case

There is a bug report on netfilter.org bugzilla pointing to fib
expression dropping ipv6 DAD packets.

Add a test case that demonstrates this problem.

Next patch excludes icmpv6 packets coming from any to linklocal.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

tools/testing/selftests/netfilter/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for netfilter selftests
 
-TEST_PROGS := nft_trans_stress.sh nft_nat.sh bridge_brouter.sh \
+TEST_PROGS := nft_trans_stress.sh nft_fib.sh nft_nat.sh bridge_brouter.sh \
 	conntrack_icmp_related.sh nft_flowtable.sh ipvs.sh \
 	nft_concat_range.sh nft_conntrack_helper.sh \
 	nft_queue.sh nft_meta.sh nf_nat_edemux.sh \

tools/testing/selftests/netfilter/nft_fib.sh

+#!/bin/bash
+#
+# This tests the fib expression.
+#
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+ret=0
+
+sfx=$(mktemp -u "XXXXXXXX")
+ns1="ns1-$sfx"
+ns2="ns2-$sfx"
+nsrouter="nsrouter-$sfx"
+timeout=4
+
+log_netns=$(sysctl -n net.netfilter.nf_log_all_netns)
+
+cleanup()
+{
+	ip netns del ${ns1}
+	ip netns del ${ns2}
+	ip netns del ${nsrouter}
+
+	[ $log_netns -eq 0 ] && sysctl -q net.netfilter.nf_log_all_netns=$log_netns
+}
+
+nft --version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without nft tool"
+	exit $ksft_skip
+fi
+
+ip -Version > /dev/null 2>&1
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not run test without ip tool"
+	exit $ksft_skip
+fi
+
+ip netns add ${nsrouter}
+if [ $? -ne 0 ];then
+	echo "SKIP: Could not create net namespace"
+	exit $ksft_skip
+fi
+
+trap cleanup EXIT
+
+dmesg | grep -q ' nft_rpfilter: '
+if [ $? -eq 0 ]; then
+	dmesg -c | grep ' nft_rpfilter: '
+	echo "WARN: a previous test run has failed" 1>&2
+fi
+
+sysctl -q net.netfilter.nf_log_all_netns=1
+ip netns add ${ns1}
+ip netns add ${ns2}
+
+load_ruleset() {
+	local netns=$1
+
+ip netns exec ${netns} nft -f /dev/stdin <<EOF
+table inet filter {
+	chain prerouting {
+		type filter hook prerouting priority 0; policy accept;
+	        fib saddr . iif oif missing counter log prefix "$netns nft_rpfilter: " drop
+	}
+}
+EOF
+}
+
+load_ruleset_count() {
+	local netns=$1
+
+ip netns exec ${netns} nft -f /dev/stdin <<EOF
+table inet filter {
+	chain prerouting {
+		type filter hook prerouting priority 0; policy accept;
+		ip daddr 1.1.1.1 fib saddr . iif oif missing counter drop
+		ip6 daddr 1c3::c01d fib saddr . iif oif missing counter drop
+	}
+}
+EOF
+}
+
+check_drops() {
+	dmesg | grep -q ' nft_rpfilter: '
+	if [ $? -eq 0 ]; then
+		dmesg | grep ' nft_rpfilter: '
+		echo "FAIL: rpfilter did drop packets"
+		return 1
+	fi
+
+	return 0
+}
+
+check_fib_counter() {
+	local want=$1
+	local ns=$2
+	local address=$3
+
+	line=$(ip netns exec ${ns} nft list table inet filter | grep 'fib saddr . iif' | grep $address | grep "packets $want" )
+	ret=$?
+
+	if [ $ret -ne 0 ];then
+		echo "Netns $ns fib counter doesn't match expected packet count of $want for $address" 1>&2
+		ip netns exec ${ns} nft list table inet filter
+		return 1
+	fi
+
+	if [ $want -gt 0 ]; then
+		echo "PASS: fib expression did drop packets for $address"
+	fi
+
+	return 0
+}
+
+load_ruleset ${nsrouter}
+load_ruleset ${ns1}
+load_ruleset ${ns2}
+
+ip link add veth0 netns ${nsrouter} type veth peer name eth0 netns ${ns1} > /dev/null 2>&1
+if [ $? -ne 0 ];then
+    echo "SKIP: No virtual ethernet pair device support in kernel"
+    exit $ksft_skip
+fi
+ip link add veth1 netns ${nsrouter} type veth peer name eth0 netns ${ns2}
+
+ip -net ${nsrouter} link set lo up
+ip -net ${nsrouter} link set veth0 up
+ip -net ${nsrouter} addr add 10.0.1.1/24 dev veth0
+ip -net ${nsrouter} addr add dead:1::1/64 dev veth0
+
+ip -net ${nsrouter} link set veth1 up
+ip -net ${nsrouter} addr add 10.0.2.1/24 dev veth1
+ip -net ${nsrouter} addr add dead:2::1/64 dev veth1
+
+ip -net ${ns1} link set lo up
+ip -net ${ns1} link set eth0 up
+
+ip -net ${ns2} link set lo up
+ip -net ${ns2} link set eth0 up
+
+ip -net ${ns1} addr add 10.0.1.99/24 dev eth0
+ip -net ${ns1} addr add dead:1::99/64 dev eth0
+ip -net ${ns1} route add default via 10.0.1.1
+ip -net ${ns1} route add default via dead:1::1
+
+ip -net ${ns2} addr add 10.0.2.99/24 dev eth0
+ip -net ${ns2} addr add dead:2::99/64 dev eth0
+ip -net ${ns2} route add default via 10.0.2.1
+ip -net ${ns2} route add default via dead:2::1
+
+test_ping() {
+  local daddr4=$1
+  local daddr6=$2
+
+  ip netns exec ${ns1} ping -c 1 -q $daddr4 > /dev/null
+  ret=$?
+  if [ $ret -ne 0 ];then
+	check_drops
+	echo "FAIL: ${ns1} cannot reach $daddr4, ret $ret" 1>&2
+	return 1
+  fi
+
+  ip netns exec ${ns1} ping -c 3 -q $daddr6 > /dev/null
+  ret=$?
+  if [ $ret -ne 0 ];then
+	check_drops
+	echo "FAIL: ${ns1} cannot reach $daddr6, ret $ret" 1>&2
+	return 1
+  fi
+
+  return 0
+}
+
+ip netns exec ${nsrouter} sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
+ip netns exec ${nsrouter} sysctl net.ipv4.conf.veth0.forwarding=1 > /dev/null
+ip netns exec ${nsrouter} sysctl net.ipv4.conf.veth1.forwarding=1 > /dev/null
+
+sleep 3
+
+test_ping 10.0.2.1 dead:2::1 || exit 1
+check_drops || exit 1
+
+test_ping 10.0.2.99 dead:2::99 || exit 1
+check_drops || exit 1
+
+echo "PASS: fib expression did not cause unwanted packet drops"
+
+ip netns exec ${nsrouter} nft flush table inet filter
+
+ip -net ${ns1} route del default
+ip -net ${ns1} -6 route del default
+
+ip -net ${ns1} addr del 10.0.1.99/24 dev eth0
+ip -net ${ns1} addr del dead:1::99/64 dev eth0
+
+ip -net ${ns1} addr add 10.0.2.99/24 dev eth0
+ip -net ${ns1} addr add dead:2::99/64 dev eth0
+
+ip -net ${ns1} route add default via 10.0.2.1
+ip -net ${ns1} -6 route add default via dead:2::1
+
+ip -net ${nsrouter} addr add dead:2::1/64 dev veth0
+
+# switch to ruleset that doesn't log, this time
+# its expected that this does drop the packets.
+load_ruleset_count ${nsrouter}
+
+# ns1 has a default route, but nsrouter does not.
+# must not check return value, ping to 1.1.1.1 will
+# fail.
+check_fib_counter 0 ${nsrouter} 1.1.1.1 || exit 1
+check_fib_counter 0 ${nsrouter} 1c3::c01d || exit 1
+
+ip netns exec ${ns1} ping -c 1 -W 1 -q 1.1.1.1 > /dev/null
+check_fib_counter 1 ${nsrouter} 1.1.1.1 || exit 1
+
+sleep 2
+ip netns exec ${ns1} ping -c 3 -q 1c3::c01d > /dev/null
+check_fib_counter 3 ${nsrouter} 1c3::c01d || exit 1
+
+exit 0