[PATCH 5.16 126/126] selftests: netfilter: check stateless nat udp checksum fixup

Greg Kroah-Hartman
2022-02-07T12:03:28Z

From: Florian Westphal <fw@strlen.de>

commit aad51ca71ad83273e8826d6cfdcf53c98748d1fa upstream.

Add a test that sends large udp packet (which is fragmented)
via a stateless nft nat rule, i.e. 'ip saddr set 10.2.3.4'
and check that the datagram is received by peer.

On kernels without
commit 4e1860a38637 ("netfilter: nft_payload: do not update layer 4 checksum when mangling fragments")',
this will fail with:

cmp: EOF on /tmp/tmp.V1q0iXJyQF which is empty
-rw------- 1 root root 4096 Jan 24 22:03 /tmp/tmp.Aaqnq4rBKS
-rw------- 1 root root 0 Jan 24 22:03 /tmp/tmp.V1q0iXJyQF
ERROR: in and output file mismatch when checking udp with stateless nat
FAIL: nftables v1.0.0 (Fearless Fosdick #2)

On patched kernels, this will show:
PASS: IP statless for ns2-PFp89amx

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/netfilter/nft_nat.sh | 152 +++++++++++++++++++++++++++
1 file changed, 152 insertions(+)

--- a/tools/testing/selftests/netfilter/nft_nat.sh
+++ b/tools/testing/selftests/netfilter/nft_nat.sh
@@ -898,6 +898,144 @@ EOF
ip netns exec "$ns0" nft delete table $family nat
}

+test_stateless_nat_ip()
+{
+ local lret=0
+
+ ip netns exec "$ns0" sysctl net.ipv4.conf.veth0.forwarding=1 > /dev/null
+ ip netns exec "$ns0" sysctl net.ipv4.conf.veth1.forwarding=1 > /dev/null
+
+ ip netns exec "$ns2" ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1
+ if [ $? -ne 0 ] ; then
+ echo "ERROR: cannot ping $ns1 from $ns2 before loading stateless rules"
+ return 1
+ fi
+
+ip netns exec "$ns0" nft -f /dev/stdin <<EOF
+table ip stateless {
+ map xlate_in {
+ typeof meta iifname . ip saddr . ip daddr : ip daddr
+ elements = {
+ "veth1" . 10.0.2.99 . 10.0.1.99 : 10.0.2.2,
+ }
+ }
+ map xlate_out {
+ typeof meta iifname . ip saddr . ip daddr : ip daddr
+ elements = {
+ "veth0" . 10.0.1.99 . 10.0.2.2 : 10.0.2.99
+ }
+ }
+
+ chain prerouting {
+ type filter hook prerouting priority -400; policy accept;
+ ip saddr set meta iifname . ip saddr . ip daddr map @xlate_in
+ ip daddr set meta iifname . ip saddr . ip daddr map @xlate_out
+ }
+}
+EOF
+ if [ $? -ne 0 ]; then
+ echo "SKIP: Could not add ip statless rules"
+ return $ksft_skip
+ fi
+
+ reset_counters
+
+ ip netns exec "$ns2" ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1
+ if [ $? -ne 0 ] ; then
+ echo "ERROR: cannot ping $ns1 from $ns2 with stateless rules"
+ lret=1
+ fi
+
+ # ns1 should have seen packets from .2.2, due to stateless rewrite.
+ expect="packets 1 bytes 84"
+ cnt=$(ip netns exec "$ns1" nft list counter inet filter ns0insl | grep -q "$expect")
+ if [ $? -ne 0 ]; then
+ bad_counter "$ns1" ns0insl "$expect" "test_stateless 1"
+ lret=1
+ fi
+
+ for dir in "in" "out" ; do
+ cnt=$(ip netns exec "$ns2" nft list counter inet filter ns1${dir} | grep -q "$expect")
+ if [ $? -ne 0 ]; then
+ bad_counter "$ns2" ns1$dir "$expect" "test_stateless 2"
+ lret=1
+ fi
+ done
+
+ # ns1 should not have seen packets from ns2, due to masquerade
+ expect="packets 0 bytes 0"
+ for dir in "in" "out" ; do
+ cnt=$(ip netns exec "$ns1" nft list counter inet filter ns2${dir} | grep -q "$expect")
+ if [ $? -ne 0 ]; then
+ bad_counter "$ns1" ns0$dir "$expect" "test_stateless 3"
+ lret=1
+ fi
+
+ cnt=$(ip netns exec "$ns0" nft list counter inet filter ns1${dir} | grep -q "$expect")
+ if [ $? -ne 0 ]; then
+ bad_counter "$ns0" ns1$dir "$expect" "test_stateless 4"
+ lret=1
+ fi
+ done
+
+ reset_counters
+
+ socat -h > /dev/null 2>&1
+ if [ $? -ne 0 ];then
+ echo "SKIP: Could not run stateless nat frag test without socat tool"
+ if [ $lret -eq 0 ]; then
+ return $ksft_skip
+ fi
+
+ ip netns exec "$ns0" nft delete table ip stateless
+ return $lret
+ fi
+
+ local tmpfile=$(mktemp)
+ dd if=/dev/urandom of=$tmpfile bs=4096 count=1 2>/dev/null
+
+ local outfile=$(mktemp)
+ ip netns exec "$ns1" timeout 3 socat -u UDP4-RECV:4233 OPEN:$outfile < /dev/null &
+ sc_r=$!
+
+ sleep 1
+ # re-do with large ping -> ip fragmentation
+ ip netns exec "$ns2" timeout 3 socat - UDP4-SENDTO:"10.0.1.99:4233" < "$tmpfile" > /dev/null
+ if [ $? -ne 0 ] ; then
+ echo "ERROR: failed to test udp $ns1 to $ns2 with stateless ip nat" 1>&2
+ lret=1
+ fi
+
+ wait
+
+ cmp "$tmpfile" "$outfile"
+ if [ $? -ne 0 ]; then
+ ls -l "$tmpfile" "$outfile"
+ echo "ERROR: in and output file mismatch when checking udp with stateless nat" 1>&2
+ lret=1
+ fi
+
+ rm -f "$tmpfile" "$outfile"
+
+ # ns1 should have seen packets from 2.2, due to stateless rewrite.
+ expect="packets 3 bytes 4164"
+ cnt=$(ip netns exec "$ns1" nft list counter inet filter ns0insl | grep -q "$expect")
+ if [ $? -ne 0 ]; then
+ bad_counter "$ns1" ns0insl "$expect" "test_stateless 5"
+ lret=1
+ fi
+
+ ip netns exec "$ns0" nft delete table ip stateless
+ if [ $? -ne 0 ]; then
+ echo "ERROR: Could not delete table ip stateless" 1>&2
+ lret=1
+ fi
+
+ test $lret -eq 0 && echo "PASS: IP statless for $ns2"
+
+ return $lret
+}
+
# ip netns exec "$ns0" ping -c 1 -q 10.0.$i.99
for i in 0 1 2; do
ip netns exec ns$i-$sfx nft -f /dev/stdin <<EOF
@@ -964,6 +1102,19 @@ table inet filter {
EOF
done

+# special case for stateless nat check, counter needs to
+# be done before (input) ip defragmentation
+ip netns exec ns1-$sfx nft -f /dev/stdin <<EOF
+table inet filter {
+ counter ns0insl {}
+
+ chain pre {
+ type filter hook prerouting priority -400; policy accept;
+ ip saddr 10.0.2.2 counter name "ns0insl"
+ }
+}
+EOF
+
sleep 3
# test basic connectivity
for i in 1 2; do
@@ -1018,6 +1169,7 @@ $test_inet_nat && test_redirect inet
$test_inet_nat && test_redirect6 inet

test_port_shadowing
+test_stateless_nat_ip

if [ $ret -ne 0 ];then
echo -n "FAIL: "