Re: [PATCH v5 net-next 6/6] selftests: forwarding: add test of MAC-Auth Bypass to locked port tests

Ido Schimmel
2022-09-21T07:17:14Z

On Tue, Sep 20, 2022 at 11:29:12PM +0200, netdev@kapio-technology.com wrote:
> I have made a blackhole selftest, which looks like this:
>
> test_blackhole_fdb()
> {
> RET=0
>
> check_blackhole_fdb_support || return 0
>
> tcpdump_start $h2
> $MZ $h1 -q -t udp -a $h1 -b $h2

I don't think you can give an interface name to '-a' and '-b'?

> tcpdump_stop
> tcpdump_show | grep -q udp
> check_err $? "test_blackhole_fdb: No packet seen on initial"
> tcpdump_cleanup
>
> bridge fdb add `mac_get $h2` dev br0 blackhole
> bridge fdb show dev br0 | grep -q "blackhole"

Make this grep more specific so that we are sure it is the entry user
space installed. Something like this:

bridge fdb get `mac_get $h2` br br0 | grep -q blackhole

> check_err $? "test_blackhole_fdb: No blackhole FDB entry found"
>
> tcpdump_start $h2
> $MZ $h1 -q -t udp -a $h1 -b $h2
> tcpdump_stop
> tcpdump_show | grep -q udp
> check_fail $? "test_blackhole_fdb: packet seen with blackhole fdb
> entry"
> tcpdump_cleanup

The tcpdump filter is not specific enough. It can catch other UDP
packets (e.g., multicast) being received by $h2. Anyway, to be sure the
feature works as expected we need to make sure that the packets are not
even egressing $swp2. Checking that they are not received by $h2 is not
enough. See this (untested) suggestion [1] that uses a tc filter on the
egress of $swp2.

>
> bridge fdb del `mac_get $h2` dev br0 blackhole
> bridge fdb show dev br0 | grep -q "blackhole"
> check_fail $? "test_blackhole_fdb: Blackhole FDB entry not deleted"
>
> tcpdump_start $h2
> $MZ $h1 -q -t udp -a $h1 -b $h2
> tcpdump_stop
> tcpdump_show | grep -q udp
> check_err $? "test_blackhole_fdb: No packet seen after removing
> blackhole FDB entry"
> tcpdump_cleanup
>
> log_test "Blackhole FDB entry test"
> }
>
> the setup is simple and is the same as in bridge_sticky_fdb.sh.
>
> Does the test look sound or is there obvious mistakes?

[1]
blackhole_fdb()
{
RET=0

tc filter add dev $swp2 egress protocol ip pref 1 handle 1 flower \
dst_ip 192.0.2.2 ip_proto udp dst_port 12345 action pass

$MZ $h1 -c 1 -p 128 -t udp "sp=54321,dp=12345" \
-a own -b `mac_get $h2` -A 192.0.2.1 -B 192.0.2.2 -q

tc_check_packets "dev $swp2 egress" 1 1
check_err $? "Packet not seen on egress before adding blackhole entry"

bridge fdb add `mac_get $h2` dev br0 blackhole
bridge fdb get `mac_get $h2` br br0 | grep -q blackhole
check_err $? "Blackhole entry not found"

$MZ $h1 -c 1 -p 128 -t udp "sp=54321,dp=12345" \
-a own -b `mac_get $h2` -A 192.0.2.1 -B 192.0.2.2 -q

tc_check_packets "dev $swp2 egress" 1 1
check_err $? "Packet seen on egress after adding blackhole entry"

# Check blackhole entries can be replaced.
bridge fdb replace `mac_get $h2` dev $swp2 master static
bridge fdb get `mac_get $h2` br br0 | grep -q blackhole
check_fail $? "Blackhole entry found after replacement"

$MZ $h1 -c 1 -p 128 -t udp "sp=54321,dp=12345" \
-a own -b `mac_get $h2` -A 192.0.2.1 -B 192.0.2.2 -q

tc_check_packets "dev $swp2 egress" 1 2
check_err $? "Packet not seen on egress after replacing blackhole entry"

bridge fdb del `mac_get $h2` dev $swp2 master static
tc filter del dev $swp2 egress protocol ip pref 1 handle 1 flower

log_test "Blackhole FDB entry"
}