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Date:   Thu, 22 Sep 2022 22:35:02 +0200
From:   netdev@kapio-technology.com
To:     Ido Schimmel <idosch@nvidia.com>
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Subject: Re: [PATCH v5 net-next 6/6] selftests: forwarding: add test of
 MAC-Auth Bypass to locked port tests
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On 2022-09-21 09:15, Ido Schimmel wrote:
> 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"
> }

Thx, looks good.
I have tried to run the test as far as I can manually, but I don't seem 
to have 'busywait' in the system, which tc_check_packets() depends on, 
and I couldn't find any 'busywait' in Buildroot.