[ovs-dev] [PATCH v2] conntrack: Add a test for IPv4 UDP zero checksum

Paolo Valerio pvalerio at redhat.com
Wed Mar 24 10:47:56 UTC 2021


Aaron Conole <aconole at redhat.com> writes:

> Paolo Valerio <pvalerio at redhat.com> writes:
>
>> Hi Aaron,
>>
>> Aaron Conole <aconole at redhat.com> writes:
>>
>>> Recently, during some conntrack testing a bug was uncovered in a DPDK
>>> PMD, which doesn't support an IPv4 packet with a zero checksum value.
>>> In order to show that the connection tracking code in userspace
>>> supports IPv4 UDP with a zero checksum, add a test case to enforce
>>> this behavior.
>>>
>>> Reported-at: http://mails.dpdk.org/archives/dev/2021-January/198528.html
>>> Reported-by: Paolo Valerio <pvalerio at redhat.com>
>>> Signed-off-by: Aaron Conole <aconole at redhat.com>
>>> ---
>>> Previous version:
>>> https://mail.openvswitch.org/pipermail/ovs-dev/2021-February/380266.html
>>>
>>> v1->v2: - Addressed most of the comments by Flavio & William Tu.
>>>         - Added the 0xffff checksum case
>>>         - Added a bad checksum case
>>>         - For the single instance of "sleep 1," this needs to be retained
>>>           due to the negative test case (we have no WAIT_UNTIL to rely on)
>>>           but there are other instances of sleep 1 throughout the suite,
>>>           so I guess it should be okay.
>>>
>>>  tests/system-traffic.at | 64 +++++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 64 insertions(+)
>>>
>>> diff --git a/tests/system-traffic.at b/tests/system-traffic.at
>>> index fb5b9a36d2..5e51c24760 100644
>>> --- a/tests/system-traffic.at
>>> +++ b/tests/system-traffic.at
>>> @@ -5927,6 +5927,69 @@ ovs-appctl dpif/dump-flows br0
>>>  OVS_TRAFFIC_VSWITCHD_STOP
>>>  AT_CLEANUP
>>>  
>>> +
>>> +AT_SETUP([conntrack - IPv4 UDP zero checksum])
>>
>> Don't know if this second new line up here was intentional (mixed style
>> in the file).
>> TBH, I have no strong preference about it, I pointed out just in case.
>
> Ugh... every time I rebase some stray new line makes it in.  It's like I
> have a 4 year old in my lap...
>
>>> +dnl This tracks sending zero checksum packets for udp over ipv4
>>> +CHECK_CONNTRACK()
>>> +OVS_TRAFFIC_VSWITCHD_START()
>>> +OVS_CHECK_CT_CLEAR()
>>> +
>>> +ADD_NAMESPACES(at_ns0, at_ns1)
>>> +ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24", "f0:00:00:01:01:01")
>>> +ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24", "f0:00:00:01:01:02")
>>> +dnl setup ct flows
>>> +AT_DATA([flows.txt], [dnl
>>> +table=0,priority=10  ip,udp,ct_state=-trk action=ct(zone=1,table=1)
>>> +table=0,priority=0   action=drop
>>> +table=1,priority=10  ct_state=-est+trk+new,ip,ct_zone=1,in_port=1 action=ct(commit,table=2)
>>> +table=1,priority=10  ct_state=+est-new+trk,ct_zone=1,in_port=1 action=resubmit(,2)
>>> +table=1,priority=0   action=drop
>>> +table=2,priority=10  ct_state=+trk+new,in_port=1 action=2
>>> +table=2,priority=10  ct_state=+trk+est action=2
>>> +])
>>> +
>>> +AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt])
>>> +
>>> +# sending udp pkt with 0000 checksum
>>> +NS_CHECK_EXEC([at_ns0], [$PYTHON3 $srcdir/sendpkt.py p0 f0 00 00 01
>>> 01 02 f0 00 00 01 01 01 08 00 45 00 00 28 00 01 00 00 40 11 64 c0 0a
>>> 01 01 01 0a 01 01 02 04 d2 04 d2 00 14 00 00 aa aa aa aa aa aa aa aa
>>> aa aa aa aa > /dev/null])
>>> +
>>> +OVS_WAIT_UNTIL([ovs-appctl dpctl/dump-conntrack | grep "udp"])
>>> +
>>> +dnl ensure CT picked up the packet
>>> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1)], [0], [dnl
>>> +udp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>)
>>> +])
>>> +
>>> +dnl clear CT tuples
>>> +AT_CHECK([ovs-appctl dpctl/flush-conntrack])
>>> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "udp"], [1])
>>> +
>>> +dnl send UDP with ffff checksum
>>> +NS_CHECK_EXEC([at_ns0], [$PYTHON3 $srcdir/sendpkt.py p0 f0 00 00 01
>>> 01 02 f0 00 00 01 01 01 08 00 45 00 00 40 00 01 00 00 40 11 64 a8 0a
>>> 01 01 01 0a 01 01 02 04 d2 04 d2 00 2c ff ff 00 00 00 00 00 00 00 00
>>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>> 00 00 00 df ed > /dev/null])
>>> +OVS_WAIT_UNTIL([ovs-appctl dpctl/dump-conntrack | grep "udp"])
>>> +
>>> +dnl ensure CT picked up the packet
>>> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | FORMAT_CT(10.1.1)], [0], [dnl
>>> +udp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=<cleared>,dport=<cleared>),reply=(src=10.1.1.2,dst=10.1.1.1,sport=<cleared>,dport=<cleared>)
>>> +])
>>> +
>>> +dnl clear CT tuples
>>> +AT_CHECK([ovs-appctl dpctl/flush-conntrack])
>>> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "udp"], [1])
>>> +
>>> +# sending udp pkt with bad checksum
>>> +NS_CHECK_EXEC([at_ns0], [$PYTHON3 $srcdir/sendpkt.py p0 f0 00 00 01
>>> 01 02 f0 00 00 01 01 01 08 00 45 00 00 28 00 01 00 00 40 11 64 c0 0a
>>> 01 01 01 0a 01 01 02 04 d2 04 d2 00 14 11 11 aa aa aa aa aa aa aa aa
>>> aa aa aa aa > /dev/null])
>>> +
>>> +dnl There isn't anything else to do here but call a sleep... we can't use a WAIT_UNTIL
>>> +dnl because there isn't a condition to check against - we just expect the packet to
>>> +dnl be dropped.
>>> +sleep 1
>>> +
>>> +AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "udp"], [1])
>>> +
>>
>> what if we restrict a little the pattern here?
>
> Sure, but I'm not sure how best to restrict it.  Something like:
>
>   grep "udp,orig=(src=10.1.1.1,dst=10.1.1.2,sport=1234,dport=1234)"
>
> I can do that - it makes the most sense to me.
>

I was going to suggest the src or dst ip, that's even better.

Do you think it's a good idea to do something similar in every
place we have a command sequence like:

AT_CHECK([ovs-appctl dpctl/flush-conntrack])
AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "udp"], [1])

>> In case of kernel dp, considering the sleep, there's a chance an UDP
>> entry (e.g. a DNS query) gets created between the flush and the dump
>> with grep returning 0.
>
> ACK
>
>>
>>> +OVS_TRAFFIC_VSWITCHD_STOP
>>> +AT_CLEANUP
>>> +
>>>  AT_SETUP([conntrack - Multiple ICMP traverse])
>>>  dnl This tracks sending ICMP packets via conntrack multiple times for the
>>>  dnl same packet
>>> -- 
>>> 2.25.4



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