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

Paolo Valerio pvalerio at redhat.com
Mon Mar 22 19:51:37 UTC 2021


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.

> +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?

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.


> +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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