Thanks for fixing this Xavier. I had no idea you could use that syntax
to put a time gap between sending packets with nc. Thanks for teaching
me something!

Acked-by: Mark Michelson <[email protected]>

On Mon, Oct 13, 2025 at 9:16 AM Xavier Simonart via dev
<[email protected]> wrote:
>
> When a nc connection is established on client side, the client
> (using -z) was immediately closing the connection (sending FIN/ACK).
> As a result, the server was either sending ACK and FIN/ACK, or
> was also sometimes only sending FIN/ACK.
> Only ACK (and neither SYN/ACK nor FIN/ACK) causes the connection to
> be committed in conntrack.
> Fix this by having the client send a Packet, then wait some time
> before sending FIN/ACK.
>
> Reported-at: https://issues.redhat.com/browse/FDP-1026
> Signed-off-by: Xavier Simonart <[email protected]>
> ---
>  tests/system-ovn.at | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/tests/system-ovn.at b/tests/system-ovn.at
> index df5bd716d..16848ec4a 100644
> --- a/tests/system-ovn.at
> +++ b/tests/system-ovn.at
> @@ -6505,7 +6505,7 @@ NS_CHECK_EXEC([bob1], [ip r d default via 172.16.0.2 
> dev bob1], [0])
>  NS_CHECK_EXEC([bob1], [ip r a default via 172.16.0.3 dev bob1], [0])
>
>  NETNS_DAEMONIZE([bob1], [nc -l -k 8080], [bob1.pid])
> -NS_CHECK_EXEC([alice1], [nc -z 172.16.0.1 8080], [0])
> +NS_CHECK_EXEC([alice1], [(echo "Packet 1"; sleep 1; echo "Packet 2") | nc 
> 172.16.0.1 8080], [0])
>  NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 172.16.0.1 | FORMAT_PING], 
> \
>  [0], [dnl
>  3 packets transmitted, 3 received, 0% packet loss, time 0ms
> @@ -6522,7 +6522,7 @@ check ovn-nbctl --policy="src-ip" lr-route-del R1 
> 10.0.0.0/24 20.0.0.3
>  check ovn-nbctl --wait=hv sync
>  AT_CHECK([ovs-appctl dpctl/flush-conntrack])
>  NETNS_DAEMONIZE([bob1], [nc -l -k 8081], [bob2.pid])
> -NS_CHECK_EXEC([alice1], [nc -z 172.16.0.1 8081], [0])
> +NS_CHECK_EXEC([alice1], [(echo "Packet 1"; sleep 1; echo "Packet 2") | nc 
> 172.16.0.1 8081], [0])
>  NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 172.16.0.1 | FORMAT_PING], 
> \
>  [0], [dnl
>  3 packets transmitted, 3 received, 0% packet loss, time 0ms
> @@ -6737,7 +6737,7 @@ test $(ovs-ofctl dump-flows br-int | grep -c 
> 'table=OFTABLE_ECMP_NH, n_packets')
>  AT_CHECK([ovs-appctl dpctl/flush-conntrack])
>
>  NETNS_DAEMONIZE([bob1], [nc -6 -l -k 8080], [bob1.pid])
> -NS_CHECK_EXEC([alice1], [nc -6 -z fd07::1 8080], [0])
> +NS_CHECK_EXEC([alice1], [(echo "Packet 1"; sleep 1; echo "Packet 2") | nc -6 
> fd07::1 8080], [0])
>  NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 fd07::1 | FORMAT_PING], \
>  [0], [dnl
>  3 packets transmitted, 3 received, 0% packet loss, time 0ms
> @@ -6754,7 +6754,7 @@ check ovn-nbctl --policy="src-ip" lr-route-del R1 
> fd01::/126 fd02::3
>  check ovn-nbctl --wait=hv sync
>  AT_CHECK([ovs-appctl dpctl/flush-conntrack])
>  NETNS_DAEMONIZE([bob1], [nc -6 -l -k 8081], [bob2.pid])
> -NS_CHECK_EXEC([alice1], [nc -6 -z fd07::1 8081], [0])
> +NS_CHECK_EXEC([alice1], [(echo "Packet 1"; sleep 1; echo "Packet 2") | nc -6 
> fd07::1 8081], [0])
>  NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 fd07::1 | FORMAT_PING], \
>  [0], [dnl
>  3 packets transmitted, 3 received, 0% packet loss, time 0ms
> --
> 2.47.1
>
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>

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