On 1/21/26 10:55 AM, Eelco Chaudron wrote:
>
>
> On 20 Jan 2026, at 21:55, Ilya Maximets wrote:
>
>> On 1/20/26 11:17 AM, Eelco Chaudron wrote:
>>> Add the '--len' option to 'ovs-ofctl compose-packet', which
>>> allows extension of the generated packet.
>>>
>>> Fixes: 90b6e83beb60 ("tests: Fix NSH decap header test for real Ethernet
>>> devices.")
>>> Signed-off-by: Eelco Chaudron <[email protected]>
>>> ---
>>> v2: Use packet_expand() so packet length and checksums get
>>> updated.
>>>
>>> tests/system-traffic.at | 4 ++--
>>> utilities/ovs-ofctl.c | 30 +++++++++++++++++++++++++++---
>>> 2 files changed, 29 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/tests/system-traffic.at b/tests/system-traffic.at
>>> index 8f4fdf8b1..71a8afff2 100644
>>> --- a/tests/system-traffic.at
>>> +++ b/tests/system-traffic.at
>>> @@ -9996,12 +9996,12 @@ dnl Send the NSH packet with TCP SYN payload from
>>> p0(at_ns0) interface directed
>>> dnl to p1(at_ns1) interface.
>>> NS_CHECK_EXEC([at_ns0], [$PYTHON3 $srcdir/sendpkt.py p0 \
>>> "$(ovs-ofctl compose-packet --bare 'NSH_HEADER')" \
>>> - "$(ovs-ofctl compose-packet --bare 'TCP_SYN_PKT')"],
>>> + "$(ovs-ofctl compose-packet --len 64 --bare 'TCP_SYN_PKT')"],
>>> [0], [ignore])
>>>
>>> dnl Check the expected de-capsulated TCP packet on the egress interface
>>> OVS_WAIT_UNTIL([ovs-pcap p1.pcap | grep -q \
>>> - "^$(ovs-ofctl compose-packet --bare 'TCP_SYN_PKT')0*\$"])
>>> + "^$(ovs-ofctl compose-packet --len 64 --bare 'TCP_SYN_PKT')\$"])
>>
>> Hrm. More I look at this, more I think we don't need the new option.
>> The 'compose-packet' already adds 64 bytes of payload to normal packets,
>> having an extra --len option feels a little awkward. It doesn't add them
>> here, because it's a SYN packet that is not supposed to carry extra data.
>> The hardware returns some l2 padding, which is not part of the actual
>> packet, so it is fine.
>>
>> What we can do is either:
>>
>> 1. Keep everything as is - maybe add a comment that there is a possibility
>> for extra l2 padding in case of running with a real hardware.
>>
>> 2. Remove the SYN flag and let the TCP packet have the 64 bytes of payload
>> this way.
>
> I do not really have a preference. Maybe 1 and add a comment? For two, people
> might wonder why we do not simulate using a tcp setup packet?
>
> Let me know, and I’ll send a patch adding the comment (although the commit
> message already has it).
I guess, let's defer/drop this change for now. Can revisit later if this
comes up again.
Best regards, Ilya Maximets.
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