Re: [PATCH bpf-next 0/4] monitor network traffic for flaky test cases

[Kui-Feng Lee <sinquersw@gmail.com>]

On 7/15/24 20:25, Stanislav Fomichev wrote:
> On 07/15, Kui-Feng Lee wrote:
>>
>>
>> On 7/15/24 16:56, Martin KaFai Lau wrote:
>>> On 7/15/24 3:07 PM, Kui-Feng Lee wrote:
>>>>
>>>>
>>>> On 7/15/24 14:33, Stanislav Fomichev wrote:
>>>>> On 07/12, Kui-Feng Lee wrote:
>>>>>> Run tcpdump in the background for flaky test cases related to network
>>>>>> features.
>>>>>
>>>>> Have you considered linking against libpcap instead of shelling out
>>>>> to tcpdump? As long as we have this lib installed on the runners
>>>>> (likely?) that should be a bit cleaner than doing tcpdump.. WDYT?
>>>>
>>>> I just checked the script building the root image for vmtest. [1]
>>>> It doesn't install libpcap.
>>>>
>>>> If our approach is to capture the packets in a file, and let developers
>>>> download the file, it would be a simple and straight forward solution.
>>>> If we want a log in text, it would be more complicated to parse
>>>> packets.
>>>>
>>>> Martin & Stanislay,
>>>>
>>>> WDYT about capture packets in a file and using libpcap directly?
>>>> Developers can download the file and parse it with tcpdump locally.
>>>
>>> thinking out loud...
>>>
>>> Re: libpcap (instead of tcpdump) part. I am not very experienced in
>>> libpcap. I don't have a strong preference. I do hope patch 1 could be
>>> more straight forward that no need to use loops and artificial udp
>>> packets to ensure the tcpdump is fully ready to capture. I assume using
>>> libpcap can make this sync part easier/cleaner (pthread_cond?) and not
>>> too much code is needed to use libpcap?
>>
>> Yes, it would be easier and cleaner if we don't parse the payload
>> of packets.
> 
> Yeah, same, no strong preference; was just wondering whether you've
> made a conscious choice of not using it because it definitely makes things
> a bit easier wrt to the part where you try to sync with tcpdump..
> 
> Also +1 on saving the raw file (via libpcap or tcpdump -w).

I agree to do it with libpcap. And, will print a number to stdout/stderr
as an index to the packets in the raw file. However, I need to figure
out how to make the raw file available to developers at first.