Re: How to troubleshoot extcap applications?

[João Valverde <j () v6e pt>]

This is almost certainly my fault when integrating extcap with wslog. 
Thanks for looking into it.

I'm not sure disabling every message to stderr is a good idea. The 
problem space is the same as with dumpcap and that already works seamlessly.

But for now muting stderr with extcap --debug is probably good enough 
and I can look into it later, if you prefer.

On 01/12/21 13:18, Jirka Novak wrote:
> Hi,
>
>    I noticed issue below and I propose a solution for it. Can I ask for
> comments?
>
>    Every extcap tool has --debug and --debug-file options, but when they
> are used, it do "nothing". File is created, but it is empty.
>    Later I found that it must be used with --log-level=debug to really
> log messages.
>    The issue is that when you increase --log-level, it logs to console
> (STDERR). So when extcap is started from Wireshark, it mixes log output
> with packet data and wireshark gets confused and I found no way how to
> make it operational.
>    In other words you can't use debug of extcap from Wireshark.
>
>    In code I found that the reason is that wsutils/wscode.c writes every
> message to STDERR. If application registers additional file, it is
> copied to it too, but output to STDERR is made in every case.
>    Applications can replace default writer to STDERR, but no extcap do it.
>
>    My proposal is to modify extcap/extcap-base.c:
> 1) When --debug is used, set log level to debug so you don't have to add
> --log-level
> 2) If --log-file used, register custom log writer with
> ws_log_init_with_writer() which will discard all messages so just write
> to file will be made.
> 3) Update log init in every extcap
>
>    Change is quite simple, but involves all extcaps. I already tested it
> and it works. I'm just not sure every extcap.
>    I'm ready to prepare patch.
>
>                                         Best regards,
>
>                                                 Jirka
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