[OpenWrt-Devel] [PATCH] libpcap: patch to add limits.h to pcap-usb-linux.c

[Bjørn Mork]

Michael Richardson <mcr at sandelman.ca> writes:
> Bjørn Mork <bjorn at mork.no> wrote:
>     >> The reason why the buildservers don't fail is that they're probably
>     >> not setting CONFIG_PCAP_HAS_USB (default is OFF), so the patched file
>     >> does not get compiled.  I will add that info in the cover letter.
>
>     > Not directly related.... But I wonder if maybe this default could be
>     > changed?
>
>     > I realize that this is a space thing, but having an optional feature
>     > defaulting to off means that practically nobody uses the feature.  And
>     > this one is particularily useful.  At least to me :-) Which of course
>     > is no argument since I can easily build my own images with the feature
>     > enabled.
>
> I also agree, but turning in USB requires additional libraries, and I'm not
> sure that many will need USB captures on openwrt.

I agree that most users won't need it. The problem is the high threshold
for those few who do.

I've been into the LTE modem driver business for a while. Captures from
end users with some modem hardware/firmware specific issue have often
been the only way to fully understand a problem. Changing an option
hidden deep inside the OpenWrt build config is out of the question
unless the reporter already is familiar with that build system.  It is
about as convenient as a kernel debug patch for most end users.  The
lack of a pre-built usbmon capture tool makes bug reports from OpenWrt
users much harder to debug.

BTW: I tried to figure out which additional libraries the feature
requires.  It doesn't seem to be any? pcap-usb-linux.c uses the Linux
kernel support directly.  Or am I missing something?

> I (as mcr at tcpdump.org) don't understand why you are seeing a build failure
> that causes you to want to patch the file.

The build failure is in version 1.8.1 used by OpenWrt 18.06.  The fix
being discussed is a backport of this upstream patch:

 https://github.com/the-tcpdump-group/libpcap/commit/aafa3512b7b742f5e66a5543e41974cc5e7eebfa

> Also, the latest libpcap (1.9.0) has cmake support, which might make things
> easier?

Maybe? All these questions are of course up to the maintainer. Adding
Felix to the CC list.



Bjørn

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