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List:       tcpdump-workers
Subject:    Re: [tcpdump-workers] pcap_compile_nopcap() not in man pages
From:       Guy Harris via tcpdump-workers <tcpdump-workers () lists ! tcpdump ! org>
Date:       2020-08-12 19:59:35
Message-ID: mailman.49.1597261138.29104.tcpdump-workers () lists ! tcpdump ! org
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Subject: Re: [tcpdump-workers] pcap_compile_nopcap() not in man pages
From: Guy Harris <gharris@sonic.net>
In-Reply-To: <mailman.21.1597257892.29104.tcpdump-workers@lists.tcpdump.org>
Date: Wed, 12 Aug 2020 12:59:35 -0700
Cc: tcpdump-workers@lists.tcpdump.org
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References: <mailman.21.1597257892.29104.tcpdump-workers@lists.tcpdump.org>
To: Denis Ovsienko <denis@ovsienko.info>
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(Your first attempt seems to have worked - finally.  Perhaps Michael =
cleared the backlog?)

On Aug 10, 2020, at 4:24 AM, Denis Ovsienko via tcpdump-workers =
<tcpdump-workers@lists.tcpdump.org> wrote:

> It turns out, pcap_compile_nopcap() has been a part of the libpcap API
> since version 0.5 (June 2000), but it is not even mentioned anywhere =
in
> the man pages. The existing pcap_compile.3pcap man page seems to be =
the
> best place to add this information, since the two functions are
> similar. Would it be the right thing to do?

The problem with pcap_compile_nopcap() is that it provides no way to =
return an error message if it fails, unlike pcap_open_dead() combined =
with pcap_compile(), where you can use pcap_geterr() before closing the =
pcap_t.

An additional problem is that NetBSD fixed this by adding an =
error-buffer pointer argument, but that meant that NetBSD's =
pcap_compile_nopcap() was unfixably incompatible with the one in other =
OSes.  They've shifted to the compatible API, at the cost of not being =
able to get an error string.

So, for now, my inclination is to 1) deprecate pcap_compile_nopcap() =
(complete with marking it as deprecated, so code that uses it gets a =
compile-time warning on compilers where the deprecation macro is =
supported) and 2) not document it.=


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