Re: RFC: a loadable plugin framework for external capture backends

[Robin Jarry via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

> --- Begin Message ---
>
>
> From: "Robin Jarry" <rjarry () redhat com>
>
> Date: Sat, 03 Oct 2026 12:11:36 +0200
>
> Michael Richardson, Oct 03, 2026 at 01:10:
> > > So you're saying that plugins should be bundled *by the OS 
> > > distributor* and wired in, rather than allowing outside-of-libpcap 
> > > projects *not* bundled by the distributor to be plugged into libpcap?
> >
> > I'm saying that calling dlopen() shouldn't be required: do that at 
> > link time.
>
> This would defeat the whole purpose of external applications providing 
> their own backend without libpcap knowing about them in advance.
>
> dlopen() is the only solution if we don't want to hardcode the list of 
> well-known plugins *and* require their .so to be present at build time 
> so that the linker is happy.
>
> > > If so, that might work for most cases with Linux distributions, most 
> > > of which don't seem to draw a strong distinction between "core OS" 
> > > and "packages". It *does* mean that the libpcap package would have 
> > > more dependencies.
> >
> > Yes, that's the problem with "compile-time option, disabled"..
>
> libpcap must *not* have any additional dependencies. This is the other 
> way around: external backends would depend on libpcap plugin ABI. They 
> would drop their plugins in a well known location and libpcap would 
> dynamically load them at runtime, not build time.
>
> > > It might not work so well for the *BSDs, most of which have a "core 
> > > OS" separate from the package collection, and that include libpcap in 
> > > the "core OS". That includes macOS ("CupertinoBSD"), which, being 
> > > a commercial OS, may have third-party *binary-only* libpcap 
> > > extensions, which would require a stadardized *ABI*. (macOS is one 
> > > reason why I try to make sure libpcap never changes its ABI other 
> > > than, perhaps, carefully dropping routines from the API/ABI over 
> > > time, as long as they've been deprecated before their disappearance.)
> >
> > libpcap 2.x
>
> The plugin *ABI* does not need to be standardized across different OSes 
> and architectures, only the *API*.
>
> --
> Robin
>
> # Prices subject to change without notice.
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>
> --- End Message ---
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