[RFC 0/7] Introduce FreeBSD macros for SAFE iteration

[Stephen Hemminger]

On Mon, 27 Jan 2025 20:29:55 +0100
Morten Brørup <mb at smartsharesystems.com> wrote:

> > From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> > Sent: Monday, 27 January 2025 19.44
> > 
> > On Mon, 27 Jan 2025 18:16:18 +0000
> > Bruce Richardson <bruce.richardson at intel.com> wrote:
> >   
> > > On Mon, Jan 27, 2025 at 10:03:54AM -0800, Stephen Hemminger wrote:  
> > > > This series adds common macros for safe iteration over lists.
> > > > It is a subset copy of the macros from FreeBSD that are
> > > > missing from the Linux header sys/queue.h
> > > >
> > > > Chose this over several other options:
> > > >   - let each driver define their own as needed.
> > > >     One Intel driver got it wrong, others will as well.
> > > >   - rename all the queue macros to RTE_XXX variants.
> > > >     Seems like useless renaming and confusion.
> > > >   - Several distros have libbsd package with the correct macros.
> > > >     But adding yet another dependency to DPDK would be annoying
> > > >     for something this basic.
> > > >  
> > >
> > > Actually, I wouldn't be that quick to eliminate the last option. It  
> > may  
> > > give us some additional options for simplification. For example, the
> > > strlcpy and strlcat functions are in libbsd too, and if we had that  
> > as  
> > > mandatory dependency, perhaps we could remove some extra code there  
> > too?  
> > >
> > > /Bruce
> > >  
> > 
> > I would be ok with using libbsd but only if we didn't have to keep a
> > parallel
> > copy for all the other compiler and OS variants. And would it be global
> > or
> > a per-driver dependency?  
> 
> +1 to providing our own implementations of relevant libbsd features in the DPDK EAL, rather than depending on the entire libbsd (and libbsd-dev for development). Providing these features as part of a "utilities library" (which is currently integrated into the EAL) is better for non-Unix environments.
> 
> Furthermore, libbsd has plenty of stuff we don't need:
> https://manpages.debian.org/testing/libbsd-dev/index.html

The red-black tries in libbsd are very useful. In one product we used it as a way
to manage LPM rules, since the current DPDK model is O(N^2) and works terribly in
a router with 3M routes.