Re: [PATCH v5 0/2] Add config file support for l3fwd

[Stephen Hemminger <stephen@networkplumber.org>]

On Sun, 6 Feb 2022 15:16:22 +0000
"Ananyev, Konstantin" <konstantin.ananyev@intel.com> wrote:

> > > This patchset introduces config file support for l3fwd
> > > and its lookup methods LPM, FIB, and EM, similar to
> > > that of l3fwd-acl. This allows for route rules to be
> > > defined in configuration files and edited there instead
> > > of in each of the lookup methods hardcoded route tables.
> > >
> > > V4:
> > > * Fix nondeterministic bug of segfault on termination of
> > >   sample app.
> > > V5:
> > > * Reintroduce hardcoded tables as to not break dts and
> > >   allow for hardcoded tables to be used if no config
> > >   files presented.
> > >
> > > Sean Morrissey (2):
> > >   examples/l3fwd: add config file support for LPM/FIB
> > >   examples/l3fwd: add config file support for EM
> > >
> > >  doc/guides/sample_app_ug/l3_forward.rst |  89 +++--
> > >  examples/l3fwd/em_default_v4.cfg        |  17 +
> > >  examples/l3fwd/em_default_v6.cfg        |  17 +
> > >  examples/l3fwd/l3fwd.h                  |  41 +++
> > >  examples/l3fwd/l3fwd_em.c               | 471 +++++++++++++++++-------
> > >  examples/l3fwd/l3fwd_fib.c              |  50 +--
> > >  examples/l3fwd/l3fwd_lpm.c              | 315 +++++++++++++++-
> > >  examples/l3fwd/l3fwd_route.h            |  41 +++
> > >  examples/l3fwd/lpm_default_v4.cfg       |  17 +
> > >  examples/l3fwd/lpm_default_v6.cfg       |  17 +
> > >  examples/l3fwd/main.c                   |  68 +++-
> > >  11 files changed, 949 insertions(+), 194 deletions(-)
> > >  create mode 100644 examples/l3fwd/em_default_v4.cfg
> > >  create mode 100644 examples/l3fwd/em_default_v6.cfg
> > >  create mode 100644 examples/l3fwd/lpm_default_v4.cfg
> > >  create mode 100644 examples/l3fwd/lpm_default_v6.cfg
> > >  
> > 
> > Why not use the DPDK cfgfile library and format?
> > It is model after standard INI format.  
> 
> It is probably some sort of misunderstanding:
> This patch doesn't add configuration file for some l3fwd run-time parameters
> (number of ports/queues, queue/cpu mappings, etc.).
> It allows user to specify he's own routing table instead of hard-coded ones.
> For routing table .ini file format is not really suitable.
> Instead we follow format similar to what is used in other DPDK apps
> (l3fwd-acl, ipsec-secgw, test-acl, test-fib,  test-sad, etc.) for these purposes:
> list of route entries, each entry occupies exactly one line.
> As an example:
> /examples/l3fwd/lpm_default_v4.cfg
> #Copy of hard-coded IPv4 FWD table for L3FWD LPM
> R198.18.0.0/24 0
> R198.18.1.0/24 1
> R198.18.2.0/24 2
> R198.18.3.0/24 3
> ....
> I suppose it is self-explanatory, intuitive and close enough 
> to what user used for with unix-like route config tools.
> Konstantin

I was think either, use existing cfgfile and a a section of LPM
so that it could be an example and also have some generic code for handling
prefix entries.

Or have a generic library for reading LPM entries.  L3fwd is supposed
to be as small as possible (it no longer is), and the real work should
be done by libraries to make it easier to build other applications.