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

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> > > > 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

LPM can have thousands or even millions entries,
it probably wouldn't be nice to pollute all of them in .ini file
together with usual settings.
At least my preference would be to have them in separate file - clean and simple

> so that it could be an example and also have some generic code for handling
> prefix entries.

Didn't get your sentence above about 'generic code for handling prefix entries'.
Could you possibly elaborate.
 
> 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.

I never heard users ask about such thing,
but if there is a demand for that, then I suppose it could be considered.
CC-ing LPM/FIB maintainers to comment.
Though I believe it should be a subject of separate patch and discussion 
(I think many questions will arise - what format should be, how to support 
different types of user-data, to make it generic enough, etc.).
Konstantin