netdev - Re: [RFC] iproute: Add support for extended ack to rtnl

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Date:   Thu, 4 May 2017 20:55:56 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: Re: [RFC] iproute: Add support for extended ack to rtnl_talk

On Thu, May 04, 2017 at 09:45:58AM -0700, Stephen Hemminger wrote:
> On Thu, 4 May 2017 17:37:38 +0300
> Leon Romanovsky <leon@...nel.org> wrote:
>
> > On Thu, May 04, 2017 at 11:36:36AM +0200, Daniel Borkmann wrote:
> > > On 05/04/2017 01:56 AM, Stephen Hemminger wrote:
> > > > Add support for extended ack error reporting via libmnl. This
> > > > is a better alternative to use existing library and not copy/paste
> > > > code from the kernel. Also make arguments const where possible.
> > > >
> > > > Add a new function rtnl_talk_extack that takes a callback as an input
> > > > arg. If a netlink response contains extack attributes, the callback is
> > > > is invoked with the the err string, offset in the message and a pointer
> > > > to the message returned by the kernel.
> > > >
> > > > Adding a new function allows commands to be moved over to the
> > > > extended error reporting over time.
> > > >
> > > > For feedback, compile tested only.
> > >
> > > Just out of curiosity, what is the plan regarding converting iproute2
> > > over to libmnl (ip, tc, ss, ...)? In 2015, tipc tool was the first
> > > user merged that requires libmnl, the only other user today in the
> > > tree is devlink, which even seems to define its own libmnl library
> > > helpers. What is the clear benefit/rationale of outsourcing this to
> > > libmnl? I always was the impression we should strive for as little
> > > dependencies as possible?
> >
> > And I would like to get direction for the RDMA tool [1] which I'm
> > working on it now.
> >
> > The overall decision was to use netlink and put it under iproute2
> > umbrella. Currently, I have working RFC which is based on
> > legacy sysfs interface to ensure that we are converging on
> > user-experience even before moving to actual netlink defines.
> >
> > An I would like to continue to work on netlink interface, but which lib interface
> > should I need to base rdmatool's netlink code?
> >
> > [1] https://www.mail-archive.com/netdev@vger.kernel.org/msg148523.html
> >
> > >
> > > I don't really like that we make extended ack reporting now dependent
> > > on libmnl, which further diverts from iproute's native nl library vs
> > > requiring to install another nl library, making the current status
> > > quo even worse ... :/
> > >
> > > Thanks,
> > > Daniel
>
> I would prefer new code use libmnl, but using libnetlink would also be ok.
> Any later conversion to libmnl would be mostly automated anyway.

Thanks, I'm copy/pasting devlink variation of libmnl :)

>
> The real objection was copy/pasting in the kernel netlink parser.
> That was unnecessary bloat.



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