From: "Robin Jarry" <rjarry@redhat.com>
To: "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>
Cc: <dev@dpdk.org>, "Bruce Richardson" <bruce.richardson@intel.com>
Subject: Re: fib{,6}: questions and proposals
Date: Tue, 19 Mar 2024 21:38:33 +0100 [thread overview]
Message-ID: <CZY0LHKYV4ZO.YRBZ6C6GW6AI@redhat.com> (raw)
In-Reply-To: <fd03db0e-342f-4cac-8e56-9ecbcbe3c89d@intel.com>
Hi Vladimir,
Medvedkin, Vladimir, Mar 19, 2024 at 18:16:
> > 2) Is it OK/safe to modify a fib from a control thread (read/write)
> > while it is used by data path threads (read only)?
>
> This part is a bit more complicated. In practice, I would say yes,
> however, there is a possibility that if the lookup thread is preempted
> in the middle of the lookup process, and at the same time the control
> thread deletes the corresponding route, then the lookup result may
> return outdated data. This problem is solved in LPM with RCU enabled.
> I have plans to implement it in the near future in the FIB.
OK that's good to know, thanks.
> > 3) There is no public API to list/walk all configured routes in
> > a fib. Would that be possible/easy to implement?
>
> Yes, it already there. FIB under the hood uses rte_rib to hold
> existing routes. So walking through can be implemented like:
I had tried it and got confusing results out of this. This must have
been before I had realized that all addresses needed to be in host
order...
I tried again and it works as advertised with a small missing detail:
after configuring a default route, e.g.:
rte_fib_add(fib, RTE_IPV4(2, 2, 0, 0), 16, RTE_IPV4(1, 2, 3, 4));
rte_fib_add(fib, RTE_IPV4(3, 3, 3, 0), 24, RTE_IPV4(4, 3, 2, 1));
rte_fib_add(fib, RTE_IPV4(0, 0, 0, 0), 0, RTE_IPV4(9, 9, 9, 9));
It is not returned by rte_rib_get_nxt() successive calls. I only see the
other two routes:
2.2.0.0/16 via 1.2.3.4
3.3.3.0/24 via 4.3.2.1
Is this expected?
> > 4) In rte_fib, every IPv4 address (route *and* next hop) needs to be
> > in host order. This is not consistent with fib6 where addresses
> > are stored in network order. It took me quite a while to figure
> > out what was wrong with my code.
>
> This API behavior was created in such a way that it is the same as
> LPM.
>
> As for LPM, I think it was done this way for performance reasons
> because in some scenarios you only working with the host order ipv4
> addresses.
This should really be advertised in strong capital letters in the API
docs. Or (preferably) hidden to the user. I don't see any valid scenario
where you would work with host order IPv4 addresses.
Do you think we could change that API or at least add a flag at FIB/RIB
creation to make it transparent to the user and consistent between IPv4
and IPv6?
Thanks!
next prev parent reply other threads:[~2024-03-19 20:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 8:30 Robin Jarry
2024-03-19 17:16 ` Medvedkin, Vladimir
2024-03-19 20:38 ` Robin Jarry [this message]
2024-03-20 7:45 ` Morten Brørup
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CZY0LHKYV4ZO.YRBZ6C6GW6AI@redhat.com \
--to=rjarry@redhat.com \
--cc=bruce.richardson@intel.com \
--cc=dev@dpdk.org \
--cc=vladimir.medvedkin@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).