All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Jakub Kicinski <kubakici@wp.pl>,
	David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org, xdp-newbies@vger.kernel.org,
	brouer@redhat.com
Subject: Re: [PATCH v3 net-next RFC] Generic XDP
Date: Sun, 16 Apr 2017 22:26:01 +0200	[thread overview]
Message-ID: <20170416222601.671f037c@redhat.com> (raw)
In-Reply-To: <20170415004642.GA73685@ast-mbp.thefacebook.com>

On Fri, 14 Apr 2017 17:46:44 -0700
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:

> But that's probably bad idea, since I was assuming that such ring
> reconfiguration can be made fast, which is unlikely.
> If it takes seconds to setup a ring, then drivers should just
> assume XDP_PACKET_HEADROOM, since at that time the program
> properties are unknown and in the future other programs will be loaded.
>
> Take a look at our current setup with slots for xdp_dump, ddos, lb
> programs. Only root program is attached at the begining.
> If the driver configures the ring for such empty program that would break
> dynamic addition of lb prog.
> The driver must not interrupt the traffic when user adds another
> prog to prog array. In such case XDP side doesn't even know that
> prog array is used. It's all happening purely on bpf side.

The bpf tail-call use-case is a very good example of why the verifier
cannot deduct the needed HEADROOM upfront.

Could we still make the verifier reject a program getting attached as a
tail-call when a too "low"/small HEADROOM have been setup? (to satisfy
programs needs)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer

  parent reply	other threads:[~2017-04-16 20:26 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-12 18:54 [PATCH v3 net-next RFC] Generic XDP David Miller
2017-04-12 19:54 ` David Ahern
2017-04-13  2:08   ` David Miller
2017-04-13  2:16     ` David Ahern
2017-04-12 21:30 ` Stephen Hemminger
2017-04-12 21:49   ` Eric Dumazet
2017-04-13  1:55     ` David Miller
2017-04-13  1:54   ` David Miller
2017-04-13  4:20 ` Alexei Starovoitov
2017-04-13  6:10   ` Johannes Berg
2017-04-13 15:38     ` David Miller
2017-04-14 19:41       ` Alexei Starovoitov
2017-04-18  9:47         ` Johannes Berg
2017-04-18 23:09           ` Alexei Starovoitov
2017-04-13 15:37   ` David Miller
2017-04-13 19:22     ` Johannes Berg
2017-04-13 20:01       ` David Miller
2017-04-14  8:07         ` Johannes Berg
2017-04-14 19:09           ` Alexei Starovoitov
2017-04-14  9:05     ` Jesper Dangaard Brouer
2017-04-14 19:28       ` Alexei Starovoitov
2017-04-14 22:18         ` Daniel Borkmann
2017-04-14 22:30         ` Jakub Kicinski
2017-04-15  0:46           ` Alexei Starovoitov
2017-04-15  1:47             ` Jakub Kicinski
2017-04-16 20:26             ` Jesper Dangaard Brouer [this message]
2017-04-17 19:49               ` David Miller
2017-04-17 23:04                 ` Alexei Starovoitov
2017-04-17 23:33                   ` Daniel Borkmann
2017-04-18 18:46                   ` David Miller
2017-04-18 23:05                     ` Alexei Starovoitov
2017-04-13  6:48 ` Michael Chan
2017-04-13 15:38   ` David Miller
2017-04-13 15:57 ` Daniel Borkmann
2017-04-13 16:04   ` David Miller
2017-04-13 17:13 ` aa5c2fd79f: net/core/dev.c:#suspicious_rcu_dereference_check()usage kernel test robot
2017-04-13 17:13   ` kernel test robot

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=20170416222601.671f037c@redhat.com \
    --to=brouer@redhat.com \
    --cc=alexei.starovoitov@gmail.com \
    --cc=davem@davemloft.net \
    --cc=kubakici@wp.pl \
    --cc=netdev@vger.kernel.org \
    --cc=xdp-newbies@vger.kernel.org \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.