From: Stephen Hemminger <stephen@networkplumber.org>
To: Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>
Cc: dev@dpdk.org, Konstantin Ananyev <konstantin.ananyev@huawei.com>,
stable@dpdk.org, Isaac Boukris <iboukris@gmail.com>
Subject: Re: [PATCH 2/3] bfp: fix load hangs with six IPv6 addresses
Date: Thu, 27 Jun 2024 08:13:43 -0700 [thread overview]
Message-ID: <20240627081343.744b612d@hermes.local> (raw)
In-Reply-To: <20240627115531.1440-3-konstantin.v.ananyev@yandex.ru>
On Thu, 27 Jun 2024 12:55:30 +0100
Konstantin Ananyev <konstantin.v.ananyev@yandex.ru> wrote:
> From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
>
> As described in: https://bugs.dpdk.org/show_bug.cgi?id=1465
> converting from following cBPF filter:
> "host 1::1 or host 1::1 or host 1::1 or host 1::1 or host 1::1 or host 1::1"
> taking too long for BPF verifier ito complete (up to 25 seconds).
> Looking at it I didn't find any actual functional bug.
> In fact, it does what is expected: goes through each possible path of
> BPF program and evaluates register/stack state for each instruction.
> The problem is that for program with a lot of conditional branches number
> of possible paths starts to grow exponentially and such walk becomes very
> excessive.
> So to minimize number of evaluations, this patch implements heuristic
> similar to what Linux kernel does - state pruning:
> If from given instruction for given program state we explore all possible
> paths and for each of them reach bpf_exit() without any complaints and a
> valid R0 value, then for that instruction this program state can be
> marked as 'safe'. When we later arrive at the same instruction with a state
> equivalent to an earlier instruction 'safe' state, we can prune the search.
> For now, only states for JCC targets are saved/examined.
> Plus added few extra logging for DEBUG level.
>
> Bugzilla ID: 1465
> Fixes: 8021917293d0 ("bpf: add extra validation for input BPF program")
> Cc: stable@dpdk.org
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> + struct bpf_eval_state *cur; /*save/restore for jcc targets */
Nit: should have space after /* in this comment
next prev parent reply other threads:[~2024-06-27 15:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240627115531.1440-1-konstantin.v.ananyev@yandex.ru>
2024-06-27 11:55 ` [PATCH 1/3] bfp: fix MOV instruction evaluation Konstantin Ananyev
2024-06-27 11:55 ` [PATCH 2/3] bfp: fix load hangs with six IPv6 addresses Konstantin Ananyev
2024-06-27 15:13 ` Stephen Hemminger [this message]
[not found] ` <20240627180442.1602-1-konstantin.v.ananyev@yandex.ru>
2024-06-27 18:04 ` [PATCH v2 1/3] bfp: fix MOV instruction evaluation Konstantin Ananyev
2024-06-27 18:04 ` [PATCH v2 2/3] bfp: fix load hangs with six IPv6 addresses Konstantin Ananyev
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=20240627081343.744b612d@hermes.local \
--to=stephen@networkplumber.org \
--cc=dev@dpdk.org \
--cc=iboukris@gmail.com \
--cc=konstantin.ananyev@huawei.com \
--cc=konstantin.v.ananyev@yandex.ru \
--cc=stable@dpdk.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 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).