From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Henning Fehrmann <henning.fehrmann@aei.mpg.de>,
"xdp-newbies@vger.kernel.org" <xdp-newbies@vger.kernel.org>
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Subject: Re: make XDP program aware of multi buffer
Date: Wed, 30 Nov 2022 14:11:03 +0100 [thread overview]
Message-ID: <87wn7cy4d4.fsf@toke.dk> (raw)
In-Reply-To: <Y4caS5Bh7M9SDJf9@mephisto.aei.uni-hannover.de>
Henning Fehrmann <henning.fehrmann@aei.mpg.de> writes:
>> You just replace:
>>
>> SEC("xdp")
>>
>> with
>>
>> SEC("xdp.frags")
>>
>> in your source file and, assuming your libbpf version is up-to-date,
>> that should be it as far as the kernel is concerned.
>
> Nice. It loads now. I appreciate the work done for multi buffer packets.
Cool!
>> However, you obviously also need to make sure there are no semantic
>> issues in your program before doing this. I.e., data_end is no longer
>> the end of your packet, so if you are using data_end-data to calculate
>> the packet len, that will no longer be accurate. If you need to access
>> data beyond the first frag you'll need to use the
>> xdp_{load,store}_bytes() helpers.
>
> I guess, this is not the case or does bpf_redirect needs it if I have
> multi frame packets?
> I realized that redirection actually doesn't happen if the packets
> exceed the page size.
No, XDP_REDIRECT is not supported at all for multi-frame packets:
https://elixir.bootlin.com/linux/latest/source/net/core/filter.c#L4278
Cc Lorenzo who was looking into enabling this at some point...
-Toke
prev parent reply other threads:[~2022-11-30 13:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-29 12:14 make XDP program aware of multi buffer Henning Fehrmann
2022-11-29 13:24 ` Toke Høiland-Jørgensen
2022-11-30 8:54 ` Henning Fehrmann
2022-11-30 13:11 ` Toke Høiland-Jørgensen [this message]
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