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From: Johannes Berg <johannes@sipsolutions.net>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>
Subject: Re: eBPF - little-endian load instructions?
Date: Tue, 11 Apr 2017 13:15:30 +0200	[thread overview]
Message-ID: <1491909330.31620.21.camel@sipsolutions.net> (raw)
In-Reply-To: <58ECB8CF.8040409@iogearbox.net>


> Are you working with an skb at that point in time in wifi? 

Yes.

> There are
> 3 different ways of accessing skb data, see [1] slide 7 - 10. The BPF
> LD_ABS/IND instructions were carried over from cBPF and are the only
> ones that convert to host endianess. It can be used in eBPF as well,
> but there are more efficient ways like 'direct packet access' or
> helpers such as bpf_skb_load_bytes() that load the raw buffers as-is,
> which is probably what you want if I understand you correctly.

Sounds like, yeah.

> There are instructions to convert endianess, see __bpf_prog_run(),
> the ALU_END_TO_BE, ALU_END_TO_LE labels for details. There's a
> BPF_ENDIAN() macro used in the test suite and other places.

Ok, thanks! :)

So sounds like I don't need anything special - should have a patch to
hook up the wifi stuff soon.

johannes

  reply	other threads:[~2017-04-11 11:15 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-11 10:38 eBPF - little-endian load instructions? Johannes Berg
2017-04-11 11:06 ` Daniel Borkmann
2017-04-11 11:15   ` Johannes Berg [this message]
2017-04-11 11:22     ` Daniel Borkmann
2017-04-11 11:26       ` Johannes Berg
2017-04-12 13:02   ` Johannes Berg
2017-04-12 16:58     ` Alexei Starovoitov
2017-04-12 19:38       ` Johannes Berg
2017-04-13  3:08         ` Alexei Starovoitov
2017-04-13  5:58           ` Johannes Berg
2017-04-14 18:42             ` Alexei Starovoitov
2017-04-15  7:06               ` Johannes Berg

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