netdev - Re: [PATCH bpf-next 1/2] samples/bpf: fixup xdp_redirect tool to be able to support xdp multibuffer

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Message-ID: <cf3903b0-9258-d000-c8b4-1f196ea726c5@linux.dev>
Date: Tue, 30 May 2023 10:22:11 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Tariq Toukan <ttoukan.linux@...il.com>
Cc: brouer@...hat.com, Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>, bpf@...r.kernel.org,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 netdev@...r.kernel.org, Gal Pressman <gal@...dia.com>,
 Nimrod Oren <noren@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
 Lorenzo Bianconi <lorenzo.bianconi@...hat.com>, drosen@...gle.com,
 Joanne Koong <joannelkoong@...il.com>, henning.fehrmann@....mpg.de,
 oliver.behnke@....mpg.de, Jesper Dangaard Brouer <jbrouer@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH bpf-next 1/2] samples/bpf: fixup xdp_redirect tool to be
 able to support xdp multibuffer

On 5/30/23 6:40 AM, Tariq Toukan wrote:
>>> I initiated a discussion on this topic a few months ago. dynptr was accepted 
>>> since then, but I'm not aware of any in-progress followup work that addresses 
>>> this.
>>>
>>
>> Are you saying some more work is needed on dynptr?
>>
> 
> AFAIU yes.
> But I might be wrong... I need to revisit this.
> Do you think/know that dynptr can be used immediately?

Not sure if you are aware of the bpf_dynptr_slice[_rdwr]() which could be useful 
here. It only does a copy when the requested slice is across different frags:
https://lore.kernel.org/all/20230301154953.641654-10-joannelkoong@gmail.com/