From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Lorenzo Bianconi <lorenzo.bianconi@redhat•com>,
John Fastabend <john.fastabend@gmail•com>
Cc: Eelco Chaudron <echaudro@redhat•com>,
Lorenzo Bianconi <lorenzo@kernel•org>,
bpf@vger•kernel.org, netdev@vger•kernel.org, davem@davemloft•net,
kuba@kernel•org, ast@kernel•org, daniel@iogearbox•net,
shayagr@amazon•com, sameehj@amazon•com, dsahern@kernel•org,
brouer@redhat•com, jasowang@redhat•com,
alexander.duyck@gmail•com, saeed@kernel•org,
maciej.fijalkowski@intel•com, magnus.karlsson@intel•com,
tirthendu.sarkar@intel•com
Subject: Re: [PATCH v9 bpf-next 08/14] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API
Date: Tue, 29 Jun 2021 15:27:43 +0200 [thread overview]
Message-ID: <874kdgkdgw.fsf@toke.dk> (raw)
In-Reply-To: <YNsdyD6OBXcf5mUa@lore-desk>
Lorenzo Bianconi <lorenzo.bianconi@redhat•com> writes:
>> Eelco Chaudron wrote:
>> >
>> >
>> > On 23 Jun 2021, at 1:37, John Fastabend wrote:
>> >
>> > > Lorenzo Bianconi wrote:
>> > >> From: Eelco Chaudron <echaudro@redhat•com>
>> > >>
>> > >> This change adds support for tail growing and shrinking for XDP multi-buff.
>> > >>
>> > >
>> > > It would be nice if the commit message gave us some details on how the
>> > > growing/shrinking works in the multi-buff support.
> [...]
>> > Guess this is the tricky part, applications need to be multi-buffer aware. If current applications rely on bpf_xdp_adjust_tail(+) to determine maximum frame length this approach might not work. In this case, we might need an additional helper to do tail expansion with multi buffer support.
>> >
>> > But then the question arrives how would mb unaware application behave in general when an mb packet is supplied?? It would definitely not determine the correct packet length.
>>
>> Right that was my conclusion as well. Existing programs might
>> have subtle side effects if they start running on multibuffer
>> drivers as is. I don't have any good ideas though on how
>> to handle this.
>
> what about checking the program capabilities at load time (e.g. with a
> special program type) and disable mb feature if the bpf program is not
> mb-aware? (e.g. forbid to set the MTU greater than 1500B in xdp mode).
So what happens when that legacy program runs on a veth and gets an
mb-enabled frame redirected into it? :)
-Toke
next prev parent reply other threads:[~2021-06-29 13:27 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 12:49 [PATCH v9 bpf-next 00/14] mvneta: introduce XDP multi-buffer support Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 01/14] net: skbuff: add data_len field to skb_shared_info Lorenzo Bianconi
2021-06-28 19:58 ` Alexander Duyck
2021-06-29 12:44 ` Lorenzo Bianconi
2021-06-29 17:08 ` Jakub Kicinski
2021-06-29 18:18 ` Alexander Duyck
2021-06-29 18:37 ` Jakub Kicinski
2021-06-29 19:11 ` Jesper Dangaard Brouer
2021-06-29 19:18 ` Lorenzo Bianconi
2021-06-29 20:45 ` Alexander Duyck
2021-06-14 12:49 ` [PATCH v9 bpf-next 02/14] xdp: introduce flags field in xdp_buff/xdp_frame Lorenzo Bianconi
2021-06-28 20:14 ` Alexander Duyck
2021-06-29 12:43 ` Lorenzo Bianconi
2021-06-29 13:07 ` Alexander Duyck
2021-06-29 13:25 ` Lorenzo Bianconi
2021-07-05 15:52 ` Lorenzo Bianconi
2021-07-05 21:35 ` Alexander Duyck
2021-07-06 11:53 ` Lorenzo Bianconi
2021-07-06 14:04 ` Alexander Duyck
2021-07-06 17:47 ` Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 03/14] net: mvneta: update mb bit before passing the xdp buffer to eBPF layer Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 04/14] xdp: add multi-buff support to xdp_return_{buff/frame} Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 05/14] net: mvneta: add multi buffer support to XDP_TX Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 06/14] net: mvneta: enable jumbo frames for XDP Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 07/14] net: xdp: add multi-buff support to xdp_build_skb_from_frame Lorenzo Bianconi
2021-06-28 21:05 ` Alexander Duyck
2021-06-29 18:34 ` Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 08/14] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API Lorenzo Bianconi
2021-06-22 23:37 ` John Fastabend
2021-06-24 9:26 ` Eelco Chaudron
2021-06-24 14:24 ` John Fastabend
2021-06-24 15:16 ` Zvi Effron
2021-06-29 13:19 ` Lorenzo Bianconi
2021-06-29 13:27 ` Toke Høiland-Jørgensen [this message]
2021-07-06 21:44 ` Backwards compatibility for XDP multi-buff (was: Re: [PATCH v9 bpf-next 08/14] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API) Toke Høiland-Jørgensen
2021-06-14 12:49 ` [PATCH v9 bpf-next 09/14] bpf: introduce bpf_xdp_get_buff_len helper Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 10/14] bpf: add multi-buffer support to xdp copy helpers Lorenzo Bianconi
2021-06-22 23:49 ` John Fastabend
2021-06-24 9:42 ` Eelco Chaudron
2021-06-24 14:28 ` John Fastabend
2021-06-25 8:25 ` Eelco Chaudron
2021-06-29 13:23 ` Lorenzo Bianconi
2021-07-06 10:15 ` Eelco Chaudron
2021-06-14 12:49 ` [PATCH v9 bpf-next 11/14] bpf: move user_size out of bpf_test_init Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 12/14] bpf: introduce multibuff support to bpf_prog_test_run_xdp() Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 13/14] bpf: test_run: add xdp_shared_info pointer in bpf_test_finish signature Lorenzo Bianconi
2021-06-14 12:49 ` [PATCH v9 bpf-next 14/14] bpf: update xdp_adjust_tail selftest to include multi-buffer Lorenzo Bianconi
2021-06-22 23:18 ` [PATCH v9 bpf-next 00/14] mvneta: introduce XDP multi-buffer support John Fastabend
2021-06-23 3:41 ` David Ahern
2021-06-23 5:48 ` John Fastabend
2021-06-23 14:40 ` David Ahern
2021-06-24 14:22 ` John Fastabend
2021-07-01 7:56 ` Magnus Karlsson
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