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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>,
	duanxiongchun@bytedance.com,
	Dongdong Wang <wangdongdong.6@bytedance.com>,
	jiang.wang@bytedance.com, Cong Wang <cong.wang@bytedance.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Lorenz Bauer <lmb@cloudflare.com>
Subject: Re: [Patch bpf-next 03/19] skmsg: use skb ext instead of TCP_SKB_CB
Date: Mon, 8 Feb 2021 10:56:54 -0800	[thread overview]
Message-ID: <CAM_iQpXtKisVu-QJA3=51oDJqEwEiuQu=np83RN0=r2A3wG0HA@mail.gmail.com> (raw)
In-Reply-To: <87eehu4157.fsf@cloudflare.com>

On Fri, Feb 5, 2021 at 2:09 PM Jakub Sitnicki <jakub@cloudflare.com> wrote:
>
> On Wed, Feb 03, 2021 at 05:16 AM CET, Cong Wang wrote:
> > From: Cong Wang <cong.wang@bytedance.com>
> >
> > Currently TCP_SKB_CB() is hard-coded in skmsg code, it certainly
> > won't work for any other non-TCP protocols. We can move them to
> > skb ext instead of playing with skb cb, which is harder to make
> > correct.
> >
> > Of course, except ->data_end, which is used by
> > sk_skb_convert_ctx_access() to adjust compile-time constant offset.
> > Fortunately, we can reuse the anonymous union where the field
> > 'tcp_tsorted_anchor' is and save/restore the overwritten part
> > before/after a brief use.
> >
> > Cc: John Fastabend <john.fastabend@gmail.com>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: Jakub Sitnicki <jakub@cloudflare.com>
> > Cc: Lorenz Bauer <lmb@cloudflare.com>
> > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> > ---
> >  include/linux/skbuff.h |  4 ++++
> >  include/linux/skmsg.h  | 45 ++++++++++++++++++++++++++++++++++++++++++
> >  include/net/tcp.h      | 25 -----------------------
> >  net/Kconfig            |  1 +
> >  net/core/filter.c      |  3 +--
> >  net/core/skbuff.c      |  7 +++++++
> >  net/core/skmsg.c       | 44 ++++++++++++++++++++++++++++-------------
> >  net/core/sock_map.c    | 12 +++++------
> >  8 files changed, 94 insertions(+), 47 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 46f901adf1a8..12a28268233a 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -755,6 +755,7 @@ struct sk_buff {
> >                       void            (*destructor)(struct sk_buff *skb);
> >               };
> >               struct list_head        tcp_tsorted_anchor;
> > +             void                    *data_end;
> >       };
>
> I think we can avoid `data_end` by computing it in BPF with the help of
> a scratch register. Similar to how we compute skb_shinfo(skb) in
> bpf_convert_shinfo_access(). Something like:

Sounds like an excellent idea! It is certainly much better if we can just
compute it at run-time. I will give this a try.

Thanks!

  reply	other threads:[~2021-02-08 18:58 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-03  4:16 [Patch bpf-next 00/19] sock_map: add non-TCP and cross-protocol support Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 01/19] bpf: rename BPF_STREAM_PARSER to BPF_SOCK_MAP Cong Wang
2021-02-05 10:32   ` Jakub Sitnicki
2021-02-09  1:40     ` Cong Wang
2021-02-08  8:21   ` John Fastabend
2021-02-08  9:50     ` Lorenz Bauer
2021-02-09  1:45     ` Cong Wang
2021-02-09  6:48       ` John Fastabend
2021-02-03  4:16 ` [Patch bpf-next 02/19] skmsg: get rid of struct sk_psock_parser Cong Wang
2021-02-05 11:25   ` Jakub Sitnicki
2021-02-08  8:39     ` John Fastabend
2021-02-09  0:19       ` Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 03/19] skmsg: use skb ext instead of TCP_SKB_CB Cong Wang
2021-02-05 22:09   ` Jakub Sitnicki
2021-02-08 18:56     ` Cong Wang [this message]
2021-02-03  4:16 ` [Patch bpf-next 04/19] sock_map: rename skb_parser and skb_verdict Cong Wang
2021-02-08  8:27   ` John Fastabend
2021-02-03  4:16 ` [Patch bpf-next 05/19] sock_map: introduce BPF_SK_SKB_VERDICT Cong Wang
2021-02-08  8:31   ` John Fastabend
2021-02-03  4:16 ` [Patch bpf-next 06/19] sock: introduce sk_prot->update_proto() Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 07/19] udp: implement ->sendmsg_locked() Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 08/19] udp: implement ->read_sock() for sockmap Cong Wang
2021-02-08  9:48   ` Lorenz Bauer
2021-02-09  1:35     ` Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 09/19] udp: add ->read_sock() and ->sendmsg_locked() to ipv6 Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 10/19] af_unix: implement ->sendmsg_locked for dgram socket Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 11/19] af_unix: implement ->read_sock() for sockmap Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 12/19] af_unix: implement ->update_proto() Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 13/19] af_unix: set TCP_ESTABLISHED for datagram sockets too Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 14/19] skmsg: extract __tcp_bpf_recvmsg() and tcp_bpf_wait_data() Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 15/19] udp: implement udp_bpf_recvmsg() for sockmap Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 16/19] af_unix: implement unix_dgram_bpf_recvmsg() Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 17/19] sock_map: update sock type checks Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 18/19] selftests/bpf: add test cases for unix and udp sockmap Cong Wang
2021-02-05 10:53   ` Jakub Sitnicki
2021-02-08 18:43     ` Cong Wang
2021-02-03  4:16 ` [Patch bpf-next 19/19] selftests/bpf: add test case for redirection between udp and unix Cong Wang
2021-02-03 17:48 ` [Patch bpf-next 00/19] sock_map: add non-TCP and cross-protocol support Alexei Starovoitov
2021-02-03 19:22   ` Cong Wang
2021-02-03 20:29     ` John Fastabend

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