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From: Martin KaFai Lau <kafai@fb.com>
To: Eric Dumazet <edumazet@google.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	kernel-team <kernel-team@fb.com>, Lawrence Brakmo <brakmo@fb.com>,
	Neal Cardwell <ncardwell@google.com>,
	netdev <netdev@vger.kernel.org>,
	Yuchung Cheng <ycheng@google.com>
Subject: Re: [PATCH bpf-next 02/10] tcp: bpf: Parse BPF experimental header option
Date: Sun, 28 Jun 2020 17:45:45 -0700	[thread overview]
Message-ID: <20200629004545.cpiiowlhgnk527f3@kafai-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <CANn89iK50rqOVy=PmKO-Fe1D-HsHjp4zj-feevouQ2hc1GAQ9Q@mail.gmail.com>

On Sat, Jun 27, 2020 at 10:17:26AM -0700, Eric Dumazet wrote:
[ ... ]

> It seems strange that we want to add code in TCP stack only to cover a
> limited use case (kind 254 and 0xEB9F magic)
> 
> For something like the work Petar Penkov did (to be able to generate
> SYNCOOKIES from XDP), we do not go through tcp_parse_options() and BPF
> program
> would have to implement its own parsing (without having an SKB at
> hand), probably calling a helper function, with no
> TCP_SKB_CB(skb)->bpf_hdr_opt_off.
> 
> This patch is hard coding a specific option and will prevent anyone
> using private option(s) from using this infrastructure in the future,
> yet paying the extra overhead.
There is a discussion in patch 4 about not limiting this patch set
to option kind 254.  That will affect the usefulness of bpf_hdr_opt_off.

> 
> TCP_SKB_CB(skb) is tight, I would prefer keeping the space in it for
> standard TCP stack features.
> 
> If an optional BPF program needs to re-parse the TCP options to find a
> specific option, maybe the extra cost is noise (especially if this is
> only for SYN & SYNACK packets) ?
> 
> Thanks

  parent reply	other threads:[~2020-06-29  0:46 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-26 17:55 [PATCH bpf-next 00/10] BPF TCP header options Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 01/10] tcp: Use a struct to represent a saved_syn Martin KaFai Lau
2020-06-27 17:41   ` Eric Dumazet
2020-06-30 23:24     ` Martin KaFai Lau
2020-06-30 23:35       ` Eric Dumazet
2020-06-26 17:55 ` [PATCH bpf-next 02/10] tcp: bpf: Parse BPF experimental header option Martin KaFai Lau
2020-06-27 16:44   ` Eric Dumazet
2020-06-27 17:17   ` Eric Dumazet
2020-06-28 23:44     ` Martin KaFai Lau
2020-06-29  0:45     ` Martin KaFai Lau [this message]
2020-06-26 17:55 ` [PATCH bpf-next 03/10] bpf: sock_ops: Change some members of sock_ops_kern from u32 to u8 Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 04/10] bpf: tcp: Allow bpf prog to write and parse BPF TCP header option Martin KaFai Lau
2020-06-28 18:24   ` Alexei Starovoitov
2020-06-29  0:34     ` Martin KaFai Lau
2020-07-02  5:31       ` Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 05/10] bpf: selftests: A few improvements to network_helpers.c Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 06/10] bpf: selftests: Add fastopen_connect to network_helpers Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 07/10] bpf: selftests: Restore netns after each test Martin KaFai Lau
2020-06-26 22:45   ` Andrii Nakryiko
2020-06-27  0:23     ` Martin KaFai Lau
2020-06-27 20:31       ` Andrii Nakryiko
2020-06-29 18:00         ` Martin KaFai Lau
2020-06-29 18:13           ` Andrii Nakryiko
2020-06-29 18:24             ` Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 08/10] bpf: selftests: tcp header options Martin KaFai Lau
2020-06-26 17:55 ` [PATCH bpf-next 09/10] tcp: bpf: Add TCP_BPF_DELACK_MAX and TCP_BPF_RTO_MIN to bpf_setsockopt Martin KaFai Lau
2020-06-27 17:30   ` Eric Dumazet
2020-06-26 17:56 ` [PATCH bpf-next 10/10] bpf: selftest: Add test for TCP_BPF_DELACK_MAX and TCP_BPF_RTO_MIN Martin KaFai Lau

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