From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: John Fastabend <john.fastabend@gmail.com>
Cc: davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
davejwatson@fb.com, netdev@vger.kernel.org
Subject: Re: [bpf-next PATCH v2 06/18] bpf: sockmap, add bpf_msg_apply_bytes() helper
Date: Thu, 15 Mar 2018 14:45:56 -0700 [thread overview]
Message-ID: <20180315214554.2gspfp255qqxbjcb@ast-mbp> (raw)
In-Reply-To: <20180312192334.8039.98220.stgit@john-Precision-Tower-5810>
On Mon, Mar 12, 2018 at 12:23:34PM -0700, John Fastabend wrote:
> A single sendmsg or sendfile system call can contain multiple logical
> messages that a BPF program may want to read and apply a verdict. But,
> without an apply_bytes helper any verdict on the data applies to all
> bytes in the sendmsg/sendfile. Alternatively, a BPF program may only
> care to read the first N bytes of a msg. If the payload is large say
> MB or even GB setting up and calling the BPF program repeatedly for
> all bytes, even though the verdict is already known, creates
> unnecessary overhead.
>
> To allow BPF programs to control how many bytes a given verdict
> applies to we implement a bpf_msg_apply_bytes() helper. When called
> from within a BPF program this sets a counter, internal to the
> BPF infrastructure, that applies the last verdict to the next N
> bytes. If the N is smaller than the current data being processed
> from a sendmsg/sendfile call, the first N bytes will be sent and
> the BPF program will be re-run with start_data pointing to the N+1
> byte. If N is larger than the current data being processed the
> BPF verdict will be applied to multiple sendmsg/sendfile calls
> until N bytes are consumed.
>
> Note1 if a socket closes with apply_bytes counter non-zero this
> is not a problem because data is not being buffered for N bytes
> and is sent as its received.
>
> Note2 if this is operating in the sendpage context the data
> pointers may be zeroed after this call if the apply walks beyond
> a msg_pull_data() call specified data range. (helper implemented
> shortly in this series).
instead of 'shortly in this seris' you meant 'implemented earlier'?
patch 5 handles it, but it's set here, right?
The semantics of the helper looks great.
next prev parent reply other threads:[~2018-03-15 21:46 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-12 19:23 [bpf-next PATCH v2 00/18] bpf,sockmap: sendmsg/sendfile ULP John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 01/18] sock: make static tls function alloc_sg generic sock helper John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 02/18] sockmap: convert refcnt to an atomic refcnt John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 03/18] net: do_tcp_sendpages flag to avoid SKBTX_SHARED_FRAG John Fastabend
2018-03-15 18:40 ` David Miller
2018-03-12 19:23 ` [bpf-next PATCH v2 04/18] net: generalize sk_alloc_sg to work with scatterlist rings John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 05/18] bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data John Fastabend
2018-03-15 18:41 ` David Miller
2018-03-15 21:59 ` Alexei Starovoitov
2018-03-15 22:08 ` John Fastabend
2018-03-15 22:17 ` Daniel Borkmann
2018-03-15 22:20 ` Alexei Starovoitov
2018-03-15 22:55 ` Daniel Borkmann
2018-03-15 23:06 ` Alexei Starovoitov
2018-03-16 0:37 ` Daniel Borkmann
2018-03-16 16:47 ` John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 06/18] bpf: sockmap, add bpf_msg_apply_bytes() helper John Fastabend
2018-03-15 18:41 ` David Miller
2018-03-15 20:32 ` Daniel Borkmann
2018-03-15 22:02 ` John Fastabend
2018-03-15 21:45 ` Alexei Starovoitov [this message]
2018-03-15 21:59 ` John Fastabend
2018-03-12 19:23 ` [bpf-next PATCH v2 07/18] bpf: sockmap, add msg_cork_bytes() helper John Fastabend
2018-03-15 18:41 ` David Miller
2018-03-12 19:23 ` [bpf-next PATCH v2 08/18] bpf: sk_msg program helper bpf_sk_msg_pull_data John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-15 20:25 ` Daniel Borkmann
2018-03-12 19:23 ` [bpf-next PATCH v2 09/18] bpf: add map tests for BPF_PROG_TYPE_SK_MSG John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:23 ` [bpf-next PATCH v2 10/18] bpf: add verifier " John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 11/18] bpf: sockmap sample, add option to attach SK_MSG program John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 12/18] bpf: sockmap sample, add sendfile test John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 13/18] bpf: sockmap sample, add data verification option John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 14/18] bpf: sockmap, add sample option to test apply_bytes helper John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 15/18] bpf: sockmap sample support for bpf_msg_cork_bytes() John Fastabend
2018-03-15 18:42 ` David Miller
2018-03-15 20:15 ` Alexei Starovoitov
2018-03-15 22:04 ` John Fastabend
2018-03-12 19:24 ` [bpf-next PATCH v2 16/18] bpf: sockmap add SK_DROP tests John Fastabend
2018-03-15 18:43 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 17/18] bpf: sockmap sample test for bpf_msg_pull_data John Fastabend
2018-03-15 18:43 ` David Miller
2018-03-12 19:24 ` [bpf-next PATCH v2 18/18] bpf: sockmap test script John Fastabend
2018-03-15 18:43 ` David Miller
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