From: David Miller <davem@davemloft.net>
To: john.fastabend@gmail.com
Cc: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
davejwatson@fb.com
Subject: Re: [bpf-next PATCH 05/16] bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data
Date: Mon, 05 Mar 2018 16:40:08 -0500 (EST) [thread overview]
Message-ID: <20180305.164008.2006986778756330199.davem@davemloft.net> (raw)
In-Reply-To: <20180305195122.6612.78322.stgit@john-Precision-Tower-5810>
From: John Fastabend <john.fastabend@gmail.com>
Date: Mon, 05 Mar 2018 11:51:22 -0800
> BPF_PROG_TYPE_SK_MSG supports only two return codes SK_PASS and
> SK_DROP. Returning SK_DROP free's the copied data in the sendmsg
> case and in the sendpage case leaves the data untouched. Both cases
> return -EACESS to the user. Returning SK_PASS will allow the msg to
> be sent.
>
> In the sendmsg case data is copied into kernel space buffers before
> running the BPF program. In the sendpage case data is never copied.
> The implication being users may change data after BPF programs run in
> the sendpage case. (A flag will be added to always copy shortly
> if the copy must always be performed).
I don't see how the sendpage case can be right.
The user can asynchronously change the page contents whenever they
want, and if the BPF program runs on the old contents then the verdict
is not for what actually ends up being sent on the socket.
There is really no way to cheaply freeze the page contents other than
to make a copy.
next prev parent reply other threads:[~2018-03-05 21:40 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-05 19:50 [bpf-next PATCH 00/16] bpf,sockmap: sendmsg/sendfile ULP John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 01/16] sock: make static tls function alloc_sg generic sock helper John Fastabend
2018-03-05 21:32 ` David Miller
2018-03-05 19:51 ` [bpf-next PATCH 02/16] sockmap: convert refcnt to an atomic refcnt John Fastabend
2018-03-05 21:34 ` David Miller
2018-03-05 19:51 ` [bpf-next PATCH 03/16] net: do_tcp_sendpages flag to avoid SKBTX_SHARED_FRAG John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 04/16] net: generalize sk_alloc_sg to work with scatterlist rings John Fastabend
2018-03-05 21:35 ` David Miller
2018-03-05 19:51 ` [bpf-next PATCH 05/16] bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data John Fastabend
2018-03-05 21:40 ` David Miller [this message]
2018-03-05 22:53 ` John Fastabend
2018-03-06 5:42 ` David Miller
2018-03-06 6:22 ` John Fastabend
2018-03-06 6:42 ` David Miller
2018-03-06 7:06 ` John Fastabend
2018-03-06 15:47 ` David Miller
2018-03-06 18:18 ` John Fastabend
2018-03-07 3:25 ` John Fastabend
2018-03-07 4:41 ` David Miller
2018-03-07 13:03 ` Daniel Borkmann
2018-03-05 19:51 ` [bpf-next PATCH 06/16] bpf: sockmap, add bpf_msg_apply_bytes() helper John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 07/16] bpf: sockmap, add msg_cork_bytes() helper John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 08/16] bpf: add map tests for BPF_PROG_TYPE_SK_MSG John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 09/16] bpf: add verifier " John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 10/16] bpf: sockmap sample, add option to attach SK_MSG program John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 11/16] bpf: sockmap sample, add sendfile test John Fastabend
2018-03-05 19:51 ` [bpf-next PATCH 12/16] bpf: sockmap sample, add data verification option John Fastabend
2018-03-05 19:52 ` [bpf-next PATCH 13/16] bpf: sockmap, add sample option to test apply_bytes helper John Fastabend
2018-03-05 19:52 ` [bpf-next PATCH 14/16] bpf: sockmap sample support for bpf_msg_cork_bytes() John Fastabend
2018-03-05 19:52 ` [bpf-next PATCH 15/16] sockmap: add SK_DROP tests John Fastabend
2018-03-05 19:52 ` [bpf-next PATCH 16/16] bpf: sockmap test script John Fastabend
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