From: Alan Maguire <alan.maguire@oracle.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
Marek Majkowski <marek@cloudflare.com>,
Lorenz Bauer <lmb@cloudflare.com>,
David Miller <davem@davemloft.net>,
Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls
Date: Wed, 2 Oct 2019 16:10:02 +0100 (BST) [thread overview]
Message-ID: <alpine.LRH.2.20.1910021540270.24629@dhcp-10-175-191-98.vpn.oracle.com> (raw)
In-Reply-To: <157002302448.1302756.5727756706334050763.stgit@alrua-x1>
[-- Attachment #1: Type: text/plain, Size: 2193 bytes --]
On Wed, 2 Oct 2019, Toke Høiland-Jørgensen wrote:
> This series adds support for executing multiple XDP programs on a single
> interface in sequence, through the use of chain calls, as discussed at the Linux
> Plumbers Conference last month:
>
> https://linuxplumbersconf.org/event/4/contributions/460/
>
> # HIGH-LEVEL IDEA
>
> The basic idea is to express the chain call sequence through a special map type,
> which contains a mapping from a (program, return code) tuple to another program
> to run in next in the sequence. Userspace can populate this map to express
> arbitrary call sequences, and update the sequence by updating or replacing the
> map.
>
> The actual execution of the program sequence is done in bpf_prog_run_xdp(),
> which will lookup the chain sequence map, and if found, will loop through calls
> to BPF_PROG_RUN, looking up the next XDP program in the sequence based on the
> previous program ID and return code.
>
> An XDP chain call map can be installed on an interface by means of a new netlink
> attribute containing an fd pointing to a chain call map. This can be supplied
> along with the XDP prog fd, so that a chain map is always installed together
> with an XDP program.
>
This is great stuff Toke! One thing that wasn't immediately clear to me -
and this may be just me - is the relationship between program
behaviour for the XDP_DROP case and chain call execution. My initial
thought was that a program in the chain XDP_DROP'ping the packet would
terminate the call chain, but on looking at patch #4 it seems that
the only way the call chain execution is terminated is if
- XDP_ABORTED is returned from a program in the call chain; or
- the map entry for the next program (determined by the return value
of the current program) is empty; or
- we run out of entries in the map
The return value of the last-executed program in the chain seems
to be what determines packet processing behaviour after executing
the chain (_DROP, _TX, _PASS, etc). So there's no way to both XDP_PASS
and XDP_TX a packet from the same chain, right? Just want to make
sure I've got the semantics correct. Thanks!
Alan
next prev parent reply other threads:[~2019-10-02 15:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 13:30 [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 1/9] hashtab: Add new bpf_map_fd_put_value op Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 2/9] xdp: Add new xdp_chain_map type for specifying XDP call sequences Toke Høiland-Jørgensen
2019-10-02 15:50 ` Lorenz Bauer
2019-10-02 18:25 ` Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 3/9] xdp: Support setting and getting device chain map Toke Høiland-Jørgensen
2019-10-02 15:50 ` Lorenz Bauer
2019-10-02 18:32 ` Toke Høiland-Jørgensen
2019-10-02 18:07 ` kbuild test robot
2019-10-02 18:29 ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 4/9] xdp: Implement chain call logic to support multiple programs on one interface Toke Høiland-Jørgensen
2019-10-02 17:33 ` kbuild test robot
2019-10-02 17:53 ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 5/9] tools/include/uapi: Add XDP chain map definitions Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 6/9] tools/libbpf_probes: Add support for xdp_chain map type Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 7/9] bpftool: Add definitions " Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 8/9] libbpf: Add support for setting and getting XDP chain maps Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 9/9] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen
2019-10-02 15:10 ` Alan Maguire [this message]
2019-10-02 15:33 ` [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through " Toke Høiland-Jørgensen
2019-10-02 16:34 ` John Fastabend
2019-10-02 18:33 ` Toke Høiland-Jørgensen
2019-10-02 20:34 ` John Fastabend
2019-10-03 7:48 ` Toke Høiland-Jørgensen
2019-10-03 10:09 ` Jesper Dangaard Brouer
2019-10-03 19:45 ` John Fastabend
2019-10-02 16:35 ` Lorenz Bauer
2019-10-02 18:54 ` Toke Høiland-Jørgensen
2019-10-02 16:43 ` John Fastabend
2019-10-02 19:09 ` Toke Høiland-Jørgensen
2019-10-02 19:15 ` Daniel Borkmann
2019-10-02 19:29 ` Toke Høiland-Jørgensen
2019-10-02 19:46 ` Alexei Starovoitov
2019-10-03 7:58 ` Toke Høiland-Jørgensen
2019-10-02 18:38 ` Song Liu
2019-10-02 18:54 ` Song Liu
2019-10-02 19:25 ` Toke Høiland-Jørgensen
2019-10-03 8:53 ` Jesper Dangaard Brouer
2019-10-03 14:03 ` Alexei Starovoitov
2019-10-03 14:33 ` Toke Høiland-Jørgensen
2019-10-03 14:53 ` Edward Cree
2019-10-03 18:49 ` Jesper Dangaard Brouer
2019-10-03 19:35 ` John Fastabend
2019-10-04 8:09 ` Toke Høiland-Jørgensen
2019-10-04 10:34 ` Edward Cree
2019-10-04 15:58 ` Lorenz Bauer
2019-10-07 16:43 ` Edward Cree
2019-10-07 17:12 ` Lorenz Bauer
2019-10-07 19:21 ` Edward Cree
2019-10-07 21:01 ` Alexei Starovoitov
2019-10-02 19:23 ` Toke Høiland-Jørgensen
2019-10-02 19:49 ` Song Liu
2019-10-03 7:59 ` Toke Høiland-Jørgensen
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