Re: [PATCH bpf-next v4 00/16] Run a BPF program on socket lookup

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Mon, Jul 13, 2020 at 10:47 AM Jakub Sitnicki <jakub@cloudflare.com> wrote:
>
> Dependencies
> ============
>
> This patch series depends on:
>
> 1. 'bpf-multi-prog-prep' series in 'bpf' [0]
>    (commit 951f38cf0835 ("Merge branch 'bpf-multi-prog-prep'"))
> 2. "bpf: Shift and mask loads narrower than context field size" patch
>    https://lore.kernel.org/bpf/20200710173123.427983-1-jakub@cloudflare.com/
>

[...]

>
> Overview
> ========
>
> This series proposes a new BPF program type named BPF_PROG_TYPE_SK_LOOKUP,
> or BPF sk_lookup for short.
>
> BPF sk_lookup program runs when transport layer is looking up a listening
> socket for a new connection request (TCP), or when looking up an
> unconnected socket for a packet (UDP).
>
> This serves as a mechanism to overcome the limits of what bind() API allows
> to express. Two use-cases driving this work are:
>
>  (1) steer packets destined to an IP range, fixed port to a single socket
>
>      192.0.2.0/24, port 80 -> NGINX socket
>
>  (2) steer packets destined to an IP address, any port to a single socket
>
>      198.51.100.1, any port -> L7 proxy socket
>
> In its context, program receives information about the packet that
> triggered the socket lookup. Namely IP version, L4 protocol identifier, and
> address 4-tuple.
>
> To select a socket BPF program fetches it from a map holding socket
> references, like SOCKMAP or SOCKHASH, calls bpf_sk_assign(ctx, sk, ...)
> helper to record the selection, and returns SK_PASS code. Transport layer
> then uses the selected socket as a result of socket lookup.
>
> Alternatively, program can also fail the lookup (SK_DROP), or let the
> lookup continue as usual (SK_PASS without selecting a socket).
>
> This lets the user match packets with listening (TCP) or receiving (UDP)
> sockets freely at the last possible point on the receive path, where we
> know that packets are destined for local delivery after undergoing
> policing, filtering, and routing.
>
> Program is attached to a network namespace, similar to BPF flow_dissector.
> We add a new attach type, BPF_SK_LOOKUP, for this. Multiple programs can be
> attached at the same time, in which case their return values are aggregated
> according the rules outlined in patch #4 description.
>
> Series structure
> ================
>
> Patches are organized as so:
>
>  1: enables multiple link-based prog attachments for bpf-netns
>  2: introduces sk_lookup program type
>  3-4: hook up the program to run on ipv4/tcp socket lookup
>  5-6: hook up the program to run on ipv6/tcp socket lookup
>  7-8: hook up the program to run on ipv4/udp socket lookup
>  9-10: hook up the program to run on ipv6/udp socket lookup
>  11-13: libbpf & bpftool support for sk_lookup
>  14-16: verifier and selftests for sk_lookup
>
> Patches are also available on GH:
>
>   https://github.com/jsitnicki/linux/commits/bpf-inet-lookup-v4
>
> Follow-up work
> ==============
>
> I'll follow up with below items, which IMHO don't block the review:
>
> - benchmark results for udp6 small packet flood scenario,
> - user docs for new BPF prog type, Documentation/bpf/prog_sk_lookup.rst,
> - timeout for accept() in tests after extending network_helper.[ch].
>

Looks good to me overall. I've looked through networking-specific code
and didn't spot anything, but I might be missing some subtleties,
hopefully not, though.

I left a few suggestions, please take a look, and if they make sense,
apply them in the follow up(s). Thanks!

For the series:

Acked-by: Andrii Nakryiko <andriin@fb.com>

> Thanks to the reviewers for their feedback to this patch series:
>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andriin@fb.com>
> Cc: Lorenz Bauer <lmb@cloudflare.com>
> Cc: Marek Majkowski <marek@cloudflare.com>
> Cc: Martin KaFai Lau <kafai@fb.com>
> Cc: Yonghong Song <yhs@fb.com>
>
> -jkbs
>

[...]