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Date: Fri, 17 Jul 2020 17:40:33 +0100
From: Lorenz Bauer <lmb@...udflare.com>
To: Jakub Sitnicki <jakub@...udflare.com>
Cc: bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
kernel-team <kernel-team@...udflare.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Andrii Nakryiko <andriin@...com>,
Marek Majkowski <marek@...udflare.com>,
Martin KaFai Lau <kafai@...com>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH bpf-next v5 00/15] Run a BPF program on socket lookup
On Fri, 17 Jul 2020 at 11:35, Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> Changelog
> =========
> v4 -> v5:
> - Enforce BPF prog return value to be SK_DROP or SK_PASS. (Andrii)
> - Simplify prog runners now that only SK_DROP/PASS can be returned.
> - Enable bpf_perf_event_output from the start. (Andrii)
> - Drop patch
> "selftests/bpf: Rename test_sk_lookup_kern.c to test_ref_track_kern.c"
> - Remove tests for narrow loads from context at an offset wider in size
> than target field, while we are discussing how to fix it:
> https://lore.kernel.org/bpf/20200710173123.427983-1-jakub@cloudflare.com/
> - Rebase onto recent bpf-next (bfdfa51702de)
> - Other minor changes called out in per-patch changelogs,
> see patches: 2, 4, 6, 13-15
> - Carried over Andrii's Acks where nothing changed.
>
> v3 -> v4:
> - Reduce BPF prog return codes to SK_DROP/SK_PASS (Lorenz)
> - Default to drop on illegal return value from BPF prog (Lorenz)
> - Extend bpf_sk_assign to accept NULL socket pointer.
> - Switch to saner return values and add docs for new prog_array API (Andrii)
> - Add support for narrow loads from BPF context fields (Yonghong)
> - Fix broken build when IPv6 is compiled as a module (kernel test robot)
> - Fix null/wild-ptr-deref on BPF context access
> - Rebase to recent bpf-next (eef8a42d6ce0)
> - Other minor changes called out in per-patch changelogs,
> see patches 1-2, 4, 6, 8, 10-12, 14, 16
>
> v2 -> v3:
> - Switch to link-based program attachment
> - Support for multi-prog attachment
> - Ability to skip reuseport socket selection
> - Code on RX path is guarded by a static key
> - struct in6_addr's are no longer copied into BPF prog context
> - BPF prog context is initialized as late as possible
> - Changes called out in patches 1-2, 4, 6, 8, 10-14, 16
> - Patches dropped:
> 01/17 flow_dissector: Extract attach/detach/query helpers
> 03/17 inet: Store layer 4 protocol in inet_hashinfo
> 08/17 udp: Store layer 4 protocol in udp_table
>
> v1 -> v2:
> - Changes called out in patches 2, 13-15, 17
> - Rebase to recent bpf-next (b4563facdcae)
>
> RFCv2 -> v1:
>
> - Switch to fetching a socket from a map and selecting a socket with
> bpf_sk_assign, instead of having a dedicated helper that does both.
> - Run reuseport logic on sockets selected by BPF sk_lookup.
> - Allow BPF sk_lookup to fail the lookup with no match.
> - Go back to having just 2 hash table lookups in UDP.
>
> RFCv1 -> RFCv2:
>
> - Make socket lookup redirection map-based. BPF program now uses a
> dedicated helper and a SOCKARRAY map to select the socket to redirect to.
> A consequence of this change is that bpf_inet_lookup context is now
> read-only.
> - Look for connected UDP sockets before allowing redirection from BPF.
> This makes connected UDP socket work as expected in the presence of
> inet_lookup prog.
> - Share the code for BPF_PROG_{ATTACH,DETACH,QUERY} with flow_dissector,
> the only other per-netns BPF prog type.
>
> 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
> 14-15: verifier and selftests for sk_lookup
>
> Patches are also available on GH:
>
> https://github.com/jsitnicki/linux/commits/bpf-inet-lookup-v5
>
> 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].
>
> Thanks to the reviewers for their feedback to this patch series:
>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Andrii Nakryiko <andriin@...com>
> Cc: Lorenz Bauer <lmb@...udflare.com>
> Cc: Marek Majkowski <marek@...udflare.com>
> Cc: Martin KaFai Lau <kafai@...com>
> Cc: Yonghong Song <yhs@...com>
>
> -jkbs
Phew, I have to admit that at the patch that adds 2k lines of tests my
eyes glazed over a bit, but other than that: thank you for your hard
work!
For the series:
Reviewed-by: Lorenz Bauer <lmb@...udflare.com>
>
> [RFCv1] https://lore.kernel.org/bpf/20190618130050.8344-1-jakub@cloudflare.com/
> [RFCv2] https://lore.kernel.org/bpf/20190828072250.29828-1-jakub@cloudflare.com/
> [v1] https://lore.kernel.org/bpf/20200511185218.1422406-18-jakub@cloudflare.com/
> [v2] https://lore.kernel.org/bpf/20200506125514.1020829-1-jakub@cloudflare.com/
> [v3] https://lore.kernel.org/bpf/20200702092416.11961-1-jakub@cloudflare.com/
> [v4] https://lore.kernel.org/bpf/20200713174654.642628-1-jakub@cloudflare.com/
>
> Jakub Sitnicki (15):
> bpf, netns: Handle multiple link attachments
> bpf: Introduce SK_LOOKUP program type with a dedicated attach point
> inet: Extract helper for selecting socket from reuseport group
> inet: Run SK_LOOKUP BPF program on socket lookup
> inet6: Extract helper for selecting socket from reuseport group
> inet6: Run SK_LOOKUP BPF program on socket lookup
> udp: Extract helper for selecting socket from reuseport group
> udp: Run SK_LOOKUP BPF program on socket lookup
> udp6: Extract helper for selecting socket from reuseport group
> udp6: Run SK_LOOKUP BPF program on socket lookup
> bpf: Sync linux/bpf.h to tools/
> libbpf: Add support for SK_LOOKUP program type
> tools/bpftool: Add name mappings for SK_LOOKUP prog and attach type
> selftests/bpf: Add verifier tests for bpf_sk_lookup context access
> selftests/bpf: Tests for BPF_SK_LOOKUP attach point
>
> include/linux/bpf-netns.h | 3 +
> include/linux/bpf.h | 4 +
> include/linux/bpf_types.h | 2 +
> include/linux/filter.h | 147 ++
> include/uapi/linux/bpf.h | 77 +
> kernel/bpf/core.c | 55 +
> kernel/bpf/net_namespace.c | 127 +-
> kernel/bpf/syscall.c | 9 +
> kernel/bpf/verifier.c | 13 +-
> net/core/filter.c | 183 +++
> net/ipv4/inet_hashtables.c | 60 +-
> net/ipv4/udp.c | 93 +-
> net/ipv6/inet6_hashtables.c | 66 +-
> net/ipv6/udp.c | 97 +-
> scripts/bpf_helpers_doc.py | 9 +-
> .../bpftool/Documentation/bpftool-prog.rst | 2 +-
> tools/bpf/bpftool/bash-completion/bpftool | 2 +-
> tools/bpf/bpftool/common.c | 1 +
> tools/bpf/bpftool/prog.c | 3 +-
> tools/include/uapi/linux/bpf.h | 77 +
> tools/lib/bpf/libbpf.c | 3 +
> tools/lib/bpf/libbpf.h | 2 +
> tools/lib/bpf/libbpf.map | 2 +
> tools/lib/bpf/libbpf_probes.c | 3 +
> tools/testing/selftests/bpf/network_helpers.c | 58 +-
> tools/testing/selftests/bpf/network_helpers.h | 2 +
> .../selftests/bpf/prog_tests/sk_lookup.c | 1282 +++++++++++++++++
> .../selftests/bpf/progs/test_sk_lookup.c | 641 +++++++++
> .../selftests/bpf/verifier/ctx_sk_lookup.c | 492 +++++++
> 29 files changed, 3418 insertions(+), 97 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/sk_lookup.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_sk_lookup.c
> create mode 100644 tools/testing/selftests/bpf/verifier/ctx_sk_lookup.c
>
> --
> 2.25.4
>
--
Lorenz Bauer | Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK
www.cloudflare.com
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