From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Stringer Subject: [RFC bpf-next 00/11] Add socket lookup support Date: Wed, 9 May 2018 14:06:58 -0700 Message-ID: <20180509210709.7201-1-joe@wand.net.nz> Cc: netdev@vger.kernel.org, ast@kernel.org, john.fastabend@gmail.com, tgraf@suug.ch, kafai@fb.com To: daniel@iogearbox.net Return-path: Received: from mail-ot0-f171.google.com ([74.125.82.171]:38562 "EHLO mail-ot0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964849AbeEIVHX (ORCPT ); Wed, 9 May 2018 17:07:23 -0400 Received: by mail-ot0-f171.google.com with SMTP id n3-v6so5494587ota.5 for ; Wed, 09 May 2018 14:07:23 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: This series proposes a new helper for the BPF API which allows BPF programs to perform lookups for sockets in a network namespace. This would allow programs to determine early on in processing whether the stack is expecting to receive the packet, and perform some action (eg drop, forward somewhere) based on this information. The series is structured roughly into: * Misc refactor * Add the socket pointer type * Add reference tracking to ensure that socket references are freed * Extend the BPF API to add sk_lookup() / sk_release() functions * Add tests/documentation The helper proposed in this series includes a parameter for a tuple which must be filled in by the caller to determine the socket to look up. The simplest case would be filling with the contents of the packet, ie mapping the packet's 5-tuple into the parameter. In common cases, it may alternatively be useful to reverse the direction of the tuple and perform a lookup, to find the socket that initiates this connection; and if the BPF program ever performs a form of IP address translation, it may further be useful to be able to look up arbitrary tuples that are not based upon the packet, but instead based on state held in BPF maps or hardcoded in the BPF program. Currently, access into the socket's fields are limited to those which are otherwise already accessible, and are restricted to read-only access. A few open points: * Currently, the lookup interface only returns either a valid socket or a NULL pointer. This means that if there is any kind of issue with the tuple, such as it provides an unsupported protocol number, or the socket can't be found, then we are unable to differentiate these cases from one another. One natural approach to improve this could be to return an ERR_PTR from the bpf_sk_lookup() helper. This would be more complicated but maybe it's worthwhile. * No ordering is defined between sockets. If the tuple could find multiple sockets, then it will arbitrarily return one. It is up to the caller to handle this. If we wish to handle this more reliably in future, we could encode an ordering preference in the flags field. * Currently this helper is only defined for TC hook point, but it should also be valid at XDP and perhaps some other hooks. Joe Stringer (11): bpf: Add iterator for spilled registers bpf: Simplify ptr_min_max_vals adjustment bpf: Generalize ptr_or_null regs check bpf: Add PTR_TO_SOCKET verifier type bpf: Macrofy stack state copy bpf: Add reference tracking to verifier bpf: Add helper to retrieve socket in BPF selftests/bpf: Add tests for reference tracking libbpf: Support loading individual progs selftests/bpf: Add C tests for reference tracking Documentation: Describe bpf reference tracking Documentation/networking/filter.txt | 64 +++ include/linux/bpf.h | 19 +- include/linux/bpf_verifier.h | 31 +- include/uapi/linux/bpf.h | 39 +- kernel/bpf/verifier.c | 548 ++++++++++++++++++---- net/core/filter.c | 132 +++++- tools/include/uapi/linux/bpf.h | 40 +- tools/lib/bpf/libbpf.c | 4 +- tools/lib/bpf/libbpf.h | 3 + tools/testing/selftests/bpf/Makefile | 2 +- tools/testing/selftests/bpf/bpf_helpers.h | 7 + tools/testing/selftests/bpf/test_progs.c | 38 ++ tools/testing/selftests/bpf/test_sk_lookup_kern.c | 127 +++++ tools/testing/selftests/bpf/test_verifier.c | 373 ++++++++++++++- 14 files changed, 1299 insertions(+), 128 deletions(-) create mode 100644 tools/testing/selftests/bpf/test_sk_lookup_kern.c -- 2.14.1