linux-kernel - [PATCH 0/2] bpf, net: Allow setting SO

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Message-ID: <20230703175048.151683-1-jthinz@mailbox.tu-berlin.de>
Date:   Mon, 3 Jul 2023 19:50:44 +0200
From:   Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>
To:     <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-kselftest@...r.kernel.org>
CC:     Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Deepa Dinamani <deepa.kernel@...il.com>
Subject: [PATCH 0/2] bpf, net: Allow setting SO_TIMESTAMPING* from BPF

BPF applications, e.g., a TCP congestion control, might benefit from
precise packet timestamps. These timestamps are already available in
__sk_buff and bpf_sock_ops, but could not be requested: A BPF program
was not allowed to set SO_TIMESTAMPING* on a socket. This change enables
BPF programs to actively request the generation of timestamps from a
stream socket.

To reuse the setget_sockopt BPF prog test for
bpf_{get,set}sockopt(SO_TIMESTAMPING_NEW), also implement the missing
getsockopt(SO_TIMESTAMPING_NEW) in the network stack.

I reckon the way I added getsockopt(SO_TIMESTAMPING_NEW) causes an API
change: For existing users that set SO_TIMESTAMPING_NEW but queried
SO_TIMESTAMPING_OLD afterwards, it would now look as if no timestamping
flags have been set. Is this an acceptable change? If not, I’m happy to
change getsockopt() to only be strict about the newly-implemented
getsockopt(SO_TIMESTAMPING_NEW), or not distinguish between
SO_TIMESTAMPING_NEW and SO_TIMESTAMPING_OLD at all.

Jörn-Thorben Hinz (2):
  net: Implement missing getsockopt(SO_TIMESTAMPING_NEW)
  bpf: Allow setting SO_TIMESTAMPING* with bpf_setsockopt()

 include/uapi/linux/bpf.h                            | 3 ++-
 net/core/filter.c                                   | 2 ++
 net/core/sock.c                                     | 9 +++++++--
 tools/include/uapi/linux/bpf.h                      | 3 ++-
 tools/testing/selftests/bpf/progs/bpf_tracing_net.h | 2 ++
 tools/testing/selftests/bpf/progs/setget_sockopt.c  | 4 ++++
 6 files changed, 19 insertions(+), 4 deletions(-)

-- 
2.39.2