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(-)