A BPF application, e.g., a TCP congestion control, might benefit from or even require precise (=hardware) packet timestamps. These timestamps are already available through __sk_buff.hwtstamp and bpf_sock_ops.skb_hwtstamp, but could not be requested: BPF programs were not allowed to set SO_TIMESTAMPING* on sockets.
Enable BPF programs to actively request the generation of timestamps from a stream socket. The also required ioctl(SIOCSHWTSTAMP) on the network device must still be done separately, in user space.
This patch had previously been submitted in a two-part series (first link below). The second patch has been independently applied in commit 7f6ca95d16b9 ("net: Implement missing getsockopt(SO_TIMESTAMPING_NEW)") (second link below).
On the earlier submission, there was the open question whether to only allow, thus enforce, SO_TIMESTAMPING_NEW in this patch:
For a BPF program, this won't make a difference: A timestamp, when accessed through the fields mentioned above, is directly read from skb_shared_info.hwtstamps, independent of the places where NEW/OLD is relevant. See bpf_convert_ctx_access() besides others.
I am unsure, though, when it comes to the interconnection of user space and BPF "space", when both are interested in the timestamps. I think it would cause an unsolvable conflict when user space is bound to use SO_TIMESTAMPING_OLD with a BPF program only allowed to set SO_TIMESTAMPING_NEW *on the same socket*? Please correct me if I'm mistaken.
Link: https://lore.kernel.org/lkml/20230703175048.151683-1-jthinz@mailbox.tu-berli... Link: https://lore.kernel.org/all/20231221231901.67003-1-jthinz@mailbox.tu-berlin.... Cc: Arnd Bergmann arnd@arndb.de Cc: Deepa Dinamani deepa.kernel@gmail.com Cc: Willem de Bruijn willemdebruijn.kernel@gmail.com Signed-off-by: Jörn-Thorben Hinz j-t.hinz@alumni.tu-berlin.de --- include/uapi/linux/bpf.h | 3 ++- net/core/filter.c | 2 ++ 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 ++++ 5 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 754e68ca8744..8825d0648efe 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2734,7 +2734,8 @@ union bpf_attr { * **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**, * **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**, * **SO_BINDTODEVICE**, **SO_KEEPALIVE**, **SO_REUSEADDR**, - * **SO_REUSEPORT**, **SO_BINDTOIFINDEX**, **SO_TXREHASH**. + * **SO_REUSEPORT**, **SO_BINDTOIFINDEX**, **SO_TXREHASH**, + * **SO_TIMESTAMPING_NEW**, **SO_TIMESTAMPING_OLD**. * * **IPPROTO_TCP**, which supports the following *optname*\ s: * **TCP_CONGESTION**, **TCP_BPF_IW**, * **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**, diff --git a/net/core/filter.c b/net/core/filter.c index 8c9f67c81e22..4f5280874fd8 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5144,6 +5144,8 @@ static int sol_socket_sockopt(struct sock *sk, int optname, case SO_MAX_PACING_RATE: case SO_BINDTOIFINDEX: case SO_TXREHASH: + case SO_TIMESTAMPING_NEW: + case SO_TIMESTAMPING_OLD: if (*optlen != sizeof(int)) return -EINVAL; break; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 7f24d898efbb..09eaafa6ab43 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2734,7 +2734,8 @@ union bpf_attr { * **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**, * **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**, * **SO_BINDTODEVICE**, **SO_KEEPALIVE**, **SO_REUSEADDR**, - * **SO_REUSEPORT**, **SO_BINDTOIFINDEX**, **SO_TXREHASH**. + * **SO_REUSEPORT**, **SO_BINDTOIFINDEX**, **SO_TXREHASH**, + * **SO_TIMESTAMPING_NEW**, **SO_TIMESTAMPING_OLD**. * * **IPPROTO_TCP**, which supports the following *optname*\ s: * **TCP_CONGESTION**, **TCP_BPF_IW**, * **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**, diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h index 1bdc680b0e0e..95f5f169819e 100644 --- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h +++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h @@ -15,8 +15,10 @@ #define SO_RCVLOWAT 18 #define SO_BINDTODEVICE 25 #define SO_MARK 36 +#define SO_TIMESTAMPING_OLD 37 #define SO_MAX_PACING_RATE 47 #define SO_BINDTOIFINDEX 62 +#define SO_TIMESTAMPING_NEW 65 #define SO_TXREHASH 74 #define __SO_ACCEPTCON (1 << 16)
diff --git a/tools/testing/selftests/bpf/progs/setget_sockopt.c b/tools/testing/selftests/bpf/progs/setget_sockopt.c index 7a438600ae98..54205d10793c 100644 --- a/tools/testing/selftests/bpf/progs/setget_sockopt.c +++ b/tools/testing/selftests/bpf/progs/setget_sockopt.c @@ -48,6 +48,10 @@ static const struct sockopt_test sol_socket_tests[] = { { .opt = SO_MARK, .new = 0xeb9f, .expected = 0xeb9f, }, { .opt = SO_MAX_PACING_RATE, .new = 0xeb9f, .expected = 0xeb9f, }, { .opt = SO_TXREHASH, .flip = 1, }, + { .opt = SO_TIMESTAMPING_NEW, .new = SOF_TIMESTAMPING_RX_HARDWARE, + .expected = SOF_TIMESTAMPING_RX_HARDWARE, }, + { .opt = SO_TIMESTAMPING_OLD, .new = SOF_TIMESTAMPING_RX_HARDWARE, + .expected = SOF_TIMESTAMPING_RX_HARDWARE, }, { .opt = 0, }, };