Add 3 tracepoints, namely tcp_data_send/tcp_data_recv/tcp_data_acked, which will be called every time a tcp data packet is sent, received, and acked. tcp_data_send: called after a data packet is sent. tcp_data_recv: called after a data packet is receviced. tcp_data_acked: called after a valid ack packet is processed (some sent data are ackknowledged).
We use these callbacks for fine-grained tcp monitoring, which collects and analyses every tcp request/response event information. The whole system has been described in SIGMOD'18 (see https://dl.acm.org/doi/pdf/10.1145/3183713.3190659 for details). To achieve this with bpf, we require hooks for data events that call bpf prog (1) when any data packet is sent/received/acked, and (2) after critical tcp state variables have been updated (e.g., snd_una, snd_nxt, rcv_nxt). However, existing bpf hooks cannot meet our requirements. Besides, these tracepoints help to debug tcp when data send/recv/acked. Though kretprobe/fexit can also be used to collect these information, they will not work if the kernel functions get inlined. Considering the stability, we prefer tracepoint as the solution. Signed-off-by: Philo Lu <[email protected]> Signed-off-by: Xuan Zhuo <[email protected]> --- include/trace/events/tcp.h | 21 +++++++++++++++++++++ net/ipv4/tcp_input.c | 4 ++++ net/ipv4/tcp_output.c | 2 ++ 3 files changed, 27 insertions(+) diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index 7b1ddffa3dfc..1423f7cb73f9 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h @@ -113,6 +113,13 @@ DEFINE_EVENT(tcp_event_sk_skb, tcp_send_reset, TP_ARGS(sk, skb) ); +DEFINE_EVENT(tcp_event_sk_skb, tcp_data_recv, + + TP_PROTO(const struct sock *sk, const struct sk_buff *skb), + + TP_ARGS(sk, skb) +); + /* * tcp event with arguments sk * @@ -187,6 +194,20 @@ DEFINE_EVENT(tcp_event_sk, tcp_rcv_space_adjust, TP_ARGS(sk) ); +DEFINE_EVENT(tcp_event_sk, tcp_data_send, + + TP_PROTO(struct sock *sk), + + TP_ARGS(sk) +); + +DEFINE_EVENT(tcp_event_sk, tcp_data_acked, + + TP_PROTO(struct sock *sk), + + TP_ARGS(sk) +); + TRACE_EVENT(tcp_retransmit_synack, TP_PROTO(const struct sock *sk, const struct request_sock *req), diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index bcb55d98004c..edb1e24a3423 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -824,6 +824,8 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) now = tcp_jiffies32; + trace_tcp_data_recv(sk, skb); + if (!icsk->icsk_ack.ato) { /* The _first_ data packet received, initialize * delayed ACK engine. @@ -3486,6 +3488,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb, } } #endif + + trace_tcp_data_acked(sk); return flag; } diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index eb13a55d660c..cb6f2af55ce2 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2821,6 +2821,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, /* Send one loss probe per tail loss episode. */ if (push_one != 2) tcp_schedule_loss_probe(sk, false); + + trace_tcp_data_send(sk); return false; } return !tp->packets_out && !tcp_write_queue_empty(sk); -- 2.32.0.3.g01195cf9f
