trace: tcp: Add tracepoint for tcp_sendmsg_locked()

Add a tracepoint to monitor TCP send operations, enabling detailed
visibility into TCP message transmission.

Create a new tracepoint within the tcp_sendmsg_locked function,
capturing traditional fields along with size_goal, which indicates the
optimal data size for a single TCP segment. Additionally, a reference to
the struct sock sk is passed, allowing direct access for BPF programs.
The implementation is largely based on David's patch[1] and suggestions.

Link: https://lore.kernel.org/all/70168c8f-bf52-4279-b4c4-be64527aa1ac@kernel.org/
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250408-tcpsendmsg-v3-2-208b87064c28@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index 1a40c41ff8c30a31b5c7002a4109de1cd8ef389e..75d3d53a3832c825c88199455489f07ff9af1404 100644 (file)
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -259,6 +259,30 @@ TRACE_EVENT(tcp_retransmit_synack,
                  __entry->saddr_v6, __entry->daddr_v6)
 );
 
+TRACE_EVENT(tcp_sendmsg_locked,
+       TP_PROTO(const struct sock *sk, const struct msghdr *msg,
+                const struct sk_buff *skb, int size_goal),
+
+       TP_ARGS(sk, msg, skb, size_goal),
+
+       TP_STRUCT__entry(
+               __field(const void *, skb_addr)
+               __field(int, skb_len)
+               __field(int, msg_left)
+               __field(int, size_goal)
+       ),
+
+       TP_fast_assign(
+               __entry->skb_addr = skb;
+               __entry->skb_len = skb ? skb->len : 0;
+               __entry->msg_left = msg_data_left(msg);
+               __entry->size_goal = size_goal;
+       ),
+
+       TP_printk("skb_addr %p skb_len %d msg_left %d size_goal %d",
+                 __entry->skb_addr, __entry->skb_len, __entry->msg_left,
+                 __entry->size_goal));
+
 DECLARE_TRACE(tcp_cwnd_reduction_tp,
        TP_PROTO(const struct sock *sk, int newly_acked_sacked,
                 int newly_lost, int flag),

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 16ba36f34dfab7531babf5753cab9f368cddefa3..24a26b4bb0b8ab229139b5552046e3ce3d6385c7 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6541,6 +6541,7 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = {
        { "xprt_put_cong", 0x10 },
        /* tcp */
        { "tcp_send_reset", 0x11 },
+       { "tcp_sendmsg_locked", 0x100 },
        /* tegra_apb_dma */
        { "tegra_dma_tx_status", 0x100 },
        /* timer_migration */

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 6edc441b37023de48281aa810aa7a36199fd8bc3..e0e96f8fd47cb57a4502ff3d316df9c1d9d12a3e 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1160,6 +1160,8 @@ restart:
                if (skb)
                        copy = size_goal - skb->len;
 
+               trace_tcp_sendmsg_locked(sk, msg, skb, size_goal);
+
                if (copy <= 0 || !tcp_skb_can_collapse_to(skb)) {
                        bool first_skb;