On Sun, Jul 20, 2025 at 8:16 PM [off-list ref] wrote:

From: Fan Yu <fan.yu9@zte.com.cn>

Background
==========
When TCP retransmits a packet due to missing ACKs, the
retransmission may fail for various reasons (e.g., packets
stuck in driver queues, receiver zero windows, or routing issues).

The original tcp_retransmit_skb tracepoint:

  'commit e086101b150a ("tcp: add a tracepoint for tcp retransmission")'

lacks visibility into these failure causes, making production
diagnostics difficult.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Suggested-by: Eric Dumazet <edumazet@google.com>
Co-developed-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Fan Yu <fan.yu9@zte.com.cn>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Please do not add a Suggested-by tag when the original idea did not
come from someone else.

I only made suggestions to make your patch better.

Reviewed-by: Eric Dumazet <edumazet@google.com>