[PATCH net-next v4 5/7] tcp: rstreason: introduce SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT for active reset

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

Introducing this to show the users the reason of keepalive timeout.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
v3
Link: https://lore.kernel.org/all/20240731120955.23542-6-kerneljasonxing@gmail.com/
1. chose a better reason name (Eric)

v2
Link: https://lore.kernel.org/all/CAL+tcoB-12pUS0adK8M_=C97aXewYYmDA6rJKLXvAXEHvEsWjA@mail.gmail.com/
1. correct the comment and changelog
---
 include/net/rstreason.h | 7 +++++++
 net/ipv4/tcp_timer.c    | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index bbf20d0bbde7..9c0c46df0e73 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -21,6 +21,7 @@
 	FN(TCP_ABORT_ON_LINGER)		\
 	FN(TCP_ABORT_ON_MEMORY)		\
 	FN(TCP_STATE)			\
+	FN(TCP_KEEPALIVE_TIMEOUT)	\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -108,6 +109,12 @@ enum sk_rst_reason {
 	 * Please see RFC 9293 for all possible reset conditions
 	 */
 	SK_RST_REASON_TCP_STATE,
+	/**
+	 * @SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT: time to timeout
+	 * When we have already run out of all the chances, which means
+	 * keepalive timeout, we have to reset the connection
+	 */
+	SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 3910f6d8614e..86169127e4d1 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -807,7 +807,7 @@ static void tcp_keepalive_timer (struct timer_list *t)
 		    (user_timeout == 0 &&
 		    icsk->icsk_probes_out >= keepalive_probes(tp))) {
 			tcp_send_active_reset(sk, GFP_ATOMIC,
-					      SK_RST_REASON_NOT_SPECIFIED);
+					      SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT);
 			tcp_write_err(sk);
 			goto out;
 		}
-- 
2.37.3