[PATCH net-next v4 6/7] tcp: rstreason: introduce SK_RST_REASON_TCP_DISCONNECT_WITH_DATA for active reset

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

When user tries to disconnect a socket and there are more data written
into tcp write queue, we should tell users about this reset reason.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
--
v3
Link: Link: https://lore.kernel.org/all/20240731120955.23542-5-kerneljasonxing@gmail.com/
1. This case is different from previous patch, so we need to write
it into a new patch. (Eric)
---
 include/net/rstreason.h | 8 ++++++++
 net/ipv4/tcp.c          | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index 9c0c46df0e73..69cb2e52b7da 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -22,6 +22,7 @@
 	FN(TCP_ABORT_ON_MEMORY)		\
 	FN(TCP_STATE)			\
 	FN(TCP_KEEPALIVE_TIMEOUT)	\
+	FN(TCP_DISCONNECT_WITH_DATA)	\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -115,6 +116,13 @@ enum sk_rst_reason {
 	 * keepalive timeout, we have to reset the connection
 	 */
 	SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT,
+	/**
+	 * @SK_RST_REASON_TCP_DISCONNECT_WITH_DATA: disconnect when write
+	 * queue is not empty
+	 * It means user has written data into the write queue when doing
+	 * disconnecting, so we have to send an RST.
+	 */
+	SK_RST_REASON_TCP_DISCONNECT_WITH_DATA,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 24777e48bcc8..8514257f4ecd 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3033,7 +3033,8 @@ int tcp_disconnect(struct sock *sk, int flags)
 		/* The last check adjusts for discrepancy of Linux wrt. RFC
 		 * states
 		 */
-		tcp_send_active_reset(sk, gfp_any(), SK_RST_REASON_NOT_SPECIFIED);
+		tcp_send_active_reset(sk, gfp_any(),
+				      SK_RST_REASON_TCP_DISCONNECT_WITH_DATA);
 		WRITE_ONCE(sk->sk_err, ECONNRESET);
 	} else if (old_state == TCP_SYN_SENT)
 		WRITE_ONCE(sk->sk_err, ECONNRESET);
-- 
2.37.3