[PATCH] ksmbd: enable TCP keepalive for accepted connections

[Namjae Jeon <linkinjeon@kernel.org>]

A client that disappears without sending a FIN or RST can leave its
ksmbd connection in ESTABLISHED indefinitely. ksmbd sets a socket
receive timeout, but the connection receive loop retries timeout errors
without a limit, so the connection remains in conn_list and consumes the
per-IP connection quota.

Enable SO_KEEPALIVE on accepted TCP sockets so the TCP stack can detect a
silent peer failure. The keepalive idle time, interval, and probe count
remain controlled by the existing TCP sysctl settings.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/smb/server/transport_tcp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c
index 0ae5f145a332..921e4e86d01c 100644
--- a/fs/smb/server/transport_tcp.c
+++ b/fs/smb/server/transport_tcp.c
@@ -292,6 +292,12 @@ static int ksmbd_kthread_fn(void *p)
 		ksmbd_debug(CONN, "connect success: accepted new connection\n");
 		client_sk->sk->sk_rcvtimeo = KSMBD_TCP_RECV_TIMEOUT;
 		client_sk->sk->sk_sndtimeo = KSMBD_TCP_SEND_TIMEOUT;
+		/*
+		 * Detect peers that disappear without sending a FIN or RST.
+		 * Otherwise the connection handler can retry receive timeouts
+		 * indefinitely and keep the connection in conn_list.
+		 */
+		sock_set_keepalive(client_sk->sk);
 
 		ksmbd_tcp_new_connection(client_sk);
 	}
-- 
2.25.1