netdev - [PATCH net v1] tipc: fix hanging clients using poll with EPOLLOUT flag

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Date:   Thu,  9 May 2019 07:13:42 +0200
From:   Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...il.com>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     jon.maloy@...csson.com, ying.xue@...driver.com,
        tipc-discussion@...ts.sourceforge.net,
        Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...il.com>,
        Jon Maloy <jon.maloy@...csson.se>
Subject: [PATCH net v1] tipc: fix hanging clients using poll with EPOLLOUT flag

commit 517d7c79bdb398 ("tipc: fix hanging poll() for stream sockets")
introduced a regression for clients using non-blocking sockets.
After the commit, we send EPOLLOUT event to the client even in
TIPC_CONNECTING state. This causes the subsequent send() to fail
with ENOTCONN, as the socket is still not in TIPC_ESTABLISHED state.

In this commit, we:
- improve the fix for hanging poll() by replacing sk_data_ready()
  with sk_state_change() to wake up all clients.
- revert the faulty updates introduced by commit 517d7c79bdb398
  ("tipc: fix hanging poll() for stream sockets").

Fixes: 517d7c79bdb398 ("tipc: fix hanging poll() for stream sockets")
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...il.com>
Acked-by: Jon Maloy <jon.maloy@...csson.se>
---
 net/tipc/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index b542f14ed444..2851937f6e32 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -734,11 +734,11 @@ static __poll_t tipc_poll(struct file *file, struct socket *sock,
 
 	switch (sk->sk_state) {
 	case TIPC_ESTABLISHED:
-	case TIPC_CONNECTING:
 		if (!tsk->cong_link_cnt && !tsk_conn_cong(tsk))
 			revents |= EPOLLOUT;
 		/* fall through */
 	case TIPC_LISTEN:
+	case TIPC_CONNECTING:
 		if (!skb_queue_empty(&sk->sk_receive_queue))
 			revents |= EPOLLIN | EPOLLRDNORM;
 		break;
@@ -2041,7 +2041,7 @@ static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb)
 			if (msg_data_sz(hdr))
 				return true;
 			/* Empty ACK-, - wake up sleeping connect() and drop */
-			sk->sk_data_ready(sk);
+			sk->sk_state_change(sk);
 			msg_set_dest_droppable(hdr, 1);
 			return false;
 		}
-- 
2.21.0