Scenario:
1. A client socket initiates a SYN message to a listening socket.
2. The send link is congested, the SYN message is put in the
send link and a wakeup message is put in wakeup queue.
3. The congestion situation is abated, the wakeup message is
pulled out of the wakeup queue. Function tipc_sk_push_backlog()
is called to send out delayed messages by Nagle. However,
the client socket is still in CONNECTING state. So, it sends
the SYN message in the socket write queue to the listening socket
again.
4. The listening socket receives the first SYN message and creates
first server socket. The client socket receives ACK- and establishes
a connection to the first server socket. The client socket closes
its connection with the first server socket.
5. The listening socket receives the second SYN message and creates
second server socket. The second server socket sends ACK- to the
client socket, but it has been closed. It results in connection
refuse error when reading from the server socket in user space.
Solution: return from function tipc_sk_push_backlog() immediately
if the client socket state is not ESTABLISHED.
Fixes: c0bceb97db9e ("tipc: add smart nagle feature")
Signed-off-by: Tung Nguyen <[email protected]>
---
net/tipc/socket.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 5d7859a..61f9da4 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1246,13 +1246,18 @@ void tipc_sk_mcast_rcv(struct net *net, struct
sk_buff_head *arrvq,
static void tipc_sk_push_backlog(struct tipc_sock *tsk)
{
struct sk_buff_head *txq = &tsk->sk.sk_write_queue;
- struct net *net = sock_net(&tsk->sk);
+ struct sock *sk = &tsk->sk;
+ struct net *net = sock_net(sk);
u32 dnode = tsk_peer_node(tsk);
int rc;
if (skb_queue_empty(txq) || tsk->cong_link_cnt)
return;
+ /* Do not send SYN again after congestion */
+ if (sk->sk_state != TIPC_ESTABLISHED)
+ return;
+
tsk->snt_unacked += tsk->snd_backlog;
tsk->snd_backlog = 0;
tsk->expect_ack = true;
--
2.1.4
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