[RFC net-next 1/2] tipc: abort pending connects when the peer node is lost

[liushike <liushike123@gmail.com>]

From: liushike <liushike@ruijie.com.cn>

A client can send a SYN and block in connect() while the listening server
has not yet called accept(). If the last usable link to that server is
lost, the client may remain asleep until its connection timeout expires.
Only established connections are in the peer node's conn_sks list, so
node_lost_contact() cannot notify the pending connection.

Register an active open before sending SYN and check node availability
under the node write lock. Let the existing node-loss notification abort
the pending handshake with EHOSTUNREACH and wake the connect waiter.
Losing one link does not abort the connect while another link survives.

Update the listening port to the accepted port in place on receipt of
ACK, preserving the node-loss registration. Reject a late ACK if node
loss already removed the registration, even if the node has recovered.
Transfer the registration when a named SYN is rerouted to another node.
Avoid registering active opens twice; remove registrations on transmit
failure and terminal rejection, but retain them across overload retries
and connection-wait timeouts, which do not cancel the handshake.

Signed-off-by: liushike <liushike@ruijie.com.cn>
---
 net/tipc/node.c   | 37 ++++++++++++++++++++++++++++++++++++-
 net/tipc/node.h   |  1 +
 net/tipc/socket.c | 38 +++++++++++++++++++++++++++++++++++---
 3 files changed, 72 insertions(+), 4 deletions(-)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index bd91378b7540..31f2ef44ad37 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -713,13 +713,48 @@ int tipc_node_add_conn(struct net *net, u32 dnode, u32 port, u32 peer_port)
 	conn->peer_port = peer_port;
 
 	tipc_node_write_lock(node);
-	list_add_tail(&conn->list, &node->conn_sks);
+	if (node_is_up(node)) {
+		list_add_tail(&conn->list, &node->conn_sks);
+	} else {
+		err = -EHOSTUNREACH;
+		kfree(conn);
+	}
 	tipc_node_write_unlock(node);
 exit:
 	tipc_node_put(node);
 	return err;
 }
 
+/* Replace the listening port with the accepted port without losing the
+ * node loss subscription. A missing entry means node_lost_contact() has
+ * already aborted this connection attempt, even if the node is up again.
+ */
+int tipc_node_update_conn(struct net *net, u32 dnode, u32 port, u32 peer_port)
+{
+	struct tipc_sock_conn *conn;
+	struct tipc_node *node;
+	int err = -EHOSTUNREACH;
+
+	if (in_own_node(net, dnode))
+		return 0;
+
+	node = tipc_node_find(net, dnode);
+	if (!node)
+		return err;
+
+	tipc_node_write_lock(node);
+	list_for_each_entry(conn, &node->conn_sks, list) {
+		if (conn->port != port)
+			continue;
+		conn->peer_port = peer_port;
+		err = 0;
+		break;
+	}
+	tipc_node_write_unlock(node);
+	tipc_node_put(node);
+	return err;
+}
+
 void tipc_node_remove_conn(struct net *net, u32 dnode, u32 port)
 {
 	struct tipc_node *node;
diff --git a/net/tipc/node.h b/net/tipc/node.h
index 154a5bbb0d29..48693a050aa8 100644
--- a/net/tipc/node.h
+++ b/net/tipc/node.h
@@ -107,6 +107,7 @@ void tipc_node_subscribe(struct net *net, struct list_head *subscr, u32 addr);
 void tipc_node_unsubscribe(struct net *net, struct list_head *subscr, u32 addr);
 void tipc_node_broadcast(struct net *net, struct sk_buff *skb, int rc_dests);
 int tipc_node_add_conn(struct net *net, u32 dnode, u32 port, u32 peer_port);
+int tipc_node_update_conn(struct net *net, u32 dnode, u32 port, u32 peer_port);
 void tipc_node_remove_conn(struct net *net, u32 dnode, u32 port);
 int tipc_node_get_mtu(struct net *net, u32 addr, u32 sel, bool connected);
 bool tipc_node_is_up(struct net *net, u32 addr);
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index d5d70eb230b5..191579636351 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1511,6 +1511,16 @@ static int __tipc_sendmsg(struct socket *sock, struct msghdr *m, size_t dlen)
 		return -ENOMEM;
 	}
 
+	/* Subscribe before sending SYN so node loss also aborts pending connects. */
+	if (syn) {
+		rc = tipc_node_add_conn(net, skaddr.node, tsk->portid, skaddr.ref);
+		if (rc) {
+			__skb_queue_purge(&pkts);
+			__skb_queue_purge(&sk->sk_write_queue);
+			return rc;
+		}
+	}
+
 	/* Send message */
 	trace_tipc_sk_sendmsg(sk, skb_peek(&pkts), TIPC_DUMP_SK_SNDQ, " ");
 	rc = tipc_node_xmit(net, &pkts, skaddr.node, tsk->portid);
@@ -1520,6 +1530,11 @@ static int __tipc_sendmsg(struct socket *sock, struct msghdr *m, size_t dlen)
 		rc = 0;
 	}
 
+	if (unlikely(syn && rc)) {
+		tipc_node_remove_conn(net, skaddr.node, tsk->portid);
+		__skb_queue_purge(&sk->sk_write_queue);
+	}
+
 	if (unlikely(syn && !rc)) {
 		tipc_set_sk_state(sk, TIPC_CONNECTING);
 		if (dlen && timeout) {
@@ -1674,8 +1689,10 @@ static void tipc_sk_finish_conn(struct tipc_sock *tsk, u32 peer_port,
 	msg_set_hdr_sz(msg, SHORT_H_SIZE);
 
 	sk_reset_timer(sk, &sk->sk_timer, jiffies + CONN_PROBING_INTV);
+	/* Active opens already subscribed before sending SYN. */
+	if (sk->sk_state != TIPC_CONNECTING)
+		tipc_node_add_conn(net, peer_node, tsk->portid, peer_port);
 	tipc_set_sk_state(sk, TIPC_ESTABLISHED);
-	tipc_node_add_conn(net, peer_node, tsk->portid, peer_port);
 	tsk->max_pkt = tipc_node_get_mtu(net, peer_node, tsk->portid, true);
 	tsk->peer_caps = tipc_node_get_capabilities(net, peer_node);
 	tsk_set_nagle(tsk);
@@ -2199,12 +2216,14 @@ static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb,
 	struct net *net = sock_net(sk);
 	struct tipc_msg *hdr = buf_msg(skb);
 	bool con_msg = msg_connected(hdr);
+	bool reject_ack = false;
 	u32 pport = tsk_peer_port(tsk);
 	u32 pnode = tsk_peer_node(tsk);
 	u32 oport = msg_origport(hdr);
 	u32 onode = msg_orignode(hdr);
 	int err = msg_errcode(hdr);
 	unsigned long delay;
+	int rc;
 
 	if (unlikely(msg_mcast(hdr)))
 		return false;
@@ -2216,6 +2235,18 @@ static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb,
 		if (likely(con_msg)) {
 			if (err)
 				break;
+			rc = tipc_node_update_conn(net, pnode, tsk->portid, oport);
+			/* A named SYN may have been rerouted to another node. */
+			if (!rc && onode != pnode) {
+				tipc_node_remove_conn(net, pnode, tsk->portid);
+				rc = tipc_node_add_conn(net, onode, tsk->portid, oport);
+			}
+			if (rc) {
+				err = TIPC_ERR_NO_NODE;
+				/* Return a late ACK to its sender, including any data. */
+				reject_ack = true;
+				break;
+			}
 			tipc_sk_finish_conn(tsk, oport, onode);
 			msg_set_importance(&tsk->phdr, msg_importance(hdr));
 			/* ACK+ message with data is added to receive queue */
@@ -2285,9 +2316,10 @@ static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb,
 	}
 	/* Abort connection setup attempt */
 	tipc_set_sk_state(sk, TIPC_DISCONNECTING);
-	sk->sk_err = ECONNREFUSED;
+	tipc_node_remove_conn(net, pnode, tsk->portid);
+	sk->sk_err = err == TIPC_ERR_NO_NODE ? EHOSTUNREACH : ECONNREFUSED;
 	sk->sk_state_change(sk);
-	return true;
+	return !reject_ack;
 }
 
 /**
-- 
2.34.1