Re: unix_stream_connect and socket address resolution

[John Ericson]

In case this is useful or interesting to anyone, I deep a some history
spelunking, and the restart logic in question seems to date back to
Import 2.2.4pre6:

https://github.com/tbodt/linux-history/commit/7d4fc34b9bbc0a14d3e5f6b2f978373422e1ca8a#diff-0553d076c243e06ae312480cb8cb52f1cebe1d80fc099d3842593e12c9e0d4f3

---
@@ -673,9 +703,25 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	   we will have to recheck all again in any case.
 	 */
 
+restart:
 	/*  Find listening sock */
 	other=unix_find_other(sunaddr, addr_len, sk->type, hash, &err);
 
+	if (!other)
+		return -ECONNREFUSED;
+
+	while (other->ack_backlog >= other->max_ack_backlog) {
+		unix_unlock(other);
+		if (other->dead || other->state != TCP_LISTEN)
+			return -ECONNREFUSED;
+		if (flags & O_NONBLOCK)
+			return -EAGAIN;
+		interruptible_sleep_on(&unix_ack_wqueue);
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+		goto restart;
+        }
+
 	/* create new sock for complete connection */
 	newsk = unix_create1(NULL, 1);
 
@@ -704,7 +750,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 
 	/* Check that listener is in valid state. */
 	err = -ECONNREFUSED;
-	if (other == NULL || other->dead || other->state != TCP_LISTEN)
+	if (other->dead || other->state != TCP_LISTEN)
 		goto out;
 
 	err = -ENOMEM;
---

My question can be basically restated: why should the `restart` label
not go *after* the `unix_find_other` call?

Cheers,

John