Bug#37267 - connect() EINPROGRESS failures mishandled in client library

We cann connect() in a non-blocking mode to be able to specify a
non-standard timeout.

The problem was that we did not fetch the status from the
non-blocking connect(). We assumed that poll() would not return
a POLLIN flag if the connect failed. But on some platforms this
is not true.

After a successful poll() we do now retrieve the status value
from connect() with getsockopt(...SO_ERROR...). Now we do know
if (and how) the connect failed.

The test case for my investigation was rpl.rlp_ssl1 on an
Ubuntu 9.04 x86_64 machine. Both, IPV4 and IPV6 were active.
'localhost' resolved first for IPV6 and then for IPV4. The
connection over IPV6 was blocked. rpl.rlp_ssl1 timed out
as it did not notice the failed connect(). The first read()
failed, which was interpreted as a master crash and the
connection was tried to reestablish with the same result
until the retry limit was reached.

With the fix, the connect() problem is immediately recognized,
and the connect() is retried on the second resolution for
'localhost', which is successful.

libmysqld/libmysqld.c

@@ -99,7 +99,7 @@ mysql_real_connect(MYSQL *mysql,const char *host, const char *user,
   char name_buff[USERNAME_LENGTH];
 
   DBUG_ENTER("mysql_real_connect");
-  DBUG_PRINT("enter",("host: %s  db: %s  user: %s",
+  DBUG_PRINT("enter",("host: %s  db: %s  user: %s (libmysqld)",
 		      host ? host : "(Null)",
 		      db ? db : "(Null)",
 		      user ? user : "(Null)"));