ext/socket/init.c (wait_connectable): bail out early on some errors

This becomes necesary if sockets become non-blocking by
default <https://bugs.ruby-lang.org/issues/14968>; but it's
always been possible to make sockets non-blocking anyways.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65619 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/init.c

@@ -508,11 +508,30 @@ wait_connectable(int fd)
     int sockerr, revents;
     socklen_t sockerrlen;
 
-    /* only to clear pending error */
     sockerrlen = (socklen_t)sizeof(sockerr);
     if (getsockopt(fd, SOL_SOCKET, SO_ERROR, (void *)&sockerr, &sockerrlen) < 0)
         return -1;
 
+    /* necessary for non-blocking sockets (at least ECONNREFUSED) */
+    switch (sockerr) {
+      case 0:
+        break;
+#ifdef EALREADY
+      case EALREADY:
+#endif
+#ifdef EISCONN
+      case EISCONN:
+#endif
+#ifdef ECONNREFUSED
+      case ECONNREFUSED:
+#endif
+#ifdef EHOSTUNREACH
+      case EHOSTUNREACH:
+#endif
+        errno = sockerr;
+        return -1;
+    }
+
     /*
      * Stevens book says, successful finish turn on RB_WAITFD_OUT and
      * failure finish turn on both RB_WAITFD_IN and RB_WAITFD_OUT.