socket-util: Avoid using SO_ERROR.

ESX doesn't implement it, and there's another approach that should work
everywhere, so drop back to that.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>

lib/socket-util.c

@@ -221,6 +221,7 @@ get_socket_error(int fd)
 int
 check_connection_completion(int fd)
 {
+    static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 10);
     struct pollfd pfd;
     int retval;
 
@@ -230,9 +231,17 @@ check_connection_completion(int fd)
         retval = poll(&pfd, 1, 0);
     } while (retval < 0 && errno == EINTR);
     if (retval == 1) {
-        return get_socket_error(fd);
+        if (pfd.revents & POLLERR) {
+            ssize_t n = send(fd, "", 1, MSG_DONTWAIT);
+            if (n < 0) {
+                return errno;
+            } else {
+                VLOG_ERR_RL(&rl, "poll return POLLERR but send succeeded");
+                return EPROTO;
+            }
+        }
+        return 0;
     } else if (retval < 0) {
-        static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 10);
         VLOG_ERR_RL(&rl, "poll: %s", strerror(errno));
         return errno;
     } else {

python/ovs/socket_util.py

@@ -78,8 +78,22 @@ def make_unix_socket(style, nonblock, bind_path, connect_path):
 def check_connection_completion(sock):
     p = ovs.poller.SelectPoll()
     p.register(sock, ovs.poller.POLLOUT)
-    if len(p.poll(0)) == 1:
-        return get_socket_error(sock)
+    pfds = p.poll(0)
+    if len(pfds) == 1:
+        revents = pfds[0][1]
+        if revents & ovs.poller.POLLERR:
+            try:
+                # The following should raise an exception.
+                socket.send("\0", socket.MSG_DONTWAIT)
+
+                # (Here's where we end up if it didn't.)
+                # XXX rate-limit
+                vlog.err("poll return POLLERR but send succeeded")
+                return errno.EPROTO
+            except socket.error, e:
+                return get_exception_errno(e)
+        else:
+            return 0
     else:
         return errno.EAGAIN