Add TCP port connection timeout.

Use poll as a reasonably portable implementation. This takes advantage
of the existing FAKE_POLL implementation as well.

getsockopt(SO_ERROR) on Windows uses "int", removing the requirement for
any custom code for that platform.

We don't add any handling for EINTR, since it would add considerably
more code, and the connection can simply be retried. For that reason,
poll returning -1 is always an error.

asyn/drvAsynSerial/drvAsynIPPort.c

@@ -505,13 +505,56 @@ connectIt(void *drvPvt, asynUser *pasynUser)
             }
         }
 
+    }
+
+#ifdef USE_POLL
+    if (setNonBlock(fd, 1) < 0) {
+        epicsSnprintf(pasynUser->errorMessage,pasynUser->errorMessageSize,
+                               "Can't set %s O_NONBLOCK option: %s",
+                                       tty->IPDeviceName, strerror(SOCKERRNO));
+        epicsSocketDestroy(fd);
+        return asynError;
+    }
+#endif
+
+    if (pasynUser->reason <= 0) {
+
         /*
          * Connect to the remote host
          * If the connect fails, arrange for another DNS lookup in case the
          * problem is just that the device has DHCP'd itself an new number.
          */
         if (tty->socketType != SOCK_DGRAM) {
-            if (connect(fd, &tty->farAddr.oa.sa, (int)tty->farAddrSize) < 0) {
+            int connectResult = connect(fd, &tty->farAddr.oa.sa, (int)tty->farAddrSize);
+        #ifdef USE_POLL
+            if (connectResult < 0 && ((SOCKERRNO == EWOULDBLOCK) || (SOCKERRNO == EINPROGRESS))) {
+                double connectTimeout;
+                int msConnectTimeout;
+                struct pollfd pollfd;
+
+                pasynManager->getAutoConnectTimeout(&connectTimeout);
+                msConnectTimeout = 1000 * connectTimeout;
+                pollfd.fd = fd;
+                pollfd.events = POLLOUT;
+
+                /*
+                 * poll() returning 1 is the only case where connect might have been successful.
+                 * Otherwise connectResult will remain -1.
+                 */
+                if (poll(&pollfd, 1, msConnectTimeout) == 1) {
+                    int so_error;
+                    socklen_t len = sizeof so_error;
+
+                    /*
+                     * We must verify SO_ERROR to make sure the connection was successful.
+                     */
+                    getsockopt(fd, SOL_SOCKET, SO_ERROR, &so_error, &len);
+                    if (so_error == 0)
+                        connectResult = 0;
+                }
+            }
+        #endif
+            if (connectResult < 0) {
                 epicsSnprintf(pasynUser->errorMessage,pasynUser->errorMessageSize,
                               "Can't connect to %s: %s",
                               tty->IPDeviceName, strerror(SOCKERRNO));
@@ -532,15 +575,6 @@ connectIt(void *drvPvt, asynUser *pasynUser)
         epicsSocketDestroy(fd);
         return asynError;
     }
-#ifdef USE_POLL
-    if (setNonBlock(fd, 1) < 0) {
-        epicsSnprintf(pasynUser->errorMessage,pasynUser->errorMessageSize,
-                               "Can't set %s O_NONBLOCK option: %s",
-                                       tty->IPDeviceName, strerror(SOCKERRNO));
-        epicsSocketDestroy(fd);
-        return asynError;
-    }
-#endif
 
     asynPrint(pasynUser, ASYN_TRACE_FLOW,
                           "Opened connection OK to %s\n", tty->IPDeviceName);