GUACAMOLE-2107: Fix the error handling within the guac_tcp_connect() function.

src/libguac/tcp.c

@@ -25,6 +25,7 @@
 #include <fcntl.h>
 #include <netdb.h>
 #include <netinet/in.h>
+#include <string.h>
 #include <sys/select.h>
 #include <sys/socket.h>
 #include <unistd.h>
@@ -50,7 +51,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
     if ((retval = getaddrinfo(hostname, port, &hints, &addresses))) {
         guac_error = GUAC_STATUS_INVALID_ARGUMENT;
         guac_error_message = "Error parsing address or port.";
-        return retval;
+        return -1;
     }
 
     /* Attempt connection to each address until success */
@@ -83,6 +84,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
             guac_error = GUAC_STATUS_INVALID_ARGUMENT;
             guac_error_message = "Failed to retrieve socket options.";
             close(fd);
+            fd = -1;
             continue;
         }
 
@@ -91,6 +93,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
             guac_error = GUAC_STATUS_INVALID_ARGUMENT;
             guac_error_message = "Failed to set non-blocking socket.";
             close(fd);
+            fd = -1;
             continue;
         }
 
@@ -108,12 +111,46 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
                 FD_SET(fd, &fdset);
 
                 retval = select(fd + 1, NULL, &fdset, NULL, &tv);
+
+                if (retval > 0) {
+                    int so_error = 0;
+                    socklen_t so_error_len = sizeof(so_error);
+                    retval = getsockopt(fd, SOL_SOCKET, SO_ERROR, &so_error, &so_error_len);
+
+                    /* Error occurs retrieving the socket status, so we set it
+                       and move on. */
+                    if (retval < 0) {
+                        guac_error = GUAC_STATUS_INVALID_ARGUMENT;
+                        guac_error_message = "Failed to retrieve socket status.";
+                        close(fd);
+                        fd = -1;
+                        continue;
+                    }
+
+                    /* This indicates that the connection is successful, so we
+                       break so that the socket can be immediately returned. */
+                    if (so_error == 0) {
+                        break;
+                    }
+
+                    /* There's a socket error, so we retrieve it and move to 
+                       the next address. */
+                    else {
+                        guac_error = GUAC_STATUS_REFUSED;
+                        guac_error_message = strerror(so_error);
+                        close(fd);
+                        fd = -1;
+                        continue;
+                    }
+                }
+
             }
 
             else {
                 guac_error = GUAC_STATUS_REFUSED;
                 guac_error_message = "Unable to connect via socket.";
                 close(fd);
+                fd = -1;
                 continue;
             }
         }
@@ -125,6 +162,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
                 guac_error = GUAC_STATUS_INVALID_ARGUMENT;
                 guac_error_message = "Failed to reset socket options.";
                 close(fd);
+                fd = -1;
                 continue;
             }
 
@@ -142,7 +180,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
 
         /* Some error has occurred - free resources before next iteration. */
         close(fd);
-
+        fd = -1;
     }
 
     /* Free addrinfo */
@@ -152,6 +190,7 @@ int guac_tcp_connect(const char* hostname, const char* port, const int timeout)
     if (current_address == NULL) {
         guac_error = GUAC_STATUS_REFUSED;
         guac_error_message = "Unable to connect to remote host.";
+        fd = -1;
     }
 
     /* Return the fd, or the error message if the socket connection failed. */