Improve logging on failed connect attempt

common/trans.c

@@ -22,6 +22,8 @@
 #include <config_ac.h>
 #endif
 
+#include <errno.h>
+
 #include "os_calls.h"
 #include "string_calls.h"
 #include "trans.h"
@@ -750,6 +752,7 @@ trans_connect(struct trans *self, const char *server, const char *port,
     unsigned int start_time = g_get_elapsed_ms();
     int error;
     int ms_before_next_connect;
+    int connect_errno = 0;
 
     /*
      * Function pointers which we use in the main loop to avoid
@@ -792,6 +795,7 @@ trans_connect(struct trans *self, const char *server, const char *port,
 
         if (self->sck < 0)
         {
+            connect_errno = errno;
             error = 1;
             break;
         }
@@ -800,6 +804,7 @@ trans_connect(struct trans *self, const char *server, const char *port,
         g_file_set_cloexec(self->sck, 1);
         g_tcp_set_non_blocking(self->sck);
         error = f_connect(self->sck, server, port);
+        connect_errno = errno;
         if (error == 0)
         {
             /* Connect was immediately successful */
@@ -851,6 +856,8 @@ trans_connect(struct trans *self, const char *server, const char *port,
             g_tcp_close(self->sck);
             self->sck = -1;
         }
+        /* Ensure errno is representative of the last connection attempt */
+        errno = connect_errno;
         self->status = TRANS_STATUS_DOWN;
     }
     else

common/trans.h

@@ -158,6 +158,9 @@ trans_write_copy_s(struct trans *self, struct stream *out_s);
  *
  * Multiple connection attempts may be made within the timeout period.
  *
+ * If the operation is not successful, errno will have been set by
+ * the last connection attempt.
+ *
  * If the operation is successful, 0 is returned and self->status will
  * be TRANS_STATUS_UP
  */

vnc/vnc.c

@@ -1732,71 +1732,78 @@ lib_mod_connect(struct vnc *v)
 
     error = trans_connect(v->trans, v->ip, con_port, 3000);
 
+    if (error != 0)
+    {
+        g_snprintf(text, sizeof(text), "Error connecting to VNC server [%s]",
+                   g_get_strerror());
+        v->server_msg(v, text, 0);
+        free_stream(s);
+        free_stream(pixel_format);
+        return 1;
+    }
+
+    v->server_msg(v, "VNC tcp connected", 0);
+    /* protocol version */
+    init_stream(s, 8192);
+    error = trans_force_read_s(v->trans, s, 12);
     if (error == 0)
     {
-        v->server_msg(v, "VNC tcp connected", 0);
+        s->p = s->data;
-        /* protocol version */
+        out_uint8a(s, "RFB 003.003\n", 12);
-        init_stream(s, 8192);
+        s_mark_end(s);
-        error = trans_force_read_s(v->trans, s, 12);
+        error = trans_force_write_s(v->trans, s);
-        if (error == 0)
+    }
-        {
-            s->p = s->data;
-            out_uint8a(s, "RFB 003.003\n", 12);
-            s_mark_end(s);
-            error = trans_force_write_s(v->trans, s);
-        }
 
-        /* sec type */
+    /* sec type */
-        if (error == 0)
+    if (error == 0)
+    {
+        init_stream(s, 8192);
+        error = trans_force_read_s(v->trans, s, 4);
+    }
+
+    if (error == 0)
+    {
+        in_uint32_be(s, i);
+        g_sprintf(text, "VNC security level is %d (1 = none, 2 = standard)", i);
+        v->server_msg(v, text, 0);
+
+        if (i == 1) /* none */
+        {
+            check_sec_result = 0;
+        }
+        else if (i == 2) /* dec the password and the server random */
         {
             init_stream(s, 8192);
-            error = trans_force_read_s(v->trans, s, 4);
+            error = trans_force_read_s(v->trans, s, 16);
-        }
 
-        if (error == 0)
+            if (error == 0)
-        {
-            in_uint32_be(s, i);
-            g_sprintf(text, "VNC security level is %d (1 = none, 2 = standard)", i);
-            v->server_msg(v, text, 0);
-
-            if (i == 1) /* none */
-            {
-                check_sec_result = 0;
-            }
-            else if (i == 2) /* dec the password and the server random */
             {
                 init_stream(s, 8192);
-                error = trans_force_read_s(v->trans, s, 16);
+                if (guid_is_set(&v->guid))
-
-                if (error == 0)
                 {
-                    init_stream(s, 8192);
+                    char guid_str[GUID_STR_SIZE];
-                    if (guid_is_set(&v->guid))
+                    guid_to_str(&v->guid, guid_str);
-                    {
+                    rfbHashEncryptBytes(s->data, guid_str);
-                        char guid_str[GUID_STR_SIZE];
-                        guid_to_str(&v->guid, guid_str);
-                        rfbHashEncryptBytes(s->data, guid_str);
-                    }
-                    else
-                    {
-                        rfbEncryptBytes(s->data, v->password);
-                    }
-                    s->p += 16;
-                    s_mark_end(s);
-                    error = trans_force_write_s(v->trans, s);
-                    check_sec_result = 1; // not needed
                 }
+                else
+                {
+                    rfbEncryptBytes(s->data, v->password);
+                }
+                s->p += 16;
+                s_mark_end(s);
+                error = trans_force_write_s(v->trans, s);
+                check_sec_result = 1; // not needed
             }
-            else if (i == 0)
+        }
-            {
+        else if (i == 0)
-                LOG(LOG_LEVEL_ERROR, "VNC Server will disconnect");
+        {
-                error = 1;
+            LOG(LOG_LEVEL_ERROR, "VNC Server will disconnect");
-            }
+            error = 1;
-            else
+        }
-            {
+        else
-                LOG(LOG_LEVEL_ERROR, "VNC unsupported security level %d", i);
+        {
-                error = 1;
+            LOG(LOG_LEVEL_ERROR, "VNC unsupported security level %d", i);
-            }
+            error = 1;
         }
     }
 

xup/xup.c

@@ -324,7 +324,8 @@ lib_mod_connect(struct mod *mod)
     }
     else
     {
-        mod->server_msg(mod, "connection problem, giving up", 0);
+        LOG(LOG_LEVEL_ERROR, "Error connecting to X server [%s]",
+            g_get_strerror());
     }
 
     if (error == 0)