If capture_get_if_capabilities() fails, pop up a message, just as we

print a message in tshark.  That doesn't fix the problem seen on Linux
distributions, such as recent versions of Debian and derivatives, that
have libpcap 1.1.0 or later built without libnl, where the monitor mode
checkbox doesn't work - that's a libpcap bug, fixed in the 1.2 branch
and trunk, so a future 1.2.1 or 1.3.0 release should fix it, and perhaps
a future Debian release will build libpcap with libnl - but at least it
means you get a dialog box rather than just getting mysterious behavior
when you try to check the "monitor mode" checkbox.

svn path=/trunk/; revision=40098

1 files changed, 140 insertions, 5 deletions

diff --git a/gtk/capture_dlg.c b/gtk/capture_dlg.c
index 4385b03cf4..df81cdb0b9 100644
--- a/gtk/capture_dlg.c
+++ b/gtk/capture_dlg.c
@@ -808,6 +808,7 @@ insert_new_rows(GList *list)
   if_capabilities_t *caps;
   gint linktype_count;
   cap_settings_t cap_settings;
+  gchar *err_str, *err_str_norfmon;
   GSList *curr_addr;
   int ips = 0;
   guint i, count=0;
@@ -843,7 +844,7 @@ insert_new_rows(GList *list)
       continue;
     }
     ip_str = g_string_new("");
-	ips = 0;
+    ips = 0;
     row.name = g_strdup(if_info->name);
     /* Is this interface hidden and, if so, should we include it
        anyway? */
@@ -896,7 +897,50 @@ insert_new_rows(GList *list)
       row.cfilter = g_strdup(global_capture_opts.default_options.cfilter);
     }
     cap_settings = capture_get_cap_settings(if_string);
-    caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode, NULL);
+    caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode,
+                                       &err_str);
+    if (caps == NULL) {
+      /* Error attempting to get interface capabilities. */
+      if (cap_settings.monitor_mode) {
+        /*
+         * Perhaps this is the libpcap bug on Linux where
+         * attempting to set monitor mode with the Wireless
+         * Extensions ioctls doesn't work correctly.
+         *
+         * Try fetching the capabilities without monitor mode;
+         * if that succeeds, report the monitor-mode problem,
+         * and use the no-monitor-mode capabilities.  If that
+         * fails, report that failure.  In either case, force
+         * monitor mode off.
+         */
+        cap_settings.monitor_mode = FALSE;
+        caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode,
+                                           &err_str_norfmon);
+        if (caps == NULL) {
+          /* Epic fail. */
+          simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str_norfmon);
+          g_free(err_str_norfmon);
+          g_free(err_str);
+        } else {
+          /*
+           * OK, it's probably that bug.  Suggest using airmon-ng,
+           * just in case the adapter has a mac80211 driver and
+           * libpcap was built without libnl so that it can't
+           * use the mac80211 features to create a monitor-mode
+           * device.
+           */
+          simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK,
+                        "%s\n\n"
+                        "Try using airmon-ng, as suggested by CaptureSetup/WLAN in the Wireshark Wiki.",
+                        err_str);
+          g_free(err_str);
+        }
+      } else {
+        simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str);
+        g_free(err_str);
+      }
+    }
+
     gtk_list_store_append (GTK_LIST_STORE(model), &iter);
     for (; (curr_addr = g_slist_nth(if_info->addrs, ips)) != NULL; ips++) {
       if (ips != 0) {
@@ -3673,7 +3717,7 @@ make_and_fill_rows(void)
   GList *lt_entry;
   link_row *link = NULL;
   data_link_info_t *data_link_info;
-  gchar *str, *err_str = NULL;
+  gchar *str, *err_str = NULL, *err_str_norfmon;
   interface_row row;
   interface_options interface_opts;
   gboolean found = FALSE;
@@ -3749,7 +3793,50 @@ make_and_fill_rows(void)
         row.cfilter = g_strdup(global_capture_opts.default_options.cfilter);
       }
       cap_settings = capture_get_cap_settings(if_info->name);
-      caps = capture_get_if_capabilities(if_info->name, cap_settings.monitor_mode, NULL);
+      caps = capture_get_if_capabilities(if_info->name,
+                                         cap_settings.monitor_mode,
+                                         &err_str);
+      if (caps == NULL) {
+        /* Error attempting to get interface capabilities. */
+        if (cap_settings.monitor_mode) {
+          /*
+           * Perhaps this is the libpcap bug on Linux where
+           * attempting to set monitor mode with the Wireless
+           * Extensions ioctls doesn't work correctly.
+           *
+           * Try fetching the capabilities without monitor mode;
+           * if that succeeds, report the monitor-mode problem,
+           * and use the no-monitor-mode capabilities.  If that
+           * fails, report that failure.  In either case, force
+           * monitor mode off.
+           */
+          cap_settings.monitor_mode = FALSE;
+          caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode,
+                                             &err_str_norfmon);
+          if (caps == NULL) {
+            /* Epic fail. */
+            simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str_norfmon);
+            g_free(err_str_norfmon);
+            g_free(err_str);
+          } else {
+            /*
+             * OK, it's probably that bug.  Suggest using airmon-ng,
+             * just in case the adapter has a mac80211 driver and
+             * libpcap was built without libnl so that it can't
+             * use the mac80211 features to create a monitor-mode
+             * device.
+             */
+            simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK,
+                          "%s\n\n"
+                          "Try using airmon-ng, as suggested by CaptureSetup/WLAN in the Wireshark Wiki.",
+                          err_str);
+            g_free(err_str);
+          }
+        } else {
+          simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str);
+          g_free(err_str);
+        }
+      }
       for (; (curr_addr = g_slist_nth(if_info->addrs, ips)) != NULL; ips++) {
         if (ips != 0) {
           g_string_append(ip_str, "\n");
@@ -4019,6 +4106,7 @@ capture_prep_monitor_changed_cb(GtkWidget *monitor, gpointer argp _U_)
   GList *lt_entry;
   gchar *if_string=NULL;
   cap_settings_t cap_settings;
+  gchar *err_str, *err_str_norfmon;
   if_capabilities_t *caps=NULL;
   gint linktype_count = 0, i;
   data_link_info_t *data_link_info;
@@ -4034,7 +4122,49 @@ capture_prep_monitor_changed_cb(GtkWidget *monitor, gpointer argp _U_)
   if_string = g_strdup(row.name);
   cap_settings = capture_get_cap_settings(if_string);
   cap_settings.monitor_mode = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(monitor));
-  caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode, NULL);
+  caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode,
+                                     &err_str);
+  if (caps == NULL) {
+    /* Error attempting to get interface capabilities. */
+    if (cap_settings.monitor_mode) {
+      /*
+       * Perhaps this is the libpcap bug on Linux where
+       * attempting to set monitor mode with the Wireless
+       * Extensions ioctls doesn't work correctly.
+       *
+       * Try fetching the capabilities without monitor mode;
+       * if that succeeds, report the monitor-mode problem,
+       * and use the no-monitor-mode capabilities.  If that
+       * fails, report that failure.  In either case, force
+       * monitor mode off.
+       */
+      cap_settings.monitor_mode = FALSE;
+      caps = capture_get_if_capabilities(if_string, cap_settings.monitor_mode,
+                                         &err_str_norfmon);
+      if (caps == NULL) {
+        /* Epic fail. */
+        simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str_norfmon);
+        g_free(err_str_norfmon);
+        g_free(err_str);
+      } else {
+        /*
+         * OK, it's probably that bug.  Suggest using airmon-ng,
+         * just in case the adapter has a mac80211 driver and
+         * libpcap was built without libnl so that it can't
+         * use the mac80211 features to create a monitor-mode
+         * device.
+         */
+        simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK,
+                      "%s\n\n"
+                      "Try using airmon-ng, as suggested by CaptureSetup/WLAN in the Wireshark Wiki.",
+                      err_str);
+        g_free(err_str);
+      }
+    } else {
+      simple_dialog(ESD_TYPE_ERROR, ESD_BTN_OK, "%s", err_str);
+      g_free(err_str);
+    }
+  }
 
   if (caps != NULL) {
     g_signal_handlers_disconnect_by_func(linktype_combo_box, G_CALLBACK(select_link_type_cb), NULL );
@@ -4086,6 +4216,11 @@ capture_prep_monitor_changed_cb(GtkWidget *monitor, gpointer argp _U_)
   }
   gtk_widget_set_sensitive(linktype_lb, linktype_count >= 2);
   gtk_widget_set_sensitive(linktype_combo_box, linktype_count >= 2);
+#ifdef HAVE_PCAP_CREATE
+  /* Set the monitor-mode checkbox to the appropriate value */
+  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(monitor),
+                               cap_settings.monitor_mode);
+#endif
   ws_combo_box_set_active(GTK_COMBO_BOX(linktype_combo_box),0);
   g_array_insert_val(rows, marked_row, row);
 }