if_capabilities: Use a structured error msg from dumpcap

Have dumpcap in child mode return an error message with a primary and
secondary string, instead of using stderr. When writing to the console
log we ignore the second message to prevent flooding the log with
tutorial-like info on permissions.

8 files changed, 48 insertions, 31 deletions

diff --git a/capchild/capture_ifinfo.c b/capchild/capture_ifinfo.c
index e8f049818a..a7dc7b7649 100644
--- a/capchild/capture_ifinfo.c
+++ b/capchild/capture_ifinfo.c
@@ -196,7 +196,8 @@ capture_interface_list(int *err, char **err_str, void (*update_cb)(void))
 if_capabilities_t *
 capture_get_if_capabilities(const gchar *ifname, gboolean monitor_mode,
                             const gchar *auth_string,
-                            char **err_str, void (*update_cb)(void))
+                            char **err_primary_msg, char **err_secondary_msg,
+                            void (*update_cb)(void))
 {
     if_capabilities_t *caps;
     GList              *linktype_list = NULL, *timestamp_list = NULL;
@@ -207,27 +208,28 @@ capture_get_if_capabilities(const gchar *ifname, gboolean monitor_mode,
     g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_MESSAGE, "Capture Interface Capabilities ...");
 
     /* see if the interface is from extcap */
-    caps = extcap_get_if_dlts(ifname, err_str);
+    caps = extcap_get_if_dlts(ifname, err_primary_msg);
     if (caps != NULL)
         return caps;
 
     /* return if the extcap interface generated an error */
-    if (err_str != NULL && *err_str != NULL)
+    if (err_primary_msg != NULL && *err_primary_msg != NULL)
         return NULL;
 
     /* Try to get our interface list */
     err = sync_if_capabilities_open(ifname, monitor_mode, auth_string, &data,
                                     &primary_msg, &secondary_msg, update_cb);
     if (err != 0) {
-        g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_MESSAGE, "Capture Interface Capabilities failed. Error %d, %s (%s)",
-              err, primary_msg ? primary_msg : "no message",
-              secondary_msg ? secondary_msg : "no secondary message");
-        if (err_str) {
-            *err_str = primary_msg;
-        } else {
+        g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_MESSAGE, "Capture Interface Capabilities failed. Error %d, %s",
+              err, primary_msg ? primary_msg : "no message");
+        if (err_primary_msg)
+            *err_primary_msg = primary_msg;
+        else
             g_free(primary_msg);
-        }
-        g_free(secondary_msg);
+        if (err_secondary_msg)
+            *err_secondary_msg = secondary_msg;
+        else
+            g_free(secondary_msg);
         return NULL;
     }
 
@@ -244,8 +246,8 @@ capture_get_if_capabilities(const gchar *ifname, gboolean monitor_mode,
      */
     if (raw_list[0] == NULL || *raw_list[0] == '\0') {
         g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_MESSAGE, "Capture Interface Capabilities returned no information.");
-        if (err_str) {
-            *err_str = g_strdup("Dumpcap returned no interface capability information");
+        if (err_primary_msg) {
+            *err_primary_msg = g_strdup("Dumpcap returned no interface capability information");
         }
         g_strfreev(raw_list);
         return NULL;
@@ -267,8 +269,8 @@ capture_get_if_capabilities(const gchar *ifname, gboolean monitor_mode,
 
     default:
         g_log(LOG_DOMAIN_CAPTURE, G_LOG_LEVEL_MESSAGE, "Capture Interface Capabilities returned bad information.");
-        if (err_str) {
-            *err_str = g_strdup_printf("Dumpcap returned \"%s\" for monitor-mode capability",
+        if (err_primary_msg) {
+            *err_primary_msg = g_strdup_printf("Dumpcap returned \"%s\" for monitor-mode capability",
                                        raw_list[0]);
         }
         g_free(caps);
@@ -323,8 +325,8 @@ capture_get_if_capabilities(const gchar *ifname, gboolean monitor_mode,
     /* Check to see if we built a list */
     if (linktype_list == NULL) {
         /* No. */
-        if (err_str)
-            *err_str = g_strdup("Dumpcap returned no link-layer types");
+        if (err_primary_msg)
+            *err_primary_msg = g_strdup("Dumpcap returned no link-layer types");
         g_free(caps);
         return NULL;
     }
diff --git a/caputils/capture_ifinfo.h b/caputils/capture_ifinfo.h
index 9965703538..5034ddb720 100644
--- a/caputils/capture_ifinfo.h
+++ b/caputils/capture_ifinfo.h
@@ -124,7 +124,8 @@ typedef struct {
 extern if_capabilities_t *
 capture_get_if_capabilities(const gchar *devname, gboolean monitor_mode,
                             const gchar *auth_string,
-                            char **err_str, void (*update_cb)(void));
+                            char **err_primary_msg, char **err_secondary_msg,
+                            void (*update_cb)(void));
 
 void free_if_capabilities(if_capabilities_t *caps);
 
diff --git a/dumpcap.c b/dumpcap.c
index 8a64a20510..19cf9f3818 100644
--- a/dumpcap.c
+++ b/dumpcap.c
@@ -5447,9 +5447,20 @@ main(int argc, char *argv[])
 
             caps = get_if_capabilities(interface_opts, &err, &err_str);
             if (caps == NULL) {
-                cmdarg_err("The capabilities of the capture device \"%s\" could not be obtained (%s).\n"
-                           "%s", interface_opts->name, err_str,
-                           get_pcap_failure_secondary_error_message(err, err_str));
+                if (capture_child) {
+                    char *error_msg = g_strdup_printf("The capabilities of the capture device"
+                                                " \"%s\" could not be obtained (%s)",
+                                                interface_opts->name, err_str);
+                    sync_pipe_errmsg_to_parent(2, error_msg,
+                            get_pcap_failure_secondary_error_message(err, err_str));
+                    g_free(error_msg);
+                }
+                else {
+                    cmdarg_err("The capabilities of the capture device"
+                                "\"%s\" could not be obtained (%s).\n%s",
+                                interface_opts->name, err_str,
+                                get_pcap_failure_secondary_error_message(err, err_str));
+                }
                 g_free(err_str);
                 exit_main(2);
             }
diff --git a/tshark.c b/tshark.c
index 15f30c21bf..a2e4360f31 100644
--- a/tshark.c
+++ b/tshark.c
@@ -727,7 +727,7 @@ main(int argc, char *argv[])
   int                  caps_queries = 0;
   gboolean             start_capture = FALSE;
   GList               *if_list;
-  gchar               *err_str;
+  gchar               *err_str, *err_str_secondary;
   struct bpf_program   fcode;
 #else
   gboolean             capture_option_specified = FALSE;
@@ -2200,11 +2200,13 @@ main(int argc, char *argv[])
               auth_str = g_strdup_printf("%s:%s", interface_opts->auth_username, interface_opts->auth_password);
           }
 #endif
-          caps = capture_get_if_capabilities(interface_opts->name, interface_opts->monitor_mode, auth_str, &err_str, NULL);
+          caps = capture_get_if_capabilities(interface_opts->name, interface_opts->monitor_mode,
+                                              auth_str, &err_str, &err_str_secondary, NULL);
           g_free(auth_str);
           if (caps == NULL) {
-            cmdarg_err("%s", err_str);
+            cmdarg_err("%s%s%s", err_str, err_str_secondary ? "\n" : "", err_str_secondary ? err_str_secondary : "");
             g_free(err_str);
+            g_free(err_str_secondary);
             exit_status = INVALID_CAPABILITY;
             goto clean_exit;
           }
diff --git a/ui/iface_lists.c b/ui/iface_lists.c
index 9ba39b9c5e..3294e53334 100644
--- a/ui/iface_lists.c
+++ b/ui/iface_lists.c
@@ -225,7 +225,7 @@ scan_local_interfaces(void (*update_cb)(void))
         }
         device.type = if_info->type;
         monitor_mode = prefs_capture_device_monitor_mode(if_info->name);
-        caps = capture_get_if_capabilities(if_info->name, monitor_mode, NULL, NULL, update_cb);
+        caps = capture_get_if_capabilities(if_info->name, monitor_mode, NULL, NULL, NULL, update_cb);
         for (; (curr_addr = g_slist_nth(if_info->addrs, ips)) != NULL; ips++) {
             temp_addr = g_new0(if_addr_t, 1);
             if (ips != 0) {
diff --git a/ui/qt/capture_options_dialog.cpp b/ui/qt/capture_options_dialog.cpp
index e4bd48fa94..f015888223 100644
--- a/ui/qt/capture_options_dialog.cpp
+++ b/ui/qt/capture_options_dialog.cpp
@@ -414,7 +414,7 @@ void CaptureOptionsDialog::interfaceItemChanged(QTreeWidgetItem *item, int colum
                                        device->remote_opts.remote_host_opts.auth_password);
         }
     #endif
-        caps = capture_get_if_capabilities(device->name, monitor_mode, auth_str, NULL, main_window_update);
+        caps = capture_get_if_capabilities(device->name, monitor_mode, auth_str, NULL, NULL, main_window_update);
         g_free(auth_str);
 
         if (caps != Q_NULLPTR) {
diff --git a/ui/qt/main.cpp b/ui/qt/main.cpp
index ddde2cbd4b..2e37116792 100644
--- a/ui/qt/main.cpp
+++ b/ui/qt/main.cpp
@@ -449,7 +449,7 @@ int main(int argc, char *qt_argv[])
     char                *rf_path;
     int                  rf_open_errno;
 #ifdef HAVE_LIBPCAP
-    gchar               *err_str;
+    gchar               *err_str, *err_str_secondary;;
 #else
 #ifdef _WIN32
 #ifdef HAVE_AIRPCAP
@@ -854,13 +854,14 @@ int main(int argc, char *qt_argv[])
             device = &g_array_index(global_capture_opts.all_ifaces, interface_t, i);
             if (device->selected) {
 #if defined(HAVE_PCAP_CREATE)
-                caps = capture_get_if_capabilities(device->name, device->monitor_mode_supported, NULL, &err_str, main_window_update);
+                caps = capture_get_if_capabilities(device->name, device->monitor_mode_supported, NULL, &err_str, &err_str_secondary, main_window_update);
 #else
-                caps = capture_get_if_capabilities(device->name, FALSE, NULL, &err_str,main_window_update);
+                caps = capture_get_if_capabilities(device->name, FALSE, NULL, &err_str, &err_str_secondary, main_window_update);
 #endif
                 if (caps == NULL) {
-                    cmdarg_err("%s", err_str);
+                    cmdarg_err("%s%s%s", err_str, err_str_secondary ? "\n" : "", err_str_secondary ? err_str_secondary : "");
                     g_free(err_str);
+                    g_free(err_str_secondary);
                     ret_val = INVALID_CAPABILITY;
                     goto clean_exit;
                 }
diff --git a/ui/qt/manage_interfaces_dialog.cpp b/ui/qt/manage_interfaces_dialog.cpp
index 99b541ca64..48ec905e4d 100644
--- a/ui/qt/manage_interfaces_dialog.cpp
+++ b/ui/qt/manage_interfaces_dialog.cpp
@@ -403,7 +403,7 @@ void ManageInterfacesDialog::updateRemoteInterfaceList(GList* rlist, remote_opti
             auth_str = g_strdup_printf("%s:%s", roptions->remote_host_opts.auth_username,
                                        roptions->remote_host_opts.auth_password);
         }
-        caps = capture_get_if_capabilities(if_string, monitor_mode, auth_str, NULL, main_window_update);
+        caps = capture_get_if_capabilities(if_string, monitor_mode, auth_str, NULL, NULL, main_window_update);
         g_free(auth_str);
         for (; (curr_addr = g_slist_nth(if_info->addrs, ips)) != NULL; ips++) {
             address addr_str;