Centralize the code to set the active_dlt value for a device.

We were doing it similarly, but not the same, in several places; make a
common routine for it.

Have that code check to make sure the DLT_ value in question is actually
supported by the device; if not, pick the first supported DLT_ value, if
any; this keeps it from, for example, picking a bad DLT_ value if your
defaults were set based on monitor mode being on but monitor mode
actually being off, or vice versa.

Change-Id: I1722bfeaf60429bc5c6f665fdea3d466052b13bd
Reviewed-on: https://code.wireshark.org/review/7795
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 5 insertions, 18 deletions

diff --git a/ui/iface_lists.c b/ui/iface_lists.c
index 1310c30a3f..1dfb9b88c3 100644
--- a/ui/iface_lists.c
+++ b/ui/iface_lists.c
@@ -244,28 +244,10 @@ scan_local_interfaces(void (*update_cb)(void))
             device.monitor_mode_supported = caps->can_set_rfmon;
 #endif
             /*
-             * If there's a preference for the link-layer header type for
-             * this interface, use it.  If not, use the all-interface
-             * default; if that's not set on the command line, that will
-             * be -1, meaning "use per-interface defaults", otherwise
-             * we'll fail if it's not one of the types the interface
-             * supports.
-             */
-            if ((device.active_dlt = capture_dev_user_linktype_find(if_info->name)) == -1) {
-                device.active_dlt = global_capture_opts.default_options.linktype;
-            }
-
-            /*
              * Process the list of link-layer header types.
-             * If the active link-layer header type wasn't set from a
-             * preference or a global option (meaning it's -1), default
-             * to the first link-layer header type in the list.
              */
             for (lt_entry = caps->data_link_types; lt_entry != NULL; lt_entry = g_list_next(lt_entry)) {
                 data_link_info = (data_link_info_t *)lt_entry->data;
-                if (linktype_count == 0 && device.active_dlt == -1) {
-                    device.active_dlt = data_link_info->dlt;
-                }
                 link = (link_row *)g_malloc(sizeof(link_row));
                 if (data_link_info->description != NULL) {
                     link->dlt = data_link_info->dlt;
@@ -277,6 +259,11 @@ scan_local_interfaces(void (*update_cb)(void))
                 device.links = g_list_append(device.links, link);
                 linktype_count++;
             }
+
+            /*
+             * Set the active DLT for the device appropriately.
+             */
+            set_active_dlt(&device, global_capture_opts.default_options.linktype);
         } else {
 #if defined(HAVE_PCAP_CREATE)
             device.monitor_mode_enabled = FALSE;