Put the interface descrptions into the IDB when capturing to pcapng.

capture_opts_add_iface_opt(), when called in a program acting as a
capture child, will fetch the description for the interface, and will
also generate a "display name" for the interface.

In the process, we clean up capture_opts_add_iface_opt() a bit,
combining duplicate code.

We rename console_display_name to just display_name, as it may also be
used in the title bar of Wireshark when capturing.

Change-Id: Ifd18955bb3cb41df4c0ed4362d4854068c825b96
Reviewed-on: https://code.wireshark.org/review/29117
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>

6 files changed, 387 insertions, 145 deletions

diff --git a/capture_opts.c b/capture_opts.c
index 8b249d6175..47f6dab00e 100644
--- a/capture_opts.c
+++ b/capture_opts.c
@@ -155,7 +155,7 @@ capture_opts_log(const char *log_domain, GLogLevelFlags log_level, capture_optio
         interface_opts = &g_array_index(capture_opts->ifaces, interface_options, i);
         g_log(log_domain, log_level, "Interface name[%02d]  : %s", i, interface_opts->name ? interface_opts->name : "(unspecified)");
         g_log(log_domain, log_level, "Interface description[%02d] : %s", i, interface_opts->descr ? interface_opts->descr : "(unspecified)");
-        g_log(log_domain, log_level, "Console display name[%02d]: %s", i, interface_opts->console_display_name ? interface_opts->console_display_name : "(unspecified)");
+        g_log(log_domain, log_level, "Display name[%02d]: %s", i, interface_opts->display_name ? interface_opts->display_name : "(unspecified)");
         g_log(log_domain, log_level, "Capture filter[%02d]  : %s", i, interface_opts->cfilter ? interface_opts->cfilter : "(unspecified)");
         g_log(log_domain, log_level, "Snap length[%02d] (%u) : %d", i, interface_opts->has_snaplen, interface_opts->snaplen);
         g_log(log_domain, log_level, "Link Type[%02d]       : %d", i, interface_opts->linktype);
@@ -499,6 +499,129 @@ get_auth_arguments(capture_options *capture_opts, const char *arg)
 }
 #endif
 
+#ifdef _WIN32
+static char *
+capture_opts_generate_display_name(const char *friendly_name,
+                                   const char *name _U_)
+{
+    /*
+     * Display the friendly name rather than the not-so-friendly
+     * GUID-based interface name.
+     */
+    return g_strdup(friendly_name);
+}
+#else
+static char *
+capture_opts_generate_display_name(const char *friendly_name,
+                                   const char *name)
+{
+    /*
+     * On UN*X, however, users are more used to interface names,
+     * and may find it helpful to see them.
+     */
+    return g_strdup_printf("%s: %s", friendly_name, name);
+}
+#endif
+
+static gboolean
+capture_opts_search_for_interface(interface_options *interface_opts,
+                                  const char *name)
+{
+    gboolean    matched;
+    GList       *if_list;
+    int         err;
+    GList       *if_entry;
+    if_info_t   *if_info;
+    size_t      prefix_length;
+
+    matched = FALSE;
+    if_list = capture_interface_list(&err, NULL, NULL);
+    if (if_list != NULL) {
+        /* try and do an exact match (case insensitive) */
+        for (if_entry = g_list_first(if_list); if_entry != NULL;
+             if_entry = g_list_next(if_entry))
+        {
+            if_info = (if_info_t *)if_entry->data;
+
+            /*
+             * Does the specified name match the interface name
+             * with a case-insensitive match?
+             */
+            if (g_ascii_strcasecmp(if_info->name, name) == 0) {
+                /*
+                 * Yes.
+                 */
+                matched = TRUE;
+                break;
+            }
+
+            /*
+             * Does this interface have a friendly name and, if so,
+             * does the specified name match the friendly name with
+             * a case-insensitive match?
+             */
+            if (if_info->friendly_name != NULL &&
+                g_ascii_strcasecmp(if_info->friendly_name, name) == 0) {
+                /*
+                 * Yes.
+                 */
+                matched = TRUE;
+                break;
+            }
+        }
+
+        if (!matched) {
+            /*
+             * We didn't find it; attempt a case-insensitive prefix match
+             * of the friendly name.
+             */
+            prefix_length = strlen(name);
+            for (if_entry = g_list_first(if_list); if_entry != NULL;
+                 if_entry = g_list_next(if_entry))
+            {
+                if_info = (if_info_t *)if_entry->data;
+
+                if (if_info->friendly_name != NULL &&
+                    g_ascii_strncasecmp(if_info->friendly_name, name, prefix_length) == 0) {
+                    /*
+                     * We found an interface whose friendly name matches
+                     * with a case-insensitive prefix match.
+                     */
+                    matched = TRUE;
+                    break;
+                }
+            }
+        }
+    }
+
+    if (matched) {
+        /*
+         * We found an interface that matches.
+         */
+        interface_opts->name = g_strdup(if_info->name);
+
+        if (if_info->friendly_name != NULL) {
+            /*
+             * We have a friendly name; remember it as the
+             * description...
+             */
+            interface_opts->descr = g_strdup(if_info->friendly_name);
+            /*
+             * ...and use it in the console display name.
+             */
+            interface_opts->display_name = capture_opts_generate_display_name(if_info->friendly_name, if_info->name);
+        } else {
+            /* fallback to the interface name */
+            interface_opts->descr = NULL;
+            interface_opts->display_name = g_strdup(if_info->name);
+        }
+        interface_opts->if_type = if_info->type;
+        interface_opts->extcap = g_strdup(if_info->extcap);
+    }
+    free_interface_list(if_list);
+    return matched;
+}
+
 static int
 capture_opts_add_iface_opt(capture_options *capture_opts, const char *optarg_str_p)
 {
@@ -551,132 +674,65 @@ capture_opts_add_iface_opt(capture_options *capture_opts, const char *optarg_str
         interface_opts.name = g_strdup(if_info->name);
         if (if_info->friendly_name != NULL) {
             /*
+             * We have a friendly name for the interface, so remember that
+             * as the description.
+             */
+            interface_opts.descr = g_strdup(if_info->friendly_name);
+            interface_opts.display_name = capture_opts_generate_display_name(if_info->friendly_name, if_info->name);
+        } else {
+            /* fallback to the interface name */
+            interface_opts.descr = NULL;
+            interface_opts.display_name = g_strdup(if_info->name);
+        }
+        interface_opts.if_type = if_info->type;
+        interface_opts.extcap = g_strdup(if_info->extcap);
+        free_interface_list(if_list);
+    } else if (capture_opts->capture_child) {
+        /*
+         * In Wireshark capture child mode, so the exact interface name
+         * is supplied, and we don't need to look it up.
+         */
+	if_info = if_info_get(optarg_str_p);
+        interface_opts.name = g_strdup(if_info->name);
+        if (if_info->friendly_name != NULL) {
+            /*
              * We have a friendly name for the interface, so display that
              * instead of the interface name/guid.
              *
              * XXX - on UN*X, the interface name is not quite so ugly,
              * and might be more familiar to users; display them both?
              */
-            interface_opts.console_display_name = g_strdup(if_info->friendly_name);
+            interface_opts.descr = g_strdup(if_info->friendly_name);
+            interface_opts.display_name = g_strdup(if_info->friendly_name);
         } else {
+            interface_opts.descr = NULL;
             /* fallback to the interface name */
-            interface_opts.console_display_name = g_strdup(if_info->name);
+            interface_opts.display_name = g_strdup(if_info->name);
         }
         interface_opts.if_type = if_info->type;
         interface_opts.extcap = g_strdup(if_info->extcap);
-        free_interface_list(if_list);
-    } else if (capture_opts->capture_child) {
-        /* In Wireshark capture child mode, thus proper device name is supplied. */
-        /* No need for trying to match it for friendly names. */
-        interface_opts.name = g_strdup(optarg_str_p);
-        interface_opts.console_display_name = g_strdup(optarg_str_p);
-        interface_opts.if_type = capture_opts->default_options.if_type;
-        interface_opts.extcap = g_strdup(capture_opts->default_options.extcap);
+        if_info_free(if_info);
     } else {
         /*
-         * Retrieve the interface list so that we can search for the
-         * specified option amongst both the interface names and the
-         * friendly names and so that we find the friendly name even
-         * if an interface name was specified.
-         *
-         * If we can't get the list, just use the specified option as
-         * the interface name, so that the user can try specifying an
-         * interface explicitly for testing purposes.
+         * Search for that name in the interface list and, if we found
+         * it, fill in fields in the interface_opts structure.
          */
-        if_list = capture_interface_list(&err, NULL, NULL);
-        if (if_list != NULL) {
-            /* try and do an exact match (case insensitive) */
-            GList   *if_entry;
-            gboolean matched;
-
-            matched = FALSE;
-            for (if_entry = g_list_first(if_list); if_entry != NULL;
-                 if_entry = g_list_next(if_entry))
-            {
-                if_info = (if_info_t *)if_entry->data;
-                /* exact name check */
-                if (g_ascii_strcasecmp(if_info->name, optarg_str_p) == 0) {
-                    /* exact match on the interface name, use that for displaying etc */
-                    interface_opts.name = g_strdup(if_info->name);
-
-                    if (if_info->friendly_name != NULL) {
-                        /*
-                         * If we have a friendly name, use that for the
-                         * console display name, as it is the basis for
-                         * the auto generated temp filename.
-                         */
-                        interface_opts.console_display_name = g_strdup(if_info->friendly_name);
-                    } else {
-                        interface_opts.console_display_name = g_strdup(if_info->name);
-                    }
-                    interface_opts.if_type = if_info->type;
-                    interface_opts.extcap = g_strdup(if_info->extcap);
-                    matched = TRUE;
-                    break;
-                }
-
-                /* exact friendly name check */
-                if (if_info->friendly_name != NULL &&
-                    g_ascii_strcasecmp(if_info->friendly_name, optarg_str_p) == 0) {
-                    /* exact match - use the friendly name for display */
-                    interface_opts.name = g_strdup(if_info->name);
-                    interface_opts.console_display_name = g_strdup(if_info->friendly_name);
-                    interface_opts.if_type = if_info->type;
-                    interface_opts.extcap = g_strdup(if_info->extcap);
-                    matched = TRUE;
-                    break;
-                }
-            }
-
-            /* didn't find, attempt a case insensitive prefix match of the friendly name*/
-            if (!matched) {
-                size_t prefix_length;
-
-                prefix_length = strlen(optarg_str_p);
-                for (if_entry = g_list_first(if_list); if_entry != NULL;
-                     if_entry = g_list_next(if_entry))
-                {
-                    if_info = (if_info_t *)if_entry->data;
-
-                    if (if_info->friendly_name != NULL &&
-                        g_ascii_strncasecmp(if_info->friendly_name, optarg_str_p, prefix_length) == 0) {
-                        /* prefix match - use the friendly name for display */
-                        interface_opts.name = g_strdup(if_info->name);
-                        interface_opts.console_display_name = g_strdup(if_info->friendly_name);
-                        interface_opts.if_type = if_info->type;
-                        interface_opts.extcap = g_strdup(if_info->extcap);
-                        matched = TRUE;
-                        break;
-                    }
-                }
-            }
-            if (!matched) {
-                /*
-                 * We didn't find the interface in the list; just use
-                 * the specified name, so that, for example, if an
-                 * interface doesn't show up in the list for some
-                 * reason, the user can try specifying it explicitly
-                 * for testing purposes.
-                 */
-                interface_opts.name = g_strdup(optarg_str_p);
-                interface_opts.console_display_name = g_strdup(optarg_str_p);
-                interface_opts.if_type = capture_opts->default_options.if_type;
-                interface_opts.extcap = g_strdup(capture_opts->default_options.extcap);
-            }
-            free_interface_list(if_list);
-        } else {
+        if (!capture_opts_search_for_interface(&interface_opts, optarg_str_p)) {
+            /*
+             * We didn't find the interface in the list; just use
+             * the specified name, so that, for example, if an
+             * interface doesn't show up in the list for some
+             * reason, the user can try specifying it explicitly
+             * for testing purposes.
+             */
             interface_opts.name = g_strdup(optarg_str_p);
-            interface_opts.console_display_name = g_strdup(optarg_str_p);
+            interface_opts.descr = NULL;
+            interface_opts.display_name = g_strdup(optarg_str_p);
             interface_opts.if_type = capture_opts->default_options.if_type;
             interface_opts.extcap = g_strdup(capture_opts->default_options.extcap);
         }
     }
 
-    /*  We don't set iface_descr here because doing so requires
-     *  capture_ui_utils.c which requires epan/prefs.c which is
-     *  probably a bit too much dependency for here...
-     */
-    interface_opts.descr = g_strdup(capture_opts->default_options.descr);
     interface_opts.cfilter = g_strdup(capture_opts->default_options.cfilter);
     interface_opts.snaplen = capture_opts->default_options.snaplen;
     interface_opts.has_snaplen = capture_opts->default_options.has_snaplen;
@@ -1119,7 +1175,7 @@ capture_opts_del_iface(capture_options *capture_opts, guint if_index)
 
     g_free(interface_opts->name);
     g_free(interface_opts->descr);
-    g_free(interface_opts->console_display_name);
+    g_free(interface_opts->display_name);
     g_free(interface_opts->cfilter);
     g_free(interface_opts->timestamp_type);
     g_free(interface_opts->extcap);
@@ -1164,8 +1220,8 @@ collect_ifaces(capture_options *capture_opts)
         device = &g_array_index(capture_opts->all_ifaces, interface_t, i);
         if (!device->hidden && device->selected) {
             interface_opts.name = g_strdup(device->name);
-            interface_opts.descr = g_strdup(device->display_name);
-            interface_opts.console_display_name = g_strdup(device->name);
+            interface_opts.descr = g_strdup(device->friendly_name);
+            interface_opts.display_name = g_strdup(device->display_name);
             interface_opts.linktype = device->active_dlt;
             interface_opts.cfilter = g_strdup(device->cfilter);
             interface_opts.timestamp_type = g_strdup(device->timestamp_type);
diff --git a/capture_opts.h b/capture_opts.h
index 9bbd3e8599..d0b433706f 100644
--- a/capture_opts.h
+++ b/capture_opts.h
@@ -197,9 +197,9 @@ typedef struct link_row_tag {
 } link_row;
 
 typedef struct interface_options_tag {
-    gchar            *name;                 /* the name of the interface provided to winpcap/libpcap to specify the interface */
-    gchar            *descr;
-    gchar            *console_display_name; /* the name displayed in the console, also the basis for autonamed pcap filenames */
+    gchar            *name;                 /* the name of the interface supplied to libpcap/WinPcap/Npcap to specify the interface */
+    gchar            *descr;                /* a more user-friendly description of the interface; may be NULL if none */
+    gchar            *display_name;         /* the name displayed in the console and title bar */
     gchar            *cfilter;
     gboolean          has_snaplen;
     int               snaplen;
diff --git a/caputils/capture-pcap-util.c b/caputils/capture-pcap-util.c
index 1647511aa0..366d92e6c3 100644
--- a/caputils/capture-pcap-util.c
+++ b/caputils/capture-pcap-util.c
@@ -261,6 +261,150 @@ add_unix_interface_ifinfo(if_info_t *if_info, const char *name _U_,
 #endif
 
 if_info_t *
+if_info_get(const char *name)
+{
+	char *description = NULL;
+	if_info_t *if_info;
+#ifdef SIOCGIFDESCR
+	/*
+	 * Try to fetch the description of this interface.
+	 * XXX - this is only here because libpcap has no API to
+	 * get the description of a *single* interface; it really
+	 * needs both an API to get pcapng-IDB-style attributes
+	 * for a single interface and to get a list of interfaces
+	 * with pcapng-IDB-style attributes for each interface.
+	 */
+	int s;
+	struct ifreq ifrdesc;
+#ifndef IFDESCRSIZE
+	size_t descrlen = 64;
+#else
+	size_t descrlen = IFDESCRSIZE;
+#endif /* IFDESCRSIZE */
+
+	/*
+	 * Get the description for the interface.
+	 */
+	memset(&ifrdesc, 0, sizeof ifrdesc);
+	g_strlcpy(ifrdesc.ifr_name, name, sizeof ifrdesc.ifr_name);
+	s = socket(AF_INET, SOCK_DGRAM, 0);
+	if (s >= 0) {
+#ifdef __FreeBSD__
+		/*
+		 * On FreeBSD, if the buffer isn't big enough for the
+		 * description, the ioctl succeeds, but the description
+		 * isn't copied, ifr_buffer.length is set to the description
+		 * length, and ifr_buffer.buffer is set to NULL.
+		 */
+		for (;;) {
+			g_free(description);
+			if ((description = g_malloc(descrlen)) != NULL) {
+				ifrdesc.ifr_buffer.buffer = description;
+				ifrdesc.ifr_buffer.length = descrlen;
+				if (ioctl(s, SIOCGIFDESCR, &ifrdesc) == 0) {
+					if (ifrdesc.ifr_buffer.buffer ==
+					    description)
+						break;
+					else
+						descrlen = ifrdesc.ifr_buffer.length;
+				} else {
+					/*
+					 * Failed to get interface description.
+					 */
+					g_free(description);
+					description = NULL;
+					break;
+				}
+			} else
+				break;
+		}
+#else /* __FreeBSD__ */
+		/*
+		 * The only other OS that currently supports
+		 * SIOCGIFDESCR is OpenBSD, and it has no way
+		 * to get the description length - it's clamped
+		 * to a maximum of IFDESCRSIZE.
+		 */
+		if ((description = g_malloc(descrlen)) != NULL) {
+			ifrdesc.ifr_data = (caddr_t)description;
+			if (ioctl(s, SIOCGIFDESCR, &ifrdesc) != 0) {
+				/*
+				 * Failed to get interface description.
+				 */
+				g_free(description);
+				description = NULL;
+			}
+		}
+#endif /* __FreeBSD__ */
+		close(s);
+		if (description != NULL && strlen(description) == 0) {
+			/*
+			 * Description is empty, so discard it.
+			 */
+			g_free(description);
+			description = NULL;
+		}
+	}
+
+#ifdef __FreeBSD__
+	/*
+	 * For FreeBSD, if we didn't get a description, and this is
+	 * a device with a name of the form usbusN, label it as a USB
+	 * bus.
+	 */
+	if (description == NULL) {
+		if (strncmp(name, "usbus", 5) == 0) {
+			/*
+			 * OK, it begins with "usbus".
+			 */
+			long busnum;
+			char *p;
+
+			errno = 0;
+			busnum = strtol(name + 5, &p, 10);
+			if (errno == 0 && p != name + 5 && *p == '\0' &&
+			    busnum >= 0 && busnum <= INT_MAX) {
+				/*
+				 * OK, it's a valid number that's not
+				 * bigger than INT_MAX.  Construct
+				 * a description from it.
+				 */
+				static const char descr_prefix[] = "USB bus number ";
+				size_t descr_size;
+
+				/*
+				 * Allow enough room for a 32-bit bus number.
+				 * sizeof (descr_prefix) includes the
+				 * terminating NUL.
+				 */
+				descr_size = sizeof (descr_prefix) + 10;
+				description = g_malloc(descr_size);
+				if (description != NULL) {
+					pcap_snprintf(description, descr_size,
+					    "%s%ld", descr_prefix, busnum);
+				}
+			}
+		}
+	}
+#endif /* __FreeBSD__ */
+#endif /* SIOCGIFDESCR */
+	if_info = if_info_new(name, description, FALSE);
+	g_free(description);
+	return if_info;
+}
+
+void
+if_info_free(if_info_t *if_info)
+{
+	g_free(if_info->name);
+	g_free(if_info->friendly_name);
+	g_free(if_info->vendor_description);
+	g_free(if_info->extcap);
+	g_slist_free_full(if_info->addrs, g_free);
+	g_free(if_info);
+}
+
+if_info_t *
 if_info_new(const char *name, const char *description, gboolean loopback)
 {
 	if_info_t *if_info;
@@ -528,14 +672,7 @@ get_interface_list_findalldevs(int *err, char **err_str)
 static void
 free_if_cb(gpointer data, gpointer user_data _U_)
 {
-	if_info_t *if_info = (if_info_t *)data;
-
-	g_free(if_info->name);
-	g_free(if_info->friendly_name);
-	g_free(if_info->vendor_description);
-	g_free(if_info->extcap);
-	g_slist_free_full(if_info->addrs, g_free);
-	g_free(if_info);
+	if_info_free((if_info_t *)data);
 }
 
 void
diff --git a/caputils/capture_ifinfo.h b/caputils/capture_ifinfo.h
index 7ee447aa5c..171561d16c 100644
--- a/caputils/capture_ifinfo.h
+++ b/caputils/capture_ifinfo.h
@@ -75,6 +75,17 @@ extern GList *capture_interface_list(int *err, char **err_str, void (*update_cb)
 
 void free_interface_list(GList *if_list);
 
+/**
+ * Get an if_info_t for a particular interface.
+ * (May require privilege, so should only be used by dumpcap.)
+ */
+extern if_info_t *if_info_get(const char *name);
+
+/**
+ * Free an if_info_t.
+ */
+void if_info_free(if_info_t *if_info);
+
 /*
  * "get_if_capabilities()" and "capture_if_capabilities()" return a pointer
  * to an allocated instance of this structure.  "free_if_capabilities()"
diff --git a/dumpcap.c b/dumpcap.c
index f17424b738..1fad72bcd8 100644
--- a/dumpcap.c
+++ b/dumpcap.c
@@ -3310,23 +3310,57 @@ capture_loop_open_output(capture_options *capture_opts, int *save_file_fd,
             prefix = g_strdup_printf("wireshark_%d_interfaces", global_capture_opts.ifaces->len);
         } else {
             /*
-             * One interface; use its name to generate the temporary file
-             * name prefix.
+             * One interface; use its description, if it has one, to generate
+             * the temporary file name, otherwise use its name.
              */
             gchar *basename;
-            basename = g_path_get_basename((&g_array_index(global_capture_opts.ifaces, interface_options, 0))->console_display_name);
+            const interface_options *interface_opts;
+
+            interface_opts = &g_array_index(global_capture_opts.ifaces, interface_options, 0);
+
+            /*
+             * Do we have a description?
+             */
+            if (interface_opts->descr) {
+                /*
+                 * Yes - use it.
+                 *
+                 * Strip off any stuff we shouldn't use in the file name,
+                 * by getting the last component of what would be a file
+                 * name.
+                 */
+                basename = g_path_get_basename(interface_opts->descr);
+            } else {
+                /*
+                 * No - use the name.
+                 *
+                 * Strip off any stuff we shouldn't use in the file name,
+                 * by getting the last component of what would be a file
+                 * name.
+                 */
+                basename = g_path_get_basename(interface_opts->name);
 #ifdef _WIN32
-            /* use the generic portion of the interface guid to form the basis of the filename */
-            if (strncmp("NPF_{", basename, 5)==0)
-            {
-                /* we have a windows guid style device name, extract the guid digits as the basis of the filename */
-                GString *iface;
-                iface = isolate_uuid(basename);
-                g_free(basename);
-                basename = g_strdup(iface->str);
-                g_string_free(iface, TRUE);
-            }
+                /*
+                 * This is Windows, where we might have an ugly GUID-based
+                 * interface name.
+                 *
+                 * If it's an ugly GUID-based name, use the generic portion
+                 * of the interface GUID to form the basis of the filename.
+                 */
+                if (strncmp("NPF_{", basename, 5) == 0) {
+                    /*
+                     * We have a GUID-based name; extract the GUID digits
+                     * as the basis of the filename.
+                     */
+                    GString *iface;
+                    iface = isolate_uuid(basename);
+                    g_free(basename);
+                    basename = g_strdup(iface->str);
+                    g_string_free(iface, TRUE);
+                }
 #endif
+            }
+            /* generate the temp file name prefix */
             prefix = g_strconcat("wireshark_", basename, NULL);
             g_free(basename);
         }
@@ -3990,7 +4024,7 @@ capture_loop_start(capture_options *capture_opts, gboolean *stats_known, struct
                 report_capture_error(errmsg, please_report);
             }
         }
-        report_packet_drops(received, pcap_dropped, pcap_src->dropped, pcap_src->flushed, stats->ps_ifdrop, interface_opts->console_display_name);
+        report_packet_drops(received, pcap_dropped, pcap_src->dropped, pcap_src->flushed, stats->ps_ifdrop, interface_opts->display_name);
     }
 
     /* close the input file (pcap or capture pipe) */
@@ -5141,7 +5175,7 @@ main(int argc, char *argv[])
                         g_string_append_printf(str, "and ");
                     }
                 }
-                g_string_append_printf(str, "'%s'", interface_opts->console_display_name);
+                g_string_append_printf(str, "'%s'", interface_opts->display_name);
             }
         } else {
             g_string_append_printf(str, "%u interfaces", global_capture_opts.ifaces->len);
diff --git a/ui/capture_ui_utils.c b/ui/capture_ui_utils.c
index 92ff44d77f..0f7fe1c39f 100644
--- a/ui/capture_ui_utils.c
+++ b/ui/capture_ui_utils.c
@@ -468,23 +468,27 @@ get_if_name(const char *if_text)
     return if_name;
 }
 
-/*  Return interface_opts->descr (after setting it if it is not set)
- *  This is necessary because capture_opts.c can't set descr (at least
- *  not without adding significant dependencies there).
+/*  Return a display name for the interface.
  */
 static const char *
-get_iface_description_for_interface(capture_options *capture_opts, guint i)
+get_display_name_for_interface(capture_options *capture_opts, guint i)
 {
     interface_options *interface_opts;
 
     if (i < capture_opts->ifaces->len) {
         interface_opts = &g_array_index(capture_opts->ifaces, interface_options, i);
-        if (!interface_opts->descr && interface_opts->name) {
-            interface_opts->descr = get_interface_descriptive_name(interface_opts->name);
+        if (interface_opts->display_name) {
+            return interface_opts->display_name;
         }
-        return (interface_opts->descr);
+        if (!interface_opts->display_name) {
+            if (interface_opts->descr && interface_opts->name) {
+                interface_opts->descr = get_interface_descriptive_name(interface_opts->name);
+            }
+            interface_opts->display_name = g_strdup(interface_opts->descr);
+        }
+        return interface_opts->display_name;
     } else {
-        return (NULL);
+        return NULL;
     }
 }
 
@@ -569,7 +573,7 @@ get_iface_list_string(capture_options *capture_opts, guint32 style)
                 }
                 if (style & IFLIST_QUOTE_IF_DESCRIPTION)
                     g_string_append_printf(iface_list_string, "'");
-                g_string_append_printf(iface_list_string, "%s", get_iface_description_for_interface(capture_opts, i));
+                g_string_append_printf(iface_list_string, "%s", get_display_name_for_interface(capture_opts, i));
                 if (style & IFLIST_QUOTE_IF_DESCRIPTION)
                     g_string_append_printf(iface_list_string, "'");
                 if (style & IFLIST_SHOW_FILTER) {