knownnetworks: rework known frequencies

The current format for the .known_networks.freq file had a hidden
limitation of not being able to handle SSID's with some special
characters. Since the provisioning file path was used as the
group name the filename was limited to only characters supported
by l_settings groups, which conflicted with allowable SSID
characters.

Instead we can generate a unique UUID for each network and use
this as the group. For this particular case the group does not
really matter, so long as its unique. But we can utilize this unique
UUID for other purposes, including using it as a seed for changing
the MAC address per-connection in the future.

The .known_networks.freq file will now have the following format:

[<UUID>]
name=/path/to/provisioning/file
list= XXXX YYYY ZZZZ

src/knownnetworks.c

@@ -29,6 +29,8 @@
 #include <errno.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <limits.h>
+#include <stdlib.h>
 
 #include <ell/ell.h>
 
@@ -735,9 +737,53 @@ static char *known_frequencies_to_string(struct l_queue *known_frequencies)
 	return l_string_unwrap(str);
 }
 
+struct hotspot_search {
+	struct network_info *info;
+	const char *path;
+};
+
+static bool match_hotspot_path(const struct network_info *info, void *user_data)
+{
+	struct hotspot_search *search = user_data;
+	char *path;
+
+	if (!info->is_hotspot)
+		return true;
+
+	path = info->ops->get_file_path(info);
+
+	if (!strcmp(path, search->path)) {
+		l_free(path);
+		search->info = (struct network_info *)info;
+		return false;
+	}
+
+	l_free(path);
+
+	return true;
+}
+
+static struct network_info *find_network_info_from_path(const char *path)
+{
+	enum security security;
+	struct hotspot_search search;
+	const char *ssid = storage_network_ssid_from_path(path, &security);
+
+	if (ssid)
+		return known_networks_find(ssid, security);
+
+	search.info = NULL;
+	search.path = path;
+
+	/* Try hotspot */
+	known_networks_foreach(match_hotspot_path, &search);
+
+	return search.info;
+}
+
 static void known_network_frequencies_load(void)
 {
-	char **network_names;
+	char **groups;
 	struct l_queue *known_frequencies;
 	uint32_t i;
 
@@ -747,41 +793,35 @@ static void known_network_frequencies_load(void)
 		return;
 	}
 
-	network_names = l_settings_get_groups(known_freqs);
-	if (!network_names[0])
-		goto done;
+	groups = l_settings_get_groups(known_freqs);
 
-	for (i = 0; network_names[i]; i++) {
-		struct network_info *network_info;
-		enum security security;
-		const char *ssid;
+	for (i = 0; groups[i]; i++) {
+		struct network_info *info;
 		char *freq_list;
-
-		ssid = storage_network_ssid_from_path(network_names[i],
-								&security);
-		if (!ssid)
+		const char *path = l_settings_get_value(known_freqs, groups[i],
+							"name");
+		if (!path)
 			continue;
 
-		freq_list = l_settings_get_string(known_freqs, network_names[i],
+		info = find_network_info_from_path(path);
+		if (!info)
+			continue;
+
+		freq_list = l_settings_get_string(known_freqs, groups[i],
 							"list");
 		if (!freq_list)
 			continue;
 
-		network_info = known_networks_find(ssid, security);
-		if (!network_info)
-			goto next;
-
 		known_frequencies = known_frequencies_from_string(freq_list);
 		if (!known_frequencies)
 			goto next;
 
-		network_info->known_frequencies = known_frequencies;
+		info->known_frequencies = known_frequencies;
 next:
 		l_free(freq_list);
 	}
 
-done:
-	l_strv_free(network_names);
+	l_strv_free(groups);
 }
 
 /*
@@ -791,6 +831,16 @@ void known_network_frequency_sync(const struct network_info *info)
 {
 	char *freq_list_str;
 	char *file_path;
+	char group[37];
+	uint8_t uuid[16];
+	/*
+	 * 16 bytes of randomness. Since we only care about a unique value there
+	 * is no need to use any special pre-defined namespace.
+	 */
+	static const uint8_t nsid[16] = {
+		0xfd, 0x88, 0x6f, 0x1e, 0xdf, 0x02, 0xd7, 0x8b,
+		0xc4, 0x90, 0x30, 0x59, 0x73, 0x8a, 0x86, 0x0d
+	};
 
 	if (!info->known_frequencies)
 		return;
@@ -802,7 +852,11 @@ void known_network_frequency_sync(const struct network_info *info)
 
 	file_path = info->ops->get_file_path(info);
 
-	l_settings_set_value(known_freqs, file_path, "list", freq_list_str);
+	l_uuid_v5(nsid, file_path, strlen(file_path), uuid);
+	l_uuid_to_string(uuid, group, sizeof(group));
+
+	l_settings_set_value(known_freqs, group, "name", file_path);
+	l_settings_set_value(known_freqs, group, "list", freq_list_str);
 	l_free(file_path);
 	l_free(freq_list_str);