support juice_bind_stun to reflect stun requests from unbound client.

include/juice/juice.h

@@ -64,6 +64,17 @@ typedef void (*juice_cb_gathering_done_t)(juice_agent_t *agent, void *user_ptr);
 typedef void (*juice_cb_recv_t)(juice_agent_t *agent, const char *data, size_t size,
                                 void *user_ptr);
 
+typedef struct juice_stun_binding {
+	const char *ufrag;
+	const char *pwd;
+
+	uint8_t family;
+	const char *address;
+	uint16_t port;
+} juice_stun_binding_t;
+
+typedef void (*juice_cb_stun_binding_t)(const juice_stun_binding_t *info);
+
 typedef struct juice_turn_server {
 	const char *host;
 	const char *username;
@@ -118,6 +129,7 @@ JUICE_EXPORT int juice_get_selected_addresses(juice_agent_t *agent, char *local,
                                               char *remote, size_t remote_size);
 JUICE_EXPORT int juice_set_local_ice_attributes(juice_agent_t *agent, const char *ufrag, const char *pwd);
 JUICE_EXPORT const char *juice_state_to_string(juice_state_t state);
+JUICE_EXPORT int juice_bind_stun(const char *bind_address, int local_port, juice_cb_stun_binding_t cb);
 
 // ICE server
 

src/conn.c

@@ -108,7 +108,7 @@ static void release_registry(conn_mode_entry_t *entry) {
 
 	// registry must be locked
 
-	if (registry->agents_count == 0) {
+	if (registry->agents_count == 0 && registry->cb_stun_binding == NULL) {
 		JLOG_DEBUG("No connection left, destroying connections registry");
 		mutex_unlock(&registry->mutex);
 
@@ -247,3 +247,30 @@ int conn_get_addrs(juice_agent_t *agent, addr_record_t *records, size_t size) {
 
 	return get_mode_entry(agent)->get_addrs_func(agent, records, size);
 }
+
+int juice_bind_stun(const char *bind_address, int local_port, juice_cb_stun_binding_t cb)
+{
+	conn_mode_entry_t *entry = &mode_entries[JUICE_CONCURRENCY_MODE_MUX];
+
+	udp_socket_config_t config;
+	config.bind_address = bind_address;
+	config.port_begin = config.port_end = local_port;
+
+	mutex_lock(&entry->mutex);
+
+	if (entry->registry) {
+		mutex_unlock(&entry->mutex);
+		return -1;
+	}
+
+	conn_registry_t *registry = acquire_registry(entry, &config);
+	mutex_unlock(&entry->mutex);
+
+	if (!registry)
+		return -2;
+
+	registry->cb_stun_binding = cb;
+	mutex_unlock(&registry->mutex);
+
+	return 0;
+}

src/conn.h

@@ -30,6 +30,7 @@ typedef struct conn_registry {
 	juice_agent_t **agents;
 	int agents_size;
 	int agents_count;
+	juice_cb_stun_binding_t cb_stun_binding;
 } conn_registry_t;
 
 int conn_create(juice_agent_t *agent, udp_socket_config_t *config);

src/conn_mux.c

@@ -243,6 +243,8 @@ int conn_mux_prepare(conn_registry_t *registry, struct pollfd *pfd, timestamp_t
 	}
 
 	int count = registry->agents_count;
+	if (registry->cb_stun_binding)
+		++count;
 	mutex_unlock(&registry->mutex);
 	return count;
 }
@@ -295,6 +297,32 @@ static juice_agent_t *lookup_agent(conn_registry_t *registry, char *buf, size_t
 			}
 		}
 
+		if (registry->cb_stun_binding) {
+			JLOG_DEBUG("Found STUN agent for unknown ICE ufrag");
+			const struct sockaddr *sa = (const struct sockaddr *)&src->addr;
+
+			socklen_t salen = addr_get_len(sa);
+			if (salen == 0)
+				return NULL;
+
+			char host[ADDR_MAX_NUMERICHOST_LEN];
+			if (getnameinfo(sa, salen, host, ADDR_MAX_NUMERICHOST_LEN, NULL, 0, NI_NUMERICHOST)) {
+				JLOG_ERROR("getnameinfo failed, errno=%d", sockerrno);
+				return NULL;
+			}
+
+			juice_stun_binding_t binding_info;
+
+			binding_info.ufrag = username;
+			binding_info.pwd = separator + 1;
+			binding_info.family = (uint8_t)sa->sa_family;
+			binding_info.address = host;
+			binding_info.port = addr_get_port((struct sockaddr *)src);
+
+			registry->cb_stun_binding(&binding_info);
+
+			return NULL;
+		}
 	} else {
 		if (!STUN_IS_RESPONSE(msg.msg_class)) {
 			JLOG_INFO("Got unexpected STUN message from unknown source address");