wifi: esp_at: cleanup sockets at network close

Some sockets (UDP sockets at least) do not generate "<N>,CLOSED"
messages when the WiFi network drops. As a result the networking stack
thinks these sockets are still open after the network has dropped, and
after any subsequent reconnections.

This affects the DNS resolver library in particular, which leaves UDP
sockets open permanently by default.

Manually close these sockets when the network drops to ensure a clean
state the next time the network connects.

Signed-off-by: Jordan Yates <[email protected]>

Author: Jordan Yates

drivers/wifi/esp_at/esp.c

@@ -384,20 +384,37 @@ MODEM_CMD_DEFINE(on_cmd_wifi_connected)
 	return 0;
 }
 
-MODEM_CMD_DEFINE(on_cmd_wifi_disconnected)
+static void esp_mgmt_disconnect_work(struct k_work *work)
 {
-	struct esp_data *dev = CONTAINER_OF(data, struct esp_data,
-					    cmd_handler_data);
+	struct esp_socket *sock;
+	struct esp_data *dev;
 
-	if (!esp_flags_are_set(dev, EDF_STA_CONNECTED)) {
-		return 0;
+	dev = CONTAINER_OF(work, struct esp_data, disconnect_work);
+
+	/* Cleanup any sockets that weren't closed */
+	for (int i = 0; i < ARRAY_SIZE(dev->sockets); i++) {
+		sock = &dev->sockets[i];
+		if (esp_socket_connected(sock)) {
+			LOG_WRN("Socket %d left open, manually closing", i);
+			esp_socket_close(sock);
+		}
 	}
 
 	esp_flags_clear(dev, EDF_STA_CONNECTED);
 	esp_mode_switch_submit_if_needed(dev);
 
 	net_if_ipv4_addr_rm(dev->net_iface, &dev->ip);
 	wifi_mgmt_raise_disconnect_result_event(dev->net_iface, 0);
+}
+
+MODEM_CMD_DEFINE(on_cmd_wifi_disconnected)
+{
+	struct esp_data *dev = CONTAINER_OF(data, struct esp_data,
+					    cmd_handler_data);
+
+	if (esp_flags_are_set(dev, EDF_STA_CONNECTED)) {
+		k_work_submit_to_queue(&dev->workq, &dev->disconnect_work);
+	}
 
 	return 0;
 }
@@ -1102,6 +1119,7 @@ static int esp_init(const struct device *dev)
 	k_work_init_delayable(&data->ip_addr_work, esp_ip_addr_work);
 	k_work_init(&data->scan_work, esp_mgmt_scan_work);
 	k_work_init(&data->connect_work, esp_mgmt_connect_work);
+	k_work_init(&data->disconnect_work, esp_mgmt_disconnect_work);
 	k_work_init(&data->mode_switch_work, esp_mode_switch_work);
 	if (IS_ENABLED(CONFIG_WIFI_ESP_AT_DNS_USE)) {
 		k_work_init(&data->dns_work, esp_dns_work);

drivers/wifi/esp_at/esp.h

@@ -250,6 +250,7 @@ struct esp_data {
 	struct k_work_delayable ip_addr_work;
 	struct k_work scan_work;
 	struct k_work connect_work;
+	struct k_work disconnect_work;
 	struct k_work mode_switch_work;
 	struct k_work dns_work;