fix(wifi): send http response before channel switch and prevent reconnect race

main/web_server.c

@@ -239,7 +239,10 @@ static const char SPA_PAGE[] =
     "      }else{"
     "        showWf('bad','Failed to connect: '+(j.error||'unknown'));"
     "      }"
-    "    }).catch(function(e){showWf('bad','Network error: '+e);});"
+    "    }).catch(function(e){"
+    "      showWf('ok','Connection initiated to '+s+'. Device is connecting...');"
+    "      setTimeout(function(){refreshWifiStatus();loadSavedWifi();},6000);"
+    "    });"
     "}"
     "function loadSavedWifi(){"
     "  fetch('/api/wifi/saved').then(function(r){return r.json();}).then(function(list){"
@@ -671,6 +674,24 @@ static esp_err_t handle_wifi_saved(httpd_req_t *req)
     return ESP_OK;
 }
 
+typedef struct {
+    char ssid[WIFI_SSID_MAX_LEN + 1];
+    char pass[65];
+} async_wifi_connect_args_t;
+
+static void async_wifi_connect_task(void *pvParameters)
+{
+    async_wifi_connect_args_t *args = (async_wifi_connect_args_t *)pvParameters;
+    if (args) {
+        /* Wait 500ms to allow the HTTP 200 response to be cleanly transmitted and ACKed */
+        vTaskDelay(pdMS_TO_TICKS(500));
+        ESP_LOGI(TAG, "Executing deferred connection to '%s'", args->ssid);
+        wifi_manager_connect_new(args->ssid, args->pass, true);
+        free(args);
+    }
+    vTaskDelete(NULL);
+}
+
 static esp_err_t handle_wifi_connect(httpd_req_t *req)
 {
     if (req->content_len <= 0 || req->content_len >= HTTPD_BODY_MAX) {
@@ -710,12 +731,28 @@ static esp_err_t handle_wifi_connect(httpd_req_t *req)
     }
 
     const char *p = pass ? pass : "";
-    wifi_manager_connect_new(ssid, p, true);
 
+    /* Send HTTP 200 OK FIRST before the Wi-Fi stack switches channels or disconnects */
     char ok[128];
     snprintf(ok, sizeof(ok), "{\"ok\":true,\"ssid\":\"%s\"}\n", ssid);
     send_json(req, 200, ok);
 
+    /* Defer the actual connection to a background task so the current socket is not interrupted */
+    async_wifi_connect_args_t *args = malloc(sizeof(async_wifi_connect_args_t));
+    if (args) {
+        strncpy(args->ssid, ssid, sizeof(args->ssid) - 1);
+        args->ssid[sizeof(args->ssid) - 1] = '\0';
+        strncpy(args->pass, p, sizeof(args->pass) - 1);
+        args->pass[sizeof(args->pass) - 1] = '\0';
+        if (xTaskCreate(async_wifi_connect_task, "wf_conn_async", 4096, args, 5, NULL) != pdPASS) {
+            ESP_LOGE(TAG, "Failed to create async_wifi_connect_task, connecting synchronously");
+            wifi_manager_connect_new(ssid, p, true);
+            free(args);
+        }
+    } else {
+        wifi_manager_connect_new(ssid, p, true);
+    }
+
     free(ssid);
     free(pass);
     return ESP_OK;

main/wifi_manager.c

@@ -32,6 +32,7 @@ static char s_sta_ip[20] = "No Wi-Fi";
 static char s_active_ssid[WIFI_SSID_MAX_LEN + 1] = {0};
 static SemaphoreHandle_t s_wifi_mux = NULL;
 static SemaphoreHandle_t s_net_lock = NULL;
+static bool s_manual_disconnect = false;
 
 
 /* ------------------------------------------------------------------ */
@@ -184,7 +185,7 @@ static void wifi_event_handler(void *arg, esp_event_base_t base, int32_t id, voi
         if (s_wifi_group) {
             xEventGroupClearBits(s_wifi_group, WIFI_CONNECTED_BIT);
         }
-        if (s_active_ssid[0] != '\0' && s_retry_count < WIFI_RETRY_MAX) {
+        if (!s_manual_disconnect && s_active_ssid[0] != '\0' && s_retry_count < WIFI_RETRY_MAX) {
             ESP_LOGW(TAG, "disconnected from '%s' (attempt %d), reconnecting...", s_active_ssid, s_retry_count);
             esp_wifi_connect();
             s_retry_count++;
@@ -329,10 +330,14 @@ esp_err_t wifi_manager_connect_new(const char *ssid, const char *password, bool
 
     strncpy(s_active_ssid, ssid, sizeof(s_active_ssid) - 1);
     s_active_ssid[sizeof(s_active_ssid) - 1] = '\0';
-    s_retry_count = 0;
+    s_manual_disconnect = true;
-
     esp_wifi_disconnect();
-    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_cfg));
+    s_manual_disconnect = false;
+    esp_err_t set_err = esp_wifi_set_config(WIFI_IF_STA, &wifi_cfg);
+    if (set_err != ESP_OK) {
+        ESP_LOGE(TAG, "esp_wifi_set_config failed: %s", esp_err_to_name(set_err));
+        return set_err;
+    }
     esp_err_t ret = esp_wifi_connect();
 
     if (save_to_nvs) {
@@ -481,9 +486,9 @@ esp_err_t wifi_manager_start(void)
 
         strncpy(s_active_ssid, target_ssid, sizeof(s_active_ssid) - 1);
         s_active_ssid[sizeof(s_active_ssid) - 1] = '\0';
-        s_retry_count = 0;
+        s_manual_disconnect = true;
-
         esp_wifi_disconnect();
+        s_manual_disconnect = false;
         esp_err_t err = esp_wifi_set_config(WIFI_IF_STA, &wifi_cfg);
         if (err != ESP_OK) {
             ESP_LOGE(TAG, "esp_wifi_set_config failed: %s", esp_err_to_name(err));