End the web_server captive DNS when the provisioning window closes and report a DNS start failure

esphome/components/web_server/web_server.cpp

@@ -444,9 +444,12 @@ void WebServer::start_captive() {
   if (this->dns_.is_running())
     return;
   network::IPAddress ip = wifi::global_wifi_component->wifi_soft_ap_ip();
-  this->dns_.start(ip);
-  this->enable_loop();
   char ip_buf[network::IP_ADDRESS_BUFFER_SIZE];
+  if (!this->dns_.start(ip)) {
+    ESP_LOGW(TAG, "AP mode: captive DNS failed to start; open http://%s/ manually", ip.str_to(ip_buf));
+    return;
+  }
+  this->enable_loop();
   ESP_LOGI(TAG, "AP mode: serving the web interface as captive portal at http://%s/", ip.str_to(ip_buf));
 }
 

esphome/components/web_server_base/captive_dns.h

@@ -20,16 +20,21 @@ namespace esphome::web_server_base {
 // The server object only exists while running, so an idle owner (AP not up) pays one pointer.
 class CaptiveDNS {
  public:
-  void start(const network::IPAddress &ip) {
+  /// Returns false when the DNS server could not start; nothing is kept, so a later start retries.
+  bool start(const network::IPAddress &ip) {
     if (this->dns_server_ != nullptr)
-      return;
-    this->dns_server_ = make_unique<DNSServer>();
+      return true;
+    auto server = make_unique<DNSServer>();
 #if defined(USE_ESP32)
-    this->dns_server_->start(ip);
+    const bool started = server->start(ip);
 #elif defined(USE_ARDUINO)
-    this->dns_server_->setErrorReplyCode(DNSReplyCode::NoError);
-    this->dns_server_->start(53, ESPHOME_F("*"), ip);
+    server->setErrorReplyCode(DNSReplyCode::NoError);
+    const bool started = server->start(53, ESPHOME_F("*"), ip);
 #endif
+    if (!started)
+      return false;
+    this->dns_server_ = std::move(server);
+    return true;
   }
   void stop() {
     if (this->dns_server_ == nullptr)

esphome/components/web_server_base/dns_server_esp32_idf.cpp

@@ -46,7 +46,7 @@ struct DNSAnswer {
   uint32_t ip_addr;
 } __attribute__((packed));
 
-void DNSServer::start(const network::IPAddress &ip) {
+bool DNSServer::start(const network::IPAddress &ip) {
   this->server_ip_ = ip;
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
   char ip_buf[network::IP_ADDRESS_BUFFER_SIZE];
@@ -57,7 +57,7 @@ void DNSServer::start(const network::IPAddress &ip) {
   this->socket_ = socket::socket_ip_loop_monitored(SOCK_DGRAM, IPPROTO_UDP).release();
   if (this->socket_ == nullptr) {
     ESP_LOGE(TAG, "Socket create failed");
-    return;
+    return false;
   }
 
   // Set socket options
@@ -72,9 +72,10 @@ void DNSServer::start(const network::IPAddress &ip) {
   if (err != 0) {
     ESP_LOGE(TAG, "Bind failed: %d", errno);
     this->destroy_socket_();
-    return;
+    return false;
   }
   ESP_LOGV(TAG, "Bound to port %d", DNS_PORT);
+  return true;
 }
 
 void DNSServer::stop() {

esphome/components/web_server_base/dns_server_esp32_idf.h

@@ -13,7 +13,8 @@ namespace esphome::web_server_base {
 
 class DNSServer {
  public:
-  void start(const network::IPAddress &ip);
+  /// Returns false when the socket could not be created or bound.
+  bool start(const network::IPAddress &ip);
   void stop();
   void process_next_request();
 

esphome/components/wifi/wifi_component.cpp

@@ -638,13 +638,14 @@ void WiFiComponent::setup() {
 
 #if defined(USE_PROVISIONING) && defined(USE_WIFI_AP)
   // The access point is a provisioning surface: once the provisioning window has
-  // closed, shut it down (mirrors the teardown done on a successful connection).
-  // The captive portal registers its own closed-callback, and the fallback block
-  // in loop() is gated so neither is started again afterwards.
+  // closed, end both portals and shut it down (mirrors the teardown done on a
+  // successful connection). The fallback block in loop() is gated so none of them
+  // is started again afterwards.
   if (provisioning::global_provisioning_manager != nullptr) {
     provisioning::global_provisioning_manager->add_on_closed_callback([this]() {
       if (this->ap_setup_) {
         ESP_LOGD(TAG, "Provisioning window closed; disabling AP");
+        this->end_ap_portal_();
         this->wifi_mode_({}, false);
       }
     });

tests/components/web_server/common-ap-fallback.yaml

@@ -1,5 +1,12 @@
 # STA with AP fallback plus local: true opts the fallback into captive AP mode; exercises
-# the runtime start (fallback branch in wifi loop) and end (on STA connect) paths.
+# the runtime start (fallback branch in wifi loop) and end (on STA connect, and when the
+# provisioning window closes) paths.
+provisioning:
+  timeout: 1min
+
+api:
+  encryption:
+
 wifi:
   ssid: MySSID
   password: password1