[web_server_idf] Reduce heap allocations by using stack buffers

esphome/components/api/api_connection.cpp

@@ -133,8 +133,8 @@ void APIConnection::start() {
     return;
   }
   // Initialize client name with peername (IP address) until Hello message provides actual name
-  char peername[socket::SOCKADDR_STR_LEN];
-  this->helper_->set_client_name(this->helper_->get_peername_to(peername), strlen(peername));
+  const char *peername = this->helper_->get_client_peername();
+  this->helper_->set_client_name(peername, strlen(peername));
 }
 
 APIConnection::~APIConnection() {
@@ -179,8 +179,8 @@ void APIConnection::begin_iterator_(ActiveIterator type) {
 
 void APIConnection::loop() {
   if (this->flags_.next_close) {
-    // requested a disconnect - don't close socket here, let APIServer::loop() do it
-    // so getpeername() still works for the disconnect trigger
+    // requested a disconnect
+    this->helper_->close();
     this->flags_.remove = true;
     return;
   }
@@ -293,8 +293,7 @@ bool APIConnection::send_disconnect_response(const DisconnectRequest &msg) {
   return this->send_message(resp, DisconnectResponse::MESSAGE_TYPE);
 }
 void APIConnection::on_disconnect_response(const DisconnectResponse &value) {
-  // Don't close socket here, let APIServer::loop() do it
-  // so getpeername() still works for the disconnect trigger
+  this->helper_->close();
   this->flags_.remove = true;
 }
 
@@ -1525,11 +1524,8 @@ void APIConnection::complete_authentication_() {
   this->flags_.connection_state = static_cast<uint8_t>(ConnectionState::AUTHENTICATED);
   this->log_client_(ESPHOME_LOG_LEVEL_DEBUG, LOG_STR("connected"));
 #ifdef USE_API_CLIENT_CONNECTED_TRIGGER
-  {
-    char peername[socket::SOCKADDR_STR_LEN];
-    this->parent_->get_client_connected_trigger()->trigger(std::string(this->helper_->get_client_name()),
-                                                           std::string(this->helper_->get_peername_to(peername)));
-  }
+  this->parent_->get_client_connected_trigger()->trigger(std::string(this->helper_->get_client_name()),
+                                                         std::string(this->helper_->get_client_peername()));
 #endif
 #ifdef USE_HOMEASSISTANT_TIME
   if (homeassistant::global_homeassistant_time != nullptr) {
@@ -1548,9 +1544,8 @@ bool APIConnection::send_hello_response(const HelloRequest &msg) {
   this->helper_->set_client_name(msg.client_info.c_str(), msg.client_info.size());
   this->client_api_version_major_ = msg.api_version_major;
   this->client_api_version_minor_ = msg.api_version_minor;
-  char peername[socket::SOCKADDR_STR_LEN];
   ESP_LOGV(TAG, "Hello from client: '%s' | %s | API Version %" PRIu32 ".%" PRIu32, this->helper_->get_client_name(),
-           this->helper_->get_peername_to(peername), this->client_api_version_major_, this->client_api_version_minor_);
+           this->helper_->get_client_peername(), this->client_api_version_major_, this->client_api_version_minor_);
 
   HelloResponse resp;
   resp.api_version_major = 1;
@@ -1867,8 +1862,7 @@ void APIConnection::on_no_setup_connection() {
   this->log_client_(ESPHOME_LOG_LEVEL_DEBUG, LOG_STR("no connection setup"));
 }
 void APIConnection::on_fatal_error() {
-  // Don't close socket here - keep it open so getpeername() works for logging
-  // Socket will be closed when client is removed from the list in APIServer::loop()
+  this->helper_->close();
   this->flags_.remove = true;
 }
 
@@ -2224,14 +2218,12 @@ void APIConnection::process_state_subscriptions_() {
 #endif  // USE_API_HOMEASSISTANT_STATES
 
 void APIConnection::log_client_(int level, const LogString *message) {
-  char peername[socket::SOCKADDR_STR_LEN];
   esp_log_printf_(level, TAG, __LINE__, ESPHOME_LOG_FORMAT("%s (%s): %s"), this->helper_->get_client_name(),
-                  this->helper_->get_peername_to(peername), LOG_STR_ARG(message));
+                  this->helper_->get_client_peername(), LOG_STR_ARG(message));
 }
 
 void APIConnection::log_warning_(const LogString *message, APIError err) {
-  char peername[socket::SOCKADDR_STR_LEN];
-  ESP_LOGW(TAG, "%s (%s): %s %s errno=%d", this->helper_->get_client_name(), this->helper_->get_peername_to(peername),
+  ESP_LOGW(TAG, "%s (%s): %s %s errno=%d", this->helper_->get_client_name(), this->helper_->get_client_peername(),
            LOG_STR_ARG(message), LOG_STR_ARG(api_error_to_logstr(err)), errno);
 }
 

esphome/components/api/api_connection.h

@@ -281,10 +281,8 @@ class APIConnection final : public APIServerConnection {
   bool send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) override;
 
   const char *get_name() const { return this->helper_->get_client_name(); }
-  /// Get peer name (IP address) into caller-provided buffer, returns buf for convenience
-  const char *get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const {
-    return this->helper_->get_peername_to(buf);
-  }
+  /// Get peer name (IP address) - cached at connection init time
+  const char *get_peername() const { return this->helper_->get_client_peername(); }
 
  protected:
   // Helper function to handle authentication completion

esphome/components/api/api_frame_helper.cpp

@@ -16,12 +16,7 @@ static const char *const TAG = "api.frame_helper";
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) \
-  do { \
-    char peername_buf[socket::SOCKADDR_STR_LEN]; \
-    this->get_peername_to(peername_buf); \
-    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
-  } while (0)
+#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif
@@ -245,20 +240,13 @@ APIError APIFrameHelper::try_send_tx_buf_() {
   return APIError::OK;  // All buffers sent successfully
 }
 
-const char *APIFrameHelper::get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const {
-  if (this->socket_) {
-    this->socket_->getpeername_to(buf);
-  } else {
-    buf[0] = '\0';
-  }
-  return buf.data();
-}
-
 APIError APIFrameHelper::init_common_() {
   if (state_ != State::INITIALIZE || this->socket_ == nullptr) {
     HELPER_LOG("Bad state for init %d", (int) state_);
     return APIError::BAD_STATE;
   }
+  // Cache peername now while socket is valid - needed for error logging after socket failure
+  this->socket_->getpeername_to(this->client_peername_);
   int err = this->socket_->setblocking(false);
   if (err != 0) {
     state_ = State::FAILED;

esphome/components/api/api_frame_helper.h

@@ -90,9 +90,8 @@ class APIFrameHelper {
 
   // Get client name (null-terminated)
   const char *get_client_name() const { return this->client_name_; }
-  // Get client peername/IP into caller-provided buffer (fetches on-demand from socket)
-  // Returns pointer to buf for convenience in printf-style calls
-  const char *get_peername_to(std::span<char, socket::SOCKADDR_STR_LEN> buf) const;
+  // Get client peername/IP (null-terminated, cached at init time for availability after socket failure)
+  const char *get_client_peername() const { return this->client_peername_; }
   // Set client name from buffer with length (truncates if needed)
   void set_client_name(const char *name, size_t len) {
     size_t copy_len = std::min(len, sizeof(this->client_name_) - 1);
@@ -106,8 +105,6 @@ class APIFrameHelper {
   bool can_write_without_blocking() { return this->state_ == State::DATA && this->tx_buf_count_ == 0; }
   int getpeername(struct sockaddr *addr, socklen_t *addrlen) { return socket_->getpeername(addr, addrlen); }
   APIError close() {
-    if (state_ == State::CLOSED)
-      return APIError::OK;  // Already closed
     state_ = State::CLOSED;
     int err = this->socket_->close();
     if (err == -1)
@@ -234,6 +231,8 @@ class APIFrameHelper {
 
   // Client name buffer - stores name from Hello message or initial peername
   char client_name_[CLIENT_INFO_NAME_MAX_LEN]{};
+  // Cached peername/IP address - captured at init time for availability after socket failure
+  char client_peername_[socket::SOCKADDR_STR_LEN]{};
 
   // Group smaller types together
   uint16_t rx_buf_len_ = 0;

esphome/components/api/api_frame_helper_noise.cpp

@@ -29,12 +29,7 @@ static constexpr size_t PROLOGUE_INIT_LEN = 12;  // strlen("NoiseAPIInit")
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) \
-  do { \
-    char peername_buf[socket::SOCKADDR_STR_LEN]; \
-    this->get_peername_to(peername_buf); \
-    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
-  } while (0)
+#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif

esphome/components/api/api_frame_helper_plaintext.cpp

@@ -21,12 +21,7 @@ static const char *const TAG = "api.plaintext";
 static constexpr size_t API_MAX_LOG_BYTES = 168;
 
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERY_VERBOSE
-#define HELPER_LOG(msg, ...) \
-  do { \
-    char peername_buf[socket::SOCKADDR_STR_LEN]; \
-    this->get_peername_to(peername_buf); \
-    ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, peername_buf, ##__VA_ARGS__); \
-  } while (0)
+#define HELPER_LOG(msg, ...) ESP_LOGVV(TAG, "%s (%s): " msg, this->client_name_, this->client_peername_, ##__VA_ARGS__)
 #else
 #define HELPER_LOG(msg, ...) ((void) 0)
 #endif

esphome/components/api/api_server.cpp

@@ -192,15 +192,11 @@ void APIServer::loop() {
     ESP_LOGV(TAG, "Remove connection %s", client->get_name());
 
 #ifdef USE_API_CLIENT_DISCONNECTED_TRIGGER
-    // Save client info before closing socket and removal for the trigger
-    char peername_buf[socket::SOCKADDR_STR_LEN];
+    // Save client info before removal for the trigger
     std::string client_name(client->get_name());
-    std::string client_peername(client->get_peername_to(peername_buf));
+    std::string client_peername(client->get_peername());
 #endif
 
-    // Close socket now (was deferred from on_fatal_error to allow getpeername)
-    client->helper_->close();
-
     // Swap with the last element and pop (avoids expensive vector shifts)
     if (client_index < this->clients_.size() - 1) {
       std::swap(this->clients_[client_index], this->clients_.back());

esphome/components/mhz19/mhz19.cpp

@@ -155,6 +155,9 @@ void MHZ19Component::dump_config() {
     case MHZ19_DETECTION_RANGE_0_10000PPM:
       range_str = "0 to 10000ppm";
       break;
+    default:
+      range_str = "default";
+      break;
   }
   ESP_LOGCONFIG(TAG, "  Detection range: %s", range_str);
 }

esphome/components/voice_assistant/voice_assistant.cpp

@@ -430,14 +430,12 @@ void VoiceAssistant::client_subscription(api::APIConnection *client, bool subscr
   }
 
   if (this->api_client_ != nullptr) {
-    char current_peername[socket::SOCKADDR_STR_LEN];
-    char new_peername[socket::SOCKADDR_STR_LEN];
     ESP_LOGE(TAG,
              "Multiple API Clients attempting to connect to Voice Assistant\n"
              "Current client: %s (%s)\n"
              "New client: %s (%s)",
-             this->api_client_->get_name(), this->api_client_->get_peername_to(current_peername), client->get_name(),
-             client->get_peername_to(new_peername));
+             this->api_client_->get_name(), this->api_client_->get_peername(), client->get_name(),
+             client->get_peername());
     return;
   }
 

esphome/components/web_server_idf/utils.cpp

@@ -78,11 +78,8 @@ optional<std::string> query_key_value(const std::string &query_url, const std::s
     return {};
   }
 
-  auto val = std::unique_ptr<char[]>(new char[query_url.size()]);
-  if (!val) {
-    ESP_LOGE(TAG, "Not enough memory to the query key value");
-    return {};
-  }
+  // Use stack buffer for typical query strings, heap fallback for large ones
+  SmallBufferWithHeapFallback<256, char> val(query_url.size());
 
   if (httpd_query_key_value(query_url.c_str(), key.c_str(), val.get(), query_url.size()) != ESP_OK) {
     return {};

esphome/components/web_server_idf/web_server_idf.cpp

@@ -352,14 +352,15 @@ bool AsyncWebServerRequest::authenticate(const char *username, const char *passw
   memcpy(user_info + user_len + 1, password, pass_len);
   user_info[user_info_len] = '\0';
 
-  size_t n = 0, out;
-  esp_crypto_base64_encode(nullptr, 0, &n, reinterpret_cast<const uint8_t *>(user_info), user_info_len);
-
-  auto digest = std::unique_ptr<char[]>(new char[n + 1]);
-  esp_crypto_base64_encode(reinterpret_cast<uint8_t *>(digest.get()), n, &out,
+  // Base64 output size is ceil(input_len * 4/3) + 1, with input bounded to 256 bytes
+  // max output is ceil(256 * 4/3) + 1 = 343 bytes, use 350 for safety
+  constexpr size_t max_digest_len = 350;
+  char digest[max_digest_len];
+  size_t out;
+  esp_crypto_base64_encode(reinterpret_cast<uint8_t *>(digest), max_digest_len, &out,
                            reinterpret_cast<const uint8_t *>(user_info), user_info_len);
 
-  return strcmp(digest.get(), auth_str + auth_prefix_len) == 0;
+  return strcmp(digest, auth_str + auth_prefix_len) == 0;
 }
 
 void AsyncWebServerRequest::requestAuthentication(const char *realm) const {
@@ -869,12 +870,12 @@ esp_err_t AsyncWebServer::handle_multipart_upload_(httpd_req_t *r, const char *c
     }
   });
 
-  // Process data
-  std::unique_ptr<char[]> buffer(new char[MULTIPART_CHUNK_SIZE]);
+  // Process data - use stack buffer to avoid heap allocation
+  char buffer[MULTIPART_CHUNK_SIZE];
   size_t bytes_since_yield = 0;
 
   for (size_t remaining = r->content_len; remaining > 0;) {
-    int recv_len = httpd_req_recv(r, buffer.get(), std::min(remaining, MULTIPART_CHUNK_SIZE));
+    int recv_len = httpd_req_recv(r, buffer, std::min(remaining, MULTIPART_CHUNK_SIZE));
 
     if (recv_len <= 0) {
       httpd_resp_send_err(r, recv_len == HTTPD_SOCK_ERR_TIMEOUT ? HTTPD_408_REQ_TIMEOUT : HTTPD_400_BAD_REQUEST,
@@ -882,7 +883,7 @@ esp_err_t AsyncWebServer::handle_multipart_upload_(httpd_req_t *r, const char *c
       return recv_len == HTTPD_SOCK_ERR_TIMEOUT ? ESP_ERR_TIMEOUT : ESP_FAIL;
     }
 
-    if (reader->parse(buffer.get(), recv_len) != static_cast<size_t>(recv_len)) {
+    if (reader->parse(buffer, recv_len) != static_cast<size_t>(recv_len)) {
       ESP_LOGW(TAG, "Multipart parser error");
       httpd_resp_send_err(r, HTTPD_400_BAD_REQUEST, nullptr);
       return ESP_FAIL;