Add configurable Wi-Fi station mDNS hostname support. Mini-Feature #1

dependencies.lock

@@ -29,6 +29,16 @@ dependencies:
       registry_url: https://components.espressif.com/
       type: service
     version: 3.0.3
+  espressif/mdns:
+    component_hash: 3ba256ac95e07c274be53cbd73f06cb846c403b61e8fbdf1be57bdb79db7a63e
+    dependencies:
+    - name: idf
+      require: private
+      version: '>=5.0'
+    source:
+      registry_url: https://components.espressif.com/
+      type: service
+    version: 1.12.0
   espressif/tinyusb:
     component_hash: a72b7d67472914ab76309340fd50d578b31e310963d45ad0f81144bde3314752
     dependencies:
@@ -66,9 +76,10 @@ dependencies:
 direct_dependencies:
 - espressif/esp_tinyusb
 - espressif/led_strip
+- espressif/mdns
 - idf
 - wolfssl/wolfssh
 - wolfssl/wolfssl
-manifest_hash: 34e93560f67a22e2a43647a4663b450e07ecd9fa3fdc2ac38343c1a76b513f5d
+manifest_hash: 4b6fa5a7e06122f9194adfc282a4baf4247d8a114b905e65f6397503e59f0898
 target: esp32s3
 version: 2.0.0

docs/agent/architecture.md

@@ -159,12 +159,13 @@ Remote reboot, SSH stop/disconnect, and host-key rotate/reset use deferred contr
 
 `wifi_config` owns a fixed-width versioned NVS schema with four prioritized station profiles and AP policy `off`, `fallback`, or `always`. Missing configuration generates per-device defaults including a random AP password. Invalid stored data is generally left untouched while RAM defaults are used.
 
-`wifi_manager` is a permanent task with one bounded command/event queue. ESP-IDF callbacks only copy compact events into the queue. The task owns association, DHCP deadlines, profile failover, AP policy, retries/backoff, and next-profile requests. It also reconciles against authoritative driver/netif state so dropped events do not permanently wedge policy. ESP-IDF Wi-Fi storage is RAM-only; the application blob is authoritative, and edits require explicit save. Edits to disabled station profiles are staged in RAM without restarting the radio; enabling/disabling a profile or changing enabled station/AP policy restarts it asynchronously. Start/stop—including local controls—intentionally update the RAM `enabled_at_boot` field. Working-configuration copies contain PSKs and must be securely wiped; routine status and the local UI use secret-free snapshots.
+`wifi_manager` is a permanent task with one bounded command/event queue. ESP-IDF callbacks only copy compact events into the queue. The task owns association, DHCP deadlines, profile failover, AP policy, retries/backoff, next-profile requests, and the mDNS announcement lifecycle. `mdns_service` announces the configured hostname only after a validated STA `GOT_IP` transition and is stopped when that IPv4 reachability is lost or the radio is stopped; mDNS failure is nonfatal. It also reconciles against authoritative driver/netif state so dropped events do not permanently wedge policy. ESP-IDF Wi-Fi storage is RAM-only; the application blob is authoritative, and edits require explicit save. Edits to disabled station profiles are staged in RAM without restarting the radio; enabling/disabling a profile or changing enabled station/AP policy restarts it asynchronously. Start/stop—including local controls—intentionally update the RAM `enabled_at_boot` field. Working-configuration copies contain PSKs and must be securely wiped; routine status and the local UI use secret-free snapshots.
 
 Persistent namespaces/blobs include:
 
 - `serial/config`;
 - `wifi_app/config`;
+- `mdns_cfg/config`;
 - `local_ui/config`;
 - `web_sec/material`;
 - `user_db/database`;

docs/agent/code-map.md

@@ -112,10 +112,10 @@ This is a semantic map, not a complete file inventory. Start here, then read the
 
 **Responsibility:** persist station/AP policy and own asynchronous ESP-NETIF/Wi-Fi state transitions.
 
-- Files: `src/wifi_config.{h,c}`, `src/wifi_manager.{h,c}`, `src/wifi_console.{h,c}`, `src/network_console.{h,c}`
+- Files: `src/wifi_config.{h,c}`, `src/wifi_manager.{h,c}`, `src/wifi_console.{h,c}`, `src/mdns_config.{h,c}`, `src/mdns_service.{h,c}`, `src/mdns_console.{h,c}`, `src/network_console.{h,c}`
 - Interfaces: config defaults/validate/load/save; manager init/start/stop/apply/reconnect/next-profile/snapshot
 - Called by: startup, console, local UI, ESP event callbacks
-- Dependencies: secure random for default AP password, NVS, ESP-NETIF/Wi-Fi/events, lwIP diagnostics
+- Dependencies: secure random for default AP password, NVS, ESP-NETIF/Wi-Fi/events, Espressif mDNS, lwIP diagnostics
 - Lifecycle: permanent manager task and bounded queue; callbacks enqueue compact events only.
 - Constraint: application NVS is authoritative (`WIFI_STORAGE_RAM`); working edits are not persisted until save. Start/stop, including local controls, intentionally update the RAM `enabled_at_boot` field. Working-config copies contain PSKs and must be tightly scoped and wiped; routine status/local UI must use secret-free snapshots.
 
@@ -157,6 +157,7 @@ This is a semantic map, not a complete file inventory. Start here, then read the
 | Add or change a command | relevant `*_console.c`, `console_completion.c`, `admin_ssh_console.c` policy/deferred handling |
 | Change account roles/passwords/keys | `user_database.*`, `user_console.c`, transport revocation APIs |
 | Change Wi-Fi policy or profile persistence | `wifi_manager.*`, `wifi_config.*`, `wifi_console.c` |
+| Change station mDNS hostname or persistence | `mdns_service.*`, `mdns_config.*`, `mdns_console.c`, then `wifi_manager.c` |
 | Change OLED rendering or buttons | `local_status_ui.c`, `local_display.*`, `local_ui_config.*` |
 | Change board GPIO or electrical tests | `board_pins.h`, hardware test module, `docs/wiring.md` |
 | Change embedded browser assets | `web_assets/SOURCES.md`, generator, then generated data only as an explicit regeneration task |

docs/agent/current-state.md

@@ -46,13 +46,13 @@ These observations should be checked when touching the relevant area; they are n
 
 ## Active Task
 
-- **Objective:** Keep UART1 configuration independent of USB CDC host line coding, keep Phase 0 RS-232 status under `debug`, avoid disconnecting Wi-Fi for edits to disabled profiles, and add explicit web/admin-SSH session exit controls.
-- **Relevant files:** `src/usb_cdc_transport.{c,h}`, `src/usb_console.c`, `src/rs232_hw_test.c`, `src/console_completion.c`, `src/wifi_manager.{c,h}`, `src/web_ui.c`, `src/admin_ssh_console.{c,h}`, `src/main.c`, related documentation.
-- **Findings:** The USB transport converted cached CDC line coding into `serial_config_t` and called `serial_service_apply_config()` after writer acquisition. Root `status` was a Phase 0 diagnostic that needed to claim the RS-232 port and therefore failed while the production serial service owned it. Every Wi-Fi working-configuration update queued a radio restart, including edits to profiles disabled in both the old and new configurations.
-- **Decision:** Treat CDC line coding as diagnostic metadata only. UART1 configuration remains exclusively controlled by explicit `serial` commands and their NVS persistence. Keep all Phase 0 RS-232 diagnostics, including signal status, under `debug`. Treat disabled Wi-Fi profiles as staged configuration: their edits do not restart the radio; enable/disable transitions and changes to enabled station/AP policy retain controlled asynchronous restart behavior. Browser Disconnect pauses reconnect until Reconnect is selected. `exit`/empty-line Ctrl+D are admin-SSH-only deferred self-disconnect actions; role-`user` SSH remains binary-transparent.
-- **Changes completed:** Removed the pending line-coding apply path and its counters; retained the latest host setting for `usb status`. Replaced root `status` with `debug status`, updated completion and documentation. Added effective Wi-Fi policy comparison before queueing `MESSAGE_COMMAND_APPLY`. Added browser Disconnect and admin SSH `exit`/Ctrl+D session closing through the existing bounded drain path.
-- **Remaining work:** Target-hardware verification: acquire/release USB writer ownership after changing a host terminal's line coding and confirm UART1 remains at the configured framing. Verify `debug status` works after `serial stop` and root `status` is unknown. While connected through Wi-Fi, edit a disabled profile and its secret without a reconnect; then enable it and verify the expected reconnect. Verify browser Disconnect pauses automatic reconnect until Reconnect is selected, and admin SSH `exit`/empty Ctrl+D close cleanly.
-- **Risks / things to remember:** Host terminal line-coding selectors no longer configure the physical RS-232 port; use `serial set`/`serial save` instead. `debug status` remains ownership-protected and requires UART1 to be stopped. Enabling a profile may disconnect an SSH administrative session. `pio run` passed after all changes.
+- **Objective:** Announce a configurable `sak-<suffix>.local` hostname through mDNS when Wi-Fi STA has an IPv4 address, without changing the Wi-Fi NVS blob schema.
+- **Relevant files:** `src/mdns_config.{c,h}`, `src/mdns_service.{c,h}`, `src/mdns_console.{c,h}`, `src/wifi_manager.{c,h}`, `src/main.c`, `src/CMakeLists.txt`, `src/idf_component.yml`, `dependencies.lock`, completion and command documentation.
+- **Findings:** `wifi_manager` already serializes all meaningful STA transitions through its permanent task; callbacks only enqueue events. This is the appropriate lifecycle owner for mDNS, while a separate configuration module preserves the existing `wifi_app/config` wire format.
+- **Decision:** Persist a fixed v1 record under `mdns_cfg/config`, separate from Wi-Fi configuration. Defaults derive a safe lower-case hexadecimal suffix from the STA MAC. The manager starts mDNS after validating `IP_EVENT_STA_GOT_IP`, stops it on IPv4 loss, STA disconnect, and radio stop, and performs online reannouncements requested after configuration changes. mDNS errors are logged but cannot fail Wi-Fi, UART0, UART1, or native USB.
+- **Changes completed:** Added the `espressif/mdns` managed dependency (resolved to 1.12.0 on IDF 5.5), mDNS config/service/console modules, `mdns status|suffix|save|load|defaults|reset`, completion, CMake integration, and command/architecture documentation. `pio run` passes.
+- **Remaining work:** Target-hardware verification: associate a station and resolve the default `sak-<mac>.local`; change/save/load a suffix and confirm live reannouncement plus reboot persistence; stop Wi-Fi or remove the STA lease and confirm the record withdraws. Verify serial, native USB, and UART0 remain available if mDNS initialization fails.
+- **Risks / things to remember:** Hostnames are STA-only and are intentionally not announced by fallback AP mode. NVS changes to `mdns_cfg/config` are independent of the unchanged `wifi_app/config` blob.
 
 ### Handoff template
 

docs/command_reference.md

@@ -108,6 +108,17 @@ Opening `/dev/ttyACM*` with DTR asserted creates the `usb-cdc` broker client, st
 
 `ping`, `nslookup`, and `traceroute` are root aliases. The four station-profile slots use lower priority values first. Edits to a disabled profile's SSID, priority, security mode, or secret are staged in RAM and do not interrupt the current Wi-Fi connection. Enabling or disabling a profile, changing an enabled profile, or changing AP policy/configuration applies the new radio policy and may reconnect Wi-Fi. Use `wifi save` to persist working changes. Passwords are not displayed by ordinary status output.
 
+## mDNS
+
+| Command | Description |
+|---|---|
+| `mdns status` | Show the configured `sak-<suffix>.local` hostname and announcement state. |
+| `mdns suffix <value>` | Set a 1–55-character lowercase hostname suffix in RAM. |
+| `mdns save` / `mdns load` | Save the working suffix to its independent NVS record or load it. |
+| `mdns defaults` / `mdns reset` | Restore the MAC-derived suffix in RAM, or restore and persist it. |
+
+When the Wi-Fi station receives an IPv4 address, the Wi-Fi manager announces `sak-<suffix>.local`. The default suffix is the lower-case hexadecimal STA MAC address. Suffixes may contain lowercase ASCII letters, digits, and internal hyphens only. Changing a suffix while online causes a best-effort reannouncement; mDNS failures do not stop Wi-Fi, UART0, UART1, or native USB access.
+
 ## HTTPS web terminal
 
 | Command | Description |

src/CMakeLists.txt

@@ -38,6 +38,9 @@ idf_component_register(
         "wifi_config.c"
         "wifi_manager.c"
         "wifi_console.c"
+        "mdns_config.c"
+        "mdns_service.c"
+        "mdns_console.c"
     INCLUDE_DIRS "."
     REQUIRES
         bootloader_support
@@ -58,6 +61,7 @@ idf_component_register(
         led_strip
         lwip
         mbedtls
+        mdns
         nvs_flash
         wolfssl__wolfssh
         wolfssl__wolfssl

src/console_completion.c

@@ -12,7 +12,7 @@
 
 static const char *const s_root_candidates[] = {
     "help", "exit", "debug", "display", "serial", "broker", "usb", "user",
-    "wifi", "web", "ssh", "ping", "nslookup", "traceroute", "reboot", "memory",
+    "wifi", "mdns", "web", "ssh", "ping", "nslookup", "traceroute", "reboot", "memory",
 };
 
 /* Keep full-line candidate strings grouped by their registered root command. */
@@ -169,6 +169,14 @@ static const char *const s_completion_candidates[] = {
     "wifi nslookup",
     "wifi traceroute",
 
+    /* Station mDNS hostname configuration. */
+    "mdns status",
+    "mdns suffix",
+    "mdns save",
+    "mdns load",
+    "mdns defaults",
+    "mdns reset",
+
     /* Authenticated HTTPS lifecycle and physical-admin recovery operations. */
     "web help",
     "web status",

src/idf_component.yml

@@ -4,6 +4,7 @@ dependencies:
   idf: ">=5.3.0"
   espressif/led_strip: "^3.0.3"
   espressif/esp_tinyusb: "^2.2.1"
+  espressif/mdns: "^1.8.2"
   # Exact official registry versions form the reviewed Phase 6 integration baseline.
   wolfssl/wolfssl: "5.8.2~1"
   wolfssl/wolfssh: "1.4.20"

src/main.c

@@ -14,6 +14,9 @@
 #include "local_ui_config.h"
 #include "local_ui_console.h"
 #include "local_ui_hw_test.h"
+#include "mdns_config.h"
+#include "mdns_console.h"
+#include "mdns_service.h"
 #include "rs232_hw_test.h"
 #include "rs232_port_owner.h"
 #include "secure_random.h"
@@ -215,6 +218,23 @@ void app_main(void)
                  "Stored Wi-Fi configuration is incompatible; using RAM defaults without overwriting it");
     }
 
+    mdns_config_t mdns_config;
+    bool used_stored_mdns_config = false;
+    esp_err_t mdns_config_error = mdns_config_load(&mdns_config, &used_stored_mdns_config);
+    if (mdns_config_error != ESP_OK) {
+        mdns_config_defaults(&mdns_config);
+        ESP_LOGW(TAG, "NVS mDNS configuration unavailable (%s); using RAM defaults",
+                 esp_err_to_name(mdns_config_error));
+    }
+    esp_err_t mdns_service_error = mdns_service_init(&mdns_config);
+    if (mdns_service_error != ESP_OK) {
+        ESP_LOGW(TAG, "mDNS configuration service unavailable: %s; Wi-Fi will continue",
+                 esp_err_to_name(mdns_service_error));
+    } else {
+        ESP_LOGI(TAG, "Using %s mDNS suffix sak-%s.local",
+                 used_stored_mdns_config ? "stored" : "default", mdns_config.suffix);
+    }
+
     esp_err_t wifi_error = wifi_config_error;
     if (wifi_config_error == ESP_OK) {
         wifi_error = wifi_manager_init(&wifi_config);
@@ -301,6 +321,9 @@ void app_main(void)
     ESP_ERROR_CHECK(usb_console_register_commands());
     ESP_ERROR_CHECK(user_console_register_commands());
     ESP_ERROR_CHECK(wifi_console_register_commands());
+    if (mdns_service_error == ESP_OK) {
+        ESP_ERROR_CHECK(mdns_console_register_commands());
+    }
     ESP_ERROR_CHECK(web_console_register_commands());
     ESP_ERROR_CHECK(ssh_console_register_commands());
     ESP_ERROR_CHECK(network_console_register_root_commands());

src/mdns_config.c

@@ -0,0 +1,145 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* Versioned persistent configuration for the station mDNS hostname. */
+
+#include "mdns_config.h"
+
+#include <stddef.h>
+#include <string.h>
+
+#include "esp_mac.h"
+#include "nvs.h"
+#include "nvs_flash.h"
+
+_Static_assert(sizeof(mdns_config_t) == MDNS_CONFIG_BLOB_SIZE,
+               "mDNS config schema size changed");
+
+static bool suffix_character_is_valid(char character)
+{
+    return (character >= 'a' && character <= 'z') ||
+           (character >= '0' && character <= '9') || character == '-';
+}
+
+void mdns_config_defaults(mdns_config_t *config)
+{
+    static const char hex[] = "0123456789abcdef";
+    uint8_t mac[6] = {0};
+
+    if (config == NULL) {
+        return;
+    }
+
+    memset(config, 0, sizeof(*config));
+    config->schema_version = MDNS_CONFIG_SCHEMA_VERSION;
+    config->blob_size = MDNS_CONFIG_BLOB_SIZE;
+    if (esp_read_mac(mac, ESP_MAC_WIFI_STA) != ESP_OK) {
+        return;
+    }
+    for (size_t index = 0U; index < sizeof(mac); ++index) {
+        config->suffix[index * 2U] = hex[mac[index] >> 4U];
+        config->suffix[index * 2U + 1U] = hex[mac[index] & 0x0fU];
+    }
+    config->suffix_len = sizeof(mac) * 2U;
+}
+
+esp_err_t mdns_config_validate(const mdns_config_t *config)
+{
+    if (config == NULL || config->schema_version != MDNS_CONFIG_SCHEMA_VERSION ||
+        config->blob_size != MDNS_CONFIG_BLOB_SIZE || config->suffix_len == 0U ||
+        config->suffix_len > MDNS_CONFIG_SUFFIX_MAX_LEN || config->reserved != 0U ||
+        config->suffix[config->suffix_len] != '\0') {
+        return ESP_ERR_INVALID_ARG;
+    }
+    if (config->suffix[0] == '-' || config->suffix[config->suffix_len - 1U] == '-') {
+        return ESP_ERR_INVALID_ARG;
+    }
+    for (size_t index = 0U; index < MDNS_CONFIG_SUFFIX_MAX_LEN; ++index) {
+        if (index < config->suffix_len) {
+            if (!suffix_character_is_valid(config->suffix[index])) {
+                return ESP_ERR_INVALID_ARG;
+            }
+        } else if (config->suffix[index] != '\0') {
+            return ESP_ERR_INVALID_ARG;
+        }
+    }
+    return ESP_OK;
+}
+
+esp_err_t mdns_config_load(mdns_config_t *config, bool *used_stored_config)
+{
+    if (config == NULL || used_stored_config == NULL) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    mdns_config_defaults(config);
+    *used_stored_config = false;
+    if (mdns_config_validate(config) != ESP_OK) {
+        return ESP_FAIL;
+    }
+
+    esp_err_t error = nvs_flash_init();
+    if (error != ESP_OK) {
+        return error;
+    }
+    nvs_handle_t handle;
+    error = nvs_open(MDNS_CONFIG_NVS_NAMESPACE, NVS_READONLY, &handle);
+    if (error == ESP_ERR_NVS_NOT_FOUND) {
+        return ESP_OK;
+    }
+    if (error != ESP_OK) {
+        return error;
+    }
+    size_t size = 0U;
+    error = nvs_get_blob(handle, MDNS_CONFIG_NVS_BLOB_KEY, NULL, &size);
+    if (error == ESP_ERR_NVS_NOT_FOUND || error == ESP_ERR_NVS_TYPE_MISMATCH ||
+        (error == ESP_OK && size != sizeof(*config))) {
+        nvs_close(handle);
+        return ESP_OK;
+    }
+    if (error != ESP_OK) {
+        nvs_close(handle);
+        return error;
+    }
+    mdns_config_t stored = {0};
+    error = nvs_get_blob(handle, MDNS_CONFIG_NVS_BLOB_KEY, &stored, &size);
+    nvs_close(handle);
+    if (error == ESP_ERR_NVS_INVALID_LENGTH) {
+        return ESP_OK;
+    }
+    if (error != ESP_OK) {
+        return error;
+    }
+    if (size == sizeof(stored) && mdns_config_validate(&stored) == ESP_OK) {
+        *config = stored;
+        *used_stored_config = true;
+    }
+    return ESP_OK;
+}
+
+esp_err_t mdns_config_save(const mdns_config_t *config)
+{
+    esp_err_t error = mdns_config_validate(config);
+    if (error != ESP_OK) {
+        return error;
+    }
+    error = nvs_flash_init();
+    if (error != ESP_OK) {
+        return error;
+    }
+    nvs_handle_t handle;
+    error = nvs_open(MDNS_CONFIG_NVS_NAMESPACE, NVS_READWRITE, &handle);
+    if (error != ESP_OK) {
+        return error;
+    }
+    error = nvs_set_blob(handle, MDNS_CONFIG_NVS_BLOB_KEY, config, sizeof(*config));
+    if (error == ESP_OK) {
+        error = nvs_commit(handle);
+    }
+    nvs_close(handle);
+    return error;
+}
+
+esp_err_t mdns_config_reset_storage(void)
+{
+    mdns_config_t config;
+    mdns_config_defaults(&config);
+    return mdns_config_save(&config);
+}

src/mdns_config.h

@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* Versioned persistent configuration for the station mDNS hostname. */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "esp_err.h"
+
+#define MDNS_CONFIG_SCHEMA_VERSION 1U
+#define MDNS_CONFIG_BLOB_SIZE 64U
+#define MDNS_CONFIG_SUFFIX_MAX_LEN 55U
+#define MDNS_CONFIG_NVS_NAMESPACE "mdns_cfg"
+#define MDNS_CONFIG_NVS_BLOB_KEY "config"
+
+typedef struct {
+    uint32_t schema_version;
+    uint16_t blob_size;
+    uint8_t suffix_len;
+    uint8_t reserved;
+    char suffix[MDNS_CONFIG_SUFFIX_MAX_LEN + 1U];
+} mdns_config_t;
+
+void mdns_config_defaults(mdns_config_t *config);
+esp_err_t mdns_config_validate(const mdns_config_t *config);
+esp_err_t mdns_config_load(mdns_config_t *config, bool *used_stored_config);
+esp_err_t mdns_config_save(const mdns_config_t *config);
+esp_err_t mdns_config_reset_storage(void);

src/mdns_console.c

@@ -0,0 +1,149 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* Administration console for the station mDNS hostname. */
+
+#include "mdns_console.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include "esp_console.h"
+#include "mdns_config.h"
+#include "mdns_service.h"
+#include "wifi_manager.h"
+
+static void print_usage(void)
+{
+    printf("Usage: mdns status|suffix <lowercase-suffix>|save|load|defaults|reset\n");
+}
+
+static int request_reannounce(void)
+{
+    esp_err_t error = wifi_manager_mdns_reannounce();
+    if (error != ESP_OK) {
+        printf("mDNS configuration updated; it will be used when Wi-Fi STA receives an IP (%s).\n",
+               esp_err_to_name(error));
+    }
+    return 0;
+}
+
+static int show_status(void)
+{
+    mdns_service_snapshot_t snapshot;
+    esp_err_t error = mdns_service_get_snapshot(&snapshot);
+    if (error != ESP_OK) {
+        printf("mDNS unavailable: %s\n", esp_err_to_name(error));
+        return 1;
+    }
+    printf("mDNS: initialized=%s announced=%s hostname=%s.local suffix=%s last-error=%s\n",
+           snapshot.initialized ? "yes" : "no", snapshot.announced ? "yes" : "no",
+           snapshot.hostname, snapshot.suffix, esp_err_to_name(snapshot.last_error));
+    return 0;
+}
+
+static int set_suffix(const char *suffix)
+{
+    size_t length = strlen(suffix);
+    mdns_config_t config;
+    esp_err_t error = mdns_service_get_config(&config);
+    if (error == ESP_OK) {
+        memset(config.suffix, 0, sizeof(config.suffix));
+        if (length <= MDNS_CONFIG_SUFFIX_MAX_LEN) {
+            memcpy(config.suffix, suffix, length);
+            config.suffix_len = (uint8_t)length;
+            error = mdns_service_set_config(&config);
+        } else {
+            error = ESP_ERR_INVALID_ARG;
+        }
+    }
+    if (error != ESP_OK) {
+        printf("Suffix must be 1..%u lowercase letters, digits, or hyphens, and cannot begin or end with a hyphen.\n",
+               MDNS_CONFIG_SUFFIX_MAX_LEN);
+        return 1;
+    }
+    printf("mDNS suffix updated in RAM; hostname is sak-%s.local; use 'mdns save' to persist it.\n",
+           suffix);
+    return request_reannounce();
+}
+
+static int save_config(void)
+{
+    mdns_config_t config;
+    esp_err_t error = mdns_service_get_config(&config);
+    if (error == ESP_OK) {
+        error = mdns_config_save(&config);
+    }
+    if (error != ESP_OK) {
+        printf("Could not save mDNS configuration: %s\n", esp_err_to_name(error));
+        return 1;
+    }
+    printf("mDNS configuration saved to NVS.\n");
+    return 0;
+}
+
+static int load_config(void)
+{
+    mdns_config_t config;
+    bool stored = false;
+    esp_err_t error = mdns_config_load(&config, &stored);
+    if (error == ESP_OK) {
+        error = mdns_service_set_config(&config);
+    }
+    if (error != ESP_OK) {
+        printf("Could not load mDNS configuration: %s\n", esp_err_to_name(error));
+        return 1;
+    }
+    printf("Loaded %s mDNS configuration into RAM.\n", stored ? "stored" : "default");
+    return request_reannounce();
+}
+
+static int apply_defaults(bool persist)
+{
+    mdns_config_t config;
+    mdns_config_defaults(&config);
+    esp_err_t error = mdns_service_set_config(&config);
+    if (error == ESP_OK && persist) {
+        error = mdns_config_save(&config);
+    }
+    if (error != ESP_OK) {
+        printf("Could not apply mDNS defaults: %s\n", esp_err_to_name(error));
+        return 1;
+    }
+    printf("MAC-derived mDNS defaults applied%s.\n", persist ? " and saved" : " in RAM");
+    return request_reannounce();
+}
+
+static int command_mdns(int argc, char **argv)
+{
+    if (argc == 1 || (argc == 2 && strcmp(argv[1], "status") == 0)) {
+        return show_status();
+    }
+    if (argc == 3 && strcmp(argv[1], "suffix") == 0) {
+        return set_suffix(argv[2]);
+    }
+    if (argc == 2 && strcmp(argv[1], "save") == 0) {
+        return save_config();
+    }
+    if (argc == 2 && strcmp(argv[1], "load") == 0) {
+        return load_config();
+    }
+    if (argc == 2 && strcmp(argv[1], "defaults") == 0) {
+        return apply_defaults(false);
+    }
+    if (argc == 2 && strcmp(argv[1], "reset") == 0) {
+        return apply_defaults(true);
+    }
+    print_usage();
+    return 1;
+}
+
+esp_err_t mdns_console_register_commands(void)
+{
+    const esp_console_cmd_t command = {
+        .command = "mdns",
+        .help = "Configure the STA mDNS hostname; use 'mdns' for status",
+        .hint = NULL,
+        .func = &command_mdns,
+        .argtable = NULL,
+    };
+    return esp_console_cmd_register(&command);
+}

src/mdns_console.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+#pragma once
+
+#include "esp_err.h"
+
+esp_err_t mdns_console_register_commands(void);

src/mdns_service.c

@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* mDNS runtime service; its lifecycle is owned by wifi_manager. */
+
+#include "mdns_service.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/semphr.h"
+#include "mdns.h"
+
+static SemaphoreHandle_t s_mutex;
+static mdns_config_t s_config;
+static bool s_announced;
+static esp_err_t s_last_error;
+
+static void lock_service(void)
+{
+    (void)xSemaphoreTake(s_mutex, portMAX_DELAY);
+}
+
+static void unlock_service(void)
+{
+    (void)xSemaphoreGive(s_mutex);
+}
+
+static void make_hostname(const mdns_config_t *config, char *hostname, size_t size)
+{
+    (void)snprintf(hostname, size, "sak-%s", config->suffix);
+}
+
+esp_err_t mdns_service_init(const mdns_config_t *config)
+{
+    if (mdns_config_validate(config) != ESP_OK) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    if (s_mutex != NULL) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    s_mutex = xSemaphoreCreateMutex();
+    if (s_mutex == NULL) {
+        return ESP_ERR_NO_MEM;
+    }
+    s_config = *config;
+    s_last_error = ESP_OK;
+    return ESP_OK;
+}
+
+esp_err_t mdns_service_get_config(mdns_config_t *config)
+{
+    if (config == NULL || s_mutex == NULL) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    lock_service();
+    *config = s_config;
+    unlock_service();
+    return ESP_OK;
+}
+
+esp_err_t mdns_service_set_config(const mdns_config_t *config)
+{
+    if (s_mutex == NULL || mdns_config_validate(config) != ESP_OK) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    lock_service();
+    s_config = *config;
+    unlock_service();
+    return ESP_OK;
+}
+
+esp_err_t mdns_service_get_snapshot(mdns_service_snapshot_t *snapshot)
+{
+    if (snapshot == NULL || s_mutex == NULL) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    lock_service();
+    memset(snapshot, 0, sizeof(*snapshot));
+    snapshot->initialized = true;
+    snapshot->announced = s_announced;
+    memcpy(snapshot->suffix, s_config.suffix, s_config.suffix_len);
+    make_hostname(&s_config, snapshot->hostname, sizeof(snapshot->hostname));
+    snapshot->last_error = s_last_error;
+    unlock_service();
+    return ESP_OK;
+}
+
+esp_err_t mdns_service_start(void)
+{
+    if (s_mutex == NULL) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    lock_service();
+    if (s_announced) {
+        unlock_service();
+        return ESP_OK;
+    }
+    mdns_config_t config = s_config;
+    unlock_service();
+
+    esp_err_t error = mdns_init();
+    if (error == ESP_OK) {
+        char hostname[MDNS_CONFIG_SUFFIX_MAX_LEN + 5U] = {0};
+        make_hostname(&config, hostname, sizeof(hostname));
+        error = mdns_hostname_set(hostname);
+        if (error == ESP_OK) {
+            error = mdns_instance_name_set("ESP32 Serial Swiss Army Knife");
+        }
+        if (error != ESP_OK) {
+            mdns_free();
+        }
+    }
+
+    lock_service();
+    s_announced = error == ESP_OK;
+    s_last_error = error;
+    unlock_service();
+    return error;
+}
+
+void mdns_service_stop(void)
+{
+    if (s_mutex == NULL) {
+        return;
+    }
+    lock_service();
+    bool announced = s_announced;
+    s_announced = false;
+    unlock_service();
+    if (announced) {
+        mdns_free();
+    }
+}

src/mdns_service.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-3.0-only */
+/* mDNS runtime service; its lifecycle is owned by wifi_manager. */
+
+#pragma once
+
+#include <stdbool.h>
+
+#include "esp_err.h"
+#include "mdns_config.h"
+
+typedef struct {
+    bool initialized;
+    bool announced;
+    char suffix[MDNS_CONFIG_SUFFIX_MAX_LEN + 1U];
+    char hostname[MDNS_CONFIG_SUFFIX_MAX_LEN + 5U];
+    esp_err_t last_error;
+} mdns_service_snapshot_t;
+
+esp_err_t mdns_service_init(const mdns_config_t *config);
+esp_err_t mdns_service_get_config(mdns_config_t *config);
+esp_err_t mdns_service_set_config(const mdns_config_t *config);
+esp_err_t mdns_service_get_snapshot(mdns_service_snapshot_t *snapshot);
+
+/* Only wifi_manager may call these lifecycle operations. */
+esp_err_t mdns_service_start(void);
+void mdns_service_stop(void);

src/wifi_manager.c

@@ -17,6 +17,7 @@
 #include "freertos/queue.h"
 #include "freertos/semphr.h"
 #include "freertos/task.h"
+#include "mdns_service.h"
 
 #define WIFI_MANAGER_QUEUE_LENGTH 16U
 #define WIFI_MANAGER_TASK_STACK_SIZE 6144U
@@ -35,6 +36,7 @@ typedef enum {
     MESSAGE_COMMAND_APPLY,
     MESSAGE_COMMAND_RECONNECT,
     MESSAGE_COMMAND_NEXT_PROFILE,
+    MESSAGE_COMMAND_MDNS_REANNOUNCE,
     MESSAGE_STA_CONNECTED,
     MESSAGE_STA_DISCONNECTED,
     MESSAGE_STA_GOT_IP,
@@ -109,6 +111,15 @@ static void manager_task(void *context);
 static void start_profile_cycle(manager_runtime_t *runtime);
 static void start_next_profile(manager_runtime_t *runtime);
 
+static void start_mdns_announcement(void)
+{
+    esp_err_t error = mdns_service_start();
+    if (error != ESP_OK) {
+        /* Name discovery is optional; never make network or serial recovery depend on it. */
+        ESP_LOGW(TAG, "mDNS announcement unavailable: %s", esp_err_to_name(error));
+    }
+}
+
 static void lock_shared(void)
 {
     (void)xSemaphoreTake(s_mutex, portMAX_DELAY);
@@ -410,6 +421,7 @@ static void mark_intentional_disconnect(manager_runtime_t *runtime)
 
 static void stop_radio(manager_runtime_t *runtime)
 {
+    mdns_service_stop();
     if (!runtime->radio_started) {
         return;
     }
@@ -744,6 +756,7 @@ static void handle_got_ip(manager_runtime_t *runtime,
     unlock_shared();
 
     wifi_config_secure_wipe(&config, sizeof(config));
+    start_mdns_announcement();
 }
 
 static void handle_sta_disconnected(manager_runtime_t *runtime,
@@ -764,6 +777,7 @@ static void handle_sta_disconnected(manager_runtime_t *runtime,
     bool had_attempt = runtime->attempt_deadline != 0;
     bool was_online = runtime->online;
 
+    mdns_service_stop();
     runtime->associated = false;
     runtime->online = false;
     runtime->attempt_deadline = 0;
@@ -868,6 +882,13 @@ static void handle_message(manager_runtime_t *runtime,
         }
         break;
 
+    case MESSAGE_COMMAND_MDNS_REANNOUNCE:
+        if (runtime->online) {
+            mdns_service_stop();
+            start_mdns_announcement();
+        }
+        break;
+
     case MESSAGE_STA_CONNECTED:
         if (!manager_is_started() ||
             !connected_event_matches_active_profile(message)) {
@@ -900,6 +921,7 @@ static void handle_message(manager_runtime_t *runtime,
                 /* Ignore a delayed loss event after a newer DHCP lease. */
                 break;
             }
+            mdns_service_stop();
             runtime->online = false;
             runtime->stable_deadline = 0;
             runtime->attempt_deadline = esp_timer_get_time() + WIFI_MANAGER_ATTEMPT_US;
@@ -1465,6 +1487,11 @@ esp_err_t wifi_manager_next_profile(void)
     return enqueue_lifecycle_command(MESSAGE_COMMAND_NEXT_PROFILE, -1);
 }
 
+esp_err_t wifi_manager_mdns_reannounce(void)
+{
+    return enqueue_lifecycle_command(MESSAGE_COMMAND_MDNS_REANNOUNCE, -1);
+}
+
 esp_err_t wifi_manager_get_snapshot(wifi_manager_snapshot_t *snapshot)
 {
     if (snapshot == NULL) {

src/wifi_manager.h

@@ -95,6 +95,8 @@ esp_err_t wifi_manager_stop(void);
 esp_err_t wifi_manager_reconnect(void);
 /* Advance to the next enabled station profile in priority order, wrapping safely. */
 esp_err_t wifi_manager_next_profile(void);
+/* Reannounce the configured hostname when the manager currently has a STA IP. */
+esp_err_t wifi_manager_mdns_reannounce(void);
 
 /* Snapshot data never contains station or AP passwords. */
 esp_err_t wifi_manager_get_snapshot(wifi_manager_snapshot_t *snapshot);