Step 2a (1/2): mDNS hostname.local and _http._tcp

- aes67_net: espressif/mdns 1.13.1 (managed component, pinned in
  dependencies.lock). Advertises <net.hostname>.local and the web UI as
  _http._tcp port 80. net apply callback renames live.
- First config value actually applied: net.hostname.
- Docs: mDNS in the core Network section; build order gets step 2a
  (mDNS, then LLDP).
- Verified on board: p4-aes67.local resolves via raw mDNS and getent,
  http://p4-aes67.local/ answers, service shows in _http._tcp browse;
  live rename to p4-rename and back works (after ~1 s probing).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -37,6 +37,7 @@ Repo: https://gitea.apointless.space/bsncubed/aes67-ESP32-P4
 - [x] 0. Check chip revision and flash size; create IDF project and empty component stubs (layout in aes67-core-base.md). Set up the OTA partition table (two app slots, no factory) and PROJECT_VER from git now, so the layout never changes later.
 - [x] 1. Ethernet: IP101 up, DHCP, IP logged. Ping works.
 - [x] 2. Web server + config store (cJSON in NVS) + embedded index.html; /api/config, /api/status (stub values), /api/reboot.
+- [ ] 2a. Finding the device: mDNS (hostname.local + _http._tcp), then LLDP (switch shows name + IP).
 - [ ] 2b. Firmware update: /api/ota upload + rollback self-test. Test: update to a new build, then deliberately flash a build that fails its self-test and confirm it rolls back. After this, flash over the network; keep USB for recovery.
 - [ ] 3. PTP TimeReceiver: lock to an existing GM (Riedel), fill `status.ptp`. Confirm EMAC hardware timestamps work. First check whether the installed ESP-IDF has a PTP example/component for the P4 before writing one.
 - [ ] 4. AES67 TX with a 1 kHz test tone, PTP-paced; /stream.sdp. Verify: import SDP on a Riedel Artist 4-wire AES67 port, and check packets/timestamps in Wireshark.

components/aes67_net/CMakeLists.txt

@@ -1,4 +1,4 @@
 idf_component_register(SRCS "aes67_net.c"
                        INCLUDE_DIRS "include"
                        REQUIRES esp_eth esp_netif esp_event
-                       PRIV_REQUIRES aes67_web lwip)
+                       PRIV_REQUIRES aes67_web lwip espressif__mdns)

components/aes67_net/aes67_net.c

@@ -10,6 +10,7 @@
 #include "esp_event.h"
 #include "esp_log.h"
 #include "esp_netif.h"
+#include "mdns.h"
 
 static const char *TAG = "net";
 
@@ -105,6 +106,31 @@ static bool inet_validate(const cJSON *g, char *err, size_t n)
            check_addr(g, err, n);
 }
 
+// mDNS: <hostname>.local plus the web UI as _http._tcp.
+static void mdns_setup(void)
+{
+    cJSON *net = cfg_get("net");
+    const char *host = cJSON_GetObjectItemCaseSensitive(net, "hostname")->valuestring;
+    esp_err_t err = mdns_init();
+    if (err == ESP_OK) {
+        mdns_hostname_set(host);
+        mdns_instance_name_set(host);
+        mdns_service_add(NULL, "_http", "_tcp", 80, NULL, 0);
+        ESP_LOGI(TAG, "mDNS: %s.local, _http._tcp port 80", host);
+    } else {
+        ESP_LOGE(TAG, "mDNS init failed: %s", esp_err_to_name(err));
+    }
+    cJSON_Delete(net);
+}
+
+static void net_apply(const cJSON *g)
+{
+    const char *host = cJSON_GetObjectItemCaseSensitive(g, "hostname")->valuestring;
+    if (mdns_hostname_set(host) == ESP_OK && mdns_instance_name_set(host) == ESP_OK) {
+        ESP_LOGI(TAG, "mDNS: now %s.local", host);
+    }
+}
+
 static void net_status(cJSON *st)
 {
     char ip[16] = "", mac_s[18] = "";
@@ -126,8 +152,8 @@ static void net_status(cJSON *st)
 
 esp_err_t aes67_net_init(esp_eth_handle_t eth)
 {
-    // Config is stored only for now; applying it (hostname, static IP, VLAN) comes later.
+    // Applied so far: hostname (mDNS). Static IP and VLAN come later.
-    ESP_ERROR_CHECK(cfg_register("net", NET_DEFAULTS, net_validate, NULL));
+    ESP_ERROR_CHECK(cfg_register("net", NET_DEFAULTS, net_validate, net_apply));
     ESP_ERROR_CHECK(cfg_register("inet", INET_DEFAULTS, inet_validate, NULL));
 
     ESP_ERROR_CHECK(esp_netif_init());
@@ -143,6 +169,7 @@ esp_err_t aes67_net_init(esp_eth_handle_t eth)
     ESP_ERROR_CHECK(esp_event_handler_register(ETH_EVENT, ESP_EVENT_ANY_ID, eth_event, NULL));
     ESP_ERROR_CHECK(esp_event_handler_register(IP_EVENT, IP_EVENT_ETH_GOT_IP, ip_event, NULL));
 
+    mdns_setup();
     status_register(net_status);
     return esp_eth_start(eth);
 }

components/aes67_net/idf_component.yml

@@ -0,0 +1,2 @@
+dependencies:
+  espressif/mdns: "^1.13.1"

dependencies.lock

@@ -0,0 +1,20 @@
+dependencies:
+  espressif/mdns:
+    component_hash: b679eafd0acae2066e2645bd91d073e33ca5be515e2545cd3c4e55a3e3bce3cb
+    dependencies:
+    - name: idf
+      require: private
+      version: '>=5.0'
+    source:
+      registry_url: https://components.espressif.com/
+      type: service
+    version: 1.13.1
+  idf:
+    source:
+      type: idf
+    version: 5.5.5
+direct_dependencies:
+- espressif/mdns
+manifest_hash: e5eba11c864076c14a58153c7f761bec2b064244e66ca3f76c0dc170db907329
+target: esp32p4
+version: 2.0.0

docs/aes67-core-base.md

@@ -91,6 +91,7 @@ When this device is the GM, offset/frequency/delay show "–".
 ## Network
 - Default: one untagged interface. VLAN split option: AES67 untagged + internet tagged (inet.vlan_id/pcp) using the ESP-IDF vlan_support approach (examples/network/vlan_support, ESP32-P4 supported). AES67 side has no gateway; default route and DNS are on inet.
 - PTP, RTP, SAP and IGMP bind to the AES67 netif. HTTP server filters on `web_on`.
+- mDNS (espressif/mdns): `<net.hostname>.local` plus the web UI as `_http._tcp` port 80. A hostname change applies live (the new name answers after ~1 s of RFC 6762 probing).
 - Switch port: AES67 as native/untagged VLAN, internet tagged, PoE on. IGMP snooping + querier on the AES67 VLAN.
 
 ## Syslog