Step 4.1: /stream.sdp from the live config and PTP GM

- aes67_sdp_sap: aes67_sdp_build() builds the AES67 SDP (RFC 4566 +
  RFC 7273) with the same lines and order as the web UI preview;
  GET /stream.sdp serves it as application/sdp.
- aes67_ptp: public aes67_ptp_gm_id(), aes67_ptp_locked(),
  aes67_ptp_now_ns(). Clock IDs are now uppercase (RFC 7273 style), also
  in status.ptp, which the UI copies into ts-refclk.
- aes67_net: aes67_net_netif() returns the AES67 interface.
- Verified on board: /stream.sdp byte-identical to the UI's sdp() for
  the same config/status; mono, L16, ptime 0.333, ttl 8, clk_offset
  4294967295 and session_ver all follow the config.

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

components/aes67_net/aes67_net.c

@@ -183,3 +183,8 @@ esp_err_t aes67_net_init(esp_eth_handle_t eth)
     status_register(net_status);
     return esp_eth_start(eth);
 }
+
+esp_netif_t *aes67_net_netif(void)
+{
+    return s_netif;
+}

components/aes67_net/include/aes67_net.h

@@ -4,6 +4,10 @@
 
 #include "esp_err.h"
 #include "esp_eth_driver.h"
+#include "esp_netif.h"
 
 // Attach a netif (DHCP client) to the Ethernet driver and start it. Logs link and IP events.
 esp_err_t aes67_net_init(esp_eth_handle_t eth);
+
+// The AES67 interface (untagged side once the VLAN split exists). NULL before aes67_net_init().
+esp_netif_t *aes67_net_netif(void);

components/aes67_ptp/aes67_ptp.c

@@ -45,3 +45,23 @@ esp_err_t aes67_ptp_start(esp_eth_handle_t eth)
     }
     return err;
 }
+
+bool aes67_ptp_gm_id(char out[24])
+{
+    return ptp_clock_gm_id(out);
+}
+
+bool aes67_ptp_locked(void)
+{
+    return ptp_clock_locked();
+}
+
+esp_err_t aes67_ptp_now_ns(int64_t *ns)
+{
+    eth_mac_time_t t;
+    esp_err_t err = ptp_hw_get_time(&t);
+    if (err == ESP_OK) {
+        *ns = (int64_t)t.seconds * 1000000000LL + t.nanoseconds;
+    }
+    return err;
+}

components/aes67_ptp/include/aes67_ptp.h

@@ -2,6 +2,9 @@
 // Core component: must not depend on main/ (project code).
 #pragma once
 
+#include <stdbool.h>
+#include <stdint.h>
+
 #include "esp_err.h"
 #include "esp_eth_driver.h"
 
@@ -9,3 +12,10 @@
 esp_err_t aes67_ptp_init(void);
 // Start the EMAC PTP clock and the PTP task on this Ethernet interface.
 esp_err_t aes67_ptp_start(esp_eth_handle_t eth);
+
+// Current GM clockIdentity as "XX-XX-XX-XX-XX-XX-XX-XX" (RFC 7273 form). false if none selected.
+bool aes67_ptp_gm_id(char out[24]);
+// Servo locked to the GM.
+bool aes67_ptp_locked(void);
+// PTP time (EMAC hardware clock) in ns.
+esp_err_t aes67_ptp_now_ns(int64_t *ns);

components/aes67_ptp/ptp_clock.c

@@ -150,7 +150,7 @@ static int64_t mac_ns(const eth_mac_time_t *t)
 
 static void fmt_id(char *out, const uint8_t *id)
 {
-    sprintf(out, "%02x-%02x-%02x-%02x-%02x-%02x-%02x-%02x", id[0], id[1], id[2], id[3], id[4], id[5], id[6], id[7]);
+    sprintf(out, "%02X-%02X-%02X-%02X-%02X-%02X-%02X-%02X", id[0], id[1], id[2], id[3], id[4], id[5], id[6], id[7]);
 }
 
 // IEEE 1588 dataset comparison (without the topology part): <0 if a is better.
@@ -487,6 +487,22 @@ static void ptp_task(void *arg)
     }
 }
 
+bool ptp_clock_gm_id(char out[24])
+{
+    xSemaphoreTake(s.lock, portMAX_DELAY);
+    bool valid = s.gm.valid;
+    if (valid) {
+        fmt_id(out, s.gm.gm_id);
+    }
+    xSemaphoreGive(s.lock);
+    return valid;
+}
+
+bool ptp_clock_locked(void)
+{
+    return s.locked;
+}
+
 void ptp_clock_status(cJSON *st)
 {
     cJSON *p = cJSON_AddObjectToObject(st, "ptp");

components/aes67_ptp/ptp_clock.h

@@ -6,5 +6,7 @@
 #include "esp_netif.h"
 
 esp_err_t ptp_clock_start(esp_netif_t *netif);
+bool ptp_clock_gm_id(char out[24]);
+bool ptp_clock_locked(void);
 // Adds the "ptp" object to /api/status.
 void ptp_clock_status(cJSON *st);

components/aes67_sdp_sap/CMakeLists.txt

@@ -1,2 +1,3 @@
 idf_component_register(SRCS "aes67_sdp_sap.c"
-                       INCLUDE_DIRS "include")
+                       INCLUDE_DIRS "include"
+                       PRIV_REQUIRES aes67_net aes67_ptp aes67_web esp_netif)

components/aes67_sdp_sap/aes67_sdp_sap.c

@@ -1,7 +1,89 @@
 #include "aes67_sdp_sap.h"
 
-// Stub (build step 0).
+#include <stdio.h>
+#include <string.h>
+
+#include "aes67_cfg.h"
+#include "aes67_net.h"
+#include "aes67_ptp.h"
+#include "aes67_web.h"
+#include "esp_netif.h"
+
+#define SDP_MAX 1024
+
+// Same lines, in the same order, as the SDP preview in web/index.html.
+size_t aes67_sdp_build(char *buf, size_t size)
+{
+    cJSON *a = cfg_get("aes67");
+    cJSON *p = cfg_get("ptp");
+    if (!a || !p) {
+        cJSON_Delete(a);
+        cJSON_Delete(p);
+        return 0;
+    }
+#define NUM(o, k) cJSON_GetObjectItemCaseSensitive(o, k)->valuedouble
+#define STR(o, k) cJSON_GetObjectItemCaseSensitive(o, k)->valuestring
+    char ip[16] = "0.0.0.0";
+    esp_netif_ip_info_t info;
+    esp_netif_t *netif = aes67_net_netif();
+    if (netif && esp_netif_get_ip_info(netif, &info) == ESP_OK && info.ip.addr) {
+        snprintf(ip, sizeof(ip), IPSTR, IP2STR(&info.ip));
+    }
+    char gm[24];
+    if (!aes67_ptp_gm_id(gm)) {
+        strcpy(gm, "00-00-00-00-00-00-00-00");
+    }
+    int ch = (int)NUM(a, "channels");
+    char info_ch[16];
+    snprintf(info_ch, sizeof(info_ch), ch == 1 ? "mono" : ch == 2 ? "stereo" : "%d ch", ch);
+    int dom = (int)NUM(p, "domain");
+    int pt = (int)NUM(a, "pt");
+
+    int n = snprintf(buf, size,
+                     "v=0\r\n"
+                     "o=- %.0f %.0f IN IP4 %s\r\n"
+                     "s=%s\r\n"
+                     "c=IN IP4 %s/%d\r\n"
+                     "t=0 0\r\n"
+                     "a=clock-domain:PTPv2 %d\r\n"
+                     "m=audio %d RTP/AVP %d\r\n"
+                     "i=%s\r\n"
+                     "a=rtpmap:%d %s/%d/%d\r\n"
+                     "a=recvonly\r\n"
+                     "a=ptime:%g\r\n"
+                     "a=ts-refclk:ptp=IEEE1588-2008:%s:%d\r\n"
+                     "a=mediaclk:direct=%.0f\r\n",
+                     NUM(a, "session_id"), NUM(a, "session_ver"), ip,
+                     STR(a, "name"),
+                     STR(a, "mcast"), (int)NUM(a, "ttl"),
+                     dom,
+                     (int)NUM(a, "port"), pt,
+                     info_ch,
+                     pt, STR(a, "encoding"), (int)NUM(a, "rate"), ch,
+                     NUM(a, "ptime"),
+                     gm, dom,
+                     NUM(a, "clk_offset"));
+#undef NUM
+#undef STR
+    cJSON_Delete(a);
+    cJSON_Delete(p);
+    return n > 0 && (size_t)n < size ? (size_t)n : 0;
+}
+
+static esp_err_t sdp_get(httpd_req_t *req)
+{
+    char buf[SDP_MAX];
+    size_t len = aes67_sdp_build(buf, sizeof(buf));
+    if (!len) {
+        return httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "SDP build failed");
+    }
+    httpd_resp_set_type(req, "application/sdp");
+    httpd_resp_set_hdr(req, "Cache-Control", "no-store");
+    return httpd_resp_send(req, buf, len);
+}
+
 esp_err_t aes67_sdp_sap_init(void)
 {
-    return ESP_OK;
+    static const httpd_uri_t uri = { .uri = "/stream.sdp", .method = HTTP_GET, .handler = sdp_get };
+    return web_register_uri(&uri);
 }

components/aes67_sdp_sap/include/aes67_sdp_sap.h

@@ -2,6 +2,11 @@
 // Core component: must not depend on main/ (project code).
 #pragma once
 
+#include <stddef.h>
+
 #include "esp_err.h"
 
+// Registers GET /stream.sdp. (SAP: step 5.)
 esp_err_t aes67_sdp_sap_init(void);
+// Build the current SDP (RFC 4566 + RFC 7273, AES67). Returns the length, or 0 if it didn't fit.
+size_t aes67_sdp_build(char *buf, size_t size);

main/CMakeLists.txt

@@ -1,5 +1,5 @@
 idf_component_register(SRCS "main.c" "project_cfg.c"
                        INCLUDE_DIRS "."
                        REQUIRES esp_app_format esp_hw_support
-                                aes67_board aes67_health aes67_net aes67_ota aes67_ptp
+                                aes67_board aes67_health aes67_net aes67_ota aes67_ptp aes67_sdp_sap
                                 aes67_syslog aes67_tx aes67_web)

main/main.c

@@ -3,6 +3,7 @@
 #include "aes67_net.h"
 #include "aes67_ota.h"
 #include "aes67_ptp.h"
+#include "aes67_sdp_sap.h"
 #include "aes67_syslog.h"
 #include "aes67_tx.h"
 #include "aes67_web.h"
@@ -36,5 +37,6 @@ void app_main(void)
     ESP_ERROR_CHECK(aes67_syslog_init());
     project_cfg_register();
     ESP_ERROR_CHECK(aes67_ota_init());
+    ESP_ERROR_CHECK(aes67_sdp_sap_init());
     ESP_ERROR_CHECK(aes67_web_start());
 }