From 7c8453f2602f2d6b44dbd1fbf4ff1963882175c9 Mon Sep 17 00:00:00 2001
From: Arun Raghavan <arun@asymptotic.io>
Date: Thu, 4 Jul 2024 13:13:37 -0400
Subject: [PATCH] module-rtp: Allow overriding session ID

This allows us to specify a static session ID, so that (Dante) receivers
can uniquely identify us as a sender. This prevents duplicate streams in
Dante Controller, for example.
---
 src/modules/module-rtp-sap.c  | 17 +++++++++++++----
 src/modules/module-rtp-sink.c |  1 +
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/modules/module-rtp-sap.c b/src/modules/module-rtp-sap.c
index ab31d7f73..a085b4f85 100644
--- a/src/modules/module-rtp-sap.c
+++ b/src/modules/module-rtp-sap.c
@@ -179,7 +179,7 @@ static const struct spa_dict_item module_info[] = {
 
 struct sdp_info {
 	uint16_t hash;
-	uint32_t ntp;
+	uint32_t session_id;
 	uint32_t t_ntp;
 
 	char *origin;
@@ -692,7 +692,7 @@ static int send_sap(struct impl *impl, struct session *sess, bool bye)
 			"c=IN %s %s%s\n"
 			"t=%u 0\n"
 			"m=%s %u RTP/AVP %i\n",
-			user_name, sdp->ntp, src_ip4 ? "IP4" : "IP6", src_addr,
+			user_name, sdp->session_id, src_ip4 ? "IP4" : "IP6", src_addr,
 			sdp->session_name,
 			dst_ip4 ? "IP4" : "IP6", dst_addr, dst_ttl,
 			sdp->t_ntp,
@@ -854,8 +854,17 @@ static struct session *session_new_announce(struct impl *impl, struct node *node
 	sess->announce = true;
 
 	sdp->hash = pw_rand32();
-	sdp->ntp = (uint32_t) time(NULL) + 2208988800U + impl->n_sessions;
-	sdp->t_ntp = pw_properties_get_uint32(props, "rtp.ntp", sdp->ntp);
+	if ((str = pw_properties_get(props, "sess.id")) != NULL) {
+		if (!spa_atou32(str, &sdp->session_id, 10)) {
+			pw_log_error("Invalid session id: %s (must be a uint32)", str);
+			goto error_free;
+		}
+		sdp->t_ntp = pw_properties_get_uint32(props, "rtp.ntp",
+				(uint32_t) time(NULL) + 2208988800U + impl->n_sessions);
+	} else {
+		sdp->session_id = (uint32_t) time(NULL) + 2208988800U + impl->n_sessions;
+		sdp->t_ntp = pw_properties_get_uint32(props, "rtp.ntp", sdp->session_id);
+	}
 	sess->props = props;
 
 	if ((str = pw_properties_get(props, "sess.name")) == NULL)
diff --git a/src/modules/module-rtp-sink.c b/src/modules/module-rtp-sink.c
index 44f754843..696be239f 100644
--- a/src/modules/module-rtp-sink.c
+++ b/src/modules/module-rtp-sink.c
@@ -529,6 +529,7 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 	copy_props(impl, props, "net.mtu");
 	copy_props(impl, props, "sess.media");
 	copy_props(impl, props, "sess.name");
+	copy_props(impl, props, "sess.id");
 	copy_props(impl, props, "sess.min-ptime");
 	copy_props(impl, props, "sess.max-ptime");
 	copy_props(impl, props, "sess.latency.msec");