From 64d3c7646c32e0c568781eb6900c8377260c9576 Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Wed, 30 Jul 2025 11:17:42 -0400
Subject: [PATCH] MT#63317 parse out RTP header extensions

Stub function for now.

Change-Id: I7ad2a203f42fb118e50273a57772cac4fbd1738f
---
 daemon/media_socket.c  | 23 ++++++++++++-
 include/media_socket.h |  1 +
 lib/rtplib.c           | 74 ++++++++++++++++++++++++++++++++++++++++++
 lib/rtplib.h           |  7 ++++
 4 files changed, 104 insertions(+), 1 deletion(-)

diff --git a/daemon/media_socket.c b/daemon/media_socket.c
index b1fba6f51..fff1916f0 100644
--- a/daemon/media_socket.c
+++ b/daemon/media_socket.c
@@ -2304,7 +2304,7 @@ static void media_packet_parse(struct packet_handler_ctx *phc) {
 		return;
 
 	if (!phc->rtcp) {
-		phc->mp.rtp = rtp_payload(&phc->mp.payload, &phc->s, NULL);
+		phc->mp.rtp = rtp_payload(&phc->mp.payload, &phc->s, &phc->mp.extensions);
 		if (G_LIKELY(phc->mp.rtp)) {
 			// check the payload type
 			// XXX redundant between SSRC handling and codec_handler stuff -> combine
@@ -2346,6 +2346,24 @@ static void media_packet_rtcp_mux(struct packet_handler_ctx *phc, struct sink_ha
 }
 
 
+static void media_packet_rtp_extension(struct packet_handler_ctx *phc, unsigned int id, const str *data) {
+	__auto_type ext = phc->mp.media->extmap_lookup(phc->mp.media, id);
+	if (!ext)
+		return;
+
+	// stub
+}
+
+static void media_packet_rtp_extensions(struct packet_handler_ctx *phc) {
+	if (!phc->mp.media->extmap.length)
+		return;
+	if (!phc->mp.extensions.len)
+		return;
+
+	rtp_rfc8285_iterate(&phc->mp.extensions, media_packet_rtp_extension, phc);
+}
+
+
 // sets ssrc_in and tracks stats
 static void media_packet_rtp_in(struct packet_handler_ctx *phc) {
 	if (G_UNLIKELY(!phc->mp.media))
@@ -2381,6 +2399,8 @@ static void media_packet_rtp_in(struct packet_handler_ctx *phc) {
 			atomic64_add(&rtp_s->bytes, phc->s.len);
 			g_atomic_pointer_set(&phc->mp.stream->rtp_stats_cache, rtp_s);
 		}
+
+		media_packet_rtp_extensions(phc);
 	}
 	else if (phc->rtcp) {
 		unkern = __stream_ssrc_in(phc->in_srtp, phc->mp.rtcp->ssrc, &phc->mp.ssrc_in,
@@ -2775,6 +2795,7 @@ void media_packet_copy(struct media_packet *dst, const struct media_packet *src)
 	dst->rtcp = __g_memdup(src->rtcp, sizeof(*src->rtcp));
 	dst->payload = STR_NULL;
 	dst->raw = STR_NULL;
+	dst->extensions = STR_NULL;
 }
 void media_packet_release(struct media_packet *mp) {
 	if (mp->sfd)
diff --git a/include/media_socket.h b/include/media_socket.h
index bd8808022..8a2d20de1 100644
--- a/include/media_socket.h
+++ b/include/media_socket.h
@@ -281,6 +281,7 @@ struct media_packet {
 	struct rtcp_packet *rtcp;
 	struct ssrc_entry_call *ssrc_in, *ssrc_out; // SSRC contexts from in_srtp and out_srtp
 	str payload;
+	str extensions;
 
 	codec_packet_q packets_out;
 	int ptime; // returned from decoding
diff --git a/lib/rtplib.c b/lib/rtplib.c
index 3f506d15c..72003e53e 100644
--- a/lib/rtplib.c
+++ b/lib/rtplib.c
@@ -11,6 +11,17 @@ struct rtp_exthdr {
 	uint16_t length;
 } __attribute__ ((packed));
 
+struct rtp_rfc8285_hdr {
+	uint8_t be;
+	uint8_t de;
+	uint16_t length;
+} __attribute__ ((packed));
+
+struct rtp_rfc8285_item {
+	uint8_t id;
+	uint8_t length;
+} __attribute__ ((packed));
+
 
 
 
@@ -55,8 +66,71 @@ const struct rtp_payload_type rfc_rtp_payload_types[] =
 const int num_rfc_rtp_payload_types = G_N_ELEMENTS(rfc_rtp_payload_types);
 
 
+static void rtp_rfc8285_iterate_short(str s, const struct rtp_rfc8285_hdr *hdr,
+		rtp_rfc8285_handler cb, struct packet_handler_ctx *arg)
+{
+	str_shift(&s, sizeof(*hdr));
+
+	while (s.len) {
+		uint8_t id_len = s.s[0];
+		if (id_len == '\0') {
+			// padding
+			str_shift(&s, 1);
+			continue;
+		}
+		uint8_t id = id_len >> 4;
+		uint8_t len = (id_len & 0xf) + 1;
+		str_shift(&s, 1);
+
+		if (s.len < len)
+			return;
+
+		cb(arg, id, &STR_LEN(s.s, len));
+
+		str_shift(&s, len);
+	}
+}
+
+static void rtp_rfc8285_iterate_long(str s, const struct rtp_rfc8285_hdr *hdr,
+		rtp_rfc8285_handler cb, struct packet_handler_ctx *arg)
+{
+	str_shift(&s, sizeof(*hdr));
+
+	struct rtp_rfc8285_item *item;
+
+	while (s.len >= sizeof(*item)) {
+		if (s.s[0] == '\0') {
+			// padding
+			str_shift(&s, 1);
+			continue;
+		}
+
+		item = (struct rtp_rfc8285_item *) s.s;
+
+		str_shift(&s, sizeof(*item));
+
+		if (s.len < item->length)
+			return;
 
+		cb(arg, item->id, &STR_LEN(s.s, item->length));
 
+		str_shift(&s, item->length);
+	}
+}
+
+void rtp_rfc8285_iterate(const str *extensions, rtp_rfc8285_handler cb, struct packet_handler_ctx *arg) {
+	const struct rtp_rfc8285_hdr *hdr;
+
+	if (extensions->len < sizeof(*hdr))
+		return;
+
+	hdr = (struct rtp_rfc8285_hdr *) extensions->s;
+
+	if (hdr->be == 0xbe && hdr->de == 0xde)
+		rtp_rfc8285_iterate_short(*extensions, hdr, cb, arg);
+	else if (hdr->be == 0x10 && (hdr->de & 0xf0) == 0x00)
+		rtp_rfc8285_iterate_long(*extensions, hdr, cb, arg);
+}
 
 
 struct rtp_header *rtp_payload(str *p, const str *s, str *exts) {
diff --git a/lib/rtplib.h b/lib/rtplib.h
index 8d9e9a4b8..c554771bb 100644
--- a/lib/rtplib.h
+++ b/lib/rtplib.h
@@ -131,6 +131,13 @@ __attribute__((nonnull(2)))
 struct rtp_header *rtp_payload(str *p, const str *s, str *ext);
 __attribute__((nonnull(2)))
 bool rtp_padding(const struct rtp_header *header, str *payload);
+
+struct packet_handler_ctx;
+
+typedef void (*rtp_rfc8285_handler)(struct packet_handler_ctx *, unsigned int, const str *);
+void rtp_rfc8285_iterate(const str *, rtp_rfc8285_handler, struct packet_handler_ctx *);
+
+
 const struct rtp_payload_type *rtp_get_rfc_payload_type(unsigned int type);
 const struct rtp_payload_type *rtp_get_rfc_codec(const str *codec);