rtp_engine: allocate RTP dynamic payloads per session

Dynamic payload types were statically defined in Asterisk. This unfortunately
limited the number of dynamic payloads that could be registered. With this patch
dynamic payload type numbers are now assigned dynamically and per RTP instance.
However, in order to limit any issues where some clients expect the old
statically defined value this patch makes it so the value Asterisk used to pre-
designate is used for the dynamic assignment if available.

An option, "rtp_use_dynamic", has also been added (can be set in asterisk.conf)
that turns the new dynamic behavior on or off. When off it reverts back to using
statically defined payload values. This option defaults to "yes" in Asterisk 15.

ASTERISK-26515 #close
patches:
  ASTERISK-26515.diff submitted by jcolp (license 5000

Change-Id: I7653465c5ebeaf968f1a1cc8f3f4f5c4321da7fc

1 files changed, 159 insertions, 108 deletions

diff --git a/main/rtp_engine.c b/main/rtp_engine.c
index 931f89d7c..00f9d595f 100644
--- a/main/rtp_engine.c
+++ b/main/rtp_engine.c
@@ -266,14 +266,28 @@ static void rtp_payload_type_dtor(void *obj)
 	ao2_cleanup(payload->format);
 }
 
-struct ast_rtp_payload_type *ast_rtp_engine_alloc_payload_type(void)
+static struct ast_rtp_payload_type *rtp_payload_type_alloc(struct ast_format *format,
+	int payload, int rtp_code, int primary_mapping)
 {
-	struct ast_rtp_payload_type *payload;
+	struct ast_rtp_payload_type *type = ao2_alloc_options(
+		sizeof(*type), rtp_payload_type_dtor, AO2_ALLOC_OPT_LOCK_NOLOCK);
 
-	payload = ao2_alloc_options(sizeof(*payload), rtp_payload_type_dtor,
-		AO2_ALLOC_OPT_LOCK_NOLOCK);
+	if (!type) {
+		return NULL;
+	}
 
-	return payload;
+	type->format = ao2_bump(format);
+	type->asterisk_format = type->format != NULL;
+	type->payload = payload;
+	type->rtp_code = rtp_code;
+	type->primary_mapping = primary_mapping;
+
+	return type;
+}
+
+struct ast_rtp_payload_type *ast_rtp_engine_alloc_payload_type(void)
+{
+	return rtp_payload_type_alloc(NULL, 0, 0, 0);
 }
 
 int ast_rtp_engine_register2(struct ast_rtp_engine *engine, struct ast_module *module)
@@ -1250,31 +1264,112 @@ static int find_static_payload_type(int asterisk_format, const struct ast_format
 
 /*!
  * \internal
- * \brief Find the first unused dynamic rx payload type.
- * \since 14.0.0
+ * \brief Find the first unused payload type in a given range
  *
- * \param codecs Codecs structure to look in
+ * \param codecs The codec structure to look in
+ * \param start Starting index
+ * \param end Ending index
+ * \param ignore Skip these payloads types
  *
- * \note It is assumed that codecs is at least read locked before calling.
+ * \note The static_RTP_PT_lock object must be locked before calling
  *
  * \retval Numerical payload type
  * \retval -1 if not found.
  */
-static int rtp_codecs_find_empty_dynamic_rx(struct ast_rtp_codecs *codecs)
+static int find_unused_payload_in_range(const struct ast_rtp_codecs *codecs,
+		int start, int end, struct ast_rtp_payload_type *ignore[])
 {
-	struct ast_rtp_payload_type *type;
-	int idx;
-	int payload = -1;
+	int x;
 
-	idx = AST_RTP_PT_FIRST_DYNAMIC;
-	for (; idx < AST_VECTOR_SIZE(&codecs->payload_mapping_rx); ++idx) {
-		type = AST_VECTOR_GET(&codecs->payload_mapping_rx, idx);
+	for (x = start; x < end; ++x) {
+		struct ast_rtp_payload_type *type;
+
+		if (ignore[x]) {
+			continue;
+		} else if (!codecs || x >= AST_VECTOR_SIZE(&codecs->payload_mapping_rx)) {
+			return x;
+		}
+
+		type = AST_VECTOR_GET(&codecs->payload_mapping_rx, x);
 		if (!type) {
-			payload = idx;
-			break;
+			return x;
 		}
 	}
-	return payload;
+	return -1;
+}
+
+/*!
+ * \internal
+ * \brief Find an unused payload type
+ *
+ * \param codecs Codecs structure to look in
+ *
+ * \note Both static_RTP_PT_lock and codecs (if given) must be at least
+ *       read locked before calling.
+ *
+ * \retval Numerical payload type
+ * \retval -1 if not found.
+ */
+static int find_unused_payload(const struct ast_rtp_codecs *codecs)
+{
+	int res;
+
+	/* find next available dynamic payload slot */
+	res = find_unused_payload_in_range(
+		codecs, AST_RTP_PT_FIRST_DYNAMIC, AST_RTP_MAX_PT, static_RTP_PT);
+	if (res != -1) {
+		return res;
+	}
+
+	if (ast_option_rtpusedynamic) {
+		/*
+		 * We're using default values for some dynamic types. So if an unused
+		 * slot was not found try again, but this time ignore the default
+		 * values declared for dynamic types (except for 101 and 121) .
+		 */
+		static struct ast_rtp_payload_type *ignore[AST_RTP_MAX_PT] = {0};
+
+		ignore[101] = static_RTP_PT[101];
+		ignore[121] = static_RTP_PT[121];
+
+		res = find_unused_payload_in_range(
+			codecs, AST_RTP_PT_FIRST_DYNAMIC, AST_RTP_MAX_PT, ignore);
+		if (res != -1) {
+			return res;
+		}
+	}
+
+	/* http://www.iana.org/assignments/rtp-parameters
+	 * RFC 3551, Section 3: "[...] applications which need to define more
+	 * than 32 dynamic payload types MAY bind codes below 96, in which case
+	 * it is RECOMMENDED that unassigned payload type numbers be used
+	 * first". Updated by RFC 5761, Section 4: "[...] values in the range
+	 * 64-95 MUST NOT be used [to avoid conflicts with RTCP]". Summaries:
+	 * https://tools.ietf.org/html/draft-roach-mmusic-unified-plan#section-3.2.1.2
+	 * https://tools.ietf.org/html/draft-wu-avtcore-dynamic-pt-usage#section-3
+	 */
+	res = find_unused_payload_in_range(codecs, MAX(ast_option_rtpptdynamic, 35),
+		AST_RTP_PT_LAST_REASSIGN, static_RTP_PT);
+	if (res != -1) {
+		return res;
+	}
+
+	/* Yet, reusing mappings below 35 is not supported in Asterisk because
+	 * when Compact Headers are activated, no rtpmap is send for those below
+	 * 35. If you want to use 35 and below
+	 * A) do not use Compact Headers,
+	 * B) remove that code in chan_sip/res_pjsip, or
+	 * C) add a flag that this RTP Payload Type got reassigned dynamically
+	 *    and requires a rtpmap even with Compact Headers enabled.
+	 */
+	res = find_unused_payload_in_range(
+		codecs, MAX(ast_option_rtpptdynamic, 20), 35, static_RTP_PT);
+	if (res != -1) {
+		return res;
+	}
+
+	return find_unused_payload_in_range(
+		codecs, MAX(ast_option_rtpptdynamic, 0), 20, static_RTP_PT);
 }
 
 /*!
@@ -1331,30 +1426,26 @@ static int rtp_codecs_assign_payload_code_rx(struct ast_rtp_codecs *codecs, int
 	struct ast_rtp_payload_type *new_type;
 
 	payload = find_static_payload_type(asterisk_format, format, code);
-	if (payload < 0) {
+
+	if (payload < 0 && (!asterisk_format || ast_option_rtpusedynamic)) {
 		return payload;
 	}
 
-	new_type = ast_rtp_engine_alloc_payload_type();
+	new_type = rtp_payload_type_alloc(format, payload, code, 1);
 	if (!new_type) {
 		return -1;
 	}
-	new_type->format = ao2_bump(format);
-	new_type->asterisk_format = asterisk_format;
-	new_type->rtp_code = code;
-	new_type->payload = payload;
-	new_type->primary_mapping = 1;
 
 	ast_rwlock_wrlock(&codecs->codecs_lock);
-	if (payload < AST_RTP_PT_FIRST_DYNAMIC
+	if (payload > -1 && (payload < AST_RTP_PT_FIRST_DYNAMIC
 		|| AST_VECTOR_SIZE(&codecs->payload_mapping_rx) <= payload
-		|| !AST_VECTOR_GET(&codecs->payload_mapping_rx, payload)) {
+		|| !AST_VECTOR_GET(&codecs->payload_mapping_rx, payload))) {
 		/*
 		 * The payload type is a static assignment
 		 * or our default dynamic position is available.
 		 */
-		rtp_codecs_payload_replace_rx(codecs, payload, new_type);
-	} else if (-1 < (payload = rtp_codecs_find_empty_dynamic_rx(codecs))
+               rtp_codecs_payload_replace_rx(codecs, payload, new_type);
+	} else if (-1 < (payload = find_unused_payload(codecs))
 		|| -1 < (payload = rtp_codecs_find_non_primary_dynamic_rx(codecs))) {
 		/*
 		 * We found the first available empty dynamic position
@@ -1370,7 +1461,8 @@ static int rtp_codecs_assign_payload_code_rx(struct ast_rtp_codecs *codecs, int
 		 *
 		 * I don't think this is really possible.
 		 */
-		ast_log(LOG_WARNING, "No dynamic RTP payload type values available!\n");
+		ast_log(LOG_WARNING, "No dynamic RTP payload type values available "
+			"for %s - %d!\n", format ? ast_format_get_name(format) : "", code);
 	}
 	ast_rwlock_unlock(&codecs->codecs_lock);
 
@@ -2293,95 +2385,47 @@ static void set_next_mime_type(struct ast_format *format, int rtp_code, const ch
 	ast_rwlock_unlock(&mime_types_lock);
 }
 
-static void add_static_payload(int map, struct ast_format *format, int rtp_code)
+static void add_static_payload(int payload, struct ast_format *format, int rtp_code)
 {
-	int x;
 	struct ast_rtp_payload_type *type;
 
 	/*
 	 * ARRAY_LEN's result is cast to an int so 'map' is not autocast to a size_t,
 	 * which if negative would cause an assertion.
 	 */
-	ast_assert(map < (int)ARRAY_LEN(static_RTP_PT));
+	ast_assert(payload < (int)ARRAY_LEN(static_RTP_PT));
 
+	if (ast_option_rtpusedynamic && payload < 0) {
+		/*
+		 * We're going to build dynamic payloads dynamically. An RTP code is
+		 * required otherwise one will be dynamically allocated per instance.
+		 */
+		return;
+	}
+
+	/*
+	 * Either the given payload is truly a static type, or Asterisk is
+	 * globally storing the dynamic payloads in the static_RTP_PT object.
+	 */
 	ast_rwlock_wrlock(&static_RTP_PT_lock);
-	if (map < 0) {
-		/* find next available dynamic payload slot */
-		for (x = AST_RTP_PT_FIRST_DYNAMIC; x < AST_RTP_MAX_PT; ++x) {
-			if (!static_RTP_PT[x]) {
-				map = x;
-				break;
-			}
-		}
 
-		/* http://www.iana.org/assignments/rtp-parameters
-		 * RFC 3551, Section 3: "[...] applications which need to define more
-		 * than 32 dynamic payload types MAY bind codes below 96, in which case
-		 * it is RECOMMENDED that unassigned payload type numbers be used
-		 * first". Updated by RFC 5761, Section 4: "[...] values in the range
-		 * 64-95 MUST NOT be used [to avoid conflicts with RTCP]". Summaries:
-		 * https://tools.ietf.org/html/draft-roach-mmusic-unified-plan#section-3.2.1.2
-		 * https://tools.ietf.org/html/draft-wu-avtcore-dynamic-pt-usage#section-3
-		 */
-		if (map < 0) {
-			for (x = MAX(ast_option_rtpptdynamic, 35); x <= AST_RTP_PT_LAST_REASSIGN; ++x) {
-				if (!static_RTP_PT[x]) {
-					map = x;
-					break;
-				}
-			}
-		}
-		/* Yet, reusing mappings below 35 is not supported in Asterisk because
-		 * when Compact Headers are activated, no rtpmap is send for those below
-		 * 35. If you want to use 35 and below
-		 * A) do not use Compact Headers,
-		 * B) remove that code in chan_sip/res_pjsip, or
-		 * C) add a flag that this RTP Payload Type got reassigned dynamically
-		 *    and requires a rtpmap even with Compact Headers enabled.
+	if (payload < 0) {
+		/*
+		 * This is a dynamic payload that will be stored globally,
+		 * so find the next available empty slot.
 		 */
-		if (map < 0) {
-			for (x = MAX(ast_option_rtpptdynamic, 20); x < 35; ++x) {
-				if (!static_RTP_PT[x]) {
-					map = x;
-					break;
-				}
-			}
-		}
-		if (map < 0) {
-			for (x = MAX(ast_option_rtpptdynamic, 0); x < 20; ++x) {
-				if (!static_RTP_PT[x]) {
-					map = x;
-					break;
-				}
-			}
-		}
-
-		if (map < 0) {
-			if (format) {
-				ast_log(LOG_WARNING, "No Dynamic RTP mapping available for format %s\n",
-					ast_format_get_name(format));
-			} else {
-				ast_log(LOG_WARNING, "No Dynamic RTP mapping available for RTP code %d\n",
-					rtp_code);
-			}
-			ast_rwlock_unlock(&static_RTP_PT_lock);
+		payload = find_unused_payload(NULL);
+		if (payload < 0) {
+			ast_log(LOG_WARNING, "No dynamic RTP payload type values available "
+				"for %s - %d!\n", format ? ast_format_get_name(format) : "", rtp_code);
 			return;
 		}
 	}
 
-	type = ast_rtp_engine_alloc_payload_type();
+	type = rtp_payload_type_alloc(format, payload, rtp_code, 1);
 	if (type) {
-		if (format) {
-			ao2_ref(format, +1);
-			type->format = format;
-			type->asterisk_format = 1;
-		} else {
-			type->rtp_code = rtp_code;
-		}
-		type->payload = map;
-		type->primary_mapping = 1;
-		ao2_cleanup(static_RTP_PT[map]);
-		static_RTP_PT[map] = type;
+		ao2_cleanup(static_RTP_PT[payload]);
+		static_RTP_PT[payload] = type;
 	}
 	ast_rwlock_unlock(&static_RTP_PT_lock);
 }
@@ -2797,23 +2841,34 @@ int ast_rtp_engine_init(void)
 	add_static_payload(26, ast_format_jpeg, 0);
 	add_static_payload(31, ast_format_h261, 0);
 	add_static_payload(34, ast_format_h263, 0);
+
+	/*
+	 * Dynamic payload types - Even when dynamically assigning them we'll fall
+	 * back to using the statically declared values as the default number.
+	 */
+	add_static_payload(96, ast_format_slin192, 0);
 	add_static_payload(97, ast_format_ilbc, 0);
 	add_static_payload(98, ast_format_h263p, 0);
 	add_static_payload(99, ast_format_h264, 0);
+	add_static_payload(100, ast_format_vp8, 0);
 	add_static_payload(101, NULL, AST_RTP_DTMF);
 	add_static_payload(102, ast_format_siren7, 0);
 	add_static_payload(103, ast_format_h263p, 0);
 	add_static_payload(104, ast_format_mp4, 0);
 	add_static_payload(105, ast_format_t140_red, 0);   /* Real time text chat (with redundancy encoding) */
 	add_static_payload(106, ast_format_t140, 0);     /* Real time text chat */
+	add_static_payload(107, ast_format_opus, 0);
+
 	add_static_payload(110, ast_format_speex, 0);
 	add_static_payload(111, ast_format_g726, 0);
 	add_static_payload(112, ast_format_g726_aal2, 0);
+
 	add_static_payload(115, ast_format_siren14, 0);
 	add_static_payload(116, ast_format_g719, 0);
 	add_static_payload(117, ast_format_speex16, 0);
 	add_static_payload(118, ast_format_slin16, 0); /* 16 Khz signed linear */
 	add_static_payload(119, ast_format_speex32, 0);
+
 	add_static_payload(121, NULL, AST_RTP_CISCO_DTMF);   /* Must be type 121 */
 	add_static_payload(122, ast_format_slin12, 0);
 	add_static_payload(123, ast_format_slin24, 0);
@@ -2822,10 +2877,6 @@ int ast_rtp_engine_init(void)
 	add_static_payload(126, ast_format_slin48, 0);
 	add_static_payload(127, ast_format_slin96, 0);
 	/* payload types above 127 are not valid */
-	add_static_payload(96, ast_format_slin192, 0);
-	/* Opus and VP8 */
-	add_static_payload(100, ast_format_vp8, 0);
-	add_static_payload(107, ast_format_opus, 0);
 
 	return 0;
 }