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rtp: Add support for RTP extension negotiation and abs-send-time.
When RTP was originally created it had the ability to place a single extension in an RTP packet. In practice people wanted to potentially put multiple extensions in one and so RFC 5285 (obsoleted by RFC 8285) came into existence. This allows RTP extensions to be negotiated with a unique identifier to be used in the RTP packet, allowing multiple extensions to be present in the packet. This change extends the RTP engine API to add support for this. A user of it can enable extensions and the API provides the ability to retrieve the information (to construct SDP for example) and to provide negotiated information (from SDP). The end result is that the RTP engine can then query to see if the extension has been negotiated and what unique identifier is to be used. It is then up to the RTP engine implementation to construct the packet appropriately. The first extension to use this support is abs-send-time which is defined in the REMB draft[1] and is a second timestamp placed in an RTP packet which is for when the packet has left the sending system. It is used to more accurately determine the available bandwidth. ASTERISK-27831 [1] https://tools.ietf.org/html/draft-alvestrand-rmcat-remb-03 Change-Id: I508deac557867b1e27fc7339be890c8018171588
This commit is contained in:
Joshua Colp
@@ -533,6 +533,18 @@ enum ast_rtp_dtls_verify {
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AST_RTP_DTLS_VERIFY_CERTIFICATE = (1 << 1), /*!< Verify the certificate */
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};
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/*!
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* \brief Known RTP extensions
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*/
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enum ast_rtp_extension {
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/*! Per the RFC 0 should not be used, so we treat it as an unsupported extension placeholder */
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AST_RTP_EXTENSION_UNSUPPORTED = 0,
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/*! abs-send-time from https://tools.ietf.org/html/draft-alvestrand-rmcat-remb-03 */
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AST_RTP_EXTENSION_ABS_SEND_TIME,
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/*! The maximum number of known RTP extensions */
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AST_RTP_EXTENSION_MAX,
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};
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/*! \brief DTLS configuration structure */
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struct ast_rtp_dtls_cfg {
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unsigned int enabled:1; /*!< Whether DTLS support is enabled or not */
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@@ -654,6 +666,8 @@ struct ast_rtp_engine {
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struct ast_rtp_engine_ice *ice;
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/*! Callback to pointer for optional DTLS SRTP support */
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struct ast_rtp_engine_dtls *dtls;
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/*! Callback to enable an RTP extension (returns non-zero if supported) */
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int (*extension_enable)(struct ast_rtp_instance *instance, enum ast_rtp_extension extension);
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/*! Linked list information */
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AST_RWLIST_ENTRY(ast_rtp_engine) entry;
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};
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@@ -720,6 +734,22 @@ struct ast_rtp_glue {
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AST_RWLIST_ENTRY(ast_rtp_glue) entry;
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};
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/*!
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* \brief Directions for RTP extensions
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*/
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enum ast_rtp_extension_direction {
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/*! The extension is not negotiated and is not flowing */
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AST_RTP_EXTENSION_DIRECTION_NONE,
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/*! Send and receive */
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AST_RTP_EXTENSION_DIRECTION_SENDRECV,
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/*! Send only */
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AST_RTP_EXTENSION_DIRECTION_SENDONLY,
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/*! Receive only */
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AST_RTP_EXTENSION_DIRECTION_RECVONLY,
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/*! Negotiated but not sending or receiving */
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AST_RTP_EXTENSION_DIRECTION_INACTIVE,
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};
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/*!
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* \brief Allocation routine for \ref ast_rtp_payload_type
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*
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@@ -1246,6 +1276,109 @@ int ast_rtp_instance_get_prop(struct ast_rtp_instance *instance, enum ast_rtp_pr
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*/
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struct ast_rtp_codecs *ast_rtp_instance_get_codecs(struct ast_rtp_instance *instance);
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/*!
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* \brief Enable support for an RTP extension on an instance
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*
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* \param instance The RTP instance to enable the extension on
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* \param id The unique local identifier to use for this extension (-1 to have one auto selected)
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* \param extension The RTP extension
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* \param direction The initial direction that the RTP extension should be used in
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*
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* \retval 0 success
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* \retval -1 failure
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*
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* \since 15.5.0
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*/
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int ast_rtp_instance_extmap_enable(struct ast_rtp_instance *instance, int id, enum ast_rtp_extension extension,
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enum ast_rtp_extension_direction direction);
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/*!
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* \brief Negotiate received RTP extension information
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*
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* \param instance The RTP instance to set the extension on
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* \param id The local identifier for the extension
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* \param direction The direction that the extension should be used in
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* \param uri The unique URI for the extension
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* \param attributes Attributes specific to this extension (if NULL or empty then no attributes)
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*
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* \retval 0 success
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* \retval -1 failure
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*
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* \since 15.5.0
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*/
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int ast_rtp_instance_extmap_negotiate(struct ast_rtp_instance *instance, int id, enum ast_rtp_extension_direction direction,
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const char *uri, const char *attributes);
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/*!
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* \brief Clear negotiated RTP extension information
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*
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* \param instance The RTP instance to clear negotiated extension information on
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*/
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void ast_rtp_instance_extmap_clear(struct ast_rtp_instance *instance);
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/*!
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* \brief Retrieve the id for an RTP extension
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*
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* \param instance The RTP instance to retrieve the id from
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* \param extension The RTP extension
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*
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* \retval -1 not negotiated
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* \retval id if negotiated
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*
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* \since 15.5.0
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*/
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int ast_rtp_instance_extmap_get_id(struct ast_rtp_instance *instance, enum ast_rtp_extension extension);
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/*!
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* \brief Get the number of known unique identifiers
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*
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* \param instance The RTP instance to retrieve the count from
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*
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* \return the number of known unique identifiers
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*
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* \since 15.5.0
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*/
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size_t ast_rtp_instance_extmap_count(struct ast_rtp_instance *instance);
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/*!
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* \brief Retrieve the extension for an RTP extension id
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*
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* \param instance The RTP instance to retrieve the extension from
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* \param id The negotiated RTP extension id
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*
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* \retval extension the extension that maps to the id
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*
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* \since 15.5.0
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*
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* \note This will return AST_RTP_EXTENSION_UNSUPPORTED if an extension was proposed for this unique identifier
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* but it is not supported or if the unique identifier is unused.
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*/
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enum ast_rtp_extension ast_rtp_instance_extmap_get_extension(struct ast_rtp_instance *instance, int id);
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/*!
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* \brief Retrieve the negotiated direction for an RTP extension id
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*
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* \param instance The RTP instance to retrieve the direction from
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* \param id The negotiated RTP extension id
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*
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* \retval direction the direction that has been negotiated
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*
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* \since 15.5.0
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*/
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enum ast_rtp_extension_direction ast_rtp_instance_extmap_get_direction(struct ast_rtp_instance *instance, int id);
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/*!
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* \brief Retrieve the URI for an RTP extension id
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*
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* \param instance The RTP instance to retrieve the direction from
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* \param id The negotiated RTP extension id
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*
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* \retval uri The URI for the RTP extension
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*
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* \since 15.5.0
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*/
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const char *ast_rtp_instance_extmap_get_uri(struct ast_rtp_instance *instance, int id);
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/*!
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* \brief Initialize an RTP codecs structure
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*
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