asterisk/res/res_pjsip_sdp_rtp.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * Joshua Colp <jcolp@digium.com>
 * Kevin Harwell <kharwell@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \author Joshua Colp <jcolp@digium.com>
 *
 * \brief SIP SDP media stream handling
 */

/*** MODULEINFO
	<depend>pjproject</depend>
	<depend>res_pjsip</depend>
	<depend>res_pjsip_session</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <pjsip.h>
#include <pjsip_ua.h>
#include <pjmedia.h>
#include <pjlib.h>

ASTERISK_FILE_VERSION(__FILE__, "$Revision$")

#include "asterisk/module.h"
#include "asterisk/format.h"
#include "asterisk/format_cap.h"
#include "asterisk/rtp_engine.h"
#include "asterisk/netsock2.h"
#include "asterisk/channel.h"
#include "asterisk/causes.h"
#include "asterisk/sched.h"
#include "asterisk/acl.h"
#include "asterisk/sdp_srtp.h"

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"

/*! \brief Scheduler for RTCP purposes */
static struct ast_sched_context *sched;

/*! \brief Address for IPv4 RTP */
static struct ast_sockaddr address_ipv4;

/*! \brief Address for IPv6 RTP */
static struct ast_sockaddr address_ipv6;

static const char STR_AUDIO[] = "audio";
static const int FD_AUDIO = 0;

static const char STR_VIDEO[] = "video";
static const int FD_VIDEO = 2;

/*! \brief Retrieves an ast_format_type based on the given stream_type */
static enum ast_media_type stream_to_media_type(const char *stream_type)
{
	if (!strcasecmp(stream_type, STR_AUDIO)) {
		return AST_MEDIA_TYPE_AUDIO;
	} else if (!strcasecmp(stream_type, STR_VIDEO)) {
		return AST_MEDIA_TYPE_VIDEO;
	}

	return 0;
}

/*! \brief Get the starting descriptor for a media type */
static int media_type_to_fdno(enum ast_media_type media_type)
{
	switch (media_type) {
	case AST_MEDIA_TYPE_AUDIO: return FD_AUDIO;
	case AST_MEDIA_TYPE_VIDEO: return FD_VIDEO;
	case AST_MEDIA_TYPE_TEXT:
	case AST_MEDIA_TYPE_UNKNOWN:
	case AST_MEDIA_TYPE_IMAGE: break;
	}
	return -1;
}

/*! \brief Remove all other cap types but the one given */
static void format_cap_only_type(struct ast_format_cap *caps, enum ast_media_type media_type)
{
	int i = 0;
	while (i <= AST_MEDIA_TYPE_TEXT) {
		if (i != media_type && i != AST_MEDIA_TYPE_UNKNOWN) {
			ast_format_cap_remove_by_type(caps, i);
		}
		i += 1;
	}
}

/*! \brief Internal function which creates an RTP instance */
static int create_rtp(struct ast_sip_session *session, struct ast_sip_session_media *session_media, unsigned int ipv6)
{
	struct ast_rtp_engine_ice *ice;

	if (!(session_media->rtp = ast_rtp_instance_new(session->endpoint->media.rtp.engine, sched, ipv6 ? &address_ipv6 : &address_ipv4, NULL))) {
		ast_log(LOG_ERROR, "Unable to create RTP instance using RTP engine '%s'\n", session->endpoint->media.rtp.engine);
		return -1;
	}

	ast_rtp_instance_set_prop(session_media->rtp, AST_RTP_PROPERTY_RTCP, 1);
	ast_rtp_instance_set_prop(session_media->rtp, AST_RTP_PROPERTY_NAT, session->endpoint->media.rtp.symmetric);

	if (!session->endpoint->media.rtp.ice_support && (ice = ast_rtp_instance_get_ice(session_media->rtp))) {
		ice->stop(session_media->rtp);
	}

	if (session->endpoint->dtmf == AST_SIP_DTMF_RFC_4733) {
		ast_rtp_instance_dtmf_mode_set(session_media->rtp, AST_RTP_DTMF_MODE_RFC2833);
		ast_rtp_instance_set_prop(session_media->rtp, AST_RTP_PROPERTY_DTMF, 1);
	} else if (session->endpoint->dtmf == AST_SIP_DTMF_INBAND) {
		ast_rtp_instance_dtmf_mode_set(session_media->rtp, AST_RTP_DTMF_MODE_INBAND);
	}

	if (!strcmp(session_media->stream_type, STR_AUDIO) &&
			(session->endpoint->media.tos_audio || session->endpoint->media.cos_video)) {
		ast_rtp_instance_set_qos(session_media->rtp, session->endpoint->media.tos_audio,
				session->endpoint->media.cos_audio, "SIP RTP Audio");
	} else if (!strcmp(session_media->stream_type, STR_VIDEO) &&
			(session->endpoint->media.tos_video || session->endpoint->media.cos_video)) {
		ast_rtp_instance_set_qos(session_media->rtp, session->endpoint->media.tos_video,
				session->endpoint->media.cos_video, "SIP RTP Video");
	}

	return 0;
}

static void get_codecs(struct ast_sip_session *session, const struct pjmedia_sdp_media *stream, struct ast_rtp_codecs *codecs)
{
	pjmedia_sdp_attr *attr;
	pjmedia_sdp_rtpmap *rtpmap;
	pjmedia_sdp_fmtp fmtp;
	struct ast_format *format;
	int i, num = 0;
	char name[256];
	char media[20];
	char fmt_param[256];

	ast_rtp_codecs_payloads_initialize(codecs);

	/* Iterate through provided formats */
	for (i = 0; i < stream->desc.fmt_count; ++i) {
		/* The payload is kept as a string for things like t38 but for video it is always numerical */
		ast_rtp_codecs_payloads_set_m_type(codecs, NULL, pj_strtoul(&stream->desc.fmt[i]));
		/* Look for the optional rtpmap attribute */
		if (!(attr = pjmedia_sdp_media_find_attr2(stream, "rtpmap", &stream->desc.fmt[i]))) {
			continue;
		}

		/* Interpret the attribute as an rtpmap */
		if ((pjmedia_sdp_attr_to_rtpmap(session->inv_session->pool_prov, attr, &rtpmap)) != PJ_SUCCESS) {
			continue;
		}

		ast_copy_pj_str(name, &rtpmap->enc_name, sizeof(name));
		ast_copy_pj_str(media, (pj_str_t*)&stream->desc.media, sizeof(media));
		ast_rtp_codecs_payloads_set_rtpmap_type_rate(codecs, NULL, pj_strtoul(&stream->desc.fmt[i]),
							     media, name, 0, rtpmap->clock_rate);
		/* Look for an optional associated fmtp attribute */
		if (!(attr = pjmedia_sdp_media_find_attr2(stream, "fmtp", &rtpmap->pt))) {
			continue;
		}

		if ((pjmedia_sdp_attr_get_fmtp(attr, &fmtp)) == PJ_SUCCESS) {
			sscanf(pj_strbuf(&fmtp.fmt), "%d", &num);
			if ((format = ast_rtp_codecs_get_payload_format(codecs, num))) {
				struct ast_format *format_parsed;

				ast_copy_pj_str(fmt_param, &fmtp.fmt_param, sizeof(fmt_param));

				format_parsed = ast_format_parse_sdp_fmtp(format, fmt_param);
				if (format_parsed) {
					ast_rtp_codecs_payload_replace_format(codecs, num, format_parsed);
					ao2_ref(format_parsed, -1);
				}

				ao2_ref(format, -1);
			}
		}
	}

	/* Get the packetization, if it exists */
	if ((attr = pjmedia_sdp_media_find_attr2(stream, "ptime", NULL))) {
		unsigned long framing = pj_strtoul(pj_strltrim(&attr->value));
		if (framing && session->endpoint->media.rtp.use_ptime) {
			ast_rtp_codecs_set_framing(codecs, framing);
		}
	}
}

static int set_caps(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
		    const struct pjmedia_sdp_media *stream)
{
	RAII_VAR(struct ast_format_cap *, caps, NULL, ao2_cleanup);
	RAII_VAR(struct ast_format_cap *, peer, NULL, ao2_cleanup);
	RAII_VAR(struct ast_format_cap *, joint, NULL, ao2_cleanup);
	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
	struct ast_rtp_codecs codecs = AST_RTP_CODECS_NULL_INIT;
	int fmts = 0;
	int direct_media_enabled = !ast_sockaddr_isnull(&session_media->direct_media_addr) &&
		ast_format_cap_count(session->direct_media_cap);

	if (!(caps = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT)) ||
	    !(peer = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT)) ||
	    !(joint = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
		ast_log(LOG_ERROR, "Failed to allocate %s capabilities\n", session_media->stream_type);
		return -1;
	}

	/* get the endpoint capabilities */
	if (direct_media_enabled) {
		ast_format_cap_get_compatible(session->endpoint->media.codecs, session->direct_media_cap, caps);
		format_cap_only_type(caps, media_type);
	} else {
		ast_format_cap_append_from_cap(caps, session->endpoint->media.codecs, media_type);
	}

	/* get the capabilities on the peer */
	get_codecs(session, stream, &codecs);
	ast_rtp_codecs_payload_formats(&codecs, peer, &fmts);

	/* get the joint capabilities between peer and endpoint */
	ast_format_cap_get_compatible(caps, peer, joint);
	if (!ast_format_cap_count(joint)) {
		struct ast_str *usbuf = ast_str_alloca(256);
		struct ast_str *thembuf = ast_str_alloca(256);

		ast_rtp_codecs_payloads_destroy(&codecs);
		ast_log(LOG_NOTICE, "No joint capabilities for '%s' media stream between our configuration(%s) and incoming SDP(%s)\n",
			session_media->stream_type,
			ast_format_cap_get_names(caps, &usbuf),
			ast_format_cap_get_names(peer, &thembuf));
		return -1;
	}

	ast_rtp_codecs_payloads_copy(&codecs, ast_rtp_instance_get_codecs(session_media->rtp),
				     session_media->rtp);

	ast_format_cap_append_from_cap(session->req_caps, joint, AST_MEDIA_TYPE_UNKNOWN);

	if (session->channel) {

		ast_channel_lock(session->channel);

		/*
		 * Apply the new formats to the channel, potentially changing
		 * raw read/write formats and translation path while doing so.
		 */
		ast_channel_nativeformats_set(session->channel, joint);
		ast_set_read_format(session->channel, ast_channel_readformat(session->channel));
		ast_set_write_format(session->channel, ast_channel_writeformat(session->channel));
		ast_channel_unlock(session->channel);
	}

	ast_rtp_codecs_payloads_destroy(&codecs);
	return 0;
}

static pjmedia_sdp_attr* generate_rtpmap_attr(pjmedia_sdp_media *media, pj_pool_t *pool, int rtp_code,
					      int asterisk_format, struct ast_format *format, int code)
{
	pjmedia_sdp_rtpmap rtpmap;
	pjmedia_sdp_attr *attr = NULL;
	char tmp[64];

	snprintf(tmp, sizeof(tmp), "%d", rtp_code);
	pj_strdup2(pool, &media->desc.fmt[media->desc.fmt_count++], tmp);
	rtpmap.pt = media->desc.fmt[media->desc.fmt_count - 1];
	rtpmap.clock_rate = ast_rtp_lookup_sample_rate2(asterisk_format, format, code);
	pj_strdup2(pool, &rtpmap.enc_name, ast_rtp_lookup_mime_subtype2(asterisk_format, format, code, 0));
	rtpmap.param.slen = 0;
	rtpmap.param.ptr = NULL;

	pjmedia_sdp_rtpmap_to_attr(pool, &rtpmap, &attr);

	return attr;
}

static pjmedia_sdp_attr* generate_fmtp_attr(pj_pool_t *pool, struct ast_format *format, int rtp_code)
{
	struct ast_str *fmtp0 = ast_str_alloca(256);
	pj_str_t fmtp1;
	pjmedia_sdp_attr *attr = NULL;
	char *tmp;

	ast_format_generate_sdp_fmtp(format, rtp_code, &fmtp0);
	if (ast_str_strlen(fmtp0)) {
		tmp = ast_str_buffer(fmtp0) + ast_str_strlen(fmtp0) - 1;
		/* remove any carriage return line feeds */
		while (*tmp == '\r' || *tmp == '\n') --tmp;
		*++tmp = '\0';
		/* ast...generate gives us everything, just need value */
		tmp = strchr(ast_str_buffer(fmtp0), ':');
		if (tmp && tmp + 1) {
			fmtp1 = pj_str(tmp + 1);
		} else {
			fmtp1 = pj_str(ast_str_buffer(fmtp0));
		}
		attr = pjmedia_sdp_attr_create(pool, "fmtp", &fmtp1);
	}
	return attr;
}

/*! \brief Function which adds ICE attributes to a media stream */
static void add_ice_to_stream(struct ast_sip_session *session, struct ast_sip_session_media *session_media, pj_pool_t *pool, pjmedia_sdp_media *media)
{
	struct ast_rtp_engine_ice *ice;
	struct ao2_container *candidates;
	const char *username, *password;
	pj_str_t stmp;
	pjmedia_sdp_attr *attr;
	struct ao2_iterator it_candidates;
	struct ast_rtp_engine_ice_candidate *candidate;

	if (!session->endpoint->media.rtp.ice_support || !(ice = ast_rtp_instance_get_ice(session_media->rtp)) ||
		!(candidates = ice->get_local_candidates(session_media->rtp))) {
		return;
	}

	if ((username = ice->get_ufrag(session_media->rtp))) {
		attr = pjmedia_sdp_attr_create(pool, "ice-ufrag", pj_cstr(&stmp, username));
		media->attr[media->attr_count++] = attr;
	}

	if ((password = ice->get_password(session_media->rtp))) {
		attr = pjmedia_sdp_attr_create(pool, "ice-pwd", pj_cstr(&stmp, password));
		media->attr[media->attr_count++] = attr;
	}

	it_candidates = ao2_iterator_init(candidates, 0);
	for (; (candidate = ao2_iterator_next(&it_candidates)); ao2_ref(candidate, -1)) {
		struct ast_str *attr_candidate = ast_str_create(128);

		ast_str_set(&attr_candidate, -1, "%s %u %s %d %s ", candidate->foundation, candidate->id, candidate->transport,
					candidate->priority, ast_sockaddr_stringify_addr_remote(&candidate->address));
		ast_str_append(&attr_candidate, -1, "%s typ ", ast_sockaddr_stringify_port(&candidate->address));

		switch (candidate->type) {
			case AST_RTP_ICE_CANDIDATE_TYPE_HOST:
				ast_str_append(&attr_candidate, -1, "host");
				break;
			case AST_RTP_ICE_CANDIDATE_TYPE_SRFLX:
				ast_str_append(&attr_candidate, -1, "srflx");
				break;
			case AST_RTP_ICE_CANDIDATE_TYPE_RELAYED:
				ast_str_append(&attr_candidate, -1, "relay");
				break;
		}

		if (!ast_sockaddr_isnull(&candidate->relay_address)) {
			ast_str_append(&attr_candidate, -1, " raddr %s rport", ast_sockaddr_stringify_addr_remote(&candidate->relay_address));
			ast_str_append(&attr_candidate, -1, " %s", ast_sockaddr_stringify_port(&candidate->relay_address));
		}

		attr = pjmedia_sdp_attr_create(pool, "candidate", pj_cstr(&stmp, ast_str_buffer(attr_candidate)));
		media->attr[media->attr_count++] = attr;

		ast_free(attr_candidate);
	}

	ao2_iterator_destroy(&it_candidates);
	ao2_ref(candidates, -1);
}

/*! \brief Function which processes ICE attributes in an audio stream */
static void process_ice_attributes(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
				   const struct pjmedia_sdp_session *remote, const struct pjmedia_sdp_media *remote_stream)
{
	struct ast_rtp_engine_ice *ice;
	const pjmedia_sdp_attr *attr;
	char attr_value[256];
	unsigned int attr_i;

	/* If ICE support is not enabled or available exit early */
	if (!session->endpoint->media.rtp.ice_support || !(ice = ast_rtp_instance_get_ice(session_media->rtp))) {
		return;
	}

	attr = pjmedia_sdp_media_find_attr2(remote_stream, "ice-ufrag", NULL);
	if (!attr) {
		attr = pjmedia_sdp_attr_find2(remote->attr_count, remote->attr, "ice-ufrag", NULL);
	}
	if (attr) {
		ast_copy_pj_str(attr_value, (pj_str_t*)&attr->value, sizeof(attr_value));
		ice->set_authentication(session_media->rtp, attr_value, NULL);
	} else {
		return;
	}

	attr = pjmedia_sdp_media_find_attr2(remote_stream, "ice-pwd", NULL);
	if (!attr) {
		attr = pjmedia_sdp_attr_find2(remote->attr_count, remote->attr, "ice-pwd", NULL);
	}
	if (attr) {
		ast_copy_pj_str(attr_value, (pj_str_t*)&attr->value, sizeof(attr_value));
		ice->set_authentication(session_media->rtp, NULL, attr_value);
	} else {
		return;
	}

	if (pjmedia_sdp_media_find_attr2(remote_stream, "ice-lite", NULL)) {
		ice->ice_lite(session_media->rtp);
	}

	/* Find all of the candidates */
	for (attr_i = 0; attr_i < remote_stream->attr_count; ++attr_i) {
		char foundation[32], transport[32], address[PJ_INET6_ADDRSTRLEN + 1], cand_type[6], relay_address[PJ_INET6_ADDRSTRLEN + 1] = "";
		unsigned int port, relay_port = 0;
		struct ast_rtp_engine_ice_candidate candidate = { 0, };

		attr = remote_stream->attr[attr_i];

		/* If this is not a candidate line skip it */
		if (pj_strcmp2(&attr->name, "candidate")) {
			continue;
		}

		ast_copy_pj_str(attr_value, (pj_str_t*)&attr->value, sizeof(attr_value));

		if (sscanf(attr_value, "%31s %30u %31s %30u %46s %30u typ %5s %*s %23s %*s %30u", foundation, &candidate.id, transport,
			(unsigned *)&candidate.priority, address, &port, cand_type, relay_address, &relay_port) < 7) {
			/* Candidate did not parse properly */
			continue;
		}

		candidate.foundation = foundation;
		candidate.transport = transport;

		ast_sockaddr_parse(&candidate.address, address, PARSE_PORT_FORBID);
		ast_sockaddr_set_port(&candidate.address, port);

		if (!strcasecmp(cand_type, "host")) {
			candidate.type = AST_RTP_ICE_CANDIDATE_TYPE_HOST;
		} else if (!strcasecmp(cand_type, "srflx")) {
			candidate.type = AST_RTP_ICE_CANDIDATE_TYPE_SRFLX;
		} else if (!strcasecmp(cand_type, "relay")) {
			candidate.type = AST_RTP_ICE_CANDIDATE_TYPE_RELAYED;
		} else {
			continue;
		}

		if (!ast_strlen_zero(relay_address)) {
			ast_sockaddr_parse(&candidate.relay_address, relay_address, PARSE_PORT_FORBID);
		}

		if (relay_port) {
			ast_sockaddr_set_port(&candidate.relay_address, relay_port);
		}

		ice->add_remote_candidate(session_media->rtp, &candidate);
	}

	ice->set_role(session_media->rtp, pjmedia_sdp_neg_was_answer_remote(session->inv_session->neg) == PJ_TRUE ?
		AST_RTP_ICE_ROLE_CONTROLLING : AST_RTP_ICE_ROLE_CONTROLLED);
	ice->start(session_media->rtp);
}

/*! \brief figure out if media stream has crypto lines for sdes */
static int media_stream_has_crypto(const struct pjmedia_sdp_media *stream)
{
	int i;

	for (i = 0; i < stream->attr_count; i++) {
		pjmedia_sdp_attr *attr;

		/* check the stream for the required crypto attribute */
		attr = stream->attr[i];
		if (pj_strcmp2(&attr->name, "crypto")) {
			continue;
		}

		return 1;
	}

	return 0;
}

/*! \brief figure out media transport encryption type from the media transport string */
static enum ast_sip_session_media_encryption get_media_encryption_type(pj_str_t transport,
	const struct pjmedia_sdp_media *stream, unsigned int *optimistic)
{
	RAII_VAR(char *, transport_str, ast_strndup(transport.ptr, transport.slen), ast_free);

	*optimistic = 0;

	if (strstr(transport_str, "UDP/TLS")) {
		return AST_SIP_MEDIA_ENCRYPT_DTLS;
	} else if (strstr(transport_str, "SAVP")) {
		return AST_SIP_MEDIA_ENCRYPT_SDES;
	} else if (media_stream_has_crypto(stream)) {
		*optimistic = 1;
		return AST_SIP_MEDIA_ENCRYPT_SDES;
	} else {
		return AST_SIP_MEDIA_ENCRYPT_NONE;
	}
}

/*!
 * \brief Checks whether the encryption offered in SDP is compatible with the endpoint's configuration
 * \internal
 *
 * \param endpoint_encryption Media encryption configured for the endpoint
 * \param stream pjmedia_sdp_media stream description
 *
 * \retval AST_SIP_MEDIA_TRANSPORT_INVALID on encryption mismatch
 * \retval The encryption requested in the SDP
 */
static enum ast_sip_session_media_encryption check_endpoint_media_transport(
	struct ast_sip_endpoint *endpoint,
	const struct pjmedia_sdp_media *stream)
{
	enum ast_sip_session_media_encryption incoming_encryption;
	char transport_end = stream->desc.transport.ptr[stream->desc.transport.slen - 1];
	unsigned int optimistic;

	if ((transport_end == 'F' && !endpoint->media.rtp.use_avpf)
		|| (transport_end != 'F' && endpoint->media.rtp.use_avpf)) {
		return AST_SIP_MEDIA_TRANSPORT_INVALID;
	}

	incoming_encryption = get_media_encryption_type(stream->desc.transport, stream, &optimistic);

	if (incoming_encryption == endpoint->media.rtp.encryption) {
		return incoming_encryption;
	}

	if (endpoint->media.rtp.force_avp ||
		endpoint->media.rtp.encryption_optimistic) {
		return incoming_encryption;
	}

	/* If an optimistic offer has been made but encryption is not enabled consider it as having
	 * no offer of crypto at all instead of invalid so the session proceeds.
	 */
	if (optimistic) {
		return AST_SIP_MEDIA_ENCRYPT_NONE;
	}

	return AST_SIP_MEDIA_TRANSPORT_INVALID;
}

static int setup_srtp(struct ast_sip_session_media *session_media)
{
	if (!session_media->srtp) {
		session_media->srtp = ast_sdp_srtp_alloc();
		if (!session_media->srtp) {
			return -1;
		}
	}

	if (!session_media->srtp->crypto) {
		session_media->srtp->crypto = ast_sdp_crypto_alloc();
		if (!session_media->srtp->crypto) {
			return -1;
		}
	}

	return 0;
}

static int setup_dtls_srtp(struct ast_sip_session *session,
	struct ast_sip_session_media *session_media)
{
	struct ast_rtp_engine_dtls *dtls;

	if (!session->endpoint->media.rtp.dtls_cfg.enabled || !session_media->rtp) {
		return -1;
	}

	dtls = ast_rtp_instance_get_dtls(session_media->rtp);
	if (!dtls) {
		return -1;
	}

	session->endpoint->media.rtp.dtls_cfg.suite = ((session->endpoint->media.rtp.srtp_tag_32) ? AST_AES_CM_128_HMAC_SHA1_32 : AST_AES_CM_128_HMAC_SHA1_80);
	if (dtls->set_configuration(session_media->rtp, &session->endpoint->media.rtp.dtls_cfg)) {
		ast_log(LOG_ERROR, "Attempted to set an invalid DTLS-SRTP configuration on RTP instance '%p'\n",
			session_media->rtp);
		return -1;
	}

	if (setup_srtp(session_media)) {
		return -1;
	}
	return 0;
}

static void apply_dtls_attrib(struct ast_sip_session_media *session_media,
	pjmedia_sdp_attr *attr)
{
	struct ast_rtp_engine_dtls *dtls = ast_rtp_instance_get_dtls(session_media->rtp);
	pj_str_t *value;

	if (!attr->value.ptr) {
		return;
	}

	value = pj_strtrim(&attr->value);

	if (!pj_strcmp2(&attr->name, "setup")) {
		if (!pj_stricmp2(value, "active")) {
			dtls->set_setup(session_media->rtp, AST_RTP_DTLS_SETUP_ACTIVE);
		} else if (!pj_stricmp2(value, "passive")) {
			dtls->set_setup(session_media->rtp, AST_RTP_DTLS_SETUP_PASSIVE);
		} else if (!pj_stricmp2(value, "actpass")) {
			dtls->set_setup(session_media->rtp, AST_RTP_DTLS_SETUP_ACTPASS);
		} else if (!pj_stricmp2(value, "holdconn")) {
			dtls->set_setup(session_media->rtp, AST_RTP_DTLS_SETUP_HOLDCONN);
		} else {
			ast_log(LOG_WARNING, "Unsupported setup attribute value '%*s'\n", (int)value->slen, value->ptr);
		}
	} else if (!pj_strcmp2(&attr->name, "connection")) {
		if (!pj_stricmp2(value, "new")) {
			dtls->reset(session_media->rtp);
		} else if (!pj_stricmp2(value, "existing")) {
			/* Do nothing */
		} else {
			ast_log(LOG_WARNING, "Unsupported connection attribute value '%*s'\n", (int)value->slen, value->ptr);
		}
	} else if (!pj_strcmp2(&attr->name, "fingerprint")) {
		char hash_value[256], hash[32];
		char fingerprint_text[value->slen + 1];
		ast_copy_pj_str(fingerprint_text, value, sizeof(fingerprint_text));
			if (sscanf(fingerprint_text, "%31s %255s", hash, hash_value) == 2) {
			if (!strcasecmp(hash, "sha-1")) {
				dtls->set_fingerprint(session_media->rtp, AST_RTP_DTLS_HASH_SHA1, hash_value);
			} else if (!strcasecmp(hash, "sha-256")) {
				dtls->set_fingerprint(session_media->rtp, AST_RTP_DTLS_HASH_SHA256, hash_value);
			} else {
				ast_log(LOG_WARNING, "Unsupported fingerprint hash type '%s'\n",
				hash);
			}
		}
	}
}

static int parse_dtls_attrib(struct ast_sip_session_media *session_media,
	const struct pjmedia_sdp_session *sdp,
	const struct pjmedia_sdp_media *stream)
{
	int i;

	for (i = 0; i < sdp->attr_count; i++) {
		apply_dtls_attrib(session_media, sdp->attr[i]);
	}

	for (i = 0; i < stream->attr_count; i++) {
		apply_dtls_attrib(session_media, stream->attr[i]);
	}

	ast_set_flag(session_media->srtp, AST_SRTP_CRYPTO_OFFER_OK);

	return 0;
}

static int setup_sdes_srtp(struct ast_sip_session_media *session_media,
	const struct pjmedia_sdp_media *stream)
{
	int i;

	for (i = 0; i < stream->attr_count; i++) {
		pjmedia_sdp_attr *attr;
		RAII_VAR(char *, crypto_str, NULL, ast_free);

		/* check the stream for the required crypto attribute */
		attr = stream->attr[i];
		if (pj_strcmp2(&attr->name, "crypto")) {
			continue;
		}

		crypto_str = ast_strndup(attr->value.ptr, attr->value.slen);
		if (!crypto_str) {
			return -1;
		}

		if (setup_srtp(session_media)) {
			return -1;
		}

		if (!ast_sdp_crypto_process(session_media->rtp, session_media->srtp, crypto_str)) {
			/* found a valid crypto attribute */
			return 0;
		}

		ast_debug(1, "Ignoring crypto offer with unsupported parameters: %s\n", crypto_str);
	}

	/* no usable crypto attributes found */
	return -1;
}

static int setup_media_encryption(struct ast_sip_session *session,
	struct ast_sip_session_media *session_media,
	const struct pjmedia_sdp_session *sdp,
	const struct pjmedia_sdp_media *stream)
{
	switch (session_media->encryption) {
	case AST_SIP_MEDIA_ENCRYPT_SDES:
		if (setup_sdes_srtp(session_media, stream)) {
			return -1;
		}
		break;
	case AST_SIP_MEDIA_ENCRYPT_DTLS:
		if (setup_dtls_srtp(session, session_media)) {
			return -1;
		}
		if (parse_dtls_attrib(session_media, sdp, stream)) {
			return -1;
		}
		break;
	case AST_SIP_MEDIA_TRANSPORT_INVALID:
	case AST_SIP_MEDIA_ENCRYPT_NONE:
		break;
	}

	return 0;
}

/*! \brief Function which negotiates an incoming media stream */
static int negotiate_incoming_sdp_stream(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
					 const struct pjmedia_sdp_session *sdp, const struct pjmedia_sdp_media *stream)
{
	char host[NI_MAXHOST];
	RAII_VAR(struct ast_sockaddr *, addrs, NULL, ast_free_ptr);
	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
	enum ast_sip_session_media_encryption encryption = AST_SIP_MEDIA_ENCRYPT_NONE;
	int res;

	/* If port is 0, ignore this media stream */
	if (!stream->desc.port) {
		ast_debug(3, "Media stream '%s' is already declined\n", session_media->stream_type);
		return 0;
	}

	/* If no type formats have been configured reject this stream */
	if (!ast_format_cap_has_type(session->endpoint->media.codecs, media_type)) {
		ast_debug(3, "Endpoint has no codecs for media type '%s', declining stream\n", session_media->stream_type);
		return 0;
	}

	/* Ensure incoming transport is compatible with the endpoint's configuration */
	if (!session->endpoint->media.rtp.use_received_transport) {
		encryption = check_endpoint_media_transport(session->endpoint, stream);

		if (encryption == AST_SIP_MEDIA_TRANSPORT_INVALID) {
			return -1;
		}
	}

	ast_copy_pj_str(host, stream->conn ? &stream->conn->addr : &sdp->conn->addr, sizeof(host));

	/* Ensure that the address provided is valid */
	if (ast_sockaddr_resolve(&addrs, host, PARSE_PORT_FORBID, AST_AF_UNSPEC) <= 0) {
		/* The provided host was actually invalid so we error out this negotiation */
		return -1;
	}

	/* Using the connection information create an appropriate RTP instance */
	if (!session_media->rtp && create_rtp(session, session_media, ast_sockaddr_is_ipv6(addrs))) {
		return -1;
	}

	res = setup_media_encryption(session, session_media, sdp, stream);
	if (res) {
		if (!session->endpoint->media.rtp.encryption_optimistic) {
			/* If optimistic encryption is disabled and crypto should have been enabled
			 * but was not this session must fail.
			 */
			return -1;
		}
		/* There is no encryption, sad. */
		session_media->encryption = AST_SIP_MEDIA_ENCRYPT_NONE;
 	}

	/* If we've been explicitly configured to use the received transport OR if
	 * encryption is on and crypto is present use the received transport.
	 * This is done in case of optimistic because it may come in as RTP/AVP or RTP/SAVP depending
	 * on the configuration of the remote endpoint (optimistic themselves or mandatory).
	 */
	if ((session->endpoint->media.rtp.use_received_transport) ||
		((encryption == AST_SIP_MEDIA_ENCRYPT_SDES) && !res)) {
		pj_strdup(session->inv_session->pool, &session_media->transport, &stream->desc.transport);
 	}

	if (set_caps(session, session_media, stream)) {
		return 0;
	}
	return 1;
}

static int add_crypto_to_stream(struct ast_sip_session *session,
	struct ast_sip_session_media *session_media,
	pj_pool_t *pool, pjmedia_sdp_media *media)
{
	pj_str_t stmp;
	pjmedia_sdp_attr *attr;
	enum ast_rtp_dtls_hash hash;
	const char *crypto_attribute;
	struct ast_rtp_engine_dtls *dtls;
	static const pj_str_t STR_NEW = { "new", 3 };
	static const pj_str_t STR_EXISTING = { "existing", 8 };
	static const pj_str_t STR_ACTIVE = { "active", 6 };
	static const pj_str_t STR_PASSIVE = { "passive", 7 };
	static const pj_str_t STR_ACTPASS = { "actpass", 7 };
	static const pj_str_t STR_HOLDCONN = { "holdconn", 8 };

	switch (session_media->encryption) {
	case AST_SIP_MEDIA_ENCRYPT_NONE:
	case AST_SIP_MEDIA_TRANSPORT_INVALID:
		break;
	case AST_SIP_MEDIA_ENCRYPT_SDES:
		if (!session_media->srtp) {
			session_media->srtp = ast_sdp_srtp_alloc();
			if (!session_media->srtp) {
				return -1;
			}
		}

		crypto_attribute = ast_sdp_srtp_get_attrib(session_media->srtp,
			0 /* DTLS running? No */,
			session->endpoint->media.rtp.srtp_tag_32 /* 32 byte tag length? */);
		if (!crypto_attribute) {
			/* No crypto attribute to add, bad news */
			return -1;
		}

		attr = pjmedia_sdp_attr_create(pool, "crypto", pj_cstr(&stmp, crypto_attribute));
		media->attr[media->attr_count++] = attr;
		break;
	case AST_SIP_MEDIA_ENCRYPT_DTLS:
		if (setup_dtls_srtp(session, session_media)) {
			return -1;
		}

		dtls = ast_rtp_instance_get_dtls(session_media->rtp);
		if (!dtls) {
			return -1;
		}

		switch (dtls->get_connection(session_media->rtp)) {
		case AST_RTP_DTLS_CONNECTION_NEW:
			attr = pjmedia_sdp_attr_create(pool, "connection", &STR_NEW);
			media->attr[media->attr_count++] = attr;
			break;
		case AST_RTP_DTLS_CONNECTION_EXISTING:
			attr = pjmedia_sdp_attr_create(pool, "connection", &STR_EXISTING);
			media->attr[media->attr_count++] = attr;
			break;
		default:
			break;
		}

		switch (dtls->get_setup(session_media->rtp)) {
		case AST_RTP_DTLS_SETUP_ACTIVE:
			attr = pjmedia_sdp_attr_create(pool, "setup", &STR_ACTIVE);
			media->attr[media->attr_count++] = attr;
			break;
		case AST_RTP_DTLS_SETUP_PASSIVE:
			attr = pjmedia_sdp_attr_create(pool, "setup", &STR_PASSIVE);
			media->attr[media->attr_count++] = attr;
			break;
		case AST_RTP_DTLS_SETUP_ACTPASS:
			attr = pjmedia_sdp_attr_create(pool, "setup", &STR_ACTPASS);
			media->attr[media->attr_count++] = attr;
			break;
		case AST_RTP_DTLS_SETUP_HOLDCONN:
			attr = pjmedia_sdp_attr_create(pool, "setup", &STR_HOLDCONN);
			media->attr[media->attr_count++] = attr;
			break;
		default:
			break;
		}

		hash = dtls->get_fingerprint_hash(session_media->rtp);
		crypto_attribute = dtls->get_fingerprint(session_media->rtp);
		if (crypto_attribute && (hash == AST_RTP_DTLS_HASH_SHA1 || hash == AST_RTP_DTLS_HASH_SHA256)) {
			RAII_VAR(struct ast_str *, fingerprint, ast_str_create(64), ast_free);
			if (!fingerprint) {
				return -1;
			}

			if (hash == AST_RTP_DTLS_HASH_SHA1) {
				ast_str_set(&fingerprint, 0, "SHA-1 %s", crypto_attribute);
			} else {
				ast_str_set(&fingerprint, 0, "SHA-256 %s", crypto_attribute);
			}

			attr = pjmedia_sdp_attr_create(pool, "fingerprint", pj_cstr(&stmp, ast_str_buffer(fingerprint)));
			media->attr[media->attr_count++] = attr;
		}
		break;
	}

	return 0;
}

/*! \brief Function which creates an outgoing stream */
static int create_outgoing_sdp_stream(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
				      struct pjmedia_sdp_session *sdp)
{
	pj_pool_t *pool = session->inv_session->pool_prov;
	static const pj_str_t STR_IN = { "IN", 2 };
	static const pj_str_t STR_IP4 = { "IP4", 3};
	static const pj_str_t STR_IP6 = { "IP6", 3};
	static const pj_str_t STR_SENDRECV = { "sendrecv", 8 };
	static const pj_str_t STR_SENDONLY = { "sendonly", 8 };
	pjmedia_sdp_media *media;
	char hostip[PJ_INET6_ADDRSTRLEN+2];
	struct ast_sockaddr addr;
	char tmp[512];
	pj_str_t stmp;
	pjmedia_sdp_attr *attr;
	int index = 0;
	int noncodec = (session->endpoint->dtmf == AST_SIP_DTMF_RFC_4733) ? AST_RTP_DTMF : 0;
	int min_packet_size = 0, max_packet_size = 0;
	int rtp_code;
	RAII_VAR(struct ast_format_cap *, caps, NULL, ao2_cleanup);
	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
	int use_override_prefs = ast_format_cap_count(session->req_caps);

	int direct_media_enabled = !ast_sockaddr_isnull(&session_media->direct_media_addr) &&
		ast_format_cap_count(session->direct_media_cap);

	if ((use_override_prefs && !ast_format_cap_has_type(session->req_caps, media_type)) ||
	    (!use_override_prefs && !ast_format_cap_has_type(session->endpoint->media.codecs, media_type))) {
		/* If no type formats are configured don't add a stream */
		return 0;
	} else if (!session_media->rtp && create_rtp(session, session_media, session->endpoint->media.rtp.ipv6)) {
		return -1;
	}

	if (!(media = pj_pool_zalloc(pool, sizeof(struct pjmedia_sdp_media))) ||
		!(media->conn = pj_pool_zalloc(pool, sizeof(struct pjmedia_sdp_conn)))) {
		return -1;
	}

	if (add_crypto_to_stream(session, session_media, pool, media)) {
		return -1;
	}

	media->desc.media = pj_str(session_media->stream_type);
	if (pj_strlen(&session_media->transport)) {
		/* If a transport has already been specified use it */
		media->desc.transport = session_media->transport;
	} else {
		media->desc.transport = pj_str(ast_sdp_get_rtp_profile(
			/* Optimistic encryption places crypto in the normal RTP/AVP profile */
			!session->endpoint->media.rtp.encryption_optimistic &&
				(session_media->encryption == AST_SIP_MEDIA_ENCRYPT_SDES),
			session_media->rtp, session->endpoint->media.rtp.use_avpf,
			session->endpoint->media.rtp.force_avp));
	}

	/* Add connection level details */
	if (direct_media_enabled) {
		ast_copy_string(hostip, ast_sockaddr_stringify_fmt(&session_media->direct_media_addr, AST_SOCKADDR_STR_ADDR), sizeof(hostip));
	} else if (ast_strlen_zero(session->endpoint->media.address)) {
		pj_sockaddr localaddr;

		if (pj_gethostip(session->endpoint->media.rtp.ipv6 ? pj_AF_INET6() : pj_AF_INET(), &localaddr)) {
			return -1;
		}
		pj_sockaddr_print(&localaddr, hostip, sizeof(hostip), 2);
	} else {
		ast_copy_string(hostip, session->endpoint->media.address, sizeof(hostip));
	}

	media->conn->net_type = STR_IN;
	media->conn->addr_type = session->endpoint->media.rtp.ipv6 ? STR_IP6 : STR_IP4;
	pj_strdup2(pool, &media->conn->addr, hostip);
	ast_rtp_instance_get_local_address(session_media->rtp, &addr);
	media->desc.port = direct_media_enabled ? ast_sockaddr_port(&session_media->direct_media_addr) : (pj_uint16_t) ast_sockaddr_port(&addr);
	media->desc.port_count = 1;

	/* Add ICE attributes and candidates */
	add_ice_to_stream(session, session_media, pool, media);

	if (!(caps = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
		ast_log(LOG_ERROR, "Failed to allocate %s capabilities\n", session_media->stream_type);
		return -1;
	}

	if (direct_media_enabled) {
		ast_format_cap_get_compatible(session->endpoint->media.codecs, session->direct_media_cap, caps);
	} else if (!ast_format_cap_count(session->req_caps) ||
		!ast_format_cap_iscompatible(session->req_caps, session->endpoint->media.codecs)) {
		ast_format_cap_append_from_cap(caps, session->endpoint->media.codecs, media_type);
	} else {
		ast_format_cap_append_from_cap(caps, session->req_caps, media_type);
	}

	for (index = 0; index < ast_format_cap_count(caps); ++index) {
		struct ast_format *format = ast_format_cap_get_format(caps, index);

		if (ast_format_get_type(format) != media_type) {
			ao2_ref(format, -1);
			continue;
		}

		if ((rtp_code = ast_rtp_codecs_payload_code(ast_rtp_instance_get_codecs(session_media->rtp), 1, format, 0)) == -1) {
			ast_log(LOG_WARNING,"Unable to get rtp codec payload code for %s\n", ast_format_get_name(format));
			ao2_ref(format, -1);
			continue;
		}

		if (!(attr = generate_rtpmap_attr(media, pool, rtp_code, 1, format, 0))) {
			ao2_ref(format, -1);
			continue;
		}
		media->attr[media->attr_count++] = attr;

		if ((attr = generate_fmtp_attr(pool, format, rtp_code))) {
			media->attr[media->attr_count++] = attr;
		}

		if (ast_format_get_maximum_ms(format) &&
			((ast_format_get_maximum_ms(format) < max_packet_size) || !max_packet_size)) {
			max_packet_size = ast_format_get_maximum_ms(format);
		}
		ao2_ref(format, -1);
	}

	/* Add non-codec formats */
	if (media_type != AST_MEDIA_TYPE_VIDEO) {
		for (index = 1LL; index <= AST_RTP_MAX; index <<= 1) {
			if (!(noncodec & index) || (rtp_code = ast_rtp_codecs_payload_code(ast_rtp_instance_get_codecs(session_media->rtp),
											   0, NULL, index)) == -1) {
				continue;
			}

			if (!(attr = generate_rtpmap_attr(media, pool, rtp_code, 0, NULL, index))) {
				continue;
			}

			media->attr[media->attr_count++] = attr;

			if (index == AST_RTP_DTMF) {
				snprintf(tmp, sizeof(tmp), "%d 0-16", rtp_code);
				attr = pjmedia_sdp_attr_create(pool, "fmtp", pj_cstr(&stmp, tmp));
				media->attr[media->attr_count++] = attr;
			}
		}
	}

	/* If no formats were actually added to the media stream don't add it to the SDP */
	if (!media->desc.fmt_count) {
		return 1;
	}

	/* If ptime is set add it as an attribute */
	min_packet_size = ast_rtp_codecs_get_framing(ast_rtp_instance_get_codecs(session_media->rtp));
	if (!min_packet_size) {
		min_packet_size = ast_format_cap_get_framing(caps);
	}
	if (min_packet_size) {
		snprintf(tmp, sizeof(tmp), "%d", min_packet_size);
		attr = pjmedia_sdp_attr_create(pool, "ptime", pj_cstr(&stmp, tmp));
		media->attr[media->attr_count++] = attr;
	}

	if (max_packet_size) {
		snprintf(tmp, sizeof(tmp), "%d", max_packet_size);
		attr = pjmedia_sdp_attr_create(pool, "maxptime", pj_cstr(&stmp, tmp));
		media->attr[media->attr_count++] = attr;
	}

	/* Add the sendrecv attribute - we purposely don't keep track because pjmedia-sdp will automatically change our offer for us */
	attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr);
	attr->name = !session_media->locally_held ? STR_SENDRECV : STR_SENDONLY;
	media->attr[media->attr_count++] = attr;

	/* Add the media stream to the SDP */
	sdp->media[sdp->media_count++] = media;

	return 1;
}

static int apply_negotiated_sdp_stream(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
				       const struct pjmedia_sdp_session *local, const struct pjmedia_sdp_media *local_stream,
				       const struct pjmedia_sdp_session *remote, const struct pjmedia_sdp_media *remote_stream)
{
	RAII_VAR(struct ast_sockaddr *, addrs, NULL, ast_free_ptr);
	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
	char host[NI_MAXHOST];
	int fdno, res;

	if (!session->channel) {
		return 1;
	}

	if (!local_stream->desc.port || !remote_stream->desc.port) {
		return 1;
	}

	/* Ensure incoming transport is compatible with the endpoint's configuration */
	if (!session->endpoint->media.rtp.use_received_transport &&
		check_endpoint_media_transport(session->endpoint, remote_stream) == AST_SIP_MEDIA_TRANSPORT_INVALID) {
		return -1;
	}

	/* Create an RTP instance if need be */
	if (!session_media->rtp && create_rtp(session, session_media, session->endpoint->media.rtp.ipv6)) {
		return -1;
	}

	res = setup_media_encryption(session, session_media, remote, remote_stream);
	if (!session->endpoint->media.rtp.encryption_optimistic && res) {
		/* If optimistic encryption is disabled and crypto should have been enabled but was not
		 * this session must fail.
		 */
		return -1;
	}

	if (!remote_stream->conn && !remote->conn) {
		return 1;
	}

	ast_copy_pj_str(host, remote_stream->conn ? &remote_stream->conn->addr : &remote->conn->addr, sizeof(host));

	/* Ensure that the address provided is valid */
	if (ast_sockaddr_resolve(&addrs, host, PARSE_PORT_FORBID, AST_AF_UNSPEC) <= 0) {
		/* The provided host was actually invalid so we error out this negotiation */
		return -1;
	}

	/* Apply connection information to the RTP instance */
	ast_sockaddr_set_port(addrs, remote_stream->desc.port);
	ast_rtp_instance_set_remote_address(session_media->rtp, addrs);
	if (set_caps(session, session_media, local_stream)) {
		return 1;
	}

	if ((fdno = media_type_to_fdno(media_type)) < 0) {
		return -1;
	}
	ast_channel_set_fd(session->channel, fdno, ast_rtp_instance_fd(session_media->rtp, 0));
	ast_channel_set_fd(session->channel, fdno + 1, ast_rtp_instance_fd(session_media->rtp, 1));

	/* If ICE support is enabled find all the needed attributes */
	process_ice_attributes(session, session_media, remote, remote_stream);

	/* Ensure the RTP instance is active */
	ast_rtp_instance_activate(session_media->rtp);

	/* audio stream handles music on hold */
	if (media_type != AST_MEDIA_TYPE_AUDIO) {
		if ((pjmedia_sdp_neg_was_answer_remote(session->inv_session->neg) == PJ_FALSE)
			&& (session->inv_session->state == PJSIP_INV_STATE_CONFIRMED)) {
			ast_queue_control(session->channel, AST_CONTROL_UPDATE_RTP_PEER);
		}
		return 1;
	}

	if (ast_sockaddr_isnull(addrs) ||
		ast_sockaddr_is_any(addrs) ||
		pjmedia_sdp_media_find_attr2(remote_stream, "sendonly", NULL) ||
		pjmedia_sdp_media_find_attr2(remote_stream, "inactive", NULL)) {
		if (!session_media->remotely_held) {
			/* The remote side has put us on hold */
			ast_queue_hold(session->channel, session->endpoint->mohsuggest);
			ast_rtp_instance_stop(session_media->rtp);
			ast_queue_frame(session->channel, &ast_null_frame);
			session_media->remotely_held = 1;
		}
	} else if (session_media->remotely_held) {
		/* The remote side has taken us off hold */
		ast_queue_unhold(session->channel);
		ast_queue_frame(session->channel, &ast_null_frame);
		session_media->remotely_held = 0;
	} else if ((pjmedia_sdp_neg_was_answer_remote(session->inv_session->neg) == PJ_FALSE)
		&& (session->inv_session->state == PJSIP_INV_STATE_CONFIRMED)) {
		ast_queue_control(session->channel, AST_CONTROL_UPDATE_RTP_PEER);
	}

	/* This purposely resets the encryption to the configured in case it gets added later */
	session_media->encryption = session->endpoint->media.rtp.encryption;

	return 1;
}

/*! \brief Function which updates the media stream with external media address, if applicable */
static void change_outgoing_sdp_stream_media_address(pjsip_tx_data *tdata, struct pjmedia_sdp_media *stream, struct ast_sip_transport *transport)
{
	char host[NI_MAXHOST];
	struct ast_sockaddr addr = { { 0, } };

	/* If the stream has been rejected there will be no connection line */
	if (!stream->conn) {
		return;
	}

	ast_copy_pj_str(host, &stream->conn->addr, sizeof(host));
	ast_sockaddr_parse(&addr, host, PARSE_PORT_FORBID);

	/* Is the address within the SDP inside the same network? */
	if (ast_apply_ha(transport->localnet, &addr) == AST_SENSE_ALLOW) {
		return;
	}

	pj_strdup2(tdata->pool, &stream->conn->addr, transport->external_media_address);
}

/*! \brief Function which destroys the RTP instance when session ends */
static void stream_destroy(struct ast_sip_session_media *session_media)
{
	if (session_media->rtp) {
		ast_rtp_instance_stop(session_media->rtp);
		ast_rtp_instance_destroy(session_media->rtp);
	}
	session_media->rtp = NULL;
}

/*! \brief SDP handler for 'audio' media stream */
static struct ast_sip_session_sdp_handler audio_sdp_handler = {
	.id = STR_AUDIO,
	.negotiate_incoming_sdp_stream = negotiate_incoming_sdp_stream,
	.create_outgoing_sdp_stream = create_outgoing_sdp_stream,
	.apply_negotiated_sdp_stream = apply_negotiated_sdp_stream,
	.change_outgoing_sdp_stream_media_address = change_outgoing_sdp_stream_media_address,
	.stream_destroy = stream_destroy,
};

/*! \brief SDP handler for 'video' media stream */
static struct ast_sip_session_sdp_handler video_sdp_handler = {
	.id = STR_VIDEO,
	.negotiate_incoming_sdp_stream = negotiate_incoming_sdp_stream,
	.create_outgoing_sdp_stream = create_outgoing_sdp_stream,
	.apply_negotiated_sdp_stream = apply_negotiated_sdp_stream,
	.change_outgoing_sdp_stream_media_address = change_outgoing_sdp_stream_media_address,
	.stream_destroy = stream_destroy,
};

static int video_info_incoming_request(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
{
	struct pjsip_transaction *tsx;
	pjsip_tx_data *tdata;

	if (!session->channel
		|| !ast_sip_is_content_type(&rdata->msg_info.msg->body->content_type,
			"application",
			"media_control+xml")) {
		return 0;
	}

	tsx = pjsip_rdata_get_tsx(rdata);

	ast_queue_control(session->channel, AST_CONTROL_VIDUPDATE);

	if (pjsip_dlg_create_response(session->inv_session->dlg, rdata, 200, NULL, &tdata) == PJ_SUCCESS) {
		pjsip_dlg_send_response(session->inv_session->dlg, tsx, tdata);
	}

	return 0;
}

static struct ast_sip_session_supplement video_info_supplement = {
	.method = "INFO",
	.incoming_request = video_info_incoming_request,
};

/*! \brief Unloads the sdp RTP/AVP module from Asterisk */
static int unload_module(void)
{
	ast_sip_session_unregister_supplement(&video_info_supplement);
	ast_sip_session_unregister_sdp_handler(&video_sdp_handler, STR_VIDEO);
	ast_sip_session_unregister_sdp_handler(&audio_sdp_handler, STR_AUDIO);

	if (sched) {
		ast_sched_context_destroy(sched);
	}

	return 0;
}

/*!
 * \brief Load the module
 *
 * Module loading including tests for configuration or dependencies.
 * This function can return AST_MODULE_LOAD_FAILURE, AST_MODULE_LOAD_DECLINE,
 * or AST_MODULE_LOAD_SUCCESS. If a dependency or environment variable fails
 * tests return AST_MODULE_LOAD_FAILURE. If the module can not load the
 * configuration file or other non-critical problem return
 * AST_MODULE_LOAD_DECLINE. On success return AST_MODULE_LOAD_SUCCESS.
 */
static int load_module(void)
{
	CHECK_PJSIP_SESSION_MODULE_LOADED();

	ast_sockaddr_parse(&address_ipv4, "0.0.0.0", 0);
	ast_sockaddr_parse(&address_ipv6, "::", 0);

	if (!(sched = ast_sched_context_create())) {
		ast_log(LOG_ERROR, "Unable to create scheduler context.\n");
		goto end;
	}

	if (ast_sched_start_thread(sched)) {
		ast_log(LOG_ERROR, "Unable to create scheduler context thread.\n");
		goto end;
	}

	if (ast_sip_session_register_sdp_handler(&audio_sdp_handler, STR_AUDIO)) {
		ast_log(LOG_ERROR, "Unable to register SDP handler for %s stream type\n", STR_AUDIO);
		goto end;
	}

	if (ast_sip_session_register_sdp_handler(&video_sdp_handler, STR_VIDEO)) {
		ast_log(LOG_ERROR, "Unable to register SDP handler for %s stream type\n", STR_VIDEO);
		goto end;
	}

	ast_sip_session_register_supplement(&video_info_supplement);

	return AST_MODULE_LOAD_SUCCESS;
end:
	unload_module();

	return AST_MODULE_LOAD_FAILURE;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP SDP RTP/AVP stream handler",
		.support_level = AST_MODULE_SUPPORT_CORE,
		.load = load_module,
		.unload = unload_module,
		.load_pri = AST_MODPRI_CHANNEL_DRIVER,
	);