The large GULP->PJSIP renaming effort.

The general gist is to have a clear boundary between old SIP stuff
and new SIP stuff by having the word "SIP" for old stuff and "PJSIP"
for new stuff. Here's a brief rundown of the changes:

* The word "Gulp" in dialstrings, functions, and CLI commands is now
  "PJSIP"
* chan_gulp.c is now chan_pjsip.c
* Function names in chan_gulp.c that were "gulp_*" are now "chan_pjsip_*"
* All files that were "res_sip*" are now "res_pjsip*"
* The "res_sip" directory is now "res_pjsip"
* Files in the "res_pjsip" directory that began with "sip_*" are now "pjsip_*"
* The configuration file is now "pjsip.conf" instead of "res_sip.conf"
* The module info for all PJSIP-related files now uses "PJSIP" instead of "SIP"
* CLI and AMI commands created by Asterisk's PJSIP modules now have "pjsip" as
the starting word instead of "sip"



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@395764 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 853 insertions, 0 deletions

diff --git a/res/res_pjsip_t38.c b/res/res_pjsip_t38.c
new file mode 100644
index 000000000..eb5d8eaec
--- /dev/null
+++ b/res/res_pjsip_t38.c
@@ -0,0 +1,853 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2013, Digium, Inc.
+ *
+ * Joshua Colp <jcolp@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 T.38 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/udptl.h"
+#include "asterisk/netsock2.h"
+#include "asterisk/channel.h"
+#include "asterisk/acl.h"
+
+#include "asterisk/res_pjsip.h"
+#include "asterisk/res_pjsip_session.h"
+
+/*! \brief The number of seconds after receiving a T.38 re-invite before automatically rejecting it */
+#define T38_AUTOMATIC_REJECTION_SECONDS 5
+
+/*! \brief Address for IPv4 UDPTL */
+static struct ast_sockaddr address_ipv4;
+
+/*! \brief Address for IPv6 UDPTL */
+static struct ast_sockaddr address_ipv6;
+
+/*! \brief T.38 state information */
+struct t38_state {
+	/*! \brief Current state */
+	enum ast_sip_session_t38state state;
+	/*! \brief Our T.38 parameters */
+	struct ast_control_t38_parameters our_parms;
+	/*! \brief Their T.38 parameters */
+	struct ast_control_t38_parameters their_parms;
+	/*! \brief Timer entry for automatically rejecting an inbound re-invite */
+	pj_timer_entry timer;
+};
+
+/*! \brief Destructor for T.38 state information */
+static void t38_state_destroy(void *obj)
+{
+	ast_free(obj);
+}
+
+/*! \brief Datastore for attaching T.38 state information */
+static const struct ast_datastore_info t38_datastore = {
+	.type = "t38",
+	.destroy = t38_state_destroy,
+};
+
+/*! \brief Structure for T.38 parameters task data */
+struct t38_parameters_task_data {
+	/*! \brief Session itself */
+	struct ast_sip_session *session;
+	/*! \brief T.38 control frame */
+	struct ast_frame *frame;
+};
+
+/*! \brief Destructor for T.38 data */
+static void t38_parameters_task_data_destroy(void *obj)
+{
+	struct t38_parameters_task_data *data = obj;
+
+	ao2_cleanup(data->session);
+
+	if (data->frame) {
+		ast_frfree(data->frame);
+	}
+}
+
+/*! \brief Allocator for T.38 data */
+static struct t38_parameters_task_data *t38_parameters_task_data_alloc(struct ast_sip_session *session,
+	struct ast_frame *frame)
+{
+	struct t38_parameters_task_data *data = ao2_alloc(sizeof(*data), t38_parameters_task_data_destroy);
+
+	if (!data) {
+		return NULL;
+	}
+
+	data->session = session;
+	ao2_ref(session, +1);
+
+	if (!(data->frame = ast_frdup(frame))) {
+		ao2_cleanup(data);
+		return NULL;
+	}
+
+	return data;
+}
+
+/*! \brief Helper function for changing the T.38 state */
+static void t38_change_state(struct ast_sip_session *session, struct ast_sip_session_media *session_media,
+	struct t38_state *state, enum ast_sip_session_t38state new_state)
+{
+	enum ast_sip_session_t38state old_state = session->t38state;
+	struct ast_control_t38_parameters parameters = { .request_response = 0, };
+	pj_time_val delay = { .sec = T38_AUTOMATIC_REJECTION_SECONDS };
+
+	if (old_state == new_state) {
+		return;
+	}
+
+	session->t38state = new_state;
+	ast_debug(2, "T.38 state changed to '%d' from '%d' on channel '%s'\n", new_state, old_state, ast_channel_name(session->channel));
+
+	if (pj_timer_heap_cancel(pjsip_endpt_get_timer_heap(ast_sip_get_pjsip_endpoint()), &state->timer)) {
+		ast_debug(2, "Automatic T.38 rejection on channel '%s' terminated\n", ast_channel_name(session->channel));
+		ao2_ref(session, -1);
+	}
+
+	if (!session->channel) {
+		return;
+	}
+
+	switch (new_state) {
+	case T38_PEER_REINVITE:
+		ao2_ref(session, +1);
+		if (pjsip_endpt_schedule_timer(ast_sip_get_pjsip_endpoint(), &state->timer, &delay) != PJ_SUCCESS) {
+			ast_log(LOG_WARNING, "Scheduling of automatic T.38 rejection for channel '%s' failed\n",
+				ast_channel_name(session->channel));
+			ao2_ref(session, -1);
+		}
+		parameters = state->their_parms;
+		parameters.max_ifp = ast_udptl_get_far_max_ifp(session_media->udptl);
+		parameters.request_response = AST_T38_REQUEST_NEGOTIATE;
+		ast_udptl_set_tag(session_media->udptl, "%s", ast_channel_name(session->channel));
+		break;
+	case T38_ENABLED:
+		parameters = state->their_parms;
+		parameters.max_ifp = ast_udptl_get_far_max_ifp(session_media->udptl);
+		parameters.request_response = AST_T38_NEGOTIATED;
+		ast_udptl_set_tag(session_media->udptl, "%s", ast_channel_name(session->channel));
+		break;
+	case T38_REJECTED:
+	case T38_DISABLED:
+		if (old_state == T38_ENABLED) {
+			parameters.request_response = AST_T38_TERMINATED;
+		} else if (old_state == T38_LOCAL_REINVITE) {
+			parameters.request_response = AST_T38_REFUSED;
+		}
+		break;
+	case T38_LOCAL_REINVITE:
+		/* wait until we get a peer response before responding to local reinvite */
+		break;
+	}
+
+	if (parameters.request_response) {
+		ast_queue_control_data(session->channel, AST_CONTROL_T38_PARAMETERS, &parameters, sizeof(parameters));
+	}
+}
+
+/*! \brief Task function which rejects a T.38 re-invite and resumes handling it */
+static int t38_automatic_reject(void *obj)
+{
+	RAII_VAR(struct ast_sip_session *, session, obj, ao2_cleanup);
+	RAII_VAR(struct ast_datastore *, datastore, ast_sip_session_get_datastore(session, "t38"), ao2_cleanup);
+	RAII_VAR(struct ast_sip_session_media *, session_media, ao2_find(session->media, "image", OBJ_KEY), ao2_cleanup);
+
+	if (!datastore) {
+		return 0;
+	}
+
+	ast_debug(2, "Automatically rejecting T.38 request on channel '%s'\n", ast_channel_name(session->channel));
+
+	t38_change_state(session, session_media, datastore->data, T38_REJECTED);
+	ast_sip_session_resume_reinvite(session);
+
+	return 0;
+}
+
+/*! \brief Timer entry callback which queues a task to reject a T.38 re-invite and resume handling it */
+static void t38_automatic_reject_timer_cb(pj_timer_heap_t *timer_heap, struct pj_timer_entry *entry)
+{
+	struct ast_sip_session *session = entry->user_data;
+
+	if (ast_sip_push_task(session->serializer, t38_automatic_reject, session)) {
+		ao2_ref(session, -1);
+	}
+}
+
+/*! \brief Helper function which retrieves or allocates a T.38 state information datastore */
+static struct t38_state *t38_state_get_or_alloc(struct ast_sip_session *session)
+{
+	RAII_VAR(struct ast_datastore *, datastore, ast_sip_session_get_datastore(session, "t38"), ao2_cleanup);
+	struct t38_state *state;
+
+	/* While the datastore refcount is decremented this is operating in the serializer so it will remain valid regardless */
+	if (datastore) {
+		return datastore->data;
+	}
+
+	if (!(datastore = ast_sip_session_alloc_datastore(&t38_datastore, "t38")) ||
+		!(datastore->data = ast_calloc(1, sizeof(struct t38_state))) ||
+		ast_sip_session_add_datastore(session, datastore)) {
+		return NULL;
+	}
+
+	state = datastore->data;
+
+	/* This will get bumped up before scheduling */
+	state->timer.user_data = session;
+	state->timer.cb = t38_automatic_reject_timer_cb;
+
+	datastore->data = state;
+
+	return state;
+}
+
+/*! \brief Initializes UDPTL support on a session, only done when actually needed */
+static int t38_initialize_session(struct ast_sip_session *session, struct ast_sip_session_media *session_media)
+{
+	if (session_media->udptl) {
+		return 0;
+	}
+
+	if (!(session_media->udptl = ast_udptl_new_with_bindaddr(NULL, NULL, 0,
+		session->endpoint->media.t38.ipv6 ? &address_ipv6 : &address_ipv4))) {
+		return -1;
+	}
+
+	ast_channel_set_fd(session->channel, 5, ast_udptl_fd(session_media->udptl));
+	ast_udptl_set_error_correction_scheme(session_media->udptl, session->endpoint->media.t38.error_correction);
+	ast_udptl_setnat(session_media->udptl, session->endpoint->media.t38.nat);
+
+	return 0;
+}
+
+/*! \brief Callback for when T.38 reinvite SDP is created */
+static int t38_reinvite_sdp_cb(struct ast_sip_session *session, pjmedia_sdp_session *sdp)
+{
+	int stream;
+
+	/* Move the image media stream to the front and have it as the only stream, pjmedia will fill in
+	 * dummy streams for the rest
+	 */
+	for (stream = 0; stream < sdp->media_count++; ++stream) {
+		if (!pj_strcmp2(&sdp->media[stream]->desc.media, "image")) {
+			sdp->media[0] = sdp->media[stream];
+			sdp->media_count = 1;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+/*! \brief Callback for when a response is received for a T.38 re-invite */
+static int t38_reinvite_response_cb(struct ast_sip_session *session, pjsip_rx_data *rdata)
+{
+	struct pjsip_status_line status = rdata->msg_info.msg->line.status;
+	struct t38_state *state;
+	RAII_VAR(struct ast_sip_session_media *, session_media, NULL, ao2_cleanup);
+
+	if (status.code == 100) {
+		return 0;
+	}
+
+	if (!(state = t38_state_get_or_alloc(session)) ||
+		!(session_media = ao2_find(session->media, "image", OBJ_KEY))) {
+		ast_log(LOG_WARNING, "Received response to T.38 re-invite on '%s' but state unavailable\n",
+			ast_channel_name(session->channel));
+		return 0;
+	}
+
+	t38_change_state(session, session_media, state, (status.code == 200) ? T38_ENABLED : T38_REJECTED);
+
+	return 0;
+}
+
+/*! \brief Task for reacting to T.38 control frame */
+static int t38_interpret_parameters(void *obj)
+{
+	RAII_VAR(struct t38_parameters_task_data *, data, obj, ao2_cleanup);
+	const struct ast_control_t38_parameters *parameters = data->frame->data.ptr;
+	struct t38_state *state = t38_state_get_or_alloc(data->session);
+	RAII_VAR(struct ast_sip_session_media *, session_media, ao2_find(data->session->media, "image", OBJ_KEY), ao2_cleanup);
+
+	/* Without session media or state we can't interpret parameters */
+	if (!session_media || !state) {
+		return 0;
+	}
+
+	switch (parameters->request_response) {
+	case AST_T38_NEGOTIATED:
+	case AST_T38_REQUEST_NEGOTIATE:         /* Request T38 */
+		/* Negotiation can not take place without a valid max_ifp value. */
+		if (!parameters->max_ifp) {
+			t38_change_state(data->session, session_media, state, T38_REJECTED);
+			if (data->session->t38state == T38_PEER_REINVITE) {
+				ast_sip_session_resume_reinvite(data->session);
+			}
+			break;
+		} else if (data->session->t38state == T38_PEER_REINVITE) {
+			state->our_parms = *parameters;
+			/* modify our parameters to conform to the peer's parameters,
+			 * based on the rules in the ITU T.38 recommendation
+			 */
+			if (!state->their_parms.fill_bit_removal) {
+				state->our_parms.fill_bit_removal = 0;
+			}
+			if (!state->their_parms.transcoding_mmr) {
+				state->our_parms.transcoding_mmr = 0;
+			}
+			if (!state->their_parms.transcoding_jbig) {
+				state->our_parms.transcoding_jbig = 0;
+			}
+			state->our_parms.version = MIN(state->our_parms.version, state->their_parms.version);
+			state->our_parms.rate_management = state->their_parms.rate_management;
+			ast_udptl_set_local_max_ifp(session_media->udptl, state->our_parms.max_ifp);
+			t38_change_state(data->session, session_media, state, T38_ENABLED);
+			ast_sip_session_resume_reinvite(data->session);
+		} else if (data->session->t38state != T38_ENABLED) {
+			if (t38_initialize_session(data->session, session_media)) {
+				break;
+			}
+			state->our_parms = *parameters;
+			ast_udptl_set_local_max_ifp(session_media->udptl, state->our_parms.max_ifp);
+			t38_change_state(data->session, session_media, state, T38_LOCAL_REINVITE);
+			ast_sip_session_refresh(data->session, NULL, t38_reinvite_sdp_cb, t38_reinvite_response_cb,
+				AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1);
+		}
+		break;
+	case AST_T38_TERMINATED:
+	case AST_T38_REFUSED:
+	case AST_T38_REQUEST_TERMINATE:         /* Shutdown T38 */
+		if (data->session->t38state == T38_PEER_REINVITE) {
+			t38_change_state(data->session, session_media, state, T38_REJECTED);
+			ast_sip_session_resume_reinvite(data->session);
+		} else if (data->session->t38state == T38_ENABLED) {
+			t38_change_state(data->session, session_media, state, T38_DISABLED);
+			ast_sip_session_refresh(data->session, NULL, NULL, NULL, AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1);
+		}
+		break;
+	case AST_T38_REQUEST_PARMS: {		/* Application wants remote's parameters re-sent */
+		struct ast_control_t38_parameters parameters = state->their_parms;
+
+		if (data->session->t38state == T38_PEER_REINVITE) {
+			parameters.max_ifp = ast_udptl_get_far_max_ifp(session_media->udptl);
+			parameters.request_response = AST_T38_REQUEST_NEGOTIATE;
+			ast_queue_control_data(data->session->channel, AST_CONTROL_T38_PARAMETERS, &parameters, sizeof(parameters));
+		}
+		break;
+	}
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+/*! \brief Frame hook callback for writing */
+static struct ast_frame *t38_framehook_write(struct ast_sip_session *session, struct ast_frame *f)
+{
+	if (f->frametype == AST_FRAME_CONTROL && f->subclass.integer == AST_CONTROL_T38_PARAMETERS &&
+		session->endpoint->media.t38.enabled) {
+		struct t38_parameters_task_data *data = t38_parameters_task_data_alloc(session, f);
+
+		if (!data) {
+			return f;
+		}
+
+		if (ast_sip_push_task(session->serializer, t38_interpret_parameters, data)) {
+			ao2_ref(data, -1);
+		}
+	} else if (f->frametype == AST_FRAME_MODEM) {
+		RAII_VAR(struct ast_sip_session_media *, session_media, NULL, ao2_cleanup);
+
+		if ((session_media = ao2_find(session->media, "image", OBJ_KEY)) &&
+			session_media->udptl) {
+			ast_udptl_write(session_media->udptl, f);
+		}
+	}
+
+	return f;
+}
+
+/*! \brief Frame hook callback for reading */
+static struct ast_frame *t38_framehook_read(struct ast_sip_session *session, struct ast_frame *f)
+{
+	if (ast_channel_fdno(session->channel) == 5) {
+		RAII_VAR(struct ast_sip_session_media *, session_media, NULL, ao2_cleanup);
+
+		if ((session_media = ao2_find(session->media, "image", OBJ_KEY)) &&
+			session_media->udptl) {
+			f = ast_udptl_read(session_media->udptl);
+		}
+	}
+
+	return f;
+}
+
+/*! \brief Frame hook callback for T.38 related stuff */
+static struct ast_frame *t38_framehook(struct ast_channel *chan, struct ast_frame *f,
+	enum ast_framehook_event event, void *data)
+{
+	struct ast_sip_channel_pvt *channel = ast_channel_tech_pvt(chan);
+
+	if (event == AST_FRAMEHOOK_EVENT_READ) {
+		f = t38_framehook_read(channel->session, f);
+	} else if (event == AST_FRAMEHOOK_EVENT_WRITE) {
+		f = t38_framehook_write(channel->session, f);
+	}
+
+	return f;
+}
+
+/*! \brief Function called to attach T.38 framehook to channel when appropriate */
+static void t38_attach_framehook(struct ast_sip_session *session)
+{
+	static struct ast_framehook_interface hook = {
+		.version = AST_FRAMEHOOK_INTERFACE_VERSION,
+		.event_cb = t38_framehook,
+	};
+
+	if ((ast_channel_state(session->channel) == AST_STATE_UP) || !session->endpoint->media.t38.enabled) {
+		return;
+	}
+
+	if (ast_framehook_attach(session->channel, &hook) < 0) {
+		ast_log(LOG_WARNING, "Could not attach T.38 Frame hook to channel, T.38 will be unavailable on '%s'\n",
+			ast_channel_name(session->channel));
+	}
+}
+
+/*! \brief Function called when an INVITE goes out */
+static int t38_incoming_invite_request(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
+{
+	t38_attach_framehook(session);
+	return 0;
+}
+
+/*! \brief Function called when an INVITE comes in */
+static void t38_outgoing_invite_request(struct ast_sip_session *session, struct pjsip_tx_data *tdata)
+{
+	t38_attach_framehook(session);
+}
+
+/*! \brief Get Max T.38 Transmission rate from T38 capabilities */
+static unsigned int t38_get_rate(enum ast_control_t38_rate rate)
+{
+	switch (rate) {
+	case AST_T38_RATE_2400:
+		return 2400;
+	case AST_T38_RATE_4800:
+		return 4800;
+	case AST_T38_RATE_7200:
+		return 7200;
+	case AST_T38_RATE_9600:
+		return 9600;
+	case AST_T38_RATE_12000:
+		return 12000;
+	case AST_T38_RATE_14400:
+		return 14400;
+	default:
+		return 0;
+	}
+}
+
+/*! \brief Supplement for adding framehook to session channel */
+static struct ast_sip_session_supplement t38_supplement = {
+	.method = "INVITE",
+	.priority = AST_SIP_SESSION_SUPPLEMENT_PRIORITY_CHANNEL + 1,
+	.incoming_request = t38_incoming_invite_request,
+	.outgoing_request = t38_outgoing_invite_request,
+};
+
+/*! \brief Parse a T.38 image stream and store the attribute information */
+static void t38_interpret_sdp(struct t38_state *state, struct ast_sip_session *session, struct ast_sip_session_media *session_media,
+	const struct pjmedia_sdp_media *stream)
+{
+	unsigned int attr_i;
+
+	for (attr_i = 0; attr_i < stream->attr_count; attr_i++) {
+		pjmedia_sdp_attr *attr = stream->attr[attr_i];
+
+		if (!pj_stricmp2(&attr->name, "t38faxmaxbuffer")) {
+			/* This is purposely left empty, it is unused */
+		} else if (!pj_stricmp2(&attr->name, "t38maxbitrate") || !pj_stricmp2(&attr->name, "t38faxmaxrate")) {
+			switch (pj_strtoul(&attr->value)) {
+			case 14400:
+				state->their_parms.rate = AST_T38_RATE_14400;
+				break;
+			case 12000:
+				state->their_parms.rate = AST_T38_RATE_12000;
+				break;
+			case 9600:
+				state->their_parms.rate = AST_T38_RATE_9600;
+				break;
+			case 7200:
+				state->their_parms.rate = AST_T38_RATE_7200;
+				break;
+			case 4800:
+				state->their_parms.rate = AST_T38_RATE_4800;
+				break;
+			case 2400:
+				state->their_parms.rate = AST_T38_RATE_2400;
+				break;
+			}
+		} else if (!pj_stricmp2(&attr->name, "t38faxversion")) {
+			state->their_parms.version = pj_strtoul(&attr->value);
+		} else if (!pj_stricmp2(&attr->name, "t38faxmaxdatagram") || !pj_stricmp2(&attr->name, "t38maxdatagram")) {
+			if (session->endpoint->media.t38.maxdatagram) {
+				ast_udptl_set_far_max_datagram(session_media->udptl, session->endpoint->media.t38.maxdatagram);
+			} else {
+				ast_udptl_set_far_max_datagram(session_media->udptl, pj_strtoul(&attr->value));
+			}
+		} else if (!pj_stricmp2(&attr->name, "t38faxfillbitremoval")) {
+			state->their_parms.fill_bit_removal = 1;
+		} else if (!pj_stricmp2(&attr->name, "t38faxtranscodingmmr")) {
+			state->their_parms.transcoding_mmr = 1;
+		} else if (!pj_stricmp2(&attr->name, "t38faxtranscodingjbig")) {
+			state->their_parms.transcoding_jbig = 1;
+		} else if (!pj_stricmp2(&attr->name, "t38faxratemanagement")) {
+			if (!pj_stricmp2(&attr->value, "localTCF")) {
+				state->their_parms.rate_management = AST_T38_RATE_MANAGEMENT_LOCAL_TCF;
+			} else if (!pj_stricmp2(&attr->value, "transferredTCF")) {
+				state->their_parms.rate_management = AST_T38_RATE_MANAGEMENT_TRANSFERRED_TCF;
+			}
+		} else if (!pj_stricmp2(&attr->name, "t38faxudpec")) {
+			if (!pj_stricmp2(&attr->value, "t38UDPRedundancy")) {
+				ast_udptl_set_error_correction_scheme(session_media->udptl, UDPTL_ERROR_CORRECTION_REDUNDANCY);
+			} else if (!pj_stricmp2(&attr->value, "t38UDPFEC")) {
+				ast_udptl_set_error_correction_scheme(session_media->udptl, UDPTL_ERROR_CORRECTION_FEC);
+			} else {
+				ast_udptl_set_error_correction_scheme(session_media->udptl, UDPTL_ERROR_CORRECTION_NONE);
+			}
+		}
+
+	}
+}
+
+/*! \brief Function which defers an incoming media stream */
+static int defer_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)
+{
+	struct t38_state *state;
+
+	if (!session->endpoint->media.t38.enabled) {
+		return 0;
+	}
+
+	if (t38_initialize_session(session, session_media)) {
+		return 0;
+	}
+
+	if (!(state = t38_state_get_or_alloc(session))) {
+		return 0;
+	}
+
+	t38_interpret_sdp(state, session, session_media, stream);
+
+	/* If they are initiating the re-invite we need to defer responding until later */
+	if (session->t38state == T38_DISABLED) {
+		t38_change_state(session, session_media, state, T38_PEER_REINVITE);
+		return 1;
+	}
+
+	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)
+{
+	struct t38_state *state;
+	char host[NI_MAXHOST];
+	RAII_VAR(struct ast_sockaddr *, addrs, NULL, ast_free_ptr);
+
+	if (!session->endpoint->media.t38.enabled) {
+		return -1;
+	}
+
+	if (!(state = t38_state_get_or_alloc(session))) {
+		return -1;
+	}
+
+	if ((session->t38state == T38_REJECTED) || (session->t38state == T38_DISABLED)) {
+		t38_change_state(session, session_media, state, T38_DISABLED);
+		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_INET) <= 0) {
+		/* The provided host was actually invalid so we error out this negotiation */
+		return -1;
+	}
+
+	/* Check the address family to make sure it matches configured */
+	if ((ast_sockaddr_is_ipv6(addrs) && !session->endpoint->media.t38.ipv6) ||
+		(ast_sockaddr_is_ipv4(addrs) && session->endpoint->media.t38.ipv6)) {
+		/* The address does not match configured */
+		return -1;
+	}
+
+	return 1;
+}
+
+/*! \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_UDPTL = { "udptl", 5 };
+	static const pj_str_t STR_T38 = { "t38", 3 };
+	static const pj_str_t STR_TRANSFERREDTCF = { "transferredTCF", 14 };
+	static const pj_str_t STR_LOCALTCF = { "localTCF", 8 };
+	static const pj_str_t STR_T38UDPFEC = { "t38UDPFEC", 9 };
+	static const pj_str_t STR_T38UDPREDUNDANCY = { "t38UDPRedundancy", 16 };
+	struct t38_state *state;
+	pjmedia_sdp_media *media;
+	char hostip[PJ_INET6_ADDRSTRLEN+2];
+	struct ast_sockaddr addr;
+	char tmp[512];
+	pj_str_t stmp;
+
+	if (!session->endpoint->media.t38.enabled) {
+		return 1;
+	} else if ((session->t38state != T38_LOCAL_REINVITE) && (session->t38state != T38_PEER_REINVITE) &&
+		(session->t38state != T38_ENABLED)) {
+		return 1;
+	} else if (!(state = t38_state_get_or_alloc(session))) {
+		return -1;
+	} else if (t38_initialize_session(session, session_media)) {
+		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;
+	}
+
+	media->desc.media = pj_str(session_media->stream_type);
+	media->desc.transport = STR_UDPTL;
+
+	if (ast_strlen_zero(session->endpoint->media.external_address)) {
+		pj_sockaddr localaddr;
+
+		if (pj_gethostip(session->endpoint->media.t38.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.external_address, sizeof(hostip));
+	}
+
+	media->conn->net_type = STR_IN;
+	media->conn->addr_type = session->endpoint->media.t38.ipv6 ? STR_IP6 : STR_IP4;
+	pj_strdup2(pool, &media->conn->addr, hostip);
+	ast_udptl_get_us(session_media->udptl, &addr);
+	media->desc.port = (pj_uint16_t) ast_sockaddr_port(&addr);
+	media->desc.port_count = 1;
+	media->desc.fmt[media->desc.fmt_count++] = STR_T38;
+
+	snprintf(tmp, sizeof(tmp), "%d", state->our_parms.version);
+	media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxVersion", pj_cstr(&stmp, tmp));
+
+	snprintf(tmp, sizeof(tmp), "%d", t38_get_rate(state->our_parms.rate));
+	media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38MaxBitRate", pj_cstr(&stmp, tmp));
+
+	if (state->our_parms.fill_bit_removal) {
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxFillBitRemoval", NULL);
+	}
+
+	if (state->our_parms.transcoding_mmr) {
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxTranscodingMMR", NULL);
+	}
+
+	if (state->our_parms.transcoding_jbig) {
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxTranscodingJBIG", NULL);
+	}
+
+	switch (state->our_parms.rate_management) {
+	case AST_T38_RATE_MANAGEMENT_TRANSFERRED_TCF:
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxRateManagement", &STR_TRANSFERREDTCF);
+		break;
+	case AST_T38_RATE_MANAGEMENT_LOCAL_TCF:
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxRateManagement", &STR_LOCALTCF);
+		break;
+	}
+
+	snprintf(tmp, sizeof(tmp), "%d", ast_udptl_get_local_max_datagram(session_media->udptl));
+	media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxMaxDatagram", pj_cstr(&stmp, tmp));
+
+	switch (ast_udptl_get_error_correction_scheme(session_media->udptl)) {
+	case UDPTL_ERROR_CORRECTION_NONE:
+		break;
+	case UDPTL_ERROR_CORRECTION_FEC:
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxUdpEC", &STR_T38UDPFEC);
+		break;
+	case UDPTL_ERROR_CORRECTION_REDUNDANCY:
+		media->attr[media->attr_count++] = pjmedia_sdp_attr_create(pool, "T38FaxUdpEC", &STR_T38UDPREDUNDANCY);
+		break;
+	}
+
+	sdp->media[sdp->media_count++] = media;
+
+	return 1;
+}
+
+/*! \brief Function which applies a negotiated stream */
+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);
+	char host[NI_MAXHOST];
+	struct t38_state *state;
+
+	if (!session_media->udptl) {
+		return 0;
+	}
+
+	if (!(state = t38_state_get_or_alloc(session))) {
+		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;
+	}
+
+	ast_sockaddr_set_port(addrs, remote_stream->desc.port);
+	ast_udptl_set_peer(session_media->udptl, addrs);
+
+	t38_interpret_sdp(state, session, session_media, remote_stream);
+
+	return 0;
+}
+
+/*! \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, } };
+
+	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 UDPTL instance when session ends */
+static void stream_destroy(struct ast_sip_session_media *session_media)
+{
+	if (session_media->udptl) {
+		ast_udptl_destroy(session_media->udptl);
+	}
+}
+
+/*! \brief SDP handler for 'image' media stream */
+static struct ast_sip_session_sdp_handler image_sdp_handler = {
+	.id = "image",
+	.defer_incoming_sdp_stream = defer_incoming_sdp_stream,
+	.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 Unloads the SIP T.38 module from Asterisk */
+static int unload_module(void)
+{
+	ast_sip_session_unregister_sdp_handler(&image_sdp_handler, "image");
+	ast_sip_session_unregister_supplement(&t38_supplement);
+
+	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)
+{
+	ast_sockaddr_parse(&address_ipv4, "0.0.0.0", 0);
+	ast_sockaddr_parse(&address_ipv6, "::", 0);
+
+	if (ast_sip_session_register_supplement(&t38_supplement)) {
+		ast_log(LOG_ERROR, "Unable to register T.38 session supplement\n");
+		goto end;
+	}
+
+	if (ast_sip_session_register_sdp_handler(&image_sdp_handler, "image")) {
+		ast_log(LOG_ERROR, "Unable to register SDP handler for image stream type\n");
+		goto end;
+	}
+
+	return AST_MODULE_LOAD_SUCCESS;
+end:
+	unload_module();
+
+	return AST_MODULE_LOAD_FAILURE;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP T.38 UDPTL Support",
+		.load = load_module,
+		.unload = unload_module,
+		.load_pri = AST_MODPRI_CHANNEL_DRIVER,
+	);