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Revert "bridges/bridge_t38: Add a bridging module for managing T.38 state"

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This reverts commit f42d22d3a1.

Unfortunately, using a bridge to manage T.38 state will cause severe deadlocks
in core_unreal/chan_local. Local channels attempt to reach across both their
peer and the peer's bridge to inspect T.38 state. Given the propensity of
Local channel chains, managing the locking situation in such a scenario is
practically infeasible.

Change-Id: I932107387c13aad2c75a7a4c1e94197a9d6d8a51
changes/71/1771/1
Matt Jordan 10 years ago
parent e26647cbac
commit 75c800eb28
2 changed files with 0 additions and 269 deletions
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@ -205,14 +205,6 @@ Queue
--- Functionality changes from Asterisk 13.6.0 to Asterisk 13.7.0 ------------
------------------------------------------------------------------------------
bridge_t38
------------------
* A new module for the bridging framework, this bridge technology acts in the
same fashion as bridge_simple, save that it helps to maintain the state of
T.38 for two channels passing a fax through Asterisk. This helps to resolve
several esoteric issues that can occur when channels are removed from a
bridge after completing a T.38 fax.
Codecs
------------------
* Added format attribute negotiation for the VP8 video codec. Format attribute

261
bridges/bridge_t38.c
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@ -1,261 +0,0 @@
/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2015, Digium, Inc.
*
* Matt Jordan <mjordan@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
*
* \brief Bridging module for maintaining T.38 state for faxing channels
*
* \author Matt Jordan <mjordan@digium.com>
*
* \ingroup bridges
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#include "asterisk.h"
ASTERISK_REGISTER_FILE()
#include "asterisk/module.h"
#include "asterisk/channel.h"
#include "asterisk/bridge.h"
#include "asterisk/bridge_technology.h"
#include "asterisk/frame.h"
/*! \brief The current state of the T.38 fax for the channels in our bridge */
struct t38_bridge_state {
/* \brief First channel in the bridge */
struct ast_bridge_channel *bc0;
/*! \brief Second channel in the bridge */
struct ast_bridge_channel *bc1;
/*! \brief T.38 state of \c bc0 */
enum ast_t38_state c0_state;
/*! \brief T.38 state of \c bc1 */
enum ast_t38_state c1_state;
};
static void t38_bridge_destroy(struct ast_bridge *bridge)
{
struct t38_bridge_state *state = bridge->tech_pvt;
ast_free(state);
bridge->tech_pvt = NULL;
}
static int t38_bridge_create(struct ast_bridge *bridge)
{
struct t38_bridge_state *state;
state = ast_calloc(1, sizeof(*state));
if (!state) {
return -1;
}
bridge->tech_pvt = state;
return 0;
}
static int t38_bridge_start(struct ast_bridge *bridge)
{
struct ast_bridge_channel *bc0 = AST_LIST_FIRST(&bridge->channels);
struct ast_bridge_channel *bc1 = AST_LIST_LAST(&bridge->channels);
struct t38_bridge_state *state = bridge->tech_pvt;
state->bc0 = bc0;
state->bc1 = bc1;
state->c0_state = ast_channel_get_t38_state(state->bc0->chan);
state->c1_state = ast_channel_get_t38_state(state->bc1->chan);
return 0;
}
static void send_termination_update(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, enum ast_t38_state chan_state)
{
/* Inform the other side that T.38 faxing is done */
struct ast_control_t38_parameters parameters = { .request_response = 0, };
if (!bridge_channel) {
return;
}
ast_debug(5, "Bridge %s T.38: Current state of %s is %d\n",
bridge->uniqueid, ast_channel_name(bridge_channel->chan), chan_state);
if (chan_state == T38_STATE_NEGOTIATING) {
parameters.request_response = AST_T38_REFUSED;
} else if (chan_state == T38_STATE_NEGOTIATED) {
parameters.request_response = AST_T38_TERMINATED;
}
if (parameters.request_response) {
struct ast_frame f = {
.frametype = AST_FRAME_CONTROL,
.subclass.integer = AST_CONTROL_T38_PARAMETERS,
.data.ptr = &parameters,
.datalen = sizeof(parameters),
};
/* When sending a termination update to a channel, the bridge is highly
* likely to be getting torn down. Queueing a frame through the bridging
* framework won't work, as the frame will likely just get tossed as the
* bridge collapses. Hence, we write directly to the channel to ensure that
* they know they aren't in a T.38 fax any longer.
*/
ast_debug(3, "Bridge %s T.38: Informing %s to switch to %d\n",
bridge->uniqueid, ast_channel_name(bridge_channel->chan), parameters.request_response);
ast_write(bridge_channel->chan, &f);
}
}
static void t38_bridge_stop(struct ast_bridge *bridge)
{
struct t38_bridge_state *state = bridge->tech_pvt;
send_termination_update(bridge, state->bc0, state->c0_state);
send_termination_update(bridge, state->bc1, state->c1_state);
}
static void t38_bridge_leave(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel)
{
struct t38_bridge_state *state = bridge->tech_pvt;
if (bridge_channel == state->bc0) {
send_termination_update(bridge, state->bc0, state->c0_state);
state->bc0 = NULL;
state->c0_state = T38_STATE_UNKNOWN;
} else {
send_termination_update(bridge, state->bc1, state->c1_state);
state->bc1 = NULL;
state->c1_state = T38_STATE_UNKNOWN;
}
}
static int t38_bridge_write(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, struct ast_frame *frame)
{
struct t38_bridge_state *state = bridge->tech_pvt;
enum ast_t38_state *c_state;
enum ast_t38_state *other_state;
if (!bridge_channel) {
return -1;
}
c_state = bridge_channel == state->bc0 ? &(state->c0_state) : &(state->c1_state);
other_state = bridge_channel == state->bc0 ? &(state->c1_state) : &(state->c0_state);
switch (frame->frametype) {
case AST_FRAME_CONTROL:
switch (frame->subclass.integer) {
case AST_CONTROL_T38_PARAMETERS:
{
struct ast_control_t38_parameters *parameters = frame->data.ptr;
switch (parameters->request_response) {
case AST_T38_REQUEST_NEGOTIATE:
*c_state = T38_STATE_NEGOTIATING;
*other_state = T38_STATE_NEGOTIATING;
break;
case AST_T38_NEGOTIATED:
*c_state = T38_STATE_NEGOTIATED;
break;
case AST_T38_TERMINATED:
case AST_T38_REQUEST_TERMINATE:
case AST_T38_REFUSED:
*c_state = T38_STATE_REJECTED;
break;
case AST_T38_REQUEST_PARMS:
default:
/* No state change */
break;
}
ast_debug(3, "Bridge %s T.38 state: %s: %d; %s: %d\n",
bridge->uniqueid, ast_channel_name(state->bc0->chan), state->c0_state,
ast_channel_name(state->bc1->chan), state->c1_state);
break;
}
default:
break;
}
break;
default:
break;
}
return ast_bridge_queue_everyone_else(bridge, bridge_channel, frame);
}
static int t38_bridge_compatible(struct ast_bridge *bridge)
{
struct ast_bridge_channel *bc0 = AST_LIST_FIRST(&bridge->channels);
struct ast_bridge_channel *bc1 = AST_LIST_LAST(&bridge->channels);
enum ast_t38_state c0_state;
enum ast_t38_state c1_state;
/* We must have two, and only two, channels in a T.38 bridge */
if (bridge->num_channels != 2) {
ast_debug(1, "Bridge '%s' can not use T.38 bridge as two channels are required\n",
bridge->uniqueid);
return 0;
}
/* We can be the bridge tech so long as one side is in the process
* of negotiating T.38
*/
c0_state = ast_channel_get_t38_state(bc0->chan);
c1_state = ast_channel_get_t38_state(bc1->chan);
if (c0_state != T38_STATE_NEGOTIATING && c0_state != T38_STATE_NEGOTIATED
&& c1_state != T38_STATE_NEGOTIATING && c1_state != T38_STATE_NEGOTIATED) {
ast_debug(1, "Bridge '%s' can not use T.38 bridge: channel %s has T.38 state %d; channel %s has T.38 state %d\n",
bridge->uniqueid, ast_channel_name(bc0->chan), c0_state, ast_channel_name(bc1->chan), c1_state);
return 0;
}
return 1;
}
static struct ast_bridge_technology t38_bridge = {
.name = "t38_bridge",
.capabilities = AST_BRIDGE_CAPABILITY_1TO1MIX,
.preference = AST_BRIDGE_PREFERENCE_BASE_1TO1MIX + 1,
.create = t38_bridge_create,
.destroy = t38_bridge_destroy,
.start = t38_bridge_start,
.stop = t38_bridge_stop,
.leave = t38_bridge_leave,
.write = t38_bridge_write,
.compatible = t38_bridge_compatible,
};
static int unload_module(void)
{
ast_bridge_technology_unregister(&t38_bridge);
return 0;
}
static int load_module(void)
{
if (ast_bridge_technology_register(&t38_bridge)) {
return AST_MODULE_LOAD_DECLINE;
}
return AST_MODULE_LOAD_SUCCESS;
}
AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Two channel bridging module that maintains T.38 state");
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