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

This reverts commit 6614babea27fbafbe11820ea03737dd5c4f9ecec.

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: Ic687397ffea08dfb899345a443bd990ec3d0416a

1 files changed, 0 insertions, 261 deletions

diff --git a/bridges/bridge_t38.c b/bridges/bridge_t38.c
deleted file mode 100644
index 706ed227f..000000000
--- a/bridges/bridge_t38.c
+++ /dev/null
@@ -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_FILE_VERSION(__FILE__, "$Revision$")
-
-#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");