Revert "bridges/bridge_t38: Add a bridging module for managing T.38 state"
authorMatt Jordan <mjordan@digium.com>
Sun, 6 Dec 2015 22:35:24 +0000 (16:35 -0600)
committerMatt Jordan <mjordan@digium.com>
Sun, 6 Dec 2015 22:35:24 +0000 (16:35 -0600)
This reverts commit f42d22d3a1ca5c8ea73df99a50c6a28caa8f8749.

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
bridges/bridge_t38.c [deleted file]

diff --git a/CHANGES b/CHANGES
index 1180fbf..dfb1590 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -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
diff --git a/bridges/bridge_t38.c b/bridges/bridge_t38.c
deleted file mode 100644 (file)
index eb4e453..0000000
+++ /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_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");