Merge phase 1 support for the new bridging architecture.

This commit brings in the bridging core, bridging technologies,
and the ConfBridge application.

For usage information on the ConfBridge application please see
the output of "core show application ConfBridge" from the CLI.

For API documentation please see the doxygen page describing the
architecture and the documentation for each API call.

Review: http://reviewboard.digium.com/r/93/


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@180369 f38db490-d61c-443f-a65b-d21fe96a405b

4 files changed, 911 insertions, 1 deletions

diff --git a/include/asterisk/bridging.h b/include/asterisk/bridging.h
new file mode 100644
index 000000000..33fe041ca
--- /dev/null
+++ b/include/asterisk/bridging.h
@@ -0,0 +1,426 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2007 - 2009, 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
+ * \brief Channel Bridging API
+ * \author Joshua Colp <jcolp@digium.com>
+ * \ref AstBridging
+ */
+
+/*!
+ * \page AstBridging Channel Bridging API
+ *
+ * The purpose of this API is to provide an easy and flexible way to bridge
+ * channels of different technologies with different features.
+ *
+ * Bridging technologies provide the mechanism that do the actual handling
+ * of frames between channels. They provide capability information, codec information,
+ * and preference value to assist the bridging core in choosing a bridging technology when
+ * creating a bridge. Different bridges may use different bridging technologies based on needs
+ * but once chosen they all operate under the same premise; they receive frames and send frames.
+ *
+ * Bridges are a combination of bridging technology, channels, and features. A
+ * developer creates a new bridge based on what they are currently expecting to do
+ * with it or what they will do with it in the future. The bridging core determines what
+ * available bridging technology will best fit the requirements and creates a new bridge.
+ * Once created, channels can be added to the bridge in a blocking or non-blocking fashion.
+ *
+ * Features are such things as channel muting or DTMF based features such as attended transfer,
+ * blind transfer, and hangup. Feature information must be set at the most granular level, on
+ * the channel. While you can use features on a global scope the presence of a feature structure
+ * on the channel will override the global scope. An example would be having the bridge muted
+ * at global scope and attended transfer enabled on a channel. Since the channel itself is not muted
+ * it would be able to speak.
+ *
+ * Feature hooks allow a developer to tell the bridging core that when a DTMF string
+ * is received from a channel a callback should be called in their application. For
+ * example, a conference bridge application may want to provide an IVR to control various
+ * settings on the conference bridge. This can be accomplished by attaching a feature hook
+ * that calls an IVR function when a DTMF string is entered.
+ *
+ */
+
+#ifndef _ASTERISK_BRIDGING_H
+#define _ASTERISK_BRIDGING_H
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#include "asterisk/bridging_features.h"
+
+/*! \brief Capabilities for a bridge technology */
+enum ast_bridge_capability {
+	/*! Bridge is only capable of mixing 2 channels */
+	AST_BRIDGE_CAPABILITY_1TO1MIX = (1 << 1),
+	/*! Bridge is capable of mixing 2 or more channels */
+	AST_BRIDGE_CAPABILITY_MULTIMIX = (1 << 2),
+	/*! Bridge should natively bridge two channels if possible */
+	AST_BRIDGE_CAPABILITY_NATIVE = (1 << 3),
+	/*! Bridge should run using the multithreaded model */
+	AST_BRIDGE_CAPABILITY_MULTITHREADED = (1 << 4),
+	/*! Bridge should run a central bridge thread */
+	AST_BRIDGE_CAPABILITY_THREAD = (1 << 5),
+	/*! Bridge technology can do video mixing (or something along those lines) */
+	AST_BRIDGE_CAPABILITY_VIDEO = (1 << 6),
+	/*! Bridge technology can optimize things based on who is talking */
+	AST_BRIDGE_CAPABILITY_OPTIMIZE = (1 << 7),
+};
+
+/*! \brief State information about a bridged channel */
+enum ast_bridge_channel_state {
+	/*! Waiting for a signal */
+	AST_BRIDGE_CHANNEL_STATE_WAIT = 0,
+	/*! Bridged channel has ended itself (it has hung up) */
+	AST_BRIDGE_CHANNEL_STATE_END,
+	/*! Bridged channel should be hung up */
+	AST_BRIDGE_CHANNEL_STATE_HANGUP,
+	/*! Bridged channel should be removed from the bridge without being hung up */
+	AST_BRIDGE_CHANNEL_STATE_DEPART,
+	/*! Bridged channel is executing a feature hook */
+	AST_BRIDGE_CHANNEL_STATE_FEATURE,
+	/*! Bridged channel is sending a DTMF stream out */
+	AST_BRIDGE_CHANNEL_STATE_DTMF,
+};
+
+/*! \brief Return values for bridge technology write function */
+enum ast_bridge_write_result {
+	/*! Bridge technology wrote out frame fine */
+	AST_BRIDGE_WRITE_SUCCESS = 0,
+	/*! Bridge technology attempted to write out the frame but failed */
+	AST_BRIDGE_WRITE_FAILED,
+	/*! Bridge technology does not support writing out a frame of this type */
+	AST_BRIDGE_WRITE_UNSUPPORTED,
+};
+
+struct ast_bridge_technology;
+struct ast_bridge;
+
+/*!
+ * \brief Structure that contains information regarding a channel in a bridge
+ */
+struct ast_bridge_channel {
+	/*! Lock to protect this data structure */
+	ast_mutex_t lock;
+	/*! Condition, used if we want to wake up a thread waiting on the bridged channel */
+	ast_cond_t cond;
+	/*! Current bridged channel state */
+	enum ast_bridge_channel_state state;
+	/*! Asterisk channel participating in the bridge */
+	struct ast_channel *chan;
+	/*! Asterisk channel we are swapping with (if swapping) */
+	struct ast_channel *swap;
+	/*! Bridge this channel is participating in */
+	struct ast_bridge *bridge;
+	/*! Private information unique to the bridge technology */
+	void *bridge_pvt;
+	/*! Thread handling the bridged channel */
+	pthread_t thread;
+	/*! Additional file descriptors to look at */
+	int fds[4];
+	/*! Bit to indicate whether the channel is suspended from the bridge or not */
+	unsigned int suspended:1;
+	/*! Features structure for features that are specific to this channel */
+	struct ast_bridge_features *features;
+	/*! Queue of DTMF digits used for DTMF streaming */
+	char dtmf_stream_q[8];
+	/*! Linked list information */
+	AST_LIST_ENTRY(ast_bridge_channel) entry;
+};
+
+/*!
+ * \brief Structure that contains information about a bridge
+ */
+struct ast_bridge {
+	/*! Number of channels participating in the bridge */
+	int num;
+	/*! Bit to indicate that the bridge thread is waiting on channels in the bridge array */
+	unsigned int waiting:1;
+	/*! Bit to indicate the bridge thread should stop */
+	unsigned int stop:1;
+	/*! Bit to indicate the bridge thread should refresh itself */
+	unsigned int refresh:1;
+	/*! Bridge flags to tweak behavior */
+	struct ast_flags feature_flags;
+	/*! Bridge technology that is handling the bridge */
+	struct ast_bridge_technology *technology;
+	/*! Private information unique to the bridge technology */
+	void *bridge_pvt;
+	/*! Thread running the bridge */
+	pthread_t thread;
+	/*! Enabled features information */
+	struct ast_bridge_features features;
+	/*! Array of channels that the bridge thread is currently handling */
+	struct ast_channel **array;
+	/*! Number of channels in the above array */
+	size_t array_num;
+	/*! Number of channels the array can handle */
+	size_t array_size;
+	/*! Linked list of channels participating in the bridge */
+	AST_LIST_HEAD_NOLOCK(, ast_bridge_channel) channels;
+};
+
+/*! \brief Create a new bridge
+ *
+ * \param capabilities The capabilities that we require to be used on the bridge
+ * \param flags Flags that will alter the behavior of the bridge
+ *
+ * \retval a pointer to a new bridge on success
+ * \retval NULL on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge *bridge;
+ * bridge = ast_bridge_new(AST_BRIDGE_CAPABILITY_1TO1MIX, AST_BRIDGE_FLAG_DISSOLVE);
+ * \endcode
+ *
+ * This creates a simple two party bridge that will be destroyed once one of
+ * the channels hangs up.
+ */
+struct ast_bridge *ast_bridge_new(int capabilities, int flags);
+
+/*! \brief See if it is possible to create a bridge
+ *
+ * \param capabilities The capabilities that the bridge will use
+ *
+ * \retval 1 if possible
+ * \retval 0 if not possible
+ *
+ * Example usage:
+ *
+ * \code
+ * int possible = ast_bridge_check(AST_BRIDGE_CAPABILITY_1TO1MIX);
+ * \endcode
+ *
+ * This sees if it is possible to create a bridge capable of bridging two channels
+ * together.
+ */
+int ast_bridge_check(int capabilities);
+
+/*! \brief Destroy a bridge
+ *
+ * \param bridge Bridge to destroy
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_destroy(bridge);
+ * \endcode
+ *
+ * This destroys a bridge that was previously created using ast_bridge_new.
+ */
+int ast_bridge_destroy(struct ast_bridge *bridge);
+
+/*! \brief Join (blocking) a channel to a bridge
+ *
+ * \param bridge Bridge to join
+ * \param chan Channel to join
+ * \param swap Channel to swap out if swapping
+ * \param features Bridge features structure
+ *
+ * \retval state that channel exited the bridge with
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_join(bridge, chan, NULL, NULL);
+ * \endcode
+ *
+ * This adds a channel pointed to by the chan pointer to the bridge pointed to by
+ * the bridge pointer. This function will not return until the channel has been
+ * removed from the bridge, swapped out for another channel, or has hung up.
+ *
+ * If this channel will be replacing another channel the other channel can be specified
+ * in the swap parameter. The other channel will be thrown out of the bridge in an
+ * atomic fashion.
+ *
+ * If channel specific features are enabled a pointer to the features structure
+ * can be specified in the features parameter.
+ */
+enum ast_bridge_channel_state ast_bridge_join(struct ast_bridge *bridge, struct ast_channel *chan, struct ast_channel *swap, struct ast_bridge_features *features);
+
+/*! \brief Impart (non-blocking) a channel on a bridge
+ *
+ * \param bridge Bridge to impart on
+ * \param chan Channel to impart
+ * \param swap Channel to swap out if swapping
+ * \param features Bridge features structure
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_impart(bridge, chan, NULL, NULL);
+ * \endcode
+ *
+ * This adds a channel pointed to by the chan pointer to the bridge pointed to by
+ * the bridge pointer. This function will return immediately and will not wait
+ * until the channel is no longer part of the bridge.
+ *
+ * If this channel will be replacing another channel the other channel can be specified
+ * in the swap parameter. The other channel will be thrown out of the bridge in an
+ * atomic fashion.
+ *
+ * If channel specific features are enabled a pointer to the features structure
+ * can be specified in the features parameter.
+ */
+int ast_bridge_impart(struct ast_bridge *bridge, struct ast_channel *chan, struct ast_channel *swap, struct ast_bridge_features *features);
+
+/*! \brief Depart a channel from a bridge
+ *
+ * \param bridge Bridge to depart from
+ * \param chan Channel to depart
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_depart(bridge, chan);
+ * \endcode
+ *
+ * This removes the channel pointed to by the chan pointer from the bridge
+ * pointed to by the bridge pointer and gives control to the calling thread.
+ * This does not hang up the channel.
+ *
+ * \note This API call can only be used on channels that were added to the bridge
+ *       using the ast_bridge_impart API call.
+ */
+int ast_bridge_depart(struct ast_bridge *bridge, struct ast_channel *chan);
+
+/*! \brief Remove a channel from a bridge
+ *
+ * \param bridge Bridge that the channel is to be removed from
+ * \param chan Channel to remove
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_remove(bridge, chan);
+ * \endcode
+ *
+ * This removes the channel pointed to by the chan pointer from the bridge
+ * pointed to by the bridge pointer and requests that it be hung up. Control
+ * over the channel will NOT be given to the calling thread.
+ *
+ * \note This API call can be used on channels that were added to the bridge
+ *       using both ast_bridge_join and ast_bridge_impart.
+ */
+int ast_bridge_remove(struct ast_bridge *bridge, struct ast_channel *chan);
+
+/*! \brief Merge two bridges together
+ *
+ * \param bridge0 First bridge
+ * \param bridge1 Second bridge
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_merge(bridge0, bridge1);
+ * \endcode
+ *
+ * This merges the bridge pointed to by bridge1 with the bridge pointed to by bridge0.
+ * In reality all of the channels in bridge1 are simply moved to bridge0.
+ *
+ * \note The second bridge specified is not destroyed when this operation is
+ *       completed.
+ */
+int ast_bridge_merge(struct ast_bridge *bridge0, struct ast_bridge *bridge1);
+
+/*! \brief Suspend a channel temporarily from a bridge
+ *
+ * \param bridge Bridge to suspend the channel from
+ * \param chan Channel to suspend
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_suspend(bridge, chan);
+ * \endcode
+ *
+ * This suspends the channel pointed to by chan from the bridge pointed to by bridge temporarily.
+ * Control of the channel is given to the calling thread. This differs from ast_bridge_depart as
+ * the channel will not be removed from the bridge.
+ *
+ * \note This API call can be used on channels that were added to the bridge
+ *       using both ast_bridge_join and ast_bridge_impart.
+ */
+int ast_bridge_suspend(struct ast_bridge *bridge, struct ast_channel *chan);
+
+/*! \brief Unsuspend a channel from a bridge
+ *
+ * \param bridge Bridge to unsuspend the channel from
+ * \param chan Channel to unsuspend
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_unsuspend(bridge, chan);
+ * \endcode
+ *
+ * This unsuspends the channel pointed to by chan from the bridge pointed to by bridge.
+ * The bridge will go back to handling the channel once this function returns.
+ *
+ * \note You must not mess with the channel once this function returns.
+ *       Doing so may result in bad things happening.
+ */
+int ast_bridge_unsuspend(struct ast_bridge *bridge, struct ast_channel *chan);
+
+/*! \brief Change the state of a bridged channel
+ *
+ * \param bridge_channel Channel to change the state on
+ * \param new_state The new state to place the channel into
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_change_state(bridge_channel, AST_BRIDGE_CHANNEL_STATE_WAIT);
+ * \endcode
+ *
+ * This places the channel pointed to by bridge_channel into the state
+ * AST_BRIDGE_CHANNEL_STATE_WAIT.
+ *
+ * \note This API call is only meant to be used in feature hook callbacks to
+ *       make sure the channel either hangs up or returns to the bridge.
+ */
+void ast_bridge_change_state(struct ast_bridge_channel *bridge_channel, enum ast_bridge_channel_state new_state);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif /* _ASTERISK_BRIDGING_H */
diff --git a/include/asterisk/bridging_features.h b/include/asterisk/bridging_features.h
new file mode 100644
index 000000000..ee36a561c
--- /dev/null
+++ b/include/asterisk/bridging_features.h
@@ -0,0 +1,298 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2009, 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
+ * \brief Channel Bridging API
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+#ifndef _ASTERISK_BRIDGING_FEATURES_H
+#define _ASTERISK_BRIDGING_FEATURES_H
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/*! \brief Flags used for bridge features */
+enum ast_bridge_feature_flags {
+	/*! Upon hangup the bridge should be discontinued */
+	AST_BRIDGE_FLAG_DISSOLVE = (1 << 0),
+	/*! Move between bridging technologies as needed. */
+	AST_BRIDGE_FLAG_SMART = (1 << 1),
+};
+
+/*! \brief Built in features */
+enum ast_bridge_builtin_feature {
+	/*! DTMF Based Blind Transfer */
+	AST_BRIDGE_BUILTIN_BLINDTRANSFER = 0,
+	/*! DTMF Based Attended Transfer */
+	AST_BRIDGE_BUILTIN_ATTENDEDTRANSFER,
+	/*! DTMF Based Hangup Feature */
+	AST_BRIDGE_BUILTIN_HANGUP,
+	/*! End terminator for list of built in features. Must remain last. */
+	AST_BRIDGE_BUILTIN_END,
+};
+
+struct ast_bridge;
+struct ast_bridge_channel;
+
+/*!
+ * \brief Features hook callback type
+ *
+ * \param bridge The bridge that the channel is part of
+ * \param bridge_channel Channel executing the feature
+ * \param hook_pvt Private data passed in when the hook was created
+ *
+ * \retval 0 success
+ * \retval -1 failure
+ */
+typedef int (*ast_bridge_features_hook_callback)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, void *hook_pvt);
+
+/*!
+ * \brief Maximum length of a DTMF feature string
+ */
+#define MAXIMUM_DTMF_FEATURE_STRING 8
+
+/*!
+ * \brief Structure that is the essence of a features hook
+ */
+struct ast_bridge_features_hook {
+	/*! DTMF String that is examined during a feature hook lookup */
+	char dtmf[MAXIMUM_DTMF_FEATURE_STRING];
+	/*! Callback that is called when DTMF string is matched */
+	ast_bridge_features_hook_callback callback;
+	/*! Unique data that was passed into us */
+	void *hook_pvt;
+	/*! Linked list information */
+	AST_LIST_ENTRY(ast_bridge_features_hook) entry;
+};
+
+/*!
+ * \brief Structure that contains features information
+ */
+struct ast_bridge_features {
+	/*! Attached DTMF based feature hooks */
+	AST_LIST_HEAD_NOLOCK(, ast_bridge_features_hook) hooks;
+	/*! Feature flags that are enabled */
+	struct ast_flags feature_flags;
+	/*! Bit to indicate that this structure is useful and should be considered when looking for features */
+	unsigned int usable:1;
+	/*! Bit to indicate whether the channel/bridge is muted or not */
+	unsigned int mute:1;
+};
+
+/*!
+ * \brief Structure that contains configuration information for the blind transfer built in feature
+ */
+struct ast_bridge_features_blind_transfer {
+	/*! Context to use for transfers */
+	char context[AST_MAX_CONTEXT];
+};
+
+/*!
+ * \brief Structure that contains configuration information for the attended transfer built in feature
+ */
+struct ast_bridge_features_attended_transfer {
+	/*! DTMF string used to abort the transfer */
+	char abort[MAXIMUM_DTMF_FEATURE_STRING];
+	/*! DTMF string used to turn the transfer into a three way conference */
+	char threeway[MAXIMUM_DTMF_FEATURE_STRING];
+	/*! DTMF string used to complete the transfer */
+	char complete[MAXIMUM_DTMF_FEATURE_STRING];
+	/*! Context to use for transfers */
+	char context[AST_MAX_CONTEXT];
+};
+
+/*! \brief Register a handler for a built in feature
+ *
+ * \param feature The feature that the handler will be responsible for
+ * \param callback The callback function that will handle it
+ * \param dtmf Default DTMF string used to activate the feature
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_features_register(AST_BRIDGE_BUILTIN_ATTENDED_TRANSFER, bridge_builtin_attended_transfer, "*1");
+ * \endcode
+ *
+ * This registers the function bridge_builtin_attended_transfer as the function responsible for the built in
+ * attended transfer feature.
+ */
+int ast_bridge_features_register(enum ast_bridge_builtin_feature feature, ast_bridge_features_hook_callback callback, const char *dtmf);
+
+/*! \brief Unregister a handler for a built in feature
+ *
+ * \param feature The feature to unregister
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_features_unregister(AST_BRIDGE_BUILTIN_ATTENDED_TRANSFER);
+ * \endcode
+ *
+ * This unregisters the function that is handling the built in attended transfer feature.
+ */
+int ast_bridge_features_unregister(enum ast_bridge_builtin_feature feature);
+
+/*! \brief Attach a custom hook to a bridge features structure
+ *
+ * \param features Bridge features structure
+ * \param dtmf DTMF string to be activated upon
+ * \param callback Function to execute upon activation
+ * \param hook_pvt Unique data
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge_features features;
+ * ast_bridge_features_init(&features);
+ * ast_bridge_features_hook(&features, "#", pound_callback, NULL);
+ * \endcode
+ *
+ * This makes the bridging core call pound_callback if a channel that has this
+ * feature structure inputs the DTMF string '#'. A pointer to useful data may be
+ * provided to the hook_pvt parameter.
+ *
+ * \note It is important that the callback set the bridge channel state back to
+ *       AST_BRIDGE_CHANNEL_STATE_WAIT or the bridge thread will not service the channel.
+ */
+int ast_bridge_features_hook(struct ast_bridge_features *features, const char *dtmf, ast_bridge_features_hook_callback callback, void *hook_pvt);
+
+/*! \brief Enable a built in feature on a bridge features structure
+ *
+ * \param features Bridge features structure
+ * \param feature Feature to enable
+ * \param dtmf Optionally the DTMF stream to trigger the feature, if not specified it will be the default
+ * \param config Configuration structure unique to the built in type
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge_features features;
+ * ast_bridge_features_init(&features);
+ * ast_bridge_features_enable(&features, AST_BRIDGE_BUILTIN_ATTENDEDTRANSFER, NULL);
+ * \endcode
+ *
+ * This enables the attended transfer DTMF option using the default DTMF string. An alternate
+ * string may be provided using the dtmf parameter. Internally this is simply setting up a hook
+ * to a built in feature callback function.
+ */
+int ast_bridge_features_enable(struct ast_bridge_features *features, enum ast_bridge_builtin_feature feature, const char *dtmf, void *config);
+
+/*! \brief Set a flag on a bridge features structure
+ *
+ * \param features Bridge features structure
+ * \param flag Flag to enable
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge_features features;
+ * ast_bridge_features_init(&features);
+ * ast_bridge_features_set_flag(&features, AST_BRIDGE_FLAG_DISSOLVE);
+ * \endcode
+ *
+ * This sets the AST_BRIDGE_FLAG_DISSOLVE feature to be enabled on the features structure
+ * 'features'.
+ */
+int ast_bridge_features_set_flag(struct ast_bridge_features *features, enum ast_bridge_feature_flags flag);
+
+/*! \brief Initialize bridge features structure
+ *
+ * \param features Bridge featues structure
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge_features features;
+ * ast_bridge_features_init(&features);
+ * \endcode
+ *
+ * This initializes the feature structure 'features' to have nothing enabled.
+ *
+ * \note This MUST be called before enabling features or flags. Failure to do so
+ *       may result in a crash.
+ */
+int ast_bridge_features_init(struct ast_bridge_features *features);
+
+/*! \brief Clean up the contents of a bridge features structure
+ *
+ * \param features Bridge features structure
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * struct ast_bridge_features features;
+ * ast_bridge_features_init(&features);
+ * ast_bridge_features_cleanup(&features);
+ * \endcode
+ *
+ * This cleans up the feature structure 'features'.
+ *
+ * \note This MUST be called after the features structure is done being used
+ *       or a memory leak may occur.
+ */
+int ast_bridge_features_cleanup(struct ast_bridge_features *features);
+
+/*! \brief Play a DTMF stream into a bridge, optionally not to a given channel
+ *
+ * \param bridge Bridge to play stream into
+ * \param dtmf DTMF to play
+ * \param chan Channel to optionally not play to
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_dtmf_stream(bridge, "0123456789", NULL);
+ * \endcode
+ *
+ * This sends the DTMF digits '0123456789' to all channels in the bridge pointed to
+ * by the bridge pointer. Optionally a channel may be excluded by passing it's channel pointer
+ * using the chan parameter.
+ */
+int ast_bridge_dtmf_stream(struct ast_bridge *bridge, const char *dtmf, struct ast_channel *chan);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif /* _ASTERISK_BRIDGING_FEATURES_H */
diff --git a/include/asterisk/bridging_technology.h b/include/asterisk/bridging_technology.h
new file mode 100644
index 000000000..58b27a4b4
--- /dev/null
+++ b/include/asterisk/bridging_technology.h
@@ -0,0 +1,180 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2009, 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
+ * \brief Channel Bridging API
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+#ifndef _ASTERISK_BRIDGING_TECHNOLOGY_H
+#define _ASTERISK_BRIDGING_TECHNOLOGY_H
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/*! \brief Preference for choosing the bridge technology */
+enum ast_bridge_preference {
+	/*! Bridge technology should have high precedence over other bridge technologies */
+	AST_BRIDGE_PREFERENCE_HIGH = 0,
+	/*! Bridge technology is decent, not the best but should still be considered over low */
+	AST_BRIDGE_PREFERENCE_MEDIUM,
+	/*! Bridge technology is low, it should not be considered unless it is absolutely needed */
+	AST_BRIDGE_PREFERENCE_LOW,
+};
+
+/*!
+ * \brief Structure that is the essence of a bridge technology
+ */
+struct ast_bridge_technology {
+	/*! Unique name to this bridge technology */
+	const char *name;
+	/*! The capabilities that this bridge technology is capable of */
+	int capabilities;
+	/*! Preference level that should be used when determining whether to use this bridge technology or not */
+	enum ast_bridge_preference preference;
+	/*! Callback for when a bridge is being created */
+	int (*create)(struct ast_bridge *bridge);
+	/*! Callback for when a bridge is being destroyed */
+	int (*destroy)(struct ast_bridge *bridge);
+	/*! Callback for when a channel is being added to a bridge */
+	int (*join)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);
+	/*! Callback for when a channel is leaving a bridge */
+	int (*leave)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);
+	/*! Callback for when a channel is suspended from the bridge */
+	void (*suspend)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);
+	/*! Callback for when a channel is unsuspended from the bridge */
+	void (*unsuspend)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);
+	/*! Callback to see if a channel is compatible with the bridging technology */
+	int (*compatible)(struct ast_bridge_channel *bridge_channel);
+	/*! Callback for writing a frame into the bridging technology */
+	enum ast_bridge_write_result (*write)(struct ast_bridge *bridge, struct ast_bridge_channel *bridged_channel, struct ast_frame *frame);
+	/*! Callback for when a file descriptor trips */
+	int (*fd)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, int fd);
+	/*! Callback for replacement thread function */
+	int (*thread)(struct ast_bridge *bridge);
+	/*! Callback for poking a bridge thread */
+	int (*poke)(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel);
+	/*! Formats that the bridge technology supports */
+	int formats;
+	/*! Bit to indicate whether the bridge technology is currently suspended or not */
+	unsigned int suspended:1;
+	/*! Module this bridge technology belongs to. Is used for reference counting when creating/destroying a bridge. */
+	struct ast_module *mod;
+	/*! Linked list information */
+	AST_RWLIST_ENTRY(ast_bridge_technology) entry;
+};
+
+/*! \brief Register a bridge technology for use
+ *
+ * \param technology The bridge technology to register
+ * \param module The module that is registering the bridge technology
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_technology_register(&simple_bridge_tech);
+ * \endcode
+ *
+ * This registers a bridge technology declared as the structure
+ * simple_bridge_tech with the bridging core and makes it available for
+ * use when creating bridges.
+ */
+int __ast_bridge_technology_register(struct ast_bridge_technology *technology, struct ast_module *mod);
+
+/*! \brief See \ref __ast_bridge_technology_register() */
+#define ast_bridge_technology_register(technology) __ast_bridge_technology_register(technology, ast_module_info->self)
+
+/*! \brief Unregister a bridge technology from use
+ *
+ * \param technology The bridge technology to unregister
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_technology_unregister(&simple_bridge_tech);
+ * \endcode
+ *
+ * This unregisters a bridge technlogy declared as the structure
+ * simple_bridge_tech with the bridging core. It will no longer be
+ * considered when creating a new bridge.
+ */
+int ast_bridge_technology_unregister(struct ast_bridge_technology *technology);
+
+/*! \brief Feed notification that a frame is waiting on a channel into the bridging core
+ *
+ * \param bridge The bridge that the notification should influence
+ * \param bridge_channel Bridge channel the notification was received on (if known)
+ * \param chan Channel the notification was received on (if known)
+ * \param outfd File descriptor that the notification was received on (if known)
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_handle_trip(bridge, NULL, chan, -1);
+ * \endcode
+ *
+ * This tells the bridging core that a frame has been received on
+ * the channel pointed to by chan and that it should be read and handled.
+ *
+ * \note This should only be used by bridging technologies.
+ */
+void ast_bridge_handle_trip(struct ast_bridge *bridge, struct ast_bridge_channel *bridge_channel, struct ast_channel *chan, int outfd);
+
+/*! \brief Suspend a bridge technology from consideration
+ *
+ * \param technology The bridge technology to suspend
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_technology_suspend(&simple_bridge_tech);
+ * \endcode
+ *
+ * This suspends the bridge technology simple_bridge_tech from being considered
+ * when creating a new bridge. Existing bridges using the bridge technology
+ * are not affected.
+ */
+void ast_bridge_technology_suspend(struct ast_bridge_technology *technology);
+
+/*! \brief Unsuspend a bridge technology
+ *
+ * \param technology The bridge technology to unsuspend
+ *
+ * Example usage:
+ *
+ * \code
+ * ast_bridge_technology_unsuspend(&simple_bridge_tech);
+ * \endcode
+ *
+ * This makes the bridge technology simple_bridge_tech considered when
+ * creating a new bridge again.
+ */
+void ast_bridge_technology_unsuspend(struct ast_bridge_technology *technology);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif /* _ASTERISK_BRIDGING_TECHNOLOGY_H */
diff --git a/include/asterisk/channel.h b/include/asterisk/channel.h
index 39b302fc8..2d0643a0f 100644
--- a/include/asterisk/channel.h
+++ b/include/asterisk/channel.h
@@ -496,7 +496,13 @@ struct ast_channel {
 
 	unsigned short transfercapability;		/*!< ISDN Transfer Capbility - AST_FLAG_DIGITAL is not enough */
 
-	char unused_old_dtmfq[AST_MAX_EXTENSION];			/*!< (deprecated, use readq instead) Any/all queued DTMF characters */
+	union {
+		char unused_old_dtmfq[AST_MAX_EXTENSION];			/*!< (deprecated, use readq instead) Any/all queued DTMF characters */
+		struct {
+			struct ast_bridge *bridge;                                      /*!< Bridge this channel is participating in */
+		};
+	};
+
 	char context[AST_MAX_CONTEXT];			/*!< Dialplan: Current extension context */
 	char exten[AST_MAX_EXTENSION];			/*!< Dialplan: Current extension number */
 	char macrocontext[AST_MAX_CONTEXT];		/*!< Macro: Current non-macro context. See app_macro.c */