funcs/func_holdintercept: Actually add the HOLD_INTERCEPT function

When ab803ec342 was committed, it accidentally forgot to actually *add* the
HOLD_INTERCEPT function. This highlights two interesting points:
* Gerrit forces you to put the patch as it is going to into the repo up for
  review, which Review Board did not. Yay Gerrit.
* No one apparently bothered to use this feature, or else they don't know about
  it. I'm going to go with the latter explanation.

ASTERISK-24922

Change-Id: Ida38278f259dd07c334a36f9b7d5475b5db72396

1 files changed, 236 insertions, 0 deletions

diff --git a/funcs/func_holdintercept.c b/funcs/func_holdintercept.c
new file mode 100644
index 000000000..3e348c1cf
--- /dev/null
+++ b/funcs/func_holdintercept.c
@@ -0,0 +1,236 @@
+/*
+ * 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 Function that intercepts HOLD frames from channels and raises events
+ *
+ * \author Matt Jordan <mjordan@digium.com>
+ *
+ * \ingroup functions
+ */
+
+/*** MODULEINFO
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+ASTERISK_REGISTER_FILE()
+
+#include "asterisk/module.h"
+#include "asterisk/channel.h"
+#include "asterisk/pbx.h"
+#include "asterisk/app.h"
+#include "asterisk/frame.h"
+#include "asterisk/stasis.h"
+#include "asterisk/stasis_channels.h"
+
+/*** DOCUMENTATION
+	<function name="HOLD_INTERCEPT" language="en_US">
+		<synopsis>
+			Intercepts hold frames on a channel and raises an event instead of passing the frame on
+		</synopsis>
+		<syntax>
+			<parameter name="action" required="true">
+				<optionlist>
+					<option name="remove">
+						<para>W/O. Removes the hold interception function.</para>
+					</option>
+					<option name="set">
+						<para>W/O. Enable hold interception on the channel. When
+						enabled, the channel will intercept any hold action that
+						is signalled from the device, and instead simply raise an
+						event (AMI/ARI) indicating that the channel wanted to put other
+						parties on hold.</para>
+					</option>
+				</optionlist>
+			</parameter>
+		</syntax>
+	</function>
+***/
+
+/*! \brief Private data structure used with the function's datastore */
+struct hold_intercept_data {
+	int framehook_id;
+};
+
+/*! \brief The channel datastore the function uses to store state */
+static const struct ast_datastore_info hold_intercept_datastore = {
+	.type = "hold_intercept",
+};
+
+/*! \internal \brief Disable hold interception on the channel */
+static int remove_hold_intercept(struct ast_channel *chan)
+{
+	struct ast_datastore *datastore = NULL;
+	struct hold_intercept_data *data;
+	SCOPED_CHANNELLOCK(chan_lock, chan);
+
+	datastore = ast_channel_datastore_find(chan, &hold_intercept_datastore, NULL);
+	if (!datastore) {
+		ast_log(AST_LOG_WARNING, "Cannot remove HOLD_INTERCEPT from %s: HOLD_INTERCEPT not currently enabled\n",
+		        ast_channel_name(chan));
+		return -1;
+	}
+	data = datastore->data;
+
+	if (ast_framehook_detach(chan, data->framehook_id)) {
+		ast_log(AST_LOG_WARNING, "Failed to remove HOLD_INTERCEPT framehook from channel %s\n",
+		        ast_channel_name(chan));
+		return -1;
+	}
+
+	if (ast_channel_datastore_remove(chan, datastore)) {
+		ast_log(AST_LOG_WARNING, "Failed to remove HOLD_INTERCEPT datastore from channel %s\n",
+		        ast_channel_name(chan));
+		return -1;
+	}
+	ast_datastore_free(datastore);
+
+	return 0;
+}
+
+/*! \brief Frame hook that is called to intercept hold/unhold */
+static struct ast_frame *hold_intercept_framehook(struct ast_channel *chan,
+	struct ast_frame *f, enum ast_framehook_event event, void *data)
+{
+	int frame_type;
+
+	if (!f || (event != AST_FRAMEHOOK_EVENT_WRITE)) {
+		return f;
+	}
+
+	if (f->frametype != AST_FRAME_CONTROL) {
+		return f;
+	}
+
+	frame_type = f->subclass.integer;
+	if (frame_type != AST_CONTROL_HOLD && frame_type != AST_CONTROL_UNHOLD) {
+		return f;
+	}
+
+	/* Munch munch */
+	ast_frfree(f);
+	f = &ast_null_frame;
+
+	ast_channel_publish_cached_blob(chan,
+		frame_type == AST_CONTROL_HOLD ? ast_channel_hold_type() : ast_channel_unhold_type(),
+		NULL);
+
+	return f;
+}
+
+/*! \brief Callback function which informs upstream if we are consuming a frame of a specific type */
+static int hold_intercept_framehook_consume(void *data, enum ast_frame_type type)
+{
+	return (type == AST_FRAME_CONTROL ? 1 : 0);
+}
+
+/*! \internal \brief Enable hold interception on the channel */
+static int set_hold_intercept(struct ast_channel *chan)
+{
+	struct ast_datastore *datastore;
+	struct hold_intercept_data *data;
+	static struct ast_framehook_interface hold_framehook_interface = {
+		.version = AST_FRAMEHOOK_INTERFACE_VERSION,
+		.event_cb = hold_intercept_framehook,
+		.consume_cb = hold_intercept_framehook_consume,
+		.disable_inheritance = 1,
+	};
+	SCOPED_CHANNELLOCK(chan_lock, chan);
+
+	datastore = ast_channel_datastore_find(chan, &hold_intercept_datastore, NULL);
+	if (datastore) {
+		ast_log(AST_LOG_WARNING, "HOLD_INTERCEPT already set on '%s'\n",
+		        ast_channel_name(chan));
+		return 0;
+	}
+
+	datastore = ast_datastore_alloc(&hold_intercept_datastore, NULL);
+	if (!datastore) {
+		return -1;
+	}
+
+	data = ast_calloc(1, sizeof(*data));
+	if (!data) {
+		ast_datastore_free(datastore);
+		return -1;
+	}
+
+	data->framehook_id = ast_framehook_attach(chan, &hold_framehook_interface);
+	if (data->framehook_id < 0) {
+		ast_log(AST_LOG_WARNING, "Failed to attach HOLD_INTERCEPT framehook to '%s'\n",
+		        ast_channel_name(chan));
+		ast_datastore_free(datastore);
+		ast_free(data);
+		return -1;
+	}
+	datastore->data = data;
+
+	ast_channel_datastore_add(chan, datastore);
+
+	return 0;
+}
+
+/*! \internal \brief HOLD_INTERCEPT write function callback */
+static int hold_intercept_fn_write(struct ast_channel *chan, const char *function,
+	char *data, const char *value)
+{
+	int res;
+
+	if (!chan) {
+		return -1;
+	}
+
+	if (ast_strlen_zero(data)) {
+		ast_log(AST_LOG_WARNING, "HOLD_INTERCEPT requires an argument\n");
+		return -1;
+	}
+
+	if (!strcasecmp(data, "set")) {
+		res = set_hold_intercept(chan);
+	} else if (!strcasecmp(data, "remove")) {
+		res = remove_hold_intercept(chan);
+	} else {
+		ast_log(AST_LOG_WARNING, "HOLD_INTERCEPT: unknown option %s\n", data);
+		res = -1;
+	}
+
+	return res;
+}
+
+/*! \brief Definition of the HOLD_INTERCEPT function */
+static struct ast_custom_function hold_intercept_function = {
+	.name = "HOLD_INTERCEPT",
+	.write = hold_intercept_fn_write,
+};
+
+/*! \internal \brief Unload the module */
+static int unload_module(void)
+{
+	return ast_custom_function_unregister(&hold_intercept_function);
+}
+
+/*! \internal \brief Load the module */
+static int load_module(void)
+{
+	return ast_custom_function_register(&hold_intercept_function) ? AST_MODULE_LOAD_FAILURE : AST_MODULE_LOAD_SUCCESS;
+}
+
+AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Hold interception dialplan function");