app_signal: Add signaling applications
Adds the Signal and WaitForSignal applications, which can be used for inter-channel signaling in the dialplan. Signal supports sending a signal to other channels listening for a signal of the same name, with an optional data payload. The signal is received by all channels waiting for that named signal. ASTERISK-29810 #close Change-Id: Ic34439de3d60f8609357666a465c354d81f5fef3
This commit is contained in:
Naveen Albert
Friendly Automation
parent
2a066b6c2f
commit
78f5a41d64
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/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2022, Naveen Albert
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*
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* Naveen Albert <asterisk@phreaknet.org>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief Channel signaling applications
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*
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* \author Naveen Albert <asterisk@phreaknet.org>
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*
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* \ingroup applications
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*/
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/*** MODULEINFO
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<support_level>extended</support_level>
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***/
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#include "asterisk.h"
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#include "asterisk/file.h"
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#include "asterisk/channel.h"
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#include "asterisk/pbx.h"
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#include "asterisk/module.h"
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#include "asterisk/app.h"
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#include "asterisk/module.h"
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/*** DOCUMENTATION
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<application name="Signal" language="en_US">
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<synopsis>
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Sends a signal to any waiting channels.
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</synopsis>
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<syntax>
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<parameter name="signalname" required="true">
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<para>Name of signal to send.</para>
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</parameter>
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<parameter name="payload" required="false">
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<para>Payload data to deliver.</para>
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</parameter>
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</syntax>
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<description>
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<para>Sends a named signal to any channels that may be
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waiting for one. Acts as a producer in a simple
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message queue.</para>
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<variablelist>
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<variable name="SIGNALSTATUS">
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<value name="SUCCESS">
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Signal was successfully sent to at least
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one listener for processing.
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</value>
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<value name="FAILURE">
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Signal could not be sent or nobody
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was listening for this signal.
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</value>
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</variable>
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</variablelist>
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<example title="Send a signal named workdone">
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same => n,Signal(workdone,Work has completed)
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</example>
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</description>
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<see-also>
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<ref type="application">WaitForSignal</ref>
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</see-also>
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</application>
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<application name="WaitForSignal" language="en_US">
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<synopsis>
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Waits for a named signal on a channel.
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</synopsis>
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<syntax>
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<parameter name="signalname" required="true">
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<para>Name of signal to send.</para>
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</parameter>
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<parameter name="signaltimeout" required="false">
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<para>Maximum time, in seconds, to wait for signal.</para>
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</parameter>
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</syntax>
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<description>
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<para>Waits for <replaceable>signaltimeout</replaceable> seconds on the current
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channel to receive a signal with name <replaceable>signalname</replaceable>.
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Acts as a consumer in a simple message queue.</para>
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<para>Result of signal wait will be stored in the following variables:</para>
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<variablelist>
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<variable name="WAITFORSIGNALSTATUS">
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<value name="SIGNALED">
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Signal was received.
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</value>
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<value name="TIMEOUT">
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Timed out waiting for signal.
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</value>
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<value name="HANGUP">
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Channel hung up before signal was received.
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</value>
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</variable>
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<variable name="WAITFORSIGNALPAYLOAD">
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<para>Data payload attached to signal, if it exists</para>
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</variable>
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</variablelist>
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<example title="Wait for the workdone signal, indefinitely, and print out payload">
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same => n,WaitForSignal(workdone)
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same => n,NoOp(Received: ${WAITFORSIGNALPAYLOAD})
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</example>
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</description>
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<see-also>
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<ref type="application">Signal</ref>
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</see-also>
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</application>
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***/
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static const char * const app = "Signal";
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static const char * const app2 = "WaitForSignal";
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struct signalitem {
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ast_mutex_t lock;
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char name[AST_MAX_CONTEXT];
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int sig_alert_pipe[2];
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int watchers;
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unsigned int signaled:1;
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char *payload;
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AST_LIST_ENTRY(signalitem) entry; /*!< Next Signal item */
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};
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static AST_RWLIST_HEAD_STATIC(signals, signalitem);
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static struct signalitem *alloc_signal(const char *sname)
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{
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struct signalitem *s;
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if (!(s = ast_calloc(1, sizeof(*s)))) {
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return NULL;
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}
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ast_mutex_init(&s->lock);
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ast_copy_string(s->name, sname, sizeof(s->name));
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s->sig_alert_pipe[0] = -1;
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s->sig_alert_pipe[1] = -1;
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s->watchers = 0;
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s->payload = NULL;
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ast_alertpipe_init(s->sig_alert_pipe);
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return s;
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}
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static int dealloc_signal(struct signalitem *s)
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{
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if (s->watchers) { /* somebody is still using us... refuse to go away */
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ast_debug(1, "Signal '%s' is still being used by %d listener(s)\n", s->name, s->watchers);
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return -1;
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}
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ast_alertpipe_close(s->sig_alert_pipe);
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ast_mutex_destroy(&s->lock);
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if (s->payload) {
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ast_free(s->payload);
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s->payload = NULL;
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}
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ast_free(s);
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s = NULL;
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return 0;
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}
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static int remove_signal(char *sname)
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{
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int res = -1;
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struct signalitem *s;
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AST_LIST_TRAVERSE_SAFE_BEGIN(&signals, s, entry) {
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if (!strcmp(s->name, sname)) {
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AST_LIST_REMOVE_CURRENT(entry);
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res = dealloc_signal(s);
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ast_debug(1, "Removed signal '%s'\n", sname);
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}
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}
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AST_LIST_TRAVERSE_SAFE_END;
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return res;
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}
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static struct signalitem *get_signal(char *sname, int addnew)
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{
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struct signalitem *s = NULL;
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AST_RWLIST_WRLOCK(&signals);
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AST_LIST_TRAVERSE(&signals, s, entry) {
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if (!strcasecmp(s->name, sname)) {
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ast_debug(1, "Using existing signal item '%s'\n", sname);
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break;
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}
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}
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if (!s) {
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if (addnew) { /* signal doesn't exist, so create it */
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s = alloc_signal(sname);
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/* Totally fail if we fail to find/create an entry */
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if (s) {
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ast_debug(1, "Created new signal item '%s'\n", sname);
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AST_RWLIST_INSERT_HEAD(&signals, s, entry);
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} else {
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ast_log(LOG_WARNING, "Failed to create signal item for '%s'\n", sname);
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}
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} else {
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ast_debug(1, "Signal '%s' doesn't exist, and not creating it\n", sname);
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}
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}
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AST_RWLIST_UNLOCK(&signals);
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return s;
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}
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static int wait_for_signal_or_hangup(struct ast_channel *chan, char *signame, int timeout)
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{
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struct signalitem *s = NULL;
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int ms, remaining_time, res = 1, goaway = 0;
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struct timeval start;
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struct ast_frame *frame = NULL;
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remaining_time = timeout;
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start = ast_tvnow();
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s = get_signal(signame, 1);
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ast_mutex_lock(&s->lock);
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s->watchers = s->watchers + 1; /* we unlock, because a) other people need to use this and */
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ast_mutex_unlock(&s->lock); /* b) the signal will be available to us as long as watchers > 0 */
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while (timeout == 0 || remaining_time > 0) {
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int ofd, exception;
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ms = 1000;
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errno = 0;
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if (ast_waitfor_nandfds(&chan, 1, &s->sig_alert_pipe[0], 1, &exception, &ofd, &ms)) { /* channel won */
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if (!(frame = ast_read(chan))) { /* channel hung up */
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ast_debug(1, "Channel '%s' did not return a frame; probably hung up.\n", ast_channel_name(chan));
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res = -1;
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break;
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} else {
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ast_frfree(frame); /* handle frames */
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}
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} else if (ofd == s->sig_alert_pipe[0]) { /* fd won */
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if (ast_alertpipe_read(s->sig_alert_pipe) == AST_ALERT_READ_SUCCESS) {
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ast_debug(1, "Alert pipe has data for us\n");
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res = 0;
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break;
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} else {
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ast_debug(1, "Alert pipe does not have data for us\n");
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}
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} else { /* nobody won */
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if (ms && (ofd < 0)) {
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if (!((errno == 0) || (errno == EINTR))) {
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ast_log(LOG_WARNING, "Something bad happened while channel '%s' was polling.\n", ast_channel_name(chan));
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break;
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}
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} /* else, nothing happened */
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}
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if (timeout) {
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remaining_time = ast_remaining_ms(start, timeout);
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}
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}
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/* WRLOCK the list so that if we're going to destroy the signal now, nobody else can grab it before that happens. */
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AST_RWLIST_WRLOCK(&signals);
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ast_mutex_lock(&s->lock);
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if (s->payload) {
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pbx_builtin_setvar_helper(chan, "WAITFORSIGNALPAYLOAD", s->payload);
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}
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s->watchers = s->watchers - 1;
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if (s->watchers) { /* folks are still waiting for this, pass it on... */
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int save_errno = errno;
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if (ast_alertpipe_write(s->sig_alert_pipe)) {
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ast_log(LOG_WARNING, "%s: write() failed: %s\n", __FUNCTION__, strerror(errno));
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}
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errno = save_errno;
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} else { /* nobody else is waiting for this */
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goaway = 1; /* we were the last guy using this, so mark signal item for destruction */
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}
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ast_mutex_unlock(&s->lock);
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if (goaway) {
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/* remove_signal calls ast_mutex_destroy, so don't call it with the mutex itself locked. */
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remove_signal(signame);
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}
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AST_RWLIST_UNLOCK(&signals);
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return res;
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}
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static int send_signal(char *signame, char *payload)
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{
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struct signalitem *s;
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int save_errno = errno;
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int res = 0;
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s = get_signal(signame, 0); /* if signal doesn't exist already, no point in creating it, because nobody could be waiting for it! */
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if (!s) {
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return -1; /* this signal didn't exist, so we can't send a signal for it */
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}
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/* at this point, we know someone is listening, since signals are destroyed when watchers gets down to 0 */
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ast_mutex_lock(&s->lock);
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s->signaled = 1;
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if (payload && *payload) {
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int len = strlen(payload);
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if (s->payload) {
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ast_free(s->payload); /* if there was already a payload, replace it */
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s->payload = NULL;
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}
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s->payload = ast_malloc(len + 1);
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if (!s->payload) {
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ast_log(LOG_WARNING, "Failed to allocate signal payload '%s'\n", payload);
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} else {
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ast_copy_string(s->payload, payload, len + 1);
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}
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}
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if (ast_alertpipe_write(s->sig_alert_pipe)) {
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ast_log(LOG_WARNING, "%s: write() failed: %s\n", __FUNCTION__, strerror(errno));
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s->signaled = 0; /* okay, so we didn't send a signal after all... */
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res = -1;
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}
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errno = save_errno;
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ast_debug(1, "Sent '%s' signal to %d listeners\n", signame, s->watchers);
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ast_mutex_unlock(&s->lock);
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return res;
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}
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static int waitsignal_exec(struct ast_channel *chan, const char *data)
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{
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char *argcopy;
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int r = 0, timeoutms = 0;
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double timeout = 0;
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AST_DECLARE_APP_ARGS(args,
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AST_APP_ARG(signame);
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AST_APP_ARG(sigtimeout);
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);
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if (ast_strlen_zero(data)) {
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ast_log(LOG_WARNING, "Signal() requires arguments\n");
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return -1;
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}
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argcopy = ast_strdupa(data);
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AST_STANDARD_APP_ARGS(args, argcopy);
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if (ast_strlen_zero(args.signame)) {
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ast_log(LOG_WARNING, "Missing signal name\n");
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return -1;
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}
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if (strlen(args.signame) >= AST_MAX_CONTEXT) {
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ast_log(LOG_WARNING, "Signal name '%s' is too long\n", args.signame);
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return -1;
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}
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if (!ast_strlen_zero(args.sigtimeout)) {
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if (sscanf(args.sigtimeout, "%30lg", &timeout) != 1 || timeout < 0) {
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ast_log(LOG_WARNING, "Invalid timeout provided: %s. Defaulting to no timeout.\n", args.sigtimeout);
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} else {
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timeoutms = timeout * 1000; /* sec to msec */
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}
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}
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if (timeout > 0) {
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ast_debug(1, "Waiting for signal '%s' for %d ms\n", args.signame, timeoutms);
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} else {
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ast_debug(1, "Waiting for signal '%s', indefinitely\n", args.signame);
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}
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r = wait_for_signal_or_hangup(chan, args.signame, timeoutms);
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if (r == 1) {
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ast_verb(3, "Channel '%s' timed out, waiting for signal '%s'\n", ast_channel_name(chan), args.signame);
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pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "TIMEOUT");
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} else if (!r) {
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ast_verb(3, "Received signal '%s' on channel '%s'\n", args.signame, ast_channel_name(chan));
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pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "SIGNALED");
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} else {
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pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "HANGUP");
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ast_verb(3, "Channel '%s' hung up\n", ast_channel_name(chan));
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return -1;
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}
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return 0;
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}
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static int signal_exec(struct ast_channel *chan, const char *data)
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{
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char *argcopy;
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AST_DECLARE_APP_ARGS(args,
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AST_APP_ARG(signame);
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AST_APP_ARG(payload);
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);
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if (ast_strlen_zero(data)) {
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ast_log(LOG_WARNING, "Signal() requires arguments\n");
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return -1;
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}
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argcopy = ast_strdupa(data);
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AST_STANDARD_APP_ARGS(args, argcopy);
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if (ast_strlen_zero(args.signame)) {
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ast_log(LOG_WARNING, "Missing signal name\n");
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return -1;
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}
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if (strlen(args.signame) >= AST_MAX_CONTEXT) {
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ast_log(LOG_WARNING, "Signal name '%s' is too long\n", args.signame);
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return -1;
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}
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if (send_signal(args.signame, args.payload)) {
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pbx_builtin_setvar_helper(chan, "SIGNALSTATUS", "FAILURE");
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} else {
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pbx_builtin_setvar_helper(chan, "SIGNALSTATUS", "SUCCESS");
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}
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return 0;
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}
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static int unload_module(void)
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{
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struct signalitem *s;
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int res = 0;
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/* To avoid a locking nightmare, and for logistical reasons, this module
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* will refuse to unload if watchers > 0. That way we know a signal's
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* pipe won't disappear while it's being used. */
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AST_RWLIST_WRLOCK(&signals);
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/* Don't just use AST_RWLIST_REMOVE_HEAD, because if dealloc_signal fails, it should stay in the list. */
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AST_LIST_TRAVERSE_SAFE_BEGIN(&signals, s, entry) {
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int mres = dealloc_signal(s);
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res |= mres;
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if (!mres) {
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AST_LIST_REMOVE_CURRENT(entry);
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}
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}
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AST_LIST_TRAVERSE_SAFE_END;
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AST_RWLIST_UNLOCK(&signals);
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/* One or more signals still has watchers. */
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if (res) {
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ast_log(LOG_WARNING, "One or more signals is currently in use. Unload failed.\n");
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return res;
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}
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res |= ast_unregister_application(app);
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res |= ast_unregister_application(app2);
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return res;
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}
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static int load_module(void)
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{
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int res;
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res = ast_register_application_xml(app, signal_exec);
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res |= ast_register_application_xml(app2, waitsignal_exec);
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return res;
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}
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AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Channel Signaling Applications");
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|
|
@ -0,0 +1,5 @@
|
|||
Subject: app_signal
|
||||
|
||||
Adds Signal and WaitForSignal applications
|
||||
which can be used for signaling or as a
|
||||
simple message queue in the dialplan.
|
||||
Loading…
Reference in New Issue