Asterisk
/
asterisk
mirror of https://github.com/asterisk/asterisk
1
0
Fork 0
Code Issues Releases Wiki Activity

app_signal: Add signaling applications

Browse Source 
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
20.2
Naveen Albert 3 years ago committed by N A
parent 70856e865f
commit 88b2c741ca
2 changed files with 476 additions and 0 deletions
Show Stats Download Patch File Download Diff File

471
apps/app_signal.c
Unescape View File

@ -0,0 +1,471 @@
/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2022, Naveen Albert
*
* Naveen Albert <asterisk@phreaknet.org>
*
* 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 signaling applications
*
* \author Naveen Albert <asterisk@phreaknet.org>
*
* \ingroup applications
*/
/*** MODULEINFO
<support_level>extended</support_level>
***/
#include "asterisk.h"
#include "asterisk/file.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/app.h"
#include "asterisk/module.h"
/*** DOCUMENTATION
<application name="Signal" language="en_US">
<synopsis>
Sends a signal to any waiting channels.
</synopsis>
<syntax>
<parameter name="signalname" required="true">
<para>Name of signal to send.</para>
</parameter>
<parameter name="payload" required="false">
<para>Payload data to deliver.</para>
</parameter>
</syntax>
<description>
<para>Sends a named signal to any channels that may be
waiting for one. Acts as a producer in a simple
message queue.</para>
<variablelist>
<variable name="SIGNALSTATUS">
<value name="SUCCESS">
Signal was successfully sent to at least
one listener for processing.
</value>
<value name="FAILURE">
Signal could not be sent or nobody
was listening for this signal.
</value>
</variable>
</variablelist>
<example title="Send a signal named workdone">
same => n,Signal(workdone,Work has completed)
</example>
</description>
<see-also>
<ref type="application">WaitForSignal</ref>
</see-also>
</application>
<application name="WaitForSignal" language="en_US">
<synopsis>
Waits for a named signal on a channel.
</synopsis>
<syntax>
<parameter name="signalname" required="true">
<para>Name of signal to send.</para>
</parameter>
<parameter name="signaltimeout" required="false">
<para>Maximum time, in seconds, to wait for signal.</para>
</parameter>
</syntax>
<description>
<para>Waits for <replaceable>signaltimeout</replaceable> seconds on the current
channel to receive a signal with name <replaceable>signalname</replaceable>.
Acts as a consumer in a simple message queue.</para>
<para>Result of signal wait will be stored in the following variables:</para>
<variablelist>
<variable name="WAITFORSIGNALSTATUS">
<value name="SIGNALED">
Signal was received.
</value>
<value name="TIMEOUT">
Timed out waiting for signal.
</value>
<value name="HANGUP">
Channel hung up before signal was received.
</value>
</variable>
<variable name="WAITFORSIGNALPAYLOAD">
<para>Data payload attached to signal, if it exists</para>
</variable>
</variablelist>
<example title="Wait for the workdone signal, indefinitely, and print out payload">
same => n,WaitForSignal(workdone)
same => n,NoOp(Received: ${WAITFORSIGNALPAYLOAD})
</example>
</description>
<see-also>
<ref type="application">Signal</ref>
</see-also>
</application>
***/
static const char * const app = "Signal";
static const char * const app2 = "WaitForSignal";
struct signalitem {
ast_mutex_t lock;
char name[AST_MAX_CONTEXT];
int sig_alert_pipe[2];
int watchers;
unsigned int signaled:1;
char *payload;
AST_LIST_ENTRY(signalitem) entry; /*!< Next Signal item */
};
static AST_RWLIST_HEAD_STATIC(signals, signalitem);
static struct signalitem *alloc_signal(const char *sname)
{
struct signalitem *s;
if (!(s = ast_calloc(1, sizeof(*s)))) {
return NULL;
}
ast_mutex_init(&s->lock);
ast_copy_string(s->name, sname, sizeof(s->name));
s->sig_alert_pipe[0] = -1;
s->sig_alert_pipe[1] = -1;
s->watchers = 0;
s->payload = NULL;
ast_alertpipe_init(s->sig_alert_pipe);
return s;
}
static int dealloc_signal(struct signalitem *s)
{
if (s->watchers) { /* somebody is still using us... refuse to go away */
ast_debug(1, "Signal '%s' is still being used by %d listener(s)\n", s->name, s->watchers);
return -1;
}
ast_alertpipe_close(s->sig_alert_pipe);
ast_mutex_destroy(&s->lock);
if (s->payload) {
ast_free(s->payload);
s->payload = NULL;
}
ast_free(s);
s = NULL;
return 0;
}
static int remove_signal(char *sname)
{
int res = -1;
struct signalitem *s;
AST_LIST_TRAVERSE_SAFE_BEGIN(&signals, s, entry) {
if (!strcmp(s->name, sname)) {
AST_LIST_REMOVE_CURRENT(entry);
res = dealloc_signal(s);
ast_debug(1, "Removed signal '%s'\n", sname);
}
}
AST_LIST_TRAVERSE_SAFE_END;
return res;
}
static struct signalitem *get_signal(char *sname, int addnew)
{
struct signalitem *s = NULL;
AST_RWLIST_WRLOCK(&signals);
AST_LIST_TRAVERSE(&signals, s, entry) {
if (!strcasecmp(s->name, sname)) {
ast_debug(1, "Using existing signal item '%s'\n", sname);
break;
}
}
if (!s) {
if (addnew) { /* signal doesn't exist, so create it */
s = alloc_signal(sname);
/* Totally fail if we fail to find/create an entry */
if (s) {
ast_debug(1, "Created new signal item '%s'\n", sname);
AST_RWLIST_INSERT_HEAD(&signals, s, entry);
} else {
ast_log(LOG_WARNING, "Failed to create signal item for '%s'\n", sname);
}
} else {
ast_debug(1, "Signal '%s' doesn't exist, and not creating it\n", sname);
}
}
AST_RWLIST_UNLOCK(&signals);
return s;
}
static int wait_for_signal_or_hangup(struct ast_channel *chan, char *signame, int timeout)
{
struct signalitem *s = NULL;
int ms, remaining_time, res = 1, goaway = 0;
struct timeval start;
struct ast_frame *frame = NULL;
remaining_time = timeout;
start = ast_tvnow();
s = get_signal(signame, 1);
ast_mutex_lock(&s->lock);
s->watchers = s->watchers + 1; /* we unlock, because a) other people need to use this and */
ast_mutex_unlock(&s->lock); /* b) the signal will be available to us as long as watchers > 0 */
while (timeout == 0 || remaining_time > 0) {
int ofd, exception;
ms = 1000;
errno = 0;
if (ast_waitfor_nandfds(&chan, 1, &s->sig_alert_pipe[0], 1, &exception, &ofd, &ms)) { /* channel won */
if (!(frame = ast_read(chan))) { /* channel hung up */
ast_debug(1, "Channel '%s' did not return a frame; probably hung up.\n", ast_channel_name(chan));
res = -1;
break;
} else {
ast_frfree(frame); /* handle frames */
}
} else if (ofd == s->sig_alert_pipe[0]) { /* fd won */
if (ast_alertpipe_read(s->sig_alert_pipe) == AST_ALERT_READ_SUCCESS) {
ast_debug(1, "Alert pipe has data for us\n");
res = 0;
break;
} else {
ast_debug(1, "Alert pipe does not have data for us\n");
}
} else { /* nobody won */
if (ms && (ofd < 0)) {
if (!((errno == 0) || (errno == EINTR))) {
ast_log(LOG_WARNING, "Something bad happened while channel '%s' was polling.\n", ast_channel_name(chan));
break;
}
} /* else, nothing happened */
}
if (timeout) {
remaining_time = ast_remaining_ms(start, timeout);
}
}
/* WRLOCK the list so that if we're going to destroy the signal now, nobody else can grab it before that happens. */
AST_RWLIST_WRLOCK(&signals);
ast_mutex_lock(&s->lock);
if (s->payload) {
pbx_builtin_setvar_helper(chan, "WAITFORSIGNALPAYLOAD", s->payload);
}
s->watchers = s->watchers - 1;
if (s->watchers) { /* folks are still waiting for this, pass it on... */
int save_errno = errno;
if (ast_alertpipe_write(s->sig_alert_pipe)) {
ast_log(LOG_WARNING, "%s: write() failed: %s\n", __FUNCTION__, strerror(errno));
}
errno = save_errno;
} else { /* nobody else is waiting for this */
goaway = 1; /* we were the last guy using this, so mark signal item for destruction */
}
ast_mutex_unlock(&s->lock);
if (goaway) {
/* remove_signal calls ast_mutex_destroy, so don't call it with the mutex itself locked. */
remove_signal(signame);
}
AST_RWLIST_UNLOCK(&signals);
return res;
}
static int send_signal(char *signame, char *payload)
{
struct signalitem *s;
int save_errno = errno;
int res = 0;
s = get_signal(signame, 0); /* if signal doesn't exist already, no point in creating it, because nobody could be waiting for it! */
if (!s) {
return -1; /* this signal didn't exist, so we can't send a signal for it */
}
/* at this point, we know someone is listening, since signals are destroyed when watchers gets down to 0 */
ast_mutex_lock(&s->lock);
s->signaled = 1;
if (payload && *payload) {
int len = strlen(payload);
if (s->payload) {
ast_free(s->payload); /* if there was already a payload, replace it */
s->payload = NULL;
}
s->payload = ast_malloc(len + 1);
if (!s->payload) {
ast_log(LOG_WARNING, "Failed to allocate signal payload '%s'\n", payload);
} else {
ast_copy_string(s->payload, payload, len + 1);
}
}
if (ast_alertpipe_write(s->sig_alert_pipe)) {
ast_log(LOG_WARNING, "%s: write() failed: %s\n", __FUNCTION__, strerror(errno));
s->signaled = 0; /* okay, so we didn't send a signal after all... */
res = -1;
}
errno = save_errno;
ast_debug(1, "Sent '%s' signal to %d listeners\n", signame, s->watchers);
ast_mutex_unlock(&s->lock);
return res;
}
static int waitsignal_exec(struct ast_channel *chan, const char *data)
{
char *argcopy;
int r = 0, timeoutms = 0;
double timeout = 0;
AST_DECLARE_APP_ARGS(args,
AST_APP_ARG(signame);
AST_APP_ARG(sigtimeout);
);
if (ast_strlen_zero(data)) {
ast_log(LOG_WARNING, "Signal() requires arguments\n");
return -1;
}
argcopy = ast_strdupa(data);
AST_STANDARD_APP_ARGS(args, argcopy);
if (ast_strlen_zero(args.signame)) {
ast_log(LOG_WARNING, "Missing signal name\n");
return -1;
}
if (strlen(args.signame) >= AST_MAX_CONTEXT) {
ast_log(LOG_WARNING, "Signal name '%s' is too long\n", args.signame);
return -1;
}
if (!ast_strlen_zero(args.sigtimeout)) {
if (sscanf(args.sigtimeout, "%30lg", &timeout) != 1 || timeout < 0) {
ast_log(LOG_WARNING, "Invalid timeout provided: %s. Defaulting to no timeout.\n", args.sigtimeout);
} else {
timeoutms = timeout * 1000; /* sec to msec */
}
}
if (timeout > 0) {
ast_debug(1, "Waiting for signal '%s' for %d ms\n", args.signame, timeoutms);
} else {
ast_debug(1, "Waiting for signal '%s', indefinitely\n", args.signame);
}
r = wait_for_signal_or_hangup(chan, args.signame, timeoutms);
if (r == 1) {
ast_verb(3, "Channel '%s' timed out, waiting for signal '%s'\n", ast_channel_name(chan), args.signame);
pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "TIMEOUT");
} else if (!r) {
ast_verb(3, "Received signal '%s' on channel '%s'\n", args.signame, ast_channel_name(chan));
pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "SIGNALED");
} else {
pbx_builtin_setvar_helper(chan, "WAITFORSIGNALSTATUS", "HANGUP");
ast_verb(3, "Channel '%s' hung up\n", ast_channel_name(chan));
return -1;
}
return 0;
}
static int signal_exec(struct ast_channel *chan, const char *data)
{
char *argcopy;
AST_DECLARE_APP_ARGS(args,
AST_APP_ARG(signame);
AST_APP_ARG(payload);
);
if (ast_strlen_zero(data)) {
ast_log(LOG_WARNING, "Signal() requires arguments\n");
return -1;
}
argcopy = ast_strdupa(data);
AST_STANDARD_APP_ARGS(args, argcopy);
if (ast_strlen_zero(args.signame)) {
ast_log(LOG_WARNING, "Missing signal name\n");
return -1;
}
if (strlen(args.signame) >= AST_MAX_CONTEXT) {
ast_log(LOG_WARNING, "Signal name '%s' is too long\n", args.signame);
return -1;
}
if (send_signal(args.signame, args.payload)) {
pbx_builtin_setvar_helper(chan, "SIGNALSTATUS", "FAILURE");
} else {
pbx_builtin_setvar_helper(chan, "SIGNALSTATUS", "SUCCESS");
}
return 0;
}
static int unload_module(void)
{
struct signalitem *s;
int res = 0;
/* To avoid a locking nightmare, and for logistical reasons, this module
* will refuse to unload if watchers > 0. That way we know a signal's
* pipe won't disappear while it's being used. */
AST_RWLIST_WRLOCK(&signals);
/* Don't just use AST_RWLIST_REMOVE_HEAD, because if dealloc_signal fails, it should stay in the list. */
AST_LIST_TRAVERSE_SAFE_BEGIN(&signals, s, entry) {
int mres = dealloc_signal(s);
res |= mres;
if (!mres) {
AST_LIST_REMOVE_CURRENT(entry);
}
}
AST_LIST_TRAVERSE_SAFE_END;
AST_RWLIST_UNLOCK(&signals);
/* One or more signals still has watchers. */
if (res) {
ast_log(LOG_WARNING, "One or more signals is currently in use. Unload failed.\n");
return res;
}
res |= ast_unregister_application(app);
res |= ast_unregister_application(app2);
return res;
}
static int load_module(void)
{
int res;
res = ast_register_application_xml(app, signal_exec);
res |= ast_register_application_xml(app2, waitsignal_exec);
return res;
}
AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Channel Signaling Applications");

5
doc/CHANGES-staging/app_signal.txt
Unescape View File

@ -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.
Write Preview
Loading…
Cancel
Save