res_msp: Add Message Send Protocol support.

This adds support for sending messages via
the Message Send Protocol (version 2), using
the existing message API.

README.md

@@ -15,6 +15,7 @@ PhreakScript installs:
    - Broadworks compatible device feature key synchronization (PJSIP)
    - Broadworks compatible Shared Call Appearances (PJSIP)
    - Presence publishing (PJSIP)
+   - Message Send Protocol send support
    - AGI `RECORD FILE` option to require noise before silence detection
    - Optional build enhancements
       - `chan_sccp` (improved community Skinny/SCCP channel driver)

res/res_msp.c

@@ -0,0 +1,151 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2023, 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 Send a message via the RFC1312 Message Send Protocol (version 2)
+ *
+ * \author Naveen Albert <asterisk@phreaknet.org>
+ *
+ * \ingroup applications
+ */
+
+/*** MODULEINFO
+	<support_level>extended</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/logger.h"
+#include "asterisk/module.h"
+#include "asterisk/message.h"
+#include "asterisk/netsock2.h"
+#include "asterisk/config.h"
+#include "asterisk/utils.h"
+
+/*** DOCUMENTATION
+	<info name="MessageDestinationInfo" language="en_US" tech="MSP">
+		<para>Specifying a prefix of <literal>msp:</literal> will send the
+		message to the specified hostname using the Message Send Protocol version 2.</para>
+		<para>For example:
+		<literal>same => n,Set(MESSAGE(body)=This is my message)</literal> will set the message
+		and <literal>same => n,MessageSend(10.1.2.3,Asterisk,Alice)</literal> will
+		send a message to host 10.1.2.3, with a sender of <literal>Asterisk</literal>
+		and a recipient of <literal>Alice.</literal>.</para>
+		<para>Other Message Send Protocol parameters are not currently supported.</para>
+	</info>
+	<info name="MessageFromInfo" language="en_US" tech="MSP">
+		<para>Specifying a prefix of <literal>msp:</literal> will specify the
+		name of the sender of the message, as defined by RFC 1312.</para>
+	</info>
+	<info name="MessageToInfo" language="en_US" tech="MSP">
+		<para>The name of the recipient, as defined in the Message Send Protocol.</para>
+		<para>Specifying a prefix of <literal>msp:</literal> will specify the
+		name of the recipient, as defined by RFC 1312.</para>
+		<para>This parameter is optional, but may be required by the MSP server.</para>
+	</info>
+***/
+
+static int msp_send(const struct ast_msg *msg, const char *destination, const char *from)
+{
+	ssize_t res;
+	int sfd;
+	struct ast_sockaddr addr;
+	char destbuf[128];
+	char *tmp;
+	const char *hostname, *recip;
+	char buf[512]; /* Max size of a MSP message */
+	int len;
+	const char *body;
+
+	if (ast_strlen_zero(destination)) {
+		ast_log(LOG_ERROR, "Missing destination for MSP message\n");
+		return -1;
+	} else if (ast_strlen_zero(from)) {
+		ast_log(LOG_ERROR, "Missing sender for MSP message\n");
+	}
+
+	ast_copy_string(destbuf, destination, sizeof(destbuf));
+	tmp = destbuf;
+	strsep(&tmp, ":"); /* Skip msp: */
+	hostname = tmp;
+	recip = ast_msg_get_to(msg);
+
+	if (ast_strlen_zero(hostname)) {
+		ast_log(LOG_ERROR, "Missing hostname\n");
+		return -1;
+	}
+
+	body = ast_msg_get_body(msg);
+	if (ast_strlen_zero(body)) {
+		ast_log(LOG_ERROR, "No message body to send\n");
+		return -1;
+	}
+
+	/* Construct MSP message */
+	len = snprintf(buf, sizeof(buf), "%c%s%c%c%s%c%s%c%c%c%c", /* To satisfy -Werror=format-contains-nul */
+		'B', /* Version 2 of the MSP protocol */
+		S_OR(recip, ""),
+		'\0',
+		'\0',
+		body,
+		'\0',
+		from,
+		'\0',
+		'\0', '\0', '\0');
+
+	ast_debug(3, "Sending %d-byte MSP message from %s -> %s@%s: %s\n", len, S_OR(from, ""), S_OR(recip, ""), hostname, body);
+	ast_debug(3, "TO: %s\n", ast_msg_get_to(msg));
+
+	memset(&addr, 0, sizeof(addr));
+	ast_parse_arg(hostname, PARSE_ADDR, &addr);
+	ast_sockaddr_set_port(&addr, 18);
+
+	/* Message Send Protocol supports delivery via both TCP and UDP.
+	 * Send via UDP, since there's less overhead, and we don't care about the acknowledgment */
+	sfd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sfd < 0) {
+        ast_log(LOG_ERROR, "ast_socket failed: %s\n", strerror(errno));
+        return -1;
+    }
+
+	res = ast_sendto(sfd, buf, len, 0, &addr);
+	if (res <= 0) {
+		ast_log(LOG_ERROR, "ast_sendto(%s) failed: %s\n", hostname, strerror(errno));
+	}
+
+	close(sfd);
+	return res <= 0 ? -1 : 0;
+}
+
+static const struct ast_msg_tech msg_tech = {
+	.name = "msp",
+	.msg_send = msp_send,
+};
+
+static int unload_module(void)
+{
+	return ast_msg_tech_unregister(&msg_tech);
+}
+
+static int load_module(void)
+{
+	return ast_msg_tech_register(&msg_tech);
+}
+
+AST_MODULE_INFO_STANDARD_EXTENDED(ASTERISK_GPL_KEY, "Message Send Protocol");