Add optional support for RFC863, Discard Protocol

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

README.md

@@ -73,8 +73,9 @@ interface, reducing the need for a full blown firewall.
 
 Built-in optional inetd services:
 
-- time (rdate) RFC862
-- echo RFC868
+- echo RFC862
+- discard RFC863
+- time (rdate) RFC868
 
 
 **Runlevels**
@@ -484,10 +485,11 @@ The original `inetd` had a few standard services built-in:
 - chargen
 - discard
 
-Finit currently supports the `time` and `echo` services.  Both of which
-are realized as plugins to provide a simple means of testing the inetd
-functionality stand-alone.  But this also provides both a useful network
-testing/availability and a rudimentary time server for rdate clients.
+Finit currently supports the `time`, `echo`, and `discard` services.
+Both of which are realized as plugins to provide a simple means of
+testing the inetd functionality stand-alone.  But this also provides
+both a useful network testing/availability and a rudimentary time server
+for rdate clients.
 
 Internal inetd services are set up as follows:
 
@@ -496,6 +498,8 @@ Internal inetd services are set up as follows:
     inetd time/tcp         nowait [2345] internal
     inetd echo/udp           wait [2345] internal
     inetd echo/tcp         nowait [2345] internal
+    inetd discard/udp        wait [2345] internal
+    inetd discard/tcp      nowait [2345] internal
 ```
 
 Then call `rdate` from a remote machine (or use localhost):
@@ -512,6 +516,13 @@ Or `echoping` to reach the echo service:
     echoping -uv <IP>
 ```
 
+Or `echoping -d` to reach the discard service:
+
+```shell
+    echoping -dv  <IP>
+    echoping -duv <IP>
+```
+
 If you use `time/udp` you must use the standard rdate implementation and
 then call it with `rdate -up` to connect using UDP.  Without the `-p`
 argument rdate will try to set the system clock.  Please note that rdate
@@ -554,6 +565,8 @@ For your convenience a set of *optional* plugins are available:
 
 * *echo.so*: RFC 862 plugin.  Start as inetd service, like time below.
 
+* *discard.so*: RFC 863 plugin.  Start as inetd service, like time below.
+
 * *hwclock.so*: Restore and save system clock from/to RTC on
   startup/shutdown.
 

configure.ac

@@ -53,14 +53,15 @@ AC_ARG_ENABLE(quiet,
 
 # Check for extra plugins to enable
 enable_all_plugins=auto
-AC_PLUGIN([alsa-utils], [no],  [Save and restore ALSA sound settings using alsactl])
-AC_PLUGIN([dbus],       [no],  [Setup and start system message bus, D-Bus])
-AC_PLUGIN([inetd-echo], [no],  [Inetd plugin: echo server, RFC862])
-AC_PLUGIN([inetd-time], [no],  [Inetd plugin: time (rdate) server, RFC868])
-AC_PLUGIN([lost],       [no],  [Example HOOK_SVC_LOST plugin, very noisy as-is!])
-AC_PLUGIN([resolvconf], [no],  [Setup necessary files for resolvconf])
-AC_PLUGIN([x11-common], [no],  [Console setup (for X)])
-AC_PLUGIN([netlink],    [yes], [Basic netlink plugin for IFUP/IFDN and GW events. Can be replaced with externally built plugin that links with libnl or similar.])
+AC_PLUGIN([alsa-utils],    [no],  [Save and restore ALSA sound settings using alsactl])
+AC_PLUGIN([dbus],          [no],  [Setup and start system message bus, D-Bus])
+AC_PLUGIN([inetd-echo],    [no],  [Inetd plugin: echo server, RFC862])
+AC_PLUGIN([inetd-discard], [no],  [Inetd plugin: discard server, RFC862])
+AC_PLUGIN([inetd-time],    [no],  [Inetd plugin: time (rdate) server, RFC868])
+AC_PLUGIN([lost],          [no],  [Example HOOK_SVC_LOST plugin, very noisy as-is!])
+AC_PLUGIN([resolvconf],    [no],  [Setup necessary files for resolvconf])
+AC_PLUGIN([x11-common],    [no],  [Console setup (for X)])
+AC_PLUGIN([netlink],       [yes], [Basic netlink plugin for IFUP/IFDN and GW events. Can be replaced with externally built plugin that links with libnl or similar.])
 
 # Check for extra arguments or packages
 AC_ARG_WITH(heading,

plugins/Makefile.am

@@ -19,6 +19,10 @@ if BUILD_INETD_ECHO_PLUGIN
 libplug_la_SOURCES += echo.c
 endif
 
+if BUILD_INETD_DISCARD_PLUGIN
+libplug_la_SOURCES += discard.c
+endif
+
 if BUILD_INETD_TIME_PLUGIN
 libplug_la_SOURCES += time.c
 endif
@@ -50,6 +54,10 @@ if BUILD_INETD_ECHO_PLUGIN
 pkglib_LTLIBRARIES += echo.la
 endif
 
+if BUILD_INETD_DISCARD_PLUGIN
+pkglib_LTLIBRARIES += discard.la
+endif
+
 if BUILD_INETD_TIME_PLUGIN
 pkglib_LTLIBRARIES += time.la
 endif

plugins/discard.c

@@ -0,0 +1,67 @@
+/* Optional inetd plugin for the Discard Protocol, RFC 863
+ *
+ * Copyright (c) 2016  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <arpa/inet.h>
+#include <unistd.h>		/* STDIN_FILENO */
+#include <sys/socket.h>
+
+#include "../plugin.h"
+
+static int cb(int type)
+{
+	int sd = STDIN_FILENO;
+	char buf[BUFSIZ];
+	ssize_t len;
+	struct sockaddr_storage sa;
+	socklen_t sa_len = sizeof(sa);
+
+	len = recvfrom(sd, buf, sizeof(buf), MSG_DONTWAIT, (struct sockaddr *)&sa, &sa_len);
+	if (-1 == len)
+		return -1;	/* On error, close connection. */
+
+	return 0;
+}
+
+static plugin_t plugin = {
+	.name  = "discard",	/* Must match the inetd /etc/services entry */
+	.inetd = {
+		.cmd = cb
+	},
+};
+
+PLUGIN_INIT(plugin_init)
+{
+	plugin_register(&plugin);
+}
+
+PLUGIN_EXIT(plugin_exit)
+{
+	plugin_unregister(&plugin);
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */

plugins/echo.c

@@ -1,4 +1,4 @@
-/* Optional inetd plugin for the echo protocol RFC 862
+/* Optional inetd plugin for the Echo Protocol, RFC 862
  *
  * Copyright (c) 2016  Joachim Nilsson <troglobit@gmail.com>
  *
@@ -27,7 +27,7 @@
 
 #include "../plugin.h"
 
-static int echo_cb(int type)
+static int cb(int type)
 {
 	int sd = STDIN_FILENO;
 	char buf[BUFSIZ];
@@ -45,7 +45,7 @@ static int echo_cb(int type)
 static plugin_t plugin = {
 	.name  = "echo",	/* Must match the inetd /etc/services entry */
 	.inetd = {
-		.cmd = echo_cb
+		.cmd = cb
 	},
 };
 

plugins/time.c

@@ -1,4 +1,4 @@
-/* Optional inetd plugin for time (rdate) protocol RFC 868
+/* Optional inetd plugin for Time Protocol (rdate), RFC 868
  *
  * Copyright (c) 2015  Joachim Nilsson <troglobit@gmail.com>
  *
@@ -32,7 +32,7 @@
 #define EPOCH_OFFSET 2208988800ULL
 
 /* Return number of seconds since midnight, 1st Jan, 1900 */
-static int rfc868(int type)
+static int cb(int type)
 {
 	int sd = STDIN_FILENO;
 	time_t now;
@@ -64,7 +64,7 @@ static int rfc868(int type)
 static plugin_t plugin = {
 	.name  = "time",	/* Must match the inetd /etc/services entry */
 	.inetd = {
-		.cmd = rfc868
+		.cmd = cb
 	}
 };