Merge remote-tracking branch 'origin/inetd-plugins'

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

README.md

@@ -73,8 +73,11 @@ interface, reducing the need for a full blown firewall.
 
 Built-in optional inetd services:
 
-- time (rdate) RFC862
+- echo RFC862
-- echo RFC868
+- chargen RFC864
+- daytime RFC867
+- discard RFC863
+- time (rdate) RFC868
 
 
 **Runlevels**
@@ -437,7 +440,8 @@ Inetd
 A built-in *Internet Super Server* support was added in Finit v1.12 and
 v1.13, along with an internal `time` inetd service, RFC 868 (rdate).
 The latter is supplied as a plugin to illustrate how simple it is to
-extend finit with more internal inetd services.
+extend finit with more internal inetd services.  Today more built-in
+services are available.
 
 > Please note, not all UNIX daemons are prepared to run as inetd services.
 > In the example below `sshd` also need the command line argument `-i`.
@@ -474,28 +478,40 @@ default port.  To run ssh on port 222, and all others on port 22:
 
 Compared to Finit v1.12 you must *explicitly deny* access from `eth0`!
 
+To protect against looping attacks, the inetd server will refuse UDP
+service if the reply port corresponds to any internal service.  Similar
+to how the FreeBSD inetd operates.
+
 
 **Internal Services**
 
-The original `inetd` had a few standard services built-in:
+Like the original `inetd`, Finit has a few standard services built-in.
+They 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, as well as a rudimentary time server for
+`rdate` clients.
 
-- time
 - echo
 - chargen
+- daytime
 - discard
+- time
 
-Finit currently supports the `time` and `echo` services.  Both of which
+For security reasons they are all disabled by default and have to be
-are realized as plugins to provide a simple means of testing the inetd
+enabled with both the `configure` script and a special `inetd` stanza in
-functionality stand-alone.  But this also provides both a useful network
+the `finit.conf` or `finit.d/*.conf` like this:
-testing/availability and a rudimentary time server for rdate clients.
-
-Internal inetd services are set up as follows:
 
 ```shell
-    inetd time/udp           wait [2345] internal
-    inetd time/tcp         nowait [2345] internal
     inetd echo/udp           wait [2345] internal
     inetd echo/tcp         nowait [2345] internal
+    inetd chargen/udp        wait [2345] internal
+    inetd chargen/tcp      nowait [2345] internal
+    inetd daytime/udp        wait [2345] internal
+    inetd daytime/tcp      nowait [2345] internal
+    inetd discard/udp        wait [2345] internal
+    inetd discard/tcp      nowait [2345] internal
+    inetd time/udp           wait [2345] internal
+    inetd time/tcp         nowait [2345] internal
 ```
 
 Then call `rdate` from a remote machine (or use localhost):
@@ -512,6 +528,20 @@ 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>
+```
+
+Or `echoping -c` to reach the chargen service:
+
+```shell
+    echoping -cv  <IP>
+    echoping -cuv <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 +584,12 @@ For your convenience a set of *optional* plugins are available:
 
 * *echo.so*: RFC 862 plugin.  Start as inetd service, like time below.
 
+* *chargen.so*: RFC 864 plugin.  Start as inetd service, like time below.
+
+* *daytime.so*: RFC 867 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 +53,17 @@ 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([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([dbus],          [no],  [Setup and start system message bus, D-Bus])
-AC_PLUGIN([inetd-echo], [no],  [Inetd plugin: echo server, RFC862])
+AC_PLUGIN([inetd-echo],    [no],  [Inetd plugin: echo server, RFC862])
-AC_PLUGIN([inetd-time], [no],  [Inetd plugin: time (rdate) server, RFC868])
+AC_PLUGIN([inetd-chargen], [no],  [Inetd plugin: character generator, RFC864])
-AC_PLUGIN([lost],       [no],  [Example HOOK_SVC_LOST plugin, very noisy as-is!])
+AC_PLUGIN([inetd-daytime], [no],  [Inetd plugin: daytime server, RFC867])
-AC_PLUGIN([resolvconf], [no],  [Setup necessary files for resolvconf])
+AC_PLUGIN([inetd-discard], [no],  [Inetd plugin: discard server, RFC863])
-AC_PLUGIN([x11-common], [no],  [Console setup (for X)])
+AC_PLUGIN([inetd-time],    [no],  [Inetd plugin: time (rdate) server, RFC868])
-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([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,

finit.c

@@ -38,7 +38,6 @@
 #include "service.h"
 #include "sig.h"
 #include "tty.h"
-#include "inetd.h"
 #include "sm.h"
 
 int   debug     = 0;

inetd.c

@@ -107,8 +107,8 @@ static int inetd_stream_peek(int sd, char *ifname)
 
 static int get_stdin(svc_t *svc)
 {
-	char ifname[IF_NAMESIZE] = "UNKNOWN";
 	int stdin = svc->inetd.watcher.fd;
+	char ifname[IF_NAMESIZE] = "UNKNOWN";
 
 	if (svc->inetd.type == SOCK_STREAM) {
 		/* Open new client socket from server socket */
@@ -189,6 +189,33 @@ static void socket_cb(uev_t *UNUSED(w), void *arg, int UNUSED(events))
 	service_step(task);
 }
 
+/*
+ * Refuse service if the request specifies a reply port corresponding to any internal service.
+ * This is done as a defense against looping attacks; the remote IP address is logged.
+ * http://www.freebsd.org/cgi/man.cgi?inetd(8)
+ * https://svnweb.freebsd.org/base/head/usr.sbin/inetd/inetd.c?revision=298909&view=markup#l2094
+ */
+int inetd_check_loop(struct sockaddr *sa, socklen_t len, char *name)
+{
+	svc_t *svc;
+        char pname[NI_MAXHOST];
+
+        for (svc = svc_inetd_iterator(1); svc; svc = svc_inetd_iterator(0)) {
+		inetd_t *i = &svc->inetd;
+
+                if (!i->builtin || i->type != SOCK_DGRAM)
+                        continue;
+
+		if (((const struct sockaddr_in *)sa)->sin_port == i->port) {
+			getnameinfo(sa, len, pname, sizeof(pname), NULL, 0, NI_NUMERICHOST);
+			FLOG_WARN("%s/%s:%s/%s loop request REFUSED from %s", i->name, "UDP", name, "UDP", pname);
+			return 1;
+		}
+        }
+
+        return 0;
+}
+
 /* Launch Inet socket for service.
  * TODO: Add filtering ALLOW/DENY per interface.
  */

inetd.h

@@ -46,6 +46,7 @@ typedef struct {
 	int    proto;
 	int    port;
 	int    forking;
+	int    builtin;		/* Set by built-in inetd services only */
 	int    next_id;		/* Next child job's id */
 	char   name[10];
 	int  (*cmd)(int type);	/* internal inetd service, like 'time' */
@@ -53,6 +54,8 @@ typedef struct {
 	TAILQ_HEAD(, inetd_filter) filters;
 } inetd_t;
 
+int  inetd_check_loop  (struct sockaddr *sa, socklen_t len, char *name);
+
 int  inetd_start       (inetd_t *inetd);
 void inetd_stop        (inetd_t *inetd);
 

plugins/Makefile.am

@@ -15,13 +15,27 @@ if BUILD_DBUS_PLUGIN
 libplug_la_SOURCES += dbus.c
 endif
 
+if INETD
 if BUILD_INETD_ECHO_PLUGIN
 libplug_la_SOURCES += echo.c
 endif
 
+if BUILD_INETD_CHARGEN_PLUGIN
+libplug_la_SOURCES += chargen.c
+endif
+
+if BUILD_INETD_DAYTIME_PLUGIN
+libplug_la_SOURCES += daytime.c
+endif
+
+if BUILD_INETD_DISCARD_PLUGIN
+libplug_la_SOURCES += discard.c
+endif
+
 if BUILD_INETD_TIME_PLUGIN
 libplug_la_SOURCES += time.c
 endif
+endif
 
 if BUILD_LOST_PLUGIN
 libplug_la_SOURCES += lost.c
@@ -46,13 +60,27 @@ if BUILD_DBUS_PLUGIN
 pkglib_LTLIBRARIES += dbus.la
 endif
 
+if INETD
 if BUILD_INETD_ECHO_PLUGIN
 pkglib_LTLIBRARIES += echo.la
 endif
 
+if BUILD_INETD_CHARGEN_PLUGIN
+pkglib_LTLIBRARIES += chargen.la
+endif
+
+if BUILD_INETD_DAYTIME_PLUGIN
+pkglib_LTLIBRARIES += daytime.la
+endif
+
+if BUILD_INETD_DISCARD_PLUGIN
+pkglib_LTLIBRARIES += discard.la
+endif
+
 if BUILD_INETD_TIME_PLUGIN
 pkglib_LTLIBRARIES += time.la
 endif
+endif
 
 if BUILD_LOST_PLUGIN
 pkglib_LTLIBRARIES += lost.la

plugins/chargen.c

@@ -0,0 +1,114 @@
+/* Optional inetd plugin for the Character Generator Protocol, RFC 864
+ *
+ * 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"
+
+#define NAME    "chargen"
+#define PATTERN "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~ "
+
+static char *generator(char *buf, size_t len)
+{
+	size_t num;
+	static size_t pos = 0;
+	const char pattern[] = PATTERN;
+
+	len = 72;
+	if (pos + len > sizeof(pattern)) {
+		num = sizeof(pattern) - pos;
+		len -= num;
+	} else {
+		num = 72;
+		len = 0;
+	}
+
+	strncpy(&buf[0], &pattern[pos], num--);
+	if (len++)
+		strncpy(&buf[num], pattern, len);
+	strcat(buf, "\r\n");
+
+	if (++pos >= sizeof(pattern) - 1)
+		pos = 0;
+
+	return buf;
+}
+
+static int recv_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t *sa_len)
+{
+	len = recvfrom(sd, buf, len, MSG_DONTWAIT, sa, sa_len);
+	if (-1 == len)
+		return -1;	/* On error, close connection. */
+
+	if (inetd_check_loop(sa, *sa_len, NAME))
+		return -1;
+
+	return 0;
+} 
+
+static int send_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t sa_len)
+{
+	char *pattern = generator(buf, len);
+
+	return sendto(sd, pattern, strlen(pattern), MSG_DONTWAIT, sa, sa_len);
+}
+
+static int cb(int type)
+{
+	int sd = STDIN_FILENO;
+	ssize_t len;
+	char buf[BUFSIZ];
+	struct sockaddr_storage sa;
+	socklen_t sa_len = sizeof(sa);
+
+	if (recv_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, &sa_len))
+		return -1;
+
+	return send_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, sa_len);
+}
+
+static plugin_t plugin = {
+	.name  = NAME,		/* 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/daytime.c

@@ -0,0 +1,102 @@
+/* Optional inetd plugin for Daytime Protocol, RFC 867
+ *
+ * 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 <time.h>
+#include <unistd.h>		/* STDIN_FILENO */
+#include <sys/socket.h>
+
+#include "../plugin.h"
+
+#define NAME "daytime"
+
+
+static char *daytime(char *buf, size_t len)
+{
+	time_t t;
+	struct tm *tmp;
+
+	t = time(NULL);
+	tmp = localtime(&t);
+
+	memset(buf, 0, len);
+	strftime(buf, len, "%a, %B %d, %Y %T-%Z", tmp);
+
+	return buf;
+}
+
+static int recv_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t *sa_len)
+{
+	len = recvfrom(sd, buf, sizeof(buf), MSG_DONTWAIT, sa, sa_len);
+	if (-1 == len)
+		return -1;	/* On error, close connection. */
+
+	if (inetd_check_loop(sa, *sa_len, NAME))
+		return -1;
+
+	return 0;
+} 
+
+static int send_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t sa_len)
+{
+	char *now = daytime(buf, len);
+
+	return sendto(sd, now, strlen(now), MSG_DONTWAIT, sa, sa_len);
+}
+
+static int cb(int type)
+{
+	int sd = STDIN_FILENO;
+	char buf[BUFSIZ];
+	struct sockaddr_storage sa;
+	socklen_t sa_len = sizeof(sa);
+
+	if (recv_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, &sa_len))
+		return -1;
+
+	return send_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, sa_len);
+}
+
+static plugin_t plugin = {
+	.name  = NAME,		/* 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/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 +27,21 @@
 
 #include "../plugin.h"
 
-static int echo_cb(int type)
+#define NAME "echo"
+
+static int recv_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t *sa_len)
+{
+	len = recvfrom(sd, buf, sizeof(buf), MSG_DONTWAIT, sa, sa_len);
+	if (-1 == len)
+		return -1;	/* On error, close connection. */
+
+	if (inetd_check_loop(sa, *sa_len, NAME))
+		return -1;
+
+	return len;
+}
+
+static int cb(int type)
 {
 	int sd = STDIN_FILENO;
 	char buf[BUFSIZ];
@@ -35,7 +49,7 @@ static int echo_cb(int type)
 	struct sockaddr_storage sa;
 	socklen_t sa_len = sizeof(sa);
 
-	len = recvfrom(sd, buf, sizeof(buf), MSG_DONTWAIT, (struct sockaddr *)&sa, &sa_len);
+	len = recv_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, &sa_len);
 	if (-1 == len)
 		return -1;	/* On error, close connection. */
 
@@ -43,9 +57,9 @@ static int echo_cb(int type)
 }
 
 static plugin_t plugin = {
-	.name  = "echo",	/* Must match the inetd /etc/services entry */
+	.name  = NAME,		/* 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>
  *
@@ -28,43 +28,73 @@
 
 #include "../plugin.h"
 
+#define NAME "time"
+
 /* UNIX epoch starts midnight, 1st Jan, 1970 */
 #define EPOCH_OFFSET 2208988800ULL
 
 /* Return number of seconds since midnight, 1st Jan, 1900 */
-static int rfc868(int type)
+static char *rfctime(char *buf, size_t *len)
 {
-	int sd = STDIN_FILENO;
 	time_t now;
-	struct sockaddr_storage sa;
-	socklen_t sa_len = sizeof(sa);
-
-	if (SOCK_DGRAM == type) {
-		int dummy;
-
-		/* Read empty datagram in UDP mode before sending reply. */
-		if (-1 == recvfrom(sd, &dummy, sizeof(dummy), MSG_DONTWAIT, (struct sockaddr *)&sa, &sa_len))
-			return -1;	/* On error, close connection. */
-	}
 
 	now = time(NULL);
 	if ((time_t)-1 == now)
-		return -1;		/* On error, close connection. */
+		return NULL;
 
-	/* Account for UNIX epoch offset */
+	/*
+	 * Account for UNIX epoch offset, and
+	 * convert to network byte order
+	 */
 	now += EPOCH_OFFSET;
+	now  = htonl(now);
 
-	/* Convert to network byte order, not explicitly stated in RFC */
+	*len = sizeof(now);
-	now = htonl(now);
+	memcpy(buf, &now, *len);
 
-	/* Send reply, ignore error, simply close connection. */
+	return buf;
-	return sendto(sd, &now, sizeof(now), MSG_DONTWAIT, (struct sockaddr *)&sa, sa_len);
+}
+
+static int recv_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t *sa_len)
+{
+	len = recvfrom(sd, buf, sizeof(buf), MSG_DONTWAIT, sa, sa_len);
+	if (-1 == len)
+		return -1;	/* On error, close connection. */
+
+	if (inetd_check_loop(sa, *sa_len, NAME))
+		return -1;
+
+	return 0;
+}
+
+static int send_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, socklen_t sa_len)
+{
+	char *now;
+
+	now = rfctime(buf, &len);
+	if (!now)
+		return -1;	/* On error, close connection. */
+
+	return sendto(sd, now, len, MSG_DONTWAIT, sa, sa_len);
+}
+
+static int cb(int type)
+{
+	int sd = STDIN_FILENO;
+	char buf[BUFSIZ];
+	struct sockaddr_storage sa;
+	socklen_t sa_len = sizeof(sa);
+
+	if (recv_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, &sa_len))
+		return -1;	/* On error, close connection. */
+
+	return send_peer(sd, buf, sizeof(buf), (struct sockaddr *)&sa, sa_len);
 }
 
 static plugin_t plugin = {
-	.name  = "time",	/* Must match the inetd /etc/services entry */
+	.name  = NAME,		/* Must match the inetd /etc/services entry */
 	.inetd = {
-		.cmd = rfc868
+		.cmd = cb
 	}
 };
 

service.c

@@ -589,6 +589,7 @@ recreate:
 	if (plugin) {
 		/* Internal plugin provides this service */
 		svc->inetd.cmd = plugin->inetd.cmd;
+		svc->inetd.builtin = 1;
 	} else {
 		strlcpy(svc->args[i++], cmd, sizeof(svc->args[0]));
 		while ((cmd = strtok(NULL, " ")))