Add protection against UDP inetd looping attacks

This patch adds protection against a common inetd attack vector wherein
the reply port to UDP inetd services is forged to an internal inetd
service port.

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

plugins/daytime.c

@@ -28,6 +28,9 @@
 
 #include "../plugin.h"
 
+#define NAME "daytime"
+
+
 static char *daytime(char *buf, size_t len)
 {
 	time_t t;
@@ -48,6 +51,9 @@ static int recv_peer(int sd, char *buf, ssize_t len, struct sockaddr *sa, sockle
 	if (-1 == len)
 		return -1;	/* On error, close connection. */
 
+	if (inetd_check_loop(sa, *sa_len, NAME))
+		return -1;
+
 	return 0;
 } 
 
@@ -72,7 +78,7 @@ static int cb(int type)
 }
 
 static plugin_t plugin = {
-	.name  = "daytime",	/* Must match the inetd /etc/services entry */
+	.name  = NAME,		/* Must match the inetd /etc/services entry */
 	.inetd = {
 		.cmd = cb
 	}