--- a/hosts_access.5
+++ b/hosts_access.5
@@ -90,6 +90,9 @@ bitwise AND of the address and the `mask
 pattern `131.155.72.0/255.255.254.0' matches every address in the
 range `131.155.72.0' through `131.155.73.255'.
 .IP \(bu
+An expression of the form `n.n.n.n/m\' is interpreted as a
+`net/prefixlen\' pair, as below, for IPv4 addresses.
+.IP \(bu
 A string that begins with a `/' character is treated as a file
 name. A host name or address is matched if it matches any host name
 or address pattern listed in the named file. The file format is
--- a/tcpd.h
+++ b/tcpd.h
@@ -95,6 +95,7 @@ extern void refuse __P((struct request_i
 extern char *xgets __P((char *, int, FILE *));	/* fgets() on steroids */
 extern char *split_at __P((char *, int));	/* strchr() and split */
 extern unsigned long dot_quad_addr __P((char *)); /* restricted inet_addr() */
+extern unsigned long prefix_to_netmask __P((char *)); /* 0-32 prefix length */
 
 /* Global variables. */
 
--- a/misc.c
+++ b/misc.c
@@ -14,6 +14,8 @@ static char sccsic[] = "@(#) misc.c 1.2
 #include <arpa/inet.h>
 #include <stdio.h>
 #include <string.h>
+#include <ctype.h>
+#include <stdlib.h>
 
 #include "tcpd.h"
 
@@ -85,3 +87,22 @@ char   *str;
     }
     return (runs == 4 ? inet_addr(str) : INADDR_NONE);
 }
+
+/* prefix_to_netmask - convert prefix (0-32) to netmask */
+
+unsigned long prefix_to_netmask(str)
+char	*str;
+{
+    unsigned long prefix;
+    char *endptr;
+
+    if (!isdigit(str[0]))
+	return INADDR_NONE;
+
+    prefix = strtoul(str, &endptr, 10);
+    if ((endptr == str) || (*endptr != '\0') || (prefix > 32))
+	return INADDR_NONE;
+
+    return htonl(~0UL << (32 - prefix));
+}
+
--- a/hosts_access.c
+++ b/hosts_access.c
@@ -345,7 +345,12 @@ char   *string;
     if ((addr = dot_quad_addr(string)) == INADDR_NONE)
 	return (NO);
     if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
-	|| (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
+	|| ((mask = dot_quad_addr(mask_tok)) == INADDR_NONE
+	    && strcmp(mask_tok, "255.255.255.255")
+	    && (mask = prefix_to_netmask(mask_tok)) == INADDR_NONE
+	    && strcmp(mask_tok, "32"))) {
+	/* 255.255.255.255 == INADDR_NONE, separate check needed. TJ. */
+	/* 32 == INADDR_NONE, separate check needed. philipp */
 	tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
 	return (NO);				/* not tcpd_jump() */
     }