adds the ability to use and calculate network prefix specifications instead

of netmasks. It also fixes the parameters for network and netmask to match
that of the official Red Hat version (-n for network and -m for netmask).
Patch by Joshua Jackson

networking/Config.in

@@ -376,11 +376,11 @@ config CONFIG_IPCALC
 	  resulting broadcast, network, and host range.
 
 config CONFIG_FEATURE_IPCALC_FANCY
-	bool "  Fancy IPCALC, more options, adds 300 bytes"
+	bool "  Fancy IPCALC, more options, adds 1 kbyte"
 	default y
 	depends on CONFIG_IPCALC
 	help
-	  Adds the fields hostname and silent to the output of "ipcalc".
+	  Adds the options hostname, prefix and silent to the output of "ipcalc".
 
 config CONFIG_IPADDR
 	bool "ipaddr"

networking/ipcalc.c

@@ -40,11 +40,29 @@ static unsigned long get_netmask(unsigned long ipaddr)
 		return 0;
 }
 
+#ifdef CONFIG_FEATURE_IPCALC_FANCY
+static int get_prefix(unsigned long netmask)
+{
+        unsigned long t;
+        int ret = 0;
+
+        for (t = 0; t < 32; t++) {
+                if (htonl(netmask) & (0x80000000 >> t)) {
+                        ret ++;
+                } else {
+                        break;
+                }
+        }
+        return ret;
+}
+#endif
+
 #define NETMASK   0x01
 #define BROADCAST 0x02
 #define NETWORK   0x04
-#define HOSTNAME  0x08
+#define NETPREFIX 0x08
-#define SILENT    0x10
+#define HOSTNAME  0x10
+#define SILENT    0x80
 
 int ipcalc_main(int argc, char **argv)
 {
@@ -55,11 +73,18 @@ int ipcalc_main(int argc, char **argv)
 	unsigned long network;
 	unsigned long ipaddr;
 
-	static const struct option long_options[] = {
-		{"netmask", no_argument, NULL, 'n'},
-		{"broadcast", no_argument, NULL, 'b'},
-		{"network", no_argument, NULL, 'w'},
 #ifdef CONFIG_FEATURE_IPCALC_FANCY
+	unsigned long netprefix = 0;
+	int have_netmask = 0;
+	char *ipstr, *prefixstr;
+#endif
+
+	static const struct option long_options[] = {
+		{"netmask", no_argument, NULL, 'm'},
+		{"broadcast", no_argument, NULL, 'b'},
+		{"network", no_argument, NULL, 'n'},
+#ifdef CONFIG_FEATURE_IPCALC_FANCY
+                {"prefix", no_argument, NULL, 'p'},
 		{"hostname", no_argument, NULL, 'h'},
 		{"silent", no_argument, NULL, 's'},
 #endif
@@ -69,11 +94,11 @@ int ipcalc_main(int argc, char **argv)
 	bb_applet_long_options = long_options;
 	mode = bb_getopt_ulflags(argc, argv,
 #ifdef CONFIG_FEATURE_IPCALC_FANCY
-							  "nbwhs");
+							  "mbnphs");
 #else
-							  "nbw");
+							  "mbn");
 #endif
-	if (mode & (BROADCAST | NETWORK)) {
+	if (mode & (BROADCAST | NETWORK | NETPREFIX)) {
 		if (argc - optind > 2) {
 			bb_show_usage();
 		}
@@ -83,15 +108,54 @@ int ipcalc_main(int argc, char **argv)
 		}
 	}
 
+#ifdef CONFIG_FEATURE_IPCALC_FANCY
+        prefixstr = ipstr = argv[optind];
+
+        while(*prefixstr) {
+                if (*prefixstr == '/') {
+                        *prefixstr = (char)0;
+                        prefixstr++;
+                        if (*prefixstr) {
+                                netprefix = atol(prefixstr);
+                                if (netprefix > 32) {
+                                        IPCALC_MSG(bb_error_msg_and_die("bad IP prefix: %s\n", prefixstr),
+                                                exit(EXIT_FAILURE));
+                                }
+                                if (netprefix) {
+                                        netmask = 0x80000000;
+                                        netprefix--;
+                                        while(netprefix) {
+                                                netmask = 0x80000000 | (netmask >> 1);
+                                                netprefix--;
+                                        }
+                                        netmask = htonl(netmask);
+                                }
+                                /* Even if it was 0, we will signify that we have a netmask. This allows */
+                                /* for specification of default routes, etc which have a 0 netmask/prefix */
+                                have_netmask = 1;
+                        }
+                        break;
+                }
+                prefixstr++;
+        }
+	ipaddr = inet_addr(ipstr);
+#else
 	ipaddr = inet_addr(argv[optind]);
+#endif
 
 	if (ipaddr == INADDR_NONE) {
 		IPCALC_MSG(bb_error_msg_and_die("bad IP address: %s", argv[optind]),
 				   exit(EXIT_FAILURE));
 	}
 
-
 	if (argc - optind == 2) {
+#ifdef CONFIG_FEATURE_IPCALC_FANCY
+               if (have_netmask == 1) {
+                        IPCALC_MSG(bb_error_msg_and_die("Both prefix and netmask were specified, use one or the other.\n"),
+                                exit(EXIT_FAILURE));
+                }
+                have_netmask = 1;
+#endif
                 netmask = inet_addr(argv[optind + 1]);
 	}
 
@@ -118,7 +182,12 @@ int ipcalc_main(int argc, char **argv)
 		network = ipaddr & netmask;
 		printf("NETWORK=%s\n", inet_ntoa((*(struct in_addr *) &network)));
 	}
+
 #ifdef CONFIG_FEATURE_IPCALC_FANCY
+        if (mode & NETPREFIX) {
+                printf("PREFIX=%i\n", get_prefix(netmask));
+        }
+
 	if (mode & HOSTNAME) {
 		struct hostent *hostinfo;
 		int x;