Add new package for configuring 6rd tunnels.

[openwrt.git] / package / 6rd / src / 6rdcalc.c

diff --git a/package/6rd/src/6rdcalc.c b/package/6rd/src/6rdcalc.c
new file mode 100644 (file)
index 0000000..56e07d2
--- /dev/null
+++ b/package/6rd/src/6rdcalc.c
@@ -0,0 +1,126 @@
+/*
+ * Utility used to calculate the 6rd subnet.
+ *
+ * Copyright 2012, Stéphan Kochen <stephan@kochen.nl>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/errno.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+#define INET_PREFIXSTRLEN (INET_ADDRSTRLEN+3)
+#define INET6_PREFIXSTRLEN (INET6_ADDRSTRLEN+4)
+
+static void print_usage()
+{
+       fprintf(stderr, "Usage: 6rdcalc <v6 prefix>/<mask> <v4 address>/<mask>\n");
+       exit(1);
+}
+
+static void print_error()
+{
+       fprintf(stderr, "%s", strerror(errno));
+       exit(1);
+}
+
+static void parse_str(int af, char *str, void *addr, unsigned long *mask)
+{
+       int ret;
+       char *slash;
+
+       /* Split the address at the slash. */
+       if ((slash = strchr(str, '/')) == NULL)
+               print_usage();
+       *slash = '\0';
+
+       /* Parse the address. */
+       if ((ret = inet_pton(af, str, addr)) != 1) {
+               if (ret == 0)
+                       print_usage();
+               else
+                       print_error();
+       }
+
+       /* Parse the mask. */
+       *mask = strtoul(slash+1, NULL, 10);
+       if ((af == AF_INET  && *mask >  32) ||
+               (af == AF_INET6 && *mask > 128))
+               print_usage();
+}
+
+int main(int argc, const char **argv)
+{
+       char v6str[INET6_PREFIXSTRLEN], v4str[INET_PREFIXSTRLEN];
+       struct in6_addr v6;
+       struct in_addr v4;
+       unsigned long v6it, v4it, mask;
+       unsigned char *byte4, *byte6;
+       unsigned char bit4, bit6;
+
+       /* Check parameters. */
+       if (argc != 3)
+               print_usage();
+
+       /* Parse the v6 address. */
+       strncpy(v6str, argv[1], INET6_PREFIXSTRLEN);
+       v6str[INET6_PREFIXSTRLEN-1] = '\0';
+       parse_str(AF_INET6, v6str, &v6, &v6it);
+
+       /* Parse the v4 address */
+       strncpy(v4str, argv[2], INET_PREFIXSTRLEN);
+       v6str[INET_PREFIXSTRLEN-1] = '\0';
+       parse_str(AF_INET, v4str, &v4, &v4it);
+
+       /* Check if the combined mask is within bounds. */
+       mask = (32 - v4it) + v6it;
+       if (mask > 128)
+               print_usage();
+
+       /* Combine the addresses. */
+       while (v4it < 32) {
+               byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 3);
+               byte4 = (unsigned char *)(&v4.s_addr)  + (v4it >> 3);
+               bit6 = 128 >> (v6it & 0x07);
+               bit4 = 128 >> (v4it & 0x07);
+
+               if (*byte4 & bit4)
+                       *byte6 |= bit6;
+               else
+                       *byte6 &= ~bit6;
+
+               v4it++; v6it++;
+       }
+
+       /* Clear remaining bits. */
+       while (v6it < 128) {
+               byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 2);
+               bit6 = 128 >> (v6it & 0x07);
+
+               *byte6 &= ~bit6;
+
+               v6it++;
+       }
+
+       /* Print the subnet prefix. */
+       if (inet_ntop(AF_INET6, &v6, v6str, sizeof(v6str)) == NULL)
+               print_error();
+       printf("%s/%lu\n", v6str, mask);
+       return 0;
+}