diff options
Diffstat (limited to 'ipcalc-reverse.c')
| -rw-r--r-- | ipcalc-reverse.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/ipcalc-reverse.c b/ipcalc-reverse.c new file mode 100644 index 0000000..3863ef6 --- /dev/null +++ b/ipcalc-reverse.c @@ -0,0 +1,127 @@ +/* + * Copyright (c) 2015 Red Hat, Inc. All rights reserved. + * + * 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, see <http://www.gnu.org/licenses/>. + * + * Authors: + * Nikos Mavrogiannopoulos <nmav@redhat.com> + */ + +#define _GNU_SOURCE /* asprintf */ +#include <ctype.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/socket.h> +#include <sys/types.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#include <stdarg.h> +#include "ipcalc.h" + +/* draft-ietf-dnsop-rfc2317bis-00 replaces that legacy style + */ +#undef USE_RFC2317_STYLE + +char *calc_reverse_dns4(struct in_addr ip, unsigned prefix, struct in_addr network, struct in_addr broadcast) +{ + char *str = NULL; + int ret = -1; + + unsigned byte1 = (ntohl(ip.s_addr) >> 24) & 0xff; + unsigned byte2 = (ntohl(ip.s_addr) >> 16) & 0xff; + unsigned byte3 = (ntohl(ip.s_addr) >> 8) & 0xff; + unsigned byte4 = (ntohl(ip.s_addr)) & 0xff; + +#ifdef USE_RFC2317_STYLE + if (prefix == 32) { + ret = asprintf(&str, "%u.%u.%u.%u.in-addr.arpa.", byte4, byte3, byte2, byte1); + } else if (prefix == 24) { + ret = asprintf(&str, "%u.%u.%u.in-addr.arpa.", byte3, byte2, byte1); + } else if (prefix == 16) { + ret = asprintf(&str, "%u.%u.in-addr.arpa.", byte2, byte1); + } else if (prefix == 8) { + ret = asprintf(&str, "%u.in-addr.arpa.", byte1); + } else if (prefix > 24) { + ret = asprintf(&str, "%u/%u.%u.%u.%u.in-addr.arpa.", byte4, prefix, byte3, byte2, byte1); + } else if (prefix > 16) { + ret = asprintf(&str, "%u/%u.%u.%u.in-addr.arpa.", byte3, prefix, byte2, byte1); + } else if (prefix > 8) { + ret = asprintf(&str, "%u/%u.%u.in-addr.arpa.", byte2, prefix, byte1); + } +#else + if (prefix == 32) { + ret = asprintf(&str, "%u.%u.%u.%u.in-addr.arpa.", byte4, byte3, byte2, byte1); + } else if (prefix == 24) { + ret = asprintf(&str, "%u.%u.%u.in-addr.arpa.", byte3, byte2, byte1); + } else if (prefix == 16) { + ret = asprintf(&str, "%u.%u.in-addr.arpa.", byte2, byte1); + } else if (prefix == 8) { + ret = asprintf(&str, "%u.in-addr.arpa.", byte1); + } else if (prefix > 24) { + unsigned min = (ntohl(network.s_addr)) & 0xff; + unsigned max = (ntohl(broadcast.s_addr)) & 0xff; + ret = asprintf(&str, "%u-%u.%u.%u.%u.in-addr.arpa.", min, max, byte3, byte2, byte1); + } else if (prefix > 16) { + unsigned min = (ntohl(network.s_addr) >> 8) & 0xff; + unsigned max = (ntohl(broadcast.s_addr) >> 8) & 0xff; + ret = asprintf(&str, "%u-%u.%u.%u.in-addr.arpa.", min, max, byte2, byte1); + } else if (prefix > 8) { + unsigned min = (ntohl(network.s_addr) >> 16) & 0xff; + unsigned max = (ntohl(broadcast.s_addr) >> 16) & 0xff; + ret = asprintf(&str, "%u-%u.%u.in-addr.arpa.", min, max, byte1); + } +#endif + + if (ret == -1) + return NULL; + return str; +} + +static char hexchar(unsigned int val) +{ + if (val < 10) + return '0' + val; + if (val < 16) + return 'a' + val - 10; + abort(); +} + +char *calc_reverse_dns6(struct in6_addr *ip, unsigned prefix) +{ + unsigned i, j = 0; + char str[256]; + unsigned max = prefix/8; + + if (prefix % 4 != 0) + return NULL; + + if (prefix % 8 == 4) { + str[j++] = hexchar(ip->s6_addr[(prefix+4)/8-1] >> 4); + str[j++] = '.'; + } + + for (i=0;i<max;i++) { + str[j++] = hexchar(ip->s6_addr[max-1-i] & 0xf); + str[j++] = '.'; + + str[j++] = hexchar(ip->s6_addr[max-1-i] >> 4); + str[j++] = '.'; + + } + + strcpy(&str[j], "ip6.arpa."); + + return strdup(str); +} |