1 /*
2 * Copyright 2011 Daniel Drown
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * dns64.c - find the nat64 prefix with a dns64 lookup
17 */
18
19 #include <sys/socket.h>
20 #include <netinet/in.h>
21 #include <arpa/inet.h>
22 #include <netdb.h>
23 #include <strings.h>
24 #include <stdio.h>
25 #include <stdlib.h>
26 #include <unistd.h>
27
28 #include "dns64.h"
29 #include "logging.h"
30
31 /* function: plat_prefix
32 * looks up an ipv4-only hostname and looks for a nat64 /96 prefix, returns 1 on success, 0 on temporary failure, -1 on permanent failure
33 * ipv4_name - name to lookup
34 * prefix - the plat /96 prefix
35 */
plat_prefix(const char * ipv4_name,struct in6_addr * prefix)36 int plat_prefix(const char *ipv4_name, struct in6_addr *prefix) {
37 struct addrinfo hints, *result, *p;
38 int status, plat_addr_set, ipv4_records, ipv6_records;
39 struct in6_addr plat_addr, this_plat_addr;
40 struct sockaddr_in6 *this_addr;
41 char plat_addr_str[INET6_ADDRSTRLEN];
42
43 logmsg(ANDROID_LOG_INFO, "Detecting NAT64 prefix from DNS...");
44
45 result = NULL;
46 plat_addr_set = 0;
47 ipv4_records = ipv6_records = 0;
48
49 bzero(&hints, sizeof(hints));
50 hints.ai_family = AF_UNSPEC;
51 status = getaddrinfo(ipv4_name, NULL, &hints, &result);
52 if(status != 0) {
53 logmsg(ANDROID_LOG_ERROR,"plat_prefix/dns(%s) status = %d/%s\n", ipv4_name, status, gai_strerror(status));
54 return 0;
55 }
56
57 for(p = result; p; p = p->ai_next) {
58 if(p->ai_family == AF_INET) {
59 ipv4_records++;
60 continue;
61 }
62 if(p->ai_family != AF_INET6) {
63 logmsg(ANDROID_LOG_WARN,"plat_prefix/unexpected address family: %d\n", p->ai_family);
64 continue;
65 }
66 ipv6_records++;
67 this_addr = (struct sockaddr_in6 *)p->ai_addr;
68 this_plat_addr = this_addr->sin6_addr;
69 this_plat_addr.s6_addr32[3] = 0;
70
71 if(!plat_addr_set) {
72 plat_addr = this_plat_addr;
73 plat_addr_set = 1;
74 continue;
75 }
76
77 inet_ntop(AF_INET6, &plat_addr, plat_addr_str, sizeof(plat_addr_str));
78 if(!IN6_ARE_ADDR_EQUAL(&plat_addr, &this_plat_addr)) {
79 char this_plat_addr_str[INET6_ADDRSTRLEN];
80 inet_ntop(AF_INET6, &this_plat_addr, this_plat_addr_str, sizeof(this_plat_addr_str));
81 logmsg(ANDROID_LOG_ERROR,"plat_prefix/two different plat addrs = %s,%s",
82 plat_addr_str,this_plat_addr_str);
83 }
84 }
85 if(result != NULL) {
86 freeaddrinfo(result);
87 }
88 if(ipv4_records > 0 && ipv6_records == 0) {
89 logmsg(ANDROID_LOG_WARN,"plat_prefix/no dns64 detected\n");
90 return -1;
91 }
92
93 logmsg(ANDROID_LOG_INFO, "Detected NAT64 prefix %s/96", plat_addr_str);
94 *prefix = plat_addr;
95 return 1;
96 }
97