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 */
36int 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