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 #include "NetdClient.h" 31 #include "resolv_netid.h" 32 33 /* function: plat_prefix 34 * looks up an ipv4-only hostname and looks for a nat64 /96 prefix, returns 1 on success, 0 on failure 35 * ipv4_name - name to lookup 36 * net_id - (optional) netId to use, NETID_UNSET indicates use of default network 37 * prefix - the plat /96 prefix 38 */ 39 int plat_prefix(const char *ipv4_name, unsigned net_id, struct in6_addr *prefix) { 40 const struct addrinfo hints = { 41 .ai_family = AF_INET6, 42 }; 43 int status; 44 struct addrinfo *result = NULL; 45 struct in6_addr plat_addr; 46 char plat_addr_str[INET6_ADDRSTRLEN]; 47 48 logmsg(ANDROID_LOG_INFO, "Detecting NAT64 prefix from DNS..."); 49 50 // Be sure to query local DNS64 servers, bypassing Private DNS (if enabled). 51 if (net_id != NETID_UNSET) { 52 net_id |= NETID_USE_LOCAL_NAMESERVERS; 53 } 54 55 status = android_getaddrinfofornet(ipv4_name, NULL, &hints, net_id, MARK_UNSET, &result); 56 if (status != 0 || result == NULL) { 57 logmsg(ANDROID_LOG_ERROR, "plat_prefix/dns(%s) status = %d/%s", 58 ipv4_name, status, gai_strerror(status)); 59 return 0; 60 } 61 62 // Use only the first result. If other records are present, possibly with 63 // differing DNS64 prefixes they are ignored (there is very little sensible 64 // that could be done with them at this time anyway). 65 66 if (result->ai_family != AF_INET6) { 67 logmsg(ANDROID_LOG_WARN, "plat_prefix/unexpected address family: %d", result->ai_family); 68 return 0; 69 } 70 plat_addr = ((struct sockaddr_in6 *)result->ai_addr)->sin6_addr; 71 // Only /96 DNS64 prefixes are supported at this time. 72 plat_addr.s6_addr32[3] = 0; 73 freeaddrinfo(result); 74 75 logmsg(ANDROID_LOG_INFO, "Detected NAT64 prefix %s/96", 76 inet_ntop(AF_INET6, &plat_addr, plat_addr_str, sizeof(plat_addr_str))); 77 *prefix = plat_addr; 78 return 1; 79 } 80
