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/*
* Copyright 2011 Daniel Drown
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* dns64.c - find the nat64 prefix with a dns64 lookup
*/
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <strings.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "dns64.h"
#include "logging.h"
#include "resolv_netid.h"
/* function: plat_prefix
* looks up an ipv4-only hostname and looks for a nat64 /96 prefix, returns 1 on success, 0 on failure
* ipv4_name - name to lookup
* net_id - (optional) netId to use, NETID_UNSET indicates use of default network
* prefix - the plat /96 prefix
*/
int plat_prefix(const char *ipv4_name, unsigned net_id, struct in6_addr *prefix) {
const struct addrinfo hints = {
.ai_family = AF_INET6,
};
int status;
struct addrinfo *result = NULL;
struct in6_addr plat_addr;
char plat_addr_str[INET6_ADDRSTRLEN];
logmsg(ANDROID_LOG_INFO, "Detecting NAT64 prefix from DNS...");
status = android_getaddrinfofornet(ipv4_name, NULL, &hints, net_id, MARK_UNSET, &result);
if (status != 0 || result == NULL) {
logmsg(ANDROID_LOG_ERROR, "plat_prefix/dns(%s) status = %d/%s",
ipv4_name, status, gai_strerror(status));
return 0;
}
// Use only the first result. If other records are present, possibly with
// differing DNS64 prefixes they are ignored (there is very little sensible
// that could be done with them at this time anyway).
if (result->ai_family != AF_INET6) {
logmsg(ANDROID_LOG_WARN, "plat_prefix/unexpected address family: %d", result->ai_family);
return 0;
}
plat_addr = ((struct sockaddr_in6 *)result->ai_addr)->sin6_addr;
// Only /96 DNS64 prefixes are supported at this time.
plat_addr.s6_addr32[3] = 0;
freeaddrinfo(result);
logmsg(ANDROID_LOG_INFO, "Detected NAT64 prefix %s/96",
inet_ntop(AF_INET6, &plat_addr, plat_addr_str, sizeof(plat_addr_str)));
*prefix = plat_addr;
return 1;
}
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