a752c7ab
 elopes
add first test an...
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/*
* Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup net_sock_dns
* @{
* @file
* @brief sock DNS client implementation
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @}
*/
#include <string.h>
#include <stdio.h>
#include "net/sock/udp.h"
#include "net/sock/dns.h"
#ifdef RIOT_VERSION
#include "byteorder.h"
#endif
/* min domain name length is 1, so minimum record length is 7 */
#define DNS_MIN_REPLY_LEN (unsigned)(sizeof(sock_dns_hdr_t ) + 7)
static ssize_t _enc_domain_name(uint8_t *out, const char *domain_name)
{
/*
* DNS encodes domain names with "<len><part><len><part>", e.g.,
* "example.org" ends up as "\7example\3org" in the packet.
*/
uint8_t *part_start = out;
uint8_t *out_pos = ++out;
char c;
while ((c = *domain_name)) {
if (c == '.') {
/* replace dot with length of name part as byte */
*part_start = (out_pos - part_start - 1);
part_start = out_pos++;
}
else {
*out_pos++ = c;
}
domain_name++;
}
*part_start = (out_pos - part_start - 1);
*out_pos++ = 0;
return out_pos - out + 1;
}
static unsigned _put_short(uint8_t *out, uint16_t val)
{
memcpy(out, &val, 2);
return 2;
}
static unsigned _get_short(uint8_t *buf)
{
uint16_t _tmp;
memcpy(&_tmp, buf, 2);
return _tmp;
}
static size_t _skip_hostname(uint8_t *buf)
{
uint8_t *bufpos = buf;
/* handle DNS Message Compression */
if (*bufpos >= 192) {
return 2;
}
while(*bufpos) {
bufpos += *bufpos + 1;
}
return (bufpos - buf + 1);
}
static int _parse_dns_reply(uint8_t *buf, size_t len, void* addr_out, int family)
{
sock_dns_hdr_t *hdr = (sock_dns_hdr_t*) buf;
uint8_t *bufpos = buf + sizeof(*hdr);
/* skip all queries that are part of the reply */
for (unsigned n = 0; n < ntohs(hdr->qdcount); n++) {
bufpos += _skip_hostname(bufpos);
bufpos += 4; /* skip type and class of query */
}
for (unsigned n = 0; n < ntohs(hdr->ancount); n++) {
bufpos += _skip_hostname(bufpos);
uint16_t _type = ntohs(_get_short(bufpos));
bufpos += 2;
uint16_t class = ntohs(_get_short(bufpos));
bufpos += 2;
bufpos += 4; /* skip ttl */
unsigned addrlen = ntohs(_get_short(bufpos));
bufpos += 2;
if ((bufpos + addrlen) > (buf + len)) {
return -EBADMSG;
}
/* skip unwanted answers */
if ((class != DNS_CLASS_IN) ||
((_type == DNS_TYPE_A) && (family == AF_INET6)) ||
((_type == DNS_TYPE_AAAA) && (family == AF_INET)) ||
! ((_type == DNS_TYPE_A) || ((_type == DNS_TYPE_AAAA))
)) {
bufpos += addrlen;
continue;
}
memcpy(addr_out, bufpos, addrlen);
return addrlen;
}
return -1;
}
int sock_dns_query(const char *domain_name, void *addr_out, int family)
{
uint8_t buf[SOCK_DNS_QUERYBUF_LEN];
uint8_t reply_buf[512];
if (strlen(domain_name) > SOCK_DNS_MAX_NAME_LEN) {
return -ENOSPC;
}
sock_dns_hdr_t *hdr = (sock_dns_hdr_t*) buf;
memset(hdr, 0, sizeof(*hdr));
hdr->id = 0; /* random? */
hdr->flags = htons(0x0120);
hdr->qdcount = htons(1 + (family == AF_UNSPEC));
uint8_t *bufpos = buf + sizeof(*hdr);
unsigned _name_ptr;
if ((family == AF_INET6) || (family == AF_UNSPEC)) {
_name_ptr = (bufpos - buf);
bufpos += _enc_domain_name(bufpos, domain_name);
bufpos += _put_short(bufpos, htons(DNS_TYPE_AAAA));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
if ((family == AF_INET) || (family == AF_UNSPEC)) {
if (family == AF_UNSPEC) {
bufpos += _put_short(bufpos, htons((0xc000) | (_name_ptr)));
}
else {
bufpos += _enc_domain_name(bufpos, domain_name);
}
bufpos += _put_short(bufpos, htons(DNS_TYPE_A));
bufpos += _put_short(bufpos, htons(DNS_CLASS_IN));
}
sock_udp_t sock_dns;
ssize_t res = sock_udp_create(&sock_dns, NULL, &sock_dns_server, 0);
if (res) {
puts("a");
goto out;
}
for (int i = 0; i < SOCK_DNS_RETRIES; i++) {
res = sock_udp_send(&sock_dns, buf, (bufpos-buf), NULL);
if (res <= 0) {
continue;
}
res = sock_udp_recv(&sock_dns, reply_buf, sizeof(reply_buf), 1000000LU, NULL);
if ((res > 0) && (res > (int)DNS_MIN_REPLY_LEN)) {
if ((res = _parse_dns_reply(reply_buf, res, addr_out, family)) > 0) {
goto out;
}
}
}
out:
sock_udp_close(&sock_dns);
return res;
}
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