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/*
* DNS support driver
*
* Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
* Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org>
*
* This is a simple DNS implementation for U-Boot. It will use the first IP
* in the DNS response as net_server_ip. This can then be used for any other
* network related activities.
*
* The packet handling is partly based on TADNS, original copyrights
* follow below.
*
*/
/*
* Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com>
*
* "THE BEER-WARE LICENSE" (Revision 42):
* Sergey Lyubka wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return.
*/
#include <common.h>
#include <command.h>
#include <env.h>
#include <log.h>
#include <net.h>
#include <asm/unaligned.h>
#include "dns.h"
char *net_dns_resolve; /* The host to resolve */
char *net_dns_env_var; /* The envvar to store the answer in */
static int dns_our_port;
/*
* make port a little random (1024-17407)
* This keeps the math somewhat trivial to compute, and seems to work with
* all supported protocols/clients/servers
*/
static unsigned int random_port(void)
{
return 1024 + (get_timer(0) % 0x4000);
}
static void dns_send(void)
{
struct header *header;
int n, name_len;
uchar *p, *pkt;
const char *s;
const char *name;
enum dns_query_type qtype = DNS_A_RECORD;
name = net_dns_resolve;
pkt = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE);
p = pkt;
/* Prepare DNS packet header */
header = (struct header *)pkt;
header->tid = 1;
header->flags = htons(0x100); /* standard query */
header->nqueries = htons(1); /* Just one query */
header->nanswers = 0;
header->nauth = 0;
header->nother = 0;
/* Encode DNS name */
name_len = strlen(name);
p = (uchar *)&header->data; /* For encoding host name into packet */
do {
s = strchr(name, '.');
if (!s)
s = name + name_len;
n = s - name; /* Chunk length */
*p++ = n; /* Copy length */
memcpy(p, name, n); /* Copy chunk */
p += n;
if (*s == '.')
n++;
name += n;
name_len -= n;
} while (*s != '\0');
*p++ = 0; /* Mark end of host name */
*p++ = 0; /* Some servers require double null */
*p++ = (unsigned char) qtype; /* Query Type */
*p++ = 0;
*p++ = 1; /* Class: inet, 0x0001 */
n = p - pkt; /* Total packet length */
debug("Packet size %d\n", n);
dns_our_port = random_port();
net_send_udp_packet(net_server_ethaddr, net_dns_server,
DNS_SERVICE_PORT, dns_our_port, n);
debug("DNS packet sent\n");
}
static void dns_timeout_handler(void)
{
puts("Timeout\n");
net_set_state(NETLOOP_FAIL);
}
static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip,
unsigned src, unsigned len)
{
struct header *header;
const unsigned char *p, *e, *s;
u16 type, i;
int found, stop, dlen;
char ip_str[22];
struct in_addr ip_addr;
debug("%s\n", __func__);
if (dest != dns_our_port)
return;
for (i = 0; i < len; i += 4)
debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x\n",
pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);
/* We sent one query. We want to have a single answer: */
header = (struct header *)pkt;
if (ntohs(header->nqueries) != 1)
return;
/* Received 0 answers */
if (header->nanswers == 0) {
puts("DNS: host not found\n");
net_set_state(NETLOOP_SUCCESS);
return;
}
/* Skip host name */
s = &header->data[0];
e = pkt + len;
for (p = s; p < e && *p != '\0'; p++)
continue;
/* We sent query class 1, query type 1 */
if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) {
puts("DNS: response was not an A record\n");
net_set_state(NETLOOP_SUCCESS);
return;
}
/* Go to the first answer section */
p += 5;
/* Loop through the answers, we want A type answer */
for (found = stop = 0; !stop && &p[12] < e; ) {
/* Skip possible name in CNAME answer */
if (*p != 0xc0) {
while (*p && &p[12] < e)
p++;
p--;
}
debug("Name (Offset in header): %d\n", p[1]);
type = get_unaligned_be16(p+2);
debug("type = %d\n", type);
if (type == DNS_CNAME_RECORD) {
/* CNAME answer. shift to the next section */
debug("Found canonical name\n");
dlen = get_unaligned_be16(p+10);
debug("dlen = %d\n", dlen);
p += 12 + dlen;
} else if (type == DNS_A_RECORD) {
debug("Found A-record\n");
found = 1;
stop = 1;
} else {
debug("Unknown type\n");
stop = 1;
}
}
if (found && &p[12] < e) {
dlen = get_unaligned_be16(p+10);
p += 12;
memcpy(&ip_addr, p, 4);
if (p + dlen <= e) {
ip_to_string(ip_addr, ip_str);
printf("%s\n", ip_str);
if (net_dns_env_var)
env_set(net_dns_env_var, ip_str);
} else {
puts("server responded with invalid IP number\n");
}
}
net_set_state(NETLOOP_SUCCESS);
}
void dns_start(void)
{
debug("%s\n", __func__);
net_set_timeout_handler(DNS_TIMEOUT, dns_timeout_handler);
net_set_udp_handler(dns_handler);
/* Clear a previous MAC address, the server IP might have changed. */
memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr));
dns_send();
}
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