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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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