1/*
2 * DNS support driver
3 *
4 * Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
5 * Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org>
6 *
7 * This is a simple DNS implementation for U-Boot. It will use the first IP
8 * in the DNS response as net_server_ip. This can then be used for any other
9 * network related activities.
10 *
11 * The packet handling is partly based on TADNS, original copyrights
12 * follow below.
13 *
14 */
15
16/*
17 * Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com>
18 *
19 * "THE BEER-WARE LICENSE" (Revision 42):
20 * Sergey Lyubka wrote this file.  As long as you retain this notice you
21 * can do whatever you want with this stuff. If we meet some day, and you think
22 * this stuff is worth it, you can buy me a beer in return.
23 */
24
25#include <common.h>
26#include <command.h>
27#include <env.h>
28#include <log.h>
29#include <net.h>
30#include <asm/unaligned.h>
31
32#include "dns.h"
33
34char *net_dns_resolve;	/* The host to resolve  */
35char *net_dns_env_var;	/* The envvar to store the answer in */
36
37static int dns_our_port;
38
39/*
40 * make port a little random (1024-17407)
41 * This keeps the math somewhat trivial to compute, and seems to work with
42 * all supported protocols/clients/servers
43 */
44static unsigned int random_port(void)
45{
46	return 1024 + (get_timer(0) % 0x4000);
47}
48
49static void dns_send(void)
50{
51	struct header *header;
52	int n, name_len;
53	uchar *p, *pkt;
54	const char *s;
55	const char *name;
56	enum dns_query_type qtype = DNS_A_RECORD;
57
58	name = net_dns_resolve;
59	pkt = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE);
60	p = pkt;
61
62	/* Prepare DNS packet header */
63	header           = (struct header *)pkt;
64	header->tid      = 1;
65	header->flags    = htons(0x100);	/* standard query */
66	header->nqueries = htons(1);		/* Just one query */
67	header->nanswers = 0;
68	header->nauth    = 0;
69	header->nother   = 0;
70
71	/* Encode DNS name */
72	name_len = strlen(name);
73	p = (uchar *)&header->data;	/* For encoding host name into packet */
74
75	do {
76		s = strchr(name, '.');
77		if (!s)
78			s = name + name_len;
79
80		n = s - name;			/* Chunk length */
81		*p++ = n;			/* Copy length  */
82		memcpy(p, name, n);		/* Copy chunk   */
83		p += n;
84
85		if (*s == '.')
86			n++;
87
88		name += n;
89		name_len -= n;
90	} while (*s != '\0');
91
92	*p++ = 0;			/* Mark end of host name */
93	*p++ = 0;			/* Some servers require double null */
94	*p++ = (unsigned char) qtype;	/* Query Type */
95
96	*p++ = 0;
97	*p++ = 1;				/* Class: inet, 0x0001 */
98
99	n = p - pkt;				/* Total packet length */
100	debug("Packet size %d\n", n);
101
102	dns_our_port = random_port();
103
104	net_send_udp_packet(net_server_ethaddr, net_dns_server,
105			    DNS_SERVICE_PORT, dns_our_port, n);
106	debug("DNS packet sent\n");
107}
108
109static void dns_timeout_handler(void)
110{
111	puts("Timeout\n");
112	net_set_state(NETLOOP_FAIL);
113}
114
115static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip,
116			unsigned src, unsigned len)
117{
118	struct header *header;
119	const unsigned char *p, *e, *s;
120	u16 type, i;
121	int found, stop, dlen;
122	char ip_str[22];
123	struct in_addr ip_addr;
124
125
126	debug("%s\n", __func__);
127	if (dest != dns_our_port)
128		return;
129
130	for (i = 0; i < len; i += 4)
131		debug("0x%p - 0x%.2x  0x%.2x  0x%.2x  0x%.2x\n",
132		      pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);
133
134	/* We sent one query. We want to have a single answer: */
135	header = (struct header *)pkt;
136	if (ntohs(header->nqueries) != 1)
137		return;
138
139	/* Received 0 answers */
140	if (header->nanswers == 0) {
141		puts("DNS: host not found\n");
142		net_set_state(NETLOOP_SUCCESS);
143		return;
144	}
145
146	/* Skip host name */
147	s = &header->data[0];
148	e = pkt + len;
149	for (p = s; p < e && *p != '\0'; p++)
150		continue;
151
152	/* We sent query class 1, query type 1 */
153	if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) {
154		puts("DNS: response was not an A record\n");
155		net_set_state(NETLOOP_SUCCESS);
156		return;
157	}
158
159	/* Go to the first answer section */
160	p += 5;
161
162	/* Loop through the answers, we want A type answer */
163	for (found = stop = 0; !stop && &p[12] < e; ) {
164		/* Skip possible name in CNAME answer */
165		if (*p != 0xc0) {
166			while (*p && &p[12] < e)
167				p++;
168			p--;
169		}
170		debug("Name (Offset in header): %d\n", p[1]);
171
172		type = get_unaligned_be16(p+2);
173		debug("type = %d\n", type);
174		if (type == DNS_CNAME_RECORD) {
175			/* CNAME answer. shift to the next section */
176			debug("Found canonical name\n");
177			dlen = get_unaligned_be16(p+10);
178			debug("dlen = %d\n", dlen);
179			p += 12 + dlen;
180		} else if (type == DNS_A_RECORD) {
181			debug("Found A-record\n");
182			found = 1;
183			stop = 1;
184		} else {
185			debug("Unknown type\n");
186			stop = 1;
187		}
188	}
189
190	if (found && &p[12] < e) {
191		dlen = get_unaligned_be16(p+10);
192		p += 12;
193		memcpy(&ip_addr, p, 4);
194
195		if (p + dlen <= e) {
196			ip_to_string(ip_addr, ip_str);
197			printf("%s\n", ip_str);
198			if (net_dns_env_var)
199				env_set(net_dns_env_var, ip_str);
200		} else {
201			puts("server responded with invalid IP number\n");
202		}
203	}
204
205	net_set_state(NETLOOP_SUCCESS);
206}
207
208void dns_start(void)
209{
210	debug("%s\n", __func__);
211
212	net_set_timeout_handler(DNS_TIMEOUT, dns_timeout_handler);
213	net_set_udp_handler(dns_handler);
214
215	/* Clear a previous MAC address, the server IP might have changed. */
216	memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr));
217
218	dns_send();
219}
220