xref: /openbmc/u-boot/net/dns.c (revision 7da8680b)
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 <net.h>
28 #include <asm/unaligned.h>
29 
30 #include "dns.h"
31 
32 char *net_dns_resolve;	/* The host to resolve  */
33 char *net_dns_env_var;	/* The envvar to store the answer in */
34 
35 static int dns_our_port;
36 
37 static void dns_send(void)
38 {
39 	struct header *header;
40 	int n, name_len;
41 	uchar *p, *pkt;
42 	const char *s;
43 	const char *name;
44 	enum dns_query_type qtype = DNS_A_RECORD;
45 
46 	name = net_dns_resolve;
47 	pkt = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE);
48 	p = pkt;
49 
50 	/* Prepare DNS packet header */
51 	header           = (struct header *)pkt;
52 	header->tid      = 1;
53 	header->flags    = htons(0x100);	/* standard query */
54 	header->nqueries = htons(1);		/* Just one query */
55 	header->nanswers = 0;
56 	header->nauth    = 0;
57 	header->nother   = 0;
58 
59 	/* Encode DNS name */
60 	name_len = strlen(name);
61 	p = (uchar *)&header->data;	/* For encoding host name into packet */
62 
63 	do {
64 		s = strchr(name, '.');
65 		if (!s)
66 			s = name + name_len;
67 
68 		n = s - name;			/* Chunk length */
69 		*p++ = n;			/* Copy length  */
70 		memcpy(p, name, n);		/* Copy chunk   */
71 		p += n;
72 
73 		if (*s == '.')
74 			n++;
75 
76 		name += n;
77 		name_len -= n;
78 	} while (*s != '\0');
79 
80 	*p++ = 0;			/* Mark end of host name */
81 	*p++ = 0;			/* Some servers require double null */
82 	*p++ = (unsigned char) qtype;	/* Query Type */
83 
84 	*p++ = 0;
85 	*p++ = 1;				/* Class: inet, 0x0001 */
86 
87 	n = p - pkt;				/* Total packet length */
88 	debug("Packet size %d\n", n);
89 
90 	dns_our_port = random_port();
91 
92 	net_send_udp_packet(net_server_ethaddr, net_dns_server,
93 			    DNS_SERVICE_PORT, dns_our_port, n);
94 	debug("DNS packet sent\n");
95 }
96 
97 static void dns_timeout_handler(void)
98 {
99 	puts("Timeout\n");
100 	net_set_state(NETLOOP_FAIL);
101 }
102 
103 static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip,
104 			unsigned src, unsigned len)
105 {
106 	struct header *header;
107 	const unsigned char *p, *e, *s;
108 	u16 type, i;
109 	int found, stop, dlen;
110 	char ip_str[22];
111 	struct in_addr ip_addr;
112 
113 
114 	debug("%s\n", __func__);
115 	if (dest != dns_our_port)
116 		return;
117 
118 	for (i = 0; i < len; i += 4)
119 		debug("0x%p - 0x%.2x  0x%.2x  0x%.2x  0x%.2x\n",
120 		      pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);
121 
122 	/* We sent one query. We want to have a single answer: */
123 	header = (struct header *)pkt;
124 	if (ntohs(header->nqueries) != 1)
125 		return;
126 
127 	/* Received 0 answers */
128 	if (header->nanswers == 0) {
129 		puts("DNS: host not found\n");
130 		net_set_state(NETLOOP_SUCCESS);
131 		return;
132 	}
133 
134 	/* Skip host name */
135 	s = &header->data[0];
136 	e = pkt + len;
137 	for (p = s; p < e && *p != '\0'; p++)
138 		continue;
139 
140 	/* We sent query class 1, query type 1 */
141 	if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) {
142 		puts("DNS: response was not an A record\n");
143 		net_set_state(NETLOOP_SUCCESS);
144 		return;
145 	}
146 
147 	/* Go to the first answer section */
148 	p += 5;
149 
150 	/* Loop through the answers, we want A type answer */
151 	for (found = stop = 0; !stop && &p[12] < e; ) {
152 		/* Skip possible name in CNAME answer */
153 		if (*p != 0xc0) {
154 			while (*p && &p[12] < e)
155 				p++;
156 			p--;
157 		}
158 		debug("Name (Offset in header): %d\n", p[1]);
159 
160 		type = get_unaligned_be16(p+2);
161 		debug("type = %d\n", type);
162 		if (type == DNS_CNAME_RECORD) {
163 			/* CNAME answer. shift to the next section */
164 			debug("Found canonical name\n");
165 			dlen = get_unaligned_be16(p+10);
166 			debug("dlen = %d\n", dlen);
167 			p += 12 + dlen;
168 		} else if (type == DNS_A_RECORD) {
169 			debug("Found A-record\n");
170 			found = 1;
171 			stop = 1;
172 		} else {
173 			debug("Unknown type\n");
174 			stop = 1;
175 		}
176 	}
177 
178 	if (found && &p[12] < e) {
179 		dlen = get_unaligned_be16(p+10);
180 		p += 12;
181 		memcpy(&ip_addr, p, 4);
182 
183 		if (p + dlen <= e) {
184 			ip_to_string(ip_addr, ip_str);
185 			printf("%s\n", ip_str);
186 			if (net_dns_env_var)
187 				setenv(net_dns_env_var, ip_str);
188 		} else {
189 			puts("server responded with invalid IP number\n");
190 		}
191 	}
192 
193 	net_set_state(NETLOOP_SUCCESS);
194 }
195 
196 void dns_start(void)
197 {
198 	debug("%s\n", __func__);
199 
200 	net_set_timeout_handler(DNS_TIMEOUT, dns_timeout_handler);
201 	net_set_udp_handler(dns_handler);
202 
203 	/* Clear a previous MAC address, the server IP might have changed. */
204 	memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr));
205 
206 	dns_send();
207 }
208