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
dns_send(void)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
dns_timeout_handler(void)97 static void dns_timeout_handler(void)
98 {
99 puts("Timeout\n");
100 net_set_state(NETLOOP_FAIL);
101 }
102
dns_handler(uchar * pkt,unsigned dest,struct in_addr sip,unsigned src,unsigned len)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 env_set(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
dns_start(void)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