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Robin Getz1a32bf42009-07-20 14:53:54 -04001/*
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 NetServerIP. 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
29#include "dns.h"
30
31char *NetDNSResolve; /* The host to resolve */
32char *NetDNSenvvar; /* The envvar to store the answer in */
33
34static int DnsOurPort;
35
36static void
37DnsSend(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 = NetDNSResolve;
47 pkt = p = (uchar *)(NetTxPacket + NetEthHdrSize() + IP_HDR_SIZE);
48
49 /* Prepare DNS packet header */
50 header = (struct header *) pkt;
51 header->tid = 1;
52 header->flags = htons(0x100); /* standard query */
53 header->nqueries = htons(1); /* Just one query */
54 header->nanswers = 0;
55 header->nauth = 0;
56 header->nother = 0;
57
58 /* Encode DNS name */
59 name_len = strlen(name);
60 p = (uchar *) &header->data; /* For encoding host name into packet */
61
62 do {
63 s = strchr(name, '.');
64 if (!s)
65 s = name + name_len;
66
67 n = s - name; /* Chunk length */
68 *p++ = n; /* Copy length */
69 memcpy(p, name, n); /* Copy chunk */
70 p += n;
71
72 if (*s == '.')
73 n++;
74
75 name += n;
76 name_len -= n;
77 } while (*s != '\0');
78
79 *p++ = 0; /* Mark end of host name */
80 *p++ = 0; /* Some servers require double null */
81 *p++ = (unsigned char) qtype; /* Query Type */
82
83 *p++ = 0;
84 *p++ = 1; /* Class: inet, 0x0001 */
85
86 n = p - pkt; /* Total packet length */
87 debug("Packet size %d\n", n);
88
89 DnsOurPort = random_port();
90
91 NetSendUDPPacket(NetServerEther, NetOurDNSIP, DNS_SERVICE_PORT,
92 DnsOurPort, n);
93 debug("DNS packet sent\n");
94}
95
96static void
97DnsTimeout(void)
98{
99 puts("Timeout\n");
100 NetState = NETLOOP_FAIL;
101}
102
103static void
104DnsHandler(uchar *pkt, unsigned dest, 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 IPStr[22];
111 IPaddr_t IPAddress;
112 short tmp;
113
114
115 debug("%s\n", __func__);
116 if (dest != DnsOurPort)
117 return;
118
119 for (i = 0; i < len; i += 4)
120 debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x\n",
121 pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);
122
123 /* We sent 1 query. We want to see more that 1 answer. */
124 header = (struct header *) pkt;
125 if (ntohs(header->nqueries) != 1)
126 return;
127
128 /* Received 0 answers */
129 if (header->nanswers == 0) {
130 puts("DNS server returned no answers\n");
131 NetState = NETLOOP_SUCCESS;
132 return;
133 }
134
135 /* Skip host name */
136 s = &header->data[0];
137 e = pkt + len;
138 for (p = s; p < e && *p != '\0'; p++)
139 continue;
140
141 /* We sent query class 1, query type 1 */
142 tmp = p[1] | (p[2] << 8);
143 if (&p[5] > e || ntohs(tmp) != DNS_A_RECORD) {
144 puts("DNS response was not A record\n");
145 NetState = NETLOOP_SUCCESS;
146 return;
147 }
148
149 /* Go to the first answer section */
150 p += 5;
151
152 /* Loop through the answers, we want A type answer */
153 for (found = stop = 0; !stop && &p[12] < e; ) {
154
155 /* Skip possible name in CNAME answer */
156 if (*p != 0xc0) {
157 while (*p && &p[12] < e)
158 p++;
159 p--;
160 }
161 debug("Name (Offset in header): %d\n", p[1]);
162
163 tmp = p[2] | (p[3] << 8);
164 type = ntohs(tmp);
165 debug("type = %d\n", type);
166 if (type == DNS_CNAME_RECORD) {
167 /* CNAME answer. shift to the next section */
168 debug("Found canonical name\n");
169 tmp = p[10] | (p[11] << 8);
170 dlen = ntohs(tmp);
171 debug("dlen = %d\n", dlen);
172 p += 12 + dlen;
173 } else if (type == DNS_A_RECORD) {
174 debug("Found A-record\n");
175 found = stop = 1;
176 } else {
177 debug("Unknown type\n");
178 stop = 1;
179 }
180 }
181
182 if (found && &p[12] < e) {
183
184 tmp = p[10] | (p[11] << 8);
185 dlen = ntohs(tmp);
186 p += 12;
187 memcpy(&IPAddress, p, 4);
188
189 if (p + dlen <= e) {
190 ip_to_string(IPAddress, IPStr);
191 printf("%s\n", IPStr);
192 if (NetDNSenvvar)
193 setenv(NetDNSenvvar, IPStr);
194 } else
195 puts("server responded with invalid IP number\n");
196 }
197
198 NetState = NETLOOP_SUCCESS;
199}
200
201void
202DnsStart(void)
203{
204 debug("%s\n", __func__);
205
206 NetSetTimeout(DNS_TIMEOUT, DnsTimeout);
207 NetSetHandler(DnsHandler);
208
209 DnsSend();
210}