net/dns.c

   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 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 #include <asm/unaligned.h>
  29
  30 #include "dns.h"
  31
  32 char *NetDNSResolve;    /* The host to resolve  */
  33 char *NetDNSenvvar;     /* The envvar to store the answer in */
  34
  35 static int DnsOurPort;
  36
  37 static void
  38 DnsSend(void)
  39 {
  40         struct header *header;
  41         int n, name_len;
  42         uchar *p, *pkt;
  43         const char *s;
  44         const char *name;
  45         enum dns_query_type qtype = DNS_A_RECORD;
  46
  47         name = NetDNSResolve;
  48         pkt = p = (uchar *)(NetTxPacket + NetEthHdrSize() + IP_UDP_HDR_SIZE);
  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         DnsOurPort = random_port();
  91
  92         NetSendUDPPacket(NetServerEther, NetOurDNSIP, DNS_SERVICE_PORT,
  93                 DnsOurPort, n);
  94         debug("DNS packet sent\n");
  95 }
  96
  97 static void
  98 DnsTimeout(void)
  99 {
 100         puts("Timeout\n");
 101         net_set_state(NETLOOP_FAIL);
 102 }
 103
 104 static void
 105 DnsHandler(uchar *pkt, unsigned dest, IPaddr_t sip, unsigned src, unsigned len)
 106 {
 107         struct header *header;
 108         const unsigned char *p, *e, *s;
 109         u16 type, i;
 110         int found, stop, dlen;
 111         char IPStr[22];
 112         IPaddr_t IPAddress;
 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 one query. We want to have a single 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: host not found\n");
 131                 net_set_state(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         if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) {
 143                 puts("DNS: response was not an A record\n");
 144                 net_set_state(NETLOOP_SUCCESS);
 145                 return;
 146         }
 147
 148         /* Go to the first answer section */
 149         p += 5;
 150
 151         /* Loop through the answers, we want A type answer */
 152         for (found = stop = 0; !stop && &p[12] < e; ) {
 153
 154                 /* Skip possible name in CNAME answer */
 155                 if (*p != 0xc0) {
 156                         while (*p && &p[12] < e)
 157                                 p++;
 158                         p--;
 159                 }
 160                 debug("Name (Offset in header): %d\n", p[1]);
 161
 162                 type = get_unaligned_be16(p+2);
 163                 debug("type = %d\n", type);
 164                 if (type == DNS_CNAME_RECORD) {
 165                         /* CNAME answer. shift to the next section */
 166                         debug("Found canonical name\n");
 167                         dlen = get_unaligned_be16(p+10);
 168                         debug("dlen = %d\n", dlen);
 169                         p += 12 + dlen;
 170                 } else if (type == DNS_A_RECORD) {
 171                         debug("Found A-record\n");
 172                         found = stop = 1;
 173                 } else {
 174                         debug("Unknown type\n");
 175                         stop = 1;
 176                 }
 177         }
 178
 179         if (found && &p[12] < e) {
 180
 181                 dlen = get_unaligned_be16(p+10);
 182                 p += 12;
 183                 memcpy(&IPAddress, p, 4);
 184
 185                 if (p + dlen <= e) {
 186                         ip_to_string(IPAddress, IPStr);
 187                         printf("%s\n", IPStr);
 188                         if (NetDNSenvvar)
 189                                 setenv(NetDNSenvvar, IPStr);
 190                 } else
 191                         puts("server responded with invalid IP number\n");
 192         }
 193
 194         net_set_state(NETLOOP_SUCCESS);
 195 }
 196
 197 void
 198 DnsStart(void)
 199 {
 200         debug("%s\n", __func__);
 201
 202         NetSetTimeout(DNS_TIMEOUT, DnsTimeout);
 203         net_set_udp_handler(DnsHandler);
 204
 205         /* Clear a previous MAC address, the server IP might have changed. */
 206         memset(NetServerEther, 0, sizeof(NetServerEther));
 207
 208         DnsSend();
 209 }