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 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 }