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 *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 = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE); 49 p = pkt; 50 51 /* Prepare DNS packet header */ 52 header = (struct header *) pkt; 53 header->tid = 1; 54 header->flags = htons(0x100); /* standard query */ 55 header->nqueries = htons(1); /* Just one query */ 56 header->nanswers = 0; 57 header->nauth = 0; 58 header->nother = 0; 59 60 /* Encode DNS name */ 61 name_len = strlen(name); 62 p = (uchar *) &header->data; /* For encoding host name into packet */ 63 64 do { 65 s = strchr(name, '.'); 66 if (!s) 67 s = name + name_len; 68 69 n = s - name; /* Chunk length */ 70 *p++ = n; /* Copy length */ 71 memcpy(p, name, n); /* Copy chunk */ 72 p += n; 73 74 if (*s == '.') 75 n++; 76 77 name += n; 78 name_len -= n; 79 } while (*s != '\0'); 80 81 *p++ = 0; /* Mark end of host name */ 82 *p++ = 0; /* Some servers require double null */ 83 *p++ = (unsigned char) qtype; /* Query Type */ 84 85 *p++ = 0; 86 *p++ = 1; /* Class: inet, 0x0001 */ 87 88 n = p - pkt; /* Total packet length */ 89 debug("Packet size %d\n", n); 90 91 DnsOurPort = random_port(); 92 93 net_send_udp_packet(net_server_ethaddr, net_dns_server, 94 DNS_SERVICE_PORT, DnsOurPort, n); 95 debug("DNS packet sent\n"); 96 } 97 98 static void 99 DnsTimeout(void) 100 { 101 puts("Timeout\n"); 102 net_set_state(NETLOOP_FAIL); 103 } 104 105 static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip, 106 unsigned src, unsigned len) 107 { 108 struct header *header; 109 const unsigned char *p, *e, *s; 110 u16 type, i; 111 int found, stop, dlen; 112 char IPStr[22]; 113 struct in_addr ip_addr; 114 115 116 debug("%s\n", __func__); 117 if (dest != DnsOurPort) 118 return; 119 120 for (i = 0; i < len; i += 4) 121 debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x\n", 122 pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]); 123 124 /* We sent one query. We want to have a single answer: */ 125 header = (struct header *) pkt; 126 if (ntohs(header->nqueries) != 1) 127 return; 128 129 /* Received 0 answers */ 130 if (header->nanswers == 0) { 131 puts("DNS: host not found\n"); 132 net_set_state(NETLOOP_SUCCESS); 133 return; 134 } 135 136 /* Skip host name */ 137 s = &header->data[0]; 138 e = pkt + len; 139 for (p = s; p < e && *p != '\0'; p++) 140 continue; 141 142 /* We sent query class 1, query type 1 */ 143 if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) { 144 puts("DNS: response was not an A record\n"); 145 net_set_state(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 type = get_unaligned_be16(p+2); 164 debug("type = %d\n", type); 165 if (type == DNS_CNAME_RECORD) { 166 /* CNAME answer. shift to the next section */ 167 debug("Found canonical name\n"); 168 dlen = get_unaligned_be16(p+10); 169 debug("dlen = %d\n", dlen); 170 p += 12 + dlen; 171 } else if (type == DNS_A_RECORD) { 172 debug("Found A-record\n"); 173 found = stop = 1; 174 } else { 175 debug("Unknown type\n"); 176 stop = 1; 177 } 178 } 179 180 if (found && &p[12] < e) { 181 182 dlen = get_unaligned_be16(p+10); 183 p += 12; 184 memcpy(&ip_addr, p, 4); 185 186 if (p + dlen <= e) { 187 ip_to_string(ip_addr, IPStr); 188 printf("%s\n", IPStr); 189 if (NetDNSenvvar) 190 setenv(NetDNSenvvar, IPStr); 191 } else 192 puts("server responded with invalid IP number\n"); 193 } 194 195 net_set_state(NETLOOP_SUCCESS); 196 } 197 198 void 199 DnsStart(void) 200 { 201 debug("%s\n", __func__); 202 203 NetSetTimeout(DNS_TIMEOUT, DnsTimeout); 204 net_set_udp_handler(dns_handler); 205 206 /* Clear a previous MAC address, the server IP might have changed. */ 207 memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr)); 208 209 DnsSend(); 210 } 211