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 29 #include "dns.h" 30 31 char *NetDNSResolve; /* The host to resolve */ 32 char *NetDNSenvvar; /* The envvar to store the answer in */ 33 34 static int DnsOurPort; 35 36 static void 37 DnsSend(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 96 static void 97 DnsTimeout(void) 98 { 99 puts("Timeout\n"); 100 NetState = NETLOOP_FAIL; 101 } 102 103 static void 104 DnsHandler(uchar *pkt, unsigned dest, IPaddr_t sip, 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 } 200 201 void 202 DnsStart(void) 203 { 204 debug("%s\n", __func__); 205 206 NetSetTimeout(DNS_TIMEOUT, DnsTimeout); 207 NetSetHandler(DnsHandler); 208 209 DnsSend(); 210 } 211