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 DnsSend(); 206 } 207