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 env_set(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 } 208