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 <env.h> 28#include <log.h> 29#include <net.h> 30#include <asm/unaligned.h> 31 32#include "dns.h" 33 34char *net_dns_resolve; /* The host to resolve */ 35char *net_dns_env_var; /* The envvar to store the answer in */ 36 37static int dns_our_port; 38 39/* 40 * make port a little random (1024-17407) 41 * This keeps the math somewhat trivial to compute, and seems to work with 42 * all supported protocols/clients/servers 43 */ 44static unsigned int random_port(void) 45{ 46 return 1024 + (get_timer(0) % 0x4000); 47} 48 49static void dns_send(void) 50{ 51 struct header *header; 52 int n, name_len; 53 uchar *p, *pkt; 54 const char *s; 55 const char *name; 56 enum dns_query_type qtype = DNS_A_RECORD; 57 58 name = net_dns_resolve; 59 pkt = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE); 60 p = pkt; 61 62 /* Prepare DNS packet header */ 63 header = (struct header *)pkt; 64 header->tid = 1; 65 header->flags = htons(0x100); /* standard query */ 66 header->nqueries = htons(1); /* Just one query */ 67 header->nanswers = 0; 68 header->nauth = 0; 69 header->nother = 0; 70 71 /* Encode DNS name */ 72 name_len = strlen(name); 73 p = (uchar *)&header->data; /* For encoding host name into packet */ 74 75 do { 76 s = strchr(name, '.'); 77 if (!s) 78 s = name + name_len; 79 80 n = s - name; /* Chunk length */ 81 *p++ = n; /* Copy length */ 82 memcpy(p, name, n); /* Copy chunk */ 83 p += n; 84 85 if (*s == '.') 86 n++; 87 88 name += n; 89 name_len -= n; 90 } while (*s != '\0'); 91 92 *p++ = 0; /* Mark end of host name */ 93 *p++ = 0; /* Some servers require double null */ 94 *p++ = (unsigned char) qtype; /* Query Type */ 95 96 *p++ = 0; 97 *p++ = 1; /* Class: inet, 0x0001 */ 98 99 n = p - pkt; /* Total packet length */ 100 debug("Packet size %d\n", n); 101 102 dns_our_port = random_port(); 103 104 net_send_udp_packet(net_server_ethaddr, net_dns_server, 105 DNS_SERVICE_PORT, dns_our_port, n); 106 debug("DNS packet sent\n"); 107} 108 109static void dns_timeout_handler(void) 110{ 111 puts("Timeout\n"); 112 net_set_state(NETLOOP_FAIL); 113} 114 115static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip, 116 unsigned src, unsigned len) 117{ 118 struct header *header; 119 const unsigned char *p, *e, *s; 120 u16 type, i; 121 int found, stop, dlen; 122 char ip_str[22]; 123 struct in_addr ip_addr; 124 125 126 debug("%s\n", __func__); 127 if (dest != dns_our_port) 128 return; 129 130 for (i = 0; i < len; i += 4) 131 debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x\n", 132 pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]); 133 134 /* We sent one query. We want to have a single answer: */ 135 header = (struct header *)pkt; 136 if (ntohs(header->nqueries) != 1) 137 return; 138 139 /* Received 0 answers */ 140 if (header->nanswers == 0) { 141 puts("DNS: host not found\n"); 142 net_set_state(NETLOOP_SUCCESS); 143 return; 144 } 145 146 /* Skip host name */ 147 s = &header->data[0]; 148 e = pkt + len; 149 for (p = s; p < e && *p != '\0'; p++) 150 continue; 151 152 /* We sent query class 1, query type 1 */ 153 if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) { 154 puts("DNS: response was not an A record\n"); 155 net_set_state(NETLOOP_SUCCESS); 156 return; 157 } 158 159 /* Go to the first answer section */ 160 p += 5; 161 162 /* Loop through the answers, we want A type answer */ 163 for (found = stop = 0; !stop && &p[12] < e; ) { 164 /* Skip possible name in CNAME answer */ 165 if (*p != 0xc0) { 166 while (*p && &p[12] < e) 167 p++; 168 p--; 169 } 170 debug("Name (Offset in header): %d\n", p[1]); 171 172 type = get_unaligned_be16(p+2); 173 debug("type = %d\n", type); 174 if (type == DNS_CNAME_RECORD) { 175 /* CNAME answer. shift to the next section */ 176 debug("Found canonical name\n"); 177 dlen = get_unaligned_be16(p+10); 178 debug("dlen = %d\n", dlen); 179 p += 12 + dlen; 180 } else if (type == DNS_A_RECORD) { 181 debug("Found A-record\n"); 182 found = 1; 183 stop = 1; 184 } else { 185 debug("Unknown type\n"); 186 stop = 1; 187 } 188 } 189 190 if (found && &p[12] < e) { 191 dlen = get_unaligned_be16(p+10); 192 p += 12; 193 memcpy(&ip_addr, p, 4); 194 195 if (p + dlen <= e) { 196 ip_to_string(ip_addr, ip_str); 197 printf("%s\n", ip_str); 198 if (net_dns_env_var) 199 env_set(net_dns_env_var, ip_str); 200 } else { 201 puts("server responded with invalid IP number\n"); 202 } 203 } 204 205 net_set_state(NETLOOP_SUCCESS); 206} 207 208void dns_start(void) 209{ 210 debug("%s\n", __func__); 211 212 net_set_timeout_handler(DNS_TIMEOUT, dns_timeout_handler); 213 net_set_udp_handler(dns_handler); 214 215 /* Clear a previous MAC address, the server IP might have changed. */ 216 memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr)); 217 218 dns_send(); 219} 220