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net/dns.c
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d41ce506b Initial Release, ... |
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/* * DNS support driver * * Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl> * Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org> * * This is a simple DNS implementation for U-Boot. It will use the first IP * in the DNS response as net_server_ip. This can then be used for any other * network related activities. * * The packet handling is partly based on TADNS, original copyrights * follow below. * */ /* * Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com> * * "THE BEER-WARE LICENSE" (Revision 42): * Sergey Lyubka wrote this file. As long as you retain this notice you * can do whatever you want with this stuff. If we meet some day, and you think * this stuff is worth it, you can buy me a beer in return. */ #include <common.h> #include <command.h> #include <net.h> #include <asm/unaligned.h> #include "dns.h" char *net_dns_resolve; /* The host to resolve */ char *net_dns_env_var; /* The envvar to store the answer in */ static int dns_our_port; static void dns_send(void) { struct header *header; int n, name_len; uchar *p, *pkt; const char *s; const char *name; enum dns_query_type qtype = DNS_A_RECORD; name = net_dns_resolve; pkt = (uchar *)(net_tx_packet + net_eth_hdr_size() + IP_UDP_HDR_SIZE); p = pkt; /* Prepare DNS packet header */ header = (struct header *)pkt; header->tid = 1; header->flags = htons(0x100); /* standard query */ header->nqueries = htons(1); /* Just one query */ header->nanswers = 0; header->nauth = 0; header->nother = 0; /* Encode DNS name */ name_len = strlen(name); p = (uchar *)&header->data; /* For encoding host name into packet */ do { s = strchr(name, '.'); if (!s) s = name + name_len; n = s - name; /* Chunk length */ *p++ = n; /* Copy length */ memcpy(p, name, n); /* Copy chunk */ p += n; if (*s == '.') n++; name += n; name_len -= n; } while (*s != '\0'); *p++ = 0; /* Mark end of host name */ *p++ = 0; /* Some servers require double null */ *p++ = (unsigned char) qtype; /* Query Type */ *p++ = 0; *p++ = 1; /* Class: inet, 0x0001 */ n = p - pkt; /* Total packet length */ debug("Packet size %d ", n); dns_our_port = random_port(); net_send_udp_packet(net_server_ethaddr, net_dns_server, DNS_SERVICE_PORT, dns_our_port, n); debug("DNS packet sent "); } static void dns_timeout_handler(void) { puts("Timeout "); net_set_state(NETLOOP_FAIL); } static void dns_handler(uchar *pkt, unsigned dest, struct in_addr sip, unsigned src, unsigned len) { struct header *header; const unsigned char *p, *e, *s; u16 type, i; int found, stop, dlen; char ip_str[22]; struct in_addr ip_addr; debug("%s ", __func__); if (dest != dns_our_port) return; for (i = 0; i < len; i += 4) debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x ", pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]); /* We sent one query. We want to have a single answer: */ header = (struct header *)pkt; if (ntohs(header->nqueries) != 1) return; /* Received 0 answers */ if (header->nanswers == 0) { puts("DNS: host not found "); net_set_state(NETLOOP_SUCCESS); return; } /* Skip host name */ s = &header->data[0]; e = pkt + len; for (p = s; p < e && *p != '\0'; p++) continue; /* We sent query class 1, query type 1 */ if (&p[5] > e || get_unaligned_be16(p+1) != DNS_A_RECORD) { puts("DNS: response was not an A record "); net_set_state(NETLOOP_SUCCESS); return; } /* Go to the first answer section */ p += 5; /* Loop through the answers, we want A type answer */ for (found = stop = 0; !stop && &p[12] < e; ) { /* Skip possible name in CNAME answer */ if (*p != 0xc0) { while (*p && &p[12] < e) p++; p--; } debug("Name (Offset in header): %d ", p[1]); type = get_unaligned_be16(p+2); debug("type = %d ", type); if (type == DNS_CNAME_RECORD) { /* CNAME answer. shift to the next section */ debug("Found canonical name "); dlen = get_unaligned_be16(p+10); debug("dlen = %d ", dlen); p += 12 + dlen; } else if (type == DNS_A_RECORD) { debug("Found A-record "); found = 1; stop = 1; } else { debug("Unknown type "); stop = 1; } } if (found && &p[12] < e) { dlen = get_unaligned_be16(p+10); p += 12; memcpy(&ip_addr, p, 4); if (p + dlen <= e) { ip_to_string(ip_addr, ip_str); printf("%s ", ip_str); if (net_dns_env_var) env_set(net_dns_env_var, ip_str); } else { puts("server responded with invalid IP number "); } } net_set_state(NETLOOP_SUCCESS); } void dns_start(void) { debug("%s ", __func__); net_set_timeout_handler(DNS_TIMEOUT, dns_timeout_handler); net_set_udp_handler(dns_handler); /* Clear a previous MAC address, the server IP might have changed. */ memset(net_server_ethaddr, 0, sizeof(net_server_ethaddr)); dns_send(); } |