diff options
Diffstat (limited to 'net/dns.c')
| -rw-r--r-- | net/dns.c | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/net/dns.c b/net/dns.c new file mode 100644 index 0000000..bb3e3f5 --- /dev/null +++ b/net/dns.c @@ -0,0 +1,210 @@ +/* + * 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 NetServerIP. 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 "dns.h" + +char *NetDNSResolve; /* The host to resolve */ +char *NetDNSenvvar; /* The envvar to store the answer in */ + +static int DnsOurPort; + +static void +DnsSend(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 = NetDNSResolve; + pkt = p = (uchar *)(NetTxPacket + NetEthHdrSize() + IP_HDR_SIZE); + + /* 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", n); + + DnsOurPort = random_port(); + + NetSendUDPPacket(NetServerEther, NetOurDNSIP, DNS_SERVICE_PORT, + DnsOurPort, n); + debug("DNS packet sent\n"); +} + +static void +DnsTimeout(void) +{ + puts("Timeout\n"); + NetState = NETLOOP_FAIL; +} + +static void +DnsHandler(uchar *pkt, unsigned dest, unsigned src, unsigned len) +{ + struct header *header; + const unsigned char *p, *e, *s; + u16 type, i; + int found, stop, dlen; + char IPStr[22]; + IPaddr_t IPAddress; + short tmp; + + + debug("%s\n", __func__); + if (dest != DnsOurPort) + return; + + for (i = 0; i < len; i += 4) + debug("0x%p - 0x%.2x 0x%.2x 0x%.2x 0x%.2x\n", + pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]); + + /* We sent 1 query. We want to see more that 1 answer. */ + header = (struct header *) pkt; + if (ntohs(header->nqueries) != 1) + return; + + /* Received 0 answers */ + if (header->nanswers == 0) { + puts("DNS server returned no answers\n"); + NetState = 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 */ + tmp = p[1] | (p[2] << 8); + if (&p[5] > e || ntohs(tmp) != DNS_A_RECORD) { + puts("DNS response was not A record\n"); + NetState = 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\n", p[1]); + + tmp = p[2] | (p[3] << 8); + type = ntohs(tmp); + debug("type = %d\n", type); + if (type == DNS_CNAME_RECORD) { + /* CNAME answer. shift to the next section */ + debug("Found canonical name\n"); + tmp = p[10] | (p[11] << 8); + dlen = ntohs(tmp); + debug("dlen = %d\n", dlen); + p += 12 + dlen; + } else if (type == DNS_A_RECORD) { + debug("Found A-record\n"); + found = stop = 1; + } else { + debug("Unknown type\n"); + stop = 1; + } + } + + if (found && &p[12] < e) { + + tmp = p[10] | (p[11] << 8); + dlen = ntohs(tmp); + p += 12; + memcpy(&IPAddress, p, 4); + + if (p + dlen <= e) { + ip_to_string(IPAddress, IPStr); + printf("%s\n", IPStr); + if (NetDNSenvvar) + setenv(NetDNSenvvar, IPStr); + } else + puts("server responded with invalid IP number\n"); + } + + NetState = NETLOOP_SUCCESS; +} + +void +DnsStart(void) +{ + debug("%s\n", __func__); + + NetSetTimeout(DNS_TIMEOUT, DnsTimeout); + NetSetHandler(DnsHandler); + + DnsSend(); +} |