8bbc1064c7
The separation of incoming packets handling makes it much easier to run barebox dns client on top of picotcp network stack in the future. Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
276 lines
5.8 KiB
C
276 lines
5.8 KiB
C
/*
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* DNS support driver
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*
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* Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
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* Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org>
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*
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* This is a simple DNS implementation for U-Boot. It will use the first IP
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* in the DNS response as NetServerIP. This can then be used for any other
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* network related activities.
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*
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* The packet handling is partly based on TADNS, original copyrights
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* follow below.
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*
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*/
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/*
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* Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com>
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*
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* "THE BEER-WARE LICENSE" (Revision 42):
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* Sergey Lyubka wrote this file. As long as you retain this notice you
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* can do whatever you want with this stuff. If we meet some day, and you think
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* this stuff is worth it, you can buy me a beer in return.
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*/
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//#define DEBUG
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#include <common.h>
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#include <command.h>
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#include <net.h>
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#include <clock.h>
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#include <environment.h>
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#include <linux/err.h>
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#define DNS_PORT 53
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/* http://en.wikipedia.org/wiki/List_of_DNS_record_types */
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enum dns_query_type {
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DNS_A_RECORD = 0x01,
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DNS_CNAME_RECORD = 0x05,
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DNS_MX_RECORD = 0x0f,
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};
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/*
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* DNS network packet
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*/
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struct header {
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uint16_t tid; /* Transaction ID */
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uint16_t flags; /* Flags */
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uint16_t nqueries; /* Questions */
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uint16_t nanswers; /* Answers */
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uint16_t nauth; /* Authority PRs */
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uint16_t nother; /* Other PRs */
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unsigned char data[1]; /* Data, variable length */
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};
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#define STATE_INIT 0
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#define STATE_DONE 1
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static struct net_connection *dns_con;
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static uint64_t dns_timer_start;
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static int dns_state;
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static IPaddr_t dns_ip;
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static int dns_send(char *name)
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{
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int ret;
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struct header *header;
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enum dns_query_type qtype = DNS_A_RECORD;
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unsigned char *packet = net_udp_get_payload(dns_con);
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unsigned char *p, *s, *fullname, *dotptr;
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const unsigned char *domain;
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/* Prepare DNS packet header */
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header = (struct header *)packet;
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header->tid = 1;
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header->flags = htons(0x100); /* standard query */
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header->nqueries = htons(1); /* Just one query */
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header->nanswers = 0;
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header->nauth = 0;
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header->nother = 0;
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domain = getenv("net.domainname");
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if (!strchr(name, '.') && domain && *domain)
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fullname = asprintf(".%s.%s.", name, domain);
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else
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fullname = asprintf(".%s.", name);
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/* replace dots in fullname with chunk len */
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dotptr = fullname;
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do {
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int len;
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s = strchr(dotptr + 1, '.');
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len = s - dotptr - 1;
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*dotptr = len;
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dotptr = s;
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} while (*(dotptr + 1));
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*dotptr = 0;
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strcpy(header->data, fullname);
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p = header->data + strlen(fullname);
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*p++ = 0; /* Mark end of host name */
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*p++ = 0; /* Some servers require double null */
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*p++ = (unsigned char)qtype; /* Query Type */
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*p++ = 0;
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*p++ = 1; /* Class: inet, 0x0001 */
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ret = net_udp_send(dns_con, p - packet);
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free(fullname);
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return ret;
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}
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static void dns_recv(struct header *header, unsigned len)
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{
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unsigned char *p, *e, *s;
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u16 type;
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int found, stop, dlen;
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short tmp;
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debug("%s\n", __func__);
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/* We sent 1 query. We want to see more that 1 answer. */
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if (ntohs(header->nqueries) != 1)
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return;
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/* Received 0 answers */
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if (header->nanswers == 0) {
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dns_state = STATE_DONE;
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debug("DNS server returned no answers\n");
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return;
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}
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/* Skip host name */
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s = &header->data[0];
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e = ((uint8_t *)header) + len;
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for (p = s; p < e && *p != '\0'; p++)
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continue;
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/* We sent query class 1, query type 1 */
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tmp = p[1] | (p[2] << 8);
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if (&p[5] > e || ntohs(tmp) != DNS_A_RECORD) {
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debug("DNS response was not A record\n");
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return;
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}
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/* Go to the first answer section */
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p += 5;
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/* Loop through the answers, we want A type answer */
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for (found = stop = 0; !stop && &p[12] < e; ) {
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/* Skip possible name in CNAME answer */
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if (*p != 0xc0) {
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while (*p && &p[12] < e)
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p++;
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p--;
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}
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debug("Name (Offset in header): %d\n", p[1]);
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tmp = p[2] | (p[3] << 8);
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type = ntohs(tmp);
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debug("type = %d\n", type);
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if (type == DNS_CNAME_RECORD) {
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/* CNAME answer. shift to the next section */
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debug("Found canonical name\n");
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tmp = p[10] | (p[11] << 8);
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dlen = ntohs(tmp);
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debug("dlen = %d\n", dlen);
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p += 12 + dlen;
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} else if (type == DNS_A_RECORD) {
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debug("Found A-record\n");
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found = stop = 1;
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} else {
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debug("Unknown type\n");
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stop = 1;
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}
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}
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if (found && &p[12] < e) {
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tmp = p[10] | (p[11] << 8);
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dlen = ntohs(tmp);
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p += 12;
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dns_ip = net_read_ip(p);
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dns_state = STATE_DONE;
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}
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}
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static void dns_handler(void *ctx, char *packet, unsigned len)
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{
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(void)ctx;
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dns_recv((struct header *)net_eth_to_udp_payload(packet),
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net_eth_to_udplen(packet));
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}
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IPaddr_t resolv(char *host)
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{
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IPaddr_t ip;
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const char *ns;
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if (!string_to_ip(host, &ip))
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return ip;
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dns_ip = 0;
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dns_state = STATE_INIT;
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ns = getenv("net.nameserver");
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if (!ns || !*ns) {
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printk("%s: no nameserver specified in $net.nameserver\n",
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__func__);
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return 0;
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}
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if (string_to_ip(ns, &ip))
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return 0;
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debug("resolving host %s via nameserver %s\n", host, ip_to_string(ip));
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dns_con = net_udp_new(ip, DNS_PORT, dns_handler, NULL);
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if (IS_ERR(dns_con))
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return PTR_ERR(dns_con);
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dns_timer_start = get_time_ns();
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dns_send(host);
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while (dns_state != STATE_DONE) {
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if (ctrlc()) {
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break;
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}
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net_poll();
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if (is_timeout(dns_timer_start, SECOND)) {
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dns_timer_start = get_time_ns();
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printf("T ");
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dns_send(host);
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}
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}
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net_unregister(dns_con);
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return dns_ip;
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}
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#ifdef CONFIG_CMD_HOST
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static int do_host(int argc, char *argv[])
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{
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IPaddr_t ip;
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if (argc != 2)
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return COMMAND_ERROR_USAGE;
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ip = resolv(argv[1]);
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if (!ip)
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printf("unknown host %s\n", argv[1]);
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else {
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printf("%s is at ", argv[1]);
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print_IPaddr(ip);
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printf("\n");
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}
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return 0;
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}
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BAREBOX_CMD_START(host)
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.cmd = do_host,
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BAREBOX_CMD_DESC("resolve a hostname")
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BAREBOX_CMD_OPTS("HOSTNAME")
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BAREBOX_CMD_GROUP(CMD_GRP_NET)
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BAREBOX_CMD_END
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#endif
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