/*
 * 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 <env.h>
#include <log.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;

/*
 * make port a little random (1024-17407)
 * This keeps the math somewhat trivial to compute, and seems to work with
 * all supported protocols/clients/servers
 */
static unsigned int random_port(void)
{
        return 1024 + (get_timer(0) % 0x4000);
}

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", 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\n");
}

static void dns_timeout_handler(void)
{
        puts("Timeout\n");
        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\n", __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\n",
                      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\n");
                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\n");
                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\n", p[1]);

                type = get_unaligned_be16(p+2);
                debug("type = %d\n", type);
                if (type == DNS_CNAME_RECORD) {
                        /* CNAME answer. shift to the next section */
                        debug("Found canonical name\n");
                        dlen = get_unaligned_be16(p+10);
                        debug("dlen = %d\n", dlen);
                        p += 12 + dlen;
                } else if (type == DNS_A_RECORD) {
                        debug("Found A-record\n");
                        found = 1;
                        stop = 1;
                } else {
                        debug("Unknown type\n");
                        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\n", ip_str);
                        if (net_dns_env_var)
                                env_set(net_dns_env_var, ip_str);
                } else {
                        puts("server responded with invalid IP number\n");
                }
        }

        net_set_state(NETLOOP_SUCCESS);
}

void dns_start(void)
{
        debug("%s\n", __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();
}