/home/jander/temp/etherdune/DNS.cpp

Go to the documentation of this file.

// EtherDune DNS Service
// Author: Javier Peletier <jm@friendev.com>
// Summary: Implements the basics of DNS so as to resolve hostnames to IP addresses
//
// Copyright (c) 2015 All Rights Reserved, http://friendev.com
//
// This source is subject to the GPLv2 license.
// Please see the License.txt file for more information.
// All other rights reserved.
//
// THIS CODE AND INFORMATION ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY 
// KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.

#include "DNS.h"
#include "Checksum.h"

#define AC_LOGLEVEL 3
#include <ACLog.h>
ACROSS_MODULE("DNS");

void DNSClient::onReceive(uint16_t len)
{
    //Cheap hack: usually the last 4 bytes of the DNS response are the IP address we're looking for.

    IPAddress& resolvedIP = *((IPAddress*)(packet.udpData + len - sizeof(IPAddress)));

    NetworkService::notifyOnDNSResolve(packet.dns.rcode, packet.dns.identification, resolvedIP);
    buffer.release();
    if (!buffer.isEmpty())
        send();
}

DNSClient::DNSClient() 
{
    remotePort = 53;
}

uint16_t DNSClient::resolve(const char* name)
{
    remoteIP = dnsIP;

    timer = DNS_TIMEOUT_QUERY;

    DNSHeader& header = *(DNSHeader*)packet.raw;

    uint8_t* queryPtr = packet.raw + sizeof(DNSHeader);
    uint8_t* b = queryPtr;
    uint8_t* label = b;
    b++;

    for (*label = 0; *name != 0; name++, b++)
    {
        if (*name == '.')
        {
            label = b;

            *label = 0;
        }
        else
        {
            *b = *name;
            (*label)++;
        }
    }

    *b = 0;

    uint16_t id = Checksum::calc(b - queryPtr, queryPtr);

    header.zero();
    header.identification = id;
    /*
    header.QR = 0; // query
    header.opcode = 0; // standard query;
    */
    header.RD = 1; //recursion desired
    header.numberOfQuestions=1; //only one question

    //queryType = 1 (A query), queryClass=1 (Internet Address);
    b++;
    *((uint32_t*)b) = 0x01000100; //queryType = 1 (A query), queryClass=1 (Internet Address);


    b += 4;

    write(sizeof(header) + b - queryPtr, packet.raw);

    send();
    return id;
}


void DNSClient::tick()
{
    if (timer > 0)
    {
        timer--;

        if (timer == 0)
        {
            buffer.release();
            timer = DNS_TIMEOUT_QUERY;
        }
    }


    UDPSocket::tick();
}

bool DNSClient::sendPacket()
{
    uint16_t dataChecksum = 0;
    uint16_t dataLength;

    dataLength = buffer.fillTxBuffer(sizeof(EthernetHeader) + sizeof(IPHeader) + sizeof(UDPHeader),/*out*/ dataChecksum, 1);

    bool ret;
    if (dataLength > 0)
    {
        prepareUDPPacket(dataLength, dataChecksum);
        ret = !sendIPPacket(sizeof(IPHeader) + sizeof(UDPHeader));
    }
    else
        ret = false;
    
    return ret;

}