NOTE

File content as of revision 0:2a179bd4cc02:

/* Copyright (c) 2013 Henry Leinen (henry[dot]leinen [at] online [dot] de)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include "mbed.h"
#include "DnsQuery.h"

#define DEBUG
#include "debug.h"



DnsQuery::DnsQuery(Wifi* wifi, IPADDRESS_t *dnsip)
    : _wifi(wifi)
{
    _dnsip.sin_addr.o1 = dnsip->sin_addr.o1;
    _dnsip.sin_addr.o2 = dnsip->sin_addr.o2;
    _dnsip.sin_addr.o3 = dnsip->sin_addr.o3;
    _dnsip.sin_addr.o4 = dnsip->sin_addr.o4;
    INFO("Setting   DNS = %d.%d.%d.%d !", dnsip->sin_addr.o1, dnsip->sin_addr.o2, dnsip->sin_addr.o3, dnsip->sin_addr.o4);
    INFO("Accepting DNS = %d.%d.%d.%d !", _dnsip.sin_addr.o1, _dnsip.sin_addr.o2, _dnsip.sin_addr.o3, _dnsip.sin_addr.o4);
}

bool DnsQuery::gethostbyname(const char* hostname, IPADDRESS_t &ipaddress)
{
    int len = 0;
    if (hostname == NULL)
        return false;
    len = strlen(hostname);
    if ((len >128) || (len == 0))
        return false;
    memset (&ipaddress, 0, sizeof(ipaddress));
    
    int packetlen = /* size of HEADER structure */ 12 + /* size of QUESTION Structure */5 + len + 1;
    char *packet = new char[packetlen]; /* this is the UDP packet to send to the DNS */
    if (packet == NULL)
        return false;
    
    //  Fill the header
    memset(packet, 0, packetlen);
    packet[1] = 1;      //  ID = 1
    packet[5] = 1;      // QDCOUNT = 1 (contains one question)

    int c = 13;         //  point to NAME element in question section or request
    int cnt = 12;       //  points to the counter of
    packet[cnt] = 0;
    for (int i = 0 ; i < len ; i++) {
        if (hostname[i] != '.') {
            //  Copy the character and increment the character counter
            packet[cnt]++;
            packet[c++] = hostname[i];
        } else {
            //  Finished with this part, so go to the next
            cnt = c++;
            packet[cnt] = 0;
        }
    }
    
    //  Terminate this domain name with a zero entry
    packet[c++] = 0;
    
    //  Set QTYPE
    packet[c++] = 0;
    packet[c++] = 1;
    //  Set QCLASS
    packet[c++] = 0;
    packet[c++] = 1;
    
    //  REMOVE ME !!!!
    std::printf("--> DUMPING UDP PACKET : ");
    int port;
    for( int i = 0 ; i < c ; i++) {
        std::printf("%02x ", packet[i]);
    }
    std::printf("\n\n\n");
    //  Ready to send to DNS
    SOCKET_HANDLE_t sock = _wifi->SocketCreate(UDP);
    if (sock == InvalidSocketHandle) {
        delete packet;
        return false;
    }
 
    INFO("Using %d.%d.%d.%d as DNS !", _dnsip.sin_addr.o1, _dnsip.sin_addr.o2, _dnsip.sin_addr.o3, _dnsip.sin_addr.o4);
    if (!_wifi->SocketSendTo(sock, &_dnsip, 53, packet, packetlen)) {
        delete packet;
        _wifi->SocketClose(sock);
        return false;
    }
    
    delete packet;
    
    packet = new char [1024];
    if (packet == NULL) {
        _wifi->SocketClose(sock);
        return false;
    }
    
    //  Receive the answer from DNS
    Timer t;
    int recvd = 0;
    t.start();
    
    while (t.read_ms() < 10000) {
        if ((recvd = _wifi->SocketRecvFrom (sock, NULL, &port, packet, 1024)) > 0 ) {
            //  process input
            std::printf("Received %d bytes from DNS !\n", recvd);
            if (!resolve(packet, ipaddress)) {
                break;
            }
                        
            //  cleanup and return
            delete packet;
            _wifi->SocketClose(sock);
            return true;
        } else {
            ERR("SocketRecvFrom returned %d !", recvd);
        }
    }    

    delete packet;
    
    _wifi->SocketClose(sock);
        
    return false;
}


bool DnsQuery::resolve(char* resp, IPADDRESS_t &ipaddress)
{
    int ID = (((int)resp[0]) <<8) + resp[1];
    int QR = resp[2] >>7;
    int Opcode = (resp[2]>>3) & 0x0F;
    int RCODE = (resp[3] & 0x0F);
    int ANCOUNT = (((int)resp[6])<<8)+ resp[7];
    
    INFO("Resolving response : ID = %d, QR = %d, Opcode = %d, RCODE = %d", ID, QR, Opcode, RCODE);
    if ((ID != 1) || (QR != 1) || (Opcode != 0) || (RCODE != 0)) {
        ERR("Received non matching response from DNS !");
        return false;
    }
    
    int c = 12;
    int d;
    //  Skip domain question
    while(  (d=resp[c++]) != 0) {
        c+=d;
    }
    c+= 4; //   skip QTYPE and QCLASS
    
    //  Here comes the resource record
    for (int ans = 0 ; ans < ANCOUNT; ans++) {
        if (parseRR(resp, c, ipaddress)) {
            return true;
        }
    }
    
    return false;
}

bool DnsQuery::parseRR(char *resp, int& c, IPADDRESS_t& adr )
{
    int n = 0;
    
    while( (n=resp[c++]) != 0) {
        if ((n & 0xc0) != 0) {
            //  This is a link
            c++;
            break;
        } else {
            c+= n;  //  skip this segment, not interested in string domain names
        }
    }
    
    int TYPE = (((int)resp[c])<<8) + resp[c+1];
    int CLASS = (((int)resp[c+2])<<8) + resp[c+3];
    int RDLENGTH = (((int)resp[c+8])<<8) + resp[c+9];

    INFO("Record of TYPE=%d and CLASS=%d detected !", TYPE, CLASS);
    c+= 10;
    if ((CLASS == 1) && (TYPE == 1)) {
        adr.sin_addr.o1 = resp[c];
        adr.sin_addr.o2 = resp[c+1];
        adr.sin_addr.o3 = resp[c+2];
        adr.sin_addr.o4 = resp[c+3];
        c+= RDLENGTH;
        return true;
    } else {
    }
    c+= RDLENGTH;
    
    return false;
}