For example, running it on my machine and performing queries in a
virtual machine, this is the output I get:
/*
* Copyright (c) 2016, Matias Fontanini
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <tins/tins.h>
#include <iostream>
using std :: cout ;
using std :: endl ;
using namespace Tins ;
PacketSender sender ;
bool callback ( const PDU & pdu ) {
// The packet probably looks like this:
//
// EthernetII / IP / UDP / RawPDU
//
// So we retrieve each layer, and construct a
// DNS PDU from the RawPDU layer contents.
EthernetII eth = pdu . rfind_pdu < EthernetII > ();
IP ip = eth . rfind_pdu < IP > ();
UDP udp = ip . rfind_pdu < UDP > ();
DNS dns = udp . rfind_pdu < RawPDU > (). to < DNS > ();
// Is it a DNS query?
if ( dns . type () == DNS :: QUERY ) {
// Let's see if there's any query for an "A" record.
for ( const auto & query : dns . queries ()) {
if ( query . query_type () == DNS :: A ) {
// Here's one! Let's add an answer.
dns . add_answer (
DNS :: resource (
query . dname (),
"127.0.0.1" ,
DNS :: A ,
query . query_class (),
// 777 is just a random TTL
777
)
);
}
}
// Have we added some answers?
if ( dns . answers_count () > 0 ) {
// It's a response now
dns . type ( DNS :: RESPONSE );
// Recursion is available(just in case)
dns . recursion_available ( 1 );
// Build our packet
auto pkt = EthernetII ( eth . src_addr (), eth . dst_addr ()) /
IP ( ip . src_addr (), ip . dst_addr ()) /
UDP ( udp . sport (), udp . dport ()) /
dns ;
// Send it!
sender . send ( pkt );
}
}
return true ;
}
int main ( int argc , char * argv []) {
if ( argc != 2 ) {
cout << "Usage: " <<* argv << " <interface>" << endl ;
return 1 ;
}
// Sniff on the provided interface in promiscuos mode
SnifferConfiguration config ;
config . set_promisc_mode ( true );
// Use immediate mode so we get the packets as fast as we can
config . set_immediate_mode ( true );
// Only capture udp packets sent to port 53
config . set_filter ( "udp and dst port 53" );
Sniffer sniffer ( argv [ 1 ], config );
// All packets will be sent through the provided interface
sender . default_interface ( argv [ 1 ]);
// Start the capture
sniffer . sniff_loop ( callback );
}