This small example sniffs DNS queries and prints the domain names being queried

You can download this code here.

/*
* 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;

bool callback(const PDU& pdu) {
// The packet probably looks like this:
//
// EthernetII / IP / UDP / RawPDU
//
// So we retrieve the RawPDU layer, and construct a
// DNS PDU using its contents.
DNS dns = pdu.rfind_pdu<RawPDU>().to<DNS>();

// Retrieve the queries and print the domain name:
for (const auto& query : dns.queries()) {
cout << query.dname() << std::endl;
}
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);
// Only capture udp packets sent to port 53
config.set_filter("udp and dst port 53");
Sniffer sniffer(argv[1], config);

// Start the capture
sniffer.sniff_loop(callback);
}