#ifndef TCPOPTIONCUSTOMCHANNEL_H
#define TCPOPTIONCUSTOMCHANNEL_H

#include "../BidirectionalChannels.hpp"

/**
 * @class TCPOptionCustom
 *
 * A CovertChannel which hides data in a custom field in the TCP options data
 *
 * In theory, any options field can be used to store data. This implementation specifically uses field 11 (CC).
 * For (un)usable fields, refer to the IANA listing at
 * https://www.iana.org/assignments/tcp-parameters/tcp-parameters.xhtml
 *
 * @param N number of bytes which can be used to transmit data
 * @param PASSIVE true - server only reacts to incoming channel | false - server initiates channel
 */
template <int N, bool PASSIVE> class TCPOptionCustomChannel : public BidirectionalChannels<N, PASSIVE> {
	static_assert(N <= 255 - 2);

public:
	/**
	 * Sets up a CovertChannel.
	 *
	 * Creates a CovertChannel, sets the network interfaces for sniffing and sending and sets the filter.
	 *
	 * @param innerInterface name of the interface of the inner network
	 * @param outerInterface name of the interface of the outer network
	 * @param targetIP IP of the target server
	 * @param targetPort Port of the target server
	 */
	TCPOptionCustomChannel(const std::string &innerInterface, const std::string &outerInterface, const std::string &targetIP, const std::string &targetPort)
	    : BidirectionalChannels<N, PASSIVE>(innerInterface, outerInterface, targetIP, targetPort) {}

	/**
	 * Destroys the CovertChannel.
	 */
	virtual ~TCPOptionCustomChannel() {}

protected:
	// this is the id of the option as found in the article found at the top
	const unsigned int target_options_id = 11;

	/**
	 * Handler for sniffed packets filterd to forward from the outer network.
	 *
	 * Handles incoming packets and forwards them.
	 *
	 * @param pdu sniffed packet
	 *
	 * @return false = stop loop | true = continue loop
	 */
	virtual bool handleChannelFromOuter(Tins::PDU &pdu) {
		Tins::TCP &tcp = pdu.rfind_pdu<Tins::TCP>();

		const Tins::TCP::options_type &options = tcp.options();
		Tins::TCP::option op;
		size_t i;
		// find option field
		for (i = 0; i < options.size(); i++) {
			if (options[i].option() == target_options_id) {
				op = options[i];
				break;
			}
		}
		if (i != options.size() && options[i].data_size()) {
			// found the option
			BidirectionalChannels<N, PASSIVE>::protocol.receive((uint8_t *)(options[i].data_ptr()));
			tcp.remove_option((Tins::TCP::OptionTypes)target_options_id);
		}

		BidirectionalChannels<N, PASSIVE>::innerSender.send(pdu);

		return true;
	}

	/**
	 * Handler for sniffed packets filterd to forward from the inner network.
	 *
	 * Handles incoming packets and forwards them.
	 *
	 * @param pdu sniffed packet
	 *
	 * @return false = stop loop | true = continue loop
	 */
	virtual bool handleChannelFromInner(Tins::PDU &pdu) {
		Tins::TCP &tcp = pdu.rfind_pdu<Tins::TCP>();
		uint8_t data[N];
		BidirectionalChannels<N, PASSIVE>::protocol.send(data);

		Tins::TCP::option op(target_options_id, N, data);
		tcp.add_option(op);

		BidirectionalChannels<N, PASSIVE>::outerSender.send(pdu);

		return true;
	}
};

#endif