/*
 * pconfig.h
 * ptunnel is licensed under the BSD license:
 *
 * Copyright (c) 2004-2011, Daniel Stoedle <daniels@cs.uit.no>,
 * Yellow Lemon Software. All rights reserved.
 *
 * Copyright (c) 2017-2019, Toni Uhlig <matzeton@googlemail.com>
 *
 * 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.
 *
 * - Neither the name of the Yellow Lemon Software nor the names of its
 *   contributors may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * 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.
 *
 * Contacting the author:
 * You can get in touch with me, Daniel Stødle (that's the Norwegian letter oe,
 * in case your text editor didn't realize), here: <daniels@cs.uit.no>
 *
 * The official ptunnel website is here:
 * <http://www.cs.uit.no/~daniels/PingTunnel/>
 *
 * Note that the source code is best viewed with tabs set to 4 spaces.
 */

#ifndef PCONFIG_H
#define PCONFIG_H 1

enum {
    /** Set this constant to the number of
     * concurrent connections you wish to handle by default.
     */
    kMax_tunnels = 10,
    /** numbers */
    kIP_packet_max_size = 576,
    /** In bytes, mind you */
    kIP_header_size = 20,
    kIP_actual_size = (kIP_packet_max_size - kIP_header_size) - ((kIP_packet_max_size - kIP_header_size) % 8),
    /** Also in bytes */
    kICMP_header_size = 8,
    /** This constant control the maximum size of
     * the payload-portion of the ICMP packets
     * we send. Note that this does not include
     * the IP or ICMP headers!
     */
    kDefault_buf_size = 1024,
    /** Type code for echo request and replies */
    kICMP_echo_request = 8,
    kICMP_echo_reply = 0,
    /** number of packets we can have in our send/receive ring */
    kPing_window_size = 64,
    /** Tunnels are automatically closed after one minute of inactivity. Since
     * we continously send acknowledgements between the two peers, this mechanism
     * won't disconnect "valid" connections.
     */
    kAutomatic_close_timeout = 60, //  Seconds!
    /** size of md5 digest in bytes */
    kMD5_digest_size = 16,
    /** size of sha512 digest in bytes */
    kSHA512_digest_size = 64,
    kDNS_port = 53
};

enum oper_mode {
    /** Ping tunnel's operating mode (client) */
    kMode_forward = 0,
    /** Ping tunnel's operating mode (server) */
    kMode_proxy
};

enum pkt_flag {
    /** set when packet comes from a user */
    kUser_flag = 1 << 30,
    /** set when packet comes from the proxy */
    kProxy_flag = 1 << 31,
    kFlag_mask = kUser_flag | kProxy_flag
};

enum log_level {
    /** Different verbosity levels. */
    kNo_log = -1,
    kLog_error = 0,
    kLog_info,
    kLog_event,
    kLog_verbose,
    kLog_debug,
    kLog_sendrecv
};

enum proxy_state {
    /** These constants are used to indicate the protocol state. The protocol
     * works as follows:
     * - The identifier is used by both the proxy and the forwarder
     * to identify the session (and thus the relevant sockets).
     * - The seq-no of the ping packet is used in a sliding-window-esque
     * way, and to identify the order of data.
     *
     * The protocol can be in any of the following states:
     * kProxy_start        Causes the proxy to open a connection to the given
     *                     host and port, associating the ID with the socket,
     *                     before the data on the socket are transmitted.
     * kProxy_data     Indicates that the packet contains data from the proxy.
     *                     Data ordering is indicated by the seq-no, which will start
     *                     at 0. (The proxy and forwarder maintain different seq-nos.)
     * kUser_data      This packet contains user data.
     * kConnection_close   Indicates that the connection is being closed.
     * kProxy_ack and      Acknowledges the packet (and all packets before it) with seq_no = ack.
     * kUser_ack       This is used if there are no implicit acknowledgements due to data
     *                     being sent.
     *
     * Acknowledgements work by the remote peer acknowledging the last
     * continuous seq no it has received.
     *
     * Note: A proxy receiving a kProxy_data packet, or a user receiving a
     * kUser_data packet, should ignore it, as it is the host operating system
     * actually returning the ping. This is mostly relevant for users, and for
     * proxies running in unprivileged mode.
     */
    kProxy_start = 0,
    kProto_ack,
    kProto_data,
    kProto_close,
    kProto_authenticate,
    kNum_proto_types
};

#endif