/*

    Terminal Mixer - multi-point multi-user access to terminal applications

    Copyright (C) 2007  Lluís Batlle i Rossell

    Please find the license in the provided COPYING file.

*/

#include <netinet/in.h>

#include <string.h>

#include <assert.h>

#include <stdio.h>

#include <errno.h>

#include "eth_linux.h"

#include "main.h"

enum {

    MAXPACKET = 1500,

    MAXSEQ = 100,

    HEAD = 9

};

static struct

{

    int socket;

    char partner[6];

    int partner_set;

    int send_acked;

    int send_retries_left;

    unsigned int seq_send;

    unsigned int seq_wait;

    unsigned int wrong_recv;

    char send_buffer[MAXPACKET];

    int send_buffer_size;

} edata;

enum Control {

    SEND,

    ACK,

    INIT

};

static char eth_buffer[MAXPACKET];

static void eth_fill_mac(unsigned char *mac, const char *str);

static int make_head(unsigned char *data, unsigned int seq, enum Control c,

        int size)

{

    *((unsigned int *) data) = htonl(seq);

    data[4] = (unsigned char) c;

    *((unsigned int *)(data+5)) = htonl(size);

    return HEAD;

}

static int parse_head(unsigned char *data, unsigned int *seq, enum Control *c,

        int *size)

{

    *seq = ntohl( *((unsigned int*) data) );

    *c = data[4];

    if (size)

        *size = ntohl(*((unsigned int *)(data+5)));

    return HEAD;

}

int eth_proto_max_send()

{

    return MAXPACKET - HEAD;

}

void eth_proto_init()

{

    edata.socket = -1;

    edata.seq_send = 0;

    edata.seq_wait = 0;

    edata.send_acked = 1; /* Fine at the beginning, as if the last data was acked */

    edata.partner_set = 0;

}

int eth_proto_allow_sending()

{

    return edata.send_acked;

}

static int seq_next(int val)

{

    if (val >= 0 && val < MAXSEQ)

        val = val + 1;

    else

        val = 0;

    return val;

}

static int seq_before(int val)

{

    if (val > 0 && val < MAXSEQ)

        val = val - 1;

    else

        val = MAXSEQ;

    return val;

}

int eth_proto_open()

{

    edata.socket = eth_open(command_line.eth_device);

    if (edata.socket == -1)

        error("Cannot open device %s", command_line.eth_device);

    if ( !command_line.is_server)

    {

        if (command_line.c_param.server_address == 0)

            error("You must specify the MAC you want to connect to.");

        eth_fill_mac(edata.partner, command_line.c_param.server_address);

        edata.partner_set = 1;

        make_head(eth_buffer, edata.seq_send, INIT, 0);

        eth_send(command_line.eth_device, edata.partner, eth_buffer, HEAD);

        edata.seq_send = seq_next(edata.seq_send);

    }

    return edata.socket;

}

int eth_proto_recv(char *data, int size)

{

    int res;

    int seq;

    int data_length;

    enum Control c;

    char partner[6];

    do {

            res = eth_recv(eth_buffer, sizeof(eth_buffer), partner);

            edata.partner_set = 1;

    } while(res < HEAD);

    parse_head(eth_buffer, &seq, &c, &data_length);

    /* We admit any first connection */

    if (seq == 0 && c == INIT)

    {

      edata.seq_wait = 1; /* next of the just receive 0 */

      memcpy(edata.partner, partner, sizeof(edata.partner));

      return -1; /* Nothing the parent should care about */

    }

    if (c == SEND)

    {

        if (seq != edata.seq_wait && seq != seq_before(edata.seq_wait))

        {

            dump_line("Wrong data packet seq received. Recvd: %i Expected: %i\n",

                    seq, edata.seq_wait);

            edata.wrong_recv++;

            return -1;

        }

        if (seq == seq_before(edata.seq_wait))

            dump_line("Repeated data seq received: %i\n", seq);

        if (seq == edata.seq_wait)

        {

            if (data_length == 0)

            {

                edata.partner_set = 0;

                edata.seq_wait = 0;

                edata.seq_send = 0;

                /* We should send ACK anyway */

            }

            else

            {

                memcpy(data, eth_buffer + HEAD, data_length);

                edata.seq_wait = seq_next(edata.seq_wait);

            }

        }

        /* Ack the packed we received. In these conditions:

         * - We received the packed we expected

         * - We received a repeat of the old packet. The

         *   ACK was lost probably, so we resend it */

        make_head(eth_buffer, seq, ACK, 0);

        eth_send(command_line.eth_device, edata.partner, eth_buffer, HEAD);

    }

    else if (c == ACK)

    {

        if (seq == edata.seq_send)

        {

            edata.send_acked = 1;

            edata.seq_send = seq_next(edata.seq_send);

            unprogram_timeout();

        }

        else

        {

            dump_line("Wrong ack received. Recvd: %i Expected: %i\n",

                    seq, edata.seq_send);

        }

        return -1; /* not data */

    }

    else

        return -1;

    return data_length;

}

static int eth_proto_link_send()

{

    int sent;

    sent = eth_send(command_line.eth_device,

            edata.partner,

            edata.send_buffer,

            edata.send_buffer_size);

    if (sent >= 0) /* expected */

    {

        edata.send_retries_left -= 1;

        edata.send_acked = 0;

        program_timeout(1);

    }

    else /* strange case, data not sent */

    {

        sent = 0;

        edata.send_acked = 1;

    }

    return sent;

}

int eth_proto_send(const char *data, int size)

{

    int sent;

    assert(edata.send_acked);

    if (!edata.partner_set)

    {

        if (edata.seq_send == 0 && !command_line.is_server

                && command_line.c_param.server_address != 0)

        {

            eth_fill_mac(edata.partner, command_line.c_param.server_address);

            edata.partner_set = 1;

        }

        else

            return 0;

    }

    edata.send_retries_left = 3;

    /* Prepare packet */

    make_head(edata.send_buffer, edata.seq_send, SEND, size);

    memcpy(edata.send_buffer+HEAD, data, size);

    edata.send_buffer_size = size + HEAD;

    sent = eth_proto_link_send();

    sent -= HEAD;

    return sent;

}

int eth_proto_process_timeouts()

{

    if (!edata.send_acked && did_timeout_happen())

    {

        unprogram_timeout();

        if (edata.send_retries_left > 0)

        {

            dump_line("Retrying. Left:%i\n", edata.send_retries_left);

            eth_proto_link_send();

        }

        else

        {

            /* The connection has been lost */

            dump_line("Connection lost");

            edata.send_acked = 1;

            edata.partner_set = 0;

            edata.seq_wait = 0;

            edata.seq_send = 0;

            return 0; /* FAIL */

        }

    }

    return 1; /* OK */

}

static void eth_fill_mac(unsigned char *mac, const char *str)

{

  int res;

  int imac[6];

  res = sscanf(str, "%x:%x:%x:%x:%x:%x",

      &imac[0], &imac[1], &imac[2], &imac[3], &imac[4], &imac[5]);

  if (res != 6)

  {

    error("Error parsing mac: %02x:%02x:%02x:%02x:%02x:%02x\n",

      imac[0], imac[1], imac[2], imac[3], imac[4], imac[5]);

  }

  mac[0] = imac[0];  mac[1] = imac[1];  mac[2] = imac[2];

  mac[3] = imac[3];  mac[4] = imac[4];  mac[5] = imac[5];

}