/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Copyright Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/netrom.h>

/*
 *      This routine purges all of the queues of frames.
 */
void nr_clear_queues(struct sock *sk)
{
        struct nr_sock *nr = nr_sk(sk);

        skb_queue_purge(&sk->sk_write_queue);
        skb_queue_purge(&nr->ack_queue);
        skb_queue_purge(&nr->reseq_queue);
        skb_queue_purge(&nr->frag_queue);
}

/*
 * This routine purges the input queue of those frames that have been
 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
 * SDL diagram.
 */
void nr_frames_acked(struct sock *sk, unsigned short nr)
{
        struct nr_sock *nrom = nr_sk(sk);
        struct sk_buff *skb;

        /*
         * Remove all the ack-ed frames from the ack queue.
         */
        if (nrom->va != nr) {
                while (skb_peek(&nrom->ack_queue) != NULL && nrom->va != nr) {
                        skb = skb_dequeue(&nrom->ack_queue);
                        kfree_skb(skb);
                        nrom->va = (nrom->va + 1) % NR_MODULUS;
                }
        }
}

/*
 * Requeue all the un-ack-ed frames on the output queue to be picked
 * up by nr_kick called from the timer. This arrangement handles the
 * possibility of an empty output queue.
 */
void nr_requeue_frames(struct sock *sk)
{
        struct sk_buff *skb, *skb_prev = NULL;

        while ((skb = skb_dequeue(&nr_sk(sk)->ack_queue)) != NULL) {
                if (skb_prev == NULL)
                        skb_queue_head(&sk->sk_write_queue, skb);
                else
                        skb_append(skb_prev, skb, &sk->sk_write_queue);
                skb_prev = skb;
        }
}

/*
 *      Validate that the value of nr is between va and vs. Return true or
 *      false for testing.
 */
int nr_validate_nr(struct sock *sk, unsigned short nr)
{
        struct nr_sock *nrom = nr_sk(sk);
        unsigned short vc = nrom->va;

        while (vc != nrom->vs) {
                if (nr == vc) return 1;
                vc = (vc + 1) % NR_MODULUS;
        }

        return nr == nrom->vs;
}

/*
 *      Check that ns is within the receive window.
 */
int nr_in_rx_window(struct sock *sk, unsigned short ns)
{
        struct nr_sock *nr = nr_sk(sk);
        unsigned short vc = nr->vr;
        unsigned short vt = (nr->vl + nr->window) % NR_MODULUS;

        while (vc != vt) {
                if (ns == vc) return 1;
                vc = (vc + 1) % NR_MODULUS;
        }

        return 0;
}

/*
 *  This routine is called when the HDLC layer internally generates a
 *  control frame.
 */
void nr_write_internal(struct sock *sk, int frametype)
{
        struct nr_sock *nr = nr_sk(sk);
        struct sk_buff *skb;
        unsigned char  *dptr;
        int len, timeout;

        len = NR_NETWORK_LEN + NR_TRANSPORT_LEN;

        switch (frametype & 0x0F) {
        case NR_CONNREQ:
                len += 17;
                break;
        case NR_CONNACK:
                len += (nr->bpqext) ? 2 : 1;
                break;
        case NR_DISCREQ:
        case NR_DISCACK:
        case NR_INFOACK:
                break;
        default:
                printk(KERN_ERR "NET/ROM: nr_write_internal - invalid frame type %d\n", frametype);
                return;
        }

        if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
                return;

        /*
         *      Space for AX.25 and NET/ROM network header
         */
        skb_reserve(skb, NR_NETWORK_LEN);

        dptr = skb_put(skb, skb_tailroom(skb));

        switch (frametype & 0x0F) {
        case NR_CONNREQ:
                timeout  = nr->t1 / HZ;
                *dptr++  = nr->my_index;
                *dptr++  = nr->my_id;
                *dptr++  = 0;
                *dptr++  = 0;
                *dptr++  = frametype;
                *dptr++  = nr->window;
                memcpy(dptr, &nr->user_addr, AX25_ADDR_LEN);
                dptr[6] &= ~AX25_CBIT;
                dptr[6] &= ~AX25_EBIT;
                dptr[6] |= AX25_SSSID_SPARE;
                dptr    += AX25_ADDR_LEN;
                memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
                dptr[6] &= ~AX25_CBIT;
                dptr[6] &= ~AX25_EBIT;
                dptr[6] |= AX25_SSSID_SPARE;
                dptr    += AX25_ADDR_LEN;
                *dptr++  = timeout % 256;
                *dptr++  = timeout / 256;
                break;

        case NR_CONNACK:
                *dptr++ = nr->your_index;
                *dptr++ = nr->your_id;
                *dptr++ = nr->my_index;
                *dptr++ = nr->my_id;
                *dptr++ = frametype;
                *dptr++ = nr->window;
                if (nr->bpqext) *dptr++ = sysctl_netrom_network_ttl_initialiser;
                break;

        case NR_DISCREQ:
        case NR_DISCACK:
                *dptr++ = nr->your_index;
                *dptr++ = nr->your_id;
                *dptr++ = 0;
                *dptr++ = 0;
                *dptr++ = frametype;
                break;

        case NR_INFOACK:
                *dptr++ = nr->your_index;
                *dptr++ = nr->your_id;
                *dptr++ = 0;
                *dptr++ = nr->vr;
                *dptr++ = frametype;
                break;
        }

        nr_transmit_buffer(sk, skb);
}

/*
 * This routine is called to send an error reply.
 */
void __nr_transmit_reply(struct sk_buff *skb, int mine, unsigned char cmdflags)
{
        struct sk_buff *skbn;
        unsigned char *dptr;
        int len;

        len = NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1;

        if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL)
                return;

        skb_reserve(skbn, 0);

        dptr = skb_put(skbn, NR_NETWORK_LEN + NR_TRANSPORT_LEN);

        skb_copy_from_linear_data_offset(skb, 7, dptr, AX25_ADDR_LEN);
        dptr[6] &= ~AX25_CBIT;
        dptr[6] &= ~AX25_EBIT;
        dptr[6] |= AX25_SSSID_SPARE;
        dptr += AX25_ADDR_LEN;

        skb_copy_from_linear_data(skb, dptr, AX25_ADDR_LEN);
        dptr[6] &= ~AX25_CBIT;
        dptr[6] |= AX25_EBIT;
        dptr[6] |= AX25_SSSID_SPARE;
        dptr += AX25_ADDR_LEN;

        *dptr++ = sysctl_netrom_network_ttl_initialiser;

        if (mine) {
                *dptr++ = 0;
                *dptr++ = 0;
                *dptr++ = skb->data[15];
                *dptr++ = skb->data[16];
        } else {
                *dptr++ = skb->data[15];
                *dptr++ = skb->data[16];
                *dptr++ = 0;
                *dptr++ = 0;
        }

        *dptr++ = cmdflags;
        *dptr++ = 0;

        if (!nr_route_frame(skbn, NULL))
                kfree_skb(skbn);
}

void nr_disconnect(struct sock *sk, int reason)
{
        nr_stop_t1timer(sk);
        nr_stop_t2timer(sk);
        nr_stop_t4timer(sk);
        nr_stop_idletimer(sk);

        nr_clear_queues(sk);

        nr_sk(sk)->state = NR_STATE_0;

        sk->sk_state     = TCP_CLOSE;
        sk->sk_err       = reason;
        sk->sk_shutdown |= SEND_SHUTDOWN;

        if (!sock_flag(sk, SOCK_DEAD)) {
                sk->sk_state_change(sk);
                sock_set_flag(sk, SOCK_DEAD);
        }
}