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/*
* 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)
* Copyright Darryl Miles G7LED (dlm@g7led.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 <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/netrom.h>

/*
* This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
* cannot be fragmented in this manner.
*/
void nr_output(struct sock *sk, struct sk_buff *skb)
{
struct sk_buff *skbn;
unsigned char transport[NR_TRANSPORT_LEN];
int err, frontlen, len;

if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
/* Save a copy of the Transport Header */
skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
skb_pull(skb, NR_TRANSPORT_LEN);

frontlen = skb_headroom(skb);

while (skb->len > 0) {
if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
return;

skb_reserve(skbn, frontlen);

len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;

/* Copy the user data */
skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
skb_pull(skb, len);

/* Duplicate the Transport Header */
skb_push(skbn, NR_TRANSPORT_LEN);
skb_copy_to_linear_data(skbn, transport,
NR_TRANSPORT_LEN);
if (skb->len > 0)
skbn->data[4] |= NR_MORE_FLAG;

skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
}

kfree_skb(skb);
} else {
skb_queue_tail(&sk->sk_write_queue, skb); /* Throw it on the queue */
}

nr_kick(sk);
}

/*
* This procedure is passed a buffer descriptor for an iframe. It builds
* the rest of the control part of the frame and then writes it out.
*/
static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
{
struct nr_sock *nr = nr_sk(sk);

if (skb == NULL)
return;

skb->data[2] = nr->vs;
skb->data[3] = nr->vr;

if (nr->condition & NR_COND_OWN_RX_BUSY)
skb->data[4] |= NR_CHOKE_FLAG;

nr_start_idletimer(sk);

nr_transmit_buffer(sk, skb);
}

void nr_send_nak_frame(struct sock *sk)
{
struct sk_buff *skb, *skbn;
struct nr_sock *nr = nr_sk(sk);

if ((skb = skb_peek(&nr->ack_queue)) == NULL)
return;

if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
return;

skbn->data[2] = nr->va;
skbn->data[3] = nr->vr;

if (nr->condition & NR_COND_OWN_RX_BUSY)
skbn->data[4] |= NR_CHOKE_FLAG;

nr_transmit_buffer(sk, skbn);

nr->condition &= ~NR_COND_ACK_PENDING;
nr->vl = nr->vr;

nr_stop_t1timer(sk);
}

void nr_kick(struct sock *sk)
{
struct nr_sock *nr = nr_sk(sk);
struct sk_buff *skb, *skbn;
unsigned short start, end;

if (nr->state != NR_STATE_3)
return;

if (nr->condition & NR_COND_PEER_RX_BUSY)
return;

if (!skb_peek(&sk->sk_write_queue))
return;

start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs;
end = (nr->va + nr->window) % NR_MODULUS;

if (start == end)
return;

nr->vs = start;

/*
* Transmit data until either we're out of data to send or
* the window is full.
*/

/*
* Dequeue the frame and copy it.
*/
skb = skb_dequeue(&sk->sk_write_queue);

do {
if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
skb_queue_head(&sk->sk_write_queue, skb);
break;
}

skb_set_owner_w(skbn, sk);

/*
* Transmit the frame copy.
*/
nr_send_iframe(sk, skbn);

nr->vs = (nr->vs + 1) % NR_MODULUS;

/*
* Requeue the original data frame.
*/
skb_queue_tail(&nr->ack_queue, skb);

} while (nr->vs != end &&
(skb = skb_dequeue(&sk->sk_write_queue)) != NULL);

nr->vl = nr->vr;
nr->condition &= ~NR_COND_ACK_PENDING;

if (!nr_t1timer_running(sk))
nr_start_t1timer(sk);
}

void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
{
struct nr_sock *nr = nr_sk(sk);
unsigned char *dptr;

/*
* Add the protocol byte and network header.
*/
dptr = skb_push(skb, NR_NETWORK_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;

memcpy(dptr, &nr->dest_addr, 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 (!nr_route_frame(skb, NULL)) {
kfree_skb(skb);
nr_disconnect(sk, ENETUNREACH);
}
}

/*
* The following routines are taken from page 170 of the 7th ARRL Computer
* Networking Conference paper, as is the whole state machine.
*/

void nr_establish_data_link(struct sock *sk)
{
struct nr_sock *nr = nr_sk(sk);

nr->condition = 0x00;
nr->n2count = 0;

nr_write_internal(sk, NR_CONNREQ);

nr_stop_t2timer(sk);
nr_stop_t4timer(sk);
nr_stop_idletimer(sk);
nr_start_t1timer(sk);
}

/*
* Never send a NAK when we are CHOKEd.
*/
void nr_enquiry_response(struct sock *sk)
{
struct nr_sock *nr = nr_sk(sk);
int frametype = NR_INFOACK;

if (nr->condition & NR_COND_OWN_RX_BUSY) {
frametype |= NR_CHOKE_FLAG;
} else {
if (skb_peek(&nr->reseq_queue) != NULL)
frametype |= NR_NAK_FLAG;
}

nr_write_internal(sk, frametype);

nr->vl = nr->vr;
nr->condition &= ~NR_COND_ACK_PENDING;
}

void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
{
struct nr_sock *nrom = nr_sk(sk);

if (nrom->vs == nr) {
nr_frames_acked(sk, nr);
nr_stop_t1timer(sk);
nrom->n2count = 0;
} else {
if (nrom->va != nr) {
nr_frames_acked(sk, nr);
nr_start_t1timer(sk);
}
}
}
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