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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* X.25 Packet Layer release 002
*
* This is ALPHA test software. This code may break your machine,
* randomly fail to work with new releases, misbehave and/or generally
* screw up. It might even work.
*
* This code REQUIRES 2.1.15 or higher
*
* History
* X.25 001 Jonathan Naylor Started coding.
* X.25 002 Jonathan Naylor New timer architecture.
* 2000-09-04 Henner Eisen Prevented x25_output() skb leakage.
* 2000-10-27 Henner Eisen MSG_DONTWAIT for fragment allocation.
* 2000-11-10 Henner Eisen x25_send_iframe(): re-queued frames
* needed cleaned seq-number fields.
*/
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/x25.h>
static int x25_pacsize_to_bytes(unsigned int pacsize)
{
int bytes = 1;
if (!pacsize)
return 128;
while (pacsize-- > 0)
bytes *= 2;
return bytes;
}
/*
* This is where all X.25 information frames pass.
*
* Returns the amount of user data bytes sent on success
* or a negative error code on failure.
*/
int x25_output(struct sock *sk, struct sk_buff *skb)
{
struct sk_buff *skbn;
unsigned char header[X25_EXT_MIN_LEN];
int err, frontlen, len;
int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT;
struct x25_sock *x25 = x25_sk(sk);
int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN :
X25_STD_MIN_LEN;
int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
if (skb->len - header_len > max_len) {
/* Save a copy of the Header */
skb_copy_from_linear_data(skb, header, header_len);
skb_pull(skb, header_len);
frontlen = skb_headroom(skb);
while (skb->len > 0) {
release_sock(sk);
skbn = sock_alloc_send_skb(sk, frontlen + max_len,
noblock, &err);
lock_sock(sk);
if (!skbn) {
if (err == -EWOULDBLOCK && noblock){
kfree_skb(skb);
return sent;
}
SOCK_DEBUG(sk, "x25_output: fragment alloc"
" failed, err=%d, %d bytes "
"sent\n", err, sent);
return err;
}
skb_reserve(skbn, frontlen);
len = max_len > skb->len ? skb->len : max_len;
/* Copy the user data */
skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
skb_pull(skb, len);
/* Duplicate the Header */
skb_push(skbn, header_len);
skb_copy_to_linear_data(skbn, header, header_len);
if (skb->len > 0) {
if (x25->neighbour->extended)
skbn->data[3] |= X25_EXT_M_BIT;
else
skbn->data[2] |= X25_STD_M_BIT;
}
skb_queue_tail(&sk->sk_write_queue, skbn);
sent += len;
}
kfree_skb(skb);
} else {
skb_queue_tail(&sk->sk_write_queue, skb);
sent = skb->len - header_len;
}
return sent;
}
/*
* 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 x25_send_iframe(struct sock *sk, struct sk_buff *skb)
{
struct x25_sock *x25 = x25_sk(sk);
if (!skb)
return;
if (x25->neighbour->extended) {
skb->data[2] = (x25->vs << 1) & 0xFE;
skb->data[3] &= X25_EXT_M_BIT;
skb->data[3] |= (x25->vr << 1) & 0xFE;
} else {
skb->data[2] &= X25_STD_M_BIT;
skb->data[2] |= (x25->vs << 1) & 0x0E;
skb->data[2] |= (x25->vr << 5) & 0xE0;
}
x25_transmit_link(skb, x25->neighbour);
}
void x25_kick(struct sock *sk)
{
struct sk_buff *skb, *skbn;
unsigned short start, end;
int modulus;
struct x25_sock *x25 = x25_sk(sk);
if (x25->state != X25_STATE_3)
return;
/*
* Transmit interrupt data.
*/
if (skb_peek(&x25->interrupt_out_queue) != NULL &&
!test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
skb = skb_dequeue(&x25->interrupt_out_queue);
x25_transmit_link(skb, x25->neighbour);
}
if (x25->condition & X25_COND_PEER_RX_BUSY)
return;
if (!skb_peek(&sk->sk_write_queue))
return;
modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
start = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
end = (x25->va + x25->facilities.winsize_out) % modulus;
if (start == end)
return;
x25->vs = start;
/*
* Transmit data until either we're out of data to send or
* the window is full.
*/
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.
*/
x25_send_iframe(sk, skbn);
x25->vs = (x25->vs + 1) % modulus;
/*
* Requeue the original data frame.
*/
skb_queue_tail(&x25->ack_queue, skb);
} while (x25->vs != end &&
(skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
x25->vl = x25->vr;
x25->condition &= ~X25_COND_ACK_PENDING;
x25_stop_timer(sk);
}
/*
* The following routines are taken from page 170 of the 7th ARRL Computer
* Networking Conference paper, as is the whole state machine.
*/
void x25_enquiry_response(struct sock *sk)
{
struct x25_sock *x25 = x25_sk(sk);
if (x25->condition & X25_COND_OWN_RX_BUSY)
x25_write_internal(sk, X25_RNR);
else
x25_write_internal(sk, X25_RR);
x25->vl = x25->vr;
x25->condition &= ~X25_COND_ACK_PENDING;
x25_stop_timer(sk);
}
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