2 * X.25 Packet Layer release 002
4 * This is ALPHA test software. This code may break your machine,
5 * randomly fail to work with new releases, misbehave and/or generally
6 * screw up. It might even work.
8 * This code REQUIRES 2.1.15 or higher
11 * This module is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version
14 * 2 of the License, or (at your option) any later version.
17 * X.25 001 Jonathan Naylor Started coding.
18 * X.25 002 Jonathan Naylor New timer architecture.
19 * 2000-09-04 Henner Eisen Prevented x25_output() skb leakage.
20 * 2000-10-27 Henner Eisen MSG_DONTWAIT for fragment allocation.
21 * 2000-11-10 Henner Eisen x25_send_iframe(): re-queued frames
22 * needed cleaned seq-number fields.
25 #include <linux/slab.h>
26 #include <linux/socket.h>
27 #include <linux/kernel.h>
28 #include <linux/string.h>
29 #include <linux/skbuff.h>
33 static int x25_pacsize_to_bytes(unsigned int pacsize)
47 * This is where all X.25 information frames pass.
49 * Returns the amount of user data bytes sent on success
50 * or a negative error code on failure.
52 int x25_output(struct sock *sk, struct sk_buff *skb)
55 unsigned char header[X25_EXT_MIN_LEN];
56 int err, frontlen, len;
57 int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT;
58 struct x25_sock *x25 = x25_sk(sk);
59 int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN :
61 int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
63 if (skb->len - header_len > max_len) {
64 /* Save a copy of the Header */
65 skb_copy_from_linear_data(skb, header, header_len);
66 skb_pull(skb, header_len);
68 frontlen = skb_headroom(skb);
70 while (skb->len > 0) {
71 if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
72 noblock, &err)) == NULL){
73 if (err == -EWOULDBLOCK && noblock){
77 SOCK_DEBUG(sk, "x25_output: fragment alloc"
78 " failed, err=%d, %d bytes "
83 skb_reserve(skbn, frontlen);
85 len = max_len > skb->len ? skb->len : max_len;
87 /* Copy the user data */
88 skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
91 /* Duplicate the Header */
92 skb_push(skbn, header_len);
93 skb_copy_to_linear_data(skbn, header, header_len);
96 if (x25->neighbour->extended)
97 skbn->data[3] |= X25_EXT_M_BIT;
99 skbn->data[2] |= X25_STD_M_BIT;
102 skb_queue_tail(&sk->sk_write_queue, skbn);
108 skb_queue_tail(&sk->sk_write_queue, skb);
109 sent = skb->len - header_len;
115 * This procedure is passed a buffer descriptor for an iframe. It builds
116 * the rest of the control part of the frame and then writes it out.
118 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
120 struct x25_sock *x25 = x25_sk(sk);
125 if (x25->neighbour->extended) {
126 skb->data[2] = (x25->vs << 1) & 0xFE;
127 skb->data[3] &= X25_EXT_M_BIT;
128 skb->data[3] |= (x25->vr << 1) & 0xFE;
130 skb->data[2] &= X25_STD_M_BIT;
131 skb->data[2] |= (x25->vs << 1) & 0x0E;
132 skb->data[2] |= (x25->vr << 5) & 0xE0;
135 x25_transmit_link(skb, x25->neighbour);
138 void x25_kick(struct sock *sk)
140 struct sk_buff *skb, *skbn;
141 unsigned short start, end;
143 struct x25_sock *x25 = x25_sk(sk);
145 if (x25->state != X25_STATE_3)
149 * Transmit interrupt data.
151 if (skb_peek(&x25->interrupt_out_queue) != NULL &&
152 !test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
154 skb = skb_dequeue(&x25->interrupt_out_queue);
155 x25_transmit_link(skb, x25->neighbour);
158 if (x25->condition & X25_COND_PEER_RX_BUSY)
161 if (!skb_peek(&sk->sk_write_queue))
164 modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
166 start = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
167 end = (x25->va + x25->facilities.winsize_out) % modulus;
175 * Transmit data until either we're out of data to send or
176 * the window is full.
179 skb = skb_dequeue(&sk->sk_write_queue);
182 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
183 skb_queue_head(&sk->sk_write_queue, skb);
187 skb_set_owner_w(skbn, sk);
190 * Transmit the frame copy.
192 x25_send_iframe(sk, skbn);
194 x25->vs = (x25->vs + 1) % modulus;
197 * Requeue the original data frame.
199 skb_queue_tail(&x25->ack_queue, skb);
201 } while (x25->vs != end &&
202 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
205 x25->condition &= ~X25_COND_ACK_PENDING;
211 * The following routines are taken from page 170 of the 7th ARRL Computer
212 * Networking Conference paper, as is the whole state machine.
215 void x25_enquiry_response(struct sock *sk)
217 struct x25_sock *x25 = x25_sk(sk);
219 if (x25->condition & X25_COND_OWN_RX_BUSY)
220 x25_write_internal(sk, X25_RNR);
222 x25_write_internal(sk, X25_RR);
225 x25->condition &= ~X25_COND_ACK_PENDING;