1/*
2 *	X.25 Packet Layer release 002
3 *
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.
7 *
8 *	This code REQUIRES 2.1.15 or higher
9 *
10 *	This module:
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.
15 *
16 *	History
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.
23 */
24
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>
30#include <net/sock.h>
31#include <net/x25.h>
32
33static int x25_pacsize_to_bytes(unsigned int pacsize)
34{
35	int bytes = 1;
36
37	if (!pacsize)
38		return 128;
39
40	while (pacsize-- > 0)
41		bytes *= 2;
42
43	return bytes;
44}
45
46/*
47 *	This is where all X.25 information frames pass.
48 *
49 *      Returns the amount of user data bytes sent on success
50 *      or a negative error code on failure.
51 */
52int x25_output(struct sock *sk, struct sk_buff *skb)
53{
54	struct sk_buff *skbn;
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 :
60						    X25_STD_MIN_LEN;
61	int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
62
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);
67
68		frontlen = skb_headroom(skb);
69
70		while (skb->len > 0) {
71			release_sock(sk);
72			skbn = sock_alloc_send_skb(sk, frontlen + max_len,
73						   noblock, &err);
74			lock_sock(sk);
75			if (!skbn) {
76				if (err == -EWOULDBLOCK && noblock){
77					kfree_skb(skb);
78					return sent;
79				}
80				SOCK_DEBUG(sk, "x25_output: fragment alloc"
81					       " failed, err=%d, %d bytes "
82					       "sent\n", err, sent);
83				return err;
84			}
85
86			skb_reserve(skbn, frontlen);
87
88			len = max_len > skb->len ? skb->len : max_len;
89
90			/* Copy the user data */
91			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
92			skb_pull(skb, len);
93
94			/* Duplicate the Header */
95			skb_push(skbn, header_len);
96			skb_copy_to_linear_data(skbn, header, header_len);
97
98			if (skb->len > 0) {
99				if (x25->neighbour->extended)
100					skbn->data[3] |= X25_EXT_M_BIT;
101				else
102					skbn->data[2] |= X25_STD_M_BIT;
103			}
104
105			skb_queue_tail(&sk->sk_write_queue, skbn);
106			sent += len;
107		}
108
109		kfree_skb(skb);
110	} else {
111		skb_queue_tail(&sk->sk_write_queue, skb);
112		sent = skb->len - header_len;
113	}
114	return sent;
115}
116
117/*
118 *	This procedure is passed a buffer descriptor for an iframe. It builds
119 *	the rest of the control part of the frame and then writes it out.
120 */
121static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
122{
123	struct x25_sock *x25 = x25_sk(sk);
124
125	if (!skb)
126		return;
127
128	if (x25->neighbour->extended) {
129		skb->data[2]  = (x25->vs << 1) & 0xFE;
130		skb->data[3] &= X25_EXT_M_BIT;
131		skb->data[3] |= (x25->vr << 1) & 0xFE;
132	} else {
133		skb->data[2] &= X25_STD_M_BIT;
134		skb->data[2] |= (x25->vs << 1) & 0x0E;
135		skb->data[2] |= (x25->vr << 5) & 0xE0;
136	}
137
138	x25_transmit_link(skb, x25->neighbour);
139}
140
141void x25_kick(struct sock *sk)
142{
143	struct sk_buff *skb, *skbn;
144	unsigned short start, end;
145	int modulus;
146	struct x25_sock *x25 = x25_sk(sk);
147
148	if (x25->state != X25_STATE_3)
149		return;
150
151	/*
152	 *	Transmit interrupt data.
153	 */
154	if (skb_peek(&x25->interrupt_out_queue) != NULL &&
155		!test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
156
157		skb = skb_dequeue(&x25->interrupt_out_queue);
158		x25_transmit_link(skb, x25->neighbour);
159	}
160
161	if (x25->condition & X25_COND_PEER_RX_BUSY)
162		return;
163
164	if (!skb_peek(&sk->sk_write_queue))
165		return;
166
167	modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
168
169	start   = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
170	end     = (x25->va + x25->facilities.winsize_out) % modulus;
171
172	if (start == end)
173		return;
174
175	x25->vs = start;
176
177	/*
178	 * Transmit data until either we're out of data to send or
179	 * the window is full.
180	 */
181
182	skb = skb_dequeue(&sk->sk_write_queue);
183
184	do {
185		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
186			skb_queue_head(&sk->sk_write_queue, skb);
187			break;
188		}
189
190		skb_set_owner_w(skbn, sk);
191
192		/*
193		 * Transmit the frame copy.
194		 */
195		x25_send_iframe(sk, skbn);
196
197		x25->vs = (x25->vs + 1) % modulus;
198
199		/*
200		 * Requeue the original data frame.
201		 */
202		skb_queue_tail(&x25->ack_queue, skb);
203
204	} while (x25->vs != end &&
205		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
206
207	x25->vl         = x25->vr;
208	x25->condition &= ~X25_COND_ACK_PENDING;
209
210	x25_stop_timer(sk);
211}
212
213/*
214 * The following routines are taken from page 170 of the 7th ARRL Computer
215 * Networking Conference paper, as is the whole state machine.
216 */
217
218void x25_enquiry_response(struct sock *sk)
219{
220	struct x25_sock *x25 = x25_sk(sk);
221
222	if (x25->condition & X25_COND_OWN_RX_BUSY)
223		x25_write_internal(sk, X25_RNR);
224	else
225		x25_write_internal(sk, X25_RR);
226
227	x25->vl         = x25->vr;
228	x25->condition &= ~X25_COND_ACK_PENDING;
229
230	x25_stop_timer(sk);
231}
232