aboutsummaryrefslogtreecommitdiff
path: root/net/x25/x25_out.c
blob: 2b96b52114d6235980325df17ef92f8adb6c8dfd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
/*
 *	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
 *
 *	This module:
 *		This module 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.
 *
 *	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/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) {
			if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
							noblock, &err)) == NULL){
				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 (!x25->intflag && skb_peek(&x25->interrupt_out_queue) != NULL) {
		x25->intflag = 1;
		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);
}