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/socket.h>
26 #include <linux/kernel.h>
27 #include <linux/string.h>
28 #include <linux/skbuff.h>
29 #include <net/sock.h>
30 #include <net/x25.h>
31
32 static int x25_pacsize_to_bytes(unsigned int pacsize)
33 {
34 int bytes = 1;
35
36 if (!pacsize)
37 return 128;
38
39 while (pacsize-- > 0)
40 bytes *= 2;
41
42 return bytes;
43 }
44
45 /*
46 * This is where all X.25 information frames pass.
47 *
48 * Returns the amount of user data bytes sent on success
49 * or a negative error code on failure.
50 */
51 int x25_output(struct sock *sk, struct sk_buff *skb)
52 {
53 struct sk_buff *skbn;
54 unsigned char header[X25_EXT_MIN_LEN];
55 int err, frontlen, len;
56 int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT;
57 struct x25_sock *x25 = x25_sk(sk);
58 int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN :
59 X25_STD_MIN_LEN;
60 int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
61
62 if (skb->len - header_len > max_len) {
63 /* Save a copy of the Header */
64 skb_copy_from_linear_data(skb, header, header_len);
65 skb_pull(skb, header_len);
66
67 frontlen = skb_headroom(skb);
68
69 while (skb->len > 0) {
70 if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
71 noblock, &err)) == NULL){
72 if (err == -EWOULDBLOCK && noblock){
73 kfree_skb(skb);
74 return sent;
75 }
76 SOCK_DEBUG(sk, "x25_output: fragment alloc"
77 " failed, err=%d, %d bytes "
78 "sent\n", err, sent);
79 return err;
80 }
81
82 skb_reserve(skbn, frontlen);
83
84 len = max_len > skb->len ? skb->len : max_len;
85
86 /* Copy the user data */
87 skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
88 skb_pull(skb, len);
89
90 /* Duplicate the Header */
91 skb_push(skbn, header_len);
92 skb_copy_to_linear_data(skbn, header, header_len);
93
94 if (skb->len > 0) {
95 if (x25->neighbour->extended)
96 skbn->data[3] |= X25_EXT_M_BIT;
97 else
98 skbn->data[2] |= X25_STD_M_BIT;
99 }
100
101 skb_queue_tail(&sk->sk_write_queue, skbn);
102 sent += len;
103 }
104
105 kfree_skb(skb);
106 } else {
107 skb_queue_tail(&sk->sk_write_queue, skb);
108 sent = skb->len - header_len;
109 }
110 return sent;
111 }
112
113 /*
114 * This procedure is passed a buffer descriptor for an iframe. It builds
115 * the rest of the control part of the frame and then writes it out.
116 */
117 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
118 {
119 struct x25_sock *x25 = x25_sk(sk);
120
121 if (!skb)
122 return;
123
124 if (x25->neighbour->extended) {
125 skb->data[2] = (x25->vs << 1) & 0xFE;
126 skb->data[3] &= X25_EXT_M_BIT;
127 skb->data[3] |= (x25->vr << 1) & 0xFE;
128 } else {
129 skb->data[2] &= X25_STD_M_BIT;
130 skb->data[2] |= (x25->vs << 1) & 0x0E;
131 skb->data[2] |= (x25->vr << 5) & 0xE0;
132 }
133
134 x25_transmit_link(skb, x25->neighbour);
135 }
136
137 void x25_kick(struct sock *sk)
138 {
139 struct sk_buff *skb, *skbn;
140 unsigned short start, end;
141 int modulus;
142 struct x25_sock *x25 = x25_sk(sk);
143
144 if (x25->state != X25_STATE_3)
145 return;
146
147 /*
148 * Transmit interrupt data.
149 */
150 if (!x25->intflag && skb_peek(&x25->interrupt_out_queue) != NULL) {
151 x25->intflag = 1;
152 skb = skb_dequeue(&x25->interrupt_out_queue);
153 x25_transmit_link(skb, x25->neighbour);
154 }
155
156 if (x25->condition & X25_COND_PEER_RX_BUSY)
157 return;
158
159 if (!skb_peek(&sk->sk_write_queue))
160 return;
161
162 modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
163
164 start = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
165 end = (x25->va + x25->facilities.winsize_out) % modulus;
166
167 if (start == end)
168 return;
169
170 x25->vs = start;
171
172 /*
173 * Transmit data until either we're out of data to send or
174 * the window is full.
175 */
176
177 skb = skb_dequeue(&sk->sk_write_queue);
178
179 do {
180 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
181 skb_queue_head(&sk->sk_write_queue, skb);
182 break;
183 }
184
185 skb_set_owner_w(skbn, sk);
186
187 /*
188 * Transmit the frame copy.
189 */
190 x25_send_iframe(sk, skbn);
191
192 x25->vs = (x25->vs + 1) % modulus;
193
194 /*
195 * Requeue the original data frame.
196 */
197 skb_queue_tail(&x25->ack_queue, skb);
198
199 } while (x25->vs != end &&
200 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
201
202 x25->vl = x25->vr;
203 x25->condition &= ~X25_COND_ACK_PENDING;
204
205 x25_stop_timer(sk);
206 }
207
208 /*
209 * The following routines are taken from page 170 of the 7th ARRL Computer
210 * Networking Conference paper, as is the whole state machine.
211 */
212
213 void x25_enquiry_response(struct sock *sk)
214 {
215 struct x25_sock *x25 = x25_sk(sk);
216
217 if (x25->condition & X25_COND_OWN_RX_BUSY)
218 x25_write_internal(sk, X25_RNR);
219 else
220 x25_write_internal(sk, X25_RR);
221
222 x25->vl = x25->vr;
223 x25->condition &= ~X25_COND_ACK_PENDING;
224
225 x25_stop_timer(sk);
226 }
227
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