xref: /openbmc/linux/net/x25/x25_out.c (revision 4800cd83)
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 
33 static 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  */
52 int 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 			if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
72 							noblock, &err)) == NULL){
73 				if (err == -EWOULDBLOCK && noblock){
74 					kfree_skb(skb);
75 					return sent;
76 				}
77 				SOCK_DEBUG(sk, "x25_output: fragment alloc"
78 					       " failed, err=%d, %d bytes "
79 					       "sent\n", err, sent);
80 				return err;
81 			}
82 
83 			skb_reserve(skbn, frontlen);
84 
85 			len = max_len > skb->len ? skb->len : max_len;
86 
87 			/* Copy the user data */
88 			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
89 			skb_pull(skb, len);
90 
91 			/* Duplicate the Header */
92 			skb_push(skbn, header_len);
93 			skb_copy_to_linear_data(skbn, header, header_len);
94 
95 			if (skb->len > 0) {
96 				if (x25->neighbour->extended)
97 					skbn->data[3] |= X25_EXT_M_BIT;
98 				else
99 					skbn->data[2] |= X25_STD_M_BIT;
100 			}
101 
102 			skb_queue_tail(&sk->sk_write_queue, skbn);
103 			sent += len;
104 		}
105 
106 		kfree_skb(skb);
107 	} else {
108 		skb_queue_tail(&sk->sk_write_queue, skb);
109 		sent = skb->len - header_len;
110 	}
111 	return sent;
112 }
113 
114 /*
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.
117  */
118 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
119 {
120 	struct x25_sock *x25 = x25_sk(sk);
121 
122 	if (!skb)
123 		return;
124 
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;
129 	} else {
130 		skb->data[2] &= X25_STD_M_BIT;
131 		skb->data[2] |= (x25->vs << 1) & 0x0E;
132 		skb->data[2] |= (x25->vr << 5) & 0xE0;
133 	}
134 
135 	x25_transmit_link(skb, x25->neighbour);
136 }
137 
138 void x25_kick(struct sock *sk)
139 {
140 	struct sk_buff *skb, *skbn;
141 	unsigned short start, end;
142 	int modulus;
143 	struct x25_sock *x25 = x25_sk(sk);
144 
145 	if (x25->state != X25_STATE_3)
146 		return;
147 
148 	/*
149 	 *	Transmit interrupt data.
150 	 */
151 	if (skb_peek(&x25->interrupt_out_queue) != NULL &&
152 		!test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
153 
154 		skb = skb_dequeue(&x25->interrupt_out_queue);
155 		x25_transmit_link(skb, x25->neighbour);
156 	}
157 
158 	if (x25->condition & X25_COND_PEER_RX_BUSY)
159 		return;
160 
161 	if (!skb_peek(&sk->sk_write_queue))
162 		return;
163 
164 	modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
165 
166 	start   = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
167 	end     = (x25->va + x25->facilities.winsize_out) % modulus;
168 
169 	if (start == end)
170 		return;
171 
172 	x25->vs = start;
173 
174 	/*
175 	 * Transmit data until either we're out of data to send or
176 	 * the window is full.
177 	 */
178 
179 	skb = skb_dequeue(&sk->sk_write_queue);
180 
181 	do {
182 		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
183 			skb_queue_head(&sk->sk_write_queue, skb);
184 			break;
185 		}
186 
187 		skb_set_owner_w(skbn, sk);
188 
189 		/*
190 		 * Transmit the frame copy.
191 		 */
192 		x25_send_iframe(sk, skbn);
193 
194 		x25->vs = (x25->vs + 1) % modulus;
195 
196 		/*
197 		 * Requeue the original data frame.
198 		 */
199 		skb_queue_tail(&x25->ack_queue, skb);
200 
201 	} while (x25->vs != end &&
202 		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
203 
204 	x25->vl         = x25->vr;
205 	x25->condition &= ~X25_COND_ACK_PENDING;
206 
207 	x25_stop_timer(sk);
208 }
209 
210 /*
211  * The following routines are taken from page 170 of the 7th ARRL Computer
212  * Networking Conference paper, as is the whole state machine.
213  */
214 
215 void x25_enquiry_response(struct sock *sk)
216 {
217 	struct x25_sock *x25 = x25_sk(sk);
218 
219 	if (x25->condition & X25_COND_OWN_RX_BUSY)
220 		x25_write_internal(sk, X25_RNR);
221 	else
222 		x25_write_internal(sk, X25_RR);
223 
224 	x25->vl         = x25->vr;
225 	x25->condition &= ~X25_COND_ACK_PENDING;
226 
227 	x25_stop_timer(sk);
228 }
229