net: '&' redux
[linux-2.6.git] / net / x25 / x25_out.c
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 }