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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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