1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * X.25 Packet Layer release 002 |
4 | * |
5 | * This is ALPHA test software. This code may break your machine, |
6 | * randomly fail to work with new releases, misbehave and/or generally |
7 | * screw up. It might even work. |
8 | * |
9 | * This code REQUIRES 2.1.15 or higher |
10 | * |
11 | * History |
12 | * X.25 001 Jonathan Naylor Started coding. |
13 | * X.25 002 Jonathan Naylor New timer architecture. |
14 | * 2000-09-04 Henner Eisen Prevented x25_output() skb leakage. |
15 | * 2000-10-27 Henner Eisen MSG_DONTWAIT for fragment allocation. |
16 | * 2000-11-10 Henner Eisen x25_send_iframe(): re-queued frames |
17 | * needed cleaned seq-number fields. |
18 | */ |
19 | |
20 | #include <linux/slab.h> |
21 | #include <linux/socket.h> |
22 | #include <linux/kernel.h> |
23 | #include <linux/string.h> |
24 | #include <linux/skbuff.h> |
25 | #include <net/sock.h> |
26 | #include <net/x25.h> |
27 | |
28 | static int x25_pacsize_to_bytes(unsigned int pacsize) |
29 | { |
30 | int bytes = 1; |
31 | |
32 | if (!pacsize) |
33 | return 128; |
34 | |
35 | while (pacsize-- > 0) |
36 | bytes *= 2; |
37 | |
38 | return bytes; |
39 | } |
40 | |
41 | /* |
42 | * This is where all X.25 information frames pass. |
43 | * |
44 | * Returns the amount of user data bytes sent on success |
45 | * or a negative error code on failure. |
46 | */ |
47 | int x25_output(struct sock *sk, struct sk_buff *skb) |
48 | { |
49 | struct sk_buff *skbn; |
50 | unsigned char [X25_EXT_MIN_LEN]; |
51 | int err, frontlen, len; |
52 | int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT; |
53 | struct x25_sock *x25 = x25_sk(sk); |
54 | int = x25->neighbour->extended ? X25_EXT_MIN_LEN : |
55 | X25_STD_MIN_LEN; |
56 | int max_len = x25_pacsize_to_bytes(pacsize: x25->facilities.pacsize_out); |
57 | |
58 | if (skb->len - header_len > max_len) { |
59 | /* Save a copy of the Header */ |
60 | skb_copy_from_linear_data(skb, to: header, len: header_len); |
61 | skb_pull(skb, len: header_len); |
62 | |
63 | frontlen = skb_headroom(skb); |
64 | |
65 | while (skb->len > 0) { |
66 | release_sock(sk); |
67 | skbn = sock_alloc_send_skb(sk, size: frontlen + max_len, |
68 | noblock, errcode: &err); |
69 | lock_sock(sk); |
70 | if (!skbn) { |
71 | if (err == -EWOULDBLOCK && noblock){ |
72 | kfree_skb(skb); |
73 | return sent; |
74 | } |
75 | SOCK_DEBUG(sk, "x25_output: fragment alloc" |
76 | " failed, err=%d, %d bytes " |
77 | "sent\n" , err, sent); |
78 | return err; |
79 | } |
80 | |
81 | skb_reserve(skb: skbn, len: frontlen); |
82 | |
83 | len = max_len > skb->len ? skb->len : max_len; |
84 | |
85 | /* Copy the user data */ |
86 | skb_copy_from_linear_data(skb, to: skb_put(skb: skbn, len), len); |
87 | skb_pull(skb, len); |
88 | |
89 | /* Duplicate the Header */ |
90 | skb_push(skb: skbn, len: header_len); |
91 | skb_copy_to_linear_data(skb: skbn, from: header, len: header_len); |
92 | |
93 | if (skb->len > 0) { |
94 | if (x25->neighbour->extended) |
95 | skbn->data[3] |= X25_EXT_M_BIT; |
96 | else |
97 | skbn->data[2] |= X25_STD_M_BIT; |
98 | } |
99 | |
100 | skb_queue_tail(list: &sk->sk_write_queue, newsk: skbn); |
101 | sent += len; |
102 | } |
103 | |
104 | kfree_skb(skb); |
105 | } else { |
106 | skb_queue_tail(list: &sk->sk_write_queue, newsk: skb); |
107 | sent = skb->len - header_len; |
108 | } |
109 | return sent; |
110 | } |
111 | |
112 | /* |
113 | * This procedure is passed a buffer descriptor for an iframe. It builds |
114 | * the rest of the control part of the frame and then writes it out. |
115 | */ |
116 | static void x25_send_iframe(struct sock *sk, struct sk_buff *skb) |
117 | { |
118 | struct x25_sock *x25 = x25_sk(sk); |
119 | |
120 | if (!skb) |
121 | return; |
122 | |
123 | if (x25->neighbour->extended) { |
124 | skb->data[2] = (x25->vs << 1) & 0xFE; |
125 | skb->data[3] &= X25_EXT_M_BIT; |
126 | skb->data[3] |= (x25->vr << 1) & 0xFE; |
127 | } else { |
128 | skb->data[2] &= X25_STD_M_BIT; |
129 | skb->data[2] |= (x25->vs << 1) & 0x0E; |
130 | skb->data[2] |= (x25->vr << 5) & 0xE0; |
131 | } |
132 | |
133 | x25_transmit_link(skb, x25->neighbour); |
134 | } |
135 | |
136 | void x25_kick(struct sock *sk) |
137 | { |
138 | struct sk_buff *skb, *skbn; |
139 | unsigned short start, end; |
140 | int modulus; |
141 | struct x25_sock *x25 = x25_sk(sk); |
142 | |
143 | if (x25->state != X25_STATE_3) |
144 | return; |
145 | |
146 | /* |
147 | * Transmit interrupt data. |
148 | */ |
149 | if (skb_peek(list_: &x25->interrupt_out_queue) != NULL && |
150 | !test_and_set_bit(X25_INTERRUPT_FLAG, addr: &x25->flags)) { |
151 | |
152 | skb = skb_dequeue(list: &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(list_: &sk->sk_write_queue)) |
160 | return; |
161 | |
162 | modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS; |
163 | |
164 | start = skb_peek(list_: &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(list: &sk->sk_write_queue); |
178 | |
179 | do { |
180 | if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) { |
181 | skb_queue_head(list: &sk->sk_write_queue, newsk: skb); |
182 | break; |
183 | } |
184 | |
185 | skb_set_owner_w(skb: skbn, sk); |
186 | |
187 | /* |
188 | * Transmit the frame copy. |
189 | */ |
190 | x25_send_iframe(sk, skb: skbn); |
191 | |
192 | x25->vs = (x25->vs + 1) % modulus; |
193 | |
194 | /* |
195 | * Requeue the original data frame. |
196 | */ |
197 | skb_queue_tail(list: &x25->ack_queue, newsk: skb); |
198 | |
199 | } while (x25->vs != end && |
200 | (skb = skb_dequeue(list: &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 | |