x25: Handle undersized/fragmented skbs
[linux-3.10.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/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                         release_sock(sk);
72                         skbn = sock_alloc_send_skb(sk, frontlen + max_len,
73                                                    noblock, &err);
74                         lock_sock(sk);
75                         if (!skbn) {
76                                 if (err == -EWOULDBLOCK && noblock){
77                                         kfree_skb(skb);
78                                         return sent;
79                                 }
80                                 SOCK_DEBUG(sk, "x25_output: fragment alloc"
81                                                " failed, err=%d, %d bytes "
82                                                "sent\n", err, sent);
83                                 return err;
84                         }
85
86                         skb_reserve(skbn, frontlen);
87
88                         len = max_len > skb->len ? skb->len : max_len;
89
90                         /* Copy the user data */
91                         skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
92                         skb_pull(skb, len);
93
94                         /* Duplicate the Header */
95                         skb_push(skbn, header_len);
96                         skb_copy_to_linear_data(skbn, header, header_len);
97
98                         if (skb->len > 0) {
99                                 if (x25->neighbour->extended)
100                                         skbn->data[3] |= X25_EXT_M_BIT;
101                                 else
102                                         skbn->data[2] |= X25_STD_M_BIT;
103                         }
104
105                         skb_queue_tail(&sk->sk_write_queue, skbn);
106                         sent += len;
107                 }
108
109                 kfree_skb(skb);
110         } else {
111                 skb_queue_tail(&sk->sk_write_queue, skb);
112                 sent = skb->len - header_len;
113         }
114         return sent;
115 }
116
117 /*
118  *      This procedure is passed a buffer descriptor for an iframe. It builds
119  *      the rest of the control part of the frame and then writes it out.
120  */
121 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
122 {
123         struct x25_sock *x25 = x25_sk(sk);
124
125         if (!skb)
126                 return;
127
128         if (x25->neighbour->extended) {
129                 skb->data[2]  = (x25->vs << 1) & 0xFE;
130                 skb->data[3] &= X25_EXT_M_BIT;
131                 skb->data[3] |= (x25->vr << 1) & 0xFE;
132         } else {
133                 skb->data[2] &= X25_STD_M_BIT;
134                 skb->data[2] |= (x25->vs << 1) & 0x0E;
135                 skb->data[2] |= (x25->vr << 5) & 0xE0;
136         }
137
138         x25_transmit_link(skb, x25->neighbour);
139 }
140
141 void x25_kick(struct sock *sk)
142 {
143         struct sk_buff *skb, *skbn;
144         unsigned short start, end;
145         int modulus;
146         struct x25_sock *x25 = x25_sk(sk);
147
148         if (x25->state != X25_STATE_3)
149                 return;
150
151         /*
152          *      Transmit interrupt data.
153          */
154         if (skb_peek(&x25->interrupt_out_queue) != NULL &&
155                 !test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
156
157                 skb = skb_dequeue(&x25->interrupt_out_queue);
158                 x25_transmit_link(skb, x25->neighbour);
159         }
160
161         if (x25->condition & X25_COND_PEER_RX_BUSY)
162                 return;
163
164         if (!skb_peek(&sk->sk_write_queue))
165                 return;
166
167         modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
168
169         start   = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
170         end     = (x25->va + x25->facilities.winsize_out) % modulus;
171
172         if (start == end)
173                 return;
174
175         x25->vs = start;
176
177         /*
178          * Transmit data until either we're out of data to send or
179          * the window is full.
180          */
181
182         skb = skb_dequeue(&sk->sk_write_queue);
183
184         do {
185                 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
186                         skb_queue_head(&sk->sk_write_queue, skb);
187                         break;
188                 }
189
190                 skb_set_owner_w(skbn, sk);
191
192                 /*
193                  * Transmit the frame copy.
194                  */
195                 x25_send_iframe(sk, skbn);
196
197                 x25->vs = (x25->vs + 1) % modulus;
198
199                 /*
200                  * Requeue the original data frame.
201                  */
202                 skb_queue_tail(&x25->ack_queue, skb);
203
204         } while (x25->vs != end &&
205                  (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
206
207         x25->vl         = x25->vr;
208         x25->condition &= ~X25_COND_ACK_PENDING;
209
210         x25_stop_timer(sk);
211 }
212
213 /*
214  * The following routines are taken from page 170 of the 7th ARRL Computer
215  * Networking Conference paper, as is the whole state machine.
216  */
217
218 void x25_enquiry_response(struct sock *sk)
219 {
220         struct x25_sock *x25 = x25_sk(sk);
221
222         if (x25->condition & X25_COND_OWN_RX_BUSY)
223                 x25_write_internal(sk, X25_RNR);
224         else
225                 x25_write_internal(sk, X25_RR);
226
227         x25->vl         = x25->vr;
228         x25->condition &= ~X25_COND_ACK_PENDING;
229
230         x25_stop_timer(sk);
231 }