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 }