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