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/errno.h>
  26 #include <linux/types.h>
  27 #include <linux/socket.h>
  28 #include <linux/in.h>
  29 #include <linux/kernel.h>
  30 #include <linux/sched.h>
  31 #include <linux/timer.h>
  32 #include <linux/string.h>
  33 #include <linux/sockios.h>
  34 #include <linux/net.h>
  35 #include <linux/inet.h>
  36 #include <linux/netdevice.h>
  37 #include <linux/skbuff.h>
  38 #include <net/sock.h>
  39 #include <asm/system.h>
  40 #include <linux/fcntl.h>
  41 #include <linux/mm.h>
  42 #include <linux/interrupt.h>
  43 #include <net/x25.h>
  44
  45 static int x25_pacsize_to_bytes(unsigned int pacsize)
  46 {
  47         int bytes = 1;
  48
  49         if (!pacsize)
  50                 return 128;
  51
  52         while (pacsize-- > 0)
  53                 bytes *= 2;
  54
  55         return bytes;
  56 }
  57
  58 /*
  59  *      This is where all X.25 information frames pass.
  60  *
  61  *      Returns the amount of user data bytes sent on success
  62  *      or a negative error code on failure.
  63  */
  64 int x25_output(struct sock *sk, struct sk_buff *skb)
  65 {
  66         struct sk_buff *skbn;
  67         unsigned char header[X25_EXT_MIN_LEN];
  68         int err, frontlen, len;
  69         int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT;
  70         struct x25_opt *x25 = x25_sk(sk);
  71         int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN :
  72                                                     X25_STD_MIN_LEN;
  73         int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
  74
  75         if (skb->len - header_len > max_len) {
  76                 /* Save a copy of the Header */
  77                 memcpy(header, skb->data, header_len);
  78                 skb_pull(skb, header_len);
  79
  80                 frontlen = skb_headroom(skb);
  81
  82                 while (skb->len > 0) {
  83                         if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
  84                                                         noblock, &err)) == NULL){
  85                                 if (err == -EWOULDBLOCK && noblock){
  86                                         kfree_skb(skb);
  87                                         return sent;
  88                                 }
  89                                 SOCK_DEBUG(sk, "x25_output: fragment alloc"
  90                                                " failed, err=%d, %d bytes "
  91                                                "sent\n", err, sent);
  92                                 return err;
  93                         }
  94
  95                         skb_reserve(skbn, frontlen);
  96
  97                         len = max_len > skb->len ? skb->len : max_len;
  98
  99                         /* Copy the user data */
 100                         memcpy(skb_put(skbn, len), skb->data, len);
 101                         skb_pull(skb, len);
 102
 103                         /* Duplicate the Header */
 104                         skb_push(skbn, header_len);
 105                         memcpy(skbn->data, header, header_len);
 106
 107                         if (skb->len > 0) {
 108                                 if (x25->neighbour->extended)
 109                                         skbn->data[3] |= X25_EXT_M_BIT;
 110                                 else
 111                                         skbn->data[2] |= X25_STD_M_BIT;
 112                         }
 113
 114                         skb_queue_tail(&sk->sk_write_queue, skbn);
 115                         sent += len;
 116                 }
 117
 118                 kfree_skb(skb);
 119         } else {
 120                 skb_queue_tail(&sk->sk_write_queue, skb);
 121                 sent = skb->len - header_len;
 122         }
 123         return sent;
 124 }
 125
 126 /*
 127  *      This procedure is passed a buffer descriptor for an iframe. It builds
 128  *      the rest of the control part of the frame and then writes it out.
 129  */
 130 static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
 131 {
 132         struct x25_opt *x25 = x25_sk(sk);
 133
 134         if (!skb)
 135                 return;
 136
 137         if (x25->neighbour->extended) {
 138                 skb->data[2]  = (x25->vs << 1) & 0xFE;
 139                 skb->data[3] &= X25_EXT_M_BIT;
 140                 skb->data[3] |= (x25->vr << 1) & 0xFE;
 141         } else {
 142                 skb->data[2] &= X25_STD_M_BIT;
 143                 skb->data[2] |= (x25->vs << 1) & 0x0E;
 144                 skb->data[2] |= (x25->vr << 5) & 0xE0;
 145         }
 146
 147         x25_transmit_link(skb, x25->neighbour);
 148 }
 149
 150 void x25_kick(struct sock *sk)
 151 {
 152         struct sk_buff *skb, *skbn;
 153         unsigned short start, end;
 154         int modulus;
 155         struct x25_opt *x25 = x25_sk(sk);
 156
 157         if (x25->state != X25_STATE_3)
 158                 return;
 159
 160         /*
 161          *      Transmit interrupt data.
 162          */
 163         if (!x25->intflag && skb_peek(&x25->interrupt_out_queue) != NULL) {
 164                 x25->intflag = 1;
 165                 skb = skb_dequeue(&x25->interrupt_out_queue);
 166                 x25_transmit_link(skb, x25->neighbour);
 167         }
 168
 169         if (x25->condition & X25_COND_PEER_RX_BUSY)
 170                 return;
 171
 172         if (!skb_peek(&sk->sk_write_queue))
 173                 return;
 174
 175         modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
 176
 177         start   = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
 178         end     = (x25->va + x25->facilities.winsize_out) % modulus;
 179
 180         if (start == end)
 181                 return;
 182
 183         x25->vs = start;
 184
 185         /*
 186          * Transmit data until either we're out of data to send or
 187          * the window is full.
 188          */
 189
 190         skb = skb_dequeue(&sk->sk_write_queue);
 191
 192         do {
 193                 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
 194                         skb_queue_head(&sk->sk_write_queue, skb);
 195                         break;
 196                 }
 197
 198                 skb_set_owner_w(skbn, sk);
 199
 200                 /*
 201                  * Transmit the frame copy.
 202                  */
 203                 x25_send_iframe(sk, skbn);
 204
 205                 x25->vs = (x25->vs + 1) % modulus;
 206
 207                 /*
 208                  * Requeue the original data frame.
 209                  */
 210                 skb_queue_tail(&x25->ack_queue, skb);
 211
 212         } while (x25->vs != end &&
 213                  (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
 214
 215         x25->vl         = x25->vr;
 216         x25->condition &= ~X25_COND_ACK_PENDING;
 217
 218         x25_stop_timer(sk);
 219 }
 220
 221 /*
 222  * The following routines are taken from page 170 of the 7th ARRL Computer
 223  * Networking Conference paper, as is the whole state machine.
 224  */
 225
 226 void x25_enquiry_response(struct sock *sk)
 227 {
 228         struct x25_opt *x25 = x25_sk(sk);
 229
 230         if (x25->condition & X25_COND_OWN_RX_BUSY)
 231                 x25_write_internal(sk, X25_RNR);
 232         else
 233                 x25_write_internal(sk, X25_RR);
 234
 235         x25->vl         = x25->vr;
 236         x25->condition &= ~X25_COND_ACK_PENDING;
 237
 238         x25_stop_timer(sk);
 239 }