linux/net/x25/x25_out.c
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   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
  33static 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 */
  52int 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 */
 121static 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
 141void 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
 218void 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}
 232
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