net/lapb/lapb_subr.c

   1 /*
   2  *      LAPB release 002
   3  *
   4  *      This code REQUIRES 2.1.15 or higher/ NET3.038
   5  *
   6  *      This module:
   7  *              This module is free software; you can redistribute it and/or
   8  *              modify it under the terms of the GNU General Public License
   9  *              as published by the Free Software Foundation; either version
  10  *              2 of the License, or (at your option) any later version.
  11  *
  12  *      History
  13  *      LAPB 001        Jonathan Naylor Started Coding
  14  */
  15
  16 #include <linux/errno.h>
  17 #include <linux/types.h>
  18 #include <linux/socket.h>
  19 #include <linux/in.h>
  20 #include <linux/kernel.h>
  21 #include <linux/timer.h>
  22 #include <linux/string.h>
  23 #include <linux/sockios.h>
  24 #include <linux/net.h>
  25 #include <linux/inet.h>
  26 #include <linux/skbuff.h>
  27 #include <net/sock.h>
  28 #include <asm/uaccess.h>
  29 #include <asm/system.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/mm.h>
  32 #include <linux/interrupt.h>
  33 #include <net/lapb.h>
  34
  35 /*
  36  *      This routine purges all the queues of frames.
  37  */
  38 void lapb_clear_queues(struct lapb_cb *lapb)
  39 {
  40         skb_queue_purge(&lapb->write_queue);
  41         skb_queue_purge(&lapb->ack_queue);
  42 }
  43
  44 /*
  45  * This routine purges the input queue of those frames that have been
  46  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  47  * SDL diagram.
  48  */
  49 void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
  50 {
  51         struct sk_buff *skb;
  52         int modulus;
  53
  54         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  55
  56         /*
  57          * Remove all the ack-ed frames from the ack queue.
  58          */
  59         if (lapb->va != nr)
  60                 while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
  61                         skb = skb_dequeue(&lapb->ack_queue);
  62                         kfree_skb(skb);
  63                         lapb->va = (lapb->va + 1) % modulus;
  64                 }
  65 }
  66
  67 void lapb_requeue_frames(struct lapb_cb *lapb)
  68 {
  69         struct sk_buff *skb, *skb_prev = NULL;
  70
  71         /*
  72          * Requeue all the un-ack-ed frames on the output queue to be picked
  73          * up by lapb_kick called from the timer. This arrangement handles the
  74          * possibility of an empty output queue.
  75          */
  76         while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
  77                 if (!skb_prev)
  78                         skb_queue_head(&lapb->write_queue, skb);
  79                 else
  80                         skb_append(skb_prev, skb, &lapb->write_queue);
  81                 skb_prev = skb;
  82         }
  83 }
  84
  85 /*
  86  *      Validate that the value of nr is between va and vs. Return true or
  87  *      false for testing.
  88  */
  89 int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
  90 {
  91         unsigned short vc = lapb->va;
  92         int modulus;
  93
  94         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  95
  96         while (vc != lapb->vs) {
  97                 if (nr == vc)
  98                         return 1;
  99                 vc = (vc + 1) % modulus;
 100         }
 101
 102         return nr == lapb->vs;
 103 }
 104
 105 /*
 106  *      This routine is the centralised routine for parsing the control
 107  *      information for the different frame formats.
 108  */
 109 int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
 110                 struct lapb_frame *frame)
 111 {
 112         frame->type = LAPB_ILLEGAL;
 113
 114 #if LAPB_DEBUG > 2
 115         printk(KERN_DEBUG "lapb: (%p) S%d RX %02X %02X %02X\n",
 116                lapb->dev, lapb->state,
 117                skb->data[0], skb->data[1], skb->data[2]);
 118 #endif
 119
 120         /* We always need to look at 2 bytes, sometimes we need
 121          * to look at 3 and those cases are handled below.
 122          */
 123         if (!pskb_may_pull(skb, 2))
 124                 return -1;
 125
 126         if (lapb->mode & LAPB_MLP) {
 127                 if (lapb->mode & LAPB_DCE) {
 128                         if (skb->data[0] == LAPB_ADDR_D)
 129                                 frame->cr = LAPB_COMMAND;
 130                         if (skb->data[0] == LAPB_ADDR_C)
 131                                 frame->cr = LAPB_RESPONSE;
 132                 } else {
 133                         if (skb->data[0] == LAPB_ADDR_C)
 134                                 frame->cr = LAPB_COMMAND;
 135                         if (skb->data[0] == LAPB_ADDR_D)
 136                                 frame->cr = LAPB_RESPONSE;
 137                 }
 138         } else {
 139                 if (lapb->mode & LAPB_DCE) {
 140                         if (skb->data[0] == LAPB_ADDR_B)
 141                                 frame->cr = LAPB_COMMAND;
 142                         if (skb->data[0] == LAPB_ADDR_A)
 143                                 frame->cr = LAPB_RESPONSE;
 144                 } else {
 145                         if (skb->data[0] == LAPB_ADDR_A)
 146                                 frame->cr = LAPB_COMMAND;
 147                         if (skb->data[0] == LAPB_ADDR_B)
 148                                 frame->cr = LAPB_RESPONSE;
 149                 }
 150         }
 151
 152         skb_pull(skb, 1);
 153
 154         if (lapb->mode & LAPB_EXTENDED) {
 155                 if (!(skb->data[0] & LAPB_S)) {
 156                         if (!pskb_may_pull(skb, 2))
 157                                 return -1;
 158                         /*
 159                          * I frame - carries NR/NS/PF
 160                          */
 161                         frame->type       = LAPB_I;
 162                         frame->ns         = (skb->data[0] >> 1) & 0x7F;
 163                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 164                         frame->pf         = skb->data[1] & LAPB_EPF;
 165                         frame->control[0] = skb->data[0];
 166                         frame->control[1] = skb->data[1];
 167                         skb_pull(skb, 2);
 168                 } else if ((skb->data[0] & LAPB_U) == 1) {
 169                         if (!pskb_may_pull(skb, 2))
 170                                 return -1;
 171                         /*
 172                          * S frame - take out PF/NR
 173                          */
 174                         frame->type       = skb->data[0] & 0x0F;
 175                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 176                         frame->pf         = skb->data[1] & LAPB_EPF;
 177                         frame->control[0] = skb->data[0];
 178                         frame->control[1] = skb->data[1];
 179                         skb_pull(skb, 2);
 180                 } else if ((skb->data[0] & LAPB_U) == 3) {
 181                         /*
 182                          * U frame - take out PF
 183                          */
 184                         frame->type       = skb->data[0] & ~LAPB_SPF;
 185                         frame->pf         = skb->data[0] & LAPB_SPF;
 186                         frame->control[0] = skb->data[0];
 187                         frame->control[1] = 0x00;
 188                         skb_pull(skb, 1);
 189                 }
 190         } else {
 191                 if (!(skb->data[0] & LAPB_S)) {
 192                         /*
 193                          * I frame - carries NR/NS/PF
 194                          */
 195                         frame->type = LAPB_I;
 196                         frame->ns   = (skb->data[0] >> 1) & 0x07;
 197                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 198                         frame->pf   = skb->data[0] & LAPB_SPF;
 199                 } else if ((skb->data[0] & LAPB_U) == 1) {
 200                         /*
 201                          * S frame - take out PF/NR
 202                          */
 203                         frame->type = skb->data[0] & 0x0F;
 204                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 205                         frame->pf   = skb->data[0] & LAPB_SPF;
 206                 } else if ((skb->data[0] & LAPB_U) == 3) {
 207                         /*
 208                          * U frame - take out PF
 209                          */
 210                         frame->type = skb->data[0] & ~LAPB_SPF;
 211                         frame->pf   = skb->data[0] & LAPB_SPF;
 212                 }
 213
 214                 frame->control[0] = skb->data[0];
 215
 216                 skb_pull(skb, 1);
 217         }
 218
 219         return 0;
 220 }
 221
 222 /*
 223  *      This routine is called when the HDLC layer internally  generates a
 224  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 225  *      Only supervisory or unnumbered frames are processed, FRMRs are handled
 226  *      by lapb_transmit_frmr below.
 227  */
 228 void lapb_send_control(struct lapb_cb *lapb, int frametype,
 229                        int poll_bit, int type)
 230 {
 231         struct sk_buff *skb;
 232         unsigned char  *dptr;
 233
 234         if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
 235                 return;
 236
 237         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 238
 239         if (lapb->mode & LAPB_EXTENDED) {
 240                 if ((frametype & LAPB_U) == LAPB_U) {
 241                         dptr   = skb_put(skb, 1);
 242                         *dptr  = frametype;
 243                         *dptr |= poll_bit ? LAPB_SPF : 0;
 244                 } else {
 245                         dptr     = skb_put(skb, 2);
 246                         dptr[0]  = frametype;
 247                         dptr[1]  = (lapb->vr << 1);
 248                         dptr[1] |= poll_bit ? LAPB_EPF : 0;
 249                 }
 250         } else {
 251                 dptr   = skb_put(skb, 1);
 252                 *dptr  = frametype;
 253                 *dptr |= poll_bit ? LAPB_SPF : 0;
 254                 if ((frametype & LAPB_U) == LAPB_S)     /* S frames carry NR */
 255                         *dptr |= (lapb->vr << 5);
 256         }
 257
 258         lapb_transmit_buffer(lapb, skb, type);
 259 }
 260
 261 /*
 262  *      This routine generates FRMRs based on information previously stored in
 263  *      the LAPB control block.
 264  */
 265 void lapb_transmit_frmr(struct lapb_cb *lapb)
 266 {
 267         struct sk_buff *skb;
 268         unsigned char  *dptr;
 269
 270         if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
 271                 return;
 272
 273         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 274
 275         if (lapb->mode & LAPB_EXTENDED) {
 276                 dptr    = skb_put(skb, 6);
 277                 *dptr++ = LAPB_FRMR;
 278                 *dptr++ = lapb->frmr_data.control[0];
 279                 *dptr++ = lapb->frmr_data.control[1];
 280                 *dptr++ = (lapb->vs << 1) & 0xFE;
 281                 *dptr   = (lapb->vr << 1) & 0xFE;
 282                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 283                         *dptr |= 0x01;
 284                 dptr++;
 285                 *dptr++ = lapb->frmr_type;
 286
 287 #if LAPB_DEBUG > 1
 288         printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
 289                lapb->dev, lapb->state,
 290                skb->data[1], skb->data[2], skb->data[3],
 291                skb->data[4], skb->data[5]);
 292 #endif
 293         } else {
 294                 dptr    = skb_put(skb, 4);
 295                 *dptr++ = LAPB_FRMR;
 296                 *dptr++ = lapb->frmr_data.control[0];
 297                 *dptr   = (lapb->vs << 1) & 0x0E;
 298                 *dptr  |= (lapb->vr << 5) & 0xE0;
 299                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 300                         *dptr |= 0x10;
 301                 dptr++;
 302                 *dptr++ = lapb->frmr_type;
 303
 304 #if LAPB_DEBUG > 1
 305         printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X\n",
 306                lapb->dev, lapb->state, skb->data[1],
 307                skb->data[2], skb->data[3]);
 308 #endif
 309         }
 310
 311         lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
 312 }