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 <linux/slab.h>
  28 #include <net/sock.h>
  29 #include <asm/uaccess.h>
  30 #include <asm/system.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/mm.h>
  33 #include <linux/interrupt.h>
  34 #include <net/lapb.h>
  35
  36 /*
  37  *      This routine purges all the queues of frames.
  38  */
  39 void lapb_clear_queues(struct lapb_cb *lapb)
  40 {
  41         skb_queue_purge(&lapb->write_queue);
  42         skb_queue_purge(&lapb->ack_queue);
  43 }
  44
  45 /*
  46  * This routine purges the input queue of those frames that have been
  47  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  48  * SDL diagram.
  49  */
  50 void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
  51 {
  52         struct sk_buff *skb;
  53         int modulus;
  54
  55         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  56
  57         /*
  58          * Remove all the ack-ed frames from the ack queue.
  59          */
  60         if (lapb->va != nr)
  61                 while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
  62                         skb = skb_dequeue(&lapb->ack_queue);
  63                         kfree_skb(skb);
  64                         lapb->va = (lapb->va + 1) % modulus;
  65                 }
  66 }
  67
  68 void lapb_requeue_frames(struct lapb_cb *lapb)
  69 {
  70         struct sk_buff *skb, *skb_prev = NULL;
  71
  72         /*
  73          * Requeue all the un-ack-ed frames on the output queue to be picked
  74          * up by lapb_kick called from the timer. This arrangement handles the
  75          * possibility of an empty output queue.
  76          */
  77         while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
  78                 if (!skb_prev)
  79                         skb_queue_head(&lapb->write_queue, skb);
  80                 else
  81                         skb_append(skb_prev, skb, &lapb->write_queue);
  82                 skb_prev = skb;
  83         }
  84 }
  85
  86 /*
  87  *      Validate that the value of nr is between va and vs. Return true or
  88  *      false for testing.
  89  */
  90 int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
  91 {
  92         unsigned short vc = lapb->va;
  93         int modulus;
  94
  95         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  96
  97         while (vc != lapb->vs) {
  98                 if (nr == vc)
  99                         return 1;
 100                 vc = (vc + 1) % modulus;
 101         }
 102
 103         return nr == lapb->vs;
 104 }
 105
 106 /*
 107  *      This routine is the centralised routine for parsing the control
 108  *      information for the different frame formats.
 109  */
 110 int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
 111                 struct lapb_frame *frame)
 112 {
 113         frame->type = LAPB_ILLEGAL;
 114
 115 #if LAPB_DEBUG > 2
 116         printk(KERN_DEBUG "lapb: (%p) S%d RX %02X %02X %02X\n",
 117                lapb->dev, lapb->state,
 118                skb->data[0], skb->data[1], skb->data[2]);
 119 #endif
 120
 121         /* We always need to look at 2 bytes, sometimes we need
 122          * to look at 3 and those cases are handled below.
 123          */
 124         if (!pskb_may_pull(skb, 2))
 125                 return -1;
 126
 127         if (lapb->mode & LAPB_MLP) {
 128                 if (lapb->mode & LAPB_DCE) {
 129                         if (skb->data[0] == LAPB_ADDR_D)
 130                                 frame->cr = LAPB_COMMAND;
 131                         if (skb->data[0] == LAPB_ADDR_C)
 132                                 frame->cr = LAPB_RESPONSE;
 133                 } else {
 134                         if (skb->data[0] == LAPB_ADDR_C)
 135                                 frame->cr = LAPB_COMMAND;
 136                         if (skb->data[0] == LAPB_ADDR_D)
 137                                 frame->cr = LAPB_RESPONSE;
 138                 }
 139         } else {
 140                 if (lapb->mode & LAPB_DCE) {
 141                         if (skb->data[0] == LAPB_ADDR_B)
 142                                 frame->cr = LAPB_COMMAND;
 143                         if (skb->data[0] == LAPB_ADDR_A)
 144                                 frame->cr = LAPB_RESPONSE;
 145                 } else {
 146                         if (skb->data[0] == LAPB_ADDR_A)
 147                                 frame->cr = LAPB_COMMAND;
 148                         if (skb->data[0] == LAPB_ADDR_B)
 149                                 frame->cr = LAPB_RESPONSE;
 150                 }
 151         }
 152
 153         skb_pull(skb, 1);
 154
 155         if (lapb->mode & LAPB_EXTENDED) {
 156                 if (!(skb->data[0] & LAPB_S)) {
 157                         if (!pskb_may_pull(skb, 2))
 158                                 return -1;
 159                         /*
 160                          * I frame - carries NR/NS/PF
 161                          */
 162                         frame->type       = LAPB_I;
 163                         frame->ns         = (skb->data[0] >> 1) & 0x7F;
 164                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 165                         frame->pf         = skb->data[1] & LAPB_EPF;
 166                         frame->control[0] = skb->data[0];
 167                         frame->control[1] = skb->data[1];
 168                         skb_pull(skb, 2);
 169                 } else if ((skb->data[0] & LAPB_U) == 1) {
 170                         if (!pskb_may_pull(skb, 2))
 171                                 return -1;
 172                         /*
 173                          * S frame - take out PF/NR
 174                          */
 175                         frame->type       = skb->data[0] & 0x0F;
 176                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 177                         frame->pf         = skb->data[1] & LAPB_EPF;
 178                         frame->control[0] = skb->data[0];
 179                         frame->control[1] = skb->data[1];
 180                         skb_pull(skb, 2);
 181                 } else if ((skb->data[0] & LAPB_U) == 3) {
 182                         /*
 183                          * U frame - take out PF
 184                          */
 185                         frame->type       = skb->data[0] & ~LAPB_SPF;
 186                         frame->pf         = skb->data[0] & LAPB_SPF;
 187                         frame->control[0] = skb->data[0];
 188                         frame->control[1] = 0x00;
 189                         skb_pull(skb, 1);
 190                 }
 191         } else {
 192                 if (!(skb->data[0] & LAPB_S)) {
 193                         /*
 194                          * I frame - carries NR/NS/PF
 195                          */
 196                         frame->type = LAPB_I;
 197                         frame->ns   = (skb->data[0] >> 1) & 0x07;
 198                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 199                         frame->pf   = skb->data[0] & LAPB_SPF;
 200                 } else if ((skb->data[0] & LAPB_U) == 1) {
 201                         /*
 202                          * S frame - take out PF/NR
 203                          */
 204                         frame->type = skb->data[0] & 0x0F;
 205                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 206                         frame->pf   = skb->data[0] & LAPB_SPF;
 207                 } else if ((skb->data[0] & LAPB_U) == 3) {
 208                         /*
 209                          * U frame - take out PF
 210                          */
 211                         frame->type = skb->data[0] & ~LAPB_SPF;
 212                         frame->pf   = skb->data[0] & LAPB_SPF;
 213                 }
 214
 215                 frame->control[0] = skb->data[0];
 216
 217                 skb_pull(skb, 1);
 218         }
 219
 220         return 0;
 221 }
 222
 223 /*
 224  *      This routine is called when the HDLC layer internally  generates a
 225  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 226  *      Only supervisory or unnumbered frames are processed, FRMRs are handled
 227  *      by lapb_transmit_frmr below.
 228  */
 229 void lapb_send_control(struct lapb_cb *lapb, int frametype,
 230                        int poll_bit, int type)
 231 {
 232         struct sk_buff *skb;
 233         unsigned char  *dptr;
 234
 235         if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
 236                 return;
 237
 238         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 239
 240         if (lapb->mode & LAPB_EXTENDED) {
 241                 if ((frametype & LAPB_U) == LAPB_U) {
 242                         dptr   = skb_put(skb, 1);
 243                         *dptr  = frametype;
 244                         *dptr |= poll_bit ? LAPB_SPF : 0;
 245                 } else {
 246                         dptr     = skb_put(skb, 2);
 247                         dptr[0]  = frametype;
 248                         dptr[1]  = (lapb->vr << 1);
 249                         dptr[1] |= poll_bit ? LAPB_EPF : 0;
 250                 }
 251         } else {
 252                 dptr   = skb_put(skb, 1);
 253                 *dptr  = frametype;
 254                 *dptr |= poll_bit ? LAPB_SPF : 0;
 255                 if ((frametype & LAPB_U) == LAPB_S)     /* S frames carry NR */
 256                         *dptr |= (lapb->vr << 5);
 257         }
 258
 259         lapb_transmit_buffer(lapb, skb, type);
 260 }
 261
 262 /*
 263  *      This routine generates FRMRs based on information previously stored in
 264  *      the LAPB control block.
 265  */
 266 void lapb_transmit_frmr(struct lapb_cb *lapb)
 267 {
 268         struct sk_buff *skb;
 269         unsigned char  *dptr;
 270
 271         if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
 272                 return;
 273
 274         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 275
 276         if (lapb->mode & LAPB_EXTENDED) {
 277                 dptr    = skb_put(skb, 6);
 278                 *dptr++ = LAPB_FRMR;
 279                 *dptr++ = lapb->frmr_data.control[0];
 280                 *dptr++ = lapb->frmr_data.control[1];
 281                 *dptr++ = (lapb->vs << 1) & 0xFE;
 282                 *dptr   = (lapb->vr << 1) & 0xFE;
 283                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 284                         *dptr |= 0x01;
 285                 dptr++;
 286                 *dptr++ = lapb->frmr_type;
 287
 288 #if LAPB_DEBUG > 1
 289         printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
 290                lapb->dev, lapb->state,
 291                skb->data[1], skb->data[2], skb->data[3],
 292                skb->data[4], skb->data[5]);
 293 #endif
 294         } else {
 295                 dptr    = skb_put(skb, 4);
 296                 *dptr++ = LAPB_FRMR;
 297                 *dptr++ = lapb->frmr_data.control[0];
 298                 *dptr   = (lapb->vs << 1) & 0x0E;
 299                 *dptr  |= (lapb->vr << 5) & 0xE0;
 300                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 301                         *dptr |= 0x10;
 302                 dptr++;
 303                 *dptr++ = lapb->frmr_type;
 304
 305 #if LAPB_DEBUG > 1
 306         printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X\n",
 307                lapb->dev, lapb->state, skb->data[1],
 308                skb->data[2], skb->data[3]);
 309 #endif
 310         }
 311
 312         lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
 313 }