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