net/lapb/lapb_subr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      LAPB release 002
   4  *
   5  *      This code REQUIRES 2.1.15 or higher/ NET3.038
   6  *
   7  *      History
   8  *      LAPB 001        Jonathan Naylor Started Coding
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/errno.h>
  14 #include <linux/types.h>
  15 #include <linux/socket.h>
  16 #include <linux/in.h>
  17 #include <linux/kernel.h>
  18 #include <linux/timer.h>
  19 #include <linux/string.h>
  20 #include <linux/sockios.h>
  21 #include <linux/net.h>
  22 #include <linux/inet.h>
  23 #include <linux/skbuff.h>
  24 #include <linux/slab.h>
  25 #include <net/sock.h>
  26 #include <linux/uaccess.h>
  27 #include <linux/fcntl.h>
  28 #include <linux/mm.h>
  29 #include <linux/interrupt.h>
  30 #include <net/lapb.h>
  31
  32 /*
  33  *      This routine purges all the queues of frames.
  34  */
  35 void lapb_clear_queues(struct lapb_cb *lapb)
  36 {
  37         skb_queue_purge(&lapb->write_queue);
  38         skb_queue_purge(&lapb->ack_queue);
  39 }
  40
  41 /*
  42  * This routine purges the input queue of those frames that have been
  43  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  44  * SDL diagram.
  45  */
  46 void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
  47 {
  48         struct sk_buff *skb;
  49         int modulus;
  50
  51         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  52
  53         /*
  54          * Remove all the ack-ed frames from the ack queue.
  55          */
  56         if (lapb->va != nr)
  57                 while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
  58                         skb = skb_dequeue(&lapb->ack_queue);
  59                         kfree_skb(skb);
  60                         lapb->va = (lapb->va + 1) % modulus;
  61                 }
  62 }
  63
  64 void lapb_requeue_frames(struct lapb_cb *lapb)
  65 {
  66         struct sk_buff *skb, *skb_prev = NULL;
  67
  68         /*
  69          * Requeue all the un-ack-ed frames on the output queue to be picked
  70          * up by lapb_kick called from the timer. This arrangement handles the
  71          * possibility of an empty output queue.
  72          */
  73         while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
  74                 if (!skb_prev)
  75                         skb_queue_head(&lapb->write_queue, skb);
  76                 else
  77                         skb_append(skb_prev, skb, &lapb->write_queue);
  78                 skb_prev = skb;
  79         }
  80 }
  81
  82 /*
  83  *      Validate that the value of nr is between va and vs. Return true or
  84  *      false for testing.
  85  */
  86 int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
  87 {
  88         unsigned short vc = lapb->va;
  89         int modulus;
  90
  91         modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
  92
  93         while (vc != lapb->vs) {
  94                 if (nr == vc)
  95                         return 1;
  96                 vc = (vc + 1) % modulus;
  97         }
  98
  99         return nr == lapb->vs;
 100 }
 101
 102 /*
 103  *      This routine is the centralised routine for parsing the control
 104  *      information for the different frame formats.
 105  */
 106 int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
 107                 struct lapb_frame *frame)
 108 {
 109         frame->type = LAPB_ILLEGAL;
 110
 111         lapb_dbg(2, "(%p) S%d RX %3ph\n", lapb->dev, lapb->state, skb->data);
 112
 113         /* We always need to look at 2 bytes, sometimes we need
 114          * to look at 3 and those cases are handled below.
 115          */
 116         if (!pskb_may_pull(skb, 2))
 117                 return -1;
 118
 119         if (lapb->mode & LAPB_MLP) {
 120                 if (lapb->mode & LAPB_DCE) {
 121                         if (skb->data[0] == LAPB_ADDR_D)
 122                                 frame->cr = LAPB_COMMAND;
 123                         if (skb->data[0] == LAPB_ADDR_C)
 124                                 frame->cr = LAPB_RESPONSE;
 125                 } else {
 126                         if (skb->data[0] == LAPB_ADDR_C)
 127                                 frame->cr = LAPB_COMMAND;
 128                         if (skb->data[0] == LAPB_ADDR_D)
 129                                 frame->cr = LAPB_RESPONSE;
 130                 }
 131         } else {
 132                 if (lapb->mode & LAPB_DCE) {
 133                         if (skb->data[0] == LAPB_ADDR_B)
 134                                 frame->cr = LAPB_COMMAND;
 135                         if (skb->data[0] == LAPB_ADDR_A)
 136                                 frame->cr = LAPB_RESPONSE;
 137                 } else {
 138                         if (skb->data[0] == LAPB_ADDR_A)
 139                                 frame->cr = LAPB_COMMAND;
 140                         if (skb->data[0] == LAPB_ADDR_B)
 141                                 frame->cr = LAPB_RESPONSE;
 142                 }
 143         }
 144
 145         skb_pull(skb, 1);
 146
 147         if (lapb->mode & LAPB_EXTENDED) {
 148                 if (!(skb->data[0] & LAPB_S)) {
 149                         if (!pskb_may_pull(skb, 2))
 150                                 return -1;
 151                         /*
 152                          * I frame - carries NR/NS/PF
 153                          */
 154                         frame->type       = LAPB_I;
 155                         frame->ns         = (skb->data[0] >> 1) & 0x7F;
 156                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 157                         frame->pf         = skb->data[1] & LAPB_EPF;
 158                         frame->control[0] = skb->data[0];
 159                         frame->control[1] = skb->data[1];
 160                         skb_pull(skb, 2);
 161                 } else if ((skb->data[0] & LAPB_U) == 1) {
 162                         if (!pskb_may_pull(skb, 2))
 163                                 return -1;
 164                         /*
 165                          * S frame - take out PF/NR
 166                          */
 167                         frame->type       = skb->data[0] & 0x0F;
 168                         frame->nr         = (skb->data[1] >> 1) & 0x7F;
 169                         frame->pf         = skb->data[1] & LAPB_EPF;
 170                         frame->control[0] = skb->data[0];
 171                         frame->control[1] = skb->data[1];
 172                         skb_pull(skb, 2);
 173                 } else if ((skb->data[0] & LAPB_U) == 3) {
 174                         /*
 175                          * U frame - take out PF
 176                          */
 177                         frame->type       = skb->data[0] & ~LAPB_SPF;
 178                         frame->pf         = skb->data[0] & LAPB_SPF;
 179                         frame->control[0] = skb->data[0];
 180                         frame->control[1] = 0x00;
 181                         skb_pull(skb, 1);
 182                 }
 183         } else {
 184                 if (!(skb->data[0] & LAPB_S)) {
 185                         /*
 186                          * I frame - carries NR/NS/PF
 187                          */
 188                         frame->type = LAPB_I;
 189                         frame->ns   = (skb->data[0] >> 1) & 0x07;
 190                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 191                         frame->pf   = skb->data[0] & LAPB_SPF;
 192                 } else if ((skb->data[0] & LAPB_U) == 1) {
 193                         /*
 194                          * S frame - take out PF/NR
 195                          */
 196                         frame->type = skb->data[0] & 0x0F;
 197                         frame->nr   = (skb->data[0] >> 5) & 0x07;
 198                         frame->pf   = skb->data[0] & LAPB_SPF;
 199                 } else if ((skb->data[0] & LAPB_U) == 3) {
 200                         /*
 201                          * U frame - take out PF
 202                          */
 203                         frame->type = skb->data[0] & ~LAPB_SPF;
 204                         frame->pf   = skb->data[0] & LAPB_SPF;
 205                 }
 206
 207                 frame->control[0] = skb->data[0];
 208
 209                 skb_pull(skb, 1);
 210         }
 211
 212         return 0;
 213 }
 214
 215 /*
 216  *      This routine is called when the HDLC layer internally  generates a
 217  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 218  *      Only supervisory or unnumbered frames are processed, FRMRs are handled
 219  *      by lapb_transmit_frmr below.
 220  */
 221 void lapb_send_control(struct lapb_cb *lapb, int frametype,
 222                        int poll_bit, int type)
 223 {
 224         struct sk_buff *skb;
 225         unsigned char  *dptr;
 226
 227         if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
 228                 return;
 229
 230         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 231
 232         if (lapb->mode & LAPB_EXTENDED) {
 233                 if ((frametype & LAPB_U) == LAPB_U) {
 234                         dptr   = skb_put(skb, 1);
 235                         *dptr  = frametype;
 236                         *dptr |= poll_bit ? LAPB_SPF : 0;
 237                 } else {
 238                         dptr     = skb_put(skb, 2);
 239                         dptr[0]  = frametype;
 240                         dptr[1]  = (lapb->vr << 1);
 241                         dptr[1] |= poll_bit ? LAPB_EPF : 0;
 242                 }
 243         } else {
 244                 dptr   = skb_put(skb, 1);
 245                 *dptr  = frametype;
 246                 *dptr |= poll_bit ? LAPB_SPF : 0;
 247                 if ((frametype & LAPB_U) == LAPB_S)     /* S frames carry NR */
 248                         *dptr |= (lapb->vr << 5);
 249         }
 250
 251         lapb_transmit_buffer(lapb, skb, type);
 252 }
 253
 254 /*
 255  *      This routine generates FRMRs based on information previously stored in
 256  *      the LAPB control block.
 257  */
 258 void lapb_transmit_frmr(struct lapb_cb *lapb)
 259 {
 260         struct sk_buff *skb;
 261         unsigned char  *dptr;
 262
 263         if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
 264                 return;
 265
 266         skb_reserve(skb, LAPB_HEADER_LEN + 1);
 267
 268         if (lapb->mode & LAPB_EXTENDED) {
 269                 dptr    = skb_put(skb, 6);
 270                 *dptr++ = LAPB_FRMR;
 271                 *dptr++ = lapb->frmr_data.control[0];
 272                 *dptr++ = lapb->frmr_data.control[1];
 273                 *dptr++ = (lapb->vs << 1) & 0xFE;
 274                 *dptr   = (lapb->vr << 1) & 0xFE;
 275                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 276                         *dptr |= 0x01;
 277                 dptr++;
 278                 *dptr++ = lapb->frmr_type;
 279
 280                 lapb_dbg(1, "(%p) S%d TX FRMR %5ph\n",
 281                          lapb->dev, lapb->state,
 282                          &skb->data[1]);
 283         } else {
 284                 dptr    = skb_put(skb, 4);
 285                 *dptr++ = LAPB_FRMR;
 286                 *dptr++ = lapb->frmr_data.control[0];
 287                 *dptr   = (lapb->vs << 1) & 0x0E;
 288                 *dptr  |= (lapb->vr << 5) & 0xE0;
 289                 if (lapb->frmr_data.cr == LAPB_RESPONSE)
 290                         *dptr |= 0x10;
 291                 dptr++;
 292                 *dptr++ = lapb->frmr_type;
 293
 294                 lapb_dbg(1, "(%p) S%d TX FRMR %3ph\n",
 295                          lapb->dev, lapb->state, &skb->data[1]);
 296         }
 297
 298         lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
 299 }