LXR linux/net/lapb/lapb

   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 */
  35void 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 */
  46void 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
  64void 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 */
  86int 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 */
 106int 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 */
 221void 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 */
 258void 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}
 300