linux/net/lapb/lapb_subr.c
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   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 */
  40void 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 */
  51void 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
  69void 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 */
  91int 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 */
 111int 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 %02X %02X %02X\n",
 117                 lapb->dev, lapb->state,
 118                 skb->data[0], skb->data[1], skb->data[2]);
 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 */
 228void 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 */
 265void 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                lapb_dbg(1, "(%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
 288                         lapb->dev, lapb->state,
 289                         skb->data[1], skb->data[2], skb->data[3],
 290                         skb->data[4], skb->data[5]);
 291        } else {
 292                dptr    = skb_put(skb, 4);
 293                *dptr++ = LAPB_FRMR;
 294                *dptr++ = lapb->frmr_data.control[0];
 295                *dptr   = (lapb->vs << 1) & 0x0E;
 296                *dptr  |= (lapb->vr << 5) & 0xE0;
 297                if (lapb->frmr_data.cr == LAPB_RESPONSE)
 298                        *dptr |= 0x10;
 299                dptr++;
 300                *dptr++ = lapb->frmr_type;
 301
 302                lapb_dbg(1, "(%p) S%d TX FRMR %02X %02X %02X\n",
 303                         lapb->dev, lapb->state, skb->data[1],
 304                         skb->data[2], skb->data[3]);
 305        }
 306
 307        lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
 308}
 309
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