--- /dev/null
+/* Because this code is derived from the 4.3BSD compress source:
+ *
+ * Copyright (c) 1985, 1986 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * James A. Woods, derived from original work by Spencer Thomas
+ * and Joseph Orost.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * This version is for use with contigious buffers on Linux-derived systems.
+ *
+ * ==FILEVERSION 5==
+ *
+ * NOTE TO MAINTAINERS:
+ * If you modify this file at all, increment the number above.
+ * bsd_comp.c is shipped with a PPP distribution as well as with
+ * the kernel; if everyone increases the FILEVERSION number above,
+ * then scripts can do the right thing when deciding whether to
+ * install a new bsd_comp.c file. Don't change the format of that
+ * line otherwise, so the installation script can recognize it.
+ *
+ * $Id: bsd_comp.c,v 1.2 1995/12/18 03:37:05 paulus Exp $
+ */
+
+#ifndef MODULE
+#error This file must be compiled as a module.
+#endif
+
+#include <linux/module.h>
+
+#include <endian.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/interrupt.h>
+#include <linux/ptrace.h>
+#include <linux/ioport.h>
+#include <linux/in.h>
+#include <linux/malloc.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/sched.h> /* to get the struct task_struct */
+#include <linux/string.h> /* used in new tty drivers */
+#include <linux/signal.h> /* used in new tty drivers */
+
+#include <asm/system.h>
+#include <asm/bitops.h>
+#include <asm/segment.h>
+
+#include <net/if.h>
+
+#include <linux/if_ether.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/inet.h>
+#include <linux/ioctl.h>
+
+#include <linux/ppp_defs.h>
+
+#ifdef NEW_SKBUFF
+#include <linux/netprotocol.h>
+#endif
+
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <net/if_arp.h>
+
+#undef PACKETPTR
+#define PACKETPTR 1
+#include <linux/ppp-comp.h>
+#undef PACKETPTR
+
+/*
+ * PPP "BSD compress" compression
+ * The differences between this compression and the classic BSD LZW
+ * source are obvious from the requirement that the classic code worked
+ * with files while this handles arbitrarily long streams that
+ * are broken into packets. They are:
+ *
+ * When the code size expands, a block of junk is not emitted by
+ * the compressor and not expected by the decompressor.
+ *
+ * New codes are not necessarily assigned every time an old
+ * code is output by the compressor. This is because a packet
+ * end forces a code to be emitted, but does not imply that a
+ * new sequence has been seen.
+ *
+ * The compression ratio is checked at the first end of a packet
+ * after the appropriate gap. Besides simplifying and speeding
+ * things up, this makes it more likely that the transmitter
+ * and receiver will agree when the dictionary is cleared when
+ * compression is not going well.
+ */
+
+/*
+ * Macros to extract protocol version and number of bits
+ * from the third byte of the BSD Compress CCP configuration option.
+ */
+
+#define BSD_VERSION(x) ((x) >> 5)
+#define BSD_NBITS(x) ((x) & 0x1F)
+
+#define BSD_CURRENT_VERSION 1
+
+/*
+ * A dictionary for doing BSD compress.
+ */
+
+struct bsd_dict {
+ union { /* hash value */
+ unsigned long fcode;
+ struct {
+#ifndef BIG_ENDIAN_BITFIELD /* Little endian order */
+ unsigned short prefix; /* preceding code */
+ unsigned char suffix; /* last character of new code */
+ unsigned char pad;
+#else /* Big endian order */
+ unsigned char pad;
+ unsigned char suffix; /* last character of new code */
+ unsigned short prefix; /* preceding code */
+#endif
+ } hs;
+ } f;
+ unsigned short codem1; /* output of hash table -1 */
+ unsigned short cptr; /* map code to hash table entry */
+};
+
+struct bsd_db {
+ int totlen; /* length of this structure */
+ unsigned int hsize; /* size of the hash table */
+ unsigned char hshift; /* used in hash function */
+ unsigned char n_bits; /* current bits/code */
+ unsigned char maxbits; /* maximum bits/code */
+ unsigned char debug; /* non-zero if debug desired */
+ unsigned char unit; /* ppp unit number */
+ unsigned short seqno; /* sequence # of next packet */
+ unsigned int mru; /* size of receive (decompress) bufr */
+ unsigned int maxmaxcode; /* largest valid code */
+ unsigned int max_ent; /* largest code in use */
+ unsigned int in_count; /* uncompressed bytes, aged */
+ unsigned int bytes_out; /* compressed bytes, aged */
+ unsigned int ratio; /* recent compression ratio */
+ unsigned int checkpoint; /* when to next check the ratio */
+ unsigned int clear_count; /* times dictionary cleared */
+ unsigned int incomp_count; /* incompressible packets */
+ unsigned int incomp_bytes; /* incompressible bytes */
+ unsigned int uncomp_count; /* uncompressed packets */
+ unsigned int uncomp_bytes; /* uncompressed bytes */
+ unsigned int comp_count; /* compressed packets */
+ unsigned int comp_bytes; /* compressed bytes */
+ unsigned short *lens; /* array of lengths of codes */
+ struct bsd_dict *dict; /* dictionary */
+};
+
+#define BSD_OVHD 2 /* BSD compress overhead/packet */
+#define MIN_BSD_BITS 9
+#define BSD_INIT_BITS MIN_BSD_BITS
+#define MAX_BSD_BITS 15
+
+static void bsd_free (void *state);
+static void *bsd_alloc(unsigned char *options, int opt_len, int decomp);
+static void *bsd_comp_alloc (unsigned char *options, int opt_len);
+static void *bsd_decomp_alloc (unsigned char *options, int opt_len);
+
+static int bsd_init (void *db, unsigned char *options,
+ int opt_len, int unit, int debug, int decomp);
+static int bsd_comp_init (void *state, unsigned char *options,
+ int opt_len, int unit, int opthdr, int debug);
+static int bsd_decomp_init (void *state, unsigned char *options,
+ int opt_len, int unit, int opthdr, int mru,
+ int debug);
+
+static void bsd_reset (void *state);
+static void bsd_comp_stats (void *state, struct compstat *stats);
+
+static int bsd_compress (void *state, unsigned char *rptr,
+ unsigned char *obuf, int isize, int osize);
+static void bsd_incomp (void *state, unsigned char *ibuf, int icnt);
+
+static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
+ unsigned char *obuf, int osize);
+
+/* These are in ppp.c */
+extern int ppp_register_compressor (struct compressor *cp);
+extern void ppp_unregister_compressor (struct compressor *cp);
+
+/*
+ * the next two codes should not be changed lightly, as they must not
+ * lie within the contiguous general code space.
+ */
+#define CLEAR 256 /* table clear output code */
+#define FIRST 257 /* first free entry */
+#define LAST 255
+
+#define MAXCODE(b) ((1 << (b)) - 1)
+#define BADCODEM1 MAXCODE(MAX_BSD_BITS);
+
+#define BSD_HASH(prefix,suffix,hshift) ((((unsigned long)(suffix))<<(hshift)) \
+ ^ (unsigned long)(prefix))
+#define BSD_KEY(prefix,suffix) ((((unsigned long)(suffix)) << 16) \
+ + (unsigned long)(prefix))
+
+#define CHECK_GAP 10000 /* Ratio check interval */
+
+#define RATIO_SCALE_LOG 8
+#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
+#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
+
+/*
+ * clear the dictionary
+ */
+
+static void
+bsd_clear(struct bsd_db *db)
+{
+ db->clear_count++;
+ db->max_ent = FIRST-1;
+ db->n_bits = BSD_INIT_BITS;
+ db->bytes_out = 0;
+ db->in_count = 0;
+ db->incomp_count = 0;
+ db->ratio = 0;
+ db->checkpoint = CHECK_GAP;
+}
+
+/*
+ * If the dictionary is full, then see if it is time to reset it.
+ *
+ * Compute the compression ratio using fixed-point arithmetic
+ * with 8 fractional bits.
+ *
+ * Since we have an infinite stream instead of a single file,
+ * watch only the local compression ratio.
+ *
+ * Since both peers must reset the dictionary at the same time even in
+ * the absence of CLEAR codes (while packets are incompressible), they
+ * must compute the same ratio.
+ */
+
+static int bsd_check (struct bsd_db *db) /* 1=output CLEAR */
+ {
+ unsigned int new_ratio;
+
+ if (db->in_count >= db->checkpoint)
+ {
+ /* age the ratio by limiting the size of the counts */
+ if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
+ {
+ db->in_count -= (db->in_count >> 2);
+ db->bytes_out -= (db->bytes_out >> 2);
+ }
+
+ db->checkpoint = db->in_count + CHECK_GAP;
+
+ if (db->max_ent >= db->maxmaxcode)
+ {
+ /* Reset the dictionary only if the ratio is worse,
+ * or if it looks as if it has been poisoned
+ * by incompressible data.
+ *
+ * This does not overflow, because
+ * db->in_count <= RATIO_MAX.
+ */
+
+ new_ratio = db->in_count << RATIO_SCALE_LOG;
+ if (db->bytes_out != 0)
+ {
+ new_ratio /= db->bytes_out;
+ }
+
+ if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
+ {
+ bsd_clear (db);
+ return 1;
+ }
+ db->ratio = new_ratio;
+ }
+ }
+ return 0;
+ }
+
+/*
+ * Return statistics.
+ */
+
+static void bsd_comp_stats (void *state, struct compstat *stats)
+ {
+ struct bsd_db *db = (struct bsd_db *) state;
+
+ stats->unc_bytes = db->uncomp_bytes;
+ stats->unc_packets = db->uncomp_count;
+ stats->comp_bytes = db->comp_bytes;
+ stats->comp_packets = db->comp_count;
+ stats->inc_bytes = db->incomp_bytes;
+ stats->inc_packets = db->incomp_count;
+ stats->in_count = db->in_count;
+ stats->bytes_out = db->bytes_out;
+ }
+
+/*
+ * Reset state, as on a CCP ResetReq.
+ */
+
+static void bsd_reset (void *state)
+ {
+ struct bsd_db *db = (struct bsd_db *) state;
+
+ bsd_clear(db);
+
+ db->seqno = 0;
+ db->clear_count = 0;
+ }
+
+/*
+ * Release the compression structure
+ */
+
+static void bsd_free (void *state)
+ {
+ struct bsd_db *db = (struct bsd_db *) state;
+
+ if (db)
+ {
+/*
+ * Release the dictionary
+ */
+ if (db->dict)
+ {
+ vfree (db->dict);
+ db->dict = NULL;
+ }
+/*
+ * Release the string buffer
+ */
+ if (db->lens)
+ {
+ vfree (db->lens);
+ db->lens = NULL;
+ }
+/*
+ * Finally release the structure itself.
+ */
+ kfree (db);
+ MOD_DEC_USE_COUNT;
+ }
+ }
+
+/*
+ * Allocate space for a (de) compressor.
+ */
+
+static void *bsd_alloc (unsigned char *options, int opt_len, int decomp)
+ {
+ int bits;
+ unsigned int hsize, hshift, maxmaxcode;
+ struct bsd_db *db;
+
+ if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
+ || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
+ {
+ return NULL;
+ }
+
+ bits = BSD_NBITS(options[2]);
+
+ switch (bits)
+ {
+ case 9: /* needs 82152 for both directions */
+ case 10: /* needs 84144 */
+ case 11: /* needs 88240 */
+ case 12: /* needs 96432 */
+ hsize = 5003;
+ hshift = 4;
+ break;
+ case 13: /* needs 176784 */
+ hsize = 9001;
+ hshift = 5;
+ break;
+ case 14: /* needs 353744 */
+ hsize = 18013;
+ hshift = 6;
+ break;
+ case 15: /* needs 691440 */
+ hsize = 35023;
+ hshift = 7;
+ break;
+ case 16: /* needs 1366160--far too much, */
+ /* hsize = 69001; */ /* and 69001 is too big for cptr */
+ /* hshift = 8; */ /* in struct bsd_db */
+ /* break; */
+ default:
+ return NULL;
+ }
+/*
+ * Allocate the main control structure for this instance.
+ */
+ maxmaxcode = MAXCODE(bits);
+ db = (struct bsd_db *) kmalloc (sizeof (struct bsd_db),
+ GFP_KERNEL);
+ if (!db)
+ {
+ return NULL;
+ }
+
+ memset (db, 0, sizeof(struct bsd_db));
+/*
+ * Allocate space for the dictionary. This may be more than one page in
+ * length.
+ */
+ db->dict = (struct bsd_dict *) vmalloc (hsize *
+ sizeof (struct bsd_dict));
+ if (!db->dict)
+ {
+ bsd_free (db);
+ return NULL;
+ }
+
+ MOD_INC_USE_COUNT;
+/*
+ * If this is the compression buffer then there is no length data.
+ */
+ if (!decomp)
+ {
+ db->lens = NULL;
+ }
+/*
+ * For decompression, the length information is needed as well.
+ */
+ else
+ {
+ db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) *
+ sizeof (db->lens[0]));
+ if (!db->lens)
+ {
+ bsd_free (db);
+ return (NULL);
+ }
+ }
+/*
+ * Initialize the data information for the compression code
+ */
+ db->totlen = sizeof (struct bsd_db) +
+ (sizeof (struct bsd_dict) * hsize);
+
+ db->hsize = hsize;
+ db->hshift = hshift;
+ db->maxmaxcode = maxmaxcode;
+ db->maxbits = bits;
+
+ return (void *) db;
+ }
+
+static void *bsd_comp_alloc (unsigned char *options, int opt_len)
+ {
+ return bsd_alloc (options, opt_len, 0);
+ }
+
+static void *bsd_decomp_alloc (unsigned char *options, int opt_len)
+ {
+ return bsd_alloc (options, opt_len, 1);
+ }
+
+/*
+ * Initialize the database.
+ */
+
+static int bsd_init (void *state, unsigned char *options,
+ int opt_len, int unit, int debug, int decomp)
+ {
+ struct bsd_db *db = state;
+ int indx;
+
+ if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3)
+ || (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
+ || (BSD_NBITS(options[2]) != db->maxbits)
+ || (decomp && db->lens == NULL))
+ {
+ return 0;
+ }
+
+ if (decomp)
+ {
+ indx = LAST;
+ do
+ {
+ db->lens[indx] = 1;
+ }
+ while (indx-- > 0);
+ }
+
+ indx = db->hsize;
+ while (indx-- != 0)
+ {
+ db->dict[indx].codem1 = BADCODEM1;
+ db->dict[indx].cptr = 0;
+ }
+
+ db->unit = unit;
+ db->mru = 0;
+#ifndef DEBUG
+ if (debug)
+#endif
+ db->debug = 1;
+
+ bsd_reset(db);
+
+ return 1;
+ }
+
+static int bsd_comp_init (void *state, unsigned char *options,
+ int opt_len, int unit, int opthdr, int debug)
+ {
+ return bsd_init (state, options, opt_len, unit, debug, 0);
+ }
+
+static int bsd_decomp_init (void *state, unsigned char *options,
+ int opt_len, int unit, int opthdr, int mru,
+ int debug)
+ {
+ return bsd_init (state, options, opt_len, unit, debug, 1);
+ }
+
+/*
+ * Obtain pointers to the various structures in the compression tables
+ */
+
+#define dict_ptrx(p,idx) &(p->dict[idx])
+#define lens_ptrx(p,idx) &(p->lens[idx])
+
+#ifdef DEBUG
+static unsigned short *lens_ptr(struct bsd_db *db, int idx)
+ {
+ if ((unsigned int) idx > (unsigned int) db->maxmaxcode)
+ {
+ printk ("<9>ppp: lens_ptr(%d) > max\n", idx);
+ idx = 0;
+ }
+ return lens_ptrx (db, idx);
+ }
+
+static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
+ {
+ if ((unsigned int) idx >= (unsigned int) db->hsize)
+ {
+ printk ("<9>ppp: dict_ptr(%d) > max\n", idx);
+ idx = 0;
+ }
+ return dict_ptrx (db, idx);
+ }
+
+#else
+#define lens_ptr(db,idx) lens_ptrx(db,idx)
+#define dict_ptr(db,idx) dict_ptrx(db,idx)
+#endif
+
+/*
+ * compress a packet
+ *
+ * The result of this function is the size of the compressed
+ * packet. A zero is returned if the packet was not compressed
+ * for some reason, such as the size being larger than uncompressed.
+ *
+ * One change from the BSD compress command is that when the
+ * code size expands, we do not output a bunch of padding.
+ */
+
+static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf,
+ int isize, int osize)
+ {
+ struct bsd_db *db;
+ int hshift;
+ unsigned int max_ent;
+ unsigned int n_bits;
+ unsigned int bitno;
+ unsigned long accm;
+ int ent;
+ unsigned long fcode;
+ struct bsd_dict *dictp;
+ unsigned char c;
+ int hval;
+ int disp;
+ int ilen;
+ int mxcode;
+ unsigned char *wptr;
+ int olen;
+
+#define PUTBYTE(v) \
+ { \
+ ++olen; \
+ if (wptr) \
+ { \
+ *wptr++ = (unsigned char) (v); \
+ if (olen >= osize) \
+ { \
+ wptr = NULL; \
+ } \
+ } \
+ }
+
+#define OUTPUT(ent) \
+ { \
+ bitno -= n_bits; \
+ accm |= ((ent) << bitno); \
+ do \
+ { \
+ PUTBYTE(accm >> 24); \
+ accm <<= 8; \
+ bitno += 8; \
+ } \
+ while (bitno <= 24); \
+ }
+
+ /*
+ * If the protocol is not in the range we're interested in,
+ * just return without compressing the packet. If it is,
+ * the protocol becomes the first byte to compress.
+ */
+
+ ent = PPP_PROTOCOL(rptr);
+ if (ent < 0x21 || ent > 0xf9)
+ {
+ return 0;
+ }
+
+ db = (struct bsd_db *) state;
+ hshift = db->hshift;
+ max_ent = db->max_ent;
+ n_bits = db->n_bits;
+ bitno = 32;
+ accm = 0;
+ mxcode = MAXCODE (n_bits);
+
+ /* Initialize the output pointers */
+ wptr = obuf;
+ olen = PPP_HDRLEN + BSD_OVHD;
+
+ if (osize > isize)
+ {
+ osize = isize;
+ }
+
+ /* This is the PPP header information */
+ if (wptr)
+ {
+ *wptr++ = PPP_ADDRESS(rptr);
+ *wptr++ = PPP_CONTROL(rptr);
+ *wptr++ = 0;
+ *wptr++ = PPP_COMP;
+ *wptr++ = db->seqno >> 8;
+ *wptr++ = db->seqno;
+ }
+
+ /* Skip the input header */
+ rptr += PPP_HDRLEN;
+ isize -= PPP_HDRLEN;
+ ilen = ++isize; /* This is off by one, but that is what is in draft! */
+
+ while (--ilen > 0)
+ {
+ c = *rptr++;
+ fcode = BSD_KEY (ent, c);
+ hval = BSD_HASH (ent, c, hshift);
+ dictp = dict_ptr (db, hval);
+
+ /* Validate and then check the entry. */
+ if (dictp->codem1 >= max_ent)
+ {
+ goto nomatch;
+ }
+
+ if (dictp->f.fcode == fcode)
+ {
+ ent = dictp->codem1 + 1;
+ continue; /* found (prefix,suffix) */
+ }
+
+ /* continue probing until a match or invalid entry */
+ disp = (hval == 0) ? 1 : hval;
+
+ do
+ {
+ hval += disp;
+ if (hval >= db->hsize)
+ {
+ hval -= db->hsize;
+ }
+ dictp = dict_ptr (db, hval);
+ if (dictp->codem1 >= max_ent)
+ {
+ goto nomatch;
+ }
+ }
+ while (dictp->f.fcode != fcode);
+
+ ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
+ continue;
+
+nomatch:
+ OUTPUT(ent); /* output the prefix */
+
+ /* code -> hashtable */
+ if (max_ent < db->maxmaxcode)
+ {
+ struct bsd_dict *dictp2;
+ struct bsd_dict *dictp3;
+ int indx;
+
+ /* expand code size if needed */
+ if (max_ent >= mxcode)
+ {
+ db->n_bits = ++n_bits;
+ mxcode = MAXCODE (n_bits);
+ }
+
+ /* Invalidate old hash table entry using
+ * this code, and then take it over.
+ */
+
+ dictp2 = dict_ptr (db, max_ent + 1);
+ indx = dictp2->cptr;
+ dictp3 = dict_ptr (db, indx);
+
+ if (dictp3->codem1 == max_ent)
+ {
+ dictp3->codem1 = BADCODEM1;
+ }
+
+ dictp2->cptr = hval;
+ dictp->codem1 = max_ent;
+ dictp->f.fcode = fcode;
+ db->max_ent = ++max_ent;
+
+ if (db->lens)
+ {
+ unsigned short *len1 = lens_ptr (db, max_ent);
+ unsigned short *len2 = lens_ptr (db, ent);
+ *len1 = *len2 + 1;
+ }
+ }
+ ent = c;
+ }
+
+ OUTPUT(ent); /* output the last code */
+
+ db->bytes_out += olen; /* Do not count bytes from here */
+ db->uncomp_bytes += isize;
+ db->in_count += isize;
+ ++db->uncomp_count;
+ ++db->seqno;
+
+ if (bitno < 32)
+ {
+ ++db->bytes_out; /* must be set before calling bsd_check */
+ }
+
+ /*
+ * Generate the clear command if needed
+ */
+
+ if (bsd_check(db))
+ {
+ OUTPUT (CLEAR);
+ }
+
+ /*
+ * Pad dribble bits of last code with ones.
+ * Do not emit a completely useless byte of ones.
+ */
+
+ if (bitno != 32)
+ {
+ PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
+ }
+
+ /*
+ * Increase code size if we would have without the packet
+ * boundary because the decompressor will do so.
+ */
+
+ if (max_ent >= mxcode && max_ent < db->maxmaxcode)
+ {
+ db->n_bits++;
+ }
+
+ /* If output length is too large then this is an incomplete frame. */
+ if (wptr == NULL)
+ {
+ ++db->incomp_count;
+ db->incomp_bytes += isize;
+ olen = 0;
+ }
+ else /* Count the number of compressed frames */
+ {
+ ++db->comp_count;
+ db->comp_bytes += olen;
+ }
+
+ /* Return the resulting output length */
+ return olen;
+#undef OUTPUT
+#undef PUTBYTE
+ }
+
+/*
+ * Update the "BSD Compress" dictionary on the receiver for
+ * incompressible data by pretending to compress the incoming data.
+ */
+
+static void bsd_incomp (void *state, unsigned char *ibuf, int icnt)
+ {
+ (void) bsd_compress (state, ibuf, (char *) 0, icnt, 0);
+ }
+
+/*
+ * Decompress "BSD Compress".
+ *
+ * Because of patent problems, we return DECOMP_ERROR for errors
+ * found by inspecting the input data and for system problems, but
+ * DECOMP_FATALERROR for any errors which could possibly be said to
+ * be being detected "after" decompression. For DECOMP_ERROR,
+ * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
+ * infringing a patent of Motorola's if we do, so we take CCP down
+ * instead.
+ *
+ * Given that the frame has the correct sequence number and a good FCS,
+ * errors such as invalid codes in the input most likely indicate a
+ * bug, so we return DECOMP_FATALERROR for them in order to turn off
+ * compression, even though they are detected by inspecting the input.
+ */
+
+static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
+ unsigned char *obuf, int osize)
+ {
+ struct bsd_db *db;
+ unsigned int max_ent;
+ unsigned long accm;
+ unsigned int bitno; /* 1st valid bit in accm */
+ unsigned int n_bits;
+ unsigned int tgtbitno; /* bitno when we have a code */
+ struct bsd_dict *dictp;
+ int explen;
+ int seq;
+ unsigned int incode;
+ unsigned int oldcode;
+ unsigned int finchar;
+ unsigned char *p;
+ unsigned char *wptr;
+ int adrs;
+ int ctrl;
+ int ilen;
+ int codelen;
+ int extra;
+
+ db = (struct bsd_db *) state;
+ max_ent = db->max_ent;
+ accm = 0;
+ bitno = 32; /* 1st valid bit in accm */
+ n_bits = db->n_bits;
+ tgtbitno = 32 - n_bits; /* bitno when we have a code */
+
+ /*
+ * Save the address/control from the PPP header
+ * and then get the sequence number.
+ */
+
+ adrs = PPP_ADDRESS (ibuf);
+ ctrl = PPP_CONTROL (ibuf);
+
+ seq = (ibuf[4] << 8) + ibuf[5];
+
+ ibuf += (PPP_HDRLEN + 2);
+ ilen = isize - (PPP_HDRLEN + 2);
+
+ /*
+ * Check the sequence number and give up if it differs from
+ * the value we're expecting.
+ */
+
+ if (seq != db->seqno)
+ {
+ if (db->debug)
+ {
+ printk("bsd_decomp%d: bad sequence # %d, expected %d\n",
+ db->unit, seq, db->seqno - 1);
+ }
+ return DECOMP_ERROR;
+ }
+
+ ++db->seqno;
+ db->bytes_out += ilen;
+
+ /*
+ * Fill in the ppp header, but not the last byte of the protocol
+ * (that comes from the decompressed data).
+ */
+
+ wptr = obuf;
+ *wptr++ = adrs;
+ *wptr++ = ctrl;
+ *wptr++ = 0;
+
+ oldcode = CLEAR;
+ explen = 3;
+
+ /*
+ * Keep the checkpoint correctly so that incompressible packets
+ * clear the dictionary at the proper times.
+ */
+
+ for (;;)
+ {
+ if (ilen-- <= 0)
+ {
+ db->in_count += (explen - 3); /* don't count the header */
+ break;
+ }
+
+ /*
+ * Accumulate bytes until we have a complete code.
+ * Then get the next code, relying on the 32-bit,
+ * unsigned accm to mask the result.
+ */
+
+ bitno -= 8;
+ accm |= *ibuf++ << bitno;
+ if (tgtbitno < bitno)
+ {
+ continue;
+ }
+
+ incode = accm >> tgtbitno;
+ accm <<= n_bits;
+ bitno += n_bits;
+
+ /*
+ * The dictionary must only be cleared at the end of a packet.
+ */
+
+ if (incode == CLEAR)
+ {
+ if (ilen > 0)
+ {
+ if (db->debug)
+ {
+ printk("bsd_decomp%d: bad CLEAR\n", db->unit);
+ }
+ return DECOMP_FATALERROR; /* probably a bug */
+ }
+
+ bsd_clear(db);
+ break;
+ }
+
+ if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
+ || (incode > max_ent && oldcode == CLEAR))
+ {
+ if (db->debug)
+ {
+ printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
+ db->unit, incode, oldcode);
+ printk("max_ent=0x%x explen=%d seqno=%d\n",
+ max_ent, explen, db->seqno);
+ }
+ return DECOMP_FATALERROR; /* probably a bug */
+ }
+
+ /* Special case for KwKwK string. */
+ if (incode > max_ent)
+ {
+ finchar = oldcode;
+ extra = 1;
+ }
+ else
+ {
+ finchar = incode;
+ extra = 0;
+ }
+
+ codelen = *(lens_ptr (db, finchar));
+ explen += codelen + extra;
+ if (explen > osize)
+ {
+ if (db->debug)
+ {
+ printk("bsd_decomp%d: ran out of mru\n", db->unit);
+#ifdef DEBUG
+ printk(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
+ ilen, finchar, codelen, explen);
+#endif
+ }
+ return DECOMP_FATALERROR;
+ }
+
+ /*
+ * Decode this code and install it in the decompressed buffer.
+ */
+
+ wptr += codelen;
+ p = wptr;
+ while (finchar > LAST)
+ {
+ struct bsd_dict *dictp2 = dict_ptr (db, finchar);
+
+ dictp = dict_ptr (db, dictp2->cptr);
+#ifdef DEBUG
+ if (--codelen <= 0 || dictp->codem1 != finchar-1)
+ {
+ if (codelen <= 0)
+ {
+ printk("bsd_decomp%d: fell off end of chain ", db->unit);
+ printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
+ incode, finchar, dictp2->cptr, max_ent);
+ }
+ else
+ {
+ if (dictp->codem1 != finchar-1)
+ {
+ printk("bsd_decomp%d: bad code chain 0x%x "
+ "finchar=0x%x ",
+ db->unit, incode, finchar);
+
+ printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n",
+ oldcode, dictp2->cptr, dictp->codem1);
+ }
+ }
+ return DECOMP_FATALERROR;
+ }
+#endif
+ *--p = dictp->f.hs.suffix;
+ finchar = dictp->f.hs.prefix;
+ }
+ *--p = finchar;
+
+#ifdef DEBUG
+ if (--codelen != 0)
+ {
+ printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
+ db->unit, codelen, incode, max_ent);
+ }
+#endif
+
+ if (extra) /* the KwKwK case again */
+ {
+ *wptr++ = finchar;
+ }
+
+ /*
+ * If not first code in a packet, and
+ * if not out of code space, then allocate a new code.
+ *
+ * Keep the hash table correct so it can be used
+ * with uncompressed packets.
+ */
+
+ if (oldcode != CLEAR && max_ent < db->maxmaxcode)
+ {
+ struct bsd_dict *dictp2, *dictp3;
+ unsigned short *lens1, *lens2;
+ unsigned long fcode;
+ int hval, disp, indx;
+
+ fcode = BSD_KEY(oldcode,finchar);
+ hval = BSD_HASH(oldcode,finchar,db->hshift);
+ dictp = dict_ptr (db, hval);
+
+ /* look for a free hash table entry */
+ if (dictp->codem1 < max_ent)
+ {
+ disp = (hval == 0) ? 1 : hval;
+ do
+ {
+ hval += disp;
+ if (hval >= db->hsize)
+ {
+ hval -= db->hsize;
+ }
+ dictp = dict_ptr (db, hval);
+ }
+ while (dictp->codem1 < max_ent);
+ }
+
+ /*
+ * Invalidate previous hash table entry
+ * assigned this code, and then take it over
+ */
+
+ dictp2 = dict_ptr (db, max_ent + 1);
+ indx = dictp2->cptr;
+ dictp3 = dict_ptr (db, indx);
+
+ if (dictp3->codem1 == max_ent)
+ {
+ dictp3->codem1 = BADCODEM1;
+ }
+
+ dictp2->cptr = hval;
+ dictp->codem1 = max_ent;
+ dictp->f.fcode = fcode;
+ db->max_ent = ++max_ent;
+
+ /* Update the length of this string. */
+ lens1 = lens_ptr (db, max_ent);
+ lens2 = lens_ptr (db, oldcode);
+ *lens1 = *lens2 + 1;
+
+ /* Expand code size if needed. */
+ if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
+ {
+ db->n_bits = ++n_bits;
+ tgtbitno = 32-n_bits;
+ }
+ }
+ oldcode = incode;
+ }
+
+ ++db->comp_count;
+ ++db->uncomp_count;
+ db->comp_bytes += isize - BSD_OVHD - PPP_HDRLEN;
+ db->uncomp_bytes += explen;
+
+ if (bsd_check(db))
+ {
+ if (db->debug)
+ {
+ printk("bsd_decomp%d: peer should have cleared dictionary on %d\n",
+ db->unit, db->seqno - 1);
+ }
+ }
+ return explen;
+ }
+
+/*************************************************************
+ * Table of addresses for the BSD compression module
+ *************************************************************/
+
+static struct compressor ppp_bsd_compress = {
+ CI_BSD_COMPRESS, /* compress_proto */
+ bsd_comp_alloc, /* comp_alloc */
+ bsd_free, /* comp_free */
+ bsd_comp_init, /* comp_init */
+ bsd_reset, /* comp_reset */
+ bsd_compress, /* compress */
+ bsd_comp_stats, /* comp_stat */
+ bsd_decomp_alloc, /* decomp_alloc */
+ bsd_free, /* decomp_free */
+ bsd_decomp_init, /* decomp_init */
+ bsd_reset, /* decomp_reset */
+ bsd_decompress, /* decompress */
+ bsd_incomp, /* incomp */
+ bsd_comp_stats /* decomp_stat */
+};
+
+/*************************************************************
+ * Module support routines
+ *************************************************************/
+
+int
+init_module(void)
+{
+ int answer = ppp_register_compressor (&ppp_bsd_compress);
+ if (answer == 0)
+ printk (KERN_INFO "PPP BSD Compression module registered\n");
+ return answer;
+}
+
+void
+cleanup_module(void)
+{
+ ppp_unregister_compressor (&ppp_bsd_compress);
+}
projects / ppp.git / blobdiff