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Diffstat (limited to 'pppdump/bsd-comp.c')
| -rw-r--r-- | pppdump/bsd-comp.c | 749 |
1 files changed, 749 insertions, 0 deletions
diff --git a/pppdump/bsd-comp.c b/pppdump/bsd-comp.c new file mode 100644 index 0000000..b08f2b7 --- /dev/null +++ b/pppdump/bsd-comp.c @@ -0,0 +1,749 @@ +/* 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. + */ + +/* + * $Id: bsd-comp.c,v 1.1 1999/03/23 03:21:57 paulus Exp $ + */ + +#include <sys/types.h> +#include <stdlib.h> +#include "ppp_defs.h" +#include "ppp-comp.h" + +#if DO_BSD_COMPRESS + +/* + * 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. + */ + +/* + * A dictionary for doing BSD compress. + */ +struct bsd_db { + int totlen; /* length of this structure */ + u_int hsize; /* size of the hash table */ + u_char hshift; /* used in hash function */ + u_char n_bits; /* current bits/code */ + u_char maxbits; + u_char debug; + u_char unit; + u_short seqno; /* sequence number of next packet */ + u_int hdrlen; /* header length to preallocate */ + u_int mru; + u_int maxmaxcode; /* largest valid code */ + u_int max_ent; /* largest code in use */ + u_int in_count; /* uncompressed bytes, aged */ + u_int bytes_out; /* compressed bytes, aged */ + u_int ratio; /* recent compression ratio */ + u_int checkpoint; /* when to next check the ratio */ + u_int clear_count; /* times dictionary cleared */ + u_int incomp_count; /* incompressible packets */ + u_int incomp_bytes; /* incompressible bytes */ + u_int uncomp_count; /* uncompressed packets */ + u_int uncomp_bytes; /* uncompressed bytes */ + u_int comp_count; /* compressed packets */ + u_int comp_bytes; /* compressed bytes */ + u_short *lens; /* array of lengths of codes */ + struct bsd_dict { + union { /* hash value */ + u_int32_t fcode; + struct { +#ifdef BSD_LITTLE_ENDIAN + u_short prefix; /* preceding code */ + u_char suffix; /* last character of new code */ + u_char pad; +#else + u_char pad; + u_char suffix; /* last character of new code */ + u_short prefix; /* preceding code */ +#endif + } hs; + } f; + u_short codem1; /* output of hash table -1 */ + u_short cptr; /* map code to hash table entry */ + } dict[1]; +}; + +#define BSD_OVHD 2 /* BSD compress overhead/packet */ +#define BSD_INIT_BITS BSD_MIN_BITS + +static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); +static void bsd_free __P((void *state)); +static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, + int unit, int hdrlen, int mru, int debug)); +static void bsd_incomp __P((void *state, u_char *dmsg, int len)); +static int bsd_decompress __P((void *state, u_char *cmp, int inlen, + u_char *dmp, int *outlen)); +static void bsd_reset __P((void *state)); +static void bsd_comp_stats __P((void *state, struct compstat *stats)); + +/* + * Exported procedures. + */ +struct compressor ppp_bsd_compress = { + CI_BSD_COMPRESS, /* compress_proto */ + 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 */ +}; + +/* + * 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(BSD_MAX_BITS) + +#define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ + ^ (u_int32_t)(prefix)) +#define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ + + (u_int32_t)(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(db) + struct bsd_db *db; +{ + db->clear_count++; + db->max_ent = FIRST-1; + db->n_bits = BSD_INIT_BITS; + db->ratio = 0; + db->bytes_out = 0; + db->in_count = 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 /* 1=output CLEAR */ +bsd_check(db) + struct bsd_db *db; +{ + u_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/4; + db->bytes_out -= db->bytes_out/4; + } + + 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(state, stats) + void *state; + struct compstat *stats; +{ + struct bsd_db *db = (struct bsd_db *) state; + u_int out; + + 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->ratio = db->in_count; + out = db->bytes_out; + if (stats->ratio <= 0x7fffff) + stats->ratio <<= 8; + else + out >>= 8; + if (out != 0) + stats->ratio /= out; +} + +/* + * Reset state, as on a CCP ResetReq. + */ +static void +bsd_reset(state) + void *state; +{ + struct bsd_db *db = (struct bsd_db *) state; + + db->seqno = 0; + bsd_clear(db); + db->clear_count = 0; +} + +/* + * Allocate space for a (de) compressor. + */ +static void * +bsd_alloc(options, opt_len, decomp) + u_char *options; + int opt_len, decomp; +{ + int bits; + u_int newlen, 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; + } + + maxmaxcode = MAXCODE(bits); + newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); + db = (struct bsd_db *) malloc(newlen); + if (!db) + return NULL; + bzero(db, sizeof(*db) - sizeof(db->dict)); + + if (!decomp) { + db->lens = NULL; + } else { + db->lens = (u_short *) malloc((maxmaxcode+1) * sizeof(db->lens[0])); + if (!db->lens) { + free(db); + return NULL; + } + } + + db->totlen = newlen; + db->hsize = hsize; + db->hshift = hshift; + db->maxmaxcode = maxmaxcode; + db->maxbits = bits; + + return (void *) db; +} + +static void +bsd_free(state) + void *state; +{ + struct bsd_db *db = (struct bsd_db *) state; + + if (db->lens) + free(db->lens); + free(db); +} + +static void * +bsd_decomp_alloc(options, opt_len) + u_char *options; + int opt_len; +{ + return bsd_alloc(options, opt_len, 1); +} + +/* + * Initialize the database. + */ +static int +bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) + struct bsd_db *db; + u_char *options; + int opt_len, unit, hdrlen, mru, debug, decomp; +{ + int i; + + if (opt_len < CILEN_BSD_COMPRESS + || options[0] != CI_BSD_COMPRESS || options[1] != CILEN_BSD_COMPRESS + || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION + || BSD_NBITS(options[2]) != db->maxbits + || decomp && db->lens == NULL) + return 0; + + if (decomp) { + i = LAST+1; + while (i != 0) + db->lens[--i] = 1; + } + i = db->hsize; + while (i != 0) { + db->dict[--i].codem1 = BADCODEM1; + db->dict[i].cptr = 0; + } + + db->unit = unit; + db->hdrlen = hdrlen; + db->mru = mru; + if (debug) + db->debug = 1; + + bsd_reset(db); + + return 1; +} + +static int +bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) + void *state; + u_char *options; + int opt_len, unit, hdrlen, mru, debug; +{ + return bsd_init((struct bsd_db *) state, options, opt_len, + unit, hdrlen, mru, debug, 1); +} + + +/* + * Update the "BSD Compress" dictionary on the receiver for + * incompressible data by pretending to compress the incoming data. + */ +static void +bsd_incomp(state, dmsg, mlen) + void *state; + u_char *dmsg; + int mlen; +{ + struct bsd_db *db = (struct bsd_db *) state; + u_int hshift = db->hshift; + u_int max_ent = db->max_ent; + u_int n_bits = db->n_bits; + struct bsd_dict *dictp; + u_int32_t fcode; + u_char c; + long hval, disp; + int slen, ilen; + u_int bitno = 7; + u_char *rptr; + u_int ent; + + rptr = dmsg; + ent = rptr[0]; /* get the protocol */ + if (ent == 0) { + ++rptr; + --mlen; + ent = rptr[0]; + } + if ((ent & 1) == 0 || ent < 0x21 || ent > 0xf9) + return; + + db->seqno++; + ilen = 1; /* count the protocol as 1 byte */ + ++rptr; + slen = dmsg + mlen - rptr; + ilen += slen; + for (; slen > 0; --slen) { + c = *rptr++; + fcode = BSD_KEY(ent, c); + hval = BSD_HASH(ent, c, hshift); + dictp = &db->dict[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 = &db->dict[hval]; + if (dictp->codem1 >= max_ent) + goto nomatch; + } while (dictp->f.fcode != fcode); + ent = dictp->codem1+1; + continue; /* finally found (prefix,suffix) */ + + nomatch: /* output (count) the prefix */ + bitno += n_bits; + + /* code -> hashtable */ + if (max_ent < db->maxmaxcode) { + struct bsd_dict *dictp2; + /* expand code size if needed */ + if (max_ent >= MAXCODE(n_bits)) + db->n_bits = ++n_bits; + + /* Invalidate previous hash table entry + * assigned this code, and then take it over. + */ + dictp2 = &db->dict[max_ent+1]; + if (db->dict[dictp2->cptr].codem1 == max_ent) + db->dict[dictp2->cptr].codem1 = BADCODEM1; + dictp2->cptr = hval; + dictp->codem1 = max_ent; + dictp->f.fcode = fcode; + + db->max_ent = ++max_ent; + db->lens[max_ent] = db->lens[ent]+1; + } + ent = c; + } + bitno += n_bits; /* output (count) the last code */ + db->bytes_out += bitno/8; + db->in_count += ilen; + (void)bsd_check(db); + + ++db->incomp_count; + db->incomp_bytes += ilen; + ++db->uncomp_count; + db->uncomp_bytes += ilen; + + /* Increase code size if we would have without the packet + * boundary and as the decompressor will. + */ + if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) + db->n_bits++; +} + + +/* + * 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(state, cmsg, inlen, dmp, outlenp) + void *state; + u_char *cmsg, *dmp; + int inlen, *outlenp; +{ + struct bsd_db *db = (struct bsd_db *) state; + u_int max_ent = db->max_ent; + u_int32_t accm = 0; + u_int bitno = 32; /* 1st valid bit in accm */ + u_int n_bits = db->n_bits; + u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ + struct bsd_dict *dictp; + int explen, i, seq, len; + u_int incode, oldcode, finchar; + u_char *p, *rptr, *wptr; + int ilen; + int dlen, space, codelen, extra; + + rptr = cmsg; + if (*rptr == 0) + ++rptr; + ++rptr; /* skip protocol (assumed 0xfd) */ + seq = (rptr[0] << 8) + rptr[1]; + rptr += BSD_OVHD; + ilen = len = cmsg + inlen - rptr; + + /* + * Check the sequence number and give up if it is not what we expect. + */ + if (seq != db->seqno++) { + if (db->debug) + printf("bsd_decomp%d: bad sequence # %d, expected %d\n", + db->unit, seq, db->seqno - 1); + return DECOMP_ERROR; + } + + wptr = dmp + db->hdrlen; + + oldcode = CLEAR; + explen = 0; + while (len > 0) { + /* + * 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 |= *rptr++ << bitno; + --len; + if (tgtbitno < bitno) + continue; + incode = accm >> tgtbitno; + accm <<= n_bits; + bitno += n_bits; + + if (incode == CLEAR) { + /* + * The dictionary must only be cleared at + * the end of a packet. But there could be an + * empty message block at the end. + */ + if (len > 0) { + if (db->debug) + printf("bsd_decomp%d: bad CLEAR\n", db->unit); + return DECOMP_FATALERROR; + } + bsd_clear(db); + explen = ilen = 0; + break; + } + + if (incode > max_ent + 2 || incode > db->maxmaxcode + || incode > max_ent && oldcode == CLEAR) { + if (db->debug) { + printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", + db->unit, incode, oldcode); + printf("max_ent=0x%x dlen=%d seqno=%d\n", + max_ent, dlen, 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 = db->lens[finchar]; + explen += codelen + extra; + if (explen > db->mru + 1) { + if (db->debug) + printf("bsd_decomp%d: ran out of mru\n", db->unit); + return DECOMP_FATALERROR; + } + + /* + * Decode this code and install it in the decompressed buffer. + */ + p = (wptr += codelen); + while (finchar > LAST) { + dictp = &db->dict[db->dict[finchar].cptr]; +#ifdef DEBUG + --codelen; + if (codelen <= 0) { + printf("bsd_decomp%d: fell off end of chain ", db->unit); + printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", + incode, finchar, db->dict[finchar].cptr, max_ent); + return DECOMP_FATALERROR; + } + if (dictp->codem1 != finchar-1) { + printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", + db->unit, incode, finchar); + printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, + db->dict[finchar].cptr, dictp->codem1); + return DECOMP_FATALERROR; + } +#endif + *--p = dictp->f.hs.suffix; + finchar = dictp->f.hs.prefix; + } + *--p = finchar; + +#ifdef DEBUG + if (--codelen != 0) + printf("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; + u_int32_t fcode; + int hval, disp; + + fcode = BSD_KEY(oldcode,finchar); + hval = BSD_HASH(oldcode,finchar,db->hshift); + dictp = &db->dict[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 = &db->dict[hval]; + } while (dictp->codem1 < max_ent); + } + + /* + * Invalidate previous hash table entry + * assigned this code, and then take it over + */ + dictp2 = &db->dict[max_ent+1]; + if (db->dict[dictp2->cptr].codem1 == max_ent) { + db->dict[dictp2->cptr].codem1 = BADCODEM1; + } + dictp2->cptr = hval; + dictp->codem1 = max_ent; + dictp->f.fcode = fcode; + + db->max_ent = ++max_ent; + db->lens[max_ent] = db->lens[oldcode]+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; + } + *outlenp = wptr - (dmp + db->hdrlen); + + /* + * Keep the checkpoint right so that incompressible packets + * clear the dictionary at the right times. + */ + db->bytes_out += ilen; + db->in_count += explen; + if (bsd_check(db) && db->debug) { + printf("bsd_decomp%d: peer should have cleared dictionary\n", + db->unit); + } + + ++db->comp_count; + db->comp_bytes += ilen + BSD_OVHD; + ++db->uncomp_count; + db->uncomp_bytes += explen; + + return DECOMP_OK; +} +#endif /* DO_BSD_COMPRESS */ |