/* * BSD compression module * * Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp * The whole module is now SKB based. * */ /* * Update: The Berkeley copyright was changed, and the change * is retroactive to all "true" BSD software (ie everything * from UCB as opposed to other peoples code that just carried * the same license). The new copyright doesn't clash with the * GPL, so the module-only restriction has been removed.. */ /* * Original copyright notice: * * 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. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* used in new tty drivers */ #include /* used in new tty drivers */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "isdn_ppp.h" MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN"); MODULE_LICENSE("Dual BSD/GPL"); #define BSD_VERSION(x) ((x) >> 5) #define BSD_NBITS(x) ((x) & 0x1F) #define BSD_CURRENT_VERSION 1 #define DEBUG 1 /* * A dictionary for doing BSD compress. */ struct bsd_dict { u32 fcode; u16 codem1; /* output of hash table -1 */ u16 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 */ u16 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 */ int xmit; }; #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 /* * 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) /* * 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_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,unsigned char code, unsigned char id, unsigned char *data, unsigned len, struct isdn_ppp_resetparams *rsparm) { 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 */ vfree(db->dict); db->dict = NULL; /* * Release the string buffer */ vfree(db->lens); db->lens = NULL; /* * Finally release the structure itself. */ kfree(db); } } /* * Allocate space for a (de) compressor. */ static void *bsd_alloc (struct isdn_ppp_comp_data *data) { int bits; unsigned int hsize, hshift, maxmaxcode; struct bsd_db *db; int decomp; static unsigned int htab[][2] = { { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 } }; if (data->optlen != 1 || data->num != CI_BSD_COMPRESS || BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION) return NULL; bits = BSD_NBITS(data->options[0]); if(bits < 9 || bits > 15) return NULL; hsize = htab[bits-9][0]; hshift = htab[bits-9][1]; /* * Allocate the main control structure for this instance. */ maxmaxcode = MAXCODE(bits); db = kzalloc (sizeof (struct bsd_db),GFP_KERNEL); if (!db) return NULL; db->xmit = data->flags & IPPP_COMP_FLAG_XMIT; decomp = db->xmit ? 0 : 1; /* * 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; } /* * If this is the compression buffer then there is no length data. * For decompression, the length information is needed as well. */ if (!decomp) db->lens = NULL; 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; } /* * Initialize the database. */ static int bsd_init (void *state, struct isdn_ppp_comp_data *data, int unit, int debug) { struct bsd_db *db = state; int indx; int decomp; if(!state || !data) { printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n",unit,(long)state,(long)data); return 0; } decomp = db->xmit ? 0 : 1; if (data->optlen != 1 || data->num != CI_BSD_COMPRESS || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION) || (BSD_NBITS(data->options[0]) != db->maxbits) || (decomp && db->lens == NULL)) { printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n",data->optlen,data->num,data->options[0],decomp,(unsigned long)db->lens); return 0; } if (decomp) for(indx=LAST;indx>=0;indx--) db->lens[indx] = 1; indx = db->hsize; while (indx-- != 0) { db->dict[indx].codem1 = BADCODEM1; db->dict[indx].cptr = 0; } db->unit = unit; db->mru = 0; db->debug = 1; bsd_reset(db,0,0,NULL,0,NULL); return 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 (KERN_DEBUG "<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 (KERN_DEBUG "<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 */ static int bsd_compress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,int proto) { 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,disp,ilen,mxcode; unsigned char *rptr = skb_in->data; int isize = skb_in->len; #define OUTPUT(ent) \ { \ bitno -= n_bits; \ accm |= ((ent) << bitno); \ do { \ if(skb_out && skb_tailroom(skb_out) > 0) \ *(skb_put(skb_out,1)) = (unsigned char) (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. */ printk(KERN_DEBUG "bsd_compress called with %x\n",proto); ent = proto; if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1) ) 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); /* This is the PPP header information */ if(skb_out && skb_tailroom(skb_out) >= 2) { char *v = skb_put(skb_out,2); /* we only push our own data on the header, AC,PC and protos is pushed by caller */ v[0] = db->seqno >> 8; v[1] = db->seqno; } 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->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->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->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 */ if(skb_out) db->bytes_out += skb_out->len; /* 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 && skb_out && skb_tailroom(skb_out) > 0) *(skb_put(skb_out,1)) = (unsigned char) ((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 incompressible frame. */ if (!skb_out || (skb_out && skb_out->len >= skb_in->len) ) { ++db->incomp_count; db->incomp_bytes += isize; return 0; } /* Count the number of compressed frames */ ++db->comp_count; db->comp_bytes += skb_out->len; return skb_out->len; #undef OUTPUT } /* * Update the "BSD Compress" dictionary on the receiver for * incompressible data by pretending to compress the incoming data. */ static void bsd_incomp (void *state, struct sk_buff *skb_in,int proto) { bsd_compress (state, skb_in, NULL, proto); } /* * Decompress "BSD Compress". */ static int bsd_decompress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out, struct isdn_ppp_resetparams *rsparm) { 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 seq; unsigned int incode; unsigned int oldcode; unsigned int finchar; unsigned char *p,*ibuf; 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 */ printk(KERN_DEBUG "bsd_decompress called\n"); if(!skb_in || !skb_out) { printk(KERN_ERR "bsd_decompress called with NULL parameter\n"); return DECOMP_ERROR; } /* * Get the sequence number. */ if( (p = skb_pull(skb_in,2)) == NULL) { return DECOMP_ERROR; } p-=2; seq = (p[0] << 8) + p[1]; ilen = skb_in->len; ibuf = skb_in->data; /* * Check the sequence number and give up if it differs from * the value we're expecting. */ if (seq != db->seqno) { if (db->debug) { printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n", db->unit, seq, db->seqno - 1); } return DECOMP_ERROR; } ++db->seqno; db->bytes_out += ilen; if(skb_tailroom(skb_out) > 0) *(skb_put(skb_out,1)) = 0; else return DECOMP_ERR_NOMEM; oldcode = CLEAR; /* * Keep the checkpoint correctly so that incompressible packets * clear the dictionary at the proper times. */ for (;;) { if (ilen-- <= 0) { db->in_count += (skb_out->len - 1); /* 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(KERN_DEBUG "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(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ", db->unit, incode, oldcode); printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n", max_ent, skb_out->len, 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)); if( skb_tailroom(skb_out) < codelen + extra) { if (db->debug) { printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit); #ifdef DEBUG printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n", ilen, finchar, codelen, skb_out->len); #endif } return DECOMP_FATALERROR; } /* * Decode this code and install it in the decompressed buffer. */ p = skb_put(skb_out,codelen); p += codelen; 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(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit); printk(KERN_ERR "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(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",db->unit, incode, finchar); printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1); } } return DECOMP_FATALERROR; } #endif { u32 fcode = dictp->fcode; *--p = (fcode >> 16) & 0xff; finchar = fcode & 0xffff; } } *--p = finchar; #ifdef DEBUG if (--codelen != 0) printk(KERN_ERR "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 */ *(skb_put(skb_out,1)) = 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; u16 *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->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 += skb_in->len - BSD_OVHD; db->uncomp_bytes += skb_out->len; if (bsd_check(db)) { if (db->debug) printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n", db->unit, db->seqno - 1); } return skb_out->len; } /************************************************************* * Table of addresses for the BSD compression module *************************************************************/ static struct isdn_ppp_compressor ippp_bsd_compress = { .owner = THIS_MODULE, .num = CI_BSD_COMPRESS, .alloc = bsd_alloc, .free = bsd_free, .init = bsd_init, .reset = bsd_reset, .compress = bsd_compress, .decompress = bsd_decompress, .incomp = bsd_incomp, .stat = bsd_stats, }; /************************************************************* * Module support routines *************************************************************/ static int __init isdn_bsdcomp_init(void) { int answer = isdn_ppp_register_compressor (&ippp_bsd_compress); if (answer == 0) printk (KERN_INFO "PPP BSD Compression module registered\n"); return answer; } static void __exit isdn_bsdcomp_exit(void) { isdn_ppp_unregister_compressor (&ippp_bsd_compress); } module_init(isdn_bsdcomp_init); module_exit(isdn_bsdcomp_exit);