The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/netgraph/ng_pred1.c

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    1 /*-
    2  * Copyright (c) 2006 Alexander Motin <mav@alkar.net>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice unmodified, this list of conditions, and the following
   10  *    disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   25  * SUCH DAMAGE.
   26  *
   27  * $FreeBSD: releng/10.1/sys/netgraph/ng_pred1.c 243882 2012-12-05 08:04:20Z glebius $
   28  */
   29 
   30 /*
   31  * Predictor-1 PPP compression netgraph node type.
   32  */
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/kernel.h>
   37 #include <sys/mbuf.h>
   38 #include <sys/malloc.h>
   39 #include <sys/errno.h>
   40 #include <sys/syslog.h>
   41 
   42 #include <netgraph/ng_message.h>
   43 #include <netgraph/netgraph.h>
   44 #include <netgraph/ng_parse.h>
   45 #include <netgraph/ng_pred1.h>
   46 
   47 #include "opt_netgraph.h"
   48 
   49 static MALLOC_DEFINE(M_NETGRAPH_PRED1, "netgraph_pred1", "netgraph pred1 node");
   50 
   51 /* PRED1 header length */
   52 #define PRED1_HDRLEN            2
   53 
   54 #define PRED1_TABLE_SIZE        0x10000
   55 #define PRED1_BUF_SIZE          4096
   56 #define PPP_INITFCS             0xffff  /* Initial FCS value */
   57 #define PPP_GOODFCS             0xf0b8  /* Good final FCS value */
   58 
   59 /*
   60  * The following hash code is the heart of the algorithm:
   61  * it builds a sliding hash sum of the previous 3-and-a-bit
   62  * characters which will be used to index the guess table.
   63  * A better hash function would result in additional compression,
   64  * at the expense of time.
   65  */
   66 
   67 #define HASH(x) priv->Hash = (priv->Hash << 4) ^ (x)
   68 
   69 /* Node private data */
   70 struct ng_pred1_private {
   71         struct ng_pred1_config cfg;             /* configuration */
   72         u_char          GuessTable[PRED1_TABLE_SIZE];   /* dictionary */
   73         u_char          inbuf[PRED1_BUF_SIZE];  /* input buffer */
   74         u_char          outbuf[PRED1_BUF_SIZE]; /* output buffer */
   75         struct ng_pred1_stats stats;            /* statistics */
   76         uint16_t        Hash;
   77         ng_ID_t         ctrlnode;               /* path to controlling node */
   78         uint16_t        seqnum;                 /* sequence number */
   79         u_char          compress;               /* compress/decompress flag */
   80 };
   81 typedef struct ng_pred1_private *priv_p;
   82 
   83 /* Netgraph node methods */
   84 static ng_constructor_t ng_pred1_constructor;
   85 static ng_rcvmsg_t      ng_pred1_rcvmsg;
   86 static ng_shutdown_t    ng_pred1_shutdown;
   87 static ng_newhook_t     ng_pred1_newhook;
   88 static ng_rcvdata_t     ng_pred1_rcvdata;
   89 static ng_disconnect_t  ng_pred1_disconnect;
   90 
   91 /* Helper functions */
   92 static int      ng_pred1_compress(node_p node, struct mbuf *m,
   93                     struct mbuf **resultp);
   94 static int      ng_pred1_decompress(node_p node, struct mbuf *m,
   95                     struct mbuf **resultp);
   96 static void     Pred1Init(node_p node);
   97 static int      Pred1Compress(node_p node, u_char *source, u_char *dest,
   98                     int len);
   99 static int      Pred1Decompress(node_p node, u_char *source, u_char *dest,
  100                     int slen, int dlen);
  101 static void     Pred1SyncTable(node_p node, u_char *source, int len);
  102 static uint16_t Crc16(uint16_t fcs, u_char *cp, int len);
  103 
  104 static const uint16_t   Crc16Table[];
  105 
  106 /* Parse type for struct ng_pred1_config. */
  107 static const struct ng_parse_struct_field ng_pred1_config_type_fields[]
  108         = NG_PRED1_CONFIG_INFO;
  109 static const struct ng_parse_type ng_pred1_config_type = {
  110         &ng_parse_struct_type,
  111         ng_pred1_config_type_fields
  112 };
  113 
  114 /* Parse type for struct ng_pred1_stat. */
  115 static const struct ng_parse_struct_field ng_pred1_stats_type_fields[]
  116         = NG_PRED1_STATS_INFO;
  117 static const struct ng_parse_type ng_pred1_stat_type = {
  118         &ng_parse_struct_type,
  119         ng_pred1_stats_type_fields
  120 };
  121 
  122 /* List of commands and how to convert arguments to/from ASCII. */
  123 static const struct ng_cmdlist ng_pred1_cmds[] = {
  124         {
  125           NGM_PRED1_COOKIE,
  126           NGM_PRED1_CONFIG,
  127           "config",
  128           &ng_pred1_config_type,
  129           NULL
  130         },
  131         {
  132           NGM_PRED1_COOKIE,
  133           NGM_PRED1_RESETREQ,
  134           "resetreq",
  135           NULL,
  136           NULL
  137         },
  138         {
  139           NGM_PRED1_COOKIE,
  140           NGM_PRED1_GET_STATS,
  141           "getstats",
  142           NULL,
  143           &ng_pred1_stat_type
  144         },
  145         {
  146           NGM_PRED1_COOKIE,
  147           NGM_PRED1_CLR_STATS,
  148           "clrstats",
  149           NULL,
  150           NULL
  151         },
  152         {
  153           NGM_PRED1_COOKIE,
  154           NGM_PRED1_GETCLR_STATS,
  155           "getclrstats",
  156           NULL,
  157           &ng_pred1_stat_type
  158         },
  159         { 0 }
  160 };
  161 
  162 /* Node type descriptor */
  163 static struct ng_type ng_pred1_typestruct = {
  164         .version =      NG_ABI_VERSION,
  165         .name =         NG_PRED1_NODE_TYPE,
  166         .constructor =  ng_pred1_constructor,
  167         .rcvmsg =       ng_pred1_rcvmsg,
  168         .shutdown =     ng_pred1_shutdown,
  169         .newhook =      ng_pred1_newhook,
  170         .rcvdata =      ng_pred1_rcvdata,
  171         .disconnect =   ng_pred1_disconnect,
  172         .cmdlist =      ng_pred1_cmds,
  173 };
  174 NETGRAPH_INIT(pred1, &ng_pred1_typestruct);
  175 
  176 #define ERROUT(x)       do { error = (x); goto done; } while (0)
  177 
  178 /************************************************************************
  179                         NETGRAPH NODE STUFF
  180  ************************************************************************/
  181 
  182 /*
  183  * Node type constructor
  184  */
  185 static int
  186 ng_pred1_constructor(node_p node)
  187 {
  188         priv_p priv;
  189 
  190         /* Allocate private structure. */
  191         priv = malloc(sizeof(*priv), M_NETGRAPH_PRED1, M_WAITOK | M_ZERO);
  192 
  193         NG_NODE_SET_PRIVATE(node, priv);
  194 
  195         /* This node is not thread safe. */
  196         NG_NODE_FORCE_WRITER(node);
  197 
  198         /* Done */
  199         return (0);
  200 }
  201 
  202 /*
  203  * Give our OK for a hook to be added.
  204  */
  205 static int
  206 ng_pred1_newhook(node_p node, hook_p hook, const char *name)
  207 {
  208         const priv_p priv = NG_NODE_PRIVATE(node);
  209 
  210         if (NG_NODE_NUMHOOKS(node) > 0)
  211                 return (EINVAL);
  212 
  213         if (strcmp(name, NG_PRED1_HOOK_COMP) == 0)
  214                 priv->compress = 1;
  215         else if (strcmp(name, NG_PRED1_HOOK_DECOMP) == 0)
  216                 priv->compress = 0;
  217         else
  218                 return (EINVAL);
  219 
  220         return (0);
  221 }
  222 
  223 /*
  224  * Receive a control message.
  225  */
  226 static int
  227 ng_pred1_rcvmsg(node_p node, item_p item, hook_p lasthook)
  228 {
  229         const priv_p priv = NG_NODE_PRIVATE(node);
  230         struct ng_mesg *resp = NULL;
  231         int error = 0;
  232         struct ng_mesg *msg;
  233 
  234         NGI_GET_MSG(item, msg);
  235 
  236         if (msg->header.typecookie != NGM_PRED1_COOKIE)
  237                 ERROUT(EINVAL);
  238 
  239         switch (msg->header.cmd) {
  240         case NGM_PRED1_CONFIG:
  241             {
  242                 struct ng_pred1_config *const cfg =
  243                     (struct ng_pred1_config *)msg->data;
  244 
  245                 /* Check configuration. */
  246                 if (msg->header.arglen != sizeof(*cfg))
  247                         ERROUT(EINVAL);
  248 
  249                 /* Configuration is OK, reset to it. */
  250                 priv->cfg = *cfg;
  251 
  252                 /* Save return address so we can send reset-req's. */
  253                 priv->ctrlnode = NGI_RETADDR(item);
  254 
  255                 /* Clear our state. */
  256                 Pred1Init(node);
  257 
  258                 break;
  259             }
  260         case NGM_PRED1_RESETREQ:
  261                 Pred1Init(node);
  262                 break;
  263 
  264         case NGM_PRED1_GET_STATS:
  265         case NGM_PRED1_CLR_STATS:
  266         case NGM_PRED1_GETCLR_STATS:
  267             {
  268                 /* Create response. */
  269                 if (msg->header.cmd != NGM_PRED1_CLR_STATS) {
  270                         NG_MKRESPONSE(resp, msg,
  271                             sizeof(struct ng_pred1_stats), M_NOWAIT);
  272                         if (resp == NULL)
  273                                 ERROUT(ENOMEM);
  274                         bcopy(&priv->stats, resp->data,
  275                             sizeof(struct ng_pred1_stats));
  276                 }
  277 
  278                 if (msg->header.cmd != NGM_PRED1_GET_STATS)
  279                         bzero(&priv->stats, sizeof(struct ng_pred1_stats));
  280                 break;
  281             }
  282 
  283         default:
  284                 error = EINVAL;
  285                 break;
  286         }
  287 done:
  288         NG_RESPOND_MSG(error, node, item, resp);
  289         NG_FREE_MSG(msg);
  290         return (error);
  291 }
  292 
  293 /*
  294  * Receive incoming data on our hook.
  295  */
  296 static int
  297 ng_pred1_rcvdata(hook_p hook, item_p item)
  298 {
  299         const node_p node = NG_HOOK_NODE(hook);
  300         const priv_p priv = NG_NODE_PRIVATE(node);
  301         struct mbuf *m, *out;
  302         int error;
  303 
  304         if (!priv->cfg.enable) {
  305                 NG_FREE_ITEM(item);
  306                 return (ENXIO);
  307         }
  308 
  309         NGI_GET_M(item, m);
  310         /* Compress. */
  311         if (priv->compress) {
  312                 if ((error = ng_pred1_compress(node, m, &out)) != 0) {
  313                         NG_FREE_ITEM(item);
  314                         log(LOG_NOTICE, "%s: error: %d\n", __func__, error);
  315                         return (error);
  316                 }
  317 
  318         } else { /* Decompress. */
  319                 if ((error = ng_pred1_decompress(node, m, &out)) != 0) {
  320                         NG_FREE_ITEM(item);
  321                         log(LOG_NOTICE, "%s: error: %d\n", __func__, error);
  322                         if (priv->ctrlnode != 0) {
  323                                 struct ng_mesg *msg;
  324 
  325                                 /* Need to send a reset-request. */
  326                                 NG_MKMESSAGE(msg, NGM_PRED1_COOKIE,
  327                                     NGM_PRED1_RESETREQ, 0, M_NOWAIT);
  328                                 if (msg == NULL)
  329                                         return (error);
  330                                 NG_SEND_MSG_ID(error, node, msg,
  331                                     priv->ctrlnode, 0);
  332                         }
  333                         return (error);
  334                 }
  335         }
  336 
  337         NG_FWD_NEW_DATA(error, item, hook, out);
  338         return (error);
  339 }
  340 
  341 /*
  342  * Destroy node.
  343  */
  344 static int
  345 ng_pred1_shutdown(node_p node)
  346 {
  347         const priv_p priv = NG_NODE_PRIVATE(node);
  348 
  349         free(priv, M_NETGRAPH_PRED1);
  350         NG_NODE_SET_PRIVATE(node, NULL);
  351         NG_NODE_UNREF(node);            /* Let the node escape. */
  352         return (0);
  353 }
  354 
  355 /*
  356  * Hook disconnection
  357  */
  358 static int
  359 ng_pred1_disconnect(hook_p hook)
  360 {
  361         const node_p node = NG_HOOK_NODE(hook);
  362 
  363         Pred1Init(node);
  364 
  365         /* Go away if no longer connected. */
  366         if ((NG_NODE_NUMHOOKS(node) == 0) && NG_NODE_IS_VALID(node))
  367                 ng_rmnode_self(node);
  368         return (0);
  369 }
  370 
  371 /************************************************************************
  372                         HELPER STUFF
  373  ************************************************************************/
  374 
  375 /*
  376  * Compress/encrypt a packet and put the result in a new mbuf at *resultp.
  377  * The original mbuf is not free'd.
  378  */
  379 static int
  380 ng_pred1_compress(node_p node, struct mbuf *m, struct mbuf **resultp)
  381 {
  382         const priv_p    priv = NG_NODE_PRIVATE(node);
  383         int             outlen, inlen;
  384         u_char          *out;
  385         uint16_t        fcs, lenn;
  386         int             len;
  387 
  388         /* Initialize. */
  389         *resultp = NULL;
  390 
  391         inlen = m->m_pkthdr.len;
  392 
  393         priv->stats.FramesPlain++;
  394         priv->stats.InOctets += inlen;
  395 
  396         /* Reserve space for expansion. */
  397         if (inlen > (PRED1_BUF_SIZE*8/9 + 1 + 4)) {
  398                 priv->stats.Errors++;
  399                 NG_FREE_M(m);
  400                 return (ENOMEM);
  401         }
  402 
  403         /* We must own the mbuf chain exclusively to modify it. */
  404         m = m_unshare(m, M_NOWAIT);
  405         if (m == NULL) {
  406                 priv->stats.Errors++;
  407                 return (ENOMEM);
  408         }
  409 
  410         /* Work with contiguous regions of memory. */
  411         m_copydata(m, 0, inlen, (caddr_t)(priv->inbuf + 2));
  412 
  413         lenn = htons(inlen & 0x7FFF);
  414 
  415         /* Compute FCS. */
  416         fcs = Crc16(PPP_INITFCS, (u_char *)&lenn, 2);
  417         fcs = Crc16(fcs, priv->inbuf + 2, inlen);
  418         fcs = ~fcs;
  419 
  420         /* Compress data. */
  421         len = Pred1Compress(node, priv->inbuf + 2, priv->outbuf + 2, inlen);
  422 
  423         /* What happened? */
  424         if (len < inlen) {
  425                 out = priv->outbuf;
  426                 outlen = 2 + len;
  427                 *(uint16_t *)out = lenn;
  428                 *out |= 0x80;
  429                 priv->stats.FramesComp++;
  430         } else {
  431                 out = priv->inbuf;
  432                 outlen = 2 + inlen;
  433                 *(uint16_t *)out = lenn;
  434                 priv->stats.FramesUncomp++;
  435         }
  436 
  437         /* Add FCS. */
  438         (out + outlen)[0] = fcs & 0xFF;
  439         (out + outlen)[1] = fcs >> 8;
  440 
  441         /* Calculate resulting size. */
  442         outlen += 2;
  443 
  444         /* Return packet in an mbuf. */
  445         m_copyback(m, 0, outlen, (caddr_t)out);
  446         if (m->m_pkthdr.len < outlen) {
  447                 m_freem(m);
  448                 priv->stats.Errors++;
  449                 return (ENOMEM);
  450         } else if (outlen < m->m_pkthdr.len)
  451                 m_adj(m, outlen - m->m_pkthdr.len);
  452         *resultp = m;
  453         priv->stats.OutOctets += outlen;
  454 
  455         return (0);
  456 }
  457 
  458 /*
  459  * Decompress/decrypt packet and put the result in a new mbuf at *resultp.
  460  * The original mbuf is not free'd.
  461  */
  462 static int
  463 ng_pred1_decompress(node_p node, struct mbuf *m, struct mbuf **resultp)
  464 {
  465         const priv_p    priv = NG_NODE_PRIVATE(node);
  466         int             inlen;
  467         uint16_t        len, len1, cf, lenn;
  468         uint16_t        fcs;
  469 
  470         /* Initialize. */
  471         *resultp = NULL;
  472 
  473         inlen = m->m_pkthdr.len;
  474 
  475         if (inlen > PRED1_BUF_SIZE) {
  476                 priv->stats.Errors++;
  477                 NG_FREE_M(m);
  478                 return (ENOMEM);
  479         }
  480 
  481         /* We must own the mbuf chain exclusively to modify it. */
  482         m = m_unshare(m, M_NOWAIT);
  483         if (m == NULL) {
  484                 priv->stats.Errors++;
  485                 return (ENOMEM);
  486         }
  487 
  488         /* Work with contiguous regions of memory. */
  489         m_copydata(m, 0, inlen, (caddr_t)priv->inbuf);
  490 
  491         priv->stats.InOctets += inlen;
  492 
  493         /* Get initial length value. */
  494         len = priv->inbuf[0] << 8;
  495         len += priv->inbuf[1];
  496 
  497         cf = (len & 0x8000);
  498         len &= 0x7fff;
  499 
  500         /* Is data compressed or not really? */
  501         if (cf) {
  502                 priv->stats.FramesComp++;
  503                 len1 = Pred1Decompress(node, priv->inbuf + 2, priv->outbuf,
  504                     inlen - 4, PRED1_BUF_SIZE);
  505                 if (len != len1) {
  506                         /* Error is detected. Send reset request */
  507                         m_freem(m);
  508                         priv->stats.Errors++;
  509                         log(LOG_NOTICE, "ng_pred1: Comp length error (%d) "
  510                             "--> len (%d)\n", len, len1);
  511                         return (EIO);
  512                 }
  513 
  514                 /*
  515                  * CRC check on receive is defined in RFC. It is surely required
  516                  * for compressed frames to signal dictionary corruption,
  517                  * but it is actually useless for uncompressed frames because
  518                  * the same check has already done by HDLC and/or other layer.
  519                  */
  520                 lenn = htons(len);
  521                 fcs = Crc16(PPP_INITFCS, (u_char *)&lenn, 2);
  522                 fcs = Crc16(fcs, priv->outbuf, len);
  523                 fcs = Crc16(fcs, priv->inbuf + inlen - 2, 2);
  524 
  525                 if (fcs != PPP_GOODFCS) {
  526                         m_freem(m);
  527                         priv->stats.Errors++;
  528                         log(LOG_NOTICE, "ng_pred1: Pred1: Bad CRC-16\n");
  529                         return (EIO);
  530                 }
  531 
  532                 /* Return packet in an mbuf. */
  533                 m_copyback(m, 0, len, (caddr_t)priv->outbuf);
  534                 if (m->m_pkthdr.len < len) {
  535                         m_freem(m);
  536                         priv->stats.Errors++;
  537                         return (ENOMEM);
  538                 } else if (len < m->m_pkthdr.len)
  539                         m_adj(m, len - m->m_pkthdr.len);
  540                 *resultp = m;
  541 
  542         } else {
  543                 priv->stats.FramesUncomp++;
  544                 if (len != (inlen - 4)) {
  545                         /* Wrong length. Send reset request */
  546                         priv->stats.Errors++;
  547                         log(LOG_NOTICE, "ng_pred1: Uncomp length error (%d) "
  548                             "--> len (%d)\n", len, inlen - 4);
  549                         NG_FREE_M(m);
  550                         return (EIO);
  551                 }
  552                 Pred1SyncTable(node, priv->inbuf + 2, len);
  553                 m_adj(m, 2);    /* Strip length. */
  554                 m_adj(m, -2);   /* Strip fcs. */
  555                 *resultp = m;
  556         }
  557 
  558         priv->stats.FramesPlain++;
  559         priv->stats.OutOctets += len;
  560 
  561         return (0);
  562 }
  563 
  564 /*
  565  * Pred1Init()
  566  */
  567 
  568 static void
  569 Pred1Init(node_p node)
  570 {
  571         const priv_p priv = NG_NODE_PRIVATE(node);
  572 
  573         priv->Hash = 0;
  574         memset(priv->GuessTable, 0, PRED1_TABLE_SIZE);
  575 }
  576 
  577 /*
  578  * Pred1Compress()
  579  */
  580 
  581 static int
  582 Pred1Compress(node_p node, u_char *source, u_char *dest, int len)
  583 {
  584         const priv_p    priv = NG_NODE_PRIVATE(node);
  585         int             i;
  586         u_char          flags;
  587         u_char          *flagdest, *orgdest;
  588 
  589         orgdest = dest;
  590         while (len) {
  591                 flagdest = dest++;
  592                 flags = 0;      /* All guesses are wrong initially. */
  593                 for (i = 0; i < 8 && len; i++) {
  594                         if (priv->GuessTable[priv->Hash] == *source)
  595                                 /* Guess was right - don't output. */
  596                                 flags |= (1 << i);
  597                         else {
  598                                 /* Guess wrong, output char. */
  599                                 priv->GuessTable[priv->Hash] = *source;
  600                                 *dest++ = *source;
  601                         }
  602                         HASH(*source++);
  603                         len--;
  604                 }
  605                 *flagdest = flags;
  606         }
  607         return (dest - orgdest);
  608 }
  609 
  610 /*
  611  * Pred1Decompress()
  612  *
  613  * Returns decompressed size, or -1 if we ran out of space.
  614  */
  615 
  616 static int
  617 Pred1Decompress(node_p node, u_char *source, u_char *dest, int slen, int dlen)
  618 {
  619         const priv_p    priv = NG_NODE_PRIVATE(node);
  620         int             i;
  621         u_char          flags, *orgdest;
  622 
  623         orgdest = dest;
  624         while (slen) {
  625                 flags = *source++;
  626                 slen--;
  627                 for (i = 0; i < 8; i++, flags >>= 1) {
  628                         if (dlen <= 0)
  629                                 return(-1);
  630                         if (flags & 0x01)
  631                                 /* Guess correct */
  632                                 *dest = priv->GuessTable[priv->Hash];
  633                         else {
  634                                 if (!slen)
  635                                         /* We seem to be really done -- cabo. */
  636                                         break;
  637 
  638                                 /* Guess wrong. */
  639                                 priv->GuessTable[priv->Hash] = *source;
  640                                 /* Read from source. */
  641                                 *dest = *source++;
  642                                 slen--;
  643                         }
  644                         HASH(*dest++);
  645                         dlen--;
  646                 }
  647         }
  648         return (dest - orgdest);
  649 }
  650 
  651 /*
  652  * Pred1SyncTable()
  653  */
  654 
  655 static void
  656 Pred1SyncTable(node_p node, u_char *source, int len)
  657 {
  658         const priv_p priv = NG_NODE_PRIVATE(node);
  659 
  660         while (len--) {
  661                 priv->GuessTable[priv->Hash] = *source;
  662                 HASH(*source++);
  663         }
  664 }
  665 
  666 /*
  667  * Crc16()
  668  *
  669  * Compute the 16 bit frame check value, per RFC 1171 Appendix B,
  670  * on an array of bytes.
  671  */
  672 
  673 static uint16_t
  674 Crc16(uint16_t crc, u_char *cp, int len)
  675 {
  676         while (len--)
  677                 crc = (crc >> 8) ^ Crc16Table[(crc ^ *cp++) & 0xff];
  678         return (crc);
  679 }
  680 
  681 static const uint16_t Crc16Table[256] = {
  682 /* 00 */    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
  683 /* 08 */    0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
  684 /* 10 */    0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
  685 /* 18 */    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
  686 /* 20 */    0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
  687 /* 28 */    0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
  688 /* 30 */    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
  689 /* 38 */    0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
  690 /* 40 */    0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
  691 /* 48 */    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
  692 /* 50 */    0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
  693 /* 58 */    0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
  694 /* 60 */    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
  695 /* 68 */    0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
  696 /* 70 */    0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
  697 /* 78 */    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
  698 /* 80 */    0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
  699 /* 88 */    0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
  700 /* 90 */    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
  701 /* 98 */    0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
  702 /* a0 */    0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
  703 /* a8 */    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
  704 /* b0 */    0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
  705 /* b8 */    0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
  706 /* c0 */    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
  707 /* c8 */    0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
  708 /* d0 */    0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
  709 /* d8 */    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
  710 /* e0 */    0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
  711 /* e8 */    0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
  712 /* f0 */    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
  713 /* f8 */    0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
  714 };
  715 

Cache object: d98f2354e0578d8453bfc8df8fceee31


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