The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/net/slcompress.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*      $NetBSD: slcompress.c,v 1.26 2004/12/06 02:59:23 christos Exp $   */
    2 /*      Id: slcompress.c,v 1.3 1996/05/24 07:04:47 paulus Exp   */
    3 
    4 /*
    5  * Copyright (c) 1989, 1993, 1994
    6  *      The Regents of the University of California.  All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)slcompress.c        8.2 (Berkeley) 4/16/94
   33  */
   34 
   35 /*
   36  * Routines to compress and uncompess tcp packets (for transmission
   37  * over low speed serial lines.
   38  *
   39  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
   40  *      - Initial distribution.
   41  */
   42 
   43 #include <sys/cdefs.h>
   44 __KERNEL_RCSID(0, "$NetBSD: slcompress.c,v 1.26 2004/12/06 02:59:23 christos Exp $");
   45 
   46 #include "opt_inet.h"
   47 #ifdef INET
   48 #include <sys/param.h>
   49 #include <sys/mbuf.h>
   50 #include <sys/systm.h>
   51 
   52 #include <netinet/in.h>
   53 #include <netinet/in_systm.h>
   54 #include <netinet/ip.h>
   55 #include <netinet/tcp.h>
   56 
   57 #include <net/slcompress.h>
   58 
   59 #ifndef SL_NO_STATS
   60 #define INCR(counter) ++comp->counter;
   61 #else
   62 #define INCR(counter)
   63 #endif
   64 
   65 #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
   66 #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
   67 
   68 
   69 void
   70 sl_compress_init(comp)
   71         struct slcompress *comp;
   72 {
   73         u_int i;
   74         struct cstate *tstate = comp->tstate;
   75 
   76         memset((char *)comp, 0, sizeof(*comp));
   77         for (i = MAX_STATES - 1; i > 0; --i) {
   78                 tstate[i].cs_id = i;
   79                 tstate[i].cs_next = &tstate[i - 1];
   80         }
   81         tstate[0].cs_next = &tstate[MAX_STATES - 1];
   82         tstate[0].cs_id = 0;
   83         comp->last_cs = &tstate[0];
   84         comp->last_recv = 255;
   85         comp->last_xmit = 255;
   86         comp->flags = SLF_TOSS;
   87 }
   88 
   89 
   90 /*
   91  * Like sl_compress_init, but we get to specify the maximum connection
   92  * ID to use on transmission.
   93  */
   94 void
   95 sl_compress_setup(comp, max_state)
   96         struct slcompress *comp;
   97         int max_state;
   98 {
   99         u_int i;
  100         struct cstate *tstate = comp->tstate;
  101 
  102         if (max_state == -1) {
  103                 max_state = MAX_STATES - 1;
  104                 memset((char *)comp, 0, sizeof(*comp));
  105         } else {
  106                 /* Don't reset statistics */
  107                 memset((char *)comp->tstate, 0, sizeof(comp->tstate));
  108                 memset((char *)comp->rstate, 0, sizeof(comp->rstate));
  109         }
  110         for (i = max_state; i > 0; --i) {
  111                 tstate[i].cs_id = i;
  112                 tstate[i].cs_next = &tstate[i - 1];
  113         }
  114         tstate[0].cs_next = &tstate[max_state];
  115         tstate[0].cs_id = 0;
  116         comp->last_cs = &tstate[0];
  117         comp->last_recv = 255;
  118         comp->last_xmit = 255;
  119         comp->flags = SLF_TOSS;
  120 }
  121 
  122 
  123 /* ENCODE encodes a number that is known to be non-zero.  ENCODEZ
  124  * checks for zero (since zero has to be encoded in the long, 3 byte
  125  * form).
  126  */
  127 #define ENCODE(n) { \
  128         if ((u_int16_t)(n) >= 256) { \
  129                 *cp++ = 0; \
  130                 cp[1] = (n); \
  131                 cp[0] = (n) >> 8; \
  132                 cp += 2; \
  133         } else { \
  134                 *cp++ = (n); \
  135         } \
  136 }
  137 #define ENCODEZ(n) { \
  138         if ((u_int16_t)(n) >= 256 || (u_int16_t)(n) == 0) { \
  139                 *cp++ = 0; \
  140                 cp[1] = (n); \
  141                 cp[0] = (n) >> 8; \
  142                 cp += 2; \
  143         } else { \
  144                 *cp++ = (n); \
  145         } \
  146 }
  147 
  148 #define DECODEL(f) { \
  149         if (*cp == 0) {\
  150                 (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
  151                 cp += 3; \
  152         } else { \
  153                 (f) = htonl(ntohl(f) + (u_int32_t)*cp++); \
  154         } \
  155 }
  156 
  157 #define DECODES(f) { \
  158         if (*cp == 0) {\
  159                 (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
  160                 cp += 3; \
  161         } else { \
  162                 (f) = htons(ntohs(f) + (u_int32_t)*cp++); \
  163         } \
  164 }
  165 
  166 #define DECODEU(f) { \
  167         if (*cp == 0) {\
  168                 (f) = htons((cp[1] << 8) | cp[2]); \
  169                 cp += 3; \
  170         } else { \
  171                 (f) = htons((u_int32_t)*cp++); \
  172         } \
  173 }
  174 
  175 u_int
  176 sl_compress_tcp(m, ip, comp, compress_cid)
  177         struct mbuf *m;
  178         struct ip *ip;
  179         struct slcompress *comp;
  180         int compress_cid;
  181 {
  182         struct cstate *cs = comp->last_cs->cs_next;
  183         u_int hlen = ip->ip_hl;
  184         struct tcphdr *oth;
  185         struct tcphdr *th;
  186         u_int deltaS, deltaA;
  187         u_int changes = 0;
  188         u_char new_seq[16];
  189         u_char *cp = new_seq;
  190 
  191         /*
  192          * Bail if this is an IP fragment or if the TCP packet isn't
  193          * `compressible' (i.e., ACK isn't set or some other control bit is
  194          * set).  (We assume that the caller has already made sure the
  195          * packet is IP proto TCP).
  196          */
  197         if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40)
  198                 return (TYPE_IP);
  199 
  200         th = (struct tcphdr *)&((int32_t *)ip)[hlen];
  201         if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
  202                 return (TYPE_IP);
  203         /*
  204          * Packet is compressible -- we're going to send either a
  205          * COMPRESSED_TCP or UNCOMPRESSED_TCP packet.  Either way we need
  206          * to locate (or create) the connection state.  Special case the
  207          * most recently used connection since it's most likely to be used
  208          * again & we don't have to do any reordering if it's used.
  209          */
  210         INCR(sls_packets)
  211         if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
  212             ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
  213             *(int32_t *)th != ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl]) {
  214                 /*
  215                  * Wasn't the first -- search for it.
  216                  *
  217                  * States are kept in a circularly linked list with
  218                  * last_cs pointing to the end of the list.  The
  219                  * list is kept in lru order by moving a state to the
  220                  * head of the list whenever it is referenced.  Since
  221                  * the list is short and, empirically, the connection
  222                  * we want is almost always near the front, we locate
  223                  * states via linear search.  If we don't find a state
  224                  * for the datagram, the oldest state is (re-)used.
  225                  */
  226                 struct cstate *lcs;
  227                 struct cstate *lastcs = comp->last_cs;
  228 
  229                 do {
  230                         lcs = cs; cs = cs->cs_next;
  231                         INCR(sls_searches)
  232                         if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
  233                             && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
  234                             && *(int32_t *)th ==
  235                             ((int32_t *)&cs->cs_ip)[cs->cs_ip.ip_hl])
  236                                 goto found;
  237                 } while (cs != lastcs);
  238 
  239                 /*
  240                  * Didn't find it -- re-use oldest cstate.  Send an
  241                  * uncompressed packet that tells the other side what
  242                  * connection number we're using for this conversation.
  243                  * Note that since the state list is circular, the oldest
  244                  * state points to the newest and we only need to set
  245                  * last_cs to update the lru linkage.
  246                  */
  247                 INCR(sls_misses)
  248                 comp->last_cs = lcs;
  249                 hlen += th->th_off;
  250                 hlen <<= 2;
  251                 if (hlen > m->m_len)
  252                         return (TYPE_IP);
  253                 goto uncompressed;
  254 
  255         found:
  256                 /*
  257                  * Found it -- move to the front on the connection list.
  258                  */
  259                 if (cs == lastcs)
  260                         comp->last_cs = lcs;
  261                 else {
  262                         lcs->cs_next = cs->cs_next;
  263                         cs->cs_next = lastcs->cs_next;
  264                         lastcs->cs_next = cs;
  265                 }
  266         }
  267 
  268         /*
  269          * Make sure that only what we expect to change changed. The first
  270          * line of the `if' checks the IP protocol version, header length &
  271          * type of service.  The 2nd line checks the "Don't fragment" bit.
  272          * The 3rd line checks the time-to-live and protocol (the protocol
  273          * check is unnecessary but costless).  The 4th line checks the TCP
  274          * header length.  The 5th line checks IP options, if any.  The 6th
  275          * line checks TCP options, if any.  If any of these things are
  276          * different between the previous & current datagram, we send the
  277          * current datagram `uncompressed'.
  278          */
  279         oth = (struct tcphdr *)&((int32_t *)&cs->cs_ip)[hlen];
  280         deltaS = hlen;
  281         hlen += th->th_off;
  282         hlen <<= 2;
  283         if (hlen > m->m_len)
  284                 return (TYPE_IP);
  285 
  286         if (((u_int16_t *)ip)[0] != ((u_int16_t *)&cs->cs_ip)[0] ||
  287             ((u_int16_t *)ip)[3] != ((u_int16_t *)&cs->cs_ip)[3] ||
  288             ((u_int16_t *)ip)[4] != ((u_int16_t *)&cs->cs_ip)[4] ||
  289             th->th_off != oth->th_off ||
  290             (deltaS > 5 &&
  291              BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
  292             (th->th_off > 5 &&
  293              BCMP(th + 1, oth + 1, (th->th_off - 5) << 2)))
  294                 goto uncompressed;
  295 
  296         /*
  297          * Figure out which of the changing fields changed.  The
  298          * receiver expects changes in the order: urgent, window,
  299          * ack, seq (the order minimizes the number of temporaries
  300          * needed in this section of code).
  301          */
  302         if (th->th_flags & TH_URG) {
  303                 deltaS = ntohs(th->th_urp);
  304                 ENCODEZ(deltaS);
  305                 changes |= NEW_U;
  306         } else if (th->th_urp != oth->th_urp)
  307                 /* argh! URG not set but urp changed -- a sensible
  308                  * implementation should never do this but RFC793
  309                  * doesn't prohibit the change so we have to deal
  310                  * with it. */
  311                  goto uncompressed;
  312 
  313         deltaS = (u_int16_t)(ntohs(th->th_win) - ntohs(oth->th_win));
  314         if (deltaS) {
  315                 ENCODE(deltaS);
  316                 changes |= NEW_W;
  317         }
  318 
  319         deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack);
  320         if (deltaA) {
  321                 if (deltaA > 0xffff)
  322                         goto uncompressed;
  323                 ENCODE(deltaA);
  324                 changes |= NEW_A;
  325         }
  326 
  327         deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq);
  328         if (deltaS) {
  329                 if (deltaS > 0xffff)
  330                         goto uncompressed;
  331                 ENCODE(deltaS);
  332                 changes |= NEW_S;
  333         }
  334 
  335         switch (changes) {
  336 
  337         case 0:
  338                 /*
  339                  * Nothing changed. If this packet contains data and the
  340                  * last one didn't, this is probably a data packet following
  341                  * an ack (normal on an interactive connection) and we send
  342                  * it compressed.  Otherwise it's probably a retransmit,
  343                  * retransmitted ack or window probe.  Send it uncompressed
  344                  * in case the other side missed the compressed version.
  345                  */
  346                 if (ip->ip_len != cs->cs_ip.ip_len &&
  347                     ntohs(cs->cs_ip.ip_len) == hlen)
  348                         break;
  349 
  350                 /* (fall through) */
  351 
  352         case SPECIAL_I:
  353         case SPECIAL_D:
  354                 /*
  355                  * actual changes match one of our special case encodings --
  356                  * send packet uncompressed.
  357                  */
  358                 goto uncompressed;
  359 
  360         case NEW_S|NEW_A:
  361                 if (deltaS == deltaA &&
  362                     deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
  363                         /* special case for echoed terminal traffic */
  364                         changes = SPECIAL_I;
  365                         cp = new_seq;
  366                 }
  367                 break;
  368 
  369         case NEW_S:
  370                 if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
  371                         /* special case for data xfer */
  372                         changes = SPECIAL_D;
  373                         cp = new_seq;
  374                 }
  375                 break;
  376         }
  377 
  378         deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
  379         if (deltaS != 1) {
  380                 ENCODEZ(deltaS);
  381                 changes |= NEW_I;
  382         }
  383         if (th->th_flags & TH_PUSH)
  384                 changes |= TCP_PUSH_BIT;
  385         /*
  386          * Grab the cksum before we overwrite it below.  Then update our
  387          * state with this packet's header.
  388          */
  389         deltaA = ntohs(th->th_sum);
  390         BCOPY(ip, &cs->cs_ip, hlen);
  391 
  392         /*
  393          * We want to use the original packet as our compressed packet.
  394          * (cp - new_seq) is the number of bytes we need for compressed
  395          * sequence numbers.  In addition we need one byte for the change
  396          * mask, one for the connection id and two for the tcp checksum.
  397          * So, (cp - new_seq) + 4 bytes of header are needed.  hlen is how
  398          * many bytes of the original packet to toss so subtract the two to
  399          * get the new packet size.
  400          */
  401         deltaS = cp - new_seq;
  402         cp = (u_char *)ip;
  403         if (compress_cid == 0 || comp->last_xmit != cs->cs_id) {
  404                 comp->last_xmit = cs->cs_id;
  405                 hlen -= deltaS + 4;
  406                 cp += hlen;
  407                 *cp++ = changes | NEW_C;
  408                 *cp++ = cs->cs_id;
  409         } else {
  410                 hlen -= deltaS + 3;
  411                 cp += hlen;
  412                 *cp++ = changes;
  413         }
  414         m->m_len -= hlen;
  415         m->m_data += hlen;
  416         *cp++ = deltaA >> 8;
  417         *cp++ = deltaA;
  418         BCOPY(new_seq, cp, deltaS);
  419         INCR(sls_compressed)
  420         return (TYPE_COMPRESSED_TCP);
  421 
  422         /*
  423          * Update connection state cs & send uncompressed packet ('uncompressed'
  424          * means a regular ip/tcp packet but with the 'conversation id' we hope
  425          * to use on future compressed packets in the protocol field).
  426          */
  427 uncompressed:
  428         BCOPY(ip, &cs->cs_ip, hlen);
  429         ip->ip_p = cs->cs_id;
  430         comp->last_xmit = cs->cs_id;
  431         return (TYPE_UNCOMPRESSED_TCP);
  432 }
  433 
  434 
  435 int
  436 sl_uncompress_tcp(bufp, len, type, comp)
  437         u_char **bufp;
  438         int len;
  439         u_int type;
  440         struct slcompress *comp;
  441 {
  442         u_char *hdr, *cp;
  443         int vjlen;
  444         u_int hlen;
  445 
  446         cp = bufp? *bufp: NULL;
  447         vjlen = sl_uncompress_tcp_core(cp, len, len, type, comp, &hdr, &hlen);
  448         if (vjlen < 0)
  449                 return (0);     /* error */
  450         if (vjlen == 0)
  451                 return (len);   /* was uncompressed already */
  452 
  453         cp += vjlen;
  454         len -= vjlen;
  455 
  456         /*
  457          * At this point, cp points to the first byte of data in the
  458          * packet.  If we're not aligned on a 4-byte boundary, copy the
  459          * data down so the ip & tcp headers will be aligned.  Then back up
  460          * cp by the tcp/ip header length to make room for the reconstructed
  461          * header (we assume the packet we were handed has enough space to
  462          * prepend 128 bytes of header).
  463          */
  464         if ((long)cp & 3) {
  465                 if (len > 0)
  466                         memmove((caddr_t)((long)cp &~ 3), cp, len);
  467                 cp = (u_char *)((long)cp &~ 3);
  468         }
  469         cp -= hlen;
  470         len += hlen;
  471         BCOPY(hdr, cp, hlen);
  472 
  473         *bufp = cp;
  474         return (len);
  475 }
  476 
  477 /*
  478  * Uncompress a packet of total length total_len.  The first buflen
  479  * bytes are at buf; this must include the entire (compressed or
  480  * uncompressed) TCP/IP header.  This procedure returns the length
  481  * of the VJ header, with a pointer to the uncompressed IP header
  482  * in *hdrp and its length in *hlenp.
  483  */
  484 int
  485 sl_uncompress_tcp_core(buf, buflen, total_len, type, comp, hdrp, hlenp)
  486         u_char *buf;
  487         int buflen, total_len;
  488         u_int type;
  489         struct slcompress *comp;
  490         u_char **hdrp;
  491         u_int *hlenp;
  492 {
  493         u_char *cp;
  494         u_int hlen, changes;
  495         struct tcphdr *th;
  496         struct cstate *cs;
  497         struct ip *ip;
  498         u_int16_t *bp;
  499         u_int vjlen;
  500 
  501         switch (type) {
  502 
  503         case TYPE_UNCOMPRESSED_TCP:
  504                 ip = (struct ip *) buf;
  505                 if (ip->ip_p >= MAX_STATES)
  506                         goto bad;
  507                 cs = &comp->rstate[comp->last_recv = ip->ip_p];
  508                 comp->flags &=~ SLF_TOSS;
  509                 ip->ip_p = IPPROTO_TCP;
  510                 /*
  511                  * Calculate the size of the TCP/IP header and make sure that
  512                  * we don't overflow the space we have available for it.
  513                  */
  514                 hlen = ip->ip_hl << 2;
  515                 if (hlen + sizeof(struct tcphdr) > buflen)
  516                         goto bad;
  517                 hlen += ((struct tcphdr *)&((char *)ip)[hlen])->th_off << 2;
  518                 if (hlen > MAX_HDR || hlen > buflen)
  519                         goto bad;
  520                 BCOPY(ip, &cs->cs_ip, hlen);
  521                 cs->cs_hlen = hlen;
  522                 INCR(sls_uncompressedin)
  523                 *hdrp = (u_char *) &cs->cs_ip;
  524                 *hlenp = hlen;
  525                 return (0);
  526 
  527         default:
  528                 goto bad;
  529 
  530         case TYPE_COMPRESSED_TCP:
  531                 break;
  532         }
  533         /* We've got a compressed packet. */
  534         INCR(sls_compressedin)
  535         cp = buf;
  536         changes = *cp++;
  537         if (changes & NEW_C) {
  538                 /* Make sure the state index is in range, then grab the state.
  539                  * If we have a good state index, clear the 'discard' flag. */
  540                 if (*cp >= MAX_STATES)
  541                         goto bad;
  542 
  543                 comp->flags &=~ SLF_TOSS;
  544                 comp->last_recv = *cp++;
  545         } else {
  546                 /* this packet has an implicit state index.  If we've
  547                  * had a line error since the last time we got an
  548                  * explicit state index, we have to toss the packet. */
  549                 if (comp->flags & SLF_TOSS) {
  550                         INCR(sls_tossed)
  551                         return (-1);
  552                 }
  553         }
  554         cs = &comp->rstate[comp->last_recv];
  555         hlen = cs->cs_ip.ip_hl << 2;
  556         th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
  557         th->th_sum = htons((*cp << 8) | cp[1]);
  558         cp += 2;
  559         if (changes & TCP_PUSH_BIT)
  560                 th->th_flags |= TH_PUSH;
  561         else
  562                 th->th_flags &=~ TH_PUSH;
  563 
  564         switch (changes & SPECIALS_MASK) {
  565         case SPECIAL_I:
  566                 {
  567                 u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
  568                 th->th_ack = htonl(ntohl(th->th_ack) + i);
  569                 th->th_seq = htonl(ntohl(th->th_seq) + i);
  570                 }
  571                 break;
  572 
  573         case SPECIAL_D:
  574                 th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
  575                                    - cs->cs_hlen);
  576                 break;
  577 
  578         default:
  579                 if (changes & NEW_U) {
  580                         th->th_flags |= TH_URG;
  581                         DECODEU(th->th_urp)
  582                 } else
  583                         th->th_flags &=~ TH_URG;
  584                 if (changes & NEW_W)
  585                         DECODES(th->th_win)
  586                 if (changes & NEW_A)
  587                         DECODEL(th->th_ack)
  588                 if (changes & NEW_S)
  589                         DECODEL(th->th_seq)
  590                 break;
  591         }
  592         if (changes & NEW_I) {
  593                 DECODES(cs->cs_ip.ip_id)
  594         } else
  595                 cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
  596 
  597         /*
  598          * At this point, cp points to the first byte of data in the
  599          * packet.  Fill in the IP total length and update the IP
  600          * header checksum.
  601          */
  602         vjlen = cp - buf;
  603         buflen -= vjlen;
  604         if (buflen < 0)
  605                 /* we must have dropped some characters (crc should detect
  606                  * this but the old slip framing won't) */
  607                 goto bad;
  608 
  609         total_len += cs->cs_hlen - vjlen;
  610         cs->cs_ip.ip_len = htons(total_len);
  611 
  612         /* recompute the ip header checksum */
  613         bp = (u_int16_t *) &cs->cs_ip;
  614         cs->cs_ip.ip_sum = 0;
  615         for (changes = 0; hlen > 0; hlen -= 2)
  616                 changes += *bp++;
  617         changes = (changes & 0xffff) + (changes >> 16);
  618         changes = (changes & 0xffff) + (changes >> 16);
  619         cs->cs_ip.ip_sum = ~ changes;
  620 
  621         *hdrp = (u_char *) &cs->cs_ip;
  622         *hlenp = cs->cs_hlen;
  623         return vjlen;
  624 
  625 bad:
  626         comp->flags |= SLF_TOSS;
  627         INCR(sls_errorin)
  628         return (-1);
  629 }
  630 #endif

Cache object: 498086e9f06274263952f096826e059f


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.