634 lines
17 KiB
C
634 lines
17 KiB
C
/*
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* Routines to compress and uncompess tcp packets (for transmission
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* over low speed serial lines.
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*
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* Copyright (c) 1989 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* advertising materials, and other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*
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* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
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* - Initial distribution.
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*
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* Modified June 1993 by Paul Mackerras, paulus@cs.anu.edu.au,
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* so that the entire packet being decompressed doesn't have
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* to be in contiguous memory (just the compressed header).
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*
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* Modified March 1998 by Guy Lancaster, glanca@gesn.com,
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* for a 16 bit processor.
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*/
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#include <string.h>
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#include "ppp.h"
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#include "vj.h"
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#include "pppdebug.h"
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#if VJ_SUPPORT > 0
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#if LINK_STATS
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#define INCR(counter) ++comp->stats.counter
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#else
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#define INCR(counter)
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#endif
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#if defined(NO_CHAR_BITFIELDS)
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#define getip_hl(base) ((base).ip_hl_v&0xf)
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#define getth_off(base) (((base).th_x2_off&0xf0)>>4)
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#else
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#define getip_hl(base) ((base).ip_hl)
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#define getth_off(base) ((base).th_off)
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#endif
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void vj_compress_init(struct vjcompress *comp)
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{
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register u_int i;
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register struct cstate *tstate = comp->tstate;
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#if MAX_SLOTS == 0
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memset((char *)comp, 0, sizeof(*comp));
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#endif
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comp->maxSlotIndex = MAX_SLOTS - 1;
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comp->compressSlot = 0; /* Disable slot ID compression by default. */
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for (i = MAX_SLOTS - 1; i > 0; --i) {
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tstate[i].cs_id = i;
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tstate[i].cs_next = &tstate[i - 1];
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}
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tstate[0].cs_next = &tstate[MAX_SLOTS - 1];
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tstate[0].cs_id = 0;
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comp->last_cs = &tstate[0];
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comp->last_recv = 255;
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comp->last_xmit = 255;
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comp->flags = VJF_TOSS;
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}
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/* ENCODE encodes a number that is known to be non-zero. ENCODEZ
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* checks for zero (since zero has to be encoded in the long, 3 byte
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* form).
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*/
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#define ENCODE(n) { \
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if ((u_short)(n) >= 256) { \
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*cp++ = 0; \
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cp[1] = (n); \
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cp[0] = (n) >> 8; \
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cp += 2; \
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} else { \
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*cp++ = (n); \
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} \
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}
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#define ENCODEZ(n) { \
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if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
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*cp++ = 0; \
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cp[1] = (n); \
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cp[0] = (n) >> 8; \
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cp += 2; \
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} else { \
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*cp++ = (n); \
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} \
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}
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#define DECODEL(f) { \
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if (*cp == 0) {\
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u32_t tmp = ntohl(f) + ((cp[1] << 8) | cp[2]); \
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(f) = htonl(tmp); \
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cp += 3; \
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} else { \
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u32_t tmp = ntohl(f) + (u32_t)*cp++; \
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(f) = htonl(tmp); \
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} \
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}
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#define DECODES(f) { \
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if (*cp == 0) {\
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u_short tmp = ntohs(f) + (((u_short)cp[1] << 8) | cp[2]); \
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(f) = htons(tmp); \
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cp += 3; \
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} else { \
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u_short tmp = ntohs(f) + (u_short)*cp++; \
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(f) = htons(tmp); \
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} \
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}
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#define DECODEU(f) { \
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if (*cp == 0) {\
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(f) = htons(((u_short)cp[1] << 8) | cp[2]); \
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cp += 3; \
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} else { \
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(f) = htons((u_short)*cp++); \
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} \
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}
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/*
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* vj_compress_tcp - Attempt to do Van Jacobsen header compression on a
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* packet. This assumes that nb and comp are not null and that the first
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* buffer of the chain contains a valid IP header.
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* Return the VJ type code indicating whether or not the packet was
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* compressed.
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*/
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u_int vj_compress_tcp(
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struct vjcompress *comp,
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struct pbuf *pb
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)
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{
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register struct ip *ip = (struct ip *)pb->payload;
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register struct cstate *cs = comp->last_cs->cs_next;
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register u_short hlen = getip_hl(*ip);
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register struct tcphdr *oth;
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register struct tcphdr *th;
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register u_short deltaS, deltaA;
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register u_long deltaL;
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register u_int changes = 0;
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u_char new_seq[16];
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register u_char *cp = new_seq;
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/*
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* Check that the packet is IP proto TCP.
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*/
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if (ip->ip_p != IPPROTO_TCP)
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return (TYPE_IP);
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/*
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* Bail if this is an IP fragment or if the TCP packet isn't
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* `compressible' (i.e., ACK isn't set or some other control bit is
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* set).
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*/
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if ((ip->ip_off & htons(0x3fff)) || pb->tot_len < 40)
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return (TYPE_IP);
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th = (struct tcphdr *)&((long *)ip)[hlen];
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if ((th->th_flags & (TCP_SYN|TCP_FIN|TCP_RST|TCP_ACK)) != TCP_ACK)
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return (TYPE_IP);
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/*
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* Packet is compressible -- we're going to send either a
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* COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need
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* to locate (or create) the connection state. Special case the
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* most recently used connection since it's most likely to be used
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* again & we don't have to do any reordering if it's used.
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*/
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INCR(vjs_packets);
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if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr
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|| ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr
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|| *(long *)th != ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) {
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/*
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* Wasn't the first -- search for it.
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*
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* States are kept in a circularly linked list with
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* last_cs pointing to the end of the list. The
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* list is kept in lru order by moving a state to the
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* head of the list whenever it is referenced. Since
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* the list is short and, empirically, the connection
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* we want is almost always near the front, we locate
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* states via linear search. If we don't find a state
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* for the datagram, the oldest state is (re-)used.
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*/
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register struct cstate *lcs;
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register struct cstate *lastcs = comp->last_cs;
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do {
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lcs = cs; cs = cs->cs_next;
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INCR(vjs_searches);
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if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
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&& ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
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&& *(long *)th == ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)])
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goto found;
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} while (cs != lastcs);
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/*
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* Didn't find it -- re-use oldest cstate. Send an
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* uncompressed packet that tells the other side what
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* connection number we're using for this conversation.
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* Note that since the state list is circular, the oldest
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* state points to the newest and we only need to set
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* last_cs to update the lru linkage.
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*/
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INCR(vjs_misses);
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comp->last_cs = lcs;
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hlen += getth_off(*th);
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hlen <<= 2;
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/* Check that the IP/TCP headers are contained in the first buffer. */
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if (hlen > pb->len)
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return (TYPE_IP);
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goto uncompressed;
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found:
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/*
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* Found it -- move to the front on the connection list.
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*/
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if (cs == lastcs)
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comp->last_cs = lcs;
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else {
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lcs->cs_next = cs->cs_next;
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cs->cs_next = lastcs->cs_next;
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lastcs->cs_next = cs;
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}
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}
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oth = (struct tcphdr *)&((long *)&cs->cs_ip)[hlen];
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deltaS = hlen;
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hlen += getth_off(*th);
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hlen <<= 2;
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/* Check that the IP/TCP headers are contained in the first buffer. */
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if (hlen > pb->len) {
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PPPDEBUG((LOG_INFO, "vj_compress_tcp: header len %d spans buffers\n",
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hlen));
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return (TYPE_IP);
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}
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/*
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* Make sure that only what we expect to change changed. The first
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* line of the `if' checks the IP protocol version, header length &
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* type of service. The 2nd line checks the "Don't fragment" bit.
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* The 3rd line checks the time-to-live and protocol (the protocol
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* check is unnecessary but costless). The 4th line checks the TCP
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* header length. The 5th line checks IP options, if any. The 6th
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* line checks TCP options, if any. If any of these things are
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* different between the previous & current datagram, we send the
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* current datagram `uncompressed'.
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*/
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if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0]
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|| ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3]
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|| ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4]
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|| getth_off(*th) != getth_off(*oth)
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|| (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2))
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|| (getth_off(*th) > 5 && BCMP(th + 1, oth + 1, (getth_off(*th) - 5) << 2)))
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goto uncompressed;
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/*
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* Figure out which of the changing fields changed. The
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* receiver expects changes in the order: urgent, window,
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* ack, seq (the order minimizes the number of temporaries
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* needed in this section of code).
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*/
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if (th->th_flags & TCP_URG) {
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deltaS = ntohs(th->th_urp);
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ENCODEZ(deltaS);
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changes |= NEW_U;
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} else if (th->th_urp != oth->th_urp)
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/* argh! URG not set but urp changed -- a sensible
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* implementation should never do this but RFC793
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* doesn't prohibit the change so we have to deal
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* with it. */
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goto uncompressed;
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if ((deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) != 0) {
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ENCODE(deltaS);
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changes |= NEW_W;
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}
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if ((deltaL = ntohl(th->th_ack) - ntohl(oth->th_ack)) != 0) {
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if (deltaL > 0xffff)
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goto uncompressed;
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deltaA = (u_short)deltaL;
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ENCODE(deltaA);
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changes |= NEW_A;
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}
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if ((deltaL = ntohl(th->th_seq) - ntohl(oth->th_seq)) != 0) {
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if (deltaL > 0xffff)
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goto uncompressed;
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deltaS = (u_short)deltaL;
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ENCODE(deltaS);
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changes |= NEW_S;
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}
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switch(changes) {
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case 0:
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/*
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* Nothing changed. If this packet contains data and the
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* last one didn't, this is probably a data packet following
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* an ack (normal on an interactive connection) and we send
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* it compressed. Otherwise it's probably a retransmit,
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* retransmitted ack or window probe. Send it uncompressed
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* in case the other side missed the compressed version.
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*/
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if (ip->ip_len != cs->cs_ip.ip_len &&
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ntohs(cs->cs_ip.ip_len) == hlen)
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break;
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/* (fall through) */
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case SPECIAL_I:
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case SPECIAL_D:
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/*
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* actual changes match one of our special case encodings --
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* send packet uncompressed.
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*/
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goto uncompressed;
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case NEW_S|NEW_A:
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if (deltaS == deltaA && deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
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/* special case for echoed terminal traffic */
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changes = SPECIAL_I;
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cp = new_seq;
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}
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break;
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case NEW_S:
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if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
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/* special case for data xfer */
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changes = SPECIAL_D;
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cp = new_seq;
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}
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break;
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}
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deltaS = (u_short)(ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id));
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if (deltaS != 1) {
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ENCODEZ(deltaS);
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changes |= NEW_I;
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}
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if (th->th_flags & TCP_PSH)
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changes |= TCP_PUSH_BIT;
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/*
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* Grab the cksum before we overwrite it below. Then update our
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* state with this packet's header.
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*/
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deltaA = ntohs(th->th_sum);
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BCOPY(ip, &cs->cs_ip, hlen);
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/*
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* We want to use the original packet as our compressed packet.
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* (cp - new_seq) is the number of bytes we need for compressed
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* sequence numbers. In addition we need one byte for the change
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* mask, one for the connection id and two for the tcp checksum.
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* So, (cp - new_seq) + 4 bytes of header are needed. hlen is how
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* many bytes of the original packet to toss so subtract the two to
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* get the new packet size.
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*/
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deltaS = (u_short)(cp - new_seq);
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if (!comp->compressSlot || comp->last_xmit != cs->cs_id) {
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comp->last_xmit = cs->cs_id;
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hlen -= deltaS + 4;
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pbuf_header(pb, -hlen);
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cp = (u_char *)pb->payload;
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*cp++ = changes | NEW_C;
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*cp++ = cs->cs_id;
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} else {
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hlen -= deltaS + 3;
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pbuf_header(pb, -hlen);
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cp = (u_char *)pb->payload;
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*cp++ = changes;
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}
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*cp++ = deltaA >> 8;
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*cp++ = deltaA;
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BCOPY(new_seq, cp, deltaS);
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INCR(vjs_compressed);
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return (TYPE_COMPRESSED_TCP);
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/*
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* Update connection state cs & send uncompressed packet (that is,
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* a regular ip/tcp packet but with the 'conversation id' we hope
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* to use on future compressed packets in the protocol field).
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*/
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uncompressed:
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BCOPY(ip, &cs->cs_ip, hlen);
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ip->ip_p = cs->cs_id;
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comp->last_xmit = cs->cs_id;
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return (TYPE_UNCOMPRESSED_TCP);
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}
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/*
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* Called when we may have missed a packet.
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*/
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void vj_uncompress_err(struct vjcompress *comp)
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{
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comp->flags |= VJF_TOSS;
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INCR(vjs_errorin);
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}
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/*
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* "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP.
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* Return 0 on success, -1 on failure.
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*/
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int vj_uncompress_uncomp(
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struct pbuf *nb,
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struct vjcompress *comp
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)
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{
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register u_int hlen;
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register struct cstate *cs;
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register struct ip *ip;
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ip = (struct ip *)nb->payload;
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hlen = getip_hl(*ip) << 2;
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if (ip->ip_p >= MAX_SLOTS
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|| hlen + sizeof(struct tcphdr) > nb->len
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|| (hlen += getth_off(*((struct tcphdr *)&((char *)ip)[hlen])) << 2)
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> nb->len
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|| hlen > MAX_HDR) {
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PPPDEBUG((LOG_INFO, "vj_uncompress_uncomp: bad cid=%d, hlen=%d buflen=%d\n",
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ip->ip_p, hlen, nb->len));
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comp->flags |= VJF_TOSS;
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INCR(vjs_errorin);
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return -1;
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}
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cs = &comp->rstate[comp->last_recv = ip->ip_p];
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comp->flags &=~ VJF_TOSS;
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ip->ip_p = IPPROTO_TCP;
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BCOPY(ip, &cs->cs_ip, hlen);
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cs->cs_hlen = hlen;
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INCR(vjs_uncompressedin);
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return 0;
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}
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/*
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* Uncompress a packet of type TYPE_COMPRESSED_TCP.
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* The packet is composed of a buffer chain and the first buffer
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* must contain an accurate chain length.
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* The first buffer must include the entire compressed TCP/IP header.
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* This procedure replaces the compressed header with the uncompressed
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* header and returns the length of the VJ header.
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*/
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int vj_uncompress_tcp(
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struct pbuf **nb,
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struct vjcompress *comp
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)
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{
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u_char *cp;
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struct tcphdr *th;
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struct cstate *cs;
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u_short *bp;
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struct pbuf *n0 = *nb;
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u32_t tmp;
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u_int vjlen, hlen, changes;
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INCR(vjs_compressedin);
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cp = (u_char *)n0->payload;
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changes = *cp++;
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if (changes & NEW_C) {
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/*
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* Make sure the state index is in range, then grab the state.
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* If we have a good state index, clear the 'discard' flag.
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*/
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if (*cp >= MAX_SLOTS) {
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PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: bad cid=%d\n", *cp));
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goto bad;
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}
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comp->flags &=~ VJF_TOSS;
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comp->last_recv = *cp++;
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} else {
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/*
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* this packet has an implicit state index. If we've
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* had a line error since the last time we got an
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* explicit state index, we have to toss the packet.
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*/
|
|
if (comp->flags & VJF_TOSS) {
|
|
PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: tossing\n"));
|
|
INCR(vjs_tossed);
|
|
return (-1);
|
|
}
|
|
}
|
|
cs = &comp->rstate[comp->last_recv];
|
|
hlen = getip_hl(cs->cs_ip) << 2;
|
|
th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
|
|
th->th_sum = htons((*cp << 8) | cp[1]);
|
|
cp += 2;
|
|
if (changes & TCP_PUSH_BIT)
|
|
th->th_flags |= TCP_PSH;
|
|
else
|
|
th->th_flags &=~ TCP_PSH;
|
|
|
|
switch (changes & SPECIALS_MASK) {
|
|
case SPECIAL_I:
|
|
{
|
|
register u32_t i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
|
|
/* some compilers can't nest inline assembler.. */
|
|
tmp = ntohl(th->th_ack) + i;
|
|
th->th_ack = htonl(tmp);
|
|
tmp = ntohl(th->th_seq) + i;
|
|
th->th_seq = htonl(tmp);
|
|
}
|
|
break;
|
|
|
|
case SPECIAL_D:
|
|
/* some compilers can't nest inline assembler.. */
|
|
tmp = ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
|
|
th->th_seq = htonl(tmp);
|
|
break;
|
|
|
|
default:
|
|
if (changes & NEW_U) {
|
|
th->th_flags |= TCP_URG;
|
|
DECODEU(th->th_urp);
|
|
} else
|
|
th->th_flags &=~ TCP_URG;
|
|
if (changes & NEW_W)
|
|
DECODES(th->th_win);
|
|
if (changes & NEW_A)
|
|
DECODEL(th->th_ack);
|
|
if (changes & NEW_S)
|
|
DECODEL(th->th_seq);
|
|
break;
|
|
}
|
|
if (changes & NEW_I) {
|
|
DECODES(cs->cs_ip.ip_id);
|
|
} else {
|
|
cs->cs_ip.ip_id = ntohs(cs->cs_ip.ip_id) + 1;
|
|
cs->cs_ip.ip_id = htons(cs->cs_ip.ip_id);
|
|
}
|
|
|
|
/*
|
|
* At this point, cp points to the first byte of data in the
|
|
* packet. Fill in the IP total length and update the IP
|
|
* header checksum.
|
|
*/
|
|
vjlen = (u_short)(cp - (u_char*)n0->payload);
|
|
if (n0->len < vjlen) {
|
|
/*
|
|
* We must have dropped some characters (crc should detect
|
|
* this but the old slip framing won't)
|
|
*/
|
|
PPPDEBUG((LOG_INFO, "vj_uncompress_tcp: head buffer %d too short %d\n",
|
|
n0->len, vjlen));
|
|
goto bad;
|
|
}
|
|
|
|
#if BYTE_ORDER == LITTLE_ENDIAN
|
|
tmp = n0->tot_len - vjlen + cs->cs_hlen;
|
|
cs->cs_ip.ip_len = htons(tmp);
|
|
#else
|
|
cs->cs_ip.ip_len = htons(n0->tot_len - vjlen + cs->cs_hlen);
|
|
#endif
|
|
|
|
/* recompute the ip header checksum */
|
|
bp = (u_short *) &cs->cs_ip;
|
|
cs->cs_ip.ip_sum = 0;
|
|
for (tmp = 0; hlen > 0; hlen -= 2)
|
|
tmp += *bp++;
|
|
tmp = (tmp & 0xffff) + (tmp >> 16);
|
|
tmp = (tmp & 0xffff) + (tmp >> 16);
|
|
cs->cs_ip.ip_sum = (u_short)(~tmp);
|
|
|
|
/* Remove the compressed header and prepend the uncompressed header. */
|
|
pbuf_header(n0, -vjlen);
|
|
|
|
if(MEM_ALIGN(n0->payload) != n0->payload) {
|
|
struct pbuf *np, *q;
|
|
u8_t *bufptr;
|
|
|
|
np = pbuf_alloc(PBUF_RAW, n0->len + cs->cs_hlen, PBUF_POOL);
|
|
if(!np) {
|
|
PPPDEBUG((LOG_WARNING, "vj_uncompress_tcp: realign failed\n"));
|
|
*nb = NULL;
|
|
goto bad;
|
|
}
|
|
|
|
pbuf_header(np, -cs->cs_hlen);
|
|
|
|
bufptr = n0->payload;
|
|
for(q = np; q != NULL; q = q->next) {
|
|
memcpy(q->payload, bufptr, q->len);
|
|
bufptr += q->len;
|
|
}
|
|
|
|
if(n0->next) {
|
|
pbuf_chain(np, n0->next);
|
|
pbuf_dechain(n0);
|
|
}
|
|
pbuf_free(n0);
|
|
n0 = np;
|
|
}
|
|
|
|
if(pbuf_header(n0, cs->cs_hlen)) {
|
|
struct pbuf *np;
|
|
|
|
LWIP_ASSERT("vj_uncompress_tcp: cs->cs_hlen <= PBUF_POOL_BUFSIZE", cs->cs_hlen <= PBUF_POOL_BUFSIZE);
|
|
np = pbuf_alloc(PBUF_RAW, cs->cs_hlen, PBUF_POOL);
|
|
if(!np) {
|
|
PPPDEBUG((LOG_WARNING, "vj_uncompress_tcp: prepend failed\n"));
|
|
*nb = NULL;
|
|
goto bad;
|
|
}
|
|
pbuf_cat(np, n0);
|
|
n0 = np;
|
|
}
|
|
LWIP_ASSERT("n0->len >= cs->cs_hlen", n0->len >= cs->cs_hlen);
|
|
memcpy(n0->payload, &cs->cs_ip, cs->cs_hlen);
|
|
|
|
*nb = n0;
|
|
|
|
return vjlen;
|
|
|
|
bad:
|
|
comp->flags |= VJF_TOSS;
|
|
INCR(vjs_errorin);
|
|
return (-1);
|
|
}
|
|
|
|
#endif
|
|
|
|
|