BadVPN – Rev 1
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/*
* Routines to compress and uncompess tcp packets (for transmission
* over low speed serial lines.
*
* Copyright (c) 1989 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley. The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
* Initial distribution.
*
* Modified June 1993 by Paul Mackerras, paulus@cs.anu.edu.au,
* so that the entire packet being decompressed doesn't have
* to be in contiguous memory (just the compressed header).
*
* Modified March 1998 by Guy Lancaster, glanca@gesn.com,
* for a 16 bit processor.
*/
#include "netif/ppp/ppp_opts.h"
#if PPP_SUPPORT && VJ_SUPPORT /* don't build if not configured for use in lwipopts.h */
#include "netif/ppp/ppp_impl.h"
#include "netif/ppp/pppdebug.h"
#include "netif/ppp/vj.h"
#include <string.h>
#if LINK_STATS
#define INCR(counter) ++comp->stats.counter
#else
#define INCR(counter)
#endif
void
vj_compress_init(struct vjcompress *comp)
{
u8_t i;
struct cstate *tstate = comp->tstate;
#if MAX_SLOTS == 0
memset((char *)comp, 0, sizeof(*comp));
#endif
comp->maxSlotIndex = MAX_SLOTS - 1;
comp->compressSlot = 0; /* Disable slot ID compression by default. */
for (i = MAX_SLOTS - 1; i > 0; --i) {
tstate[i].cs_id = i;
tstate[i].cs_next = &tstate[i - 1];
}
tstate[0].cs_next = &tstate[MAX_SLOTS - 1];
tstate[0].cs_id = 0;
comp->last_cs = &tstate[0];
comp->last_recv = 255;
comp->last_xmit = 255;
comp->flags = VJF_TOSS;
}
/* ENCODE encodes a number that is known to be non-zero. ENCODEZ
* checks for zero (since zero has to be encoded in the long, 3 byte
* form).
*/
#define ENCODE(n) { \
if ((u16_t)(n) >= 256) { \
*cp++ = 0; \
cp[1] = (u8_t)(n); \
cp[0] = (u8_t)((n) >> 8); \
cp += 2; \
} else { \
*cp++ = (u8_t)(n); \
} \
}
#define ENCODEZ(n) { \
if ((u16_t)(n) >= 256 || (u16_t)(n) == 0) { \
*cp++ = 0; \
cp[1] = (u8_t)(n); \
cp[0] = (u8_t)((n) >> 8); \
cp += 2; \
} else { \
*cp++ = (u8_t)(n); \
} \
}
#define DECODEL(f) { \
if (*cp == 0) {\
u32_t tmp_ = lwip_ntohl(f) + ((cp[1] << 8) | cp[2]); \
(f) = lwip_htonl(tmp_); \
cp += 3; \
} else { \
u32_t tmp_ = lwip_ntohl(f) + (u32_t)*cp++; \
(f) = lwip_htonl(tmp_); \
} \
}
#define DECODES(f) { \
if (*cp == 0) {\
u16_t tmp_ = lwip_ntohs(f) + (((u16_t)cp[1] << 8) | cp[2]); \
(f) = lwip_htons(tmp_); \
cp += 3; \
} else { \
u16_t tmp_ = lwip_ntohs(f) + (u16_t)*cp++; \
(f) = lwip_htons(tmp_); \
} \
}
#define DECODEU(f) { \
if (*cp == 0) {\
(f) = lwip_htons(((u16_t)cp[1] << 8) | cp[2]); \
cp += 3; \
} else { \
(f) = lwip_htons((u16_t)*cp++); \
} \
}
/* Helper structures for unaligned *u32_t and *u16_t accesses */
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct vj_u32_t {
PACK_STRUCT_FIELD(u32_t v);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
struct vj_u16_t {
PACK_STRUCT_FIELD(u16_t v);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
/*
* vj_compress_tcp - Attempt to do Van Jacobson header compression on a
* packet. This assumes that nb and comp are not null and that the first
* buffer of the chain contains a valid IP header.
* Return the VJ type code indicating whether or not the packet was
* compressed.
*/
u8_t
vj_compress_tcp(struct vjcompress *comp, struct pbuf **pb)
{
struct pbuf *np = *pb;
struct ip_hdr *ip = (struct ip_hdr *)np->payload;
struct cstate *cs = comp->last_cs->cs_next;
u16_t ilen = IPH_HL(ip);
u16_t hlen;
struct tcp_hdr *oth;
struct tcp_hdr *th;
u16_t deltaS, deltaA = 0;
u32_t deltaL;
u32_t changes = 0;
u8_t new_seq[16];
u8_t *cp = new_seq;
/*
* Check that the packet is IP proto TCP.
*/
if (IPH_PROTO(ip) != IP_PROTO_TCP) {
return (TYPE_IP);
}
/*
* Bail if this is an IP fragment or if the TCP packet isn't
* `compressible' (i.e., ACK isn't set or some other control bit is
* set).
*/
if ((IPH_OFFSET(ip) & PP_HTONS(0x3fff)) || np->tot_len < 40) {
return (TYPE_IP);
}
th = (struct tcp_hdr *)&((struct vj_u32_t*)ip)[ilen];
if ((TCPH_FLAGS(th) & (TCP_SYN|TCP_FIN|TCP_RST|TCP_ACK)) != TCP_ACK) {
return (TYPE_IP);
}
/* Check that the TCP/IP headers are contained in the first buffer. */
hlen = ilen + TCPH_HDRLEN(th);
hlen <<= 2;
if (np->len < hlen) {
PPPDEBUG(LOG_INFO, ("vj_compress_tcp: header len %d spans buffers\n", hlen));
return (TYPE_IP);
}
/* TCP stack requires that we don't change the packet payload, therefore we copy
* the whole packet before compression. */
np = pbuf_clone(PBUF_RAW, PBUF_POOL, *pb);
if (!np) {
return (TYPE_IP);
}
*pb = np;
ip = (struct ip_hdr *)np->payload;
/*
* Packet is compressible -- we're going to send either a
* COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need
* to locate (or create) the connection state. Special case the
* most recently used connection since it's most likely to be used
* again & we don't have to do any reordering if it's used.
*/
INCR(vjs_packets);
if (!ip4_addr_cmp(&ip->src, &cs->cs_ip.src)
|| !ip4_addr_cmp(&ip->dest, &cs->cs_ip.dest)
|| (*(struct vj_u32_t*)th).v != (((struct vj_u32_t*)&cs->cs_ip)[IPH_HL(&cs->cs_ip)]).v) {
/*
* Wasn't the first -- search for it.
*
* States are kept in a circularly linked list with
* last_cs pointing to the end of the list. The
* list is kept in lru order by moving a state to the
* head of the list whenever it is referenced. Since
* the list is short and, empirically, the connection
* we want is almost always near the front, we locate
* states via linear search. If we don't find a state
* for the datagram, the oldest state is (re-)used.
*/
struct cstate *lcs;
struct cstate *lastcs = comp->last_cs;
do {
lcs = cs; cs = cs->cs_next;
INCR(vjs_searches);
if (ip4_addr_cmp(&ip->src, &cs->cs_ip.src)
&& ip4_addr_cmp(&ip->dest, &cs->cs_ip.dest)
&& (*(struct vj_u32_t*)th).v == (((struct vj_u32_t*)&cs->cs_ip)[IPH_HL(&cs->cs_ip)]).v) {
goto found;
}
} while (cs != lastcs);
/*
* Didn't find it -- re-use oldest cstate. Send an
* uncompressed packet that tells the other side what
* connection number we're using for this conversation.
* Note that since the state list is circular, the oldest
* state points to the newest and we only need to set
* last_cs to update the lru linkage.
*/
INCR(vjs_misses);
comp->last_cs = lcs;
goto uncompressed;
found:
/*
* Found it -- move to the front on the connection list.
*/
if (cs == lastcs) {
comp->last_cs = lcs;
} else {
lcs->cs_next = cs->cs_next;
cs->cs_next = lastcs->cs_next;
lastcs->cs_next = cs;
}
}
oth = (struct tcp_hdr *)&((struct vj_u32_t*)&cs->cs_ip)[ilen];
deltaS = ilen;
/*
* Make sure that only what we expect to change changed. The first
* line of the `if' checks the IP protocol version, header length &
* type of service. The 2nd line checks the "Don't fragment" bit.
* The 3rd line checks the time-to-live and protocol (the protocol
* check is unnecessary but costless). The 4th line checks the TCP
* header length. The 5th line checks IP options, if any. The 6th
* line checks TCP options, if any. If any of these things are
* different between the previous & current datagram, we send the
* current datagram `uncompressed'.
*/
if ((((struct vj_u16_t*)ip)[0]).v != (((struct vj_u16_t*)&cs->cs_ip)[0]).v
|| (((struct vj_u16_t*)ip)[3]).v != (((struct vj_u16_t*)&cs->cs_ip)[3]).v
|| (((struct vj_u16_t*)ip)[4]).v != (((struct vj_u16_t*)&cs->cs_ip)[4]).v
|| TCPH_HDRLEN(th) != TCPH_HDRLEN(oth)
|| (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2))
|| (TCPH_HDRLEN(th) > 5 && BCMP(th + 1, oth + 1, (TCPH_HDRLEN(th) - 5) << 2))) {
goto uncompressed;
}
/*
* Figure out which of the changing fields changed. The
* receiver expects changes in the order: urgent, window,
* ack, seq (the order minimizes the number of temporaries
* needed in this section of code).
*/
if (TCPH_FLAGS(th) & TCP_URG) {
deltaS = lwip_ntohs(th->urgp);
ENCODEZ(deltaS);
changes |= NEW_U;
} else if (th->urgp != oth->urgp) {
/* argh! URG not set but urp changed -- a sensible
* implementation should never do this but RFC793
* doesn't prohibit the change so we have to deal
* with it. */
goto uncompressed;
}
if ((deltaS = (u16_t)(lwip_ntohs(th->wnd) - lwip_ntohs(oth->wnd))) != 0) {
ENCODE(deltaS);
changes |= NEW_W;
}
if ((deltaL = lwip_ntohl(th->ackno) - lwip_ntohl(oth->ackno)) != 0) {
if (deltaL > 0xffff) {
goto uncompressed;
}
deltaA = (u16_t)deltaL;
ENCODE(deltaA);
changes |= NEW_A;
}
if ((deltaL = lwip_ntohl(th->seqno) - lwip_ntohl(oth->seqno)) != 0) {
if (deltaL > 0xffff) {
goto uncompressed;
}
deltaS = (u16_t)deltaL;
ENCODE(deltaS);
changes |= NEW_S;
}
switch(changes) {
case 0:
/*
* Nothing changed. If this packet contains data and the
* last one didn't, this is probably a data packet following
* an ack (normal on an interactive connection) and we send
* it compressed. Otherwise it's probably a retransmit,
* retransmitted ack or window probe. Send it uncompressed
* in case the other side missed the compressed version.
*/
if (IPH_LEN(ip) != IPH_LEN(&cs->cs_ip) &&
lwip_ntohs(IPH_LEN(&cs->cs_ip)) == hlen) {
break;
}
/* no break */
/* fall through */
case SPECIAL_I:
case SPECIAL_D:
/*
* actual changes match one of our special case encodings --
* send packet uncompressed.
*/
goto uncompressed;
case NEW_S|NEW_A:
if (deltaS == deltaA && deltaS == lwip_ntohs(IPH_LEN(&cs->cs_ip)) - hlen) {
/* special case for echoed terminal traffic */
changes = SPECIAL_I;
cp = new_seq;
}
break;
case NEW_S:
if (deltaS == lwip_ntohs(IPH_LEN(&cs->cs_ip)) - hlen) {
/* special case for data xfer */
changes = SPECIAL_D;
cp = new_seq;
}
break;
default:
break;
}
deltaS = (u16_t)(lwip_ntohs(IPH_ID(ip)) - lwip_ntohs(IPH_ID(&cs->cs_ip)));
if (deltaS != 1) {
ENCODEZ(deltaS);
changes |= NEW_I;
}
if (TCPH_FLAGS(th) & TCP_PSH) {
changes |= TCP_PUSH_BIT;
}
/*
* Grab the cksum before we overwrite it below. Then update our
* state with this packet's header.
*/
deltaA = lwip_ntohs(th->chksum);
MEMCPY(&cs->cs_ip, ip, hlen);
/*
* We want to use the original packet as our compressed packet.
* (cp - new_seq) is the number of bytes we need for compressed
* sequence numbers. In addition we need one byte for the change
* mask, one for the connection id and two for the tcp checksum.
* So, (cp - new_seq) + 4 bytes of header are needed. hlen is how
* many bytes of the original packet to toss so subtract the two to
* get the new packet size.
*/
deltaS = (u16_t)(cp - new_seq);
if (!comp->compressSlot || comp->last_xmit != cs->cs_id) {
comp->last_xmit = cs->cs_id;
hlen -= deltaS + 4;
if (pbuf_remove_header(np, hlen)){
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_remove_header failed\n", 0);
}
cp = (u8_t*)np->payload;
*cp++ = (u8_t)(changes | NEW_C);
*cp++ = cs->cs_id;
} else {
hlen -= deltaS + 3;
if (pbuf_remove_header(np, hlen)) {
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_remove_header failed\n", 0);
}
cp = (u8_t*)np->payload;
*cp++ = (u8_t)changes;
}
*cp++ = (u8_t)(deltaA >> 8);
*cp++ = (u8_t)deltaA;
MEMCPY(cp, new_seq, deltaS);
INCR(vjs_compressed);
return (TYPE_COMPRESSED_TCP);
/*
* Update connection state cs & send uncompressed packet (that is,
* a regular ip/tcp packet but with the 'conversation id' we hope
* to use on future compressed packets in the protocol field).
*/
uncompressed:
MEMCPY(&cs->cs_ip, ip, hlen);
IPH_PROTO_SET(ip, cs->cs_id);
comp->last_xmit = cs->cs_id;
return (TYPE_UNCOMPRESSED_TCP);
}
/*
* Called when we may have missed a packet.
*/
void
vj_uncompress_err(struct vjcompress *comp)
{
comp->flags |= VJF_TOSS;
INCR(vjs_errorin);
}
/*
* "Uncompress" a packet of type TYPE_UNCOMPRESSED_TCP.
* Return 0 on success, -1 on failure.
*/
int
vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp)
{
u32_t hlen;
struct cstate *cs;
struct ip_hdr *ip;
ip = (struct ip_hdr *)nb->payload;
hlen = IPH_HL(ip) << 2;
if (IPH_PROTO(ip) >= MAX_SLOTS
|| hlen + sizeof(struct tcp_hdr) > nb->len
|| (hlen += TCPH_HDRLEN_BYTES((struct tcp_hdr *)&((char *)ip)[hlen]))
> nb->len
|| hlen > MAX_HDR) {
PPPDEBUG(LOG_INFO, ("vj_uncompress_uncomp: bad cid=%d, hlen=%d buflen=%d\n",
IPH_PROTO(ip), hlen, nb->len));
vj_uncompress_err(comp);
return -1;
}
cs = &comp->rstate[comp->last_recv = IPH_PROTO(ip)];
comp->flags &=~ VJF_TOSS;
IPH_PROTO_SET(ip, IP_PROTO_TCP);
/* copy from/to bigger buffers checked above instead of cs->cs_ip and ip
just to help static code analysis to see this is correct ;-) */
MEMCPY(&cs->cs_hdr, nb->payload, hlen);
cs->cs_hlen = (u16_t)hlen;
INCR(vjs_uncompressedin);
return 0;
}
/*
* Uncompress a packet of type TYPE_COMPRESSED_TCP.
* The packet is composed of a buffer chain and the first buffer
* must contain an accurate chain length.
* The first buffer must include the entire compressed TCP/IP header.
* This procedure replaces the compressed header with the uncompressed
* header and returns the length of the VJ header.
*/
int
vj_uncompress_tcp(struct pbuf **nb, struct vjcompress *comp)
{
u8_t *cp;
struct tcp_hdr *th;
struct cstate *cs;
struct vj_u16_t *bp;
struct pbuf *n0 = *nb;
u32_t tmp;
u32_t vjlen, hlen, changes;
INCR(vjs_compressedin);
cp = (u8_t*)n0->payload;
changes = *cp++;
if (changes & NEW_C) {
/*
* Make sure the state index is in range, then grab the state.
* If we have a good state index, clear the 'discard' flag.
*/
if (*cp >= MAX_SLOTS) {
PPPDEBUG(LOG_INFO, ("vj_uncompress_tcp: bad cid=%d\n", *cp));
goto bad;
}
comp->flags &=~ VJF_TOSS;
comp->last_recv = *cp++;
} else {
/*
* this packet has an implicit state index. If we've
* had a line error since the last time we got an
* explicit state index, we have to toss the packet.
*/
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 = IPH_HL(&cs->cs_ip) << 2;
th = (struct tcp_hdr *)&((u8_t*)&cs->cs_ip)[hlen];
th->chksum = lwip_htons((*cp << 8) | cp[1]);
cp += 2;
if (changes & TCP_PUSH_BIT) {
TCPH_SET_FLAG(th, TCP_PSH);
} else {
TCPH_UNSET_FLAG(th, TCP_PSH);
}
switch (changes & SPECIALS_MASK) {
case SPECIAL_I:
{
u32_t i = lwip_ntohs(IPH_LEN(&cs->cs_ip)) - cs->cs_hlen;
/* some compilers can't nest inline assembler.. */
tmp = lwip_ntohl(th->ackno) + i;
th->ackno = lwip_htonl(tmp);
tmp = lwip_ntohl(th->seqno) + i;
th->seqno = lwip_htonl(tmp);
}
break;
case SPECIAL_D:
/* some compilers can't nest inline assembler.. */
tmp = lwip_ntohl(th->seqno) + lwip_ntohs(IPH_LEN(&cs->cs_ip)) - cs->cs_hlen;
th->seqno = lwip_htonl(tmp);
break;
default:
if (changes & NEW_U) {
TCPH_SET_FLAG(th, TCP_URG);
DECODEU(th->urgp);
} else {
TCPH_UNSET_FLAG(th, TCP_URG);
}
if (changes & NEW_W) {
DECODES(th->wnd);
}
if (changes & NEW_A) {
DECODEL(th->ackno);
}
if (changes & NEW_S) {
DECODEL(th->seqno);
}
break;
}
if (changes & NEW_I) {
DECODES(cs->cs_ip._id);
} else {
IPH_ID_SET(&cs->cs_ip, lwip_ntohs(IPH_ID(&cs->cs_ip)) + 1);
IPH_ID_SET(&cs->cs_ip, lwip_htons(IPH_ID(&cs->cs_ip)));
}
/*
* 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 = (u16_t)(cp - (u8_t*)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;
IPH_LEN_SET(&cs->cs_ip, lwip_htons((u16_t)tmp));
#else
IPH_LEN_SET(&cs->cs_ip, lwip_htons(n0->tot_len - vjlen + cs->cs_hlen));
#endif
/* recompute the ip header checksum */
bp = (struct vj_u16_t*) &cs->cs_ip;
IPH_CHKSUM_SET(&cs->cs_ip, 0);
for (tmp = 0; hlen > 0; hlen -= 2) {
tmp += (*bp++).v;
}
tmp = (tmp & 0xffff) + (tmp >> 16);
tmp = (tmp & 0xffff) + (tmp >> 16);
IPH_CHKSUM_SET(&cs->cs_ip, (u16_t)(~tmp));
/* Remove the compressed header and prepend the uncompressed header. */
if (pbuf_remove_header(n0, vjlen)) {
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_remove_header failed\n", 0);
goto bad;
}
if(LWIP_MEM_ALIGN(n0->payload) != n0->payload) {
struct pbuf *np;
#if IP_FORWARD
/* If IP forwarding is enabled we are using a PBUF_LINK packet type so
* the packet is being allocated with enough header space to be
* forwarded (to Ethernet for example).
*/
np = pbuf_alloc(PBUF_LINK, n0->len + cs->cs_hlen, PBUF_POOL);
#else /* IP_FORWARD */
np = pbuf_alloc(PBUF_RAW, n0->len + cs->cs_hlen, PBUF_POOL);
#endif /* IP_FORWARD */
if(!np) {
PPPDEBUG(LOG_WARNING, ("vj_uncompress_tcp: realign failed\n"));
goto bad;
}
if (pbuf_remove_header(np, cs->cs_hlen)) {
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_remove_header failed\n", 0);
goto bad;
}
pbuf_take(np, n0->payload, n0->len);
if(n0->next) {
pbuf_chain(np, n0->next);
pbuf_dechain(n0);
}
pbuf_free(n0);
n0 = np;
}
if (pbuf_add_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"));
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:
vj_uncompress_err(comp);
return (-1);
}
#endif /* PPP_SUPPORT && VJ_SUPPORT */