/* | |
* 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 <string.h> | |
#include "ppp.h" | |
#include "vj.h" | |
#include "pppdebug.h" | |
#if VJ_SUPPORT > 0 | |
#if LINK_STATS | |
#define INCR(counter) ++comp->stats.counter | |
#else | |
#define INCR(counter) | |
#endif | |
#if defined(NO_CHAR_BITFIELDS) | |
#define getip_hl(base) ((base).ip_hl_v&0xf) | |
#define getth_off(base) (((base).th_x2_off&0xf0)>>4) | |
#else | |
#define getip_hl(base) ((base).ip_hl) | |
#define getth_off(base) ((base).th_off) | |
#endif | |
void vj_compress_init(struct vjcompress *comp) | |
{ | |
register u_int i; | |
register 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 ((u_short)(n) >= 256) { \ | |
*cp++ = 0; \ | |
cp[1] = (n); \ | |
cp[0] = (n) >> 8; \ | |
cp += 2; \ | |
} else { \ | |
*cp++ = (n); \ | |
} \ | |
} | |
#define ENCODEZ(n) { \ | |
if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \ | |
*cp++ = 0; \ | |
cp[1] = (n); \ | |
cp[0] = (n) >> 8; \ | |
cp += 2; \ | |
} else { \ | |
*cp++ = (n); \ | |
} \ | |
} | |
#define DECODEL(f) { \ | |
if (*cp == 0) {\ | |
u32_t tmp = ntohl(f) + ((cp[1] << 8) | cp[2]); \ | |
(f) = htonl(tmp); \ | |
cp += 3; \ | |
} else { \ | |
u32_t tmp = ntohl(f) + (u32_t)*cp++; \ | |
(f) = htonl(tmp); \ | |
} \ | |
} | |
#define DECODES(f) { \ | |
if (*cp == 0) {\ | |
u_short tmp = ntohs(f) + (((u_short)cp[1] << 8) | cp[2]); \ | |
(f) = htons(tmp); \ | |
cp += 3; \ | |
} else { \ | |
u_short tmp = ntohs(f) + (u_short)*cp++; \ | |
(f) = htons(tmp); \ | |
} \ | |
} | |
#define DECODEU(f) { \ | |
if (*cp == 0) {\ | |
(f) = htons(((u_short)cp[1] << 8) | cp[2]); \ | |
cp += 3; \ | |
} else { \ | |
(f) = htons((u_short)*cp++); \ | |
} \ | |
} | |
/* | |
* vj_compress_tcp - Attempt to do Van Jacobsen 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. | |
*/ | |
u_int vj_compress_tcp( | |
struct vjcompress *comp, | |
struct pbuf *pb | |
) | |
{ | |
register struct ip *ip = (struct ip *)pb->payload; | |
register struct cstate *cs = comp->last_cs->cs_next; | |
register u_short hlen = getip_hl(*ip); | |
register struct tcphdr *oth; | |
register struct tcphdr *th; | |
register u_short deltaS, deltaA; | |
register u_long deltaL; | |
register u_int changes = 0; | |
u_char new_seq[16]; | |
register u_char *cp = new_seq; | |
/* | |
* Check that the packet is IP proto TCP. | |
*/ | |
if (ip->ip_p != IPPROTO_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 ((ip->ip_off & htons(0x3fff)) || pb->tot_len < 40) | |
return (TYPE_IP); | |
th = (struct tcphdr *)&((long *)ip)[hlen]; | |
if ((th->th_flags & (TCP_SYN|TCP_FIN|TCP_RST|TCP_ACK)) != TCP_ACK) | |
return (TYPE_IP); | |
/* | |
* 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 (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr | |
|| ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr | |
|| *(long *)th != ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) { | |
/* | |
* 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. | |
*/ | |
register struct cstate *lcs; | |
register struct cstate *lastcs = comp->last_cs; | |
do { | |
lcs = cs; cs = cs->cs_next; | |
INCR(vjs_searches); | |
if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr | |
&& ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr | |
&& *(long *)th == ((long *)&cs->cs_ip)[getip_hl(cs->cs_ip)]) | |
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; | |
hlen += getth_off(*th); | |
hlen <<= 2; | |
/* Check that the IP/TCP headers are contained in the first buffer. */ | |
if (hlen > pb->len) | |
return (TYPE_IP); | |
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 tcphdr *)&((long *)&cs->cs_ip)[hlen]; | |
deltaS = hlen; | |
hlen += getth_off(*th); | |
hlen <<= 2; | |
/* Check that the IP/TCP headers are contained in the first buffer. */ | |
if (hlen > pb->len) { | |
PPPDEBUG((LOG_INFO, "vj_compress_tcp: header len %d spans buffers\n", | |
hlen)); | |
return (TYPE_IP); | |
} | |
/* | |
* 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 (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] | |
|| ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] | |
|| ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] | |
|| getth_off(*th) != getth_off(*oth) | |
|| (deltaS > 5 && BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) | |
|| (getth_off(*th) > 5 && BCMP(th + 1, oth + 1, (getth_off(*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 (th->th_flags & TCP_URG) { | |
deltaS = ntohs(th->th_urp); | |
ENCODEZ(deltaS); | |
changes |= NEW_U; | |
} else if (th->th_urp != oth->th_urp) | |
/* 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 = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) != 0) { | |
ENCODE(deltaS); | |
changes |= NEW_W; | |
} | |
if ((deltaL = ntohl(th->th_ack) - ntohl(oth->th_ack)) != 0) { | |
if (deltaL > 0xffff) | |
goto uncompressed; | |
deltaA = (u_short)deltaL; | |
ENCODE(deltaA); | |
changes |= NEW_A; | |
} | |
if ((deltaL = ntohl(th->th_seq) - ntohl(oth->th_seq)) != 0) { | |
if (deltaL > 0xffff) | |
goto uncompressed; | |
deltaS = (u_short)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 (ip->ip_len != cs->cs_ip.ip_len && | |
ntohs(cs->cs_ip.ip_len) == hlen) | |
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 == ntohs(cs->cs_ip.ip_len) - hlen) { | |
/* special case for echoed terminal traffic */ | |
changes = SPECIAL_I; | |
cp = new_seq; | |
} | |
break; | |
case NEW_S: | |
if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) { | |
/* special case for data xfer */ | |
changes = SPECIAL_D; | |
cp = new_seq; | |
} | |
break; | |
} | |
deltaS = (u_short)(ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id)); | |
if (deltaS != 1) { | |
ENCODEZ(deltaS); | |
changes |= NEW_I; | |
} | |
if (th->th_flags & TCP_PSH) | |
changes |= TCP_PUSH_BIT; | |
/* | |
* Grab the cksum before we overwrite it below. Then update our | |
* state with this packet's header. | |
*/ | |
deltaA = ntohs(th->th_sum); | |
BCOPY(ip, &cs->cs_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 = (u_short)(cp - new_seq); | |
if (!comp->compressSlot || comp->last_xmit != cs->cs_id) { | |
comp->last_xmit = cs->cs_id; | |
hlen -= deltaS + 4; | |
pbuf_header(pb, -hlen); | |
cp = (u_char *)pb->payload; | |
*cp++ = changes | NEW_C; | |
*cp++ = cs->cs_id; | |
} else { | |
hlen -= deltaS + 3; | |
pbuf_header(pb, -hlen); | |
cp = (u_char *)pb->payload; | |
*cp++ = changes; | |
} | |
*cp++ = deltaA >> 8; | |
*cp++ = deltaA; | |
BCOPY(new_seq, cp, 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: | |
BCOPY(ip, &cs->cs_ip, hlen); | |
ip->ip_p = 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 | |
) | |
{ | |
register u_int hlen; | |
register struct cstate *cs; | |
register struct ip *ip; | |
ip = (struct ip *)nb->payload; | |
hlen = getip_hl(*ip) << 2; | |
if (ip->ip_p >= MAX_SLOTS | |
|| hlen + sizeof(struct tcphdr) > nb->len | |
|| (hlen += getth_off(*((struct tcphdr *)&((char *)ip)[hlen])) << 2) | |
> nb->len | |
|| hlen > MAX_HDR) { | |
PPPDEBUG((LOG_INFO, "vj_uncompress_uncomp: bad cid=%d, hlen=%d buflen=%d\n", | |
ip->ip_p, hlen, nb->len)); | |
comp->flags |= VJF_TOSS; | |
INCR(vjs_errorin); | |
return -1; | |
} | |
cs = &comp->rstate[comp->last_recv = ip->ip_p]; | |
comp->flags &=~ VJF_TOSS; | |
ip->ip_p = IPPROTO_TCP; | |
BCOPY(ip, &cs->cs_ip, hlen); | |
cs->cs_hlen = 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 | |
) | |
{ | |
u_char *cp; | |
struct tcphdr *th; | |
struct cstate *cs; | |
u_short *bp; | |
struct pbuf *n0 = *nb; | |
u32_t tmp; | |
u_int vjlen, hlen, changes; | |
INCR(vjs_compressedin); | |
cp = (u_char *)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 = 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 | |