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1.1 root 1: /*-
1.1.1.2 root 2: * Copyright (c) 1989, 1991 Regents of the University of California.
1.1 root 3: * All rights reserved.
4: *
1.1.1.2 root 5: * Redistribution and use in source and binary forms are permitted
6: * provided that the above copyright notice and this paragraph are
7: * duplicated in all such forms and that any documentation,
8: * advertising materials, and other materials related to such
9: * distribution and use acknowledge that the software was developed
10: * by the University of California, Berkeley. The name of the
11: * University may not be used to endorse or promote products derived
12: * from this software without specific prior written permission.
13: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15: * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
1.1 root 16: *
1.1.1.2 root 17: * Van Jacobson ([email protected]), Dec 31, 1989:
18: * - Initial distribution.
1.1.1.3 ! root 19: *
! 20: * slcompress.c,v 1.3 1993/05/20 03:06:12 cgd Exp
1.1 root 21: */
1.1.1.2 root 22:
23: #include <sys/types.h>
1.1 root 24: #include <sys/param.h>
25: #include <sys/mbuf.h>
26: #include <netinet/in.h>
27: #include <netinet/in_systm.h>
28: #include <netinet/ip.h>
29: #include <netinet/tcp.h>
30:
31: #include "slcompress.h"
32:
33: #ifndef SL_NO_STATS
34: #define INCR(counter) ++comp->counter;
35: #else
36: #define INCR(counter)
37: #endif
38:
39: #define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))
40: #define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))
41: #ifndef KERNEL
42: #define ovbcopy bcopy
43: #endif
44:
45:
46: void
47: sl_compress_init(comp)
48: struct slcompress *comp;
49: {
50: register u_int i;
51: register struct cstate *tstate = comp->tstate;
52:
53: bzero((char *)comp, sizeof(*comp));
54: for (i = MAX_STATES - 1; i > 0; --i) {
55: tstate[i].cs_id = i;
56: tstate[i].cs_next = &tstate[i - 1];
57: }
58: tstate[0].cs_next = &tstate[MAX_STATES - 1];
59: tstate[0].cs_id = 0;
60: comp->last_cs = &tstate[0];
61: comp->last_recv = 255;
62: comp->last_xmit = 255;
1.1.1.2 root 63: comp->flags = SLF_TOSS;
1.1 root 64: }
65:
66:
67: /* ENCODE encodes a number that is known to be non-zero. ENCODEZ
68: * checks for zero (since zero has to be encoded in the long, 3 byte
69: * form).
70: */
71: #define ENCODE(n) { \
72: if ((u_short)(n) >= 256) { \
73: *cp++ = 0; \
74: cp[1] = (n); \
75: cp[0] = (n) >> 8; \
76: cp += 2; \
77: } else { \
78: *cp++ = (n); \
79: } \
80: }
81: #define ENCODEZ(n) { \
82: if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
83: *cp++ = 0; \
84: cp[1] = (n); \
85: cp[0] = (n) >> 8; \
86: cp += 2; \
87: } else { \
88: *cp++ = (n); \
89: } \
90: }
91:
92: #define DECODEL(f) { \
93: if (*cp == 0) {\
94: (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
95: cp += 3; \
96: } else { \
97: (f) = htonl(ntohl(f) + (u_long)*cp++); \
98: } \
99: }
100:
101: #define DECODES(f) { \
102: if (*cp == 0) {\
103: (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
104: cp += 3; \
105: } else { \
106: (f) = htons(ntohs(f) + (u_long)*cp++); \
107: } \
108: }
109:
110: #define DECODEU(f) { \
111: if (*cp == 0) {\
112: (f) = htons((cp[1] << 8) | cp[2]); \
113: cp += 3; \
114: } else { \
115: (f) = htons((u_long)*cp++); \
116: } \
117: }
118:
119:
120: u_char
121: sl_compress_tcp(m, ip, comp, compress_cid)
122: struct mbuf *m;
123: register struct ip *ip;
124: struct slcompress *comp;
125: int compress_cid;
126: {
127: register struct cstate *cs = comp->last_cs->cs_next;
128: register u_int hlen = ip->ip_hl;
129: register struct tcphdr *oth;
130: register struct tcphdr *th;
131: register u_int deltaS, deltaA;
132: register u_int changes = 0;
133: u_char new_seq[16];
134: register u_char *cp = new_seq;
135:
136: /*
137: * Bail if this is an IP fragment or if the TCP packet isn't
138: * `compressible' (i.e., ACK isn't set or some other control bit is
139: * set). (We assume that the caller has already made sure the
140: * packet is IP proto TCP).
141: */
142: if ((ip->ip_off & htons(0x3fff)) || m->m_len < 40)
143: return (TYPE_IP);
144:
145: th = (struct tcphdr *)&((int *)ip)[hlen];
146: if ((th->th_flags & (TH_SYN|TH_FIN|TH_RST|TH_ACK)) != TH_ACK)
147: return (TYPE_IP);
148: /*
149: * Packet is compressible -- we're going to send either a
150: * COMPRESSED_TCP or UNCOMPRESSED_TCP packet. Either way we need
151: * to locate (or create) the connection state. Special case the
152: * most recently used connection since it's most likely to be used
153: * again & we don't have to do any reordering if it's used.
154: */
155: INCR(sls_packets)
156: if (ip->ip_src.s_addr != cs->cs_ip.ip_src.s_addr ||
157: ip->ip_dst.s_addr != cs->cs_ip.ip_dst.s_addr ||
158: *(int *)th != ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl]) {
159: /*
160: * Wasn't the first -- search for it.
161: *
162: * States are kept in a circularly linked list with
163: * last_cs pointing to the end of the list. The
164: * list is kept in lru order by moving a state to the
165: * head of the list whenever it is referenced. Since
166: * the list is short and, empirically, the connection
167: * we want is almost always near the front, we locate
168: * states via linear search. If we don't find a state
169: * for the datagram, the oldest state is (re-)used.
170: */
171: register struct cstate *lcs;
172: register struct cstate *lastcs = comp->last_cs;
173:
174: do {
175: lcs = cs; cs = cs->cs_next;
176: INCR(sls_searches)
177: if (ip->ip_src.s_addr == cs->cs_ip.ip_src.s_addr
178: && ip->ip_dst.s_addr == cs->cs_ip.ip_dst.s_addr
179: && *(int *)th == ((int *)&cs->cs_ip)[cs->cs_ip.ip_hl])
180: goto found;
181: } while (cs != lastcs);
182:
183: /*
184: * Didn't find it -- re-use oldest cstate. Send an
185: * uncompressed packet that tells the other side what
186: * connection number we're using for this conversation.
187: * Note that since the state list is circular, the oldest
188: * state points to the newest and we only need to set
189: * last_cs to update the lru linkage.
190: */
191: INCR(sls_misses)
192: comp->last_cs = lcs;
193: hlen += th->th_off;
194: hlen <<= 2;
1.1.1.2 root 195: if (hlen > m->m_len)
196: return (TYPE_IP);
1.1 root 197: goto uncompressed;
198:
199: found:
200: /*
201: * Found it -- move to the front on the connection list.
202: */
203: if (cs == lastcs)
204: comp->last_cs = lcs;
205: else {
206: lcs->cs_next = cs->cs_next;
207: cs->cs_next = lastcs->cs_next;
208: lastcs->cs_next = cs;
209: }
210: }
211:
212: /*
213: * Make sure that only what we expect to change changed. The first
214: * line of the `if' checks the IP protocol version, header length &
215: * type of service. The 2nd line checks the "Don't fragment" bit.
216: * The 3rd line checks the time-to-live and protocol (the protocol
217: * check is unnecessary but costless). The 4th line checks the TCP
218: * header length. The 5th line checks IP options, if any. The 6th
219: * line checks TCP options, if any. If any of these things are
220: * different between the previous & current datagram, we send the
221: * current datagram `uncompressed'.
222: */
223: oth = (struct tcphdr *)&((int *)&cs->cs_ip)[hlen];
224: deltaS = hlen;
225: hlen += th->th_off;
226: hlen <<= 2;
1.1.1.2 root 227: if (hlen > m->m_len)
228: return (TYPE_IP);
1.1 root 229:
230: if (((u_short *)ip)[0] != ((u_short *)&cs->cs_ip)[0] ||
231: ((u_short *)ip)[3] != ((u_short *)&cs->cs_ip)[3] ||
232: ((u_short *)ip)[4] != ((u_short *)&cs->cs_ip)[4] ||
233: th->th_off != oth->th_off ||
234: (deltaS > 5 &&
235: BCMP(ip + 1, &cs->cs_ip + 1, (deltaS - 5) << 2)) ||
236: (th->th_off > 5 &&
237: BCMP(th + 1, oth + 1, (th->th_off - 5) << 2)))
238: goto uncompressed;
239:
240: /*
241: * Figure out which of the changing fields changed. The
242: * receiver expects changes in the order: urgent, window,
243: * ack, seq (the order minimizes the number of temporaries
244: * needed in this section of code).
245: */
246: if (th->th_flags & TH_URG) {
247: deltaS = ntohs(th->th_urp);
248: ENCODEZ(deltaS);
249: changes |= NEW_U;
250: } else if (th->th_urp != oth->th_urp)
251: /* argh! URG not set but urp changed -- a sensible
252: * implementation should never do this but RFC793
253: * doesn't prohibit the change so we have to deal
254: * with it. */
255: goto uncompressed;
256:
257: if (deltaS = (u_short)(ntohs(th->th_win) - ntohs(oth->th_win))) {
258: ENCODE(deltaS);
259: changes |= NEW_W;
260: }
261:
262: if (deltaA = ntohl(th->th_ack) - ntohl(oth->th_ack)) {
263: if (deltaA > 0xffff)
264: goto uncompressed;
265: ENCODE(deltaA);
266: changes |= NEW_A;
267: }
268:
269: if (deltaS = ntohl(th->th_seq) - ntohl(oth->th_seq)) {
270: if (deltaS > 0xffff)
271: goto uncompressed;
272: ENCODE(deltaS);
273: changes |= NEW_S;
274: }
275:
276: switch(changes) {
277:
278: case 0:
279: /*
280: * Nothing changed. If this packet contains data and the
281: * last one didn't, this is probably a data packet following
282: * an ack (normal on an interactive connection) and we send
283: * it compressed. Otherwise it's probably a retransmit,
284: * retransmitted ack or window probe. Send it uncompressed
285: * in case the other side missed the compressed version.
286: */
287: if (ip->ip_len != cs->cs_ip.ip_len &&
288: ntohs(cs->cs_ip.ip_len) == hlen)
289: break;
290:
291: /* (fall through) */
292:
293: case SPECIAL_I:
294: case SPECIAL_D:
295: /*
296: * actual changes match one of our special case encodings --
297: * send packet uncompressed.
298: */
299: goto uncompressed;
300:
301: case NEW_S|NEW_A:
302: if (deltaS == deltaA &&
303: deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
304: /* special case for echoed terminal traffic */
305: changes = SPECIAL_I;
306: cp = new_seq;
307: }
308: break;
309:
310: case NEW_S:
311: if (deltaS == ntohs(cs->cs_ip.ip_len) - hlen) {
312: /* special case for data xfer */
313: changes = SPECIAL_D;
314: cp = new_seq;
315: }
316: break;
317: }
318:
319: deltaS = ntohs(ip->ip_id) - ntohs(cs->cs_ip.ip_id);
320: if (deltaS != 1) {
321: ENCODEZ(deltaS);
322: changes |= NEW_I;
323: }
324: if (th->th_flags & TH_PUSH)
325: changes |= TCP_PUSH_BIT;
326: /*
327: * Grab the cksum before we overwrite it below. Then update our
328: * state with this packet's header.
329: */
330: deltaA = ntohs(th->th_sum);
331: BCOPY(ip, &cs->cs_ip, hlen);
332:
333: /*
334: * We want to use the original packet as our compressed packet.
335: * (cp - new_seq) is the number of bytes we need for compressed
336: * sequence numbers. In addition we need one byte for the change
337: * mask, one for the connection id and two for the tcp checksum.
338: * So, (cp - new_seq) + 4 bytes of header are needed. hlen is how
339: * many bytes of the original packet to toss so subtract the two to
340: * get the new packet size.
341: */
342: deltaS = cp - new_seq;
343: cp = (u_char *)ip;
344: if (compress_cid == 0 || comp->last_xmit != cs->cs_id) {
345: comp->last_xmit = cs->cs_id;
346: hlen -= deltaS + 4;
347: cp += hlen;
348: *cp++ = changes | NEW_C;
349: *cp++ = cs->cs_id;
350: } else {
351: hlen -= deltaS + 3;
352: cp += hlen;
353: *cp++ = changes;
354: }
355: m->m_len -= hlen;
356: m->m_data += hlen;
357: *cp++ = deltaA >> 8;
358: *cp++ = deltaA;
359: BCOPY(new_seq, cp, deltaS);
360: INCR(sls_compressed)
361: return (TYPE_COMPRESSED_TCP);
362:
363: /*
364: * Update connection state cs & send uncompressed packet ('uncompressed'
365: * means a regular ip/tcp packet but with the 'conversation id' we hope
366: * to use on future compressed packets in the protocol field).
367: */
368: uncompressed:
369: BCOPY(ip, &cs->cs_ip, hlen);
370: ip->ip_p = cs->cs_id;
371: comp->last_xmit = cs->cs_id;
372: return (TYPE_UNCOMPRESSED_TCP);
373: }
374:
375:
376: int
377: sl_uncompress_tcp(bufp, len, type, comp)
378: u_char **bufp;
379: int len;
380: u_int type;
381: struct slcompress *comp;
382: {
383: register u_char *cp;
384: register u_int hlen, changes;
385: register struct tcphdr *th;
386: register struct cstate *cs;
387: register struct ip *ip;
388:
389: switch (type) {
390:
391: case TYPE_UNCOMPRESSED_TCP:
392: ip = (struct ip *) *bufp;
393: if (ip->ip_p >= MAX_STATES)
394: goto bad;
395: cs = &comp->rstate[comp->last_recv = ip->ip_p];
396: comp->flags &=~ SLF_TOSS;
397: ip->ip_p = IPPROTO_TCP;
398: hlen = ip->ip_hl;
399: hlen += ((struct tcphdr *)&((int *)ip)[hlen])->th_off;
400: hlen <<= 2;
401: BCOPY(ip, &cs->cs_ip, hlen);
402: cs->cs_ip.ip_sum = 0;
403: cs->cs_hlen = hlen;
404: INCR(sls_uncompressedin)
405: return (len);
406:
407: default:
408: goto bad;
409:
410: case TYPE_COMPRESSED_TCP:
411: break;
412: }
413: /* We've got a compressed packet. */
414: INCR(sls_compressedin)
415: cp = *bufp;
416: changes = *cp++;
417: if (changes & NEW_C) {
418: /* Make sure the state index is in range, then grab the state.
419: * If we have a good state index, clear the 'discard' flag. */
420: if (*cp >= MAX_STATES)
421: goto bad;
422:
423: comp->flags &=~ SLF_TOSS;
424: comp->last_recv = *cp++;
425: } else {
426: /* this packet has an implicit state index. If we've
427: * had a line error since the last time we got an
428: * explicit state index, we have to toss the packet. */
429: if (comp->flags & SLF_TOSS) {
430: INCR(sls_tossed)
431: return (0);
432: }
433: }
434: cs = &comp->rstate[comp->last_recv];
435: hlen = cs->cs_ip.ip_hl << 2;
436: th = (struct tcphdr *)&((u_char *)&cs->cs_ip)[hlen];
437: th->th_sum = htons((*cp << 8) | cp[1]);
438: cp += 2;
439: if (changes & TCP_PUSH_BIT)
440: th->th_flags |= TH_PUSH;
441: else
442: th->th_flags &=~ TH_PUSH;
443:
444: switch (changes & SPECIALS_MASK) {
445: case SPECIAL_I:
446: {
447: register u_int i = ntohs(cs->cs_ip.ip_len) - cs->cs_hlen;
448: th->th_ack = htonl(ntohl(th->th_ack) + i);
449: th->th_seq = htonl(ntohl(th->th_seq) + i);
450: }
451: break;
452:
453: case SPECIAL_D:
454: th->th_seq = htonl(ntohl(th->th_seq) + ntohs(cs->cs_ip.ip_len)
455: - cs->cs_hlen);
456: break;
457:
458: default:
459: if (changes & NEW_U) {
460: th->th_flags |= TH_URG;
461: DECODEU(th->th_urp)
462: } else
463: th->th_flags &=~ TH_URG;
464: if (changes & NEW_W)
465: DECODES(th->th_win)
466: if (changes & NEW_A)
467: DECODEL(th->th_ack)
468: if (changes & NEW_S)
469: DECODEL(th->th_seq)
470: break;
471: }
472: if (changes & NEW_I) {
473: DECODES(cs->cs_ip.ip_id)
474: } else
475: cs->cs_ip.ip_id = htons(ntohs(cs->cs_ip.ip_id) + 1);
476:
477: /*
478: * At this point, cp points to the first byte of data in the
479: * packet. If we're not aligned on a 4-byte boundary, copy the
480: * data down so the ip & tcp headers will be aligned. Then back up
481: * cp by the tcp/ip header length to make room for the reconstructed
482: * header (we assume the packet we were handed has enough space to
483: * prepend 128 bytes of header). Adjust the length to account for
484: * the new header & fill in the IP total length.
485: */
486: len -= (cp - *bufp);
487: if (len < 0)
488: /* we must have dropped some characters (crc should detect
489: * this but the old slip framing won't) */
490: goto bad;
491:
492: if ((int)cp & 3) {
493: if (len > 0)
494: (void) ovbcopy(cp, (caddr_t)((int)cp &~ 3), len);
495: cp = (u_char *)((int)cp &~ 3);
496: }
497: cp -= cs->cs_hlen;
498: len += cs->cs_hlen;
499: cs->cs_ip.ip_len = htons(len);
500: BCOPY(&cs->cs_ip, cp, cs->cs_hlen);
501: *bufp = cp;
502:
503: /* recompute the ip header checksum */
504: {
505: register u_short *bp = (u_short *)cp;
506: for (changes = 0; hlen > 0; hlen -= 2)
507: changes += *bp++;
508: changes = (changes & 0xffff) + (changes >> 16);
509: changes = (changes & 0xffff) + (changes >> 16);
510: ((struct ip *)cp)->ip_sum = ~ changes;
511: }
512: return (len);
513: bad:
514: comp->flags |= SLF_TOSS;
515: INCR(sls_errorin)
516: return (0);
517: }
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