[apple/xnu.git] / bsd / netiso / iso_chksum.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)iso_chksum.c	8.1 (Berkeley) 6/10/93
 */

/***********************************************************
		Copyright IBM Corporation 1987

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the name of IBM not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  

IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/*
 * ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison
 */
/* 
 * ISO CHECKSUM
 *
 * The checksum generation and check routines are here.
 * The checksum is 2 bytes such that the sum of all the bytes b(i) == 0
 * and the sum of i * b(i) == 0.
 * The whole thing is complicated by the fact that the data are in mbuf
 * chains.
 * Furthermore, there is the possibility of wraparound in the running
 * sums after adding up 4102 octets.  In order to avoid doing a mod
 * operation after EACH add, we have restricted this implementation to 
 * negotiating a maximum of 4096-octets per TPDU (for the transport layer).
 * The routine iso_check_csum doesn't need to know where the checksum
 * octets are.
 * The routine iso_gen_csum takes a pointer to an mbuf chain (logically
 * a chunk of data), an offset into the chunk at which the 2 octets are to
 * be stuffed, and the length of the chunk.  The 2 octets have to be
 * logically adjacent, but may be physically located in separate mbufs.
 */

#include <sys/param.h>
#include <sys/systm.h>

#if ISO
#include <netiso/argo_debug.h>
#include <sys/mbuf.h>
#endif /* ISO */

#ifndef MNULL
#define MNULL (struct mbuf *)0
#endif /* MNULL */

/*
 * FUNCTION:	iso_check_csum
 *
 * PURPOSE:		To check the checksum of the packet in the mbuf chain (m).
 * 				The total length of the packet is (len).
 * 				Called from tp_input() and clnp_intr()
 *
 * RETURNS:		 TRUE (something non-zero) if there is a checksum error,
 * 			 	 FALSE if there was NO checksum error.
 *
 * SIDE EFFECTS:  none
 *
 * NOTES:		 It might be possible to gain something by optimizing
 *               this routine (unrolling loops, etc). But it is such
 *				 a horrible thing to fiddle with anyway, it probably
 *				 isn't worth it.
 */
int 
iso_check_csum(m, len)
	struct mbuf *m;
	int len;
{
	register u_char *p = mtod(m, u_char *);
	register u_long c0=0, c1=0;
	register int i=0;
	int cume = 0; /* cumulative length */
	int l;

	l = len;
	len = min(m->m_len, len);
	i = 0;

	IFDEBUG(D_CHKSUM)
		printf("iso_check_csum: m x%x, l x%x, m->m_len x%x\n", m, l, m->m_len);
	ENDDEBUG

	while( i<l ) {
		cume += len;
		while (i<cume) {
			c0 = c0 + *(p++);
			c1 += c0;
			i++;
		}
		if(i < l) {
			m = m->m_next;
			IFDEBUG(D_CHKSUM)
				printf("iso_check_csum: new mbuf\n");
				if(l-i < m->m_len)
					printf(
					"bad mbuf chain in check csum l 0x%x i 0x%x m_data 0x%x",
						l,i,m->m_data);
			ENDDEBUG
			ASSERT( m != MNULL);
			len = min( m->m_len, l-i);
			p = mtod(m, u_char *);
		}
	}
	if ( ((int)c0 % 255) || ((int)c1 % 255) ) {
		IFDEBUG(D_CHKSUM)
			printf("BAD iso_check_csum l 0x%x cume 0x%x len 0x%x, i 0x%x", 
				l, cume, len, i);
		ENDDEBUG
		return ((int)c0 % 255)<<8 | ((int)c1 % 255);
	}
	return 0;
}

/*
 * FUNCTION:	iso_gen_csum
 *
 * PURPOSE:		To generate the checksum of the packet in the mbuf chain (m).
 * 				The first of the 2 (logically) adjacent checksum bytes 
 *				(x and y) go at offset (n).
 * 				(n) is an offset relative to the beginning of the data, 
 *				not the beginning of the mbuf.
 * 				(l) is the length of the total mbuf chain's data.
 * 				Called from tp_emit(), tp_error_emit()
 *				clnp_emit_er(), clnp_forward(), clnp_output().
 *
 * RETURNS:		Rien
 *
 * SIDE EFFECTS: Puts the 2 checksum bytes into the packet.
 *
 * NOTES:		Ditto the note for iso_check_csum().
 */

void
iso_gen_csum(m,n,l)
	struct mbuf *m;
	int n; /* offset of 2 checksum bytes */
	int l;
{
	register u_char *p = mtod(m, u_char *);
	register int c0=0, c1=0;
	register int i=0;
	int loc = n++, len=0; /* n is position, loc is offset */
	u_char *xloc;
	u_char *yloc;
	int cume=0;	/* cume == cumulative length */

	IFDEBUG(D_CHKSUM)
		printf("enter gen csum m 0x%x n 0x%x l 0x%x\n",m, n-1 ,l );
	ENDDEBUG

	while(i < l) {
		len = min(m->m_len, CLBYTES);
		/* RAH: don't cksum more than l bytes */
		len = min(len, l - i);

		cume +=len;
		p = mtod(m, u_char *);

		if(loc>=0) {
			if (loc < len) {
				xloc = loc + mtod(m, u_char *);
				IFDEBUG(D_CHKSUM)
					printf("1: zeroing xloc 0x%x loc 0x%x\n",xloc, loc );
				ENDDEBUG
				*xloc = (u_char)0;
				if (loc+1 < len) {
					/* both xloc and yloc are in same mbuf */
					yloc = 1  + xloc;
					IFDEBUG(D_CHKSUM)
						printf("2: zeroing yloc 0x%x loc 0x%x\n",yloc, loc );
					ENDDEBUG
					*yloc = (u_char)0;
				} else {
					/* crosses boundary of mbufs */
					yloc = mtod(m->m_next, u_char *);
					IFDEBUG(D_CHKSUM)
						printf("3: zeroing yloc 0x%x \n",yloc );
					ENDDEBUG
					*yloc = (u_char)0;
				}
			}
			loc -= len;
		}

		while(i < cume) {
			c0 = (c0 + *p);
			c1 += c0 ;
			i++; 
			p++;
		}
		m = m->m_next;
	}
	IFDEBUG(D_CHKSUM)
		printf("gen csum final xloc 0x%x yloc 0x%x\n",xloc, yloc );
	ENDDEBUG

	c1 = (((c0 * (l-n))-c1)%255) ;
	*xloc = (u_char) ((c1 < 0)? c1+255 : c1);

	c1 = (-(int)(c1+c0))%255;
	*yloc = (u_char) (c1 < 0? c1 + 255 : c1);

	IFDEBUG(D_CHKSUM)
		printf("gen csum end \n");
	ENDDEBUG
}

/*
 * FUNCTION:	m_datalen
 *
 * PURPOSE:		returns length of the mbuf chain.
 * 				used all over the iso code.
 *
 * RETURNS:		integer
 *
 * SIDE EFFECTS: none
 *
 * NOTES:		
 */

int
m_datalen (m)
	register struct mbuf *m;
{ 	
	register int datalen;

	for (datalen = 0; m; m = m->m_next)
		datalen += m->m_len;
	return datalen;
}

int
m_compress(in, out)
	register struct mbuf *in, **out;
{
	register 	int datalen = 0;
	int	s = splimp();

	if( in->m_next == MNULL ) {
		*out = in;
		IFDEBUG(D_REQUEST)
			printf("m_compress returning 0x%x: A\n", in->m_len);
		ENDDEBUG
		splx(s);
		return in->m_len;
	}
	MGET((*out), M_DONTWAIT, MT_DATA);
	if((*out) == MNULL) {
		*out = in;
		IFDEBUG(D_REQUEST)
			printf("m_compress returning -1: B\n");
		ENDDEBUG
		splx(s);
		return -1; 
	}
	(*out)->m_len = 0;
	(*out)->m_act = MNULL;

	while (in) {
		IFDEBUG(D_REQUEST)
			printf("m_compress in 0x%x *out 0x%x\n", in, *out);
			printf("m_compress in: len 0x%x, off 0x%x\n", in->m_len, in->m_data);
			printf("m_compress *out: len 0x%x, off 0x%x\n", (*out)->m_len, 
				(*out)->m_data);
		ENDDEBUG
		if (in->m_flags & M_EXT) {
			ASSERT(in->m_len == 0);
		}
		if ( in->m_len == 0) {
			in = in->m_next;
			continue;
		}
		if (((*out)->m_flags & M_EXT) == 0) {
			int len;

			len = M_TRAILINGSPACE(*out);
			len = min(len, in->m_len);
			datalen += len;

			IFDEBUG(D_REQUEST)
				printf("m_compress copying len %d\n", len);
			ENDDEBUG
			bcopy(mtod(in, caddr_t), mtod((*out), caddr_t) + (*out)->m_len,
						(unsigned)len);

			(*out)->m_len += len;
			in->m_len -= len;
			continue;
		} else {
			/* (*out) is full */
			if(( (*out)->m_next = m_get(M_DONTWAIT, MT_DATA) ) == MNULL) {
				m_freem(*out);
				*out = in;
				IFDEBUG(D_REQUEST)
					printf("m_compress returning -1: B\n");
				ENDDEBUG
				splx(s);
				return -1;
			}
			(*out)->m_len = 0;
			(*out)->m_act = MNULL;
			*out = (*out)->m_next;
		}
	}
	m_freem(in);
	IFDEBUG(D_REQUEST)
		printf("m_compress returning 0x%x: A\n", datalen);
	ENDDEBUG
	splx(s);
	return datalen;
}
Commit	Line	Data
1c79356b A	1	/*
	2	* Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*-
	23	* Copyright (c) 1991, 1993
	24	* The Regents of the University of California. All rights reserved.
	25	*
	26	* Redistribution and use in source and binary forms, with or without
	27	* modification, are permitted provided that the following conditions
	28	* are met:
	29	* 1. Redistributions of source code must retain the above copyright
	30	* notice, this list of conditions and the following disclaimer.
	31	* 2. Redistributions in binary form must reproduce the above copyright
	32	* notice, this list of conditions and the following disclaimer in the
	33	* documentation and/or other materials provided with the distribution.
	34	* 3. All advertising materials mentioning features or use of this software
	35	* must display the following acknowledgement:
	36	* This product includes software developed by the University of
	37	* California, Berkeley and its contributors.
	38	* 4. Neither the name of the University nor the names of its contributors
	39	* may be used to endorse or promote products derived from this software
	40	* without specific prior written permission.
	41	*
	42	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	43	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	44	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	45	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	46	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	47	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	48	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	49	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	50	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	51	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	52	* SUCH DAMAGE.
	53	*
	54	* @(#)iso_chksum.c 8.1 (Berkeley) 6/10/93
	55	*/
	56
	57	/***********************************************************
	58	Copyright IBM Corporation 1987
	59
	60	All Rights Reserved
	61
	62	Permission to use, copy, modify, and distribute this software and its
	63	documentation for any purpose and without fee is hereby granted,
	64	provided that the above copyright notice appear in all copies and that
65	both that copyright notice and this permission notice appear in
66	supporting documentation, and that the name of IBM not be
67	used in advertising or publicity pertaining to distribution of the
68	software without specific, written prior permission.
69
70	IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
71	ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
72	IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
73	ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
74	WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
75	ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
76	SOFTWARE.
77
78	******************************************************************/
79
80	/*
81	* ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison
82	*/
83	/*
84	* ISO CHECKSUM
85	*
86	* The checksum generation and check routines are here.
87	* The checksum is 2 bytes such that the sum of all the bytes b(i) == 0
88	* and the sum of i * b(i) == 0.
89	* The whole thing is complicated by the fact that the data are in mbuf
90	* chains.
91	* Furthermore, there is the possibility of wraparound in the running
92	* sums after adding up 4102 octets. In order to avoid doing a mod
93	* operation after EACH add, we have restricted this implementation to
94	* negotiating a maximum of 4096-octets per TPDU (for the transport layer).
95	* The routine iso_check_csum doesn't need to know where the checksum
96	* octets are.
97	* The routine iso_gen_csum takes a pointer to an mbuf chain (logically
98	* a chunk of data), an offset into the chunk at which the 2 octets are to
99	* be stuffed, and the length of the chunk. The 2 octets have to be
100	* logically adjacent, but may be physically located in separate mbufs.
101	*/
102
103	#include <sys/param.h>
104	#include <sys/systm.h>
105
106	#if ISO
107	#include <netiso/argo_debug.h>
108	#include <sys/mbuf.h>
109	#endif /* ISO */
110
111	#ifndef MNULL
112	#define MNULL (struct mbuf *)0
113	#endif /* MNULL */
114
115	/*
116	* FUNCTION: iso_check_csum
117	*
118	* PURPOSE: To check the checksum of the packet in the mbuf chain (m).
119	* The total length of the packet is (len).
120	* Called from tp_input() and clnp_intr()
121	*
122	* RETURNS: TRUE (something non-zero) if there is a checksum error,
123	* FALSE if there was NO checksum error.
124	*
125	* SIDE EFFECTS: none
126	*
127	* NOTES: It might be possible to gain something by optimizing
128	* this routine (unrolling loops, etc). But it is such
129	* a horrible thing to fiddle with anyway, it probably
130	* isn't worth it.
131	*/
132	int
133	iso_check_csum(m, len)
134	struct mbuf *m;
135	int len;
136	{
137	register u_char p = mtod(m, u_char );
138	register u_long c0=0, c1=0;
139	register int i=0;
140	int cume = 0; /* cumulative length */
141	int l;
142
143	l = len;
144	len = min(m->m_len, len);
145	i = 0;
146
147	IFDEBUG(D_CHKSUM)
148	printf("iso_check_csum: m x%x, l x%x, m->m_len x%x\n", m, l, m->m_len);
149	ENDDEBUG
150
151	while( i<l ) {
152	cume += len;
153	while (i<cume) {
154	c0 = c0 + *(p++);
155	c1 += c0;
156	i++;
157	}
158	if(i < l) {
159	m = m->m_next;
160	IFDEBUG(D_CHKSUM)
161	printf("iso_check_csum: new mbuf\n");
162	if(l-i < m->m_len)
163	printf(
164	"bad mbuf chain in check csum l 0x%x i 0x%x m_data 0x%x",
165	l,i,m->m_data);
166	ENDDEBUG
167	ASSERT( m != MNULL);
168	len = min( m->m_len, l-i);
169	p = mtod(m, u_char *);
170	}
171	}
172	if ( ((int)c0 % 255) \|\| ((int)c1 % 255) ) {
173	IFDEBUG(D_CHKSUM)
174	printf("BAD iso_check_csum l 0x%x cume 0x%x len 0x%x, i 0x%x",
175	l, cume, len, i);
176	ENDDEBUG
177	return ((int)c0 % 255)<<8 \| ((int)c1 % 255);
178	}
179	return 0;
180	}
181
182	/*
183	* FUNCTION: iso_gen_csum
184	*
185	* PURPOSE: To generate the checksum of the packet in the mbuf chain (m).
186	* The first of the 2 (logically) adjacent checksum bytes
187	* (x and y) go at offset (n).
188	* (n) is an offset relative to the beginning of the data,
189	* not the beginning of the mbuf.
190	* (l) is the length of the total mbuf chain's data.
191	* Called from tp_emit(), tp_error_emit()
192	* clnp_emit_er(), clnp_forward(), clnp_output().
193	*
194	* RETURNS: Rien
195	*
196	* SIDE EFFECTS: Puts the 2 checksum bytes into the packet.
197	*
198	* NOTES: Ditto the note for iso_check_csum().
199	*/
200
201	void
202	iso_gen_csum(m,n,l)
203	struct mbuf *m;
204	int n; /* offset of 2 checksum bytes */
205	int l;
206	{
207	register u_char p = mtod(m, u_char );
208	register int c0=0, c1=0;
209	register int i=0;
210	int loc = n++, len=0; /* n is position, loc is offset */
211	u_char *xloc;
212	u_char *yloc;
213	int cume=0; /* cume == cumulative length */
214
215	IFDEBUG(D_CHKSUM)
216	printf("enter gen csum m 0x%x n 0x%x l 0x%x\n",m, n-1 ,l );
217	ENDDEBUG
218
219	while(i < l) {
220	len = min(m->m_len, CLBYTES);
221	/* RAH: don't cksum more than l bytes */
222	len = min(len, l - i);
223
224	cume +=len;
225	p = mtod(m, u_char *);
226
227	if(loc>=0) {
228	if (loc < len) {
229	xloc = loc + mtod(m, u_char *);
230	IFDEBUG(D_CHKSUM)
231	printf("1: zeroing xloc 0x%x loc 0x%x\n",xloc, loc );
232	ENDDEBUG
233	*xloc = (u_char)0;
234	if (loc+1 < len) {
235	/* both xloc and yloc are in same mbuf */
236	yloc = 1 + xloc;
237	IFDEBUG(D_CHKSUM)
238	printf("2: zeroing yloc 0x%x loc 0x%x\n",yloc, loc );
239	ENDDEBUG
240	*yloc = (u_char)0;
241	} else {
242	/* crosses boundary of mbufs */
243	yloc = mtod(m->m_next, u_char *);
244	IFDEBUG(D_CHKSUM)
245	printf("3: zeroing yloc 0x%x \n",yloc );
246	ENDDEBUG
247	*yloc = (u_char)0;
248	}
249	}
250	loc -= len;
251	}
252
253	while(i < cume) {
254	c0 = (c0 + *p);
255	c1 += c0 ;
256	i++;
257	p++;
258	}
259	m = m->m_next;
260	}
261	IFDEBUG(D_CHKSUM)
262	printf("gen csum final xloc 0x%x yloc 0x%x\n",xloc, yloc );
263	ENDDEBUG
264
265	c1 = (((c0 * (l-n))-c1)%255) ;
266	*xloc = (u_char) ((c1 < 0)? c1+255 : c1);
267
268	c1 = (-(int)(c1+c0))%255;
269	*yloc = (u_char) (c1 < 0? c1 + 255 : c1);
270
271	IFDEBUG(D_CHKSUM)
272	printf("gen csum end \n");
273	ENDDEBUG
274	}
275
276	/*
277	* FUNCTION: m_datalen
278	*
279	* PURPOSE: returns length of the mbuf chain.
280	* used all over the iso code.
281	*
282	* RETURNS: integer
283	*
284	* SIDE EFFECTS: none
285	*
286	* NOTES:
287	*/
288
289	int
290	m_datalen (m)
291	register struct mbuf *m;
292	{
293	register int datalen;
294
295	for (datalen = 0; m; m = m->m_next)
296	datalen += m->m_len;
297	return datalen;
298	}
299
300	int
301	m_compress(in, out)
302	register struct mbuf in, *out;
303	{
304	register int datalen = 0;
305	int s = splimp();
306
307	if( in->m_next == MNULL ) {
308	*out = in;
309	IFDEBUG(D_REQUEST)
310	printf("m_compress returning 0x%x: A\n", in->m_len);
311	ENDDEBUG
312	splx(s);
313	return in->m_len;
314	}
315	MGET((*out), M_DONTWAIT, MT_DATA);
316	if((*out) == MNULL) {
317	*out = in;
318	IFDEBUG(D_REQUEST)
319	printf("m_compress returning -1: B\n");
320	ENDDEBUG
321	splx(s);
322	return -1;
323	}
324	(*out)->m_len = 0;
325	(*out)->m_act = MNULL;
326
327	while (in) {
328	IFDEBUG(D_REQUEST)
329	printf("m_compress in 0x%x out 0x%x\n", in, out);
330	printf("m_compress in: len 0x%x, off 0x%x\n", in->m_len, in->m_data);
331	printf("m_compress out: len 0x%x, off 0x%x\n", (out)->m_len,
332	(*out)->m_data);
333	ENDDEBUG
334	if (in->m_flags & M_EXT) {
335	ASSERT(in->m_len == 0);
336	}
337	if ( in->m_len == 0) {
338	in = in->m_next;
339	continue;
340	}
341	if (((*out)->m_flags & M_EXT) == 0) {
342	int len;
343
344	len = M_TRAILINGSPACE(*out);
345	len = min(len, in->m_len);
346	datalen += len;
347
348	IFDEBUG(D_REQUEST)
349	printf("m_compress copying len %d\n", len);
350	ENDDEBUG
351	bcopy(mtod(in, caddr_t), mtod((out), caddr_t) + (out)->m_len,
352	(unsigned)len);
353
354	(*out)->m_len += len;
355	in->m_len -= len;
356	continue;
357	} else {
358	/* (out) is full /
359	if(( (*out)->m_next = m_get(M_DONTWAIT, MT_DATA) ) == MNULL) {
360	m_freem(*out);
361	*out = in;
362	IFDEBUG(D_REQUEST)
363	printf("m_compress returning -1: B\n");
364	ENDDEBUG
365	splx(s);
366	return -1;
367	}
368	(*out)->m_len = 0;
369	(*out)->m_act = MNULL;
370	out = (out)->m_next;
371	}
372	}
373	m_freem(in);
374	IFDEBUG(D_REQUEST)
375	printf("m_compress returning 0x%x: A\n", datalen);
376	ENDDEBUG
377	splx(s);
378	return datalen;
379	}