aboutsummaryrefslogtreecommitdiff
path: root/drivers/sk98lin/skcsum.c
blob: a5dc572587eb74b56f1ac631e4f89059899aa706 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
/******************************************************************************
 *
 * Name:	skcsum.c
 * Project:	GEnesis, PCI Gigabit Ethernet Adapter
 * Version:	$Revision: 1.10 $
 * Date:	$Date: 2002/04/11 10:02:04 $
 * Purpose:	Store/verify Internet checksum in send/receive packets.
 *
 ******************************************************************************/

/******************************************************************************
 *
 *	(C)Copyright 1998-2001 SysKonnect GmbH.
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *
 *	The information in this file is provided "AS IS" without warranty.
 *
 ******************************************************************************/

/******************************************************************************
 *
 * History:
 *
 *	$Log: skcsum.c,v $
 *	Revision 1.10  2002/04/11 10:02:04  rwahl
 *	Fix in SkCsGetSendInfo():
 *	- function did not return ProtocolFlags in every case.
 *	- pseudo header csum calculated wrong for big endian.
 *
 *	Revision 1.9  2001/06/13 07:42:08  gklug
 *	fix: NetNumber was wrong in CLEAR_STAT event
 *	add: check for good NetNumber in Clear STAT
 *
 *	Revision 1.8  2001/02/06 11:15:36  rassmann
 *	Supporting two nets on dual-port adapters.
 *
 *	Revision 1.7  2000/06/29 13:17:05  rassmann
 *	Corrected reception of a packet with UDP checksum == 0 (which means there
 *	is no UDP checksum).
 *
 *	Revision 1.6  2000/02/21 12:35:10  cgoos
 *	Fixed license header comment.
 *
 *	Revision 1.5  2000/02/21 11:05:19  cgoos
 *	Merged changes back to common source.
 *	Fixed rx path for BIG ENDIAN architecture.
 *
 *	Revision 1.1  1999/07/26 15:28:12  mkarl
 *	added return SKCS_STATUS_IP_CSUM_ERROR_UDP and
 *	SKCS_STATUS_IP_CSUM_ERROR_TCP to pass the NidsTester
 *	changed from common source to windows specific source
 *	therefore restarting with v1.0
 *
 *	Revision 1.3  1999/05/10 08:39:33  mkarl
 *	prevent overflows in SKCS_HTON16
 *	fixed a bug in pseudo header checksum calculation
 *	added some comments
 *
 *	Revision 1.2  1998/10/22 11:53:28  swolf
 *	Now using SK_DBG_MSG.
 *
 *	Revision 1.1  1998/09/01 15:35:41  swolf
 *	initial revision
 *
 *	13-May-1998 sw	Created.
 *
 ******************************************************************************/

#include <config.h>

#ifdef CONFIG_SK98

#ifdef SK_USE_CSUM	/* Check if CSUM is to be used. */

#ifndef lint
static const char SysKonnectFileId[] = "@(#)"
	"$Id: skcsum.c,v 1.10 2002/04/11 10:02:04 rwahl Exp $"
	" (C) SysKonnect.";
#endif	/* !lint */

/******************************************************************************
 *
 * Description:
 *
 * This is the "GEnesis" common module "CSUM".
 *
 * This module contains the code necessary to calculate, store, and verify the
 * Internet Checksum of IP, TCP, and UDP frames.
 *
 * "GEnesis" is an abbreviation of "Gigabit Ethernet Network System in Silicon"
 * and is the code name of this SysKonnect project.
 *
 * Compilation Options:
 *
 *	SK_USE_CSUM - Define if CSUM is to be used. Otherwise, CSUM will be an
 *	empty module.
 *
 *	SKCS_OVERWRITE_PROTO - Define to overwrite the default protocol id
 *	definitions. In this case, all SKCS_PROTO_xxx definitions must be made
 *	external.
 *
 *	SKCS_OVERWRITE_STATUS - Define to overwrite the default return status
 *	definitions. In this case, all SKCS_STATUS_xxx definitions must be made
 *	external.
 *
 * Include File Hierarchy:
 *
 *	"h/skdrv1st.h"
 *	"h/skcsum.h"
 *	 "h/sktypes.h"
 *	 "h/skqueue.h"
 *	"h/skdrv2nd.h"
 *
 ******************************************************************************/

#include "h/skdrv1st.h"
#include "h/skcsum.h"
#include "h/skdrv2nd.h"

/* defines ********************************************************************/

/* The size of an Ethernet MAC header. */
#define SKCS_ETHERNET_MAC_HEADER_SIZE			(6+6+2)

/* The size of the used topology's MAC header. */
#define	SKCS_MAC_HEADER_SIZE	SKCS_ETHERNET_MAC_HEADER_SIZE

/* The size of the IP header without any option fields. */
#define SKCS_IP_HEADER_SIZE						20

/*
 * Field offsets within the IP header.
 */

/* "Internet Header Version" and "Length". */
#define SKCS_OFS_IP_HEADER_VERSION_AND_LENGTH	0

/* "Total Length". */
#define SKCS_OFS_IP_TOTAL_LENGTH				2

/* "Flags" "Fragment Offset". */
#define SKCS_OFS_IP_FLAGS_AND_FRAGMENT_OFFSET	6

/* "Next Level Protocol" identifier. */
#define SKCS_OFS_IP_NEXT_LEVEL_PROTOCOL			9

/* Source IP address. */
#define SKCS_OFS_IP_SOURCE_ADDRESS				12

/* Destination IP address. */
#define SKCS_OFS_IP_DESTINATION_ADDRESS			16


/*
 * Field offsets within the UDP header.
 */

/* UDP checksum. */
#define SKCS_OFS_UDP_CHECKSUM					6

/* IP "Next Level Protocol" identifiers (see RFC 790). */
#define SKCS_PROTO_ID_TCP		6	/* Transport Control Protocol */
#define SKCS_PROTO_ID_UDP		17	/* User Datagram Protocol */

/* IP "Don't Fragment" bit. */
#define SKCS_IP_DONT_FRAGMENT	SKCS_HTON16(0x4000)

/* Add a byte offset to a pointer. */
#define SKCS_IDX(pPtr, Ofs)	((void *) ((char *) (pPtr) + (Ofs)))

/*
 * Macros that convert host to network representation and vice versa, i.e.
 * little/big endian conversion on little endian machines only.
 */
#ifdef SK_LITTLE_ENDIAN
#define SKCS_HTON16(Val16)	(((unsigned) (Val16) >> 8) | (((Val16) & 0xFF) << 8))
#endif	/* SK_LITTLE_ENDIAN */
#ifdef SK_BIG_ENDIAN
#define SKCS_HTON16(Val16)	(Val16)
#endif	/* SK_BIG_ENDIAN */
#define SKCS_NTOH16(Val16)	SKCS_HTON16(Val16)

/* typedefs *******************************************************************/

/* function prototypes ********************************************************/

/******************************************************************************
 *
 *	SkCsGetSendInfo - get checksum information for a send packet
 *
 * Description:
 *	Get all checksum information necessary to send a TCP or UDP packet. The
 *	function checks the IP header passed to it. If the high-level protocol
 *	is either TCP or UDP the pseudo header checksum is calculated and
 *	returned.
 *
 *	The function returns the total length of the IP header (including any
 *	IP option fields), which is the same as the start offset of the IP data
 *	which in turn is the start offset of the TCP or UDP header.
 *
 *	The function also returns the TCP or UDP pseudo header checksum, which
 *	should be used as the start value for the hardware checksum calculation.
 *	(Note that any actual pseudo header checksum can never calculate to
 *	zero.)
 *
 * Note:
 *	There is a bug in the ASIC which may lead to wrong checksums.
 *
 * Arguments:
 *	pAc - A pointer to the adapter context struct.
 *
 *	pIpHeader - Pointer to IP header. Must be at least the IP header *not*
 *	including any option fields, i.e. at least 20 bytes.
 *
 *	Note: This pointer will be used to address 8-, 16-, and 32-bit
 *	variables with the respective alignment offsets relative to the pointer.
 *	Thus, the pointer should point to a 32-bit aligned address. If the
 *	target system cannot address 32-bit variables on non 32-bit aligned
 *	addresses, then the pointer *must* point to a 32-bit aligned address.
 *
 *	pPacketInfo - A pointer to the packet information structure for this
 *	packet. Before calling this SkCsGetSendInfo(), the following field must
 *	be initialized:
 *
 *		ProtocolFlags - Initialize with any combination of
 *		SKCS_PROTO_XXX bit flags. SkCsGetSendInfo() will only work on
 *		the protocols specified here. Any protocol(s) not specified
 *		here will be ignored.
 *
 *		Note: Only one checksum can be calculated in hardware. Thus, if
 *		SKCS_PROTO_IP is specified in the 'ProtocolFlags',
 *		SkCsGetSendInfo() must calculate the IP header checksum in
 *		software. It might be a better idea to have the calling
 *		protocol stack calculate the IP header checksum.
 *
 * Returns: N/A
 *	On return, the following fields in 'pPacketInfo' may or may not have
 *	been filled with information, depending on the protocol(s) found in the
 *	packet:
 *
 *	ProtocolFlags - Returns the SKCS_PROTO_XXX bit flags of the protocol(s)
 *	that were both requested by the caller and actually found in the packet.
 *	Protocol(s) not specified by the caller and/or not found in the packet
 *	will have their respective SKCS_PROTO_XXX bit flags reset.
 *
 *	Note: For IP fragments, TCP and UDP packet information is ignored.
 *
 *	IpHeaderLength - The total length in bytes of the complete IP header
 *	including any option fields is returned here. This is the start offset
 *	of the IP data, i.e. the TCP or UDP header if present.
 *
 *	IpHeaderChecksum - If IP has been specified in the 'ProtocolFlags', the
 *	16-bit Internet Checksum of the IP header is returned here. This value
 *	is to be stored into the packet's 'IP Header Checksum' field.
 *
 *	PseudoHeaderChecksum - If this is a TCP or UDP packet and if TCP or UDP
 *	has been specified in the 'ProtocolFlags', the 16-bit Internet Checksum
 *	of the TCP or UDP pseudo header is returned here.
 */
#if 0
void SkCsGetSendInfo(
SK_AC				*pAc,			/* Adapter context struct. */
void				*pIpHeader,		/* IP header. */
SKCS_PACKET_INFO	*pPacketInfo,	/* Packet information struct. */
int					NetNumber)		/* Net number */
{
	/* Internet Header Version found in IP header. */
	unsigned InternetHeaderVersion;

	/* Length of the IP header as found in IP header. */
	unsigned IpHeaderLength;

	/* Bit field specifiying the desired/found protocols. */
	unsigned ProtocolFlags;

	/* Next level protocol identifier found in IP header. */
	unsigned NextLevelProtocol;

	/* Length of IP data portion. */
	unsigned IpDataLength;

	/* TCP/UDP pseudo header checksum. */
	unsigned long PseudoHeaderChecksum;

	/* Pointer to next level protocol statistics structure. */
	SKCS_PROTO_STATS *NextLevelProtoStats;

	/* Temporary variable. */
	unsigned Tmp;

	Tmp = *(SK_U8 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_HEADER_VERSION_AND_LENGTH);

	/* Get the Internet Header Version (IHV). */
	/* Note: The IHV is stored in the upper four bits. */

	InternetHeaderVersion = Tmp >> 4;

	/* Check the Internet Header Version. */
	/* Note: We currently only support IP version 4. */

	if (InternetHeaderVersion != 4) {	/* IPv4? */
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_TX,
			("Tx: Unknown Internet Header Version %u.\n",
			InternetHeaderVersion));
		pPacketInfo->ProtocolFlags = 0;
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxUnableCts++;
		return;
	}

	/* Get the IP header length (IHL). */
	/*
	 * Note: The IHL is stored in the lower four bits as the number of
	 * 4-byte words.
	 */

	IpHeaderLength = (Tmp & 0xf) * 4;
	pPacketInfo->IpHeaderLength = IpHeaderLength;

	/* Check the IP header length. */

	/* 04-Aug-1998 sw - Really check the IHL? Necessary? */

	if (IpHeaderLength < 5*4) {
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_TX,
			("Tx: Invalid IP Header Length %u.\n", IpHeaderLength));
		pPacketInfo->ProtocolFlags = 0;
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxUnableCts++;
		return;
	}

	/* This is an IPv4 frame with a header of valid length. */

	pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxOkCts++;

	/* Check if we should calculate the IP header checksum. */

	ProtocolFlags = pPacketInfo->ProtocolFlags;

	if (ProtocolFlags & SKCS_PROTO_IP) {
		pPacketInfo->IpHeaderChecksum =
			SkCsCalculateChecksum(pIpHeader, IpHeaderLength);
	}

	/* Get the next level protocol identifier. */

	NextLevelProtocol =
		*(SK_U8 *) SKCS_IDX(pIpHeader, SKCS_OFS_IP_NEXT_LEVEL_PROTOCOL);

	/*
	 * Check if this is a TCP or UDP frame and if we should calculate the
	 * TCP/UDP pseudo header checksum.
	 *
	 * Also clear all protocol bit flags of protocols not present in the
	 * frame.
	 */

	if ((ProtocolFlags & SKCS_PROTO_TCP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_TCP) {
		/* TCP/IP frame. */
		ProtocolFlags &= SKCS_PROTO_TCP | SKCS_PROTO_IP;
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_TCP];
	}
	else if ((ProtocolFlags & SKCS_PROTO_UDP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_UDP) {
		/* UDP/IP frame. */
		ProtocolFlags &= SKCS_PROTO_UDP | SKCS_PROTO_IP;
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_UDP];
	}
	else {
		/*
		 * Either not a TCP or UDP frame and/or TCP/UDP processing not
		 * specified.
		 */
		pPacketInfo->ProtocolFlags = ProtocolFlags & SKCS_PROTO_IP;
		return;
	}

	/* Check if this is an IP fragment. */

	/*
	 * Note: An IP fragment has a non-zero "Fragment Offset" field and/or
	 * the "More Fragments" bit set. Thus, if both the "Fragment Offset"
	 * and the "More Fragments" are zero, it is *not* a fragment. We can
	 * easily check both at the same time since they are in the same 16-bit
	 * word.
	 */

	if ((*(SK_U16 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_FLAGS_AND_FRAGMENT_OFFSET) &
		~SKCS_IP_DONT_FRAGMENT) != 0) {
		/* IP fragment; ignore all other protocols. */
		pPacketInfo->ProtocolFlags = ProtocolFlags & SKCS_PROTO_IP;
		NextLevelProtoStats->TxUnableCts++;
		return;
	}

	/*
	 * Calculate the TCP/UDP pseudo header checksum.
	 */

	/* Get total length of IP header and data. */

	IpDataLength =
		*(SK_U16 *) SKCS_IDX(pIpHeader, SKCS_OFS_IP_TOTAL_LENGTH);

	/* Get length of IP data portion. */

	IpDataLength = SKCS_NTOH16(IpDataLength) - IpHeaderLength;

	/* Calculate the sum of all pseudo header fields (16-bit). */

	PseudoHeaderChecksum =
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 2) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 2) +
		(unsigned long) SKCS_HTON16(NextLevelProtocol) +
		(unsigned long) SKCS_HTON16(IpDataLength);

	/* Add-in any carries. */

	SKCS_OC_ADD(PseudoHeaderChecksum, PseudoHeaderChecksum, 0);

	/* Add-in any new carry. */

	SKCS_OC_ADD(pPacketInfo->PseudoHeaderChecksum, PseudoHeaderChecksum, 0);

	pPacketInfo->ProtocolFlags = ProtocolFlags;
	NextLevelProtoStats->TxOkCts++;	/* Success. */
}	/* SkCsGetSendInfo */


/******************************************************************************
 *
 *	SkCsGetReceiveInfo - verify checksum information for a received packet
 *
 * Description:
 *	Verify a received frame's checksum. The function returns a status code
 *	reflecting the result of the verification.
 *
 * Note:
 *	Before calling this function you have to verify that the frame is
 *	not padded and Checksum1 and Checksum2 are bigger than 1.
 *
 * Arguments:
 *	pAc - Pointer to adapter context struct.
 *
 *	pIpHeader - Pointer to IP header. Must be at least the length in bytes
 *	of the received IP header including any option fields. For UDP packets,
 *	8 additional bytes are needed to access the UDP checksum.
 *
 *	Note: The actual length of the IP header is stored in the lower four
 *	bits of the first octet of the IP header as the number of 4-byte words,
 *	so it must be multiplied by four to get the length in bytes. Thus, the
 *	maximum IP header length is 15 * 4 = 60 bytes.
 *
 *	Checksum1 - The first 16-bit Internet Checksum calculated by the
 *	hardware starting at the offset returned by SkCsSetReceiveFlags().
 *
 *	Checksum2 - The second 16-bit Internet Checksum calculated by the
 *	hardware starting at the offset returned by SkCsSetReceiveFlags().
 *
 * Returns:
 *	SKCS_STATUS_UNKNOWN_IP_VERSION - Not an IP v4 frame.
 *	SKCS_STATUS_IP_CSUM_ERROR - IP checksum error.
 *	SKCS_STATUS_IP_CSUM_ERROR_TCP - IP checksum error in TCP frame.
 *	SKCS_STATUS_IP_CSUM_ERROR_UDP - IP checksum error in UDP frame
 *	SKCS_STATUS_IP_FRAGMENT - IP fragment (IP checksum ok).
 *	SKCS_STATUS_IP_CSUM_OK - IP checksum ok (not a TCP or UDP frame).
 *	SKCS_STATUS_TCP_CSUM_ERROR - TCP checksum error (IP checksum ok).
 *	SKCS_STATUS_UDP_CSUM_ERROR - UDP checksum error (IP checksum ok).
 *	SKCS_STATUS_TCP_CSUM_OK - IP and TCP checksum ok.
 *	SKCS_STATUS_UDP_CSUM_OK - IP and UDP checksum ok.
 *	SKCS_STATUS_IP_CSUM_OK_NO_UDP - IP checksum OK and no UDP checksum.
 *
 *	Note: If SKCS_OVERWRITE_STATUS is defined, the SKCS_STATUS_XXX values
 *	returned here can be defined in some header file by the module using CSUM.
 *	In this way, the calling module can assign return values for its own needs,
 *	e.g. by assigning bit flags to the individual protocols.
 */
SKCS_STATUS SkCsGetReceiveInfo(
SK_AC		*pAc,		/* Adapter context struct. */
void		*pIpHeader,	/* IP header. */
unsigned	Checksum1,	/* Hardware checksum 1. */
unsigned	Checksum2,	/* Hardware checksum 2. */
int			NetNumber)	/* Net number */
{
	/* Internet Header Version found in IP header. */
	unsigned InternetHeaderVersion;

	/* Length of the IP header as found in IP header. */
	unsigned IpHeaderLength;

	/* Length of IP data portion. */
	unsigned IpDataLength;

	/* IP header checksum. */
	unsigned IpHeaderChecksum;

	/* IP header options checksum, if any. */
	unsigned IpOptionsChecksum;

	/* IP data checksum, i.e. TCP/UDP checksum. */
	unsigned IpDataChecksum;

	/* Next level protocol identifier found in IP header. */
	unsigned NextLevelProtocol;

	/* The checksum of the "next level protocol", i.e. TCP or UDP. */
	unsigned long NextLevelProtocolChecksum;

	/* Pointer to next level protocol statistics structure. */
	SKCS_PROTO_STATS *NextLevelProtoStats;

	/* Temporary variable. */
	unsigned Tmp;

	Tmp = *(SK_U8 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_HEADER_VERSION_AND_LENGTH);

	/* Get the Internet Header Version (IHV). */
	/* Note: The IHV is stored in the upper four bits. */

	InternetHeaderVersion = Tmp >> 4;

	/* Check the Internet Header Version. */
	/* Note: We currently only support IP version 4. */

	if (InternetHeaderVersion != 4) {	/* IPv4? */
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_RX,
			("Rx: Unknown Internet Header Version %u.\n",
			InternetHeaderVersion));
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].RxUnableCts++;
		return (SKCS_STATUS_UNKNOWN_IP_VERSION);
	}

	/* Get the IP header length (IHL). */
	/*
	 * Note: The IHL is stored in the lower four bits as the number of
	 * 4-byte words.
	 */

	IpHeaderLength = (Tmp & 0xf) * 4;

	/* Check the IP header length. */

	/* 04-Aug-1998 sw - Really check the IHL? Necessary? */

	if (IpHeaderLength < 5*4) {
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_RX,
			("Rx: Invalid IP Header Length %u.\n", IpHeaderLength));
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].RxErrCts++;
		return (SKCS_STATUS_IP_CSUM_ERROR);
	}

	/* This is an IPv4 frame with a header of valid length. */

	/* Get the IP header and data checksum. */

	IpDataChecksum = Checksum2;

	/*
	 * The IP header checksum is calculated as follows:
	 *
	 *	IpHeaderChecksum = Checksum1 - Checksum2
	 */

	SKCS_OC_SUB(IpHeaderChecksum, Checksum1, Checksum2);

	/* Check if any IP header options. */

	if (IpHeaderLength > SKCS_IP_HEADER_SIZE) {

		/* Get the IP options checksum. */

		IpOptionsChecksum = SkCsCalculateChecksum(
			SKCS_IDX(pIpHeader, SKCS_IP_HEADER_SIZE),
			IpHeaderLength - SKCS_IP_HEADER_SIZE);

		/* Adjust the IP header and IP data checksums. */

		SKCS_OC_ADD(IpHeaderChecksum, IpHeaderChecksum, IpOptionsChecksum);

		SKCS_OC_SUB(IpDataChecksum, IpDataChecksum, IpOptionsChecksum);
	}

	/*
	 * Check if the IP header checksum is ok.
	 *
	 * NOTE: We must check the IP header checksum even if the caller just wants
	 * us to check upper-layer checksums, because we cannot do any further
	 * processing of the packet without a valid IP checksum.
	 */

	/* Get the next level protocol identifier. */

	NextLevelProtocol = *(SK_U8 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_NEXT_LEVEL_PROTOCOL);

	if (IpHeaderChecksum != 0xFFFF) {
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].RxErrCts++;
		/* the NDIS tester wants to know the upper level protocol too */
		if (NextLevelProtocol == SKCS_PROTO_ID_TCP) {
			return(SKCS_STATUS_IP_CSUM_ERROR_TCP);
		}
		else if (NextLevelProtocol == SKCS_PROTO_ID_UDP) {
			return(SKCS_STATUS_IP_CSUM_ERROR_UDP);
		}
		return (SKCS_STATUS_IP_CSUM_ERROR);
	}

	/*
	 * Check if this is a TCP or UDP frame and if we should calculate the
	 * TCP/UDP pseudo header checksum.
	 *
	 * Also clear all protocol bit flags of protocols not present in the
	 * frame.
	 */

	if ((pAc->Csum.ReceiveFlags[NetNumber] & SKCS_PROTO_TCP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_TCP) {
		/* TCP/IP frame. */
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_TCP];
	}
	else if ((pAc->Csum.ReceiveFlags[NetNumber] & SKCS_PROTO_UDP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_UDP) {
		/* UDP/IP frame. */
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_UDP];
	}
	else {
		/*
		 * Either not a TCP or UDP frame and/or TCP/UDP processing not
		 * specified.
		 */
		return (SKCS_STATUS_IP_CSUM_OK);
	}

	/* Check if this is an IP fragment. */

	/*
	 * Note: An IP fragment has a non-zero "Fragment Offset" field and/or
	 * the "More Fragments" bit set. Thus, if both the "Fragment Offset"
	 * and the "More Fragments" are zero, it is *not* a fragment. We can
	 * easily check both at the same time since they are in the same 16-bit
	 * word.
	 */

	if ((*(SK_U16 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_FLAGS_AND_FRAGMENT_OFFSET) &
		~SKCS_IP_DONT_FRAGMENT) != 0) {
		/* IP fragment; ignore all other protocols. */
		NextLevelProtoStats->RxUnableCts++;
		return (SKCS_STATUS_IP_FRAGMENT);
	}

	/*
	 * 08-May-2000 ra
	 *
	 * From RFC 768 (UDP)
	 * If the computed checksum is zero, it is transmitted as all ones (the
	 * equivalent in one's complement arithmetic).  An all zero transmitted
	 * checksum value means that the transmitter generated no checksum (for
	 * debugging or for higher level protocols that don't care).
	 */

	if (NextLevelProtocol == SKCS_PROTO_ID_UDP &&
		*(SK_U16*)SKCS_IDX(pIpHeader, IpHeaderLength + 6) == 0x0000) {

		NextLevelProtoStats->RxOkCts++;

		return (SKCS_STATUS_IP_CSUM_OK_NO_UDP);
	}

	/*
	 * Calculate the TCP/UDP checksum.
	 */

	/* Get total length of IP header and data. */

	IpDataLength =
		*(SK_U16 *) SKCS_IDX(pIpHeader, SKCS_OFS_IP_TOTAL_LENGTH);

	/* Get length of IP data portion. */

	IpDataLength = SKCS_NTOH16(IpDataLength) - IpHeaderLength;

	NextLevelProtocolChecksum =

		/* Calculate the pseudo header checksum. */

		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 2) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 2) +
		(unsigned long) SKCS_HTON16(NextLevelProtocol) +
		(unsigned long) SKCS_HTON16(IpDataLength) +

		/* Add the TCP/UDP header checksum. */

		(unsigned long) IpDataChecksum;

	/* Add-in any carries. */

	SKCS_OC_ADD(NextLevelProtocolChecksum, NextLevelProtocolChecksum, 0);

	/* Add-in any new carry. */

	SKCS_OC_ADD(NextLevelProtocolChecksum, NextLevelProtocolChecksum, 0);

	/* Check if the TCP/UDP checksum is ok. */

	if ((unsigned) NextLevelProtocolChecksum == 0xFFFF) {

		/* TCP/UDP checksum ok. */

		NextLevelProtoStats->RxOkCts++;

		return (NextLevelProtocol == SKCS_PROTO_ID_TCP ?
			SKCS_STATUS_TCP_CSUM_OK : SKCS_STATUS_UDP_CSUM_OK);
	}

	/* TCP/UDP checksum error. */

	NextLevelProtoStats->RxErrCts++;

	return (NextLevelProtocol == SKCS_PROTO_ID_TCP ?
		SKCS_STATUS_TCP_CSUM_ERROR : SKCS_STATUS_UDP_CSUM_ERROR);
}	/* SkCsGetReceiveInfo */
#endif


/******************************************************************************
 *
 *	SkCsSetReceiveFlags - set checksum receive flags
 *
 * Description:
 *	Use this function to set the various receive flags. According to the
 *	protocol flags set by the caller, the start offsets within received
 *	packets of the two hardware checksums are returned. These offsets must
 *	be stored in all receive descriptors.
 *
 * Arguments:
 *	pAc - Pointer to adapter context struct.
 *
 *	ReceiveFlags - Any combination of SK_PROTO_XXX flags of the protocols
 *	for which the caller wants checksum information on received frames.
 *
 *	pChecksum1Offset - The start offset of the first receive descriptor
 *	hardware checksum to be calculated for received frames is returned
 *	here.
 *
 *	pChecksum2Offset - The start offset of the second receive descriptor
 *	hardware checksum to be calculated for received frames is returned
 *	here.
 *
 * Returns: N/A
 *	Returns the two hardware checksum start offsets.
 */
void SkCsSetReceiveFlags(
SK_AC		*pAc,				/* Adapter context struct. */
unsigned	ReceiveFlags,		/* New receive flags. */
unsigned	*pChecksum1Offset,	/* Offset for hardware checksum 1. */
unsigned	*pChecksum2Offset,	/* Offset for hardware checksum 2. */
int			NetNumber)
{
	/* Save the receive flags. */

	pAc->Csum.ReceiveFlags[NetNumber] = ReceiveFlags;

	/* First checksum start offset is the IP header. */
	*pChecksum1Offset = SKCS_MAC_HEADER_SIZE;

	/*
	 * Second checksum start offset is the IP data. Note that this may vary
	 * if there are any IP header options in the actual packet.
	 */
	*pChecksum2Offset = SKCS_MAC_HEADER_SIZE + SKCS_IP_HEADER_SIZE;
}	/* SkCsSetReceiveFlags */

#ifndef SkCsCalculateChecksum

/******************************************************************************
 *
 *	SkCsCalculateChecksum - calculate checksum for specified data
 *
 * Description:
 *	Calculate and return the 16-bit Internet Checksum for the specified
 *	data.
 *
 * Arguments:
 *	pData - Pointer to data for which the checksum shall be calculated.
 *	Note: The pointer should be aligned on a 16-bit boundary.
 *
 *	Length - Length in bytes of data to checksum.
 *
 * Returns:
 *	The 16-bit Internet Checksum for the specified data.
 *
 *	Note: The checksum is calculated in the machine's natural byte order,
 *	i.e. little vs. big endian. Thus, the resulting checksum is different
 *	for the same input data on little and big endian machines.
 *
 *	However, when written back to the network packet, the byte order is
 *	always in correct network order.
 */
unsigned SkCsCalculateChecksum(
void		*pData,		/* Data to checksum. */
unsigned	Length)		/* Length of data. */
{
	SK_U16 *pU16;		/* Pointer to the data as 16-bit words. */
	unsigned long Checksum;	/* Checksum; must be at least 32 bits. */

	/* Sum up all 16-bit words. */

	pU16 = (SK_U16 *) pData;
	for (Checksum = 0; Length > 1; Length -= 2) {
		Checksum += *pU16++;
	}

	/* If this is an odd number of bytes, add-in the last byte. */

	if (Length > 0) {
#ifdef SK_BIG_ENDIAN
		/* Add the last byte as the high byte. */
		Checksum += ((unsigned) *(SK_U8 *) pU16) << 8;
#else	/* !SK_BIG_ENDIAN */
		/* Add the last byte as the low byte. */
		Checksum += *(SK_U8 *) pU16;
#endif	/* !SK_BIG_ENDIAN */
	}

	/* Add-in any carries. */

	SKCS_OC_ADD(Checksum, Checksum, 0);

	/* Add-in any new carry. */

	SKCS_OC_ADD(Checksum, Checksum, 0);

	/* Note: All bits beyond the 16-bit limit are now zero. */

	return ((unsigned) Checksum);
}	/* SkCsCalculateChecksum */

#endif /* SkCsCalculateChecksum */

/******************************************************************************
 *
 *	SkCsEvent - the CSUM event dispatcher
 *
 * Description:
 *	This is the event handler for the CSUM module.
 *
 * Arguments:
 *	pAc - Pointer to adapter context.
 *
 *	Ioc - I/O context.
 *
 *	Event -	 Event id.
 *
 *	Param - Event dependent parameter.
 *
 * Returns:
 *	The 16-bit Internet Checksum for the specified data.
 *
 *	Note: The checksum is calculated in the machine's natural byte order,
 *	i.e. little vs. big endian. Thus, the resulting checksum is different
 *	for the same input data on little and big endian machines.
 *
 *	However, when written back to the network packet, the byte order is
 *	always in correct network order.
 */
int SkCsEvent(
SK_AC		*pAc,	/* Pointer to adapter context. */
SK_IOC		Ioc,	/* I/O context. */
SK_U32		Event,	/* Event id. */
SK_EVPARA	Param)	/* Event dependent parameter. */
{
	int ProtoIndex;
	int	NetNumber;

	switch (Event) {
	/*
	 * Clear protocol statistics.
	 *
	 * Param - Protocol index, or -1 for all protocols.
	 *		 - Net number.
	 */
	case SK_CSUM_EVENT_CLEAR_PROTO_STATS:

		ProtoIndex = (int)Param.Para32[1];
		NetNumber = (int)Param.Para32[0];
		if (ProtoIndex < 0) {	/* Clear for all protocols. */
			if (NetNumber >= 0) {
				memset(&pAc->Csum.ProtoStats[NetNumber][0], 0,
					sizeof(pAc->Csum.ProtoStats[NetNumber]));
			}
		}
		else {					/* Clear for individual protocol. */
			memset(&pAc->Csum.ProtoStats[NetNumber][ProtoIndex], 0,
				sizeof(pAc->Csum.ProtoStats[NetNumber][ProtoIndex]));
		}
		break;
	default:
		break;
	}
	return (0);	/* Success. */
}	/* SkCsEvent */

#endif	/* SK_USE_CSUM */

#endif /* CONFIG_SK98 */