Linux preempt-rt

Check our new training course

Real-Time Linux with PREEMPT_RT

Check our new training course
with Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

  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
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
/******************************************************************************
 * xen_netif.h
 *
 * Unified network-device I/O interface for Xen guest OSes.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Copyright (c) 2003-2004, Keir Fraser
 */

#ifndef __XEN_PUBLIC_IO_XEN_NETIF_H__
#define __XEN_PUBLIC_IO_XEN_NETIF_H__

#include "ring.h"
#include "../grant_table.h"

/*
 * Older implementation of Xen network frontend / backend has an
 * implicit dependency on the MAX_SKB_FRAGS as the maximum number of
 * ring slots a skb can use. Netfront / netback may not work as
 * expected when frontend and backend have different MAX_SKB_FRAGS.
 *
 * A better approach is to add mechanism for netfront / netback to
 * negotiate this value. However we cannot fix all possible
 * frontends, so we need to define a value which states the minimum
 * slots backend must support.
 *
 * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS
 * (18), which is proved to work with most frontends. Any new backend
 * which doesn't negotiate with frontend should expect frontend to
 * send a valid packet using slots up to this value.
 */
#define XEN_NETIF_NR_SLOTS_MIN 18

/*
 * Notifications after enqueuing any type of message should be conditional on
 * the appropriate req_event or rsp_event field in the shared ring.
 * If the client sends notification for rx requests then it should specify
 * feature 'feature-rx-notify' via xenbus. Otherwise the backend will assume
 * that it cannot safely queue packets (as it may not be kicked to send them).
 */

/*
 * "feature-split-event-channels" is introduced to separate guest TX
 * and RX notification. Backend either doesn't support this feature or
 * advertises it via xenstore as 0 (disabled) or 1 (enabled).
 *
 * To make use of this feature, frontend should allocate two event
 * channels for TX and RX, advertise them to backend as
 * "event-channel-tx" and "event-channel-rx" respectively. If frontend
 * doesn't want to use this feature, it just writes "event-channel"
 * node as before.
 */

/*
 * Multiple transmit and receive queues:
 * If supported, the backend will write the key "multi-queue-max-queues" to
 * the directory for that vif, and set its value to the maximum supported
 * number of queues.
 * Frontends that are aware of this feature and wish to use it can write the
 * key "multi-queue-num-queues", set to the number they wish to use, which
 * must be greater than zero, and no more than the value reported by the backend
 * in "multi-queue-max-queues".
 *
 * Queues replicate the shared rings and event channels.
 * "feature-split-event-channels" may optionally be used when using
 * multiple queues, but is not mandatory.
 *
 * Each queue consists of one shared ring pair, i.e. there must be the same
 * number of tx and rx rings.
 *
 * For frontends requesting just one queue, the usual event-channel and
 * ring-ref keys are written as before, simplifying the backend processing
 * to avoid distinguishing between a frontend that doesn't understand the
 * multi-queue feature, and one that does, but requested only one queue.
 *
 * Frontends requesting two or more queues must not write the toplevel
 * event-channel (or event-channel-{tx,rx}) and {tx,rx}-ring-ref keys,
 * instead writing those keys under sub-keys having the name "queue-N" where
 * N is the integer ID of the queue for which those keys belong. Queues
 * are indexed from zero. For example, a frontend with two queues and split
 * event channels must write the following set of queue-related keys:
 *
 * /local/domain/1/device/vif/0/multi-queue-num-queues = "2"
 * /local/domain/1/device/vif/0/queue-0 = ""
 * /local/domain/1/device/vif/0/queue-0/tx-ring-ref = "<ring-ref-tx0>"
 * /local/domain/1/device/vif/0/queue-0/rx-ring-ref = "<ring-ref-rx0>"
 * /local/domain/1/device/vif/0/queue-0/event-channel-tx = "<evtchn-tx0>"
 * /local/domain/1/device/vif/0/queue-0/event-channel-rx = "<evtchn-rx0>"
 * /local/domain/1/device/vif/0/queue-1 = ""
 * /local/domain/1/device/vif/0/queue-1/tx-ring-ref = "<ring-ref-tx1>"
 * /local/domain/1/device/vif/0/queue-1/rx-ring-ref = "<ring-ref-rx1"
 * /local/domain/1/device/vif/0/queue-1/event-channel-tx = "<evtchn-tx1>"
 * /local/domain/1/device/vif/0/queue-1/event-channel-rx = "<evtchn-rx1>"
 *
 * If there is any inconsistency in the XenStore data, the backend may
 * choose not to connect any queues, instead treating the request as an
 * error. This includes scenarios where more (or fewer) queues were
 * requested than the frontend provided details for.
 *
 * Mapping of packets to queues is considered to be a function of the
 * transmitting system (backend or frontend) and is not negotiated
 * between the two. Guests are free to transmit packets on any queue
 * they choose, provided it has been set up correctly. Guests must be
 * prepared to receive packets on any queue they have requested be set up.
 */

/*
 * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
 * offload off or on. If it is missing then the feature is assumed to be on.
 * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum
 * offload on or off. If it is missing then the feature is assumed to be off.
 */

/*
 * "feature-gso-tcpv4" and "feature-gso-tcpv6" advertise the capability to
 * handle large TCP packets (in IPv4 or IPv6 form respectively). Neither
 * frontends nor backends are assumed to be capable unless the flags are
 * present.
 */

/*
 * "feature-multicast-control" and "feature-dynamic-multicast-control"
 * advertise the capability to filter ethernet multicast packets in the
 * backend. If the frontend wishes to take advantage of this feature then
 * it may set "request-multicast-control". If the backend only advertises
 * "feature-multicast-control" then "request-multicast-control" must be set
 * before the frontend moves into the connected state. The backend will
 * sample the value on this state transition and any subsequent change in
 * value will have no effect. However, if the backend also advertises
 * "feature-dynamic-multicast-control" then "request-multicast-control"
 * may be set by the frontend at any time. In this case, the backend will
 * watch the value and re-sample on watch events.
 *
 * If the sampled value of "request-multicast-control" is set then the
 * backend transmit side should no longer flood multicast packets to the
 * frontend, it should instead drop any multicast packet that does not
 * match in a filter list.
 * The list is amended by the frontend by sending dummy transmit requests
 * containing XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL} extra-info fragments as
 * specified below.
 * Note that the filter list may be amended even if the sampled value of
 * "request-multicast-control" is not set, however the filter should only
 * be applied if it is set.
 */

/*
 * "xdp-headroom" is used to request that extra space is added
 * for XDP processing.  The value is measured in bytes and passed by
 * the frontend to be consistent between both ends.
 * If the value is greater than zero that means that
 * an RX response is going to be passed to an XDP program for processing.
 * XEN_NETIF_MAX_XDP_HEADROOM defines the maximum headroom offset in bytes
 *
 * "feature-xdp-headroom" is set to "1" by the netback side like other features
 * so a guest can check if an XDP program can be processed.
 */
#define XEN_NETIF_MAX_XDP_HEADROOM 0x7FFF

/*
 * Control ring
 * ============
 *
 * Some features, such as hashing (detailed below), require a
 * significant amount of out-of-band data to be passed from frontend to
 * backend. Use of xenstore is not suitable for large quantities of data
 * because of quota limitations and so a dedicated 'control ring' is used.
 * The ability of the backend to use a control ring is advertised by
 * setting:
 *
 * /local/domain/X/backend/<domid>/<vif>/feature-ctrl-ring = "1"
 *
 * The frontend provides a control ring to the backend by setting:
 *
 * /local/domain/<domid>/device/vif/<vif>/ctrl-ring-ref = <gref>
 * /local/domain/<domid>/device/vif/<vif>/event-channel-ctrl = <port>
 *
 * where <gref> is the grant reference of the shared page used to
 * implement the control ring and <port> is an event channel to be used
 * as a mailbox interrupt. These keys must be set before the frontend
 * moves into the connected state.
 *
 * The control ring uses a fixed request/response message size and is
 * balanced (i.e. one request to one response), so operationally it is much
 * the same as a transmit or receive ring.
 * Note that there is no requirement that responses are issued in the same
 * order as requests.
 */

/*
 * Hash types
 * ==========
 *
 * For the purposes of the definitions below, 'Packet[]' is an array of
 * octets containing an IP packet without options, 'Array[X..Y]' means a
 * sub-array of 'Array' containing bytes X thru Y inclusive, and '+' is
 * used to indicate concatenation of arrays.
 */

/*
 * A hash calculated over an IP version 4 header as follows:
 *
 * Buffer[0..8] = Packet[12..15] (source address) +
 *                Packet[16..19] (destination address)
 *
 * Result = Hash(Buffer, 8)
 */
#define _XEN_NETIF_CTRL_HASH_TYPE_IPV4 0
#define XEN_NETIF_CTRL_HASH_TYPE_IPV4 \
	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV4)

/*
 * A hash calculated over an IP version 4 header and TCP header as
 * follows:
 *
 * Buffer[0..12] = Packet[12..15] (source address) +
 *                 Packet[16..19] (destination address) +
 *                 Packet[20..21] (source port) +
 *                 Packet[22..23] (destination port)
 *
 * Result = Hash(Buffer, 12)
 */
#define _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP 1
#define XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP \
	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP)

/*
 * A hash calculated over an IP version 6 header as follows:
 *
 * Buffer[0..32] = Packet[8..23]  (source address ) +
 *                 Packet[24..39] (destination address)
 *
 * Result = Hash(Buffer, 32)
 */
#define _XEN_NETIF_CTRL_HASH_TYPE_IPV6 2
#define XEN_NETIF_CTRL_HASH_TYPE_IPV6 \
	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV6)

/*
 * A hash calculated over an IP version 6 header and TCP header as
 * follows:
 *
 * Buffer[0..36] = Packet[8..23]  (source address) +
 *                 Packet[24..39] (destination address) +
 *                 Packet[40..41] (source port) +
 *                 Packet[42..43] (destination port)
 *
 * Result = Hash(Buffer, 36)
 */
#define _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP 3
#define XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP \
	(1 << _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP)

/*
 * Hash algorithms
 * ===============
 */

#define XEN_NETIF_CTRL_HASH_ALGORITHM_NONE 0

/*
 * Toeplitz hash:
 */

#define XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ 1

/*
 * This algorithm uses a 'key' as well as the data buffer itself.
 * (Buffer[] and Key[] are treated as shift-registers where the MSB of
 * Buffer/Key[0] is considered 'left-most' and the LSB of Buffer/Key[N-1]
 * is the 'right-most').
 *
 * Value = 0
 * For number of bits in Buffer[]
 *    If (left-most bit of Buffer[] is 1)
 *        Value ^= left-most 32 bits of Key[]
 *    Key[] << 1
 *    Buffer[] << 1
 *
 * The code below is provided for convenience where an operating system
 * does not already provide an implementation.
 */
#ifdef XEN_NETIF_DEFINE_TOEPLITZ
static uint32_t xen_netif_toeplitz_hash(const uint8_t *key,
					unsigned int keylen,
					const uint8_t *buf, unsigned int buflen)
{
	unsigned int keyi, bufi;
	uint64_t prefix = 0;
	uint64_t hash = 0;

	/* Pre-load prefix with the first 8 bytes of the key */
	for (keyi = 0; keyi < 8; keyi++) {
		prefix <<= 8;
		prefix |= (keyi < keylen) ? key[keyi] : 0;
	}

	for (bufi = 0; bufi < buflen; bufi++) {
		uint8_t byte = buf[bufi];
		unsigned int bit;

		for (bit = 0; bit < 8; bit++) {
			if (byte & 0x80)
				hash ^= prefix;
			prefix <<= 1;
			byte <<= 1;
		}

		/*
		 * 'prefix' has now been left-shifted by 8, so
		 * OR in the next byte.
		 */
		prefix |= (keyi < keylen) ? key[keyi] : 0;
		keyi++;
	}

	/* The valid part of the hash is in the upper 32 bits. */
	return hash >> 32;
}
#endif				/* XEN_NETIF_DEFINE_TOEPLITZ */

/*
 * Control requests (struct xen_netif_ctrl_request)
 * ================================================
 *
 * All requests have the following format:
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |    id     |   type    |         data[0]       |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |         data[1]       |         data[2]       |
 * +-----+-----+-----+-----+-----------------------+
 *
 * id: the request identifier, echoed in response.
 * type: the type of request (see below)
 * data[]: any data associated with the request (determined by type)
 */

struct xen_netif_ctrl_request {
	uint16_t id;
	uint16_t type;

#define XEN_NETIF_CTRL_TYPE_INVALID               0
#define XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS        1
#define XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS        2
#define XEN_NETIF_CTRL_TYPE_SET_HASH_KEY          3
#define XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE 4
#define XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE 5
#define XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING      6
#define XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM    7

	uint32_t data[3];
};

/*
 * Control responses (struct xen_netif_ctrl_response)
 * ==================================================
 *
 * All responses have the following format:
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |    id     |   type    |         status        |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |         data          |
 * +-----+-----+-----+-----+
 *
 * id: the corresponding request identifier
 * type: the type of the corresponding request
 * status: the status of request processing
 * data: any data associated with the response (determined by type and
 *       status)
 */

struct xen_netif_ctrl_response {
	uint16_t id;
	uint16_t type;
	uint32_t status;

#define XEN_NETIF_CTRL_STATUS_SUCCESS           0
#define XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     1
#define XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER 2
#define XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   3

	uint32_t data;
};

/*
 * Control messages
 * ================
 *
 * XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM
 * --------------------------------------
 *
 * This is sent by the frontend to set the desired hash algorithm.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_ALGORITHM
 *  data[0] = a XEN_NETIF_CTRL_HASH_ALGORITHM_* value
 *  data[1] = 0
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - The algorithm is not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
 *
 * NOTE: Setting data[0] to XEN_NETIF_CTRL_HASH_ALGORITHM_NONE disables
 *       hashing and the backend is free to choose how it steers packets
 *       to queues (which is the default behaviour).
 *
 * XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS
 * ----------------------------------
 *
 * This is sent by the frontend to query the types of hash supported by
 * the backend.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_GET_HASH_FLAGS
 *  data[0] = 0
 *  data[1] = 0
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED - Operation not supported
 *           XEN_NETIF_CTRL_STATUS_SUCCESS       - Operation successful
 *  data   = supported hash types (if operation was successful)
 *
 * NOTE: A valid hash algorithm must be selected before this operation can
 *       succeed.
 *
 * XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS
 * ----------------------------------
 *
 * This is sent by the frontend to set the types of hash that the backend
 * should calculate. (See above for hash type definitions).
 * Note that the 'maximal' type of hash should always be chosen. For
 * example, if the frontend sets both IPV4 and IPV4_TCP hash types then
 * the latter hash type should be calculated for any TCP packet and the
 * former only calculated for non-TCP packets.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_FLAGS
 *  data[0] = bitwise OR of XEN_NETIF_CTRL_HASH_TYPE_* values
 *  data[1] = 0
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - One or more flag
 *                                                     value is invalid or
 *                                                     unsupported
 *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
 *  data   = 0
 *
 * NOTE: A valid hash algorithm must be selected before this operation can
 *       succeed.
 *       Also, setting data[0] to zero disables hashing and the backend
 *       is free to choose how it steers packets to queues.
 *
 * XEN_NETIF_CTRL_TYPE_SET_HASH_KEY
 * --------------------------------
 *
 * This is sent by the frontend to set the key of the hash if the algorithm
 * requires it. (See hash algorithms above).
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_KEY
 *  data[0] = grant reference of page containing the key (assumed to
 *            start at beginning of grant)
 *  data[1] = size of key in octets
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Key size is invalid
 *           XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   - Key size is larger
 *                                                     than the backend
 *                                                     supports
 *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
 *  data   = 0
 *
 * NOTE: Any key octets not specified are assumed to be zero (the key
 *       is assumed to be empty by default) and specifying a new key
 *       invalidates any previous key, hence specifying a key size of
 *       zero will clear the key (which ensures that the calculated hash
 *       will always be zero).
 *       The maximum size of key is algorithm and backend specific, but
 *       is also limited by the single grant reference.
 *       The grant reference may be read-only and must remain valid until
 *       the response has been processed.
 *
 * XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE
 * -----------------------------------------
 *
 * This is sent by the frontend to query the maximum size of mapping
 * table supported by the backend. The size is specified in terms of
 * table entries.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_GET_HASH_MAPPING_SIZE
 *  data[0] = 0
 *  data[1] = 0
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED - Operation not supported
 *           XEN_NETIF_CTRL_STATUS_SUCCESS       - Operation successful
 *  data   = maximum number of entries allowed in the mapping table
 *           (if operation was successful) or zero if a mapping table is
 *           not supported (i.e. hash mapping is done only by modular
 *           arithmetic).
 *
 * XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
 * -------------------------------------
 *
 * This is sent by the frontend to set the actual size of the mapping
 * table to be used by the backend. The size is specified in terms of
 * table entries.
 * Any previous table is invalidated by this message and any new table
 * is assumed to be zero filled.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
 *  data[0] = number of entries in mapping table
 *  data[1] = 0
 *  data[2] = 0
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Table size is invalid
 *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
 *  data   = 0
 *
 * NOTE: Setting data[0] to 0 means that hash mapping should be done
 *       using modular arithmetic.
 *
 * XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING
 * ------------------------------------
 *
 * This is sent by the frontend to set the content of the table mapping
 * hash value to queue number. The backend should calculate the hash from
 * the packet header, use it as an index into the table (modulo the size
 * of the table) and then steer the packet to the queue number found at
 * that index.
 *
 * Request:
 *
 *  type    = XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING
 *  data[0] = grant reference of page containing the mapping (sub-)table
 *            (assumed to start at beginning of grant)
 *  data[1] = size of (sub-)table in entries
 *  data[2] = offset, in entries, of sub-table within overall table
 *
 * Response:
 *
 *  status = XEN_NETIF_CTRL_STATUS_NOT_SUPPORTED     - Operation not
 *                                                     supported
 *           XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER - Table size or content
 *                                                     is invalid
 *           XEN_NETIF_CTRL_STATUS_BUFFER_OVERFLOW   - Table size is larger
 *                                                     than the backend
 *                                                     supports
 *           XEN_NETIF_CTRL_STATUS_SUCCESS           - Operation successful
 *  data   = 0
 *
 * NOTE: The overall table has the following format:
 *
 *          0     1     2     3     4     5     6     7  octet
 *       +-----+-----+-----+-----+-----+-----+-----+-----+
 *       |       mapping[0]      |       mapping[1]      |
 *       +-----+-----+-----+-----+-----+-----+-----+-----+
 *       |                       .                       |
 *       |                       .                       |
 *       |                       .                       |
 *       +-----+-----+-----+-----+-----+-----+-----+-----+
 *       |      mapping[N-2]     |      mapping[N-1]     |
 *       +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 *       where N is specified by a XEN_NETIF_CTRL_TYPE_SET_HASH_MAPPING_SIZE
 *       message and each  mapping must specifies a queue between 0 and
 *       "multi-queue-num-queues" (see above).
 *       The backend may support a mapping table larger than can be
 *       mapped by a single grant reference. Thus sub-tables within a
 *       larger table can be individually set by sending multiple messages
 *       with differing offset values. Specifying a new sub-table does not
 *       invalidate any table data outside that range.
 *       The grant reference may be read-only and must remain valid until
 *       the response has been processed.
 */

DEFINE_RING_TYPES(xen_netif_ctrl,
		  struct xen_netif_ctrl_request,
		  struct xen_netif_ctrl_response);

/*
 * Guest transmit
 * ==============
 *
 * This is the 'wire' format for transmit (frontend -> backend) packets:
 *
 *  Fragment 1: xen_netif_tx_request_t  - flags = XEN_NETTXF_*
 *                                    size = total packet size
 * [Extra 1: xen_netif_extra_info_t]    - (only if fragment 1 flags include
 *                                     XEN_NETTXF_extra_info)
 *  ...
 * [Extra N: xen_netif_extra_info_t]    - (only if extra N-1 flags include
 *                                     XEN_NETIF_EXTRA_MORE)
 *  ...
 *  Fragment N: xen_netif_tx_request_t  - (only if fragment N-1 flags include
 *                                     XEN_NETTXF_more_data - flags on preceding
 *                                     extras are not relevant here)
 *                                    flags = 0
 *                                    size = fragment size
 *
 * NOTE:
 *
 * This format slightly is different from that used for receive
 * (backend -> frontend) packets. Specifically, in a multi-fragment
 * packet the actual size of fragment 1 can only be determined by
 * subtracting the sizes of fragments 2..N from the total packet size.
 *
 * Ring slot size is 12 octets, however not all request/response
 * structs use the full size.
 *
 * tx request data (xen_netif_tx_request_t)
 * ------------------------------------
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | grant ref             | offset    | flags     |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | id        | size      |
 * +-----+-----+-----+-----+
 *
 * grant ref: Reference to buffer page.
 * offset: Offset within buffer page.
 * flags: XEN_NETTXF_*.
 * id: request identifier, echoed in response.
 * size: packet size in bytes.
 *
 * tx response (xen_netif_tx_response_t)
 * ---------------------------------
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | id        | status    | unused                |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | unused                |
 * +-----+-----+-----+-----+
 *
 * id: reflects id in transmit request
 * status: XEN_NETIF_RSP_*
 *
 * Guest receive
 * =============
 *
 * This is the 'wire' format for receive (backend -> frontend) packets:
 *
 *  Fragment 1: xen_netif_rx_request_t  - flags = XEN_NETRXF_*
 *                                    size = fragment size
 * [Extra 1: xen_netif_extra_info_t]    - (only if fragment 1 flags include
 *                                     XEN_NETRXF_extra_info)
 *  ...
 * [Extra N: xen_netif_extra_info_t]    - (only if extra N-1 flags include
 *                                     XEN_NETIF_EXTRA_MORE)
 *  ...
 *  Fragment N: xen_netif_rx_request_t  - (only if fragment N-1 flags include
 *                                     XEN_NETRXF_more_data - flags on preceding
 *                                     extras are not relevant here)
 *                                    flags = 0
 *                                    size = fragment size
 *
 * NOTE:
 *
 * This format slightly is different from that used for transmit
 * (frontend -> backend) packets. Specifically, in a multi-fragment
 * packet the size of the packet can only be determined by summing the
 * sizes of fragments 1..N.
 *
 * Ring slot size is 8 octets.
 *
 * rx request (xen_netif_rx_request_t)
 * -------------------------------
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | id        | pad       | gref                  |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 * id: request identifier, echoed in response.
 * gref: reference to incoming granted frame.
 *
 * rx response (xen_netif_rx_response_t)
 * ---------------------------------
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | id        | offset    | flags     | status    |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 * id: reflects id in receive request
 * offset: offset in page of start of received packet
 * flags: XEN_NETRXF_*
 * status: -ve: XEN_NETIF_RSP_*; +ve: Rx'ed pkt size.
 *
 * NOTE: Historically, to support GSO on the frontend receive side, Linux
 *       netfront does not make use of the rx response id (because, as
 *       described below, extra info structures overlay the id field).
 *       Instead it assumes that responses always appear in the same ring
 *       slot as their corresponding request. Thus, to maintain
 *       compatibility, backends must make sure this is the case.
 *
 * Extra Info
 * ==========
 *
 * Can be present if initial request or response has NET{T,R}XF_extra_info,
 * or previous extra request has XEN_NETIF_EXTRA_MORE.
 *
 * The struct therefore needs to fit into either a tx or rx slot and
 * is therefore limited to 8 octets.
 *
 * NOTE: Because extra info data overlays the usual request/response
 *       structures, there is no id information in the opposite direction.
 *       So, if an extra info overlays an rx response the frontend can
 *       assume that it is in the same ring slot as the request that was
 *       consumed to make the slot available, and the backend must ensure
 *       this assumption is true.
 *
 * extra info (xen_netif_extra_info_t)
 * -------------------------------
 *
 * General format:
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |type |flags| type specific data                |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * | padding for tx        |
 * +-----+-----+-----+-----+
 *
 * type: XEN_NETIF_EXTRA_TYPE_*
 * flags: XEN_NETIF_EXTRA_FLAG_*
 * padding for tx: present only in the tx case due to 8 octet limit
 *                 from rx case. Not shown in type specific entries
 *                 below.
 *
 * XEN_NETIF_EXTRA_TYPE_GSO:
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |type |flags| size      |type | pad | features  |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 * type: Must be XEN_NETIF_EXTRA_TYPE_GSO
 * flags: XEN_NETIF_EXTRA_FLAG_*
 * size: Maximum payload size of each segment. For example,
 *       for TCP this is just the path MSS.
 * type: XEN_NETIF_GSO_TYPE_*: This determines the protocol of
 *       the packet and any extra features required to segment the
 *       packet properly.
 * features: EN_XEN_NETIF_GSO_FEAT_*: This specifies any extra GSO
 *           features required to process this packet, such as ECN
 *           support for TCPv4.
 *
 * XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL}:
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |type |flags| addr                              |
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 * type: Must be XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL}
 * flags: XEN_NETIF_EXTRA_FLAG_*
 * addr: address to add/remove
 *
 * XEN_NETIF_EXTRA_TYPE_HASH:
 *
 * A backend that supports teoplitz hashing is assumed to accept
 * this type of extra info in transmit packets.
 * A frontend that enables hashing is assumed to accept
 * this type of extra info in receive packets.
 *
 *    0     1     2     3     4     5     6     7  octet
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 * |type |flags|htype| alg |LSB ---- value ---- MSB|
 * +-----+-----+-----+-----+-----+-----+-----+-----+
 *
 * type: Must be XEN_NETIF_EXTRA_TYPE_HASH
 * flags: XEN_NETIF_EXTRA_FLAG_*
 * htype: Hash type (one of _XEN_NETIF_CTRL_HASH_TYPE_* - see above)
 * alg: The algorithm used to calculate the hash (one of
 *      XEN_NETIF_CTRL_HASH_TYPE_ALGORITHM_* - see above)
 * value: Hash value
 */

/* Protocol checksum field is blank in the packet (hardware offload)? */
#define _XEN_NETTXF_csum_blank     (0)
#define  XEN_NETTXF_csum_blank     (1U<<_XEN_NETTXF_csum_blank)

/* Packet data has been validated against protocol checksum. */
#define _XEN_NETTXF_data_validated (1)
#define  XEN_NETTXF_data_validated (1U<<_XEN_NETTXF_data_validated)

/* Packet continues in the next request descriptor. */
#define _XEN_NETTXF_more_data      (2)
#define  XEN_NETTXF_more_data      (1U<<_XEN_NETTXF_more_data)

/* Packet to be followed by extra descriptor(s). */
#define _XEN_NETTXF_extra_info     (3)
#define  XEN_NETTXF_extra_info     (1U<<_XEN_NETTXF_extra_info)

#define XEN_NETIF_MAX_TX_SIZE 0xFFFF
struct xen_netif_tx_request {
	grant_ref_t gref;
	uint16_t offset;
	uint16_t flags;
	uint16_t id;
	uint16_t size;
};

/* Types of xen_netif_extra_info descriptors. */
#define XEN_NETIF_EXTRA_TYPE_NONE      (0)	/* Never used - invalid */
#define XEN_NETIF_EXTRA_TYPE_GSO       (1)	/* u.gso */
#define XEN_NETIF_EXTRA_TYPE_MCAST_ADD (2)	/* u.mcast */
#define XEN_NETIF_EXTRA_TYPE_MCAST_DEL (3)	/* u.mcast */
#define XEN_NETIF_EXTRA_TYPE_HASH      (4)	/* u.hash */
#define XEN_NETIF_EXTRA_TYPE_XDP       (5)	/* u.xdp */
#define XEN_NETIF_EXTRA_TYPE_MAX       (6)

/* xen_netif_extra_info_t flags. */
#define _XEN_NETIF_EXTRA_FLAG_MORE (0)
#define XEN_NETIF_EXTRA_FLAG_MORE  (1U<<_XEN_NETIF_EXTRA_FLAG_MORE)

/* GSO types */
#define XEN_NETIF_GSO_TYPE_NONE         (0)
#define XEN_NETIF_GSO_TYPE_TCPV4        (1)
#define XEN_NETIF_GSO_TYPE_TCPV6        (2)

/*
 * This structure needs to fit within both xen_netif_tx_request_t and
 * xen_netif_rx_response_t for compatibility.
 */
struct xen_netif_extra_info {
	uint8_t type;
	uint8_t flags;
	union {
		struct {
			uint16_t size;
			uint8_t type;
			uint8_t pad;
			uint16_t features;
		} gso;
		struct {
			uint8_t addr[6];
		} mcast;
		struct {
			uint8_t type;
			uint8_t algorithm;
			uint8_t value[4];
		} hash;
		struct {
			uint16_t headroom;
			uint16_t pad[2];
		} xdp;
		uint16_t pad[3];
	} u;
};

struct xen_netif_tx_response {
	uint16_t id;
	int16_t status;
};

struct xen_netif_rx_request {
	uint16_t id;		/* Echoed in response message.        */
	uint16_t pad;
	grant_ref_t gref;
};

/* Packet data has been validated against protocol checksum. */
#define _XEN_NETRXF_data_validated (0)
#define  XEN_NETRXF_data_validated (1U<<_XEN_NETRXF_data_validated)

/* Protocol checksum field is blank in the packet (hardware offload)? */
#define _XEN_NETRXF_csum_blank     (1)
#define  XEN_NETRXF_csum_blank     (1U<<_XEN_NETRXF_csum_blank)

/* Packet continues in the next request descriptor. */
#define _XEN_NETRXF_more_data      (2)
#define  XEN_NETRXF_more_data      (1U<<_XEN_NETRXF_more_data)

/* Packet to be followed by extra descriptor(s). */
#define _XEN_NETRXF_extra_info     (3)
#define  XEN_NETRXF_extra_info     (1U<<_XEN_NETRXF_extra_info)

/* Packet has GSO prefix. Deprecated but included for compatibility */
#define _XEN_NETRXF_gso_prefix     (4)
#define  XEN_NETRXF_gso_prefix     (1U<<_XEN_NETRXF_gso_prefix)

struct xen_netif_rx_response {
	uint16_t id;
	uint16_t offset;
	uint16_t flags;
	int16_t status;
};

/*
 * Generate xen_netif ring structures and types.
 */

DEFINE_RING_TYPES(xen_netif_tx, struct xen_netif_tx_request,
		  struct xen_netif_tx_response);
DEFINE_RING_TYPES(xen_netif_rx, struct xen_netif_rx_request,
		  struct xen_netif_rx_response);

#define XEN_NETIF_RSP_DROPPED         -2
#define XEN_NETIF_RSP_ERROR           -1
#define XEN_NETIF_RSP_OKAY             0
/* No response: used for auxiliary requests (e.g., xen_netif_extra_info_t). */
#define XEN_NETIF_RSP_NULL             1

#endif