Free Electrons

Embedded Linux Experts

   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
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
/*
 * llc_conn.c - Driver routines for connection component.
 *
 * Copyright (c) 1997 by Procom Technology, Inc.
 *		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *
 * This program can be redistributed or modified under the terms of the
 * GNU General Public License as published by the Free Software Foundation.
 * This program is distributed without any warranty or implied warranty
 * of merchantability or fitness for a particular purpose.
 *
 * See the GNU General Public License for more details.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <net/llc_sap.h>
#include <net/llc_conn.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/llc_c_ev.h>
#include <net/llc_c_ac.h>
#include <net/llc_c_st.h>
#include <net/llc_pdu.h>

#if 0
#define dprintk(args...) printk(KERN_DEBUG args)
#else
#define dprintk(args...)
#endif

static int llc_find_offset(int state, int ev_type);
static void llc_conn_send_pdus(struct sock *sk);
static int llc_conn_service(struct sock *sk, struct sk_buff *skb);
static int llc_exec_conn_trans_actions(struct sock *sk,
				       struct llc_conn_state_trans *trans,
				       struct sk_buff *ev);
static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
							struct sk_buff *skb);

/* Offset table on connection states transition diagram */
static int llc_offset_table[NBR_CONN_STATES][NBR_CONN_EV];

int sysctl_llc2_ack_timeout = LLC2_ACK_TIME * HZ;
int sysctl_llc2_p_timeout = LLC2_P_TIME * HZ;
int sysctl_llc2_rej_timeout = LLC2_REJ_TIME * HZ;
int sysctl_llc2_busy_timeout = LLC2_BUSY_TIME * HZ;

/**
 *	llc_conn_state_process - sends event to connection state machine
 *	@sk: connection
 *	@skb: occurred event
 *
 *	Sends an event to connection state machine. After processing event
 *	(executing it's actions and changing state), upper layer will be
 *	indicated or confirmed, if needed. Returns 0 for success, 1 for
 *	failure. The socket lock has to be held before calling this function.
 */
int llc_conn_state_process(struct sock *sk, struct sk_buff *skb)
{
	int rc;
	struct llc_sock *llc = llc_sk(skb->sk);
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

	/*
	 * We have to hold the skb, because llc_conn_service will kfree it in
	 * the sending path and we need to look at the skb->cb, where we encode
	 * llc_conn_state_ev.
	 */
	skb_get(skb);
	ev->ind_prim = ev->cfm_prim = 0;
	/*
	 * Send event to state machine
	 */
	rc = llc_conn_service(skb->sk, skb);
	if (unlikely(rc != 0)) {
		printk(KERN_ERR "%s: llc_conn_service failed\n", __func__);
		goto out_kfree_skb;
	}

	if (unlikely(!ev->ind_prim && !ev->cfm_prim)) {
		/* indicate or confirm not required */
		if (!skb->next)
			goto out_kfree_skb;
		goto out_skb_put;
	}

	if (unlikely(ev->ind_prim && ev->cfm_prim)) /* Paranoia */
		skb_get(skb);

	switch (ev->ind_prim) {
	case LLC_DATA_PRIM:
		llc_save_primitive(sk, skb, LLC_DATA_PRIM);
		if (unlikely(sock_queue_rcv_skb(sk, skb))) {
			/*
			 * shouldn't happen
			 */
			printk(KERN_ERR "%s: sock_queue_rcv_skb failed!\n",
			       __func__);
			kfree_skb(skb);
		}
		break;
	case LLC_CONN_PRIM:
		/*
		 * Can't be sock_queue_rcv_skb, because we have to leave the
		 * skb->sk pointing to the newly created struct sock in
		 * llc_conn_handler. -acme
		 */
		skb_queue_tail(&sk->sk_receive_queue, skb);
		sk->sk_state_change(sk);
		break;
	case LLC_DISC_PRIM:
		sock_hold(sk);
		if (sk->sk_type == SOCK_STREAM &&
		    sk->sk_state == TCP_ESTABLISHED) {
			sk->sk_shutdown       = SHUTDOWN_MASK;
			sk->sk_socket->state  = SS_UNCONNECTED;
			sk->sk_state          = TCP_CLOSE;
			if (!sock_flag(sk, SOCK_DEAD)) {
				sock_set_flag(sk, SOCK_DEAD);
				sk->sk_state_change(sk);
			}
		}
		kfree_skb(skb);
		sock_put(sk);
		break;
	case LLC_RESET_PRIM:
		/*
		 * FIXME:
		 * RESET is not being notified to upper layers for now
		 */
		printk(KERN_INFO "%s: received a reset ind!\n", __func__);
		kfree_skb(skb);
		break;
	default:
		if (ev->ind_prim) {
			printk(KERN_INFO "%s: received unknown %d prim!\n",
				__func__, ev->ind_prim);
			kfree_skb(skb);
		}
		/* No indication */
		break;
	}

	switch (ev->cfm_prim) {
	case LLC_DATA_PRIM:
		if (!llc_data_accept_state(llc->state))
			sk->sk_write_space(sk);
		else
			rc = llc->failed_data_req = 1;
		break;
	case LLC_CONN_PRIM:
		if (sk->sk_type == SOCK_STREAM &&
		    sk->sk_state == TCP_SYN_SENT) {
			if (ev->status) {
				sk->sk_socket->state = SS_UNCONNECTED;
				sk->sk_state         = TCP_CLOSE;
			} else {
				sk->sk_socket->state = SS_CONNECTED;
				sk->sk_state         = TCP_ESTABLISHED;
			}
			sk->sk_state_change(sk);
		}
		break;
	case LLC_DISC_PRIM:
		sock_hold(sk);
		if (sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_CLOSING) {
			sk->sk_socket->state = SS_UNCONNECTED;
			sk->sk_state         = TCP_CLOSE;
			sk->sk_state_change(sk);
		}
		sock_put(sk);
		break;
	case LLC_RESET_PRIM:
		/*
		 * FIXME:
		 * RESET is not being notified to upper layers for now
		 */
		printk(KERN_INFO "%s: received a reset conf!\n", __func__);
		break;
	default:
		if (ev->cfm_prim) {
			printk(KERN_INFO "%s: received unknown %d prim!\n",
					__func__, ev->cfm_prim);
			break;
		}
		goto out_skb_put; /* No confirmation */
	}
out_kfree_skb:
	kfree_skb(skb);
out_skb_put:
	kfree_skb(skb);
	return rc;
}

void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)
{
	/* queue PDU to send to MAC layer */
	skb_queue_tail(&sk->sk_write_queue, skb);
	llc_conn_send_pdus(sk);
}

/**
 *	llc_conn_rtn_pdu - sends received data pdu to upper layer
 *	@sk: Active connection
 *	@skb: Received data frame
 *
 *	Sends received data pdu to upper layer (by using indicate function).
 *	Prepares service parameters (prim and prim_data). calling indication
 *	function will be done in llc_conn_state_process.
 */
void llc_conn_rtn_pdu(struct sock *sk, struct sk_buff *skb)
{
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

	ev->ind_prim = LLC_DATA_PRIM;
}

/**
 *	llc_conn_resend_i_pdu_as_cmd - resend all all unacknowledged I PDUs
 *	@sk: active connection
 *	@nr: NR
 *	@first_p_bit: p_bit value of first pdu
 *
 *	Resend all unacknowledged I PDUs, starting with the NR; send first as
 *	command PDU with P bit equal first_p_bit; if more than one send
 *	subsequent as command PDUs with P bit equal zero (0).
 */
void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit)
{
	struct sk_buff *skb;
	struct llc_pdu_sn *pdu;
	u16 nbr_unack_pdus;
	struct llc_sock *llc;
	u8 howmany_resend = 0;

	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
	if (!nbr_unack_pdus)
		goto out;
	/*
	 * Process unack PDUs only if unack queue is not empty; remove
	 * appropriate PDUs, fix them up, and put them on mac_pdu_q.
	 */
	llc = llc_sk(sk);

	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
		pdu = llc_pdu_sn_hdr(skb);
		llc_pdu_set_cmd_rsp(skb, LLC_PDU_CMD);
		llc_pdu_set_pf_bit(skb, first_p_bit);
		skb_queue_tail(&sk->sk_write_queue, skb);
		first_p_bit = 0;
		llc->vS = LLC_I_GET_NS(pdu);
		howmany_resend++;
	}
	if (howmany_resend > 0)
		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
	/* any PDUs to re-send are queued up; start sending to MAC */
	llc_conn_send_pdus(sk);
out:;
}

/**
 *	llc_conn_resend_i_pdu_as_rsp - Resend all unacknowledged I PDUs
 *	@sk: active connection.
 *	@nr: NR
 *	@first_f_bit: f_bit value of first pdu.
 *
 *	Resend all unacknowledged I PDUs, starting with the NR; send first as
 *	response PDU with F bit equal first_f_bit; if more than one send
 *	subsequent as response PDUs with F bit equal zero (0).
 */
void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit)
{
	struct sk_buff *skb;
	u16 nbr_unack_pdus;
	struct llc_sock *llc = llc_sk(sk);
	u8 howmany_resend = 0;

	llc_conn_remove_acked_pdus(sk, nr, &nbr_unack_pdus);
	if (!nbr_unack_pdus)
		goto out;
	/*
	 * Process unack PDUs only if unack queue is not empty; remove
	 * appropriate PDUs, fix them up, and put them on mac_pdu_q
	 */
	while ((skb = skb_dequeue(&llc->pdu_unack_q)) != NULL) {
		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);

		llc_pdu_set_cmd_rsp(skb, LLC_PDU_RSP);
		llc_pdu_set_pf_bit(skb, first_f_bit);
		skb_queue_tail(&sk->sk_write_queue, skb);
		first_f_bit = 0;
		llc->vS = LLC_I_GET_NS(pdu);
		howmany_resend++;
	}
	if (howmany_resend > 0)
		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;
	/* any PDUs to re-send are queued up; start sending to MAC */
	llc_conn_send_pdus(sk);
out:;
}

/**
 *	llc_conn_remove_acked_pdus - Removes acknowledged pdus from tx queue
 *	@sk: active connection
 *	nr: NR
 *	how_many_unacked: size of pdu_unack_q after removing acked pdus
 *
 *	Removes acknowledged pdus from transmit queue (pdu_unack_q). Returns
 *	the number of pdus that removed from queue.
 */
int llc_conn_remove_acked_pdus(struct sock *sk, u8 nr, u16 *how_many_unacked)
{
	int pdu_pos, i;
	struct sk_buff *skb;
	struct llc_pdu_sn *pdu;
	int nbr_acked = 0;
	struct llc_sock *llc = llc_sk(sk);
	int q_len = skb_queue_len(&llc->pdu_unack_q);

	if (!q_len)
		goto out;
	skb = skb_peek(&llc->pdu_unack_q);
	pdu = llc_pdu_sn_hdr(skb);

	/* finding position of last acked pdu in queue */
	pdu_pos = ((int)LLC_2_SEQ_NBR_MODULO + (int)nr -
			(int)LLC_I_GET_NS(pdu)) % LLC_2_SEQ_NBR_MODULO;

	for (i = 0; i < pdu_pos && i < q_len; i++) {
		skb = skb_dequeue(&llc->pdu_unack_q);
		kfree_skb(skb);
		nbr_acked++;
	}
out:
	*how_many_unacked = skb_queue_len(&llc->pdu_unack_q);
	return nbr_acked;
}

/**
 *	llc_conn_send_pdus - Sends queued PDUs
 *	@sk: active connection
 *
 *	Sends queued pdus to MAC layer for transmission.
 */
static void llc_conn_send_pdus(struct sock *sk)
{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&sk->sk_write_queue)) != NULL) {
		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);

		if (LLC_PDU_TYPE_IS_I(pdu) &&
		    !(skb->dev->flags & IFF_LOOPBACK)) {
			struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);

			skb_queue_tail(&llc_sk(sk)->pdu_unack_q, skb);
			if (!skb2)
				break;
			skb = skb2;
		}
		dev_queue_xmit(skb);
	}
}

/**
 *	llc_conn_service - finds transition and changes state of connection
 *	@sk: connection
 *	@skb: happened event
 *
 *	This function finds transition that matches with happened event, then
 *	executes related actions and finally changes state of connection.
 *	Returns 0 for success, 1 for failure.
 */
static int llc_conn_service(struct sock *sk, struct sk_buff *skb)
{
	int rc = 1;
	struct llc_sock *llc = llc_sk(sk);
	struct llc_conn_state_trans *trans;

	if (llc->state > NBR_CONN_STATES)
		goto out;
	rc = 0;
	trans = llc_qualify_conn_ev(sk, skb);
	if (trans) {
		rc = llc_exec_conn_trans_actions(sk, trans, skb);
		if (!rc && trans->next_state != NO_STATE_CHANGE) {
			llc->state = trans->next_state;
			if (!llc_data_accept_state(llc->state))
				sk->sk_state_change(sk);
		}
	}
out:
	return rc;
}

/**
 *	llc_qualify_conn_ev - finds transition for event
 *	@sk: connection
 *	@skb: happened event
 *
 *	This function finds transition that matches with happened event.
 *	Returns pointer to found transition on success, %NULL otherwise.
 */
static struct llc_conn_state_trans *llc_qualify_conn_ev(struct sock *sk,
							struct sk_buff *skb)
{
	struct llc_conn_state_trans **next_trans;
	llc_conn_ev_qfyr_t *next_qualifier;
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);
	struct llc_sock *llc = llc_sk(sk);
	struct llc_conn_state *curr_state =
					&llc_conn_state_table[llc->state - 1];

	/* search thru events for this state until
	 * list exhausted or until no more
	 */
	for (next_trans = curr_state->transitions +
		llc_find_offset(llc->state - 1, ev->type);
	     (*next_trans)->ev; next_trans++) {
		if (!((*next_trans)->ev)(sk, skb)) {
			/* got POSSIBLE event match; the event may require
			 * qualification based on the values of a number of
			 * state flags; if all qualifications are met (i.e.,
			 * if all qualifying functions return success, or 0,
			 * then this is THE event we're looking for
			 */
			for (next_qualifier = (*next_trans)->ev_qualifiers;
			     next_qualifier && *next_qualifier &&
			     !(*next_qualifier)(sk, skb); next_qualifier++)
				/* nothing */;
			if (!next_qualifier || !*next_qualifier)
				/* all qualifiers executed successfully; this is
				 * our transition; return it so we can perform
				 * the associated actions & change the state
				 */
				return *next_trans;
		}
	}
	return NULL;
}

/**
 *	llc_exec_conn_trans_actions - executes related actions
 *	@sk: connection
 *	@trans: transition that it's actions must be performed
 *	@skb: event
 *
 *	Executes actions that is related to happened event. Returns 0 for
 *	success, 1 to indicate failure of at least one action.
 */
static int llc_exec_conn_trans_actions(struct sock *sk,
				       struct llc_conn_state_trans *trans,
				       struct sk_buff *skb)
{
	int rc = 0;
	llc_conn_action_t *next_action;

	for (next_action = trans->ev_actions;
	     next_action && *next_action; next_action++) {
		int rc2 = (*next_action)(sk, skb);

		if (rc2 == 2) {
			rc = rc2;
			break;
		} else if (rc2)
			rc = 1;
	}
	return rc;
}

static inline bool llc_estab_match(const struct llc_sap *sap,
				   const struct llc_addr *daddr,
				   const struct llc_addr *laddr,
				   const struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);

	return llc->laddr.lsap == laddr->lsap &&
		llc->daddr.lsap == daddr->lsap &&
		llc_mac_match(llc->laddr.mac, laddr->mac) &&
		llc_mac_match(llc->daddr.mac, daddr->mac);
}

/**
 *	__llc_lookup_established - Finds connection for the remote/local sap/mac
 *	@sap: SAP
 *	@daddr: address of remote LLC (MAC + SAP)
 *	@laddr: address of local LLC (MAC + SAP)
 *
 *	Search connection list of the SAP and finds connection using the remote
 *	mac, remote sap, local mac, and local sap. Returns pointer for
 *	connection found, %NULL otherwise.
 *	Caller has to make sure local_bh is disabled.
 */
static struct sock *__llc_lookup_established(struct llc_sap *sap,
					     struct llc_addr *daddr,
					     struct llc_addr *laddr)
{
	struct sock *rc;
	struct hlist_nulls_node *node;
	int slot = llc_sk_laddr_hashfn(sap, laddr);
	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];

	rcu_read_lock();
again:
	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
		if (llc_estab_match(sap, daddr, laddr, rc)) {
			/* Extra checks required by SLAB_DESTROY_BY_RCU */
			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
				goto again;
			if (unlikely(llc_sk(rc)->sap != sap ||
				     !llc_estab_match(sap, daddr, laddr, rc))) {
				sock_put(rc);
				continue;
			}
			goto found;
		}
	}
	rc = NULL;
	/*
	 * if the nulls value we got at the end of this lookup is
	 * not the expected one, we must restart lookup.
	 * We probably met an item that was moved to another chain.
	 */
	if (unlikely(get_nulls_value(node) != slot))
		goto again;
found:
	rcu_read_unlock();
	return rc;
}

struct sock *llc_lookup_established(struct llc_sap *sap,
				    struct llc_addr *daddr,
				    struct llc_addr *laddr)
{
	struct sock *sk;

	local_bh_disable();
	sk = __llc_lookup_established(sap, daddr, laddr);
	local_bh_enable();
	return sk;
}

static inline bool llc_listener_match(const struct llc_sap *sap,
				      const struct llc_addr *laddr,
				      const struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);

	return sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_LISTEN &&
		llc->laddr.lsap == laddr->lsap &&
		llc_mac_match(llc->laddr.mac, laddr->mac);
}

static struct sock *__llc_lookup_listener(struct llc_sap *sap,
					  struct llc_addr *laddr)
{
	struct sock *rc;
	struct hlist_nulls_node *node;
	int slot = llc_sk_laddr_hashfn(sap, laddr);
	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];

	rcu_read_lock();
again:
	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
		if (llc_listener_match(sap, laddr, rc)) {
			/* Extra checks required by SLAB_DESTROY_BY_RCU */
			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
				goto again;
			if (unlikely(llc_sk(rc)->sap != sap ||
				     !llc_listener_match(sap, laddr, rc))) {
				sock_put(rc);
				continue;
			}
			goto found;
		}
	}
	rc = NULL;
	/*
	 * if the nulls value we got at the end of this lookup is
	 * not the expected one, we must restart lookup.
	 * We probably met an item that was moved to another chain.
	 */
	if (unlikely(get_nulls_value(node) != slot))
		goto again;
found:
	rcu_read_unlock();
	return rc;
}

/**
 *	llc_lookup_listener - Finds listener for local MAC + SAP
 *	@sap: SAP
 *	@laddr: address of local LLC (MAC + SAP)
 *
 *	Search connection list of the SAP and finds connection listening on
 *	local mac, and local sap. Returns pointer for parent socket found,
 *	%NULL otherwise.
 *	Caller has to make sure local_bh is disabled.
 */
static struct sock *llc_lookup_listener(struct llc_sap *sap,
					struct llc_addr *laddr)
{
	static struct llc_addr null_addr;
	struct sock *rc = __llc_lookup_listener(sap, laddr);

	if (!rc)
		rc = __llc_lookup_listener(sap, &null_addr);

	return rc;
}

static struct sock *__llc_lookup(struct llc_sap *sap,
				 struct llc_addr *daddr,
				 struct llc_addr *laddr)
{
	struct sock *sk = __llc_lookup_established(sap, daddr, laddr);

	return sk ? : llc_lookup_listener(sap, laddr);
}

/**
 *	llc_data_accept_state - designates if in this state data can be sent.
 *	@state: state of connection.
 *
 *	Returns 0 if data can be sent, 1 otherwise.
 */
u8 llc_data_accept_state(u8 state)
{
	return state != LLC_CONN_STATE_NORMAL && state != LLC_CONN_STATE_BUSY &&
	       state != LLC_CONN_STATE_REJ;
}

/**
 *	llc_find_next_offset - finds offset for next category of transitions
 *	@state: state table.
 *	@offset: start offset.
 *
 *	Finds offset of next category of transitions in transition table.
 *	Returns the start index of next category.
 */
static u16 __init llc_find_next_offset(struct llc_conn_state *state, u16 offset)
{
	u16 cnt = 0;
	struct llc_conn_state_trans **next_trans;

	for (next_trans = state->transitions + offset;
	     (*next_trans)->ev; next_trans++)
		++cnt;
	return cnt;
}

/**
 *	llc_build_offset_table - builds offset table of connection
 *
 *	Fills offset table of connection state transition table
 *	(llc_offset_table).
 */
void __init llc_build_offset_table(void)
{
	struct llc_conn_state *curr_state;
	int state, ev_type, next_offset;

	for (state = 0; state < NBR_CONN_STATES; state++) {
		curr_state = &llc_conn_state_table[state];
		next_offset = 0;
		for (ev_type = 0; ev_type < NBR_CONN_EV; ev_type++) {
			llc_offset_table[state][ev_type] = next_offset;
			next_offset += llc_find_next_offset(curr_state,
							    next_offset) + 1;
		}
	}
}

/**
 *	llc_find_offset - finds start offset of category of transitions
 *	@state: state of connection
 *	@ev_type: type of happened event
 *
 *	Finds start offset of desired category of transitions. Returns the
 *	desired start offset.
 */
static int llc_find_offset(int state, int ev_type)
{
	int rc = 0;
	/* at this stage, llc_offset_table[..][2] is not important. it is for
	 * init_pf_cycle and I don't know what is it.
	 */
	switch (ev_type) {
	case LLC_CONN_EV_TYPE_PRIM:
		rc = llc_offset_table[state][0]; break;
	case LLC_CONN_EV_TYPE_PDU:
		rc = llc_offset_table[state][4]; break;
	case LLC_CONN_EV_TYPE_SIMPLE:
		rc = llc_offset_table[state][1]; break;
	case LLC_CONN_EV_TYPE_P_TMR:
	case LLC_CONN_EV_TYPE_ACK_TMR:
	case LLC_CONN_EV_TYPE_REJ_TMR:
	case LLC_CONN_EV_TYPE_BUSY_TMR:
		rc = llc_offset_table[state][3]; break;
	}
	return rc;
}

/**
 *	llc_sap_add_socket - adds a socket to a SAP
 *	@sap: SAP
 *	@sk: socket
 *
 *	This function adds a socket to the hash tables of a SAP.
 */
void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);
	struct hlist_head *dev_hb = llc_sk_dev_hash(sap, llc->dev->ifindex);
	struct hlist_nulls_head *laddr_hb = llc_sk_laddr_hash(sap, &llc->laddr);

	llc_sap_hold(sap);
	llc_sk(sk)->sap = sap;

	spin_lock_bh(&sap->sk_lock);
	sap->sk_count++;
	sk_nulls_add_node_rcu(sk, laddr_hb);
	hlist_add_head(&llc->dev_hash_node, dev_hb);
	spin_unlock_bh(&sap->sk_lock);
}

/**
 *	llc_sap_remove_socket - removes a socket from SAP
 *	@sap: SAP
 *	@sk: socket
 *
 *	This function removes a connection from the hash tables of a SAP if
 *	the connection was in this list.
 */
void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);

	spin_lock_bh(&sap->sk_lock);
	sk_nulls_del_node_init_rcu(sk);
	hlist_del(&llc->dev_hash_node);
	sap->sk_count--;
	spin_unlock_bh(&sap->sk_lock);
	llc_sap_put(sap);
}

/**
 *	llc_conn_rcv - sends received pdus to the connection state machine
 *	@sk: current connection structure.
 *	@skb: received frame.
 *
 *	Sends received pdus to the connection state machine.
 */
static int llc_conn_rcv(struct sock* sk, struct sk_buff *skb)
{
	struct llc_conn_state_ev *ev = llc_conn_ev(skb);

	ev->type   = LLC_CONN_EV_TYPE_PDU;
	ev->reason = 0;
	return llc_conn_state_process(sk, skb);
}

static struct sock *llc_create_incoming_sock(struct sock *sk,
					     struct net_device *dev,
					     struct llc_addr *saddr,
					     struct llc_addr *daddr)
{
	struct sock *newsk = llc_sk_alloc(sock_net(sk), sk->sk_family, GFP_ATOMIC,
					  sk->sk_prot);
	struct llc_sock *newllc, *llc = llc_sk(sk);

	if (!newsk)
		goto out;
	newllc = llc_sk(newsk);
	memcpy(&newllc->laddr, daddr, sizeof(newllc->laddr));
	memcpy(&newllc->daddr, saddr, sizeof(newllc->daddr));
	newllc->dev = dev;
	dev_hold(dev);
	llc_sap_add_socket(llc->sap, newsk);
	llc_sap_hold(llc->sap);
out:
	return newsk;
}

void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb)
{
	struct llc_addr saddr, daddr;
	struct sock *sk;

	llc_pdu_decode_sa(skb, saddr.mac);
	llc_pdu_decode_ssap(skb, &saddr.lsap);
	llc_pdu_decode_da(skb, daddr.mac);
	llc_pdu_decode_dsap(skb, &daddr.lsap);

	sk = __llc_lookup(sap, &saddr, &daddr);
	if (!sk)
		goto drop;

	bh_lock_sock(sk);
	/*
	 * This has to be done here and not at the upper layer ->accept
	 * method because of the way the PROCOM state machine works:
	 * it needs to set several state variables (see, for instance,
	 * llc_adm_actions_2 in net/llc/llc_c_st.c) and send a packet to
	 * the originator of the new connection, and this state has to be
	 * in the newly created struct sock private area. -acme
	 */
	if (unlikely(sk->sk_state == TCP_LISTEN)) {
		struct sock *newsk = llc_create_incoming_sock(sk, skb->dev,
							      &saddr, &daddr);
		if (!newsk)
			goto drop_unlock;
		skb_set_owner_r(skb, newsk);
	} else {
		/*
		 * Can't be skb_set_owner_r, this will be done at the
		 * llc_conn_state_process function, later on, when we will use
		 * skb_queue_rcv_skb to send it to upper layers, this is
		 * another trick required to cope with how the PROCOM state
		 * machine works. -acme
		 */
		skb->sk = sk;
	}
	if (!sock_owned_by_user(sk))
		llc_conn_rcv(sk, skb);
	else {
		dprintk("%s: adding to backlog...\n", __func__);
		llc_set_backlog_type(skb, LLC_PACKET);
		if (sk_add_backlog(sk, skb))
			goto drop_unlock;
	}
out:
	bh_unlock_sock(sk);
	sock_put(sk);
	return;
drop:
	kfree_skb(skb);
	return;
drop_unlock:
	kfree_skb(skb);
	goto out;
}

#undef LLC_REFCNT_DEBUG
#ifdef LLC_REFCNT_DEBUG
static atomic_t llc_sock_nr;
#endif

/**
 *	llc_backlog_rcv - Processes rx frames and expired timers.
 *	@sk: LLC sock (p8022 connection)
 *	@skb: queued rx frame or event
 *
 *	This function processes frames that has received and timers that has
 *	expired during sending an I pdu (refer to data_req_handler).  frames
 *	queue by llc_rcv function (llc_mac.c) and timers queue by timer
 *	callback functions(llc_c_ac.c).
 */
static int llc_backlog_rcv(struct sock *sk, struct sk_buff *skb)
{
	int rc = 0;
	struct llc_sock *llc = llc_sk(sk);

	if (likely(llc_backlog_type(skb) == LLC_PACKET)) {
		if (likely(llc->state > 1)) /* not closed */
			rc = llc_conn_rcv(sk, skb);
		else
			goto out_kfree_skb;
	} else if (llc_backlog_type(skb) == LLC_EVENT) {
		/* timer expiration event */
		if (likely(llc->state > 1))  /* not closed */
			rc = llc_conn_state_process(sk, skb);
		else
			goto out_kfree_skb;
	} else {
		printk(KERN_ERR "%s: invalid skb in backlog\n", __func__);
		goto out_kfree_skb;
	}
out:
	return rc;
out_kfree_skb:
	kfree_skb(skb);
	goto out;
}

/**
 *     llc_sk_init - Initializes a socket with default llc values.
 *     @sk: socket to initialize.
 *
 *     Initializes a socket with default llc values.
 */
static void llc_sk_init(struct sock* sk)
{
	struct llc_sock *llc = llc_sk(sk);

	llc->state    = LLC_CONN_STATE_ADM;
	llc->inc_cntr = llc->dec_cntr = 2;
	llc->dec_step = llc->connect_step = 1;

	setup_timer(&llc->ack_timer.timer, llc_conn_ack_tmr_cb,
			(unsigned long)sk);
	llc->ack_timer.expire	      = sysctl_llc2_ack_timeout;

	setup_timer(&llc->pf_cycle_timer.timer, llc_conn_pf_cycle_tmr_cb,
			(unsigned long)sk);
	llc->pf_cycle_timer.expire	   = sysctl_llc2_p_timeout;

	setup_timer(&llc->rej_sent_timer.timer, llc_conn_rej_tmr_cb,
			(unsigned long)sk);
	llc->rej_sent_timer.expire	   = sysctl_llc2_rej_timeout;

	setup_timer(&llc->busy_state_timer.timer, llc_conn_busy_tmr_cb,
			(unsigned long)sk);
	llc->busy_state_timer.expire	     = sysctl_llc2_busy_timeout;

	llc->n2 = 2;   /* max retransmit */
	llc->k  = 2;   /* tx win size, will adjust dynam */
	llc->rw = 128; /* rx win size (opt and equal to
			* tx_win of remote LLC) */
	skb_queue_head_init(&llc->pdu_unack_q);
	sk->sk_backlog_rcv = llc_backlog_rcv;
}

/**
 *	llc_sk_alloc - Allocates LLC sock
 *	@family: upper layer protocol family
 *	@priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
 *
 *	Allocates a LLC sock and initializes it. Returns the new LLC sock
 *	or %NULL if there's no memory available for one
 */
struct sock *llc_sk_alloc(struct net *net, int family, gfp_t priority, struct proto *prot)
{
	struct sock *sk = sk_alloc(net, family, priority, prot);

	if (!sk)
		goto out;
	llc_sk_init(sk);
	sock_init_data(NULL, sk);
#ifdef LLC_REFCNT_DEBUG
	atomic_inc(&llc_sock_nr);
	printk(KERN_DEBUG "LLC socket %p created in %s, now we have %d alive\n", sk,
		__func__, atomic_read(&llc_sock_nr));
#endif
out:
	return sk;
}

/**
 *	llc_sk_free - Frees a LLC socket
 *	@sk - socket to free
 *
 *	Frees a LLC socket
 */
void llc_sk_free(struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);

	llc->state = LLC_CONN_OUT_OF_SVC;
	/* Stop all (possibly) running timers */
	llc_conn_ac_stop_all_timers(sk, NULL);
#ifdef DEBUG_LLC_CONN_ALLOC
	printk(KERN_INFO "%s: unackq=%d, txq=%d\n", __func__,
		skb_queue_len(&llc->pdu_unack_q),
		skb_queue_len(&sk->sk_write_queue));
#endif
	skb_queue_purge(&sk->sk_receive_queue);
	skb_queue_purge(&sk->sk_write_queue);
	skb_queue_purge(&llc->pdu_unack_q);
#ifdef LLC_REFCNT_DEBUG
	if (atomic_read(&sk->sk_refcnt) != 1) {
		printk(KERN_DEBUG "Destruction of LLC sock %p delayed in %s, cnt=%d\n",
			sk, __func__, atomic_read(&sk->sk_refcnt));
		printk(KERN_DEBUG "%d LLC sockets are still alive\n",
			atomic_read(&llc_sock_nr));
	} else {
		atomic_dec(&llc_sock_nr);
		printk(KERN_DEBUG "LLC socket %p released in %s, %d are still alive\n", sk,
			__func__, atomic_read(&llc_sock_nr));
	}
#endif
	sock_put(sk);
}

/**
 *	llc_sk_reset - resets a connection
 *	@sk: LLC socket to reset
 *
 *	Resets a connection to the out of service state. Stops its timers
 *	and frees any frames in the queues of the connection.
 */
void llc_sk_reset(struct sock *sk)
{
	struct llc_sock *llc = llc_sk(sk);

	llc_conn_ac_stop_all_timers(sk, NULL);
	skb_queue_purge(&sk->sk_write_queue);
	skb_queue_purge(&llc->pdu_unack_q);
	llc->remote_busy_flag	= 0;
	llc->cause_flag		= 0;
	llc->retry_count	= 0;
	llc_conn_set_p_flag(sk, 0);
	llc->f_flag		= 0;
	llc->s_flag		= 0;
	llc->ack_pf		= 0;
	llc->first_pdu_Ns	= 0;
	llc->ack_must_be_send	= 0;
	llc->dec_step		= 1;
	llc->inc_cntr		= 2;
	llc->dec_cntr		= 2;
	llc->X			= 0;
	llc->failed_data_req	= 0 ;
	llc->last_nr		= 0;
}