1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * DECnet       An implementation of the DECnet protocol suite for the LINUX
  4 *              operating system.  DECnet is implemented using the  BSD Socket
  5 *              interface as the means of communication with the user level.
  6 *
  7 *              DECnet Network Services Protocol (Input)
  8 *
  9 * Author:      Eduardo Marcelo Serrat <emserrat@geocities.com>
 10 *
 11 * Changes:
 12 *
 13 *    Steve Whitehouse:  Split into dn_nsp_in.c and dn_nsp_out.c from
 14 *                       original dn_nsp.c.
 15 *    Steve Whitehouse:  Updated to work with my new routing architecture.
 16 *    Steve Whitehouse:  Add changes from Eduardo Serrat's patches.
 17 *    Steve Whitehouse:  Put all ack handling code in a common routine.
 18 *    Steve Whitehouse:  Put other common bits into dn_nsp_rx()
 19 *    Steve Whitehouse:  More checks on skb->len to catch bogus packets
 20 *                       Fixed various race conditions and possible nasties.
 21 *    Steve Whitehouse:  Now handles returned conninit frames.
 22 *     David S. Miller:  New socket locking
 23 *    Steve Whitehouse:  Fixed lockup when socket filtering was enabled.
 24 *         Paul Koning:  Fix to push CC sockets into RUN when acks are
 25 *                       received.
 26 *    Steve Whitehouse:
 27 *   Patrick Caulfield:  Checking conninits for correctness & sending of error
 28 *                       responses.
 29 *    Steve Whitehouse:  Added backlog congestion level return codes.
 30 *   Patrick Caulfield:
 31 *    Steve Whitehouse:  Added flow control support (outbound)
 32 *    Steve Whitehouse:  Prepare for nonlinear skbs
 33 */
 34
 35/******************************************************************************
 36    (c) 1995-1998 E.M. Serrat		emserrat@geocities.com
 37
 38*******************************************************************************/
 39
 40#include <linux/errno.h>
 41#include <linux/types.h>
 42#include <linux/socket.h>
 43#include <linux/in.h>
 44#include <linux/kernel.h>
 45#include <linux/timer.h>
 46#include <linux/string.h>
 47#include <linux/sockios.h>
 48#include <linux/net.h>
 49#include <linux/netdevice.h>
 50#include <linux/inet.h>
 51#include <linux/route.h>
 52#include <linux/slab.h>
 53#include <net/sock.h>
 54#include <net/tcp_states.h>
 55#include <linux/fcntl.h>
 56#include <linux/mm.h>
 57#include <linux/termios.h>
 58#include <linux/interrupt.h>
 59#include <linux/proc_fs.h>
 60#include <linux/stat.h>
 61#include <linux/init.h>
 62#include <linux/poll.h>
 63#include <linux/netfilter_decnet.h>
 64#include <net/neighbour.h>
 65#include <net/dst.h>
 66#include <net/dn.h>
 67#include <net/dn_nsp.h>
 68#include <net/dn_dev.h>
 69#include <net/dn_route.h>
 70
 71extern int decnet_log_martians;
 72
 73static void dn_log_martian(struct sk_buff *skb, const char *msg)
 74{
 75	if (decnet_log_martians) {
 76		char *devname = skb->dev ? skb->dev->name : "???";
 77		struct dn_skb_cb *cb = DN_SKB_CB(skb);
 78		net_info_ratelimited("DECnet: Martian packet (%s) dev=%s src=0x%04hx dst=0x%04hx srcport=0x%04hx dstport=0x%04hx\n",
 79				     msg, devname,
 80				     le16_to_cpu(cb->src),
 81				     le16_to_cpu(cb->dst),
 82				     le16_to_cpu(cb->src_port),
 83				     le16_to_cpu(cb->dst_port));
 84	}
 85}
 86
 87/*
 88 * For this function we've flipped the cross-subchannel bit
 89 * if the message is an otherdata or linkservice message. Thus
 90 * we can use it to work out what to update.
 91 */
 92static void dn_ack(struct sock *sk, struct sk_buff *skb, unsigned short ack)
 93{
 94	struct dn_scp *scp = DN_SK(sk);
 95	unsigned short type = ((ack >> 12) & 0x0003);
 96	int wakeup = 0;
 97
 98	switch (type) {
 99	case 0: /* ACK - Data */
100		if (dn_after(ack, scp->ackrcv_dat)) {
101			scp->ackrcv_dat = ack & 0x0fff;
102			wakeup |= dn_nsp_check_xmit_queue(sk, skb,
103							  &scp->data_xmit_queue,
104							  ack);
105		}
106		break;
107	case 1: /* NAK - Data */
108		break;
109	case 2: /* ACK - OtherData */
110		if (dn_after(ack, scp->ackrcv_oth)) {
111			scp->ackrcv_oth = ack & 0x0fff;
112			wakeup |= dn_nsp_check_xmit_queue(sk, skb,
113							  &scp->other_xmit_queue,
114							  ack);
115		}
116		break;
117	case 3: /* NAK - OtherData */
118		break;
119	}
120
121	if (wakeup && !sock_flag(sk, SOCK_DEAD))
122		sk->sk_state_change(sk);
123}
124
125/*
126 * This function is a universal ack processor.
127 */
128static int dn_process_ack(struct sock *sk, struct sk_buff *skb, int oth)
129{
130	__le16 *ptr = (__le16 *)skb->data;
131	int len = 0;
132	unsigned short ack;
133
134	if (skb->len < 2)
135		return len;
136
137	if ((ack = le16_to_cpu(*ptr)) & 0x8000) {
138		skb_pull(skb, 2);
139		ptr++;
140		len += 2;
141		if ((ack & 0x4000) == 0) {
142			if (oth)
143				ack ^= 0x2000;
144			dn_ack(sk, skb, ack);
145		}
146	}
147
148	if (skb->len < 2)
149		return len;
150
151	if ((ack = le16_to_cpu(*ptr)) & 0x8000) {
152		skb_pull(skb, 2);
153		len += 2;
154		if ((ack & 0x4000) == 0) {
155			if (oth)
156				ack ^= 0x2000;
157			dn_ack(sk, skb, ack);
158		}
159	}
160
161	return len;
162}
163
164
165/**
166 * dn_check_idf - Check an image data field format is correct.
167 * @pptr: Pointer to pointer to image data
168 * @len: Pointer to length of image data
169 * @max: The maximum allowed length of the data in the image data field
170 * @follow_on: Check that this many bytes exist beyond the end of the image data
171 *
172 * Returns: 0 if ok, -1 on error
173 */
174static inline int dn_check_idf(unsigned char **pptr, int *len, unsigned char max, unsigned char follow_on)
175{
176	unsigned char *ptr = *pptr;
177	unsigned char flen = *ptr++;
178
179	(*len)--;
180	if (flen > max)
181		return -1;
182	if ((flen + follow_on) > *len)
183		return -1;
184
185	*len -= flen;
186	*pptr = ptr + flen;
187	return 0;
188}
189
190/*
191 * Table of reason codes to pass back to node which sent us a badly
192 * formed message, plus text messages for the log. A zero entry in
193 * the reason field means "don't reply" otherwise a disc init is sent with
194 * the specified reason code.
195 */
196static struct {
197	unsigned short reason;
198	const char *text;
199} ci_err_table[] = {
200 { 0,             "CI: Truncated message" },
201 { NSP_REASON_ID, "CI: Destination username error" },
202 { NSP_REASON_ID, "CI: Destination username type" },
203 { NSP_REASON_US, "CI: Source username error" },
204 { 0,             "CI: Truncated at menuver" },
205 { 0,             "CI: Truncated before access or user data" },
206 { NSP_REASON_IO, "CI: Access data format error" },
207 { NSP_REASON_IO, "CI: User data format error" }
208};
209
210/*
211 * This function uses a slightly different lookup method
212 * to find its sockets, since it searches on object name/number
213 * rather than port numbers. Various tests are done to ensure that
214 * the incoming data is in the correct format before it is queued to
215 * a socket.
216 */
217static struct sock *dn_find_listener(struct sk_buff *skb, unsigned short *reason)
218{
219	struct dn_skb_cb *cb = DN_SKB_CB(skb);
220	struct nsp_conn_init_msg *msg = (struct nsp_conn_init_msg *)skb->data;
221	struct sockaddr_dn dstaddr;
222	struct sockaddr_dn srcaddr;
223	unsigned char type = 0;
224	int dstlen;
225	int srclen;
226	unsigned char *ptr;
227	int len;
228	int err = 0;
229	unsigned char menuver;
230
231	memset(&dstaddr, 0, sizeof(struct sockaddr_dn));
232	memset(&srcaddr, 0, sizeof(struct sockaddr_dn));
233
234	/*
235	 * 1. Decode & remove message header
236	 */
237	cb->src_port = msg->srcaddr;
238	cb->dst_port = msg->dstaddr;
239	cb->services = msg->services;
240	cb->info     = msg->info;
241	cb->segsize  = le16_to_cpu(msg->segsize);
242
243	if (!pskb_may_pull(skb, sizeof(*msg)))
244		goto err_out;
245
246	skb_pull(skb, sizeof(*msg));
247
248	len = skb->len;
249	ptr = skb->data;
250
251	/*
252	 * 2. Check destination end username format
253	 */
254	dstlen = dn_username2sockaddr(ptr, len, &dstaddr, &type);
255	err++;
256	if (dstlen < 0)
257		goto err_out;
258
259	err++;
260	if (type > 1)
261		goto err_out;
262
263	len -= dstlen;
264	ptr += dstlen;
265
266	/*
267	 * 3. Check source end username format
268	 */
269	srclen = dn_username2sockaddr(ptr, len, &srcaddr, &type);
270	err++;
271	if (srclen < 0)
272		goto err_out;
273
274	len -= srclen;
275	ptr += srclen;
276	err++;
277	if (len < 1)
278		goto err_out;
279
280	menuver = *ptr;
281	ptr++;
282	len--;
283
284	/*
285	 * 4. Check that optional data actually exists if menuver says it does
286	 */
287	err++;
288	if ((menuver & (DN_MENUVER_ACC | DN_MENUVER_USR)) && (len < 1))
289		goto err_out;
290
291	/*
292	 * 5. Check optional access data format
293	 */
294	err++;
295	if (menuver & DN_MENUVER_ACC) {
296		if (dn_check_idf(&ptr, &len, 39, 1))
297			goto err_out;
298		if (dn_check_idf(&ptr, &len, 39, 1))
299			goto err_out;
300		if (dn_check_idf(&ptr, &len, 39, (menuver & DN_MENUVER_USR) ? 1 : 0))
301			goto err_out;
302	}
303
304	/*
305	 * 6. Check optional user data format
306	 */
307	err++;
308	if (menuver & DN_MENUVER_USR) {
309		if (dn_check_idf(&ptr, &len, 16, 0))
310			goto err_out;
311	}
312
313	/*
314	 * 7. Look up socket based on destination end username
315	 */
316	return dn_sklist_find_listener(&dstaddr);
317err_out:
318	dn_log_martian(skb, ci_err_table[err].text);
319	*reason = ci_err_table[err].reason;
320	return NULL;
321}
322
323
324static void dn_nsp_conn_init(struct sock *sk, struct sk_buff *skb)
325{
326	if (sk_acceptq_is_full(sk)) {
327		kfree_skb(skb);
328		return;
329	}
330
331	sk->sk_ack_backlog++;
332	skb_queue_tail(&sk->sk_receive_queue, skb);
333	sk->sk_state_change(sk);
334}
335
336static void dn_nsp_conn_conf(struct sock *sk, struct sk_buff *skb)
337{
338	struct dn_skb_cb *cb = DN_SKB_CB(skb);
339	struct dn_scp *scp = DN_SK(sk);
340	unsigned char *ptr;
341
342	if (skb->len < 4)
343		goto out;
344
345	ptr = skb->data;
346	cb->services = *ptr++;
347	cb->info = *ptr++;
348	cb->segsize = le16_to_cpu(*(__le16 *)ptr);
349
350	if ((scp->state == DN_CI) || (scp->state == DN_CD)) {
351		scp->persist = 0;
352		scp->addrrem = cb->src_port;
353		sk->sk_state = TCP_ESTABLISHED;
354		scp->state = DN_RUN;
355		scp->services_rem = cb->services;
356		scp->info_rem = cb->info;
357		scp->segsize_rem = cb->segsize;
358
359		if ((scp->services_rem & NSP_FC_MASK) == NSP_FC_NONE)
360			scp->max_window = decnet_no_fc_max_cwnd;
361
362		if (skb->len > 0) {
363			u16 dlen = *skb->data;
364			if ((dlen <= 16) && (dlen <= skb->len)) {
365				scp->conndata_in.opt_optl = cpu_to_le16(dlen);
366				skb_copy_from_linear_data_offset(skb, 1,
367					      scp->conndata_in.opt_data, dlen);
368			}
369		}
370		dn_nsp_send_link(sk, DN_NOCHANGE, 0);
371		if (!sock_flag(sk, SOCK_DEAD))
372			sk->sk_state_change(sk);
373	}
374
375out:
376	kfree_skb(skb);
377}
378
379static void dn_nsp_conn_ack(struct sock *sk, struct sk_buff *skb)
380{
381	struct dn_scp *scp = DN_SK(sk);
382
383	if (scp->state == DN_CI) {
384		scp->state = DN_CD;
385		scp->persist = 0;
386	}
387
388	kfree_skb(skb);
389}
390
391static void dn_nsp_disc_init(struct sock *sk, struct sk_buff *skb)
392{
393	struct dn_scp *scp = DN_SK(sk);
394	struct dn_skb_cb *cb = DN_SKB_CB(skb);
395	unsigned short reason;
396
397	if (skb->len < 2)
398		goto out;
399
400	reason = le16_to_cpu(*(__le16 *)skb->data);
401	skb_pull(skb, 2);
402
403	scp->discdata_in.opt_status = cpu_to_le16(reason);
404	scp->discdata_in.opt_optl   = 0;
405	memset(scp->discdata_in.opt_data, 0, 16);
406
407	if (skb->len > 0) {
408		u16 dlen = *skb->data;
409		if ((dlen <= 16) && (dlen <= skb->len)) {
410			scp->discdata_in.opt_optl = cpu_to_le16(dlen);
411			skb_copy_from_linear_data_offset(skb, 1, scp->discdata_in.opt_data, dlen);
412		}
413	}
414
415	scp->addrrem = cb->src_port;
416	sk->sk_state = TCP_CLOSE;
417
418	switch (scp->state) {
419	case DN_CI:
420	case DN_CD:
421		scp->state = DN_RJ;
422		sk->sk_err = ECONNREFUSED;
423		break;
424	case DN_RUN:
425		sk->sk_shutdown |= SHUTDOWN_MASK;
426		scp->state = DN_DN;
427		break;
428	case DN_DI:
429		scp->state = DN_DIC;
430		break;
431	}
432
433	if (!sock_flag(sk, SOCK_DEAD)) {
434		if (sk->sk_socket->state != SS_UNCONNECTED)
435			sk->sk_socket->state = SS_DISCONNECTING;
436		sk->sk_state_change(sk);
437	}
438
439	/*
440	 * It appears that its possible for remote machines to send disc
441	 * init messages with no port identifier if we are in the CI and
442	 * possibly also the CD state. Obviously we shouldn't reply with
443	 * a message if we don't know what the end point is.
444	 */
445	if (scp->addrrem) {
446		dn_nsp_send_disc(sk, NSP_DISCCONF, NSP_REASON_DC, GFP_ATOMIC);
447	}
448	scp->persist_fxn = dn_destroy_timer;
449	scp->persist = dn_nsp_persist(sk);
450
451out:
452	kfree_skb(skb);
453}
454
455/*
456 * disc_conf messages are also called no_resources or no_link
457 * messages depending upon the "reason" field.
458 */
459static void dn_nsp_disc_conf(struct sock *sk, struct sk_buff *skb)
460{
461	struct dn_scp *scp = DN_SK(sk);
462	unsigned short reason;
463
464	if (skb->len != 2)
465		goto out;
466
467	reason = le16_to_cpu(*(__le16 *)skb->data);
468
469	sk->sk_state = TCP_CLOSE;
470
471	switch (scp->state) {
472	case DN_CI:
473		scp->state = DN_NR;
474		break;
475	case DN_DR:
476		if (reason == NSP_REASON_DC)
477			scp->state = DN_DRC;
478		if (reason == NSP_REASON_NL)
479			scp->state = DN_CN;
480		break;
481	case DN_DI:
482		scp->state = DN_DIC;
483		break;
484	case DN_RUN:
485		sk->sk_shutdown |= SHUTDOWN_MASK;
486		/* fall through */
487	case DN_CC:
488		scp->state = DN_CN;
489	}
490
491	if (!sock_flag(sk, SOCK_DEAD)) {
492		if (sk->sk_socket->state != SS_UNCONNECTED)
493			sk->sk_socket->state = SS_DISCONNECTING;
494		sk->sk_state_change(sk);
495	}
496
497	scp->persist_fxn = dn_destroy_timer;
498	scp->persist = dn_nsp_persist(sk);
499
500out:
501	kfree_skb(skb);
502}
503
504static void dn_nsp_linkservice(struct sock *sk, struct sk_buff *skb)
505{
506	struct dn_scp *scp = DN_SK(sk);
507	unsigned short segnum;
508	unsigned char lsflags;
509	signed char fcval;
510	int wake_up = 0;
511	char *ptr = skb->data;
512	unsigned char fctype = scp->services_rem & NSP_FC_MASK;
513
514	if (skb->len != 4)
515		goto out;
516
517	segnum = le16_to_cpu(*(__le16 *)ptr);
518	ptr += 2;
519	lsflags = *(unsigned char *)ptr++;
520	fcval = *ptr;
521
522	/*
523	 * Here we ignore erronous packets which should really
524	 * should cause a connection abort. It is not critical
525	 * for now though.
526	 */
527	if (lsflags & 0xf8)
528		goto out;
529
530	if (seq_next(scp->numoth_rcv, segnum)) {
531		seq_add(&scp->numoth_rcv, 1);
532		switch(lsflags & 0x04) { /* FCVAL INT */
533		case 0x00: /* Normal Request */
534			switch(lsflags & 0x03) { /* FCVAL MOD */
535			case 0x00: /* Request count */
536				if (fcval < 0) {
537					unsigned char p_fcval = -fcval;
538					if ((scp->flowrem_dat > p_fcval) &&
539					    (fctype == NSP_FC_SCMC)) {
540						scp->flowrem_dat -= p_fcval;
541					}
542				} else if (fcval > 0) {
543					scp->flowrem_dat += fcval;
544					wake_up = 1;
545				}
546				break;
547			case 0x01: /* Stop outgoing data */
548				scp->flowrem_sw = DN_DONTSEND;
549				break;
550			case 0x02: /* Ok to start again */
551				scp->flowrem_sw = DN_SEND;
552				dn_nsp_output(sk);
553				wake_up = 1;
554			}
555			break;
556		case 0x04: /* Interrupt Request */
557			if (fcval > 0) {
558				scp->flowrem_oth += fcval;
559				wake_up = 1;
560			}
561			break;
562		}
563		if (wake_up && !sock_flag(sk, SOCK_DEAD))
564			sk->sk_state_change(sk);
565	}
566
567	dn_nsp_send_oth_ack(sk);
568
569out:
570	kfree_skb(skb);
571}
572
573/*
574 * Copy of sock_queue_rcv_skb (from sock.h) without
575 * bh_lock_sock() (its already held when this is called) which
576 * also allows data and other data to be queued to a socket.
577 */
578static __inline__ int dn_queue_skb(struct sock *sk, struct sk_buff *skb, int sig, struct sk_buff_head *queue)
579{
580	int err;
581
582	/* Cast skb->rcvbuf to unsigned... It's pointless, but reduces
583	   number of warnings when compiling with -W --ANK
584	 */
585	if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
586	    (unsigned int)sk->sk_rcvbuf) {
587		err = -ENOMEM;
588		goto out;
589	}
590
591	err = sk_filter(sk, skb);
592	if (err)
593		goto out;
594
595	skb_set_owner_r(skb, sk);
596	skb_queue_tail(queue, skb);
597
598	if (!sock_flag(sk, SOCK_DEAD))
599		sk->sk_data_ready(sk);
600out:
601	return err;
602}
603
604static void dn_nsp_otherdata(struct sock *sk, struct sk_buff *skb)
605{
606	struct dn_scp *scp = DN_SK(sk);
607	unsigned short segnum;
608	struct dn_skb_cb *cb = DN_SKB_CB(skb);
609	int queued = 0;
610
611	if (skb->len < 2)
612		goto out;
613
614	cb->segnum = segnum = le16_to_cpu(*(__le16 *)skb->data);
615	skb_pull(skb, 2);
616
617	if (seq_next(scp->numoth_rcv, segnum)) {
618
619		if (dn_queue_skb(sk, skb, SIGURG, &scp->other_receive_queue) == 0) {
620			seq_add(&scp->numoth_rcv, 1);
621			scp->other_report = 0;
622			queued = 1;
623		}
624	}
625
626	dn_nsp_send_oth_ack(sk);
627out:
628	if (!queued)
629		kfree_skb(skb);
630}
631
632static void dn_nsp_data(struct sock *sk, struct sk_buff *skb)
633{
634	int queued = 0;
635	unsigned short segnum;
636	struct dn_skb_cb *cb = DN_SKB_CB(skb);
637	struct dn_scp *scp = DN_SK(sk);
638
639	if (skb->len < 2)
640		goto out;
641
642	cb->segnum = segnum = le16_to_cpu(*(__le16 *)skb->data);
643	skb_pull(skb, 2);
644
645	if (seq_next(scp->numdat_rcv, segnum)) {
646		if (dn_queue_skb(sk, skb, SIGIO, &sk->sk_receive_queue) == 0) {
647			seq_add(&scp->numdat_rcv, 1);
648			queued = 1;
649		}
650
651		if ((scp->flowloc_sw == DN_SEND) && dn_congested(sk)) {
652			scp->flowloc_sw = DN_DONTSEND;
653			dn_nsp_send_link(sk, DN_DONTSEND, 0);
654		}
655	}
656
657	dn_nsp_send_data_ack(sk);
658out:
659	if (!queued)
660		kfree_skb(skb);
661}
662
663/*
664 * If one of our conninit messages is returned, this function
665 * deals with it. It puts the socket into the NO_COMMUNICATION
666 * state.
667 */
668static void dn_returned_conn_init(struct sock *sk, struct sk_buff *skb)
669{
670	struct dn_scp *scp = DN_SK(sk);
671
672	if (scp->state == DN_CI) {
673		scp->state = DN_NC;
674		sk->sk_state = TCP_CLOSE;
675		if (!sock_flag(sk, SOCK_DEAD))
676			sk->sk_state_change(sk);
677	}
678
679	kfree_skb(skb);
680}
681
682static int dn_nsp_no_socket(struct sk_buff *skb, unsigned short reason)
683{
684	struct dn_skb_cb *cb = DN_SKB_CB(skb);
685	int ret = NET_RX_DROP;
686
687	/* Must not reply to returned packets */
688	if (cb->rt_flags & DN_RT_F_RTS)
689		goto out;
690
691	if ((reason != NSP_REASON_OK) && ((cb->nsp_flags & 0x0c) == 0x08)) {
692		switch (cb->nsp_flags & 0x70) {
693		case 0x10:
694		case 0x60: /* (Retransmitted) Connect Init */
695			dn_nsp_return_disc(skb, NSP_DISCINIT, reason);
696			ret = NET_RX_SUCCESS;
697			break;
698		case 0x20: /* Connect Confirm */
699			dn_nsp_return_disc(skb, NSP_DISCCONF, reason);
700			ret = NET_RX_SUCCESS;
701			break;
702		}
703	}
704
705out:
706	kfree_skb(skb);
707	return ret;
708}
709
710static int dn_nsp_rx_packet(struct net *net, struct sock *sk2,
711			    struct sk_buff *skb)
712{
713	struct dn_skb_cb *cb = DN_SKB_CB(skb);
714	struct sock *sk = NULL;
715	unsigned char *ptr = (unsigned char *)skb->data;
716	unsigned short reason = NSP_REASON_NL;
717
718	if (!pskb_may_pull(skb, 2))
719		goto free_out;
720
721	skb_reset_transport_header(skb);
722	cb->nsp_flags = *ptr++;
723
724	if (decnet_debug_level & 2)
725		printk(KERN_DEBUG "dn_nsp_rx: Message type 0x%02x\n", (int)cb->nsp_flags);
726
727	if (cb->nsp_flags & 0x83)
728		goto free_out;
729
730	/*
731	 * Filter out conninits and useless packet types
732	 */
733	if ((cb->nsp_flags & 0x0c) == 0x08) {
734		switch (cb->nsp_flags & 0x70) {
735		case 0x00: /* NOP */
736		case 0x70: /* Reserved */
737		case 0x50: /* Reserved, Phase II node init */
738			goto free_out;
739		case 0x10:
740		case 0x60:
741			if (unlikely(cb->rt_flags & DN_RT_F_RTS))
742				goto free_out;
743			sk = dn_find_listener(skb, &reason);
744			goto got_it;
745		}
746	}
747
748	if (!pskb_may_pull(skb, 3))
749		goto free_out;
750
751	/*
752	 * Grab the destination address.
753	 */
754	cb->dst_port = *(__le16 *)ptr;
755	cb->src_port = 0;
756	ptr += 2;
757
758	/*
759	 * If not a connack, grab the source address too.
760	 */
761	if (pskb_may_pull(skb, 5)) {
762		cb->src_port = *(__le16 *)ptr;
763		ptr += 2;
764		skb_pull(skb, 5);
765	}
766
767	/*
768	 * Returned packets...
769	 * Swap src & dst and look up in the normal way.
770	 */
771	if (unlikely(cb->rt_flags & DN_RT_F_RTS)) {
772		swap(cb->dst_port, cb->src_port);
773		swap(cb->dst, cb->src);
774	}
775
776	/*
777	 * Find the socket to which this skb is destined.
778	 */
779	sk = dn_find_by_skb(skb);
780got_it:
781	if (sk != NULL) {
782		struct dn_scp *scp = DN_SK(sk);
783
784		/* Reset backoff */
785		scp->nsp_rxtshift = 0;
786
787		/*
788		 * We linearize everything except data segments here.
789		 */
790		if (cb->nsp_flags & ~0x60) {
791			if (unlikely(skb_linearize(skb)))
792				goto free_out;
793		}
794
795		return sk_receive_skb(sk, skb, 0);
796	}
797
798	return dn_nsp_no_socket(skb, reason);
799
800free_out:
801	kfree_skb(skb);
802	return NET_RX_DROP;
803}
804
805int dn_nsp_rx(struct sk_buff *skb)
806{
807	return NF_HOOK(NFPROTO_DECNET, NF_DN_LOCAL_IN,
808		       &init_net, NULL, skb, skb->dev, NULL,
809		       dn_nsp_rx_packet);
810}
811
812/*
813 * This is the main receive routine for sockets. It is called
814 * from the above when the socket is not busy, and also from
815 * sock_release() when there is a backlog queued up.
816 */
817int dn_nsp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
818{
819	struct dn_scp *scp = DN_SK(sk);
820	struct dn_skb_cb *cb = DN_SKB_CB(skb);
821
822	if (cb->rt_flags & DN_RT_F_RTS) {
823		if (cb->nsp_flags == 0x18 || cb->nsp_flags == 0x68)
824			dn_returned_conn_init(sk, skb);
825		else
826			kfree_skb(skb);
827		return NET_RX_SUCCESS;
828	}
829
830	/*
831	 * Control packet.
832	 */
833	if ((cb->nsp_flags & 0x0c) == 0x08) {
834		switch (cb->nsp_flags & 0x70) {
835		case 0x10:
836		case 0x60:
837			dn_nsp_conn_init(sk, skb);
838			break;
839		case 0x20:
840			dn_nsp_conn_conf(sk, skb);
841			break;
842		case 0x30:
843			dn_nsp_disc_init(sk, skb);
844			break;
845		case 0x40:
846			dn_nsp_disc_conf(sk, skb);
847			break;
848		}
849
850	} else if (cb->nsp_flags == 0x24) {
851		/*
852		 * Special for connacks, 'cos they don't have
853		 * ack data or ack otherdata info.
854		 */
855		dn_nsp_conn_ack(sk, skb);
856	} else {
857		int other = 1;
858
859		/* both data and ack frames can kick a CC socket into RUN */
860		if ((scp->state == DN_CC) && !sock_flag(sk, SOCK_DEAD)) {
861			scp->state = DN_RUN;
862			sk->sk_state = TCP_ESTABLISHED;
863			sk->sk_state_change(sk);
864		}
865
866		if ((cb->nsp_flags & 0x1c) == 0)
867			other = 0;
868		if (cb->nsp_flags == 0x04)
869			other = 0;
870
871		/*
872		 * Read out ack data here, this applies equally
873		 * to data, other data, link serivce and both
874		 * ack data and ack otherdata.
875		 */
876		dn_process_ack(sk, skb, other);
877
878		/*
879		 * If we've some sort of data here then call a
880		 * suitable routine for dealing with it, otherwise
881		 * the packet is an ack and can be discarded.
882		 */
883		if ((cb->nsp_flags & 0x0c) == 0) {
884
885			if (scp->state != DN_RUN)
886				goto free_out;
887
888			switch (cb->nsp_flags) {
889			case 0x10: /* LS */
890				dn_nsp_linkservice(sk, skb);
891				break;
892			case 0x30: /* OD */
893				dn_nsp_otherdata(sk, skb);
894				break;
895			default:
896				dn_nsp_data(sk, skb);
897			}
898
899		} else { /* Ack, chuck it out here */
900free_out:
901			kfree_skb(skb);
902		}
903	}
904
905	return NET_RX_SUCCESS;
906}