net/decnet/dn_nsp_in.c

   1
   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  */
  27
  28 /******************************************************************************
  29     (c) 1995-1998 E.M. Serrat           emserrat@geocities.com
  30
  31     This program is free software; you can redistribute it and/or modify
  32     it under the terms of the GNU General Public License as published by
  33     the Free Software Foundation; either version 2 of the License, or
  34     any later version.
  35
  36     This program is distributed in the hope that it will be useful,
  37     but WITHOUT ANY WARRANTY; without even the implied warranty of
  38     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  39     GNU General Public License for more details.
  40 *******************************************************************************/
  41
  42 #include <linux/config.h>
  43 #include <linux/errno.h>
  44 #include <linux/types.h>
  45 #include <linux/socket.h>
  46 #include <linux/in.h>
  47 #include <linux/kernel.h>
  48 #include <linux/sched.h>
  49 #include <linux/timer.h>
  50 #include <linux/string.h>
  51 #include <linux/sockios.h>
  52 #include <linux/net.h>
  53 #include <linux/netdevice.h>
  54 #include <linux/inet.h>
  55 #include <linux/route.h>
  56 #include <net/sock.h>
  57 #include <asm/segment.h>
  58 #include <asm/system.h>
  59 #include <linux/fcntl.h>
  60 #include <linux/mm.h>
  61 #include <linux/termios.h>
  62 #include <linux/interrupt.h>
  63 #include <linux/proc_fs.h>
  64 #include <linux/stat.h>
  65 #include <linux/init.h>
  66 #include <linux/poll.h>
  67 #include <linux/netfilter_decnet.h>
  68 #include <net/neighbour.h>
  69 #include <net/dst.h>
  70 #include <net/dn_nsp.h>
  71 #include <net/dn_dev.h>
  72 #include <net/dn_route.h>
  73
  74
  75 /*
  76  * For this function we've flipped the cross-subchannel bit
  77  * if the message is an otherdata or linkservice message. Thus
  78  * we can use it to work out what to update.
  79  */
  80 static void dn_ack(struct sock *sk, struct sk_buff *skb, unsigned short ack)
  81 {
  82         struct dn_scp *scp = &sk->protinfo.dn;
  83         unsigned short type = ((ack >> 12) & 0x0003);
  84         int wakeup = 0;
  85
  86         /* printk(KERN_DEBUG "dn_ack: %hd 0x%04hx\n", type, ack); */
  87
  88         switch(type) {
  89                 case 0: /* ACK - Data */
  90                         if (after(ack, scp->ackrcv_dat)) {
  91                                 scp->ackrcv_dat = ack & 0x0fff;
  92                                 wakeup |= dn_nsp_check_xmit_queue(sk, skb, &scp->data_xmit_queue, ack);
  93                         }
  94                         break;
  95                 case 1: /* NAK - Data */
  96                         break;
  97                 case 2: /* ACK - OtherData */
  98                         if (after(ack, scp->ackrcv_oth)) {
  99                                 scp->ackrcv_oth = ack & 0x0fff;
 100                                 wakeup |= dn_nsp_check_xmit_queue(sk, skb, &scp->other_xmit_queue, ack);
 101                         }
 102                         break;
 103                 case 3: /* NAK - OtherData */
 104                         break;
 105         }
 106
 107         if (wakeup && !sk->dead)
 108                 sk->state_change(sk);
 109 }
 110
 111 /*
 112  * This function is a universal ack processor.
 113  */
 114 static int dn_process_ack(struct sock *sk, struct sk_buff *skb, int oth)
 115 {
 116         unsigned short *ptr = (unsigned short *)skb->data;
 117         int len = 0;
 118         unsigned short ack;
 119
 120         if (skb->len < 2)
 121                 return len;
 122
 123         if ((ack = dn_ntohs(*ptr)) & 0x8000) {
 124                 skb_pull(skb, 2);
 125                 ptr++;
 126                 len += 2;
 127                 if ((ack & 0x4000) == 0) {
 128                         if (oth)
 129                                 ack ^= 0x2000;
 130                         dn_ack(sk, skb, ack);
 131                 }
 132         }
 133
 134         if (skb->len < 2)
 135                 return len;
 136
 137         if ((ack = dn_ntohs(*ptr)) & 0x8000) {
 138                 skb_pull(skb, 2);
 139                 len += 2;
 140                 if ((ack & 0x4000) == 0) {
 141                         if (oth)
 142                                 ack ^= 0x2000;
 143                         dn_ack(sk, skb, ack);
 144                 }
 145         }
 146
 147         return len;
 148 }
 149
 150
 151 /*
 152  * This function uses a slightly different lookup method
 153  * to find its sockets, since it searches on object name/number
 154  * rather than port numbers
 155  */
 156 static struct sock *dn_find_listener(struct sk_buff *skb)
 157 {
 158         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 159         struct nsp_conn_init_msg *msg = (struct nsp_conn_init_msg *)skb->data;
 160         struct sockaddr_dn addr;
 161         unsigned char type = 0;
 162
 163         memset(&addr, 0, sizeof(struct sockaddr_dn));
 164
 165         cb->src_port = msg->srcaddr;
 166         cb->dst_port = msg->dstaddr;
 167         cb->services = msg->services;
 168         cb->info     = msg->info;
 169         cb->segsize  = dn_ntohs(msg->segsize);
 170
 171         skb_pull(skb, sizeof(*msg));
 172
 173         /* printk(KERN_DEBUG "username2sockaddr 1\n"); */
 174         if (dn_username2sockaddr(skb->data, skb->len, &addr, &type) < 0)
 175                 goto err_out;
 176
 177         if (type > 1)
 178                 goto err_out;
 179
 180         /* printk(KERN_DEBUG "looking for listener...\n"); */
 181         return dn_sklist_find_listener(&addr);
 182 err_out:
 183         return NULL;
 184 }
 185
 186 static void dn_nsp_conn_init(struct sock *sk, struct sk_buff *skb)
 187 {
 188         /* printk(KERN_DEBUG "checking backlog...\n"); */
 189         if (sk->ack_backlog >= sk->max_ack_backlog) {
 190                 kfree_skb(skb);
 191                 return;
 192         }
 193
 194         /* printk(KERN_DEBUG "waking up socket...\n"); */
 195         sk->ack_backlog++;
 196         skb_queue_tail(&sk->receive_queue, skb);
 197         sk->state_change(sk);
 198 }
 199
 200 static void dn_nsp_conn_conf(struct sock *sk, struct sk_buff *skb)
 201 {
 202         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 203         struct dn_scp *scp = &sk->protinfo.dn;
 204
 205         if (skb->len < 3)
 206                 goto out;
 207
 208         cb->services = *skb->data;
 209         cb->info = *(skb->data+1);
 210         skb_pull(skb, 2);
 211         cb->segsize = dn_ntohs(*(__u16 *)skb->data);
 212         skb_pull(skb, 2);
 213
 214         /*
 215          * FIXME: Check out services and info fields to check that
 216          * we can talk to this kind of node.
 217          */
 218
 219         if ((scp->state == DN_CI) || (scp->state == DN_CD)) {
 220                 scp->persist = 0;
 221                 scp->addrrem = cb->src_port;
 222                 sk->state = TCP_ESTABLISHED;
 223                 scp->state = DN_RUN;
 224
 225                 if (scp->mss > cb->segsize)
 226                         scp->mss = cb->segsize;
 227                 if (scp->mss < 230)
 228                         scp->mss = 230;
 229
 230                 if (skb->len > 0) {
 231                         unsigned char dlen = *skb->data;
 232                         if ((dlen <= 16) && (dlen <= skb->len)) {
 233                                 scp->conndata_in.opt_optl = dlen;
 234                                 memcpy(scp->conndata_in.opt_data, skb->data + 1, dlen);
 235                         }
 236                 }
 237                 dn_nsp_send_lnk(sk, DN_NOCHANGE);
 238                 if (!sk->dead)
 239                         sk->state_change(sk);
 240         }
 241
 242 out:
 243         kfree_skb(skb);
 244 }
 245
 246 static void dn_nsp_conn_ack(struct sock *sk, struct sk_buff *skb)
 247 {
 248         struct dn_scp *scp = &sk->protinfo.dn;
 249
 250         if (scp->state == DN_CI) {
 251                 scp->state = DN_CD;
 252                 scp->persist = 0;
 253         }
 254
 255         kfree_skb(skb);
 256 }
 257
 258 static void dn_nsp_disc_init(struct sock *sk, struct sk_buff *skb)
 259 {
 260         struct dn_scp *scp = &sk->protinfo.dn;
 261         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 262         unsigned short reason;
 263
 264         if (skb->len < 2)
 265                 goto out;
 266
 267         reason = dn_ntohs(*(__u16 *)skb->data);
 268         skb_pull(skb, 2);
 269
 270         scp->discdata_in.opt_status = reason;
 271         scp->discdata_in.opt_optl   = 0;
 272         memset(scp->discdata_in.opt_data, 0, 16);
 273
 274         if (skb->len > 0) {
 275                 unsigned char dlen = *skb->data;
 276                 if ((dlen <= 16) && (dlen <= skb->len)) {
 277                         scp->discdata_in.opt_optl = dlen;
 278                         memcpy(scp->discdata_in.opt_data, skb->data + 1, dlen);
 279                 }
 280         }
 281
 282         scp->addrrem = cb->src_port;
 283         sk->state    = TCP_CLOSE;
 284
 285         switch(scp->state) {
 286                 case DN_CI:
 287                 case DN_CD:
 288                         scp->state = DN_RJ;
 289                         break;
 290                 case DN_RUN:
 291                         sk->shutdown |= SHUTDOWN_MASK;
 292                         scp->state = DN_DN;
 293                         break;
 294                 case DN_DI:
 295                         scp->state = DN_DIC;
 296                         break;
 297         }
 298
 299         if (!sk->dead) {
 300                 if (sk->socket->state != SS_UNCONNECTED)
 301                         sk->socket->state = SS_DISCONNECTING;
 302                 sk->state_change(sk);
 303         }
 304
 305         dn_nsp_send_disc(sk, NSP_DISCCONF, NSP_REASON_DC, GFP_ATOMIC);
 306         scp->persist_fxn = dn_destroy_timer;
 307         scp->persist = dn_nsp_persist(sk);
 308
 309 out:
 310         kfree_skb(skb);
 311 }
 312
 313 /*
 314  * disc_conf messages are also called no_resources or no_link
 315  * messages depending upon the "reason" field.
 316  */
 317 static void dn_nsp_disc_conf(struct sock *sk, struct sk_buff *skb)
 318 {
 319         struct dn_scp *scp = &sk->protinfo.dn;
 320         unsigned short reason;
 321
 322         if (skb->len != 2)
 323                 goto out;
 324
 325         reason = dn_ntohs(*(__u16 *)skb->data);
 326
 327         sk->state = TCP_CLOSE;
 328
 329         switch(scp->state) {
 330                 case DN_CI:
 331                         scp->state = DN_NR;
 332                         break;
 333                 case DN_DR:
 334                         if (reason == NSP_REASON_DC)
 335                                 scp->state = DN_DRC;
 336                         if (reason == NSP_REASON_NL)
 337                                 scp->state = DN_CN;
 338                         break;
 339                 case DN_DI:
 340                         scp->state = DN_DIC;
 341                         break;
 342                 case DN_RUN:
 343                         sk->shutdown |= SHUTDOWN_MASK;
 344                 case DN_CC:
 345                         scp->state = DN_CN;
 346         }
 347
 348         if (!sk->dead) {
 349                 if (sk->socket->state != SS_UNCONNECTED)
 350                         sk->socket->state = SS_DISCONNECTING;
 351                 sk->state_change(sk);
 352         }
 353
 354         scp->persist_fxn = dn_destroy_timer;
 355         scp->persist = dn_nsp_persist(sk);
 356
 357 out:
 358         kfree_skb(skb);
 359 }
 360
 361 static void dn_nsp_linkservice(struct sock *sk, struct sk_buff *skb)
 362 {
 363         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 364         unsigned short segnum;
 365         unsigned char lsflags;
 366         char fcval;
 367
 368         if (skb->len != 4)
 369                 goto out;
 370
 371         cb->segnum = segnum = dn_ntohs(*(__u16 *)skb->data);
 372         skb_pull(skb, 2);
 373         lsflags = *(unsigned char *)skb->data;
 374         skb_pull(skb, 1);
 375         fcval = *(char *)skb->data;
 376
 377         if (lsflags & 0xf0)
 378                 goto out;
 379
 380         if (((sk->protinfo.dn.numoth_rcv + 1) & 0x0FFF) == (segnum & 0x0FFF)) {
 381                 sk->protinfo.dn.numoth_rcv += 1;
 382                 switch(lsflags & 0x03) {
 383                         case 0x00:
 384                                 break;
 385                         case 0x01:
 386                                 sk->protinfo.dn.flowrem_sw = DN_DONTSEND;
 387                                 break;
 388                         case 0x02:
 389                                 sk->protinfo.dn.flowrem_sw = DN_SEND;
 390                                 dn_nsp_output(sk);
 391                                 if (!sk->dead)
 392                                         sk->state_change(sk);
 393                 }
 394
 395         }
 396
 397         dn_nsp_send_oth_ack(sk);
 398
 399 out:
 400         kfree_skb(skb);
 401 }
 402
 403 /*
 404  * Copy of sock_queue_rcv_skb (from sock.h) without
 405  * bh_lock_sock() (its already held when this is called) which
 406  * also allows data and other data to be queued to a socket.
 407  */
 408 static __inline__ int dn_queue_skb(struct sock *sk, struct sk_buff *skb, int sig, struct sk_buff_head *queue)
 409 {
 410 #ifdef CONFIG_FILTER
 411         struct sk_filter *filter;
 412 #endif
 413
 414         /* Cast skb->rcvbuf to unsigned... It's pointless, but reduces
 415            number of warnings when compiling with -W --ANK
 416          */
 417         if (atomic_read(&sk->rmem_alloc) + skb->truesize >= (unsigned)sk->rcvbuf
 418 )
 419                 return -ENOMEM;
 420
 421 #ifdef CONFIG_FILTER
 422         if (sk->filter) {
 423                 int err = 0;
 424                 if ((filter = sk->filter) != NULL && sk_filter(skb, sk->filter))
 425                         err = -EPERM;  /* Toss packet */
 426                 if (err)
 427                         return err;
 428         }
 429 #endif /* CONFIG_FILTER */
 430
 431         skb_set_owner_r(skb, sk);
 432         skb_queue_tail(queue, skb);
 433
 434         /* This code only runs from BH or BH protected context.
 435          * Therefore the plain read_lock is ok here. -DaveM
 436          */
 437         read_lock(&sk->callback_lock);
 438         if (!sk->dead) {
 439                 struct socket *sock = sk->socket;
 440                 wake_up_interruptible(sk->sleep);
 441                 if (sock && sock->fasync_list &&
 442                     !test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
 443                         __kill_fasync(sock->fasync_list, sig,
 444                                     (sig == SIGURG) ? POLL_PRI : POLL_IN);
 445         }
 446         read_unlock(&sk->callback_lock);
 447
 448         return 0;
 449 }
 450
 451 static void dn_nsp_otherdata(struct sock *sk, struct sk_buff *skb)
 452 {
 453         struct dn_scp *scp = &sk->protinfo.dn;
 454         unsigned short segnum;
 455         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 456         int queued = 0;
 457
 458         if (skb->len < 2)
 459                 goto out;
 460
 461         cb->segnum = segnum = dn_ntohs(*(__u16 *)skb->data);
 462         skb_pull(skb, 2);
 463
 464         if (((sk->protinfo.dn.numoth_rcv + 1) & 0x0fff) == (segnum & 0x0fff)) {
 465
 466                 if (dn_queue_skb(sk, skb, SIGURG, &scp->other_receive_queue) == 0) {
 467                         sk->protinfo.dn.numoth_rcv++;
 468                         scp->other_report = 0;
 469                         queued = 1;
 470                 }
 471         }
 472
 473         dn_nsp_send_oth_ack(sk);
 474 out:
 475         if (!queued)
 476                 kfree_skb(skb);
 477 }
 478
 479 static void dn_nsp_data(struct sock *sk, struct sk_buff *skb)
 480 {
 481         int queued = 0;
 482         unsigned short segnum;
 483         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 484         struct dn_scp *scp = &sk->protinfo.dn;
 485
 486         if (skb->len < 2)
 487                 goto out;
 488
 489         cb->segnum = segnum = dn_ntohs(*(__u16 *)skb->data);
 490         skb_pull(skb, 2);
 491
 492         if (((sk->protinfo.dn.numdat_rcv + 1) & 0x0FFF) ==
 493                      (segnum & 0x0FFF)) {
 494
 495                 if (dn_queue_skb(sk, skb, SIGIO, &sk->receive_queue) == 0) {
 496                         sk->protinfo.dn.numdat_rcv++;
 497                         queued = 1;
 498                 }
 499
 500                 if ((scp->flowloc_sw == DN_SEND) && dn_congested(sk)) {
 501                         scp->flowloc_sw = DN_DONTSEND;
 502                         dn_nsp_send_lnk(sk, DN_DONTSEND);
 503                 }
 504         }
 505
 506         dn_nsp_send_data_ack(sk);
 507 out:
 508         if (!queued)
 509                 kfree_skb(skb);
 510 }
 511
 512 /*
 513  * If one of our conninit messages is returned, this function
 514  * deals with it. It puts the socket into the NO_COMMUNICATION
 515  * state.
 516  */
 517 static void dn_returned_conn_init(struct sock *sk, struct sk_buff *skb)
 518 {
 519         struct dn_scp *scp = &sk->protinfo.dn;
 520
 521         if (scp->state == DN_CI) {
 522                 scp->state = DN_NC;
 523                 sk->state = TCP_CLOSE;
 524                 if (!sk->dead)
 525                         sk->state_change(sk);
 526         }
 527
 528         kfree_skb(skb);
 529 }
 530
 531 static void dn_nsp_no_socket(struct sk_buff *skb)
 532 {
 533         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 534
 535         switch(cb->nsp_flags) {
 536                 case 0x28: /* Connect Confirm */
 537                         dn_nsp_return_disc(skb, NSP_DISCCONF, NSP_REASON_NL);
 538         }
 539
 540         kfree_skb(skb);
 541 }
 542
 543 static int dn_nsp_rx_packet(struct sk_buff *skb)
 544 {
 545         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 546         struct sock *sk = NULL;
 547         unsigned char *ptr = (unsigned char *)skb->data;
 548
 549         skb->h.raw    = skb->data;
 550         cb->nsp_flags = *ptr++;
 551
 552         if (decnet_debug_level & 2)
 553                 printk(KERN_DEBUG "dn_nsp_rx: Message type 0x%02x\n", (int)cb->nsp_flags);
 554
 555         if (skb->len < 2)
 556                 goto free_out;
 557
 558         if (cb->nsp_flags & 0x83)
 559                 goto free_out;
 560
 561         /*
 562          * Returned packets...
 563          * Swap src & dst and look up in the normal way.
 564          */
 565         if (cb->rt_flags & DN_RT_F_RTS) {
 566                 unsigned short tmp = cb->dst_port;
 567                 cb->dst_port = cb->src_port;
 568                 cb->src_port = tmp;
 569                 tmp = cb->dst;
 570                 cb->dst = cb->src;
 571                 cb->src = tmp;
 572                 sk = dn_find_by_skb(skb);
 573                 goto got_it;
 574         }
 575
 576         /*
 577          * Filter out conninits and useless packet types
 578          */
 579         if ((cb->nsp_flags & 0x0c) == 0x08) {
 580                 switch(cb->nsp_flags & 0x70) {
 581                         case 0x00: /* NOP */
 582                         case 0x70: /* Reserved */
 583                         case 0x50: /* Reserved, Phase II node init */
 584                                 goto free_out;
 585                         case 0x10:
 586                         case 0x60:
 587                                 sk = dn_find_listener(skb);
 588                                 goto got_it;
 589                 }
 590         }
 591
 592         if (skb->len < 3)
 593                 goto free_out;
 594
 595         /*
 596          * Grab the destination address.
 597          */
 598         cb->dst_port = *(unsigned short *)ptr;
 599         cb->src_port = 0;
 600         ptr += 2;
 601
 602         /*
 603          * If not a connack, grab the source address too.
 604          */
 605         if (skb->len >= 5) {
 606                 cb->src_port = *(unsigned short *)ptr;
 607                 ptr += 2;
 608                 skb_pull(skb, 5);
 609         }
 610
 611         /*
 612          * Find the socket to which this skb is destined.
 613          */
 614         sk = dn_find_by_skb(skb);
 615 got_it:
 616         if (sk != NULL) {
 617                 struct dn_scp *scp = &sk->protinfo.dn;
 618                 int ret;
 619
 620                 /* Reset backoff */
 621                 scp->nsp_rxtshift = 0;
 622
 623                 bh_lock_sock(sk);
 624                 ret = 0;
 625                 if (sk->lock.users == 0)
 626                         ret = dn_nsp_backlog_rcv(sk, skb);
 627                 else
 628                         sk_add_backlog(sk, skb);
 629                 bh_unlock_sock(sk);
 630                 sock_put(sk);
 631
 632                 return ret;
 633         }
 634
 635         dn_nsp_no_socket(skb);
 636         return 1;
 637
 638 free_out:
 639         kfree_skb(skb);
 640         return 0;
 641 }
 642
 643 int dn_nsp_rx(struct sk_buff *skb)
 644 {
 645         return NF_HOOK(PF_DECnet, NF_DN_LOCAL_IN, skb, skb->rx_dev, NULL, dn_nsp_rx_packet);
 646 }
 647
 648 /*
 649  * This is the main receive routine for sockets. It is called
 650  * from the above when the socket is not busy, and also from
 651  * sock_release() when there is a backlog queued up.
 652  */
 653 int dn_nsp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
 654 {
 655         struct dn_scp *scp = &sk->protinfo.dn;
 656         struct dn_skb_cb *cb = (struct dn_skb_cb *)skb->cb;
 657
 658         if (cb->rt_flags & DN_RT_F_RTS) {
 659                 dn_returned_conn_init(sk, skb);
 660                 return 0;
 661         }
 662
 663         /*
 664          * Control packet.
 665          */
 666         if ((cb->nsp_flags & 0x0c) == 0x08) {
 667                 /* printk(KERN_DEBUG "control type\n"); */
 668                 switch(cb->nsp_flags & 0x70) {
 669                         case 0x10:
 670                         case 0x60:
 671                                 dn_nsp_conn_init(sk, skb);
 672                                 break;
 673                         case 0x20:
 674                                 dn_nsp_conn_conf(sk, skb);
 675                                 break;
 676                         case 0x30:
 677                                 dn_nsp_disc_init(sk, skb);
 678                                 break;
 679                         case 0x40:
 680                                 dn_nsp_disc_conf(sk, skb);
 681                                 break;
 682                 }
 683
 684         } else if (cb->nsp_flags == 0x24) {
 685                 /*
 686                  * Special for connacks, 'cos they don't have
 687                  * ack data or ack otherdata info.
 688                  */
 689                 dn_nsp_conn_ack(sk, skb);
 690         } else {
 691                 int other = 1;
 692
 693                 /* both data and ack frames can kick a CC socket into RUN */
 694                 if ((scp->state == DN_CC) && !sk->dead) {
 695                         scp->state = DN_RUN;
 696                         sk->state = TCP_ESTABLISHED;
 697                         sk->state_change(sk);
 698                 }
 699
 700                 if ((cb->nsp_flags & 0x1c) == 0)
 701                         other = 0;
 702                 if (cb->nsp_flags == 0x04)
 703                         other = 0;
 704
 705                 /*
 706                  * Read out ack data here, this applies equally
 707                  * to data, other data, link serivce and both
 708                  * ack data and ack otherdata.
 709                  */
 710                 dn_process_ack(sk, skb, other);
 711
 712                 /*
 713                  * If we've some sort of data here then call a
 714                  * suitable routine for dealing with it, otherwise
 715                  * the packet is an ack and can be discarded.
 716                  */
 717                 if ((cb->nsp_flags & 0x0c) == 0) {
 718
 719                         if (scp->state != DN_RUN)
 720                                 goto free_out;
 721
 722                         switch(cb->nsp_flags) {
 723                                 case 0x10: /* LS */
 724                                         dn_nsp_linkservice(sk, skb);
 725                                         break;
 726                                 case 0x30: /* OD */
 727                                         dn_nsp_otherdata(sk, skb);
 728                                         break;
 729                                 default:
 730                                         dn_nsp_data(sk, skb);
 731                         }
 732
 733                 } else { /* Ack, chuck it out here */
 734 free_out:
 735                         kfree_skb(skb);
 736                 }
 737         }
 738
 739         return 0;
 740 }
 741