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iof-bird-daemon / proto / ospf / lsupd.c @ a7a7372a

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1
/*
2
 *        BIRD -- OSPF
3
 *
4
 *        (c) 2000--2004 Ondrej Filip <feela@network.cz>
5
 *        (c) 2009--2014 Ondrej Zajicek <santiago@crfreenet.org>
6
 *        (c) 2009--2014 CZ.NIC z.s.p.o.
7
 *
8
 *        Can be freely distributed and used under the terms of the GNU GPL.
9
 */
10

    
11
#include "ospf.h"
12

    
13

    
14
/*
15
struct ospf_lsupd_packet
16
{
17
  struct ospf_packet hdr;
18
  // union ospf_auth auth;
19

20
  u32 lsa_count;
21
  void lsas[];
22
};
23
*/
24

    
25

    
26
void
27
ospf_dump_lsahdr(struct ospf_proto *p, struct ospf_lsa_header *lsa_n)
28
{
29
  struct ospf_lsa_header lsa;
30
  u32 lsa_etype;
31

    
32
  lsa_ntoh_hdr(lsa_n, &lsa);
33
  lsa_etype = lsa_get_etype(&lsa, p);
34

    
35
  log(L_TRACE "%s:     LSA      Type: %04x, Id: %R, Rt: %R, Age: %u, Seq: %08x, Sum: %04x",
36
      p->p.name, lsa_etype, lsa.id, lsa.rt, lsa.age, lsa.sn, lsa.checksum);
37
}
38

    
39
void
40
ospf_dump_common(struct ospf_proto *p, struct ospf_packet *pkt)
41
{
42
  log(L_TRACE "%s:     length   %d", p->p.name, ntohs(pkt->length));
43
  log(L_TRACE "%s:     router   %R", p->p.name, ntohl(pkt->routerid));
44
}
45

    
46
static inline uint
47
ospf_lsupd_hdrlen(struct ospf_proto *p)
48
{
49
  return ospf_pkt_hdrlen(p) + 4; /* + u32 lsa count field */
50
}
51

    
52
static inline u32
53
ospf_lsupd_get_lsa_count(struct ospf_packet *pkt, uint hdrlen)
54
{
55
  u32 *c = ((void *) pkt) + hdrlen - 4;
56
  return ntohl(*c);
57
}
58

    
59
static inline void
60
ospf_lsupd_set_lsa_count(struct ospf_packet *pkt, uint hdrlen, u32 val)
61
{
62
  u32 *c = ((void *) pkt) + hdrlen - 4;
63
  *c = htonl(val);
64
}
65

    
66
static inline void
67
ospf_lsupd_body(struct ospf_proto *p, struct ospf_packet *pkt,
68
                uint *offset, uint *bound, uint *lsa_count)
69
{
70
  uint hlen = ospf_lsupd_hdrlen(p);
71
  *offset = hlen;
72
  *bound = ntohs(pkt->length) - sizeof(struct ospf_lsa_header);
73
  *lsa_count = ospf_lsupd_get_lsa_count(pkt, hlen);
74
}
75

    
76
static void
77
ospf_dump_lsupd(struct ospf_proto *p, struct ospf_packet *pkt)
78
{
79
  uint offset, bound, i, lsa_count, lsalen;
80

    
81
  ASSERT(pkt->type == LSUPD_P);
82
  ospf_dump_common(p, pkt);
83

    
84
  ospf_lsupd_body(p, pkt, &offset, &bound, &lsa_count);
85
  for (i = 0; i < lsa_count; i++)
86
  {
87
    if (offset > bound)
88
    {
89
      log(L_TRACE "%s:     LSA      invalid", p->p.name);
90
      return;
91
    }
92

    
93
    struct ospf_lsa_header *lsa = ((void *) pkt) + offset;
94
    ospf_dump_lsahdr(p, lsa);
95
    lsalen = ntohs(lsa->length);
96
    offset += lsalen;
97

    
98
    if (((lsalen % 4) != 0) || (lsalen <= sizeof(struct ospf_lsa_header)))
99
    {
100
      log(L_TRACE "%s:     LSA      invalid", p->p.name);
101
      return;
102
    }
103
  }
104
}
105

    
106

    
107
static inline void
108
ospf_lsa_lsrt_up(struct top_hash_entry *en, struct ospf_neighbor *n)
109
{
110
  struct top_hash_entry *ret = ospf_hash_get_entry(n->lsrth, en);
111

    
112
  if (!SNODE_VALID(ret))
113
  {
114
    en->ret_count++;
115
    s_add_tail(&n->lsrtl, SNODE ret);
116
  }
117

    
118
  ret->lsa = en->lsa;
119
  ret->lsa_body = LSA_BODY_DUMMY;
120
}
121

    
122
static inline int
123
ospf_lsa_lsrt_down(struct top_hash_entry *en, struct ospf_neighbor *n)
124
{
125
  struct top_hash_entry *ret = ospf_hash_find_entry(n->lsrth, en);
126

    
127
  if (ret)
128
  {
129
    en->ret_count--;
130
    s_rem_node(SNODE ret);
131
    ospf_hash_delete(n->lsrth, ret);
132
    return 1;
133
  }
134

    
135
  return 0;
136
}
137

    
138
void
139
ospf_add_flushed_to_lsrt(struct ospf_proto *p, struct ospf_neighbor *n)
140
{
141
  struct top_hash_entry *en;
142

    
143
  WALK_SLIST(en, p->lsal)
144
    if ((en->lsa.age == LSA_MAXAGE) && (en->lsa_body != NULL) &&
145
        lsa_flooding_allowed(en->lsa_type, en->domain, n->ifa))
146
      ospf_lsa_lsrt_up(en, n);
147
}
148

    
149

    
150
static void ospf_send_lsupd_to_ifa(struct ospf_proto *p, struct top_hash_entry *en, struct ospf_iface *ifa);
151

    
152

    
153
/**
154
 * ospf_flood_lsa - send LSA to the neighbors
155
 * @p: OSPF protocol instance
156
 * @en: LSA entry
157
 * @from: neighbor than sent this LSA (or NULL if LSA is local)
158
 *
159
 * return value - was the LSA flooded back?
160
 */
161
int
162
ospf_flood_lsa(struct ospf_proto *p, struct top_hash_entry *en, struct ospf_neighbor *from)
163
{
164
  struct ospf_iface *ifa;
165
  struct ospf_neighbor *n;
166

    
167
  /* RFC 2328 13.3 */
168

    
169
  int back = 0;
170
  WALK_LIST(ifa, p->iface_list)
171
  {
172
    if (ifa->stub)
173
      continue;
174

    
175
    if (! lsa_flooding_allowed(en->lsa_type, en->domain, ifa))
176
      continue;
177

    
178
    DBG("Wanted to flood LSA: Type: %u, ID: %R, RT: %R, SN: 0x%x, Age %u\n",
179
        hh->type, hh->id, hh->rt, hh->sn, hh->age);
180

    
181
    int used = 0;
182
    WALK_LIST(n, ifa->neigh_list)
183
    {
184
      /* 13.3 (1a) */
185
      if (n->state < NEIGHBOR_EXCHANGE)
186
        continue;
187

    
188
      /* 13.3 (1b) */
189
      if (n->state < NEIGHBOR_FULL)
190
      {
191
        struct top_hash_entry *req = ospf_hash_find_entry(n->lsrqh, en);
192
        if (req != NULL)
193
        {
194
          int cmp = lsa_comp(&en->lsa, &req->lsa);
195

    
196
          /* If same or newer, remove LSA from the link state request list */
197
          if (cmp > CMP_OLDER)
198
          {
199
            s_rem_node(SNODE req);
200
            ospf_hash_delete(n->lsrqh, req);
201
            n->want_lsreq = 1;
202

    
203
            if ((EMPTY_SLIST(n->lsrql)) && (n->state == NEIGHBOR_LOADING))
204
              ospf_neigh_sm(n, INM_LOADDONE);
205
          }
206

    
207
          /* If older or same, skip processing of this neighbor */
208
          if (cmp < CMP_NEWER)
209
            continue;
210
        }
211
      }
212

    
213
      /* 13.3 (1c) */
214
      if (n == from)
215
        continue;
216

    
217
      /* In OSPFv3, there should be check whether receiving router understand
218
         that type of LSA (for LSA types with U-bit == 0). But as we do not support
219
         any optional LSA types, this is not needed yet */
220

    
221
      /* 13.3 (1d) - add LSA to the link state retransmission list */
222
      ospf_lsa_lsrt_up(en, n);
223

    
224
      used = 1;
225
    }
226

    
227
    /* 13.3 (2) */
228
    if (!used)
229
      continue;
230

    
231
    if (from && (from->ifa == ifa))
232
    {
233
      /* 13.3 (3) */
234
      if ((from->rid == ifa->drid) || (from->rid == ifa->bdrid))
235
        continue;
236

    
237
      /* 13.3 (4) */
238
      if (ifa->state == OSPF_IS_BACKUP)
239
        continue;
240

    
241
      back = 1;
242
    }
243

    
244
    /* 13.3 (5) - finally flood the packet */
245
    ospf_send_lsupd_to_ifa(p, en, ifa);
246
  }
247

    
248
  return back;
249
}
250

    
251
static uint
252
ospf_prepare_lsupd(struct ospf_proto *p, struct ospf_iface *ifa,
253
                   struct top_hash_entry **lsa_list, uint lsa_count)
254
{
255
  struct ospf_packet *pkt;
256
  uint hlen, pos, i, maxsize;
257

    
258
  pkt = ospf_tx_buffer(ifa);
259
  hlen = ospf_lsupd_hdrlen(p);
260
  maxsize = ospf_pkt_maxsize(ifa);
261

    
262
  ospf_pkt_fill_hdr(ifa, pkt, LSUPD_P);
263
  pos = hlen;
264

    
265
  for (i = 0; i < lsa_count; i++)
266
  {
267
    struct top_hash_entry *en = lsa_list[i];
268
    uint len = en->lsa.length;
269

    
270
    if ((pos + len) > maxsize)
271
    {
272
      /* The packet if full, stop adding LSAs and sent it */
273
      if (i > 0)
274
        break;
275

    
276
      /* LSA is larger than MTU, check buffer size */
277
      if (ospf_iface_assure_bufsize(ifa, pos + len) < 0)
278
      {
279
        /* Cannot fit in a tx buffer, skip that */
280
        log(L_ERR "%s: LSA too large to send on %s (Type: %04x, Id: %R, Rt: %R)", 
281
            p->p.name, ifa->ifname, en->lsa_type, en->lsa.id, en->lsa.rt);
282
        break;
283
      }
284

    
285
      /* TX buffer could be reallocated */
286
      pkt = ospf_tx_buffer(ifa);
287
    }
288

    
289
    struct ospf_lsa_header *buf = ((void *) pkt) + pos;
290
    lsa_hton_hdr(&en->lsa, buf);
291
    lsa_hton_body(en->lsa_body, ((void *) buf) + sizeof(struct ospf_lsa_header),
292
                  len - sizeof(struct ospf_lsa_header));
293
    buf->age = htons(MIN(en->lsa.age + ifa->inftransdelay, LSA_MAXAGE));
294

    
295
    pos += len;
296
  }
297

    
298
  ospf_lsupd_set_lsa_count(pkt, hlen, i);
299
  pkt->length = htons(pos);
300

    
301
  return i;
302
}
303

    
304

    
305
static void
306
ospf_send_lsupd_to_ifa(struct ospf_proto *p, struct top_hash_entry *en, struct ospf_iface *ifa)
307
{
308
  uint c = ospf_prepare_lsupd(p, ifa, &en, 1);
309

    
310
  if (!c)        /* Too large LSA */
311
    return;
312

    
313
  OSPF_PACKET(ospf_dump_lsupd, ospf_tx_buffer(ifa),
314
              "LSUPD packet flooded via %s", ifa->ifname);
315

    
316
  if (ifa->type == OSPF_IT_BCAST)
317
  {
318
    if ((ifa->state == OSPF_IS_DR) || (ifa->state == OSPF_IS_BACKUP))
319
      ospf_send_to_all(ifa);
320
    else
321
      ospf_send_to_des(ifa);
322
  }
323
  else
324
    ospf_send_to_agt(ifa, NEIGHBOR_EXCHANGE);
325
}
326

    
327
int
328
ospf_send_lsupd(struct ospf_proto *p, struct top_hash_entry **lsa_list, uint lsa_count, struct ospf_neighbor *n)
329
{
330
  struct ospf_iface *ifa = n->ifa;
331
  uint i, c;
332

    
333
  for (i = 0; i < lsa_count; i += c)
334
  {
335
    c = ospf_prepare_lsupd(p, ifa, lsa_list + i, lsa_count - i);
336

    
337
    if (!c)        /* Too large LSA */
338
      { i++; continue; }
339

    
340
    OSPF_PACKET(ospf_dump_lsupd, ospf_tx_buffer(ifa),
341
                "LSUPD packet sent to %I via %s", n->ip, ifa->ifname);
342

    
343
    ospf_send_to(ifa, n->ip);
344
  }
345

    
346
  return lsa_count;
347
}
348

    
349
void
350
ospf_rxmt_lsupd(struct ospf_proto *p, struct ospf_neighbor *n)
351
{
352
  const uint max = 128;
353
  struct top_hash_entry *entries[max];
354
  struct top_hash_entry *ret, *nxt, *en;
355
  uint i = 0;
356

    
357
  WALK_SLIST_DELSAFE(ret, nxt, n->lsrtl)
358
  {
359
    if (i == max)
360
      break;
361

    
362
    en = ospf_hash_find_entry(p->gr, ret);
363
    if (!en)
364
    {
365
      /* Probably flushed LSA, this should not happen */
366
      log(L_WARN "%s: LSA disappeared (Type: %04x, Id: %R, Rt: %R)",
367
          p->p.name, ret->lsa_type, ret->lsa.id, ret->lsa.rt);
368

    
369
      s_rem_node(SNODE ret);
370
      ospf_hash_delete(n->lsrth, ret);
371

    
372
      continue;
373
    }
374

    
375
    entries[i] = en;
376
    i++;
377
  }
378

    
379
  ospf_send_lsupd(p, entries, i, n);
380
}
381

    
382

    
383
static inline int
384
ospf_addr_is_local(struct ospf_proto *p, struct ospf_area *oa, ip_addr ip)
385
{
386
  struct ospf_iface *ifa;
387
  WALK_LIST(ifa, p->iface_list)
388
    if ((ifa->oa == oa) && ifa->addr && ipa_equal(ifa->addr->ip, ip))
389
      return 1;
390

    
391
  return 0;
392
}
393

    
394
void
395
ospf_receive_lsupd(struct ospf_packet *pkt, struct ospf_iface *ifa,
396
                   struct ospf_neighbor *n)
397
{
398
  struct ospf_proto *p = ifa->oa->po;
399

    
400
  /* RFC 2328 13. */
401

    
402
  int skip_lsreq = 0;
403
  n->want_lsreq = 0;
404

    
405
  uint plen = ntohs(pkt->length);
406
  if (plen < (ospf_lsupd_hdrlen(p) + sizeof(struct ospf_lsa_header)))
407
  {
408
    log(L_ERR "OSPF: Bad LSUPD packet from %I - too short (%u B)", n->ip, plen);
409
    return;
410
  }
411

    
412
  OSPF_PACKET(ospf_dump_lsupd, pkt, "LSUPD packet received from %I via %s", n->ip, ifa->ifname);
413

    
414
  if (n->state < NEIGHBOR_EXCHANGE)
415
  {
416
    OSPF_TRACE(D_PACKETS, "Received lsupd in lesser state than EXCHANGE from (%I)", n->ip);
417
    return;
418
  }
419

    
420
  ospf_neigh_sm(n, INM_HELLOREC);        /* Questionable */
421

    
422
  uint offset, bound, i, lsa_count;
423
  ospf_lsupd_body(p, pkt, &offset, &bound, &lsa_count);
424

    
425
  for (i = 0; i < lsa_count; i++)
426
  {
427
    struct ospf_lsa_header lsa, *lsa_n;
428
    struct top_hash_entry *en;
429
    u32 lsa_len, lsa_type, lsa_domain;
430

    
431
    if (offset > bound)
432
    {
433
      log(L_WARN "%s: Received LSUPD from %I is too short", p->p.name, n->ip);
434
      ospf_neigh_sm(n, INM_BADLSREQ);
435
      return;
436
    }
437

    
438
    /* LSA header in network order */
439
    lsa_n = ((void *) pkt) + offset;
440
    lsa_len = ntohs(lsa_n->length);
441
    offset += lsa_len;
442
 
443
    if ((offset > plen) || ((lsa_len % 4) != 0) ||
444
        (lsa_len <= sizeof(struct ospf_lsa_header)))
445
    {
446
      log(L_WARN "%s: Received LSA from %I with bad length", p->p.name, n->ip);
447
      ospf_neigh_sm(n, INM_BADLSREQ);
448
      return;
449
    }
450

    
451
    /* RFC 2328 13. (1) - validate LSA checksum */
452
    u16 chsum = lsa_n->checksum;
453
    if (chsum != lsasum_check(lsa_n, NULL))
454
    {
455
      log(L_WARN "%s: Received LSA from %I with bad checksum: %x %x",
456
          p->p.name, n->ip, chsum, lsa_n->checksum);
457
      continue;
458
    }
459

    
460
    /* LSA header in host order */
461
    lsa_ntoh_hdr(lsa_n, &lsa);
462
    lsa_get_type_domain(&lsa, ifa, &lsa_type, &lsa_domain);
463

    
464
    DBG("Update Type: %04x, Id: %R, Rt: %R, Sn: 0x%08x, Age: %u, Sum: %u\n",
465
        lsa_type, lsa.id, lsa.rt, lsa.sn, lsa.age, lsa.checksum);
466

    
467
    /* RFC 2328 13. (2) */
468
    if (!lsa_type)
469
    {
470
      log(L_WARN "%s: Received unknown LSA type from %I", p->p.name, n->ip);
471
      continue;
472
    }
473

    
474
    /* RFC 5340 4.5.1 (2) and RFC 2328 13. (3) */
475
    if (!oa_is_ext(ifa->oa) && (LSA_SCOPE(lsa_type) == LSA_SCOPE_AS))
476
    {
477
      log(L_WARN "%s: Received LSA with AS scope in stub area from %I", p->p.name, n->ip);
478
      continue;
479
    }
480

    
481
    /* Errata 3746 to RFC 2328 - rt-summary-LSAs forbidden in stub areas */
482
    if (!oa_is_ext(ifa->oa) && (lsa_type == LSA_T_SUM_RT))
483
    {
484
      log(L_WARN "%s: Received rt-summary-LSA in stub area from %I", p->p.name, n->ip);
485
      continue;
486
    }
487

    
488
    /* RFC 5340 4.5.1 (3) */
489
    if (LSA_SCOPE(lsa_type) == LSA_SCOPE_RES)
490
    {
491
      log(L_WARN "%s: Received LSA with invalid scope from %I", p->p.name, n->ip);
492
      continue;
493
    }
494

    
495
    /* Find local copy of LSA in link state database */
496
    en = ospf_hash_find(p->gr, lsa_domain, lsa.id, lsa.rt, lsa_type);
497

    
498
#ifdef LOCAL_DEBUG
499
    if (en)
500
      DBG("I have Type: %04x, Id: %R, Rt: %R, Sn: 0x%08x, Age: %u, Sum: %u\n",
501
          en->lsa_type, en->lsa.id, en->lsa.rt, en->lsa.sn, en->lsa.age, en->lsa.checksum);
502
#endif
503

    
504
    /* 13. (4) - ignore maxage LSA if i have no local copy */
505
    if ((lsa.age == LSA_MAXAGE) && !en && (p->padj == 0))
506
    {
507
      /* 13.5. - schedule ACKs (tbl 19, case 5) */ 
508
      ospf_enqueue_lsack(n, lsa_n, ACKL_DIRECT);
509
      continue;
510
    }
511

    
512
    /* 13. (5) - received LSA is newer (or no local copy) */
513
    if (!en || (lsa_comp(&lsa, &en->lsa) == CMP_NEWER))
514
    {
515
      /* 13. (5a) - enforce minimum time between updates for received LSAs */
516
      /* We also use this to ratelimit reactions to received self-originated LSAs */
517
      if (en && ((now - en->inst_time) < MINLSARRIVAL))
518
      {
519
        OSPF_TRACE(D_EVENTS, "Skipping LSA received in less that MinLSArrival");
520
        skip_lsreq = 1;
521
        continue;
522
      }
523

    
524
      /* Copy and validate LSA body */
525
      int blen = lsa.length - sizeof(struct ospf_lsa_header);
526
      void *body = mb_alloc(p->p.pool, blen);
527
      lsa_ntoh_body(lsa_n + 1, body, blen);
528

    
529
      if (lsa_validate(&lsa, lsa_type, ospf_is_v2(p), body) == 0)
530
      {
531
        log(L_WARN "%s: Received invalid LSA from %I", p->p.name, n->ip);
532
        mb_free(body);
533
        continue;
534
      }
535

    
536
      /* 13. (5f) - handle self-originated LSAs, see also 13.4. */
537
      if ((lsa.rt == p->router_id) ||
538
          (ospf_is_v2(p) && (lsa_type == LSA_T_NET) && ospf_addr_is_local(p, ifa->oa, ipa_from_u32(lsa.id))))
539
      {
540
        OSPF_TRACE(D_EVENTS, "Received unexpected self-originated LSA");
541
        ospf_advance_lsa(p, en, &lsa, lsa_type, lsa_domain, body);
542
        continue;
543
      }
544

    
545
      /* 13. (5c) - remove old LSA from all retransmission lists */
546
      /*
547
       * We only need to remove it from the retransmission list of the neighbor
548
       * that send us the new LSA. The old LSA is automatically replaced in
549
       * retransmission lists by the new LSA.
550
       */
551
      if (en)
552
        ospf_lsa_lsrt_down(en, n);
553

    
554
#if 0
555
      /*
556
       * Old code for removing LSA from all retransmission lists. Must be done
557
       * before (5b), otherwise it also removes the new entries from (5b).
558
       */
559
      struct ospf_iface *ifi;
560
      struct ospf_neighbor *ni;
561

562
      WALK_LIST(ifi, p->iface_list)
563
        WALK_LIST(ni, ifi->neigh_list)
564
        if (ni->state > NEIGHBOR_EXSTART)
565
          ospf_lsa_lsrt_down(en, ni);
566
#endif
567

    
568
      /* 13. (5d) - install new LSA into database */
569
      en = ospf_install_lsa(p, &lsa, lsa_type, lsa_domain, body);
570

    
571
      /* RFC 5340 4.4.3 Events 6+7 - new Link LSA received */
572
      if (lsa_type == LSA_T_LINK)
573
        ospf_notify_net_lsa(ifa);
574

    
575
      /* 13. (5b) - flood new LSA */
576
      int flood_back = ospf_flood_lsa(p, en, n);
577

    
578
      /* 13.5. - schedule ACKs (tbl 19, cases 1+2) */ 
579
      if (! flood_back)
580
        if ((ifa->state != OSPF_IS_BACKUP) || (n->rid == ifa->drid))
581
          ospf_enqueue_lsack(n, lsa_n, ACKL_DELAY);
582

    
583
      /* FIXME: remove LSA entry if it is LSA_MAXAGE and it is possible? */
584

    
585
      continue;
586
    }
587

    
588
    /* FIXME pg145 (6) */
589

    
590
    /* 13. (7) - received LSA is same */
591
    if (lsa_comp(&lsa, &en->lsa) == CMP_SAME)
592
    {
593
      /* Duplicate LSA, treat as implicit ACK */
594
      int implicit_ack = ospf_lsa_lsrt_down(en, n);
595

    
596
      /* 13.5. - schedule ACKs (tbl 19, cases 3+4) */ 
597
      if (implicit_ack)
598
      {
599
        if ((ifa->state == OSPF_IS_BACKUP) && (n->rid == ifa->drid))
600
          ospf_enqueue_lsack(n, lsa_n, ACKL_DELAY);
601
      }
602
      else
603
        ospf_enqueue_lsack(n, lsa_n, ACKL_DIRECT);
604

    
605
      skip_lsreq = 1;
606
      continue;
607
    }
608

    
609
    /* 13. (8) - received LSA is older */
610
    {
611
      /* Seqnum is wrapping, wait until it is flushed */
612
      if ((en->lsa.age == LSA_MAXAGE) && (en->lsa.sn == LSA_MAXSEQNO))
613
        continue;
614

    
615
      /* Send newer local copy back to neighbor */
616
      /* FIXME - check for MinLSArrival ? */
617
      ospf_send_lsupd(p, &en, 1, n);
618
    }
619
  }
620

    
621
  /* Send direct LSACKs */
622
  ospf_send_lsack(p, n, ACKL_DIRECT);
623

    
624
  /*
625
   * In loading state, we should ask for another batch of LSAs. This is only
626
   * vaguely mentioned in RFC 2328. We send a new LSREQ only if the current
627
   * LSUPD actually removed some entries from LSA request list (want_lsreq) and
628
   * did not contain duplicate or early LSAs (skip_lsreq). The first condition
629
   * prevents endless floods, the second condition helps with flow control.
630
   */
631
  if ((n->state == NEIGHBOR_LOADING) && n->want_lsreq && !skip_lsreq)
632
    ospf_send_lsreq(p, n);
633
}
634