1: /*
2: * BIRD -- Neighbor Cache
3: *
4: * (c) 1998--2000 Martin Mares <mj@ucw.cz>
5: * (c) 2008--2018 Ondrej Zajicek <santiago@crfreenet.org>
6: * (c) 2008--2018 CZ.NIC z.s.p.o.
7: *
8: * Can be freely distributed and used under the terms of the GNU GPL.
9: */
10:
11: /**
12: * DOC: Neighbor cache
13: *
14: * Most routing protocols need to associate their internal state data with
15: * neighboring routers, check whether an address given as the next hop attribute
16: * of a route is really an address of a directly connected host and which
17: * interface is it connected through. Also, they often need to be notified when
18: * a neighbor ceases to exist or when their long awaited neighbor becomes
19: * connected. The neighbor cache is there to solve all these problems.
20: *
21: * The neighbor cache maintains a collection of neighbor entries. Each entry
22: * represents one IP address corresponding to either our directly connected
23: * neighbor or our own end of the link (when the scope of the address is set to
24: * %SCOPE_HOST) together with per-neighbor data belonging to a single protocol.
25: * A neighbor entry may be bound to a specific interface, which is required for
26: * link-local IP addresses and optional for global IP addresses.
27: *
28: * Neighbor cache entries are stored in a hash table, which is indexed by triple
29: * (protocol, IP, requested-iface), so if both regular and iface-bound neighbors
30: * are requested, they are represented by two neighbor cache entries. Active
31: * entries are also linked in per-interface list (allowing quick processing of
32: * interface change events). Inactive entries exist only when the protocol has
33: * explicitly requested it via the %NEF_STICKY flag because it wishes to be
34: * notified when the node will again become a neighbor. Such entries are instead
35: * linked in a special list, which is walked whenever an interface changes its
36: * state to up. Neighbor entry VRF association is implied by respective
37: * protocol.
38: *
39: * Besides the already mentioned %NEF_STICKY flag, there is also %NEF_ONLINK,
40: * which specifies that neighbor should be considered reachable on given iface
41: * regardless of associated address ranges, and %NEF_IFACE, which represents
42: * pseudo-neighbor entry for whole interface (and uses %IPA_NONE IP address).
43: *
44: * When a neighbor event occurs (a neighbor gets disconnected or a sticky
45: * inactive neighbor becomes connected), the protocol hook neigh_notify() is
46: * called to advertise the change.
47: */
48:
49: #undef LOCAL_DEBUG
50:
51: #include "nest/bird.h"
52: #include "nest/iface.h"
53: #include "nest/protocol.h"
54: #include "lib/hash.h"
55: #include "lib/resource.h"
56:
57: #define NEIGH_HASH_SIZE 256
58: #define NEIGH_HASH_OFFSET 24
59:
60: static slab *neigh_slab;
61: static list neigh_hash_table[NEIGH_HASH_SIZE], sticky_neigh_list;
62:
63: static inline uint
64: neigh_hash(struct proto *p, ip_addr a, struct iface *i)
65: {
66: return (p->hash_key ^ ipa_hash(a) ^ ptr_hash(i)) >> NEIGH_HASH_OFFSET;
67: }
68:
69: static int
70: if_connected(ip_addr a, struct iface *i, struct ifa **ap, uint flags)
71: {
72: struct ifa *b;
73:
74: /* Handle iface pseudo-neighbors */
75: if (flags & NEF_IFACE)
76: return *ap = NULL, (i->flags & IF_UP) ? SCOPE_HOST : -1;
77:
78: /* Host addresses match even if iface is down */
79: WALK_LIST(b, i->addrs)
80: if (ipa_equal(a, b->ip))
81: return *ap = b, SCOPE_HOST;
82:
83: /* Rest do not match if iface is down */
84: if (!(i->flags & IF_UP))
85: return *ap = NULL, -1;
86:
87: /* Regular neighbors */
88: WALK_LIST(b, i->addrs)
89: {
90: if (b->flags & IA_PEER)
91: {
92: if (ipa_equal(a, b->opposite))
93: return *ap = b, b->scope;
94: }
95: else
96: {
97: if (ipa_in_netX(a, &b->prefix))
98: {
99: /* Do not allow IPv4 network and broadcast addresses */
100: if (ipa_is_ip4(a) &&
101: (net_pxlen(&b->prefix) < (IP4_MAX_PREFIX_LENGTH - 1)) &&
102: (ipa_equal(a, net_prefix(&b->prefix)) || /* Network address */
103: ipa_equal(a, b->brd))) /* Broadcast */
104: return *ap = NULL, -1;
105:
106: return *ap = b, b->scope;
107: }
108: }
109: }
110:
111: /* Handle ONLINK flag */
112: if (flags & NEF_ONLINK)
113: return *ap = NULL, ipa_classify(a) & IADDR_SCOPE_MASK;
114:
115: return *ap = NULL, -1;
116: }
117:
118: static inline int
119: if_connected_any(ip_addr a, struct iface *vrf, uint vrf_set, struct iface **iface, struct ifa **addr, uint flags)
120: {
121: struct iface *i;
122: struct ifa *b;
123: int s, scope = -1;
124:
125: *iface = NULL;
126: *addr = NULL;
127:
128: /* Get first match, but prefer SCOPE_HOST to other matches */
129: WALK_LIST(i, iface_list)
130: if ((!vrf_set || vrf == i->master) && ((s = if_connected(a, i, &b, flags)) >= 0))
131: if ((scope < 0) || ((scope > SCOPE_HOST) && (s == SCOPE_HOST)))
132: {
133: *iface = i;
134: *addr = b;
135: scope = s;
136: }
137:
138: return scope;
139: }
140:
141: /**
142: * neigh_find - find or create a neighbor entry
143: * @p: protocol which asks for the entry
144: * @a: IP address of the node to be searched for
145: * @iface: optionally bound neighbor to this iface (may be NULL)
146: * @flags: %NEF_STICKY for sticky entry, %NEF_ONLINK for onlink entry
147: *
148: * Search the neighbor cache for a node with given IP address. Iface can be
149: * specified for link-local addresses or for cases, where neighbor is expected
150: * on given interface. If it is found, a pointer to the neighbor entry is
151: * returned. If no such entry exists and the node is directly connected on one
152: * of our active interfaces, a new entry is created and returned to the caller
153: * with protocol-dependent fields initialized to zero. If the node is not
154: * connected directly or *@a is not a valid unicast IP address, neigh_find()
155: * returns %NULL.
156: */
157: neighbor *
158: neigh_find(struct proto *p, ip_addr a, struct iface *iface, uint flags)
159: {
160: neighbor *n;
161: int class, scope = -1;
162: uint h = neigh_hash(p, a, iface);
163: struct iface *ifreq = iface;
164: struct ifa *addr = NULL;
165:
166: WALK_LIST(n, neigh_hash_table[h]) /* Search the cache */
167: if ((n->proto == p) && ipa_equal(n->addr, a) && (n->ifreq == iface))
168: return n;
169:
170: if (flags & NEF_IFACE)
171: {
172: if (ipa_nonzero(a) || !iface)
173: return NULL;
174: }
175: else
176: {
177: class = ipa_classify(a);
178: if (class < 0) /* Invalid address */
179: return NULL;
180: if (((class & IADDR_SCOPE_MASK) == SCOPE_HOST) ||
181: (((class & IADDR_SCOPE_MASK) == SCOPE_LINK) && !iface) ||
182: !(class & IADDR_HOST))
183: return NULL; /* Bad scope or a somecast */
184: }
185:
186: if ((flags & NEF_ONLINK) && !iface)
187: return NULL;
188:
189: if (iface)
190: {
191: scope = if_connected(a, iface, &addr, flags);
192: iface = (scope < 0) ? NULL : iface;
193: }
194: else
195: scope = if_connected_any(a, p->vrf, p->vrf_set, &iface, &addr, flags);
196:
197: /* scope < 0 means i don't know neighbor */
198: /* scope >= 0 <=> iface != NULL */
199:
200: if ((scope < 0) && !(flags & NEF_STICKY))
201: return NULL;
202:
203: n = sl_alloc(neigh_slab);
204: memset(n, 0, sizeof(neighbor));
205:
206: add_tail(&neigh_hash_table[h], &n->n);
207: add_tail((scope >= 0) ? &iface->neighbors : &sticky_neigh_list, &n->if_n);
208: n->addr = a;
209: n->ifa = addr;
210: n->iface = iface;
211: n->ifreq = ifreq;
212: n->proto = p;
213: n->flags = flags;
214: n->scope = scope;
215:
216: return n;
217: }
218:
219: /**
220: * neigh_dump - dump specified neighbor entry.
221: * @n: the entry to dump
222: *
223: * This functions dumps the contents of a given neighbor entry to debug output.
224: */
225: void
226: neigh_dump(neighbor *n)
227: {
228: debug("%p %I %s %s ", n, n->addr,
229: n->iface ? n->iface->name : "[]",
230: n->ifreq ? n->ifreq->name : "[]");
231: debug("%s %p %08x scope %s", n->proto->name, n->data, n->aux, ip_scope_text(n->scope));
232: if (n->flags & NEF_STICKY)
233: debug(" STICKY");
234: if (n->flags & NEF_ONLINK)
235: debug(" ONLINK");
236: debug("\n");
237: }
238:
239: /**
240: * neigh_dump_all - dump all neighbor entries.
241: *
242: * This function dumps the contents of the neighbor cache to debug output.
243: */
244: void
245: neigh_dump_all(void)
246: {
247: neighbor *n;
248: int i;
249:
250: debug("Known neighbors:\n");
251: for(i=0; i<NEIGH_HASH_SIZE; i++)
252: WALK_LIST(n, neigh_hash_table[i])
253: neigh_dump(n);
254: debug("\n");
255: }
256:
257: static inline void
258: neigh_notify(neighbor *n)
259: {
260: if (n->proto->neigh_notify && (n->proto->proto_state != PS_STOP))
261: n->proto->neigh_notify(n);
262: }
263:
264: static void
265: neigh_up(neighbor *n, struct iface *i, struct ifa *a, int scope)
266: {
267: DBG("Waking up sticky neighbor %I\n", n->addr);
268: n->iface = i;
269: n->ifa = a;
270: n->scope = scope;
271:
272: rem_node(&n->if_n);
273: add_tail(&i->neighbors, &n->if_n);
274:
275: neigh_notify(n);
276: }
277:
278: static void
279: neigh_down(neighbor *n)
280: {
281: DBG("Flushing neighbor %I on %s\n", n->addr, n->iface->name);
282: n->iface = NULL;
283: n->ifa = NULL;
284: n->scope = -1;
285:
286: rem_node(&n->if_n);
287: add_tail(&sticky_neigh_list, &n->if_n);
288:
289: neigh_notify(n);
290: }
291:
292: static inline void
293: neigh_free(neighbor *n)
294: {
295: rem_node(&n->n);
296: rem_node(&n->if_n);
297: sl_free(neigh_slab, n);
298: }
299:
300: /**
301: * neigh_update: update neighbor entry w.r.t. change on specific iface
302: * @n: neighbor to update
303: * @iface: changed iface
304: *
305: * The function recalculates state of the neighbor entry @n assuming that only
306: * the interface @iface may changed its state or addresses. Then, appropriate
307: * actions are executed (the neighbor goes up, down, up-down, or just notified).
308: */
309: void
310: neigh_update(neighbor *n, struct iface *iface)
311: {
312: struct proto *p = n->proto;
313: struct ifa *ifa = NULL;
314: int scope = -1;
315:
316: /* Iface-bound neighbors ignore other ifaces */
317: if (n->ifreq && (n->ifreq != iface))
318: return;
319:
320: /* VRF-bound neighbors ignore changes in other VRFs */
321: if (p->vrf_set && (p->vrf != iface->master))
322: return;
323:
324: scope = if_connected(n->addr, iface, &ifa, n->flags);
325:
326: /* When neighbor is going down, try to respawn it on other ifaces */
327: if ((scope < 0) && (n->scope >= 0) && !n->ifreq && (n->flags & NEF_STICKY))
328: scope = if_connected_any(n->addr, p->vrf, p->vrf_set, &iface, &ifa, n->flags);
329:
330: /* No change or minor change - ignore or notify */
331: if ((scope == n->scope) && (iface == n->iface))
332: {
333: if (ifa != n->ifa)
334: {
335: n->ifa = ifa;
336: neigh_notify(n);
337: }
338:
339: return;
340: }
341:
342: /* Major change - going down and/or going up */
343:
344: if (n->scope >= 0)
345: neigh_down(n);
346:
347: if ((n->scope < 0) && !(n->flags & NEF_STICKY))
348: {
349: neigh_free(n);
350: return;
351: }
352:
353: if (scope >= 0)
354: neigh_up(n, iface, ifa, scope);
355: }
356:
357:
358: /**
359: * neigh_if_up: notify neighbor cache about interface up event
360: * @i: interface in question
361: *
362: * Tell the neighbor cache that a new interface became up.
363: *
364: * The neighbor cache wakes up all inactive sticky neighbors with
365: * addresses belonging to prefixes of the interface @i.
366: */
367: void
368: neigh_if_up(struct iface *i)
369: {
370: neighbor *n;
371: node *x, *y;
372:
373: WALK_LIST2_DELSAFE(n, x, y, sticky_neigh_list, if_n)
374: neigh_update(n, i);
375: }
376:
377: /**
378: * neigh_if_down - notify neighbor cache about interface down event
379: * @i: the interface in question
380: *
381: * Notify the neighbor cache that an interface has ceased to exist.
382: *
383: * It causes all neighbors connected to this interface to be updated or removed.
384: */
385: void
386: neigh_if_down(struct iface *i)
387: {
388: neighbor *n;
389: node *x, *y;
390:
391: WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n)
392: neigh_update(n, i);
393: }
394:
395: /**
396: * neigh_if_link - notify neighbor cache about interface link change
397: * @i: the interface in question
398: *
399: * Notify the neighbor cache that an interface changed link state. All owners of
400: * neighbor entries connected to this interface are notified.
401: */
402: void
403: neigh_if_link(struct iface *i)
404: {
405: neighbor *n;
406: node *x, *y;
407:
408: WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n)
409: neigh_notify(n);
410: }
411:
412: /**
413: * neigh_ifa_update: notify neighbor cache about interface address add or remove event
414: * @a: interface address in question
415: *
416: * Tell the neighbor cache that an address was added or removed.
417: *
418: * The neighbor cache wakes up all inactive sticky neighbors with
419: * addresses belonging to prefixes of the interface belonging to @ifa
420: * and causes all unreachable neighbors to be flushed.
421: */
422: void
423: neigh_ifa_update(struct ifa *a)
424: {
425: struct iface *i = a->iface;
426: neighbor *n;
427: node *x, *y;
428:
429: /* Update all neighbors whose scope has changed */
430: WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n)
431: neigh_update(n, i);
432:
433: /* Wake up all sticky neighbors that are reachable now */
434: WALK_LIST2_DELSAFE(n, x, y, sticky_neigh_list, if_n)
435: neigh_update(n, i);
436: }
437:
438: static inline void
439: neigh_prune_one(neighbor *n)
440: {
441: if (n->proto->proto_state != PS_DOWN)
442: return;
443:
444: neigh_free(n);
445: }
446:
447: /**
448: * neigh_prune - prune neighbor cache
449: *
450: * neigh_prune() examines all neighbor entries cached and removes those
451: * corresponding to inactive protocols. It's called whenever a protocol
452: * is shut down to get rid of all its heritage.
453: */
454: void
455: neigh_prune(void)
456: {
457: neighbor *n;
458: node *m;
459: int i;
460:
461: DBG("Pruning neighbors\n");
462: for(i=0; i<NEIGH_HASH_SIZE; i++)
463: WALK_LIST_DELSAFE(n, m, neigh_hash_table[i])
464: neigh_prune_one(n);
465: }
466:
467: /**
468: * neigh_init - initialize the neighbor cache.
469: * @if_pool: resource pool to be used for neighbor entries.
470: *
471: * This function is called during BIRD startup to initialize
472: * the neighbor cache module.
473: */
474: void
475: neigh_init(pool *if_pool)
476: {
477: neigh_slab = sl_new(if_pool, sizeof(neighbor));
478:
479: for(int i = 0; i < NEIGH_HASH_SIZE; i++)
480: init_list(&neigh_hash_table[i]);
481:
482: init_list(&sticky_neigh_list);
483: }
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