/* * BIRD -- Neighbor Cache * * (c) 1998--2000 Martin Mares <mj@ucw.cz> * (c) 2008--2018 Ondrej Zajicek <santiago@crfreenet.org> * (c) 2008--2018 CZ.NIC z.s.p.o. * * Can be freely distributed and used under the terms of the GNU GPL. */ /** * DOC: Neighbor cache * * Most routing protocols need to associate their internal state data with * neighboring routers, check whether an address given as the next hop attribute * of a route is really an address of a directly connected host and which * interface is it connected through. Also, they often need to be notified when * a neighbor ceases to exist or when their long awaited neighbor becomes * connected. The neighbor cache is there to solve all these problems. * * The neighbor cache maintains a collection of neighbor entries. Each entry * represents one IP address corresponding to either our directly connected * neighbor or our own end of the link (when the scope of the address is set to * %SCOPE_HOST) together with per-neighbor data belonging to a single protocol. * A neighbor entry may be bound to a specific interface, which is required for * link-local IP addresses and optional for global IP addresses. * * Neighbor cache entries are stored in a hash table, which is indexed by triple * (protocol, IP, requested-iface), so if both regular and iface-bound neighbors * are requested, they are represented by two neighbor cache entries. Active * entries are also linked in per-interface list (allowing quick processing of * interface change events). Inactive entries exist only when the protocol has * explicitly requested it via the %NEF_STICKY flag because it wishes to be * notified when the node will again become a neighbor. Such entries are instead * linked in a special list, which is walked whenever an interface changes its * state to up. Neighbor entry VRF association is implied by respective * protocol. * * Besides the already mentioned %NEF_STICKY flag, there is also %NEF_ONLINK, * which specifies that neighbor should be considered reachable on given iface * regardless of associated address ranges, and %NEF_IFACE, which represents * pseudo-neighbor entry for whole interface (and uses %IPA_NONE IP address). * * When a neighbor event occurs (a neighbor gets disconnected or a sticky * inactive neighbor becomes connected), the protocol hook neigh_notify() is * called to advertise the change. */ #undef LOCAL_DEBUG #include "nest/bird.h" #include "nest/iface.h" #include "nest/protocol.h" #include "lib/hash.h" #include "lib/resource.h" #define NEIGH_HASH_SIZE 256 #define NEIGH_HASH_OFFSET 24 static slab *neigh_slab; static list neigh_hash_table[NEIGH_HASH_SIZE], sticky_neigh_list; static inline uint neigh_hash(struct proto *p, ip_addr a, struct iface *i) { return (p->hash_key ^ ipa_hash(a) ^ ptr_hash(i)) >> NEIGH_HASH_OFFSET; } static int if_connected(ip_addr a, struct iface *i, struct ifa **ap, uint flags) { struct ifa *b; /* Handle iface pseudo-neighbors */ if (flags & NEF_IFACE) return *ap = NULL, (i->flags & IF_UP) ? SCOPE_HOST : -1; /* Host addresses match even if iface is down */ WALK_LIST(b, i->addrs) if (ipa_equal(a, b->ip)) return *ap = b, SCOPE_HOST; /* Rest do not match if iface is down */ if (!(i->flags & IF_UP)) return *ap = NULL, -1; /* Regular neighbors */ WALK_LIST(b, i->addrs) { if (b->flags & IA_PEER) { if (ipa_equal(a, b->opposite)) return *ap = b, b->scope; } else { if (ipa_in_netX(a, &b->prefix)) { /* Do not allow IPv4 network and broadcast addresses */ if (ipa_is_ip4(a) && (net_pxlen(&b->prefix) < (IP4_MAX_PREFIX_LENGTH - 1)) && (ipa_equal(a, net_prefix(&b->prefix)) || /* Network address */ ipa_equal(a, b->brd))) /* Broadcast */ return *ap = NULL, -1; return *ap = b, b->scope; } } } /* Handle ONLINK flag */ if (flags & NEF_ONLINK) return *ap = NULL, ipa_classify(a) & IADDR_SCOPE_MASK; return *ap = NULL, -1; } static inline int if_connected_any(ip_addr a, struct iface *vrf, struct iface **iface, struct ifa **addr, uint flags) { struct iface *i; struct ifa *b; int s, scope = -1; *iface = NULL; *addr = NULL; /* Get first match, but prefer SCOPE_HOST to other matches */ WALK_LIST(i, iface_list) if ((!vrf || vrf == i->master) && ((s = if_connected(a, i, &b, flags)) >= 0)) if ((scope < 0) || ((scope > SCOPE_HOST) && (s == SCOPE_HOST))) { *iface = i; *addr = b; scope = s; } return scope; } /** * neigh_find - find or create a neighbor entry * @p: protocol which asks for the entry * @a: IP address of the node to be searched for * @iface: optionally bound neighbor to this iface (may be NULL) * @flags: %NEF_STICKY for sticky entry, %NEF_ONLINK for onlink entry * * Search the neighbor cache for a node with given IP address. Iface can be * specified for link-local addresses or for cases, where neighbor is expected * on given interface. If it is found, a pointer to the neighbor entry is * returned. If no such entry exists and the node is directly connected on one * of our active interfaces, a new entry is created and returned to the caller * with protocol-dependent fields initialized to zero. If the node is not * connected directly or *@a is not a valid unicast IP address, neigh_find() * returns %NULL. */ neighbor * neigh_find(struct proto *p, ip_addr a, struct iface *iface, uint flags) { neighbor *n; int class, scope = -1; uint h = neigh_hash(p, a, iface); struct iface *ifreq = iface; struct ifa *addr = NULL; WALK_LIST(n, neigh_hash_table[h]) /* Search the cache */ if ((n->proto == p) && ipa_equal(n->addr, a) && (n->ifreq == iface)) return n; if (flags & NEF_IFACE) { if (ipa_nonzero(a) || !iface) return NULL; } else { class = ipa_classify(a); if (class < 0) /* Invalid address */ return NULL; if (((class & IADDR_SCOPE_MASK) == SCOPE_HOST) || (((class & IADDR_SCOPE_MASK) == SCOPE_LINK) && !iface) || !(class & IADDR_HOST)) return NULL; /* Bad scope or a somecast */ } if ((flags & NEF_ONLINK) && !iface) return NULL; if (iface) { scope = if_connected(a, iface, &addr, flags); iface = (scope < 0) ? NULL : iface; } else scope = if_connected_any(a, p->vrf, &iface, &addr, flags); /* scope < 0 means i don't know neighbor */ /* scope >= 0 <=> iface != NULL */ if ((scope < 0) && !(flags & NEF_STICKY)) return NULL; n = sl_alloc(neigh_slab); memset(n, 0, sizeof(neighbor)); add_tail(&neigh_hash_table[h], &n->n); add_tail((scope >= 0) ? &iface->neighbors : &sticky_neigh_list, &n->if_n); n->addr = a; n->ifa = addr; n->iface = iface; n->ifreq = ifreq; n->proto = p; n->flags = flags; n->scope = scope; return n; } /** * neigh_dump - dump specified neighbor entry. * @n: the entry to dump * * This functions dumps the contents of a given neighbor entry to debug output. */ void neigh_dump(neighbor *n) { debug("%p %I %s %s ", n, n->addr, n->iface ? n->iface->name : "[]", n->ifreq ? n->ifreq->name : "[]"); debug("%s %p %08x scope %s", n->proto->name, n->data, n->aux, ip_scope_text(n->scope)); if (n->flags & NEF_STICKY) debug(" STICKY"); if (n->flags & NEF_ONLINK) debug(" ONLINK"); debug("\n"); } /** * neigh_dump_all - dump all neighbor entries. * * This function dumps the contents of the neighbor cache to debug output. */ void neigh_dump_all(void) { neighbor *n; int i; debug("Known neighbors:\n"); for(i=0; i<NEIGH_HASH_SIZE; i++) WALK_LIST(n, neigh_hash_table[i]) neigh_dump(n); debug("\n"); } static inline void neigh_notify(neighbor *n) { if (n->proto->neigh_notify && (n->proto->proto_state != PS_STOP)) n->proto->neigh_notify(n); } static void neigh_up(neighbor *n, struct iface *i, struct ifa *a, int scope) { DBG("Waking up sticky neighbor %I\n", n->addr); n->iface = i; n->ifa = a; n->scope = scope; rem_node(&n->if_n); add_tail(&i->neighbors, &n->if_n); neigh_notify(n); } static void neigh_down(neighbor *n) { DBG("Flushing neighbor %I on %s\n", n->addr, n->iface->name); n->iface = NULL; n->ifa = NULL; n->scope = -1; rem_node(&n->if_n); add_tail(&sticky_neigh_list, &n->if_n); neigh_notify(n); } static inline void neigh_free(neighbor *n) { rem_node(&n->n); rem_node(&n->if_n); sl_free(neigh_slab, n); } /** * neigh_update: update neighbor entry w.r.t. change on specific iface * @n: neighbor to update * @iface: changed iface * * The function recalculates state of the neighbor entry @n assuming that only * the interface @iface may changed its state or addresses. Then, appropriate * actions are executed (the neighbor goes up, down, up-down, or just notified). */ void neigh_update(neighbor *n, struct iface *iface) { struct ifa *ifa = NULL; int scope = -1; /* Iface-bound neighbors ignore other ifaces */ if (n->ifreq && (n->ifreq != iface)) return; /* VRF-bound neighbors ignore changes in other VRFs */ if (n->proto->vrf && (n->proto->vrf != iface->master)) return; scope = if_connected(n->addr, iface, &ifa, n->flags); /* When neighbor is going down, try to respawn it on other ifaces */ if ((scope < 0) && (n->scope >= 0) && !n->ifreq && (n->flags & NEF_STICKY)) scope = if_connected_any(n->addr, n->proto->vrf, &iface, &ifa, n->flags); /* No change or minor change - ignore or notify */ if ((scope == n->scope) && (iface == n->iface)) { if (ifa != n->ifa) { n->ifa = ifa; neigh_notify(n); } return; } /* Major change - going down and/or going up */ if (n->scope >= 0) neigh_down(n); if ((n->scope < 0) && !(n->flags & NEF_STICKY)) { neigh_free(n); return; } if (scope >= 0) neigh_up(n, iface, ifa, scope); } /** * neigh_if_up: notify neighbor cache about interface up event * @i: interface in question * * Tell the neighbor cache that a new interface became up. * * The neighbor cache wakes up all inactive sticky neighbors with * addresses belonging to prefixes of the interface @i. */ void neigh_if_up(struct iface *i) { neighbor *n; node *x, *y; WALK_LIST2_DELSAFE(n, x, y, sticky_neigh_list, if_n) neigh_update(n, i); } /** * neigh_if_down - notify neighbor cache about interface down event * @i: the interface in question * * Notify the neighbor cache that an interface has ceased to exist. * * It causes all neighbors connected to this interface to be updated or removed. */ void neigh_if_down(struct iface *i) { neighbor *n; node *x, *y; WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n) neigh_update(n, i); } /** * neigh_if_link - notify neighbor cache about interface link change * @i: the interface in question * * Notify the neighbor cache that an interface changed link state. All owners of * neighbor entries connected to this interface are notified. */ void neigh_if_link(struct iface *i) { neighbor *n; node *x, *y; WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n) neigh_notify(n); } /** * neigh_ifa_update: notify neighbor cache about interface address add or remove event * @a: interface address in question * * Tell the neighbor cache that an address was added or removed. * * The neighbor cache wakes up all inactive sticky neighbors with * addresses belonging to prefixes of the interface belonging to @ifa * and causes all unreachable neighbors to be flushed. */ void neigh_ifa_update(struct ifa *a) { struct iface *i = a->iface; neighbor *n; node *x, *y; /* Update all neighbors whose scope has changed */ WALK_LIST2_DELSAFE(n, x, y, i->neighbors, if_n) neigh_update(n, i); /* Wake up all sticky neighbors that are reachable now */ WALK_LIST2_DELSAFE(n, x, y, sticky_neigh_list, if_n) neigh_update(n, i); } static inline void neigh_prune_one(neighbor *n) { if (n->proto->proto_state != PS_DOWN) return; neigh_free(n); } /** * neigh_prune - prune neighbor cache * * neigh_prune() examines all neighbor entries cached and removes those * corresponding to inactive protocols. It's called whenever a protocol * is shut down to get rid of all its heritage. */ void neigh_prune(void) { neighbor *n; node *m; int i; DBG("Pruning neighbors\n"); for(i=0; i<NEIGH_HASH_SIZE; i++) WALK_LIST_DELSAFE(n, m, neigh_hash_table[i]) neigh_prune_one(n); } /** * neigh_init - initialize the neighbor cache. * @if_pool: resource pool to be used for neighbor entries. * * This function is called during BIRD startup to initialize * the neighbor cache module. */ void neigh_init(pool *if_pool) { neigh_slab = sl_new(if_pool, sizeof(neighbor)); for(int i = 0; i < NEIGH_HASH_SIZE; i++) init_list(&neigh_hash_table[i]); init_list(&sticky_neigh_list); }