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9f4908fe78
Actually much simpler than expected.
421 lines
10 KiB
C
421 lines
10 KiB
C
/*
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* BIRD -- Neighbor Cache
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*
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* (c) 1998--2000 Martin Mares <mj@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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/**
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* DOC: Neighbor cache
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*
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* Most routing protocols need to associate their internal state data with
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* neighboring routers, check whether an address given as the next hop
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* attribute of a route is really an address of a directly connected host
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* and which interface is it connected through. Also, they often need to
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* be notified when a neighbor ceases to exist or when their long awaited
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* neighbor becomes connected. The neighbor cache is there to solve all
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* these problems.
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*
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* The neighbor cache maintains a collection of neighbor entries. Each
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* entry represents one IP address corresponding to either our directly
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* connected neighbor or our own end of the link (when the scope of the
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* address is set to %SCOPE_HOST) together with per-neighbor data belonging to a
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* single protocol.
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*
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* Active entries represent known neighbors and are stored in a hash
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* table (to allow fast retrieval based on the IP address of the node) and
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* two linked lists: one global and one per-interface (allowing quick
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* processing of interface change events). Inactive entries exist only
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* when the protocol has explicitly requested it via the %NEF_STICKY
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* flag because it wishes to be notified when the node will again become
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* a neighbor. Such entries are enqueued in a special list which is walked
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* whenever an interface changes its state to up. Neighbor entry VRF
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* association is implied by respective protocol.
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*
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* When a neighbor event occurs (a neighbor gets disconnected or a sticky
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* inactive neighbor becomes connected), the protocol hook neigh_notify()
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* is called to advertise the change.
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*/
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#undef LOCAL_DEBUG
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#include "nest/bird.h"
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#include "nest/iface.h"
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#include "nest/protocol.h"
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#include "lib/resource.h"
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#define NEIGH_HASH_SIZE 256
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static slab *neigh_slab;
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static list sticky_neigh_list, neigh_hash_table[NEIGH_HASH_SIZE];
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static inline uint
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neigh_hash(struct proto *p, ip_addr *a)
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{
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return (p->hash_key ^ ipa_hash(*a)) & (NEIGH_HASH_SIZE-1);
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}
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static int
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if_connected(ip_addr *a, struct iface *i, struct ifa **ap)
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{
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struct ifa *b;
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if (!(i->flags & IF_UP))
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{
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*ap = NULL;
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return -1;
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}
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WALK_LIST(b, i->addrs)
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{
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*ap = b;
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if (ipa_equal(*a, b->ip))
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return SCOPE_HOST;
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if (b->flags & IA_PEER)
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{
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if (ipa_equal(*a, b->opposite))
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return b->scope;
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}
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else
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{
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if (ipa_in_net(*a, b->prefix, b->pxlen))
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{
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#ifndef IPV6
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if ((b->pxlen < (BITS_PER_IP_ADDRESS - 1)) &&
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(ipa_equal(*a, b->prefix) || /* Network address */
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ipa_equal(*a, b->brd))) /* Broadcast */
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{
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*ap = NULL;
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return -1;
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}
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#endif
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return b->scope;
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}
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}
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}
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*ap = NULL;
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return -1;
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}
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/**
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* neigh_find - find or create a neighbor entry.
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* @p: protocol which asks for the entry.
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* @a: pointer to IP address of the node to be searched for.
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* @flags: 0 or %NEF_STICKY if you want to create a sticky entry.
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*
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* Search the neighbor cache for a node with given IP address. If
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* it's found, a pointer to the neighbor entry is returned. If no
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* such entry exists and the node is directly connected on
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* one of our active interfaces, a new entry is created and returned
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* to the caller with protocol-dependent fields initialized to zero.
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* If the node is not connected directly or *@a is not a valid unicast
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* IP address, neigh_find() returns %NULL.
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*/
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neighbor *
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neigh_find(struct proto *p, ip_addr *a, unsigned flags)
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{
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return neigh_find2(p, a, NULL, flags);
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}
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neighbor *
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neigh_find2(struct proto *p, ip_addr *a, struct iface *ifa, unsigned flags)
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{
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neighbor *n;
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int class, scope = -1;
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uint h = neigh_hash(p, a);
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struct iface *i;
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struct ifa *addr;
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WALK_LIST(n, neigh_hash_table[h]) /* Search the cache */
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if (n->proto == p && ipa_equal(*a, n->addr) && (!ifa || (ifa == n->iface)))
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return n;
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class = ipa_classify(*a);
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if (class < 0) /* Invalid address */
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return NULL;
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if (((class & IADDR_SCOPE_MASK) == SCOPE_HOST) ||
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(((class & IADDR_SCOPE_MASK) == SCOPE_LINK) && (ifa == NULL)) ||
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!(class & IADDR_HOST))
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return NULL; /* Bad scope or a somecast */
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if (ifa)
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{
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scope = if_connected(a, ifa, &addr);
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flags |= NEF_BIND;
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if ((scope < 0) && (flags & NEF_ONLINK))
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scope = class & IADDR_SCOPE_MASK;
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}
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else
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WALK_LIST(i, iface_list)
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if ((!p->vrf || p->vrf == i->master) &&
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((scope = if_connected(a, i, &addr)) >= 0))
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{
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ifa = i;
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break;
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}
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/* scope < 0 means i don't know neighbor */
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/* scope >= 0 implies ifa != NULL */
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if ((scope < 0) && !(flags & NEF_STICKY))
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return NULL;
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n = sl_alloc(neigh_slab);
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n->addr = *a;
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if (scope >= 0)
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{
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add_tail(&neigh_hash_table[h], &n->n);
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add_tail(&ifa->neighbors, &n->if_n);
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}
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else
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{
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add_tail(&sticky_neigh_list, &n->n);
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scope = -1;
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}
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n->iface = ifa;
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n->ifa = addr;
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n->proto = p;
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n->data = NULL;
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n->aux = 0;
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n->flags = flags;
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n->scope = scope;
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return n;
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}
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/**
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* neigh_dump - dump specified neighbor entry.
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* @n: the entry to dump
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*
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* This functions dumps the contents of a given neighbor entry
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* to debug output.
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*/
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void
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neigh_dump(neighbor *n)
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{
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debug("%p %I ", n, n->addr);
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if (n->iface)
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debug("%s ", n->iface->name);
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else
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debug("[] ");
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debug("%s %p %08x scope %s", n->proto->name, n->data, n->aux, ip_scope_text(n->scope));
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if (n->flags & NEF_STICKY)
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debug(" STICKY");
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debug("\n");
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}
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/**
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* neigh_dump_all - dump all neighbor entries.
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*
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* This function dumps the contents of the neighbor cache to
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* debug output.
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*/
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void
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neigh_dump_all(void)
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{
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neighbor *n;
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int i;
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debug("Known neighbors:\n");
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WALK_LIST(n, sticky_neigh_list)
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neigh_dump(n);
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for(i=0; i<NEIGH_HASH_SIZE; i++)
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WALK_LIST(n, neigh_hash_table[i])
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neigh_dump(n);
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debug("\n");
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}
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static void
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neigh_up(neighbor *n, struct iface *i, int scope, struct ifa *a)
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{
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n->iface = i;
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n->ifa = a;
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n->scope = scope;
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add_tail(&i->neighbors, &n->if_n);
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rem_node(&n->n);
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add_tail(&neigh_hash_table[neigh_hash(n->proto, &n->addr)], &n->n);
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DBG("Waking up sticky neighbor %I\n", n->addr);
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if (n->proto->neigh_notify && n->proto->core_state != FS_FLUSHING)
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n->proto->neigh_notify(n);
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}
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static void
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neigh_down(neighbor *n)
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{
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DBG("Flushing neighbor %I on %s\n", n->addr, n->iface->name);
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rem_node(&n->if_n);
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if (! (n->flags & NEF_BIND))
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n->iface = NULL;
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n->ifa = NULL;
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n->scope = -1;
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if (n->proto->neigh_notify && n->proto->core_state != FS_FLUSHING)
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n->proto->neigh_notify(n);
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rem_node(&n->n);
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if (n->flags & NEF_STICKY)
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{
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add_tail(&sticky_neigh_list, &n->n);
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/* Respawn neighbor if there is another matching prefix */
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struct iface *i;
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struct ifa *a;
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int scope;
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if (!n->iface)
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WALK_LIST(i, iface_list)
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if ((scope = if_connected(&n->addr, i, &a)) >= 0)
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{
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neigh_up(n, i, scope, a);
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return;
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}
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}
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else
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sl_free(neigh_slab, n);
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}
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/**
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* neigh_if_up: notify neighbor cache about interface up event
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* @i: interface in question
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*
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* Tell the neighbor cache that a new interface became up.
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*
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* The neighbor cache wakes up all inactive sticky neighbors with
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* addresses belonging to prefixes of the interface @i.
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*/
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void
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neigh_if_up(struct iface *i)
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{
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struct ifa *a;
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neighbor *n, *next;
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int scope;
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WALK_LIST_DELSAFE(n, next, sticky_neigh_list)
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if ((!n->iface || n->iface == i) &&
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((scope = if_connected(&n->addr, i, &a)) >= 0))
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neigh_up(n, i, scope, a);
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}
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/**
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* neigh_if_down - notify neighbor cache about interface down event
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* @i: the interface in question
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*
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* Notify the neighbor cache that an interface has ceased to exist.
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*
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* It causes all entries belonging to neighbors connected to this interface
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* to be flushed.
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*/
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void
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neigh_if_down(struct iface *i)
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{
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node *x, *y;
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WALK_LIST_DELSAFE(x, y, i->neighbors)
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neigh_down(SKIP_BACK(neighbor, if_n, x));
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}
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/**
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* neigh_if_link - notify neighbor cache about interface link change
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* @i: the interface in question
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*
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* Notify the neighbor cache that an interface changed link state.
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* All owners of neighbor entries connected to this interface are
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* notified.
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*/
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void
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neigh_if_link(struct iface *i)
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{
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node *x, *y;
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WALK_LIST_DELSAFE(x, y, i->neighbors)
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{
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neighbor *n = SKIP_BACK(neighbor, if_n, x);
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if (n->proto->neigh_notify && n->proto->core_state != FS_FLUSHING)
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n->proto->neigh_notify(n);
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}
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}
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/**
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* neigh_ifa_update: notify neighbor cache about interface address add or remove event
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* @a: interface address in question
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*
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* Tell the neighbor cache that an address was added or removed.
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*
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* The neighbor cache wakes up all inactive sticky neighbors with
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* addresses belonging to prefixes of the interface belonging to @ifa
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* and causes all unreachable neighbors to be flushed.
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*/
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void
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neigh_ifa_update(struct ifa *a)
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{
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struct iface *i = a->iface;
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node *x, *y;
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/* Remove all neighbors whose scope has changed */
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WALK_LIST_DELSAFE(x, y, i->neighbors)
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{
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struct ifa *aa;
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neighbor *n = SKIP_BACK(neighbor, if_n, x);
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if (if_connected(&n->addr, i, &aa) != n->scope)
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neigh_down(n);
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}
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/* Wake up all sticky neighbors that are reachable now */
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neigh_if_up(i);
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}
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static inline void
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neigh_prune_one(neighbor *n)
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{
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if (n->proto->proto_state != PS_DOWN)
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return;
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rem_node(&n->n);
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if (n->scope >= 0)
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rem_node(&n->if_n);
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sl_free(neigh_slab, n);
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}
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/**
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* neigh_prune - prune neighbor cache
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*
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* neigh_prune() examines all neighbor entries cached and removes those
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* corresponding to inactive protocols. It's called whenever a protocol
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* is shut down to get rid of all its heritage.
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*/
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void
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neigh_prune(void)
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{
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neighbor *n;
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node *m;
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int i;
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DBG("Pruning neighbors\n");
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for(i=0; i<NEIGH_HASH_SIZE; i++)
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WALK_LIST_DELSAFE(n, m, neigh_hash_table[i])
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neigh_prune_one(n);
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WALK_LIST_DELSAFE(n, m, sticky_neigh_list)
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neigh_prune_one(n);
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}
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/**
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* neigh_init - initialize the neighbor cache.
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* @if_pool: resource pool to be used for neighbor entries.
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*
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* This function is called during BIRD startup to initialize
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* the neighbor cache module.
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*/
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void
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neigh_init(pool *if_pool)
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{
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int i;
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neigh_slab = sl_new(if_pool, sizeof(neighbor));
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init_list(&sticky_neigh_list);
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for(i=0; i<NEIGH_HASH_SIZE; i++)
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init_list(&neigh_hash_table[i]);
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}
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