bird/nest/neighbor.c
2010-04-28 00:39:57 +02:00

330 lines
8.4 KiB
C

/*
* BIRD -- Neighbor Cache
*
* (c) 1998--2000 Martin Mares <mj@ucw.cz>
*
* 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.
*
* Active entries represent known neighbors and are stored in a hash
* table (to allow fast retrieval based on the IP address of the node) and
* two linked lists: one global and one per-interface (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 enqueued in a special list which is walked
* whenever an interface changes its state to up.
*
* 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/resource.h"
#define NEIGH_HASH_SIZE 256
static slab *neigh_slab;
static list sticky_neigh_list, neigh_hash_table[NEIGH_HASH_SIZE];
static inline unsigned int
neigh_hash(struct proto *p, ip_addr *a)
{
return (p->hash_key ^ ipa_hash(*a)) & (NEIGH_HASH_SIZE-1);
}
static int
if_connected(ip_addr *a, struct iface *i) /* -1=error, 1=match, 0=no match */
{
struct ifa *b;
if (!(i->flags & IF_UP))
return -1;
WALK_LIST(b, i->addrs)
{
if (ipa_equal(*a, b->ip))
return SCOPE_HOST;
if (b->flags & IA_UNNUMBERED)
{
if (ipa_equal(*a, b->opposite))
return b->scope;
}
else
{
if (ipa_in_net(*a, b->prefix, b->pxlen))
{
#ifndef IPV6
if ((b->pxlen < (BITS_PER_IP_ADDRESS - 1)) &&
(ipa_equal(*a, b->prefix) || /* Network address */
ipa_equal(*a, b->brd))) /* Broadcast */
return -1;
#endif
return b->scope;
}
}
}
return -1;
}
/**
* neigh_find - find or create a neighbor entry.
* @p: protocol which asks for the entry.
* @a: pointer to IP address of the node to be searched for.
* @flags: 0 or %NEF_STICKY if you want to create a sticky entry.
*
* Search the neighbor cache for a node with given IP address. If
* it's 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, unsigned flags)
{
return neigh_find2(p, a, NULL, flags);
}
neighbor *
neigh_find2(struct proto *p, ip_addr *a, struct iface *ifa, unsigned flags)
{
neighbor *n;
int class, scope = -1; ;
unsigned int h = neigh_hash(p, a);
struct iface *i;
WALK_LIST(n, neigh_hash_table[h]) /* Search the cache */
if (n->proto == p && ipa_equal(*a, n->addr) && (!ifa || (ifa == n->iface)))
return n;
class = ipa_classify(*a);
if (class < 0) /* Invalid address */
return NULL;
if (((class & IADDR_SCOPE_MASK) == SCOPE_HOST) ||
(((class & IADDR_SCOPE_MASK) == SCOPE_LINK) && (ifa == NULL)) ||
!(class & IADDR_HOST))
return NULL; /* Bad scope or a somecast */
if (ifa)
{
scope = if_connected(a, ifa);
if ((scope < 0) && (flags & NEF_ONLINK))
scope = class & IADDR_SCOPE_MASK;
}
else
WALK_LIST(i, iface_list)
if ((scope = if_connected(a, i)) >= 0)
{
ifa = i;
break;
}
/* scope < 0 means i don't know neighbor */
/* scope >= 0 implies ifa != NULL */
if ((scope < 0) && !(flags & NEF_STICKY))
return NULL;
n = sl_alloc(neigh_slab);
n->addr = *a;
if (scope >= 0)
{
add_tail(&neigh_hash_table[h], &n->n);
add_tail(&ifa->neighbors, &n->if_n);
}
else
{
/* sticky flag does not work for link-local neighbors;
fortunately, we don't use this combination */
add_tail(&sticky_neigh_list, &n->n);
ifa = NULL;
scope = 0;
}
n->iface = ifa;
n->proto = p;
n->data = NULL;
n->aux = 0;
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 ", n, n->addr);
if (n->iface)
debug("%s ", n->iface->name);
else
debug("[] ");
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");
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");
WALK_LIST(n, sticky_neigh_list)
neigh_dump(n);
for(i=0; i<NEIGH_HASH_SIZE; i++)
WALK_LIST(n, neigh_hash_table[i])
neigh_dump(n);
debug("\n");
}
/**
* 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, *next;
int scope;
WALK_LIST_DELSAFE(n, next, sticky_neigh_list)
if ((scope = if_connected(&n->addr, i)) >= 0)
{
n->iface = i;
n->scope = scope;
add_tail(&i->neighbors, &n->if_n);
rem_node(&n->n);
add_tail(&neigh_hash_table[neigh_hash(n->proto, &n->addr)], &n->n);
DBG("Waking up sticky neighbor %I\n", n->addr);
if (n->proto->neigh_notify && n->proto->core_state != FS_FLUSHING)
n->proto->neigh_notify(n);
}
}
/**
* 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 entries belonging to neighbors connected to this interface
* to be flushed.
*/
void
neigh_if_down(struct iface *i)
{
node *x, *y;
WALK_LIST_DELSAFE(x, y, i->neighbors)
{
neighbor *n = SKIP_BACK(neighbor, if_n, x);
DBG("Flushing neighbor %I on %s\n", n->addr, i->name);
rem_node(&n->if_n);
n->iface = NULL;
if (n->proto->neigh_notify && n->proto->core_state != FS_FLUSHING)
n->proto->neigh_notify(n);
rem_node(&n->n);
if (n->flags & NEF_STICKY)
add_tail(&sticky_neigh_list, &n->n);
else
sl_free(neigh_slab, n);
}
}
static inline void
neigh_prune_one(neighbor *n)
{
if (n->proto->proto_state != PS_DOWN)
return;
rem_node(&n->n);
if (n->iface)
rem_node(&n->if_n);
sl_free(neigh_slab, 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);
WALK_LIST_DELSAFE(n, m, sticky_neigh_list)
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)
{
int i;
neigh_slab = sl_new(if_pool, sizeof(neighbor));
init_list(&sticky_neigh_list);
for(i=0; i<NEIGH_HASH_SIZE; i++)
init_list(&neigh_hash_table[i]);
}