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bird/nest/rt-fib.c
Ondrej Zajicek (work) fe9f1a6ded Initial commit on integrated BIRD 
New data types net_addr and variants (in lib/net.h) describing
network addresses (prefix/pxlen). Modifications of FIB structures
to handle these data types and changing everything to use these
data types instead of prefix/pxlen pairs where possible.

The commit is WiP, some protocols are not yet updated (BGP, Kernel),
and the code contains some temporary scaffolding.

Comments are welcome.
2015-11-05 12:48:52 +01:00

660 lines
14 KiB
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/*
* BIRD -- Forwarding Information Base -- Data Structures
*
* (c) 1998--2000 Martin Mares <mj@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
/**
* DOC: Forwarding Information Base
*
* FIB is a data structure designed for storage of routes indexed by their
* network prefixes. It supports insertion, deletion, searching by prefix,
* `routing' (in CIDR sense, that is searching for a longest prefix matching
* a given IP address) and (which makes the structure very tricky to implement)
* asynchronous reading, that is enumerating the contents of a FIB while other
* modules add, modify or remove entries.
*
* Internally, each FIB is represented as a collection of nodes of type &fib_node
* indexed using a sophisticated hashing mechanism.
* We use two-stage hashing where we calculate a 16-bit primary hash key independent
* on hash table size and then we just divide the primary keys modulo table size
* to get a real hash key used for determining the bucket containing the node.
* The lists of nodes in each bucket are sorted according to the primary hash
* key, hence if we keep the total number of buckets to be a power of two,
* re-hashing of the structure keeps the relative order of the nodes.
*
* To get the asynchronous reading consistent over node deletions, we need to
* keep a list of readers for each node. When a node gets deleted, its readers
* are automatically moved to the next node in the table.
*
* Basic FIB operations are performed by functions defined by this module,
* enumerating of FIB contents is accomplished by using the FIB_WALK() macro
* or FIB_ITERATE_START() if you want to do it asynchronously.
*/
#undef LOCAL_DEBUG
#include "nest/bird.h"
#include "nest/route.h"
#include "lib/string.h"
#define HASH_DEF_ORDER 10
#define HASH_HI_MARK *4
#define HASH_HI_STEP 2
#define HASH_HI_MAX 16 /* Must be at most 16 */
#define HASH_LO_MARK /5
#define HASH_LO_STEP 2
#define HASH_LO_MIN 10
static inline void * fib_node_to_user(struct fib *f, struct fib_node *e)
{ return (void *) ((char *) e - f->node_offset); }
static inline struct fib_node * fib_user_to_node(struct fib *f, void *e)
{ return (void *) ((char *) e + f->node_offset); }
static void
fib_ht_alloc(struct fib *f)
{
f->hash_size = 1 << f->hash_order;
f->hash_shift = 16 - f->hash_order;
if (f->hash_order > HASH_HI_MAX - HASH_HI_STEP)
f->entries_max = ~0;
else
f->entries_max = f->hash_size HASH_HI_MARK;
if (f->hash_order < HASH_LO_MIN + HASH_LO_STEP)
f->entries_min = 0;
else
f->entries_min = f->hash_size HASH_LO_MARK;
DBG("Allocating FIB hash of order %d: %d entries, %d low, %d high\n",
f->hash_order, f->hash_size, f->entries_min, f->entries_max);
f->hash_table = mb_alloc(f->fib_pool, f->hash_size * sizeof(struct fib_node *));
}
static inline void
fib_ht_free(struct fib_node **h)
{
mb_free(h);
}
static u32
fib_hash(struct fib *f, net_addr *a);
/**
* fib_init - initialize a new FIB
* @f: the FIB to be initialized (the structure itself being allocated by the caller)
* @p: pool to allocate the nodes in
* @node_size: node size to be used (each node consists of a standard header &fib_node
* followed by user data)
* @hash_order: initial hash order (a binary logarithm of hash table size), 0 to use default order
* (recommended)
* @init: pointer a function to be called to initialize a newly created node
*
* This function initializes a newly allocated FIB and prepares it for use.
*/
void
fib_init(struct fib *f, pool *p, uint addr_type, uint node_size, uint node_offset, uint hash_order, fib_init_fn init)
{
uint addr_length = net_addr_length[addr_type];
if (!hash_order)
hash_order = HASH_DEF_ORDER;
f->fib_pool = p;
f->fib_slab = addr_length ? sl_new(p, node_size + addr_length) : NULL;
f->addr_type = addr_type;
f->node_size = node_size;
f->node_offset = node_offset;
f->hash_order = hash_order;
fib_ht_alloc(f);
bzero(f->hash_table, f->hash_size * sizeof(struct fib_node *));
f->entries = 0;
f->entries_min = 0;
f->init = init;
}
static void
fib_rehash(struct fib *f, int step)
{
unsigned old, new, oldn, newn, ni, nh;
struct fib_node **n, *e, *x, **t, **m, **h;
old = f->hash_order;
oldn = f->hash_size;
new = old + step;
m = h = f->hash_table;
DBG("Re-hashing FIB from order %d to %d\n", old, new);
f->hash_order = new;
fib_ht_alloc(f);
t = n = f->hash_table;
newn = f->hash_size;
ni = 0;
while (oldn--)
{
x = *h++;
while (e = x)
{
x = e->next;
nh = fib_hash(f, e->addr);
while (nh > ni)
{
*t = NULL;
ni++;
t = ++n;
}
*t = e;
t = &e->next;
}
}
while (ni < newn)
{
*t = NULL;
ni++;
t = ++n;
}
fib_ht_free(m);
}
#define CAST(t) (net_addr_##t *)
#define FIB_HASH(f,a,t) (net_hash_##t(CAST(t) a) >> f->hash_shift)
#define FIB_FIND(f,a,t) \
({ \
struct fib_node *e = f->hash_table[FIB_HASH(f, a, t)]; \
while (e && !net_equal_##t(CAST(t) e->addr, CAST(t) a)) \
e = e->next; \
fib_node_to_user(f, e); \
})
#define FIB_INSERT(f,a,e,t) \
({ \
u32 h = net_hash_##t(CAST(t) a); \
struct fib_node **ee = f->hash_table + (h >> f->hash_shift); \
struct fib_node *g; \
\
while ((g = *ee) && (net_hash_##t(CAST(t) g->addr) < h)) \
ee = &g->next; \
\
net_copy_##t(CAST(t) e->addr, CAST(t) a); \
e->next = *ee; \
*ee = e; \
})
static u32
fib_hash(struct fib *f, net_addr *a)
{
switch (f->addr_type)
{
case NET_IP4: return FIB_HASH(f, a, ip4);
case NET_IP6: return FIB_HASH(f, a, ip6);
case NET_VPN4: return FIB_HASH(f, a, vpn4);
case NET_VPN6: return FIB_HASH(f, a, vpn6);
default: bug("invalid type");
}
}
void *
fib_find(struct fib *f, net_addr *a)
{
ASSERT(f->addr_type == a->type);
switch (f->addr_type)
{
case NET_IP4: return FIB_FIND(f, a, ip4);
case NET_IP6: return FIB_FIND(f, a, ip6);
case NET_VPN4: return FIB_FIND(f, a, vpn4);
case NET_VPN6: return FIB_FIND(f, a, vpn6);
default: bug("invalid type");
}
}
static void
fib_insert(struct fib *f, net_addr *a, struct fib_node *e)
{
switch (f->addr_type)
{
case NET_IP4: FIB_INSERT(f, a, e, ip4); return;
case NET_IP6: FIB_INSERT(f, a, e, ip6); return;
case NET_VPN4: FIB_INSERT(f, a, e, vpn4); return;
case NET_VPN6: FIB_INSERT(f, a, e, vpn6); return;
default: bug("invalid type");
}
}
/**
* fib_find - search for FIB node by prefix
* @f: FIB to search in
* @a: pointer to IP address of the prefix
* @len: prefix length
*
* Search for a FIB node corresponding to the given prefix, return
* a pointer to it or %NULL if no such node exists.
*/
/*
void *
fib_find(struct fib *f, net_addr *a)
{
struct fib_node *e = f->hash_table[fib_hash(f, a)];
while (e && (e->pxlen != len || !ipa_equal(*a, e->prefix)))
e = e->next;
return e;
}
*/
/**
* fib_get - find or create a FIB node
* @f: FIB to work with
* @a: pointer to IP address of the prefix
* @len: prefix length
*
* Search for a FIB node corresponding to the given prefix and
* return a pointer to it. If no such node exists, create it.
*/
void *
fib_get(struct fib *f, net_addr *a)
{
char *b = fib_find(f, a);
if (b)
return b;
if (f->fib_slab)
b = sl_alloc(f->fib_slab);
else
b = mb_alloc(f->fib_pool, f->node_size + a->length);
struct fib_node *e = (void *) (b + f->node_offset);
e->readers = NULL;
e->flags = 0;
e->uid = 0;
fib_insert(f, a, e);
memset(b, 0, f->node_offset);
if (f->init)
f->init(b);
if (f->entries++ > f->entries_max)
fib_rehash(f, HASH_HI_STEP);
return b;
}
/**
* fib_route - CIDR routing lookup
* @f: FIB to search in
* @a: pointer to IP address of the prefix
* @len: prefix length
*
* Search for a FIB node with longest prefix matching the given
* network, that is a node which a CIDR router would use for routing
* that network.
*/
/*
void *
fib_route(struct fib *f, ip_addr a, int len)
{
ip_addr a0;
void *t;
while (len >= 0)
{
a0 = ipa_and(a, ipa_mkmask(len));
t = fib_find(f, &a0, len);
if (t)
return t;
len--;
}
return NULL;
}
*/
static inline void
fib_merge_readers(struct fib_iterator *i, struct fib_node *to)
{
if (to)
{
struct fib_iterator *j = to->readers;
if (!j)
{
/* Fast path */
to->readers = i;
i->prev = (struct fib_iterator *) to;
}
else
{
/* Really merging */
while (j->next)
j = j->next;
j->next = i;
i->prev = j;
}
while (i && i->node)
{
i->node = NULL;
i = i->next;
}
}
else /* No more nodes */
while (i)
{
i->prev = NULL;
i = i->next;
}
}
/**
* fib_delete - delete a FIB node
* @f: FIB to delete from
* @E: entry to delete
*
* This function removes the given entry from the FIB,
* taking care of all the asynchronous readers by shifting
* them to the next node in the canonical reading order.
*/
void
fib_delete(struct fib *f, void *E)
{
struct fib_node *e = fib_user_to_node(f, E);
uint h = fib_hash(f, e->addr);
struct fib_node **ee = f->hash_table + h;
struct fib_iterator *it;
while (*ee)
{
if (*ee == e)
{
*ee = e->next;
if (it = e->readers)
{
struct fib_node *l = e->next;
while (!l)
{
h++;
if (h >= f->hash_size)
break;
else
l = f->hash_table[h];
}
fib_merge_readers(it, l);
}
sl_free(f->fib_slab, e);
if (f->entries-- < f->entries_min)
fib_rehash(f, -HASH_LO_STEP);
return;
}
ee = &((*ee)->next);
}
bug("fib_delete() called for invalid node");
}
/**
* fib_free - delete a FIB
* @f: FIB to be deleted
*
* This function deletes a FIB -- it frees all memory associated
* with it and all its entries.
*/
void
fib_free(struct fib *f)
{
fib_ht_free(f->hash_table);
rfree(f->fib_slab);
}
void
fit_init(struct fib_iterator *i, struct fib *f)
{
unsigned h;
struct fib_node *n;
i->efef = 0xff;
for(h=0; h<f->hash_size; h++)
if (n = f->hash_table[h])
{
i->prev = (struct fib_iterator *) n;
if (i->next = n->readers)
i->next->prev = i;
n->readers = i;
i->node = n;
return;
}
/* The fib is empty, nothing to do */
i->prev = i->next = NULL;
i->node = NULL;
}
struct fib_node *
fit_get(struct fib *f, struct fib_iterator *i)
{
struct fib_node *n;
struct fib_iterator *j, *k;
if (!i->prev)
{
/* We are at the end */
i->hash = ~0 - 1;
return NULL;
}
if (!(n = i->node))
{
/* No node info available, we are a victim of merging. Try harder. */
j = i;
while (j->efef == 0xff)
j = j->prev;
n = (struct fib_node *) j;
}
j = i->prev;
if (k = i->next)
k->prev = j;
j->next = k;
i->hash = fib_hash(f, n->addr);
return n;
}
void
fit_put(struct fib_iterator *i, struct fib_node *n)
{
struct fib_iterator *j;
i->node = n;
if (j = n->readers)
j->prev = i;
i->next = j;
n->readers = i;
i->prev = (struct fib_iterator *) n;
}
void
fit_put_next(struct fib *f, struct fib_iterator *i, struct fib_node *n, uint hpos)
{
if (n = n->next)
goto found;
while (++hpos < f->hash_size)
if (n = f->hash_table[hpos])
goto found;
/* We are at the end */
i->prev = i->next = NULL;
i->node = NULL;
return;
found:
fit_put(i, n);
}
#ifdef DEBUGGING
/**
* fib_check - audit a FIB
* @f: FIB to be checked
*
* This debugging function audits a FIB by checking its internal consistency.
* Use when you suspect somebody of corrupting innocent data structures.
*/
void
fib_check(struct fib *f)
{
uint i, ec, lo, nulls;
ec = 0;
for(i=0; i<f->hash_size; i++)
{
struct fib_node *n;
lo = 0;
for(n=f->hash_table[i]; n; n=n->next)
{
struct fib_iterator *j, *j0;
uint h0 = ipa_hash(n->prefix);
if (h0 < lo)
bug("fib_check: discord in hash chains");
lo = h0;
if ((h0 >> f->hash_shift) != i)
bug("fib_check: mishashed %x->%x (order %d)", h0, i, f->hash_order);
j0 = (struct fib_iterator *) n;
nulls = 0;
for(j=n->readers; j; j=j->next)
{
if (j->prev != j0)
bug("fib_check: iterator->prev mismatch");
j0 = j;
if (!j->node)
nulls++;
else if (nulls)
bug("fib_check: iterator nullified");
else if (j->node != n)
bug("fib_check: iterator->node mismatch");
}
ec++;
}
}
if (ec != f->entries)
bug("fib_check: invalid entry count (%d != %d)", ec, f->entries);
}
/*
int
fib_histogram(struct fib *f)
{
log(L_WARN "Histogram dump start %d %d", f->hash_size, f->entries);
int i, j;
struct fib_node *e;
for (i = 0; i < f->hash_size; i++)
{
j = 0;
for (e = f->hash_table[i]; e != NULL; e = e->next)
j++;
if (j > 0)
log(L_WARN "Histogram line %d: %d", i, j);
}
log(L_WARN "Histogram dump end");
}
*/
#endif
#ifdef TEST
#include "lib/resource.h"
struct fib f;
void dump(char *m)
{
uint i;
debug("%s ... order=%d, size=%d, entries=%d\n", m, f.hash_order, f.hash_size, f.hash_size);
for(i=0; i<f.hash_size; i++)
{
struct fib_node *n;
struct fib_iterator *j;
for(n=f.hash_table[i]; n; n=n->next)
{
debug("%04x %08x %p %N", i, ipa_hash(n->prefix), n, n->addr);
for(j=n->readers; j; j=j->next)
debug(" %p[%p]", j, j->node);
debug("\n");
}
}
fib_check(&f);
debug("-----\n");
}
void init(struct fib_node *n)
{
}
int main(void)
{
struct fib_node *n;
struct fib_iterator i, j;
ip_addr a;
int c;
log_init_debug(NULL);
resource_init();
fib_init(&f, &root_pool, sizeof(struct fib_node), 4, init);
dump("init");
a = ipa_from_u32(0x01020304); n = fib_get(&f, &a, 32);
a = ipa_from_u32(0x02030405); n = fib_get(&f, &a, 32);
a = ipa_from_u32(0x03040506); n = fib_get(&f, &a, 32);
a = ipa_from_u32(0x00000000); n = fib_get(&f, &a, 32);
a = ipa_from_u32(0x00000c01); n = fib_get(&f, &a, 32);
a = ipa_from_u32(0xffffffff); n = fib_get(&f, &a, 32);
dump("fill");
fit_init(&i, &f);
dump("iter init");
fib_rehash(&f, 1);
dump("rehash up");
fib_rehash(&f, -1);
dump("rehash down");
next:
c = 0;
FIB_ITERATE_START(&f, &i, z)
{
if (c)
{
FIB_ITERATE_PUT(&i, z);
dump("iter");
goto next;
}
c = 1;
debug("got %p\n", z);
}
FIB_ITERATE_END(z);
dump("iter end");
fit_init(&i, &f);
fit_init(&j, &f);
dump("iter init 2");
n = fit_get(&f, &i);
dump("iter step 2");
fit_put(&i, n->next);
dump("iter step 3");
a = ipa_from_u32(0xffffffff); n = fib_get(&f, &a, 32);
fib_delete(&f, n);
dump("iter step 3");
return 0;
}
#endif
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