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bird/filter/trie.c

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/*
* Filters: Trie for prefix sets
*
* (c) 2009--2021 Ondrej Zajicek <santiago@crfreenet.org>
* (c) 2009--2021 CZ.NIC z.s.p.o.
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
/**
* DOC: Trie for prefix sets
*
* We use a (compressed) trie to represent prefix sets. Every node in the trie
* represents one prefix (&addr/&plen) and &plen also indicates the index of
* bits in the address that are used to branch at the node. Note that such
* prefix is not necessary a member of the prefix set, it is just a canonical
* prefix associated with a node. Prefix lengths of nodes are aligned to
* multiples of &TRIE_STEP (4) and there is 16-way branching in each
* node. Therefore, we say that a node is associated with a range of prefix
* lengths (&plen .. &plen + TRIE_STEP - 1).
*
* The prefix set is not just a set of prefixes, it is defined by a set of
* prefix patterns. Each prefix pattern consists of &ppaddr/&pplen and two
* integers: &low and &high. The tested prefix &paddr/&plen matches that pattern
* if the first MIN(&plen, &pplen) bits of &paddr and &ppaddr are the same and
* &low <= &plen <= &high.
*
* There are two ways to represent accepted prefixes for a node. First, there is
* a bitmask &local, which represents independently all 15 prefixes that extend
* the canonical prefix of the node and are within a range of prefix lengths
* associated with the node. E.g., for node 10.0.0.0/8 they are 10.0.0.0/8,
* 10.0.0.0/9, 10.128.0.0/9, .. 10.224.0.0/11. This order (first by length, then
* lexicographically) is used for indexing the bitmask &local, starting at
* position 1. I.e., index is 2^(plen - base) + offset within the same length,
* see function trie_local_mask6() for details.
*
* Second, we use a bitmask &accept to represent accepted prefix lengths at a
* node. The bit is set means that all prefixes of given length that are either
* subprefixes or superprefixes of the canonical prefix are accepted. As there
* are 33 prefix lengths (0..32 for IPv4), but there is just one prefix of zero
* length in the whole trie so we have &zero flag in &f_trie (indicating whether
* the trie accepts prefix 0.0.0.0/0) as a special case, and &accept bitmask
* represents accepted prefix lengths from 1 to 32.
*
* One complication is handling of prefix patterns with unaligned prefix length.
* When such pattern is to be added, we add a primary node above (with rounded
* down prefix length &nlen) and a set of secondary nodes below (with rounded up
* prefix lengths &slen). Accepted prefix lengths of the original prefix pattern
* are then represented in different places based on their lengths. For prefixes
* shorter than &nlen, it is &accept bitmask of the primary node, for prefixes
* between &nlen and &slen - 1 it is &local bitmask of the primary node, and for
* prefixes longer of equal &slen it is &accept bitmasks of secondary nodes.
*
* There are two cases in prefix matching - a match when the length of the
* prefix is smaller that the length of the prefix pattern, (&plen < &pplen) and
* otherwise. The second case is simple - we just walk through the trie and look
* at every visited node whether that prefix accepts our prefix length (&plen).
* The first case is tricky - we do not want to examine every descendant of a
* final node, so (when we create the trie) we have to propagate that
* information from nodes to their ascendants.
*
* There are two kinds of propagations - propagation from child's &accept
* bitmask to parent's &accept bitmask, and propagation from child's &accept
* bitmask to parent's &local bitmask. The first kind is simple - as all
* superprefixes of a parent are also all superprefixes of appropriate length of
* a child, then we can just add (by bitwise or) a child &accept mask masked by
* parent prefix length mask to the parent &accept mask. This handles prefixes
* shorter than node &plen.
*
* The second kind of propagation is necessary to handle superprefixes of a
* child that are represented by parent &local mask - that are in the range of
* prefix lengths associated with the parent. For each accepted (by child
* &accept mask) prefix length from that range, we need to set appropriate bit
* in &local mask. See function trie_amask_to_local() for details.
*
* There are four cases when we walk through a trie:
*
* - we are in NULL
* - we are out of path (prefixes are inconsistent)
* - we are in the wanted (final) node (node length == &plen)
* - we are beyond the end of path (node length > &plen)
* - we are still on path and keep walking (node length < &plen)
*
* The walking code in trie_match_net() is structured according to these cases.
*
* Iteration over prefixes in a trie can be done using TRIE_WALK() macro, or
* directly using trie_walk_init() and trie_walk_next() functions. The second
* approach allows suspending the iteration and continuing in it later.
* Prefixes are enumerated in the usual lexicographic order and may be
* restricted to a subset of the trie (all subnets of a specified prefix).
*
* Note that the trie walk does not reliably enumerate `implicit' prefixes
* defined by &low and &high fields in prefix patterns, it is supposed to be
* used on tries constructed from `explicit' prefixes (&low == &plen == &high
* in call to trie_add_prefix()).
*
* The trie walk has three basic state variables stored in the struct
* &f_trie_walk_state -- the current node in &stack[stack_pos], &accept_length
* for iteration over inter-node prefixes (non-branching prefixes on compressed
* path between the current node and its parent node, stored in the bitmap
* &accept of the current node) and &local_pos for iteration over intra-node
* prefixes (stored in the bitmap &local).
*
* The trie also supports longest-prefix-match query by trie_match_longest_ip4()
* and it can be extended to iteration over all covering prefixes for a given
* prefix (from longest to shortest) using TRIE_WALK_TO_ROOT_IP4() macro. There
* are also IPv6 versions (for practical reasons, these functions and macros are
* separate for IPv4 and IPv6). There is the same limitation to enumeration of
* `implicit' prefixes like with the previous TRIE_WALK() macro.
*/
#include "nest/bird.h"
#include "lib/string.h"
#include "conf/conf.h"
#include "filter/filter.h"
#include "filter/data.h"
/*
* In the trie_add_prefix(), we use ip_addr (assuming that it is the same as
* ip6_addr) to handle both IPv4 and IPv6 prefixes. In contrast to rest of the
* BIRD, IPv4 addresses are just zero-padded from right. That is why we have
* ipt_from_ip4() and ipt_to_ip4() macros below.
*/
#define ipa_mkmask(x) ip6_mkmask(x)
#define ipa_masklen(x) ip6_masklen(&x)
#define ipa_pxlen(x,y) ip6_pxlen(x,y)
#define ipa_getbit(a,p) ip6_getbit(a,p)
#define ipa_getbits(a,p,n) ip6_getbits(a,p,n)
#define ipa_setbits(a,p,n) ip6_setbits(a,p,n)
#define trie_local_mask(a,b,c) trie_local_mask6(a,b,c)
#define ipt_from_ip4(x) _MI6(_I(x), 0, 0, 0)
#define ipt_to_ip4(x) _MI4(_I0(x))
/**
* f_new_trie - allocates and returns a new empty trie
* @lp: linear pool to allocate items from
* @data_size: user data attached to node
*/
struct f_trie *
f_new_trie(linpool *lp, uint data_size)
{
struct f_trie * ret;
ret = lp_allocz(lp, sizeof(struct f_trie) + data_size);
ret->lp = lp;
ret->ipv4 = -1;
ret->data_size = data_size;
return ret;
}
static inline struct f_trie_node4 *
new_node4(struct f_trie *t, uint plen, uint local, ip4_addr paddr, ip4_addr pmask, ip4_addr amask)
{
struct f_trie_node4 *n = lp_allocz(t->lp, sizeof(struct f_trie_node4) + t->data_size);
n->plen = plen;
n->local = local;
n->addr = paddr;
n->mask = pmask;
n->accept = amask;
return n;
}
static inline struct f_trie_node6 *
new_node6(struct f_trie *t, uint plen, uint local, ip6_addr paddr, ip6_addr pmask, ip6_addr amask)
{
struct f_trie_node6 *n = lp_allocz(t->lp, sizeof(struct f_trie_node6) + t->data_size);
n->plen = plen;
n->local = local;
n->addr = paddr;
n->mask = pmask;
n->accept = amask;
return n;
}
static inline struct f_trie_node *
new_node(struct f_trie *t, uint plen, uint local, ip_addr paddr, ip_addr pmask, ip_addr amask)
{
if (t->ipv4)
return (struct f_trie_node *) new_node4(t, plen, local, ipt_to_ip4(paddr), ipt_to_ip4(pmask), ipt_to_ip4(amask));
else
return (struct f_trie_node *) new_node6(t, plen, local, ipa_to_ip6(paddr), ipa_to_ip6(pmask), ipa_to_ip6(amask));
}
static inline void
attach_node4(struct f_trie_node4 *parent, struct f_trie_node4 *child)
{
parent->c[ip4_getbits(child->addr, parent->plen, TRIE_STEP)] = child;
}
static inline void
attach_node6(struct f_trie_node6 *parent, struct f_trie_node6 *child)
{
parent->c[ip6_getbits(child->addr, parent->plen, TRIE_STEP)] = child;
}
static inline void
attach_node(struct f_trie_node *parent, struct f_trie_node *child, int v4)
{
if (v4)
attach_node4(&parent->v4, &child->v4);
else
attach_node6(&parent->v6, &child->v6);
}
/*
* Internal prefixes of a node a represented by the local bitmask, each bit for
* one prefix. Bit 0 is unused, Bit 1 is for the main prefix of the node,
* remaining bits correspond to subprefixes by this pattern:
*
* 1
* 2 3
* 4 5 6 7
* 8 9 A B C D E F
*
* E.g. for 10.0.0.0/8 node, the 10.64.0.0/10 would be position 5.
*/
/*
* Compute appropriate mask representing prefix px/plen in local bitmask of node
* with prefix length nlen. Assuming that nlen <= plen < (nlen + TRIE_STEP).
*/
static inline uint
trie_local_mask4(ip4_addr px, uint plen, uint nlen)
{
uint step = plen - nlen;
uint pos = (1u << step) + ip4_getbits(px, nlen, step);
return 1u << pos;
}
static inline uint
trie_local_mask6(ip6_addr px, uint plen, uint nlen)
{
uint step = plen - nlen;
uint pos = (1u << step) + ip6_getbits(px, nlen, step);
return 1u << pos;
}
/*
* Compute an appropriate local mask (for a node with prefix length nlen)
* representing prefixes of px that are accepted by amask and fall within the
* range associated with that node. Used for propagation of child accept mask
* to parent local mask.
*/
static inline uint
trie_amask_to_local(ip_addr px, ip_addr amask, uint nlen)
{
uint local = 0;
for (uint plen = MAX(nlen, 1); plen < (nlen + TRIE_STEP); plen++)
if (ipa_getbit(amask, plen - 1))
local |= trie_local_mask(px, plen, nlen);
return local;
}
/*
* Compute a bitmask representing a level of subprefixes (of the same length),
* using specified position as a root. E.g., level 2 from root position 3 would
* be bit positions C-F, returned as bitmask 0xf000.
*/
static inline uint
trie_level_mask(uint pos, uint level)
{
return ((1u << (1u << level)) - 1) << (pos << level);
}
#define GET_ADDR(N,F,X) ((X) ? ipt_from_ip4((N)->v4.F) : ipa_from_ip6((N)->v6.F))
#define SET_ADDR(N,F,X,V) ({ if (X) (N)->v4.F =ipt_to_ip4(V); else (N)->v6.F =ipa_to_ip6(V); })
#define GET_LOCAL(N,X) ((X) ? (N)->v4.local : (N)->v6.local)
#define ADD_LOCAL(N,X,V) ({ uint v_ = (V); if (X) (N)->v4.local |= v_; else (N)->v6.local |= v_; })
#define GET_CHILD(N,X,I) ((X) ? (struct f_trie_node *) (N)->v4.c[I] : (struct f_trie_node *) (N)->v6.c[I])
static void *
trie_add_node(struct f_trie *t, uint plen, ip_addr px, uint local, uint l, uint h)
{
uint l_ = l ? (l - 1) : 0;
ip_addr amask = (l_ < h) ? ipa_xor(ipa_mkmask(l_), ipa_mkmask(h)) : IPA_NONE;
ip_addr pmask = ipa_mkmask(plen);
ip_addr paddr = ipa_and(px, pmask);
struct f_trie_node *o = NULL;
struct f_trie_node *n = &t->root;
int v4 = t->ipv4;
/* Add all bits for each active level (0x0002 0x000c 0x00f0 0xff00) */
for (uint i = 0; i < TRIE_STEP; i++)
if ((l <= (plen + i)) && ((plen + i) <= h))
local |= trie_level_mask(1, i);
DBG("Insert node %I/%u (%I %x)\n", paddr, plen, amask, local);
while (n)
{
ip_addr naddr = GET_ADDR(n, addr, v4);
ip_addr nmask = GET_ADDR(n, mask, v4);
ip_addr accept = GET_ADDR(n, accept, v4);
ip_addr cmask = ipa_and(nmask, pmask);
uint nlen = v4 ? n->v4.plen : n->v6.plen;
DBG("Found node %I/%u (%I %x)\n",
naddr, nlen, accept, v4 ? n->v4.local : n->v6.local);
if (ipa_compare(ipa_and(paddr, cmask), ipa_and(naddr, cmask)))
{
/* We are out of path - we have to add branching node 'b'
between node 'o' and node 'n', and attach new node 'a'
as the other child of 'b'. */
int blen = ROUND_DOWN_POW2(ipa_pxlen(paddr, naddr), TRIE_STEP);
ip_addr bmask = ipa_mkmask(blen);
ip_addr baddr = ipa_and(px, bmask);
/* Merge accept masks from children to get accept mask for node 'b' */
ip_addr baccm = ipa_and(ipa_or(amask, accept), bmask);
uint bloc = trie_amask_to_local(naddr, accept, blen) |
trie_amask_to_local(paddr, amask, blen);
struct f_trie_node *a = new_node(t, plen, local, paddr, pmask, amask);
struct f_trie_node *b = new_node(t, blen, bloc, baddr, bmask, baccm);
attach_node(o, b, v4);
attach_node(b, n, v4);
attach_node(b, a, v4);
t->prefix_count++;
DBG("Case 1\n");
return a;
}
if (plen < nlen)
{
/* We add new node 'a' between node 'o' and node 'n' */
amask = ipa_or(amask, ipa_and(accept, pmask));
local |= trie_amask_to_local(naddr, accept, plen);
struct f_trie_node *a = new_node(t, plen, local, paddr, pmask, amask);
attach_node(o, a, v4);
attach_node(a, n, v4);
t->prefix_count++;
DBG("Case 2\n");
return a;
}
if (plen == nlen)
{
/* We already found added node in trie. Just update accept and local mask */
accept = ipa_or(accept, amask);
SET_ADDR(n, accept, v4, accept);
if ((GET_LOCAL(n, v4) & local) != local)
t->prefix_count++;
ADD_LOCAL(n, v4, local);
DBG("Case 3\n");
return n;
}
/* Update accept mask part M2 and go deeper */
accept = ipa_or(accept, ipa_and(amask, nmask));
SET_ADDR(n, accept, v4, accept);
ADD_LOCAL(n, v4, trie_amask_to_local(paddr, amask, nlen));
DBG("Step %u\n", ipa_getbits(paddr, nlen));
/* n->plen < plen and plen <= 32 (128) */
o = n;
n = GET_CHILD(n, v4, ipa_getbits(paddr, nlen, TRIE_STEP));
}
/* We add new tail node 'a' after node 'o' */
struct f_trie_node *a = new_node(t, plen, local, paddr, pmask, amask);
attach_node(o, a, v4);
t->prefix_count++;
DBG("Case 4\n");
return a;
}
/**
* trie_add_prefix
* @t: trie to add to
* @net: IP network prefix
* @l: prefix lower bound
* @h: prefix upper bound
*
* Adds prefix (prefix pattern) @n to trie @t. @l and @h are lower
* and upper bounds on accepted prefix lengths, both inclusive.
* 0 <= l, h <= 32 (128 for IPv6).
*
* Returns a pointer to the allocated node. The function can return a pointer to
* an existing node if @px and @plen are the same. If px/plen == 0/0 (or ::/0),
* a pointer to the root node is returned. Returns NULL when called with
* mismatched IPv4/IPv6 net type.
*/
void *
trie_add_prefix(struct f_trie *t, const net_addr *net, uint l, uint h)
{
uint plen = net_pxlen(net);
ip_addr px;
int v4;
switch (net->type)
{
case NET_IP4:
case NET_VPN4:
case NET_ROA4:
px = ipt_from_ip4(net4_prefix(net));
v4 = 1;
break;
case NET_IP6:
case NET_VPN6:
case NET_ROA6:
case NET_IP6_SADR:
px = ipa_from_ip6(net6_prefix(net));
v4 = 0;
break;
default:
bug("invalid type");
}
if (t->ipv4 != v4)
{
if (t->ipv4 < 0)
t->ipv4 = v4;
else
return NULL;
}
DBG("\nInsert net %N (%u-%u)\n", net, l, h);
if (l == 0)
t->zero = 1;
if (h < plen)
plen = h;
/* Primary node length, plen rounded down */
uint nlen = ROUND_DOWN_POW2(plen, TRIE_STEP);
if (plen == nlen)
return trie_add_node(t, nlen, px, 0, l, h);
/* Secondary node length, plen rouned up */
uint slen = nlen + TRIE_STEP;
void *node = NULL;
/*
* For unaligned prefix lengths it is more complicated. We need to encode
* matching prefixes of lengths from l to h. There are three cases of lengths:
*
* 1) 0..nlen are encoded by the accept mask of the primary node
* 2) nlen..(slen-1) are encoded by the local mask of the primary node
* 3) slen..max are encoded in secondary nodes
*/
if (l < slen)
{
uint local = 0;
/* Compute local bits for accepted nlen..(slen-1) prefixes */
for (uint i = 0; i < TRIE_STEP; i++)
if ((l <= (nlen + i)) && ((nlen + i) <= h))
{
uint pos = (1u << i) + ipa_getbits(px, nlen, i);
uint len = ((nlen + i) <= plen) ? 1 : (1u << (nlen + i - plen));
/* We need to fill 'len' bits starting at 'pos' position */
local |= ((1u << len) - 1) << pos;
}
/* Add the primary node */
node = trie_add_node(t, nlen, px, local, l, nlen);
}
if (slen <= h)
{
uint l2 = MAX(l, slen);
uint max = (1u << (slen - plen));
/* Add secondary nodes */
for (uint i = 0; i < max; i++)
node = trie_add_node(t, slen, ipa_setbits(px, slen - 1, i), 0, l2, h);
}
return node;
}
static int
trie_match_net4(const struct f_trie *t, ip4_addr px, uint plen)
{
if (plen == 0)
return t->zero;
int plentest = plen - 1;
uint nlen = ROUND_DOWN_POW2(plen, TRIE_STEP);
uint local = trie_local_mask4(px, plen, nlen);
const struct f_trie_node4 *n = &t->root.v4;
while (n)
{
/* We are out of path */
if (!ip4_prefix_equal(px, n->addr, MIN(plen, n->plen)))
return 0;
/* Check local mask */
if ((n->plen == nlen) && (n->local & local))
return 1;
/* Check accept mask */
if (ip4_getbit(n->accept, plentest))
return 1;
/* We finished trie walk and still no match */
if (nlen <= n->plen)
return 0;
/* Choose children */
n = n->c[ip4_getbits(px, n->plen, TRIE_STEP)];
}
return 0;
}
static int
trie_match_net6(const struct f_trie *t, ip6_addr px, uint plen)
{
if (plen == 0)
return t->zero;
int plentest = plen - 1;
uint nlen = ROUND_DOWN_POW2(plen, TRIE_STEP);
uint local = trie_local_mask6(px, plen, nlen);
const struct f_trie_node6 *n = &t->root.v6;
while (n)
{
/* We are out of path */
if (!ip6_prefix_equal(px, n->addr, MIN(plen, n->plen)))
return 0;
/* Check local mask */
if ((n->plen == nlen) && (n->local & local))
return 1;
/* Check accept mask */
if (ip6_getbit(n->accept, plentest))
return 1;
/* We finished trie walk and still no match */
if (nlen <= n->plen)
return 0;
/* Choose children */
n = n->c[ip6_getbits(px, n->plen, TRIE_STEP)];
}
return 0;
}
/**
* trie_match_net
* @t: trie
* @n: net address
*
* Tries to find a matching net in the trie such that
* prefix @n matches that prefix pattern. Returns 1 if there
* is such prefix pattern in the trie.
*/
int
trie_match_net(const struct f_trie *t, const net_addr *n)
{
switch (n->type)
{
case NET_IP4:
case NET_VPN4:
case NET_ROA4:
return t->ipv4 ? trie_match_net4(t, net4_prefix(n), net_pxlen(n)) : 0;
case NET_IP6:
case NET_VPN6:
case NET_ROA6:
return !t->ipv4 ? trie_match_net6(t, net6_prefix(n), net_pxlen(n)) : 0;
default:
return 0;
}
}
/**
* trie_match_longest_ip4
* @t: trie
* @net: net address
* @dst: return value
* @found0: optional returned bitmask of found nodes
*
* Perform longest prefix match for the address @net and return the resulting
* prefix in the buffer @dst. The bitmask @found0 is used to report lengths of
* prefixes on the path from the root to the resulting prefix. E.g., if there is
* also a /20 shorter matching prefix, then 20-th bit is set in @found0. This
* can be used to enumerate all matching prefixes for the network @net using
* function trie_match_next_longest_ip4() or macro TRIE_WALK_TO_ROOT_IP4().
*
* This function assumes IPv4 trie, there is also an IPv6 variant. The @net
* argument is typed as net_addr_ip4, but would accept any IPv4-based net_addr,
* like net4_prefix(). Anyway, returned @dst is always net_addr_ip4.
*
* Result: 1 if a matching prefix was found, 0 if not.
*/
int
trie_match_longest_ip4(const struct f_trie *t, const net_addr_ip4 *net, net_addr_ip4 *dst, ip4_addr *found0)
{
ASSERT(t->ipv4);
const ip4_addr prefix = net->prefix;
const int pxlen = net->pxlen;
const struct f_trie_node4 *n = &t->root.v4;
int len = 0;
ip4_addr found = IP4_NONE;
int last = -1;
while (n)
{
/* We are out of path */
if (!ip4_prefix_equal(prefix, n->addr, MIN(pxlen, n->plen)))
goto done;
/* Check accept mask */
for (; len < n->plen; len++)
{
if (len > pxlen)
goto done;
if (ip4_getbit(n->accept, len - 1))
{
/* len is always < 32 due to len < n->plen */
ip4_setbit(&found, len);
last = len;
}
}
/* Special case for max length, there is only one valid local position */
if (len == IP4_MAX_PREFIX_LENGTH)
{
if (n->local & (1u << 1))
last = len;
goto done;
}
/* Check local mask */
for (int pos = 1; pos < (1 << TRIE_STEP); pos = 2 * pos + ip4_getbit(prefix, len), len++)
{
if (len > pxlen)
goto done;
if (n->local & (1u << pos))
{
/* len is always < 32 due to special case above */
ip4_setbit(&found, len);
last = len;
}
}
/* Choose child */
n = n->c[ip4_getbits(prefix, n->plen, TRIE_STEP)];
}
done:
if (last < 0)
return 0;
*dst = NET_ADDR_IP4(ip4_and(prefix, ip4_mkmask(last)), last);
if (found0)
*found0 = found;
return 1;
}
/**
* trie_match_longest_ip6
* @t: trie
* @net: net address
* @dst: return value
* @found0: optional returned bitmask of found nodes
*
* Perform longest prefix match for the address @net and return the resulting
* prefix in the buffer @dst. The bitmask @found0 is used to report lengths of
* prefixes on the path from the root to the resulting prefix. E.g., if there is
* also a /20 shorter matching prefix, then 20-th bit is set in @found0. This
* can be used to enumerate all matching prefixes for the network @net using
* function trie_match_next_longest_ip6() or macro TRIE_WALK_TO_ROOT_IP6().
*
* This function assumes IPv6 trie, there is also an IPv4 variant. The @net
* argument is typed as net_addr_ip6, but would accept any IPv6-based net_addr,
* like net6_prefix(). Anyway, returned @dst is always net_addr_ip6.
*
* Result: 1 if a matching prefix was found, 0 if not.
*/
int
trie_match_longest_ip6(const struct f_trie *t, const net_addr_ip6 *net, net_addr_ip6 *dst, ip6_addr *found0)
{
ASSERT(!t->ipv4);
const ip6_addr prefix = net->prefix;
const int pxlen = net->pxlen;
const struct f_trie_node6 *n = &t->root.v6;
int len = 0;
ip6_addr found = IP6_NONE;
int last = -1;
while (n)
{
/* We are out of path */
if (!ip6_prefix_equal(prefix, n->addr, MIN(pxlen, n->plen)))
goto done;
/* Check accept mask */
for (; len < n->plen; len++)
{
if (len > pxlen)
goto done;
if (ip6_getbit(n->accept, len - 1))
{
/* len is always < 128 due to len < n->plen */
ip6_setbit(&found, len);
last = len;
}
}
/* Special case for max length, there is only one valid local position */
if (len == IP6_MAX_PREFIX_LENGTH)
{
if (n->local & (1u << 1))
last = len;
goto done;
}
/* Check local mask */
for (int pos = 1; pos < (1 << TRIE_STEP); pos = 2 * pos + ip6_getbit(prefix, len), len++)
{
if (len > pxlen)
goto done;
if (n->local & (1u << pos))
{
/* len is always < 128 due to special case above */
ip6_setbit(&found, len);
last = len;
}
}
/* Choose child */
n = n->c[ip6_getbits(prefix, n->plen, TRIE_STEP)];
}
done:
if (last < 0)
return 0;
*dst = NET_ADDR_IP6(ip6_and(prefix, ip6_mkmask(last)), last);
if (found0)
*found0 = found;
return 1;
}
#define SAME_PREFIX(A,B,X,L) ((X) ? ip4_prefix_equal((A)->v4.addr, net4_prefix(B), (L)) : ip6_prefix_equal((A)->v6.addr, net6_prefix(B), (L)))
#define GET_NET_BITS(N,X,A,B) ((X) ? ip4_getbits(net4_prefix(N), (A), (B)) : ip6_getbits(net6_prefix(N), (A), (B)))
/**
* trie_walk_init
* @s: walk state
* @t: trie
* @net: optional subnet for walk
*
* Initialize walk state for subsequent walk through nodes of the trie @t by
* trie_walk_next(). The argument @net allows to restrict walk to given subnet,
* otherwise full walk over all nodes is used. This is done by finding node at
* or below @net and starting position in it.
*/
void
trie_walk_init(struct f_trie_walk_state *s, const struct f_trie *t, const net_addr *net)
{
*s = (struct f_trie_walk_state) {
.ipv4 = t->ipv4,
.accept_length = 0,
.start_pos = 1,
.local_pos = 1,
.stack_pos = 0,
.stack[0] = &t->root
};
if (!net)
return;
/* We want to find node of level at least plen */
int plen = ROUND_DOWN_POW2(net->pxlen, TRIE_STEP);
const struct f_trie_node *n = &t->root;
const int v4 = t->ipv4;
while (n)
{
int nlen = v4 ? n->v4.plen : n->v6.plen;
/* We are out of path */
if (!SAME_PREFIX(n, net, v4, MIN(net->pxlen, nlen)))
break;
/* We found final node */
if (nlen >= plen)
{
if (nlen == plen)
{
/* Find proper local_pos, while accept_length is not used */
int step = net->pxlen - plen;
s->start_pos = s->local_pos = (1u << step) + GET_NET_BITS(net, v4, plen, step);
s->accept_length = plen;
}
else
{
/* Start from pos 1 in local node, but first try accept mask */
s->accept_length = net->pxlen;
}
s->stack[0] = n;
return;
}
/* Choose child */
n = GET_CHILD(n, v4, GET_NET_BITS(net, v4, nlen, TRIE_STEP));
}
s->stack[0] = NULL;
return;
}
#define GET_ACCEPT_BIT(N,X,B) ((X) ? ip4_getbit((N)->v4.accept, (B)) : ip6_getbit((N)->v6.accept, (B)))
#define GET_LOCAL_BIT(N,X,B) (((X) ? (N)->v4.local : (N)->v6.local) & (1u << (B)))
/**
* trie_walk_next
* @s: walk state
* @net: return value
*
* Find the next prefix in the trie walk and return it in the buffer @net.
* Prefixes are walked in the usual lexicographic order and may be restricted
* to a subset of the trie during walk setup by trie_walk_init(). Note that the
* trie walk does not iterate reliably over 'implicit' prefixes defined by &low
* and &high fields in prefix patterns, it is supposed to be used on tries
* constructed from 'explicit' prefixes (&low == &plen == &high in call to
* trie_add_prefix()).
*
* Result: 1 if the next prefix was found, 0 for the end of walk.
*/
int
trie_walk_next(struct f_trie_walk_state *s, net_addr *net)
{
const struct f_trie_node *n = s->stack[s->stack_pos];
int len = s->accept_length;
int pos = s->local_pos;
int v4 = s->ipv4;
/*
* The walk has three basic state variables -- n, len and pos. In each node n,
* we first walk superprefixes (by len in &accept bitmask), and then we walk
* internal positions (by pos in &local bitmask). These positions are:
*
* 1
* 2 3
* 4 5 6 7
* 8 9 A B C D E F
*
* We walk them depth-first, including virtual positions 10-1F that are
* equivalent of position 1 in child nodes 0-F.
*/
if (!n)
{
memset(net, 0, v4 ? sizeof(net_addr_ip4) : sizeof(net_addr_ip6));
return 0;
}
next_node:;
/* Current node prefix length */
int nlen = v4 ? n->v4.plen : n->v6.plen;
/* First, check for accept prefix */
for (; len < nlen; len++)
if (GET_ACCEPT_BIT(n, v4, len - 1))
{
if (v4)
net_fill_ip4(net, ip4_and(n->v4.addr, ip4_mkmask(len)), len);
else
net_fill_ip6(net, ip6_and(n->v6.addr, ip6_mkmask(len)), len);
s->local_pos = pos;
s->accept_length = len + 1;
return 1;
}
next_pos:
/* Bottom of this node */
if (pos >= (1 << TRIE_STEP))
{
const struct f_trie_node *child = GET_CHILD(n, v4, pos - (1 << TRIE_STEP));
int dir = 0;
/* No child node */
if (!child)
{
/* Step up until return from left child (pos is even) */
do
{
/* Step up from start node */
if ((s->stack_pos == 0) && (pos == s->start_pos))
{
s->stack[0] = NULL;
memset(net, 0, v4 ? sizeof(net_addr_ip4) : sizeof(net_addr_ip6));
return 0;
}
/* Top of this node */
if (pos == 1)
{
ASSERT(s->stack_pos);
const struct f_trie_node *old = n;
/* Move to parent node */
s->stack_pos--;
n = s->stack[s->stack_pos];
nlen = v4 ? n->v4.plen : n->v6.plen;
pos = v4 ?
ip4_getbits(old->v4.addr, nlen, TRIE_STEP) :
ip6_getbits(old->v6.addr, nlen, TRIE_STEP);
pos += (1 << TRIE_STEP);
len = nlen;
ASSERT(GET_CHILD(n, v4, pos - (1 << TRIE_STEP)) == old);
}
/* Step up */
dir = pos % 2;
pos = pos / 2;
}
while (dir);
/* Continue with step down to the right child */
pos = 2 * pos + 1;
goto next_pos;
}
/* Move to child node */
pos = 1;
len = nlen + TRIE_STEP;
s->stack_pos++;
n = s->stack[s->stack_pos] = child;
goto next_node;
}
/* Check for local prefix */
if (GET_LOCAL_BIT(n, v4, pos))
{
/* Convert pos to address of local network */
int x = (pos >= 2) + (pos >= 4) + (pos >= 8);
int y = pos & ((1u << x) - 1);
if (v4)
net_fill_ip4(net, !x ? n->v4.addr : ip4_setbits(n->v4.addr, nlen + x - 1, y), nlen + x);
else
net_fill_ip6(net, !x ? n->v6.addr : ip6_setbits(n->v6.addr, nlen + x - 1, y), nlen + x);
s->local_pos = 2 * pos;
s->accept_length = len;
return 1;
}
/* Step down */
pos = 2 * pos;
goto next_pos;
}
static int
trie_node_same4(const struct f_trie_node4 *t1, const struct f_trie_node4 *t2)
{
if ((t1 == NULL) && (t2 == NULL))
return 1;
if ((t1 == NULL) || (t2 == NULL))
return 0;
if ((t1->plen != t2->plen) ||
(! ip4_equal(t1->addr, t2->addr)) ||
(! ip4_equal(t1->accept, t2->accept)))
return 0;
for (uint i = 0; i < (1 << TRIE_STEP); i++)
if (! trie_node_same4(t1->c[i], t2->c[i]))
return 0;
return 1;
}
static int
trie_node_same6(const struct f_trie_node6 *t1, const struct f_trie_node6 *t2)
{
if ((t1 == NULL) && (t2 == NULL))
return 1;
if ((t1 == NULL) || (t2 == NULL))
return 0;
if ((t1->plen != t2->plen) ||
(! ip6_equal(t1->addr, t2->addr)) ||
(! ip6_equal(t1->accept, t2->accept)))
return 0;
for (uint i = 0; i < (1 << TRIE_STEP); i++)
if (! trie_node_same6(t1->c[i], t2->c[i]))
return 0;
return 1;
}
/**
* trie_same
* @t1: first trie to be compared
* @t2: second one
*
* Compares two tries and returns 1 if they are same
*/
int
trie_same(const struct f_trie *t1, const struct f_trie *t2)
{
if ((t1->zero != t2->zero) || (t1->ipv4 != t2->ipv4))
return 0;
if (t1->ipv4)
return trie_node_same4(&t1->root.v4, &t2->root.v4);
else
return trie_node_same6(&t1->root.v6, &t2->root.v6);
}
static const u8 log2[16] = {0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3};
static void
trie_node_format(const struct f_trie_node *n, buffer *buf, int v4)
{
if (n == NULL)
return;
if (v4)
{
if (ip4_nonzero(n->v4.accept))
buffer_print(buf, "%I4/%d{%I4}, ", n->v4.addr, n->v4.plen, n->v4.accept);
}
else
{
if (ip6_nonzero(n->v6.accept))
buffer_print(buf, "%I6/%d{%I6}, ", n->v6.addr, n->v6.plen, n->v6.accept);
}
int nlen = v4 ? n->v4.plen : n->v6.plen;
uint local = v4 ? n->v4.local : n->v6.local;
for (int i = (nlen ? 0 : 1); i < TRIE_STEP; i++)
if (GET_ACCEPT_BIT(n, v4, nlen + i - 1))
local &= ~trie_level_mask(1, i);
for (int pos = 2; local && (pos < (1 << TRIE_STEP)); pos++)
if (local & (1u << pos))
{
int lvl = log2[pos];
int plen = nlen + lvl;
int i;
for (i = 0; lvl + i < TRIE_STEP; i++)
{
uint lmask = trie_level_mask(pos, i);
if ((local & lmask) != lmask)
break;
local &= ~lmask;
}
uint addr_bits = pos & ((1u << lvl) - 1);
uint accept_bits = (1u << i) - 1;
int h = plen + i - 1;
if (v4)
{
ip4_addr addr = ip4_setbits(n->v4.addr, plen - 1, addr_bits);
ip4_addr mask = ip4_setbits(IP4_NONE, h - 1, accept_bits);
buffer_print(buf, "%I4/%d{%I4}, ", addr, plen, mask);
}
else
{
ip6_addr addr = ip6_setbits(n->v6.addr, plen - 1, addr_bits);
ip6_addr mask = ip6_setbits(IP6_NONE, h - 1, accept_bits);
buffer_print(buf, "%I6/%d{%I6}, ", addr, plen, mask);
}
}
for (int i = 0; i < (1 << TRIE_STEP); i++)
trie_node_format(GET_CHILD(n, v4, i), buf, v4);
}
/**
* trie_format
* @t: trie to be formatted
* @buf: destination buffer
*
* Prints the trie to the supplied buffer.
*/
void
trie_format(const struct f_trie *t, buffer *buf)
{
buffer_puts(buf, "[");
if (t->zero)
buffer_print(buf, "%I/%d, ", t->ipv4 ? IPA_NONE4 : IPA_NONE6, 0);
trie_node_format(&t->root, buf, t->ipv4);
if (buf->pos == buf->end)
return;
/* Undo last separator */
if (buf->pos[-1] != '[')
buf->pos -= 2;
buffer_puts(buf, "]");
}
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