bird/filter/filter.c

/*
 *	Filters: utility functions
 *
 *	Copyright 1998 Pavel Machek <pavel@ucw.cz>
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 *
 */

/**
 * DOC: Filters
 *
 * You can find sources of the filter language in |filter/|
 * directory. File |filter/config.Y| contains filter grammar and basically translates
 * the source from user into a tree of &f_inst structures. These trees are
 * later interpreted using code in |filter/filter.c|.
 *
 * A filter is represented by a tree of &f_inst structures, one structure per
 * "instruction". Each &f_inst contains @code, @aux value which is
 * usually the data type this instruction operates on and two generic
 * arguments (@a1, @a2). Some instructions contain pointer(s) to other
 * instructions in their (@a1, @a2) fields.
 *
 * Filters use a &f_val structure for their data. Each &f_val
 * contains type and value (types are constants prefixed with %T_). Few
 * of the types are special; %T_RETURN can be or-ed with a type to indicate
 * that return from a function or from the whole filter should be
 * forced. Important thing about &f_val's is that they may be copied
 * with a simple |=|. That's fine for all currently defined types: strings
 * are read-only (and therefore okay), paths are copied for each
 * operation (okay too).
 */

#undef LOCAL_DEBUG

#include "nest/bird.h"
#include "lib/lists.h"
#include "lib/resource.h"
#include "lib/socket.h"
#include "lib/string.h"
#include "lib/unaligned.h"
#include "lib/net.h"
#include "lib/ip.h"
#include "nest/route.h"
#include "nest/protocol.h"
#include "nest/iface.h"
#include "nest/attrs.h"
#include "conf/conf.h"
#include "filter/filter.h"

#define CMP_ERROR 999

void (*bt_assert_hook)(int result, struct f_inst *assert);

static struct adata undef_adata;	/* adata of length 0 used for undefined */

/* Special undef value for paths and clists */
static inline int
undef_value(struct f_val v)
{
  return ((v.type == T_PATH) || (v.type == T_CLIST) ||
	  (v.type == T_ECLIST) || (v.type == T_LCLIST)) &&
    (v.val.ad == &undef_adata);
}

static struct adata *
adata_empty(struct linpool *pool, int l)
{
  struct adata *res = lp_alloc(pool, sizeof(struct adata) + l);
  res->length = l;
  return res;
}

static void
pm_format(struct f_path_mask *p, buffer *buf)
{
  buffer_puts(buf, "[= ");

  while (p)
  {
    switch(p->kind)
    {
    case PM_ASN:
      buffer_print(buf, "%u ", p->val);
      break;

    case PM_QUESTION:
      buffer_puts(buf, "? ");
      break;

    case PM_ASTERISK:
      buffer_puts(buf, "* ");
      break;

    case PM_ASN_RANGE:
      buffer_print(buf, "%u..%u ", p->val, p->val2);
      break;

    case PM_ASN_EXPR:
      ASSERT(0);
    }

    p = p->next;
  }

  buffer_puts(buf, "=]");
}

static inline int val_is_ip4(const struct f_val v)
{ return (v.type == T_IP) && ipa_is_ip4(v.val.ip); }

static inline int
lcomm_cmp(lcomm v1, lcomm v2)
{
  if (v1.asn != v2.asn)
    return (v1.asn > v2.asn) ? 1 : -1;
  if (v1.ldp1 != v2.ldp1)
    return (v1.ldp1 > v2.ldp1) ? 1 : -1;
  if (v1.ldp2 != v2.ldp2)
    return (v1.ldp2 > v2.ldp2) ? 1 : -1;
  return 0;
}

/**
 * val_compare - compare two values
 * @v1: first value
 * @v2: second value
 *
 * Compares two values and returns -1, 0, 1 on <, =, > or CMP_ERROR on
 * error. Tree module relies on this giving consistent results so
 * that it can be used for building balanced trees.
 */
int
val_compare(struct f_val v1, struct f_val v2)
{
  if (v1.type != v2.type) {
    if (v1.type == T_VOID)	/* Hack for else */
      return -1;
    if (v2.type == T_VOID)
      return 1;

    /* IP->Quad implicit conversion */
    if ((v1.type == T_QUAD) && val_is_ip4(v2))
      return uint_cmp(v1.val.i, ipa_to_u32(v2.val.ip));
    if (val_is_ip4(v1) && (v2.type == T_QUAD))
      return uint_cmp(ipa_to_u32(v1.val.ip), v2.val.i);

    debug( "Types do not match in val_compare\n" );
    return CMP_ERROR;
  }

  switch (v1.type) {
  case T_VOID:
    return 0;
  case T_ENUM:
  case T_INT:
  case T_BOOL:
  case T_PAIR:
  case T_QUAD:
    return uint_cmp(v1.val.i, v2.val.i);
  case T_EC:
  case T_RD:
    return u64_cmp(v1.val.ec, v2.val.ec);
  case T_LC:
    return lcomm_cmp(v1.val.lc, v2.val.lc);
  case T_IP:
    return ipa_compare(v1.val.ip, v2.val.ip);
  case T_NET:
    return net_compare(v1.val.net, v2.val.net);
  case T_STRING:
    return strcmp(v1.val.s, v2.val.s);
  default:
    return CMP_ERROR;
  }
}

static int
pm_same(struct f_path_mask *m1, struct f_path_mask *m2)
{
  while (m1 && m2)
  {
    if (m1->kind != m2->kind)
      return 0;

    if (m1->kind == PM_ASN_EXPR)
    {
      if (!i_same((struct f_inst *) m1->val, (struct f_inst *) m2->val))
	return 0;
    }
    else
    {
      if ((m1->val != m2->val) || (m1->val2 != m2->val2))
	return 0;
    }

    m1 = m1->next;
    m2 = m2->next;
  }

  return !m1 && !m2;
}

/**
 * val_same - compare two values
 * @v1: first value
 * @v2: second value
 *
 * Compares two values and returns 1 if they are same and 0 if not.
 * Comparison of values of different types is valid and returns 0.
 */
int
val_same(struct f_val v1, struct f_val v2)
{
  int rc;

  rc = val_compare(v1, v2);
  if (rc != CMP_ERROR)
    return !rc;

  if (v1.type != v2.type)
    return 0;

  switch (v1.type) {
  case T_PATH_MASK:
    return pm_same(v1.val.path_mask, v2.val.path_mask);
  case T_PATH:
  case T_CLIST:
  case T_ECLIST:
  case T_LCLIST:
    return adata_same(v1.val.ad, v2.val.ad);
  case T_SET:
    return same_tree(v1.val.t, v2.val.t);
  case T_PREFIX_SET:
    return trie_same(v1.val.ti, v2.val.ti);
  default:
    bug("Invalid type in val_same(): %x", v1.type);
  }
}

static int
clist_set_type(struct f_tree *set, struct f_val *v)
{
  switch (set->from.type)
  {
  case T_PAIR:
    v->type = T_PAIR;
    return 1;

  case T_QUAD:
    v->type = T_QUAD;
    return 1;

  case T_IP:
    if (val_is_ip4(set->from) && val_is_ip4(set->to))
    {
      v->type = T_QUAD;
      return 1;
    }
    /* Fall through */
  default:
    v->type = T_VOID;
    return 0;
  }
}

static inline int
eclist_set_type(struct f_tree *set)
{ return set->from.type == T_EC; }

static inline int
lclist_set_type(struct f_tree *set)
{ return set->from.type == T_LC; }

static int
clist_match_set(struct adata *clist, struct f_tree *set)
{
  if (!clist)
    return 0;

  struct f_val v;
  if (!clist_set_type(set, &v))
    return CMP_ERROR;

  u32 *l = (u32 *) clist->data;
  u32 *end = l + clist->length/4;

  while (l < end) {
    v.val.i = *l++;
    if (find_tree(set, v))
      return 1;
  }
  return 0;
}

static int
eclist_match_set(struct adata *list, struct f_tree *set)
{
  if (!list)
    return 0;

  if (!eclist_set_type(set))
    return CMP_ERROR;

  struct f_val v;
  u32 *l = int_set_get_data(list);
  int len = int_set_get_size(list);
  int i;

  v.type = T_EC;
  for (i = 0; i < len; i += 2) {
    v.val.ec = ec_get(l, i);
    if (find_tree(set, v))
      return 1;
  }

  return 0;
}

static int
lclist_match_set(struct adata *list, struct f_tree *set)
{
  if (!list)
    return 0;

  if (!lclist_set_type(set))
    return CMP_ERROR;

  struct f_val v;
  u32 *l = int_set_get_data(list);
  int len = int_set_get_size(list);
  int i;

  v.type = T_LC;
  for (i = 0; i < len; i += 3) {
    v.val.lc = lc_get(l, i);
    if (find_tree(set, v))
      return 1;
  }

  return 0;
}

static struct adata *
clist_filter(struct linpool *pool, struct adata *list, struct f_val set, int pos)
{
  if (!list)
    return NULL;

  int tree = (set.type == T_SET);	/* 1 -> set is T_SET, 0 -> set is T_CLIST */
  struct f_val v;
  if (tree)
    clist_set_type(set.val.t, &v);
  else
    v.type = T_PAIR;

  int len = int_set_get_size(list);
  u32 *l = int_set_get_data(list);
  u32 tmp[len];
  u32 *k = tmp;
  u32 *end = l + len;

  while (l < end) {
    v.val.i = *l++;
    /* pos && member(val, set) || !pos && !member(val, set),  member() depends on tree */
    if ((tree ? !!find_tree(set.val.t, v) : int_set_contains(set.val.ad, v.val.i)) == pos)
      *k++ = v.val.i;
  }

  uint nl = (k - tmp) * sizeof(u32);
  if (nl == list->length)
    return list;

  struct adata *res = adata_empty(pool, nl);
  memcpy(res->data, tmp, nl);
  return res;
}

static struct adata *
eclist_filter(struct linpool *pool, struct adata *list, struct f_val set, int pos)
{
  if (!list)
    return NULL;

  int tree = (set.type == T_SET);	/* 1 -> set is T_SET, 0 -> set is T_CLIST */
  struct f_val v;

  int len = int_set_get_size(list);
  u32 *l = int_set_get_data(list);
  u32 tmp[len];
  u32 *k = tmp;
  int i;

  v.type = T_EC;
  for (i = 0; i < len; i += 2) {
    v.val.ec = ec_get(l, i);
    /* pos && member(val, set) || !pos && !member(val, set),  member() depends on tree */
    if ((tree ? !!find_tree(set.val.t, v) : ec_set_contains(set.val.ad, v.val.ec)) == pos) {
      *k++ = l[i];
      *k++ = l[i+1];
    }
  }

  uint nl = (k - tmp) * sizeof(u32);
  if (nl == list->length)
    return list;

  struct adata *res = adata_empty(pool, nl);
  memcpy(res->data, tmp, nl);
  return res;
}

static struct adata *
lclist_filter(struct linpool *pool, struct adata *list, struct f_val set, int pos)
{
  if (!list)
    return NULL;

  int tree = (set.type == T_SET);	/* 1 -> set is T_SET, 0 -> set is T_CLIST */
  struct f_val v;

  int len = int_set_get_size(list);
  u32 *l = int_set_get_data(list);
  u32 tmp[len];
  u32 *k = tmp;
  int i;

  v.type = T_LC;
  for (i = 0; i < len; i += 3) {
    v.val.lc = lc_get(l, i);
    /* pos && member(val, set) || !pos && !member(val, set),  member() depends on tree */
    if ((tree ? !!find_tree(set.val.t, v) : lc_set_contains(set.val.ad, v.val.lc)) == pos)
      k = lc_copy(k, l+i);
  }

  uint nl = (k - tmp) * sizeof(u32);
  if (nl == list->length)
    return list;

  struct adata *res = adata_empty(pool, nl);
  memcpy(res->data, tmp, nl);
  return res;
}

/**
 * val_in_range - implement |~| operator
 * @v1: element
 * @v2: set
 *
 * Checks if @v1 is element (|~| operator) of @v2.
 */
static int
val_in_range(struct f_val v1, struct f_val v2)
{
  if ((v1.type == T_PATH) && (v2.type == T_PATH_MASK))
    return as_path_match(v1.val.ad, v2.val.path_mask);

  if ((v1.type == T_INT) && (v2.type == T_PATH))
    return as_path_contains(v2.val.ad, v1.val.i, 1);

  if (((v1.type == T_PAIR) || (v1.type == T_QUAD)) && (v2.type == T_CLIST))
    return int_set_contains(v2.val.ad, v1.val.i);
  /* IP->Quad implicit conversion */
  if (val_is_ip4(v1) && (v2.type == T_CLIST))
    return int_set_contains(v2.val.ad, ipa_to_u32(v1.val.ip));

  if ((v1.type == T_EC) && (v2.type == T_ECLIST))
    return ec_set_contains(v2.val.ad, v1.val.ec);

  if ((v1.type == T_LC) && (v2.type == T_LCLIST))
    return lc_set_contains(v2.val.ad, v1.val.lc);

  if ((v1.type == T_STRING) && (v2.type == T_STRING))
    return patmatch(v2.val.s, v1.val.s);

  if ((v1.type == T_IP) && (v2.type == T_NET))
    return ipa_in_netX(v1.val.ip, v2.val.net);

  if ((v1.type == T_NET) && (v2.type == T_NET))
    return net_in_netX(v1.val.net, v2.val.net);

  if ((v1.type == T_NET) && (v2.type == T_PREFIX_SET))
    return trie_match_net(v2.val.ti, v1.val.net);

  if (v2.type != T_SET)
    return CMP_ERROR;

  /* With integrated Quad<->IP implicit conversion */
  if ((v1.type == v2.val.t->from.type) ||
      ((v1.type == T_QUAD) && val_is_ip4(v2.val.t->from) && val_is_ip4(v2.val.t->to)))
    return !!find_tree(v2.val.t, v1);

  if (v1.type == T_CLIST)
    return clist_match_set(v1.val.ad, v2.val.t);

  if (v1.type == T_ECLIST)
    return eclist_match_set(v1.val.ad, v2.val.t);

  if (v1.type == T_LCLIST)
    return lclist_match_set(v1.val.ad, v2.val.t);

  if (v1.type == T_PATH)
    return as_path_match_set(v1.val.ad, v2.val.t);

  return CMP_ERROR;
}

/*
 * val_format - format filter value
 */
void
val_format(struct f_val v, buffer *buf)
{
  char buf2[1024];
  switch (v.type)
  {
  case T_VOID:	buffer_puts(buf, "(void)"); return;
  case T_BOOL:	buffer_puts(buf, v.val.i ? "TRUE" : "FALSE"); return;
  case T_INT:	buffer_print(buf, "%u", v.val.i); return;
  case T_STRING: buffer_print(buf, "%s", v.val.s); return;
  case T_IP:	buffer_print(buf, "%I", v.val.ip); return;
  case T_NET:   buffer_print(buf, "%N", v.val.net); return;
  case T_PAIR:	buffer_print(buf, "(%u,%u)", v.val.i >> 16, v.val.i & 0xffff); return;
  case T_QUAD:	buffer_print(buf, "%R", v.val.i); return;
  case T_EC:	ec_format(buf2, v.val.ec); buffer_print(buf, "%s", buf2); return;
  case T_LC:	lc_format(buf2, v.val.lc); buffer_print(buf, "%s", buf2); return;
  case T_RD:	rd_format(v.val.ec, buf2, 1024); buffer_print(buf, "%s", buf2); return;
  case T_PREFIX_SET: trie_format(v.val.ti, buf); return;
  case T_SET:	tree_format(v.val.t, buf); return;
  case T_ENUM:	buffer_print(buf, "(enum %x)%u", v.type, v.val.i); return;
  case T_PATH:	as_path_format(v.val.ad, buf2, 1000); buffer_print(buf, "(path %s)", buf2); return;
  case T_CLIST:	int_set_format(v.val.ad, 1, -1, buf2, 1000); buffer_print(buf, "(clist %s)", buf2); return;
  case T_ECLIST: ec_set_format(v.val.ad, -1, buf2, 1000); buffer_print(buf, "(eclist %s)", buf2); return;
  case T_LCLIST: lc_set_format(v.val.ad, -1, buf2, 1000); buffer_print(buf, "(lclist %s)", buf2); return;
  case T_PATH_MASK: pm_format(v.val.path_mask, buf); return;
  default:	buffer_print(buf, "[unknown type %x]", v.type); return;
  }
}

static struct rte **f_rte;
static struct rta *f_old_rta;
static struct ea_list **f_eattrs;
static struct linpool *f_pool;
static struct buffer f_buf;
static int f_flags;

static inline void f_cache_eattrs(void)
{
  f_eattrs = &((*f_rte)->attrs->eattrs);
}

static inline void f_rte_cow(void)
{
  if (!((*f_rte)->flags & REF_COW))
    return;

  *f_rte = rte_do_cow(*f_rte);
  f_eattrs = NULL;
}

/*
 * rta_cow - prepare rta for modification by filter
 */
static void
f_rta_cow(void)
{
  if (!rta_is_cached((*f_rte)->attrs))
    return;

  /* Prepare to modify rte */
  f_rte_cow();

  /* Store old rta to free it later, it stores reference from rte_cow() */
  f_old_rta = (*f_rte)->attrs;

  /*
   * Get shallow copy of rta. Fields eattrs and nexthops of rta are shared
   * with f_old_rta (they will be copied when the cached rta will be obtained
   * at the end of f_run()), also the lock of hostentry is inherited (we
   * suppose hostentry is not changed by filters).
   */
  (*f_rte)->attrs = rta_do_cow((*f_rte)->attrs, f_pool);

  /* Re-cache the ea_list */
  f_cache_eattrs();
}

static char *
val_format_str(struct f_val v) {
  buffer b;
  LOG_BUFFER_INIT(b);
  val_format(v, &b);
  return lp_strdup(f_pool, b.start);
}

static struct tbf rl_runtime_err = TBF_DEFAULT_LOG_LIMITS;

#define runtime(fmt, ...) do { \
    if (!(f_flags & FF_SILENT)) \
      log_rl(&rl_runtime_err, L_ERR "filters, line %d: " fmt, what->lineno, ##__VA_ARGS__); \
    res.type = T_RETURN; \
    res.val.i = F_ERROR; \
    return res; \
  } while(0)

#define ARG_ANY(n) INTERPRET(v##n, what->a##n.p)

#define ARG(n,t) ARG_ANY(n) \
    if (v##n.type != t) \
      runtime("Argument %d of instruction %s must be of type %02x, got %02x", \
	  n, f_instruction_name(what->fi_code), t, v##n.type);

#define INTERPRET(val, what_) \
    val = interpret(what_); \
    if (val.type & T_RETURN) \
      return val;

#define ACCESS_RTE \
  do { if (!f_rte) runtime("No route to access"); else f_cache_eattrs(); } while (0)

#define ACCESS_EATTRS \
  do { if (!f_eattrs) f_cache_eattrs(); } while (0)

#define BITFIELD_MASK(what) \
  (1u << (what->a2.i >> 24))

/**
 * interpret
 * @what: filter to interpret
 *
 * Interpret given tree of filter instructions. This is core function
 * of filter system and does all the hard work.
 *
 * Each instruction has 4 fields: code (which is instruction code),
 * aux (which is extension to instruction code, typically type),
 * arg1 and arg2 - arguments. Depending on instruction, arguments
 * are either integers, or pointers to instruction trees. Common
 * instructions like +, that have two expressions as arguments use
 * TWOARGS macro to get both of them evaluated.
 *
 * &f_val structures are copied around, so there are no problems with
 * memory managment.
 */
static struct f_val
interpret(struct f_inst *what)
{
  struct symbol *sym;
  struct f_val v1, v2, v3, res = { .type = T_VOID }, *vp;
  unsigned u1, u2;
  int i;
  u32 as;

  for ( ; what; what = what->next) {
  res.type = T_VOID;
  switch(what->fi_code) {
/* Binary operators */
  case FI_ADD:
    ARG(1,T_INT);
    ARG(2,T_INT);
    res.type = T_INT;
    res.val.i = v1.val.i + v2.val.i;
    break;
  case FI_SUBTRACT:
    ARG(1,T_INT);
    ARG(2,T_INT);
    res.type = T_INT;
    res.val.i = v1.val.i - v2.val.i;
    break;
  case FI_MULTIPLY:
    ARG(1,T_INT);
    ARG(2,T_INT);
    res.type = T_INT;
    res.val.i = v1.val.i * v2.val.i;
    break;
  case FI_DIVIDE:
    ARG(1,T_INT);
    ARG(2,T_INT);
    res.type = T_INT;
    if (v2.val.i == 0) runtime( "Mother told me not to divide by 0" );
    res.val.i = v1.val.i / v2.val.i;
    break;
  case FI_AND:
  case FI_OR:
    ARG(1,T_BOOL);
    if (v1.val.i == (what->fi_code == FI_OR)) {
      res.type = T_BOOL;
      res.val.i = v1.val.i;
    } else {
      ARG(2,T_BOOL);
      res = v2;
    }
    break;
  case FI_PAIR_CONSTRUCT:
    ARG(1,T_INT);
    ARG(2,T_INT);
    u1 = v1.val.i;
    u2 = v2.val.i;
    if ((u1 > 0xFFFF) || (u2 > 0xFFFF))
      runtime( "Can't operate with value out of bounds in pair constructor" );
    res.val.i = (u1 << 16) | u2;
    res.type = T_PAIR;
    break;

  case FI_EC_CONSTRUCT:
    {
      ARG_ANY(1);
      ARG(2, T_INT);

      int check, ipv4_used;
      u32 key, val;

      if (v1.type == T_INT) {
	ipv4_used = 0; key = v1.val.i;
      }
      else if (v1.type == T_QUAD) {
	ipv4_used = 1; key = v1.val.i;
      }
      /* IP->Quad implicit conversion */
      else if (val_is_ip4(v1)) {
	ipv4_used = 1; key = ipa_to_u32(v1.val.ip);
      }
      else
	runtime("Can't operate with key of non-integer/IPv4 type in EC constructor");

      val = v2.val.i;

      /* XXXX */
      res.type = T_EC;

      if (what->aux == EC_GENERIC) {
	check = 0; res.val.ec = ec_generic(key, val);
      }
      else if (ipv4_used) {
	check = 1; res.val.ec = ec_ip4(what->aux, key, val);
      }
      else if (key < 0x10000) {
	check = 0; res.val.ec = ec_as2(what->aux, key, val);
      }
      else {
	check = 1; res.val.ec = ec_as4(what->aux, key, val);
      }

      if (check && (val > 0xFFFF))
	runtime("Can't operate with value out of bounds in EC constructor");

      break;
    }

  case FI_LC_CONSTRUCT:
    {
      ARG(1, T_INT);
      ARG(2, T_INT);
      ARG(3, T_INT);

      res.type = T_LC;
      res.val.lc = (lcomm) { v1.val.i, v2.val.i, v3.val.i };

      break;
    }

  case FI_PATHMASK_CONSTRUCT:
    {
      struct f_path_mask *tt = what->a1.p, *vbegin, **vv = &vbegin;

      while (tt) {
	*vv = lp_alloc(f_pool, sizeof(struct f_path_mask));
	if (tt->kind == PM_ASN_EXPR) {
	  struct f_val res;
	  INTERPRET(res, (struct f_inst *) tt->val);
	  (*vv)->kind = PM_ASN;
	  if (res.type != T_INT) {
	    runtime( "Error resolving path mask template: value not an integer" );
	    return (struct f_val) { .type = T_VOID };
	  }

	  (*vv)->val = res.val.i;
	} else {
	  **vv = *tt;
	}
	tt = tt->next;
	vv = &((*vv)->next);
      }

      res = (struct f_val) { .type = T_PATH_MASK, .val.path_mask = vbegin };
      break;
    }

/* Relational operators */

#define COMPARE(x) \
    ARG_ANY(1); \
    ARG_ANY(2); \
    i = val_compare(v1, v2); \
    if (i==CMP_ERROR) \
      runtime( "Can't compare values of incompatible types" ); \
    res.type = T_BOOL; \
    res.val.i = (x); \
    break;

#define SAME(x) \
    ARG_ANY(1); \
    ARG_ANY(2); \
    i = val_same(v1, v2); \
    res.type = T_BOOL; \
    res.val.i = (x); \
    break;

  case FI_NEQ: SAME(!i);
  case FI_EQ: SAME(i);
  case FI_LT: COMPARE(i==-1);
  case FI_LTE: COMPARE(i!=1);

  case FI_NOT:
    ARG(1,T_BOOL);
    res = v1;
    res.val.i = !res.val.i;
    break;

  case FI_MATCH:
    ARG_ANY(1);
    ARG_ANY(2);
    res.type = T_BOOL;
    res.val.i = val_in_range(v1, v2);
    if (res.val.i == CMP_ERROR)
      runtime( "~ applied on unknown type pair" );
    res.val.i = !!res.val.i;
    break;

  case FI_NOT_MATCH:
    ARG_ANY(1);
    ARG_ANY(2);
    res.type = T_BOOL;
    res.val.i = val_in_range(v1, v2);
    if (res.val.i == CMP_ERROR)
      runtime( "!~ applied on unknown type pair" );
    res.val.i = !res.val.i;
    break;

  case FI_DEFINED:
    ARG_ANY(1);
    res.type = T_BOOL;
    res.val.i = (v1.type != T_VOID) && !undef_value(v1);
    break;
  case FI_TYPE:
    ARG_ANY(1); /* There may be more types supporting this operation */
    switch (v1.type)
    {
      case T_NET:
	res.type = T_ENUM_NETTYPE;
	res.val.i = v1.val.net->type;
	break;
      default:
	runtime( "Can't determine type of this item" );
    }
    break;
  case FI_IS_V4:
    ARG(1, T_IP);
    res.type = T_BOOL;
    res.val.i = ipa_is_ip4(v1.val.ip);
    break;

  /* Set to indirect value, a1 = variable, a2 = value */
  case FI_SET:
    ARG_ANY(2);
    sym = what->a1.p;
    vp = sym->def;
    if ((sym->class != (SYM_VARIABLE | v2.type)) && (v2.type != T_VOID))
    {
      /* IP->Quad implicit conversion */
      if ((sym->class == (SYM_VARIABLE | T_QUAD)) && val_is_ip4(v2))
      {
	vp->type = T_QUAD;
	vp->val.i = ipa_to_u32(v2.val.ip);
	break;
      }
      runtime( "Assigning to variable of incompatible type" );
    }
    *vp = v2;
    break;

    /* some constants have value in a2, some in *a1.p, strange. */
  case FI_CONSTANT:	/* integer (or simple type) constant, string, set, or prefix_set */
    res.type = what->aux;

    if (res.type == T_PREFIX_SET)
      res.val.ti = what->a2.p;
    else if (res.type == T_SET)
      res.val.t = what->a2.p;
    else if (res.type == T_STRING)
      res.val.s = what->a2.p;
    else
      res.val.i = what->a2.i;
    break;
  case FI_VARIABLE:
  case FI_CONSTANT_INDIRECT:
    res = * ((struct f_val *) what->a1.p);
    break;
  case FI_PRINT:
    ARG_ANY(1);
    val_format(v1, &f_buf);
    break;
  case FI_CONDITION:	/* ? has really strange error value, so we can implement if ... else nicely :-) */
    ARG(1, T_BOOL);
    if (v1.val.i) {
      ARG_ANY(2);
      res.val.i = 0;
    } else
      res.val.i = 1;
    res.type = T_BOOL;
    break;
  case FI_NOP:
    debug( "No operation\n" );
    break;
  case FI_PRINT_AND_DIE:
    ARG_ANY(1);
    if ((what->a2.i == F_NOP || (what->a2.i != F_NONL && what->a1.p)) &&
	!(f_flags & FF_SILENT))
      log_commit(*L_INFO, &f_buf);

    switch (what->a2.i) {
    case F_QUITBIRD:
      die( "Filter asked me to die" );
    case F_ACCEPT:
      /* Should take care about turning ACCEPT into MODIFY */
    case F_ERROR:
    case F_REJECT:	/* FIXME (noncritical) Should print complete route along with reason to reject route */
      res.type = T_RETURN;
      res.val.i = what->a2.i;
      return res;	/* We have to return now, no more processing. */
    case F_NONL:
    case F_NOP:
      break;
    default:
      bug( "unknown return type: Can't happen");
    }
    break;
  case FI_RTA_GET:	/* rta access */
    {
      ACCESS_RTE;
      struct rta *rta = (*f_rte)->attrs;
      res.type = what->aux;

      switch (what->a2.i)
      {
      case SA_FROM:	res.val.ip = rta->from; break;
      case SA_GW:	res.val.ip = rta->nh.gw; break;
      case SA_NET:	res.val.net = (*f_rte)->net->n.addr; break;
      case SA_PROTO:	res.val.s = rta->src->proto->name; break;
      case SA_SOURCE:	res.val.i = rta->source; break;
      case SA_SCOPE:	res.val.i = rta->scope; break;
      case SA_DEST:	res.val.i = rta->dest; break;
      case SA_IFNAME:	res.val.s = rta->nh.iface ? rta->nh.iface->name : ""; break;
      case SA_IFINDEX:	res.val.i = rta->nh.iface ? rta->nh.iface->index : 0; break;

      default:
	bug("Invalid static attribute access (%x)", res.type);
      }
    }
    break;
  case FI_RTA_SET:
    ACCESS_RTE;
    ARG_ANY(1);
    if (what->aux != v1.type)
      runtime( "Attempt to set static attribute to incompatible type" );

    f_rta_cow();
    {
      struct rta *rta = (*f_rte)->attrs;

      switch (what->a2.i)
      {
      case SA_FROM:
	rta->from = v1.val.ip;
	break;

      case SA_GW:
	{
	  ip_addr ip = v1.val.ip;
	  neighbor *n = neigh_find(rta->src->proto, &ip, 0);
	  if (!n || (n->scope == SCOPE_HOST))
	    runtime( "Invalid gw address" );

	  rta->dest = RTD_UNICAST;
	  rta->nh.gw = ip;
	  rta->nh.iface = n->iface;
	  rta->nh.next = NULL;
	  rta->hostentry = NULL;
	}
	break;

      case SA_SCOPE:
	rta->scope = v1.val.i;
	break;

      case SA_DEST:
	i = v1.val.i;
	if ((i != RTD_BLACKHOLE) && (i != RTD_UNREACHABLE) && (i != RTD_PROHIBIT))
	  runtime( "Destination can be changed only to blackhole, unreachable or prohibit" );

	rta->dest = i;
	rta->nh.gw = IPA_NONE;
	rta->nh.iface = NULL;
	rta->nh.next = NULL;
	rta->hostentry = NULL;
	break;

      default:
	bug("Invalid static attribute access (%x)", res.type);
      }
    }
    break;
  case FI_EA_GET:	/* Access to extended attributes */
    ACCESS_RTE;
    ACCESS_EATTRS;
    {
      u16 code = what->a2.i;
      int f_type = what->aux >> 8;
      eattr *e = ea_find(*f_eattrs, code);

      if (!e) {
	/* A special case: undefined as_path looks like empty as_path */
	if ((what->aux & EAF_TYPE_MASK) == EAF_TYPE_AS_PATH) {
	  res.type = T_PATH;
	  res.val.ad = &undef_adata;
	  break;
	}

	/* The same special case for int_set */
	if ((what->aux & EAF_TYPE_MASK) == EAF_TYPE_INT_SET) {
	  res.type = T_CLIST;
	  res.val.ad = &undef_adata;
	  break;
	}

	/* The same special case for ec_set */
	if ((what->aux & EAF_TYPE_MASK) == EAF_TYPE_EC_SET) {
	  res.type = T_ECLIST;
	  res.val.ad = &undef_adata;
	  break;
	}

	/* The same special case for lc_set */
	if ((what->aux & EAF_TYPE_MASK) == EAF_TYPE_LC_SET) {
	  res.type = T_LCLIST;
	  res.val.ad = &undef_adata;
	  break;
	}

	/* Undefined value */
	res.type = T_VOID;
	break;
      }

      switch (what->aux & EAF_TYPE_MASK) {
      case EAF_TYPE_INT:
	res.type = f_type;
	res.val.i = e->u.data;
	break;
      case EAF_TYPE_ROUTER_ID:
	res.type = T_QUAD;
	res.val.i = e->u.data;
	break;
      case EAF_TYPE_OPAQUE:
	res.type = T_ENUM_EMPTY;
	res.val.i = 0;
	break;
      case EAF_TYPE_IP_ADDRESS:
	res.type = T_IP;
	struct adata * ad = e->u.ptr;
	res.val.ip = * (ip_addr *) ad->data;
	break;
      case EAF_TYPE_AS_PATH:
        res.type = T_PATH;
	res.val.ad = e->u.ptr;
	break;
      case EAF_TYPE_BITFIELD:
	res.type = T_BOOL;
	res.val.i = !!(e->u.data & BITFIELD_MASK(what));
	break;
      case EAF_TYPE_INT_SET:
	res.type = T_CLIST;
	res.val.ad = e->u.ptr;
	break;
      case EAF_TYPE_EC_SET:
	res.type = T_ECLIST;
	res.val.ad = e->u.ptr;
	break;
      case EAF_TYPE_LC_SET:
	res.type = T_LCLIST;
	res.val.ad = e->u.ptr;
	break;
      case EAF_TYPE_UNDEF:
	res.type = T_VOID;
	break;
      default:
	bug("Unknown type in e,a");
      }
    }
    break;
  case FI_EA_SET:
    ACCESS_RTE;
    ACCESS_EATTRS;
    ARG_ANY(1);
    {
      struct ea_list *l = lp_alloc(f_pool, sizeof(struct ea_list) + sizeof(eattr));
      u16 code = what->a2.i;
      int f_type = what->aux >> 8;

      l->next = NULL;
      l->flags = EALF_SORTED;
      l->count = 1;
      l->attrs[0].id = code;
      l->attrs[0].flags = 0;
      l->attrs[0].type = (what->aux & 0xff) | EAF_ORIGINATED | EAF_FRESH;

      switch (what->aux & EAF_TYPE_MASK) {
      case EAF_TYPE_INT:
	if (v1.type != f_type)
	  runtime( "Setting int attribute to non-int value" );
	l->attrs[0].u.data = v1.val.i;
	break;

      case EAF_TYPE_ROUTER_ID:
	/* IP->Quad implicit conversion */
	if (val_is_ip4(v1)) {
	  l->attrs[0].u.data = ipa_to_u32(v1.val.ip);
	  break;
	}
	/* T_INT for backward compatibility */
	if ((v1.type != T_QUAD) && (v1.type != T_INT))
	  runtime( "Setting quad attribute to non-quad value" );
	l->attrs[0].u.data = v1.val.i;
	break;

      case EAF_TYPE_OPAQUE:
	runtime( "Setting opaque attribute is not allowed" );
	break;
      case EAF_TYPE_IP_ADDRESS:
	if (v1.type != T_IP)
	  runtime( "Setting ip attribute to non-ip value" );
	int len = sizeof(ip_addr);
	struct adata *ad = lp_alloc(f_pool, sizeof(struct adata) + len);
	ad->length = len;
	(* (ip_addr *) ad->data) = v1.val.ip;
	l->attrs[0].u.ptr = ad;
	break;
      case EAF_TYPE_AS_PATH:
	if (v1.type != T_PATH)
	  runtime( "Setting path attribute to non-path value" );
	l->attrs[0].u.ptr = v1.val.ad;
	break;
      case EAF_TYPE_BITFIELD:
	if (v1.type != T_BOOL)
	  runtime( "Setting bit in bitfield attribute to non-bool value" );
	{
	  /* First, we have to find the old value */
	  eattr *e = ea_find(*f_eattrs, code);
	  u32 data = e ? e->u.data : 0;

	  if (v1.val.i)
	    l->attrs[0].u.data = data | BITFIELD_MASK(what);
	  else
	    l->attrs[0].u.data = data & ~BITFIELD_MASK(what);;
	}
	break;
      case EAF_TYPE_INT_SET:
	if (v1.type != T_CLIST)
	  runtime( "Setting clist attribute to non-clist value" );
	l->attrs[0].u.ptr = v1.val.ad;
	break;
      case EAF_TYPE_EC_SET:
	if (v1.type != T_ECLIST)
	  runtime( "Setting eclist attribute to non-eclist value" );
	l->attrs[0].u.ptr = v1.val.ad;
	break;
      case EAF_TYPE_LC_SET:
	if (v1.type != T_LCLIST)
	  runtime( "Setting lclist attribute to non-lclist value" );
	l->attrs[0].u.ptr = v1.val.ad;
	break;
      case EAF_TYPE_UNDEF:
	if (v1.type != T_VOID)
	  runtime( "Setting void attribute to non-void value" );
	l->attrs[0].u.data = 0;
	break;
      default: bug("Unknown type in e,S");
      }

      f_rta_cow();
      l->next = *f_eattrs;
      *f_eattrs = l;
    }
    break;
  case FI_PREF_GET:
    ACCESS_RTE;
    res.type = T_INT;
    res.val.i = (*f_rte)->pref;
    break;
  case FI_PREF_SET:
    ACCESS_RTE;
    ARG(1,T_INT);
    if (v1.val.i > 0xFFFF)
      runtime( "Setting preference value out of bounds" );
    f_rte_cow();
    (*f_rte)->pref = v1.val.i;
    break;
  case FI_LENGTH:	/* Get length of */
    ARG_ANY(1);
    res.type = T_INT;
    switch(v1.type) {
    case T_NET:    res.val.i = net_pxlen(v1.val.net); break;
    case T_PATH:   res.val.i = as_path_getlen(v1.val.ad); break;
    case T_CLIST:  res.val.i = int_set_get_size(v1.val.ad); break;
    case T_ECLIST: res.val.i = ec_set_get_size(v1.val.ad); break;
    case T_LCLIST: res.val.i = lc_set_get_size(v1.val.ad); break;
    default: runtime( "Prefix, path, clist or eclist expected" );
    }
    break;
  case FI_SADR_SRC: 	/* Get SADR src prefix */
    ARG(1, T_NET);
    if (!net_is_sadr(v1.val.net))
      runtime( "SADR expected" );

    {
      net_addr_ip6_sadr *net = (void *) v1.val.net;
      net_addr *src = lp_alloc(f_pool, sizeof(net_addr_ip6));
      net_fill_ip6(src, net->src_prefix, net->src_pxlen);

      res.type = T_NET;
      res.val.net = src;
    }
    break;
  case FI_ROA_MAXLEN: 	/* Get ROA max prefix length */
    ARG(1, T_NET);
    if (!net_is_roa(v1.val.net))
      runtime( "ROA expected" );

    res.type = T_INT;
    res.val.i = (v1.val.net->type == NET_ROA4) ?
      ((net_addr_roa4 *) v1.val.net)->max_pxlen :
      ((net_addr_roa6 *) v1.val.net)->max_pxlen;
    break;
  case FI_ROA_ASN: 	/* Get ROA ASN */
    ARG(1, T_NET);
    if (!net_is_roa(v1.val.net))
      runtime( "ROA expected" );

    res.type = T_INT;
    res.val.i = (v1.val.net->type == NET_ROA4) ?
      ((net_addr_roa4 *) v1.val.net)->asn :
      ((net_addr_roa6 *) v1.val.net)->asn;
    break;
  case FI_IP:	/* Convert prefix to ... */
    ARG(1, T_NET);
    res.type = T_IP;
    res.val.ip = net_prefix(v1.val.net);
    break;
  case FI_ROUTE_DISTINGUISHER:
    ARG(1, T_NET);
    res.type = T_IP;
    if (!net_is_vpn(v1.val.net))
      runtime( "VPN address expected" );
    res.type = T_RD;
    res.val.ec = net_rd(v1.val.net);
    break;
  case FI_AS_PATH_FIRST:	/* Get first ASN from AS PATH */
    ARG(1, T_PATH);

    as = 0;
    as_path_get_first(v1.val.ad, &as);
    res.type = T_INT;
    res.val.i = as;
    break;
  case FI_AS_PATH_LAST:	/* Get last ASN from AS PATH */
    ARG(1, T_PATH);

    as = 0;
    as_path_get_last(v1.val.ad, &as);
    res.type = T_INT;
    res.val.i = as;
    break;
  case FI_AS_PATH_LAST_NAG:	/* Get last ASN from non-aggregated part of AS PATH */
    ARG(1, T_PATH);

    res.type = T_INT;
    res.val.i = as_path_get_last_nonaggregated(v1.val.ad);
    break;
  case FI_RETURN:
    ARG_ANY(1);
    res = v1;
    res.type |= T_RETURN;
    return res;
  case FI_CALL: /* CALL: this is special: if T_RETURN and returning some value, mask it out  */
    ARG_ANY(1);
    res = interpret(what->a2.p);
    if (res.type == T_RETURN)
      return res;
    res.type &= ~T_RETURN;
    break;
  case FI_CLEAR_LOCAL_VARS:	/* Clear local variables */
    for (sym = what->a1.p; sym != NULL; sym = sym->aux2)
      ((struct f_val *) sym->def)->type = T_VOID;
    break;
  case FI_SWITCH:
    ARG_ANY(1);
    {
      struct f_tree *t = find_tree(what->a2.p, v1);
      if (!t) {
	v1.type = T_VOID;
	t = find_tree(what->a2.p, v1);
	if (!t) {
	  debug( "No else statement?\n");
	  break;
	}
      }
      /* It is actually possible to have t->data NULL */

      INTERPRET(res, t->data);
    }
    break;
  case FI_IP_MASK: /* IP.MASK(val) */
    ARG(1, T_IP);
    ARG(2, T_INT);

    res.type = T_IP;
    res.val.ip = ipa_is_ip4(v1.val.ip) ?
      ipa_from_ip4(ip4_and(ipa_to_ip4(v1.val.ip), ip4_mkmask(v2.val.i))) :
      ipa_from_ip6(ip6_and(ipa_to_ip6(v1.val.ip), ip6_mkmask(v2.val.i)));
    break;

  case FI_EMPTY:	/* Create empty attribute */
    res.type = what->aux;
    res.val.ad = adata_empty(f_pool, 0);
    break;
  case FI_PATH_PREPEND:	/* Path prepend */
    ARG(1, T_PATH);
    ARG(2, T_INT);

    res.type = T_PATH;
    res.val.ad = as_path_prepend(f_pool, v1.val.ad, v2.val.i);
    break;

  case FI_CLIST_ADD_DEL:	/* (Extended) Community list add or delete */
    ARG_ANY(1);
    ARG_ANY(2);
    if (v1.type == T_PATH)
    {
      struct f_tree *set = NULL;
      u32 key = 0;
      int pos;

      if (v2.type == T_INT)
	key = v2.val.i;
      else if ((v2.type == T_SET) && (v2.val.t->from.type == T_INT))
	set = v2.val.t;
      else
	runtime("Can't delete non-integer (set)");

      switch (what->aux)
      {
      case 'a':	runtime("Can't add to path");
      case 'd':	pos = 0; break;
      case 'f':	pos = 1; break;
      default:	bug("unknown Ca operation");
      }

      if (pos && !set)
	runtime("Can't filter integer");

      res.type = T_PATH;
      res.val.ad = as_path_filter(f_pool, v1.val.ad, set, key, pos);
    }
    else if (v1.type == T_CLIST)
    {
      /* Community (or cluster) list */
      struct f_val dummy;
      int arg_set = 0;
      uint n = 0;

      if ((v2.type == T_PAIR) || (v2.type == T_QUAD))
	n = v2.val.i;
      /* IP->Quad implicit conversion */
      else if (val_is_ip4(v2))
	n = ipa_to_u32(v2.val.ip);
      else if ((v2.type == T_SET) && clist_set_type(v2.val.t, &dummy))
	arg_set = 1;
      else if (v2.type == T_CLIST)
	arg_set = 2;
      else
	runtime("Can't add/delete non-pair");

      res.type = T_CLIST;
      switch (what->aux)
      {
      case 'a':
	if (arg_set == 1)
	  runtime("Can't add set");
	else if (!arg_set)
	  res.val.ad = int_set_add(f_pool, v1.val.ad, n);
	else
	  res.val.ad = int_set_union(f_pool, v1.val.ad, v2.val.ad);
	break;

      case 'd':
	if (!arg_set)
	  res.val.ad = int_set_del(f_pool, v1.val.ad, n);
	else
	  res.val.ad = clist_filter(f_pool, v1.val.ad, v2, 0);
	break;

      case 'f':
	if (!arg_set)
	  runtime("Can't filter pair");
	res.val.ad = clist_filter(f_pool, v1.val.ad, v2, 1);
	break;

      default:
	bug("unknown Ca operation");
      }
    }
    else if (v1.type == T_ECLIST)
    {
      /* Extended community list */
      int arg_set = 0;

      /* v2.val is either EC or EC-set */
      if ((v2.type == T_SET) && eclist_set_type(v2.val.t))
	arg_set = 1;
      else if (v2.type == T_ECLIST)
	arg_set = 2;
      else if (v2.type != T_EC)
	runtime("Can't add/delete non-ec");

      res.type = T_ECLIST;
      switch (what->aux)
      {
      case 'a':
	if (arg_set == 1)
	  runtime("Can't add set");
	else if (!arg_set)
	  res.val.ad = ec_set_add(f_pool, v1.val.ad, v2.val.ec);
	else
	  res.val.ad = ec_set_union(f_pool, v1.val.ad, v2.val.ad);
	break;

      case 'd':
	if (!arg_set)
	  res.val.ad = ec_set_del(f_pool, v1.val.ad, v2.val.ec);
	else
	  res.val.ad = eclist_filter(f_pool, v1.val.ad, v2, 0);
	break;

      case 'f':
	if (!arg_set)
	  runtime("Can't filter ec");
	res.val.ad = eclist_filter(f_pool, v1.val.ad, v2, 1);
	break;

      default:
	bug("unknown Ca operation");
      }
    }
    else if (v1.type == T_LCLIST)
    {
      /* Large community list */
      int arg_set = 0;

      /* v2.val is either LC or LC-set */
      if ((v2.type == T_SET) && lclist_set_type(v2.val.t))
	arg_set = 1;
      else if (v2.type == T_LCLIST)
	arg_set = 2;
      else if (v2.type != T_LC)
	runtime("Can't add/delete non-lc");

      res.type = T_LCLIST;
      switch (what->aux)
      {
      case 'a':
	if (arg_set == 1)
	  runtime("Can't add set");
	else if (!arg_set)
	  res.val.ad = lc_set_add(f_pool, v1.val.ad, v2.val.lc);
	else
	  res.val.ad = lc_set_union(f_pool, v1.val.ad, v2.val.ad);
	break;

      case 'd':
	if (!arg_set)
	  res.val.ad = lc_set_del(f_pool, v1.val.ad, v2.val.lc);
	else
	  res.val.ad = lclist_filter(f_pool, v1.val.ad, v2, 0);
	break;

      case 'f':
	if (!arg_set)
	  runtime("Can't filter lc");
	res.val.ad = lclist_filter(f_pool, v1.val.ad, v2, 1);
	break;

      default:
	bug("unknown Ca operation");
      }
    }
    else
      runtime("Can't add/delete to non-[e|l]clist");

    break;

  case FI_ROA_CHECK:	/* ROA Check */
    if (what->arg1)
    {
      ARG(1, T_NET);
      ARG(2, T_INT);

      as = v2.val.i;
    }
    else
    {
      ACCESS_RTE;
      ACCESS_EATTRS;
      v1.val.net = (*f_rte)->net->n.addr;

      /* We ignore temporary attributes, probably not a problem here */
      /* 0x02 is a value of BA_AS_PATH, we don't want to include BGP headers */
      eattr *e = ea_find(*f_eattrs, EA_CODE(PROTOCOL_BGP, 0x02));

      if (!e || e->type != EAF_TYPE_AS_PATH)
	runtime("Missing AS_PATH attribute");

      as_path_get_last(e->u.ptr, &as);
    }

    struct rtable *table = ((struct f_inst_roa_check *) what)->rtc->table;
    if (!table)
      runtime("Missing ROA table");

    if (table->addr_type != NET_ROA4 && table->addr_type != NET_ROA6)
      runtime("Table type must be either ROA4 or ROA6");

    res.type = T_ENUM_ROA;

    if (table->addr_type != (v1.val.net->type == NET_IP4 ? NET_ROA4 : NET_ROA6))
      res.val.i = ROA_UNKNOWN; /* Prefix and table type mismatch */
    else
      res.val.i = net_roa_check(table, v1.val.net, as);

    break;

  case FI_FORMAT:	/* Format */
    ARG_ANY(1);

    res.type = T_STRING;
    res.val.s = val_format_str(v1);
    break;

  case FI_ASSERT:	/* Birdtest Assert */
    ARG(1, T_BOOL);

    res.type = v1.type;
    res.val = v1.val;

    CALL(bt_assert_hook, res.val.i, what);
    break;

  default:
    bug( "Unknown instruction %d (%c)", what->fi_code, what->fi_code & 0xff);
  }}
  return res;
}

#undef ARG
#undef ARG_ANY

#define ARG(n) \
	if (!i_same(f1->a##n.p, f2->a##n.p)) \
		return 0;

#define ONEARG		ARG(1);
#define TWOARGS		ONEARG; ARG(2);
#define THREEARGS	TWOARGS; ARG(3);

#define A2_SAME if (f1->a2.i != f2->a2.i) return 0;

/*
 * i_same - function that does real comparing of instruction trees, you should call filter_same from outside
 */
int
i_same(struct f_inst *f1, struct f_inst *f2)
{
  if ((!!f1) != (!!f2))
    return 0;
  if (!f1)
    return 1;
  if (f1->aux != f2->aux)
    return 0;
  if (f1->fi_code != f2->fi_code)
    return 0;
  if (f1 == f2)		/* It looks strange, but it is possible with call rewriting trickery */
    return 1;

  switch(f1->fi_code) {
  case FI_ADD: /* fall through */
  case FI_SUBTRACT:
  case FI_MULTIPLY:
  case FI_DIVIDE:
  case FI_OR:
  case FI_AND:
  case FI_PAIR_CONSTRUCT:
  case FI_EC_CONSTRUCT:
  case FI_NEQ:
  case FI_EQ:
  case FI_LT:
  case FI_LTE: TWOARGS; break;

  case FI_PATHMASK_CONSTRUCT: if (!pm_same(f1->a1.p, f2->a1.p)) return 0; break;

  case FI_NOT: ONEARG; break;
  case FI_NOT_MATCH:
  case FI_MATCH: TWOARGS; break;
  case FI_DEFINED: ONEARG; break;
  case FI_TYPE: ONEARG; break;

  case FI_LC_CONSTRUCT:
    THREEARGS;
    break;

  case FI_SET:
    ARG(2);
    {
      struct symbol *s1, *s2;
      s1 = f1->a1.p;
      s2 = f2->a1.p;
      if (strcmp(s1->name, s2->name))
	return 0;
      if (s1->class != s2->class)
	return 0;
    }
    break;

  case FI_CONSTANT:
    switch (f1->aux) {

    case T_PREFIX_SET:
      if (!trie_same(f1->a2.p, f2->a2.p))
	return 0;
      break;

    case T_SET:
      if (!same_tree(f1->a2.p, f2->a2.p))
	return 0;
      break;

    case T_STRING:
      if (strcmp(f1->a2.p, f2->a2.p))
	return 0;
      break;

    default:
      A2_SAME;
    }
    break;

  case FI_CONSTANT_INDIRECT:
    if (!val_same(* (struct f_val *) f1->a1.p, * (struct f_val *) f2->a1.p))
      return 0;
    break;

  case FI_VARIABLE:
    if (strcmp((char *) f1->a2.p, (char *) f2->a2.p))
      return 0;
    break;
  case FI_PRINT: case FI_LENGTH: ONEARG; break;
  case FI_CONDITION: TWOARGS; break;
  case FI_NOP: case FI_EMPTY: break;
  case FI_PRINT_AND_DIE: ONEARG; A2_SAME; break;
  case FI_PREF_GET:
  case FI_RTA_GET: A2_SAME; break;
  case FI_EA_GET: A2_SAME; break;
  case FI_PREF_SET:
  case FI_RTA_SET:
  case FI_EA_SET: ONEARG; A2_SAME; break;

  case FI_RETURN: ONEARG; break;
  case FI_ROA_MAXLEN: ONEARG; break;
  case FI_ROA_ASN: ONEARG; break;
  case FI_SADR_SRC: ONEARG; break;
  case FI_IP: ONEARG; break;
  case FI_IS_V4: ONEARG; break;
  case FI_ROUTE_DISTINGUISHER: ONEARG; break;
  case FI_CALL: /* Call rewriting trickery to avoid exponential behaviour */
             ONEARG;
	     if (!i_same(f1->a2.p, f2->a2.p))
	       return 0;
	     f2->a2.p = f1->a2.p;
	     break;
  case FI_CLEAR_LOCAL_VARS: break; /* internal instruction */
  case FI_SWITCH: ONEARG; if (!same_tree(f1->a2.p, f2->a2.p)) return 0; break;
  case FI_IP_MASK: TWOARGS; break;
  case FI_PATH_PREPEND: TWOARGS; break;
  case FI_CLIST_ADD_DEL: TWOARGS; break;
  case FI_AS_PATH_FIRST:
  case FI_AS_PATH_LAST:
  case FI_AS_PATH_LAST_NAG: ONEARG; break;
  case FI_ROA_CHECK:
    TWOARGS;
    /* Does not really make sense - ROA check results may change anyway */
    if (strcmp(((struct f_inst_roa_check *) f1)->rtc->name,
	       ((struct f_inst_roa_check *) f2)->rtc->name))
      return 0;
    break;
  case FI_FORMAT: ONEARG; break;
  case FI_ASSERT: ONEARG; break;
  default:
    bug( "Unknown instruction %d in same (%c)", f1->fi_code, f1->fi_code & 0xff);
  }
  return i_same(f1->next, f2->next);
}

/**
 * f_run - run a filter for a route
 * @filter: filter to run
 * @rte: route being filtered, may be modified
 * @tmp_pool: all filter allocations go from this pool
 * @flags: flags
 *
 * If filter needs to modify the route, there are several
 * posibilities. @rte might be read-only (with REF_COW flag), in that
 * case rw copy is obtained by rte_cow() and @rte is replaced. If
 * @rte is originally rw, it may be directly modified (and it is never
 * copied).
 *
 * The returned rte may reuse the (possibly cached, cloned) rta, or
 * (if rta was modificied) contains a modified uncached rta, which
 * uses parts allocated from @tmp_pool and parts shared from original
 * rta. There is one exception - if @rte is rw but contains a cached
 * rta and that is modified, rta in returned rte is also cached.
 *
 * Ownership of cached rtas is consistent with rte, i.e.
 * if a new rte is returned, it has its own clone of cached rta
 * (and cached rta of read-only source rte is intact), if rte is
 * modified in place, old cached rta is possibly freed.
 */
int
f_run(struct filter *filter, struct rte **rte, struct linpool *tmp_pool, int flags)
{
  if (filter == FILTER_ACCEPT)
    return F_ACCEPT;

  if (filter == FILTER_REJECT)
    return F_REJECT;

  int rte_cow = ((*rte)->flags & REF_COW);
  DBG( "Running filter `%s'...", filter->name );

  f_rte = rte;
  f_old_rta = NULL;
  f_pool = tmp_pool;
  f_flags = flags;

  LOG_BUFFER_INIT(f_buf);

  struct f_val res = interpret(filter->root);

  if (f_old_rta) {
    /*
     * Cached rta was modified and f_rte contains now an uncached one,
     * sharing some part with the cached one. The cached rta should
     * be freed (if rte was originally COW, f_old_rta is a clone
     * obtained during rte_cow()).
     *
     * This also implements the exception mentioned in f_run()
     * description. The reason for this is that rta reuses parts of
     * f_old_rta, and these may be freed during rta_free(f_old_rta).
     * This is not the problem if rte was COW, because original rte
     * also holds the same rta.
     */
    if (!rte_cow)
      (*f_rte)->attrs = rta_lookup((*f_rte)->attrs);

    rta_free(f_old_rta);
  }


  if (res.type != T_RETURN) {
    if (!(f_flags & FF_SILENT))
      log_rl(&rl_runtime_err, L_ERR "Filter %s did not return accept nor reject. Make up your mind", filter->name);
    return F_ERROR;
  }
  DBG( "done (%u)\n", res.val.i );
  return res.val.i;
}

/* TODO: perhaps we could integrate f_eval(), f_eval_rte() and f_run() */

struct f_val
f_eval_rte(struct f_inst *expr, struct rte **rte, struct linpool *tmp_pool)
{

  f_rte = rte;
  f_old_rta = NULL;
  f_pool = tmp_pool;
  f_flags = 0;

  LOG_BUFFER_INIT(f_buf);

  /* Note that in this function we assume that rte->attrs is private / uncached */
  struct f_val res = interpret(expr);

  return res;
}

struct f_val
f_eval(struct f_inst *expr, struct linpool *tmp_pool)
{
  f_flags = 0;
  f_rte = NULL;
  f_pool = tmp_pool;

  LOG_BUFFER_INIT(f_buf);

  return interpret(expr);
}

uint
f_eval_int(struct f_inst *expr)
{
  /* Called independently in parse-time to eval expressions */
  struct f_val res = f_eval(expr, cfg_mem);

  if (res.type != T_INT)
    cf_error("Integer expression expected");

  return res.val.i;
}

/**
 * filter_same - compare two filters
 * @new: first filter to be compared
 * @old: second filter to be compared, notice that this filter is
 * damaged while comparing.
 *
 * Returns 1 in case filters are same, otherwise 0. If there are
 * underlying bugs, it will rather say 0 on same filters than say
 * 1 on different.
 */
int
filter_same(struct filter *new, struct filter *old)
{
  if (old == new)	/* Handle FILTER_ACCEPT and FILTER_REJECT */
    return 1;
  if (old == FILTER_ACCEPT || old == FILTER_REJECT ||
      new == FILTER_ACCEPT || new == FILTER_REJECT)
    return 0;
  return i_same(new->root, old->root);
}