bird/filter/filter.c

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/*
* 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
*
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* 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|.
*
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* 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 (@a[0], @a[1]). Some instructions contain pointer(s) to other
* instructions in their (@a[0], @a[1]) fields.
*
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* 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"
#include "filter/f-inst.h"
#include "filter/data.h"
struct filter_stack {
/* Value stack for execution */
#define F_VAL_STACK_MAX 4096
uint vcnt; /* Current value stack size; 0 for empty */
uint ecnt; /* Current execute stack size; 0 for empty */
struct f_val vstk[F_VAL_STACK_MAX]; /* The stack itself */
/* Instruction stack for execution */
#define F_EXEC_STACK_MAX 4096
struct {
const struct f_line *line; /* The line that is being executed */
uint pos; /* Instruction index in the line */
uint ventry; /* Value stack depth on entry */
uint vbase; /* Where to index variable positions from */
enum f_exception emask; /* Exception mask */
} estk[F_EXEC_STACK_MAX];
};
/* Internal filter state, to be allocated on stack when executing filters */
struct filter_state {
/* Stacks needed for execution */
struct filter_stack *stack;
/* The route we are processing. This may be NULL to indicate no route available. */
struct rte **rte;
/* The old rta to be freed after filters are done. */
struct rta *old_rta;
/* Cached pointer to ea_list */
struct ea_list **eattrs;
/* Linpool for adata allocation */
struct linpool *pool;
/* Buffer for log output */
struct buffer buf;
/* Filter execution flags */
int flags;
};
#if HAVE_THREAD_LOCAL
_Thread_local static struct filter_state filter_state;
_Thread_local static struct filter_stack filter_stack;
#define FS_INIT(...) filter_state = (struct filter_state) { .stack = &filter_stack, __VA_ARGS__ }
#else
#define FS_INIT(...) struct filter_state filter_state = { .stack = alloca(sizeof(struct filter_stack)), __VA_ARGS__ };
#endif
void (*bt_assert_hook)(int result, const struct f_line_item *assert);
static inline void f_cache_eattrs(struct filter_state *fs)
{
fs->eattrs = &((*fs->rte)->attrs->eattrs);
}
static inline void f_rte_cow(struct filter_state *fs)
{
if (!((*fs->rte)->flags & REF_COW))
return;
*fs->rte = rte_cow(*fs->rte);
}
/*
* rta_cow - prepare rta for modification by filter
*/
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static void
f_rta_cow(struct filter_state *fs)
{
if (!rta_is_cached((*fs->rte)->attrs))
return;
/* Prepare to modify rte */
f_rte_cow(fs);
/* Store old rta to free it later, it stores reference from rte_cow() */
fs->old_rta = (*fs->rte)->attrs;
/*
* Get shallow copy of rta. Fields eattrs and nexthops of rta are shared
* with fs->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).
*/
(*fs->rte)->attrs = rta_do_cow((*fs->rte)->attrs, fs->pool);
/* Re-cache the ea_list */
f_cache_eattrs(fs);
}
static char *
val_format_str(struct filter_state *fs, const struct f_val *v) {
buffer b;
LOG_BUFFER_INIT(b);
val_format(v, &b);
return lp_strdup(fs->pool, b.start);
}
static struct tbf rl_runtime_err = TBF_DEFAULT_LOG_LIMITS;
#define runtime(fmt, ...) do { \
if (!(fs->flags & FF_SILENT)) \
log_rl(&rl_runtime_err, L_ERR "filters, line %d: " fmt, \
(fs->stack->estk[fs->stack->ecnt-1].line->items[fs->stack->estk[fs->stack->ecnt-1].pos-1]).lineno, \
##__VA_ARGS__); \
return F_ERROR; \
} while(0)
#define ACCESS_RTE do { if (!fs->rte) runtime("No route to access"); } while (0)
#define ACCESS_EATTRS do { if (!fs->eattrs) f_cache_eattrs(fs); } while (0)
static inline enum filter_return
f_rta_set(struct filter_state *fs, struct f_static_attr sa, const struct f_val *val)
{
ACCESS_RTE;
if (sa.f_type != val->type)
runtime( "Attempt to set static attribute to incompatible type" );
f_rta_cow(fs);
{
struct rta *rta = (*fs->rte)->attrs;
switch (sa.sa_code)
{
case SA_FROM:
rta->from = val->val.ip;
return F_NOP;
case SA_GW:
{
ip_addr ip = val->val.ip;
neighbor *n = neigh_find(rta->src->proto, ip, NULL, 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;
}
return F_NOP;
case SA_SCOPE:
rta->scope = val->val.i;
return F_NOP;
case SA_DEST:
{
int i = val->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;
}
return F_NOP;
case SA_IFNAME:
{
struct iface *ifa = if_find_by_name(val->val.s);
if (!ifa)
runtime( "Invalid iface name" );
rta->dest = RTD_UNICAST;
rta->nh.gw = IPA_NONE;
rta->nh.iface = ifa;
rta->nh.next = NULL;
rta->hostentry = NULL;
}
return F_NOP;
default:
bug("Invalid static attribute access (%u/%u)", sa.f_type, sa.sa_code);
}
}
}
static inline enum filter_return
f_ea_set(struct filter_state *fs, struct f_dynamic_attr da, const struct f_val *val)
{
ACCESS_RTE;
ACCESS_EATTRS;
{
struct ea_list *l = lp_alloc(fs->pool, sizeof(struct ea_list) + sizeof(eattr));
l->next = NULL;
l->flags = EALF_SORTED;
l->count = 1;
l->attrs[0].id = da.ea_code;
l->attrs[0].flags = 0;
l->attrs[0].type = da.type | EAF_ORIGINATED | EAF_FRESH;
switch (da.type) {
case EAF_TYPE_INT:
if (val->type != da.f_type)
runtime( "Setting int attribute to non-int value" );
l->attrs[0].u.data = val->val.i;
break;
case EAF_TYPE_ROUTER_ID:
/* IP->Quad implicit conversion */
if (val_is_ip4(val)) {
l->attrs[0].u.data = ipa_to_u32(val->val.ip);
break;
}
/* T_INT for backward compatibility */
if ((val->type != T_QUAD) && (val->type != T_INT))
runtime( "Setting quad attribute to non-quad value" );
l->attrs[0].u.data = val->val.i;
break;
case EAF_TYPE_OPAQUE:
runtime( "Setting opaque attribute is not allowed" );
break;
case EAF_TYPE_IP_ADDRESS:
if (val->type != T_IP)
runtime( "Setting ip attribute to non-ip value" );
int len = sizeof(ip_addr);
struct adata *ad = lp_alloc(fs->pool, sizeof(struct adata) + len);
ad->length = len;
(* (ip_addr *) ad->data) = val->val.ip;
l->attrs[0].u.ptr = ad;
break;
case EAF_TYPE_AS_PATH:
if (val->type != T_PATH)
runtime( "Setting path attribute to non-path value" );
l->attrs[0].u.ptr = val->val.ad;
break;
case EAF_TYPE_BITFIELD:
if (val->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(*fs->eattrs, da.ea_code);
u32 data = e ? e->u.data : 0;
if (val->val.i)
l->attrs[0].u.data = data | (1u << da.bit);
else
l->attrs[0].u.data = data & ~(1u << da.bit);
}
break;
case EAF_TYPE_INT_SET:
if (val->type != T_CLIST)
runtime( "Setting clist attribute to non-clist value" );
l->attrs[0].u.ptr = val->val.ad;
break;
case EAF_TYPE_EC_SET:
if (val->type != T_ECLIST)
runtime( "Setting eclist attribute to non-eclist value" );
l->attrs[0].u.ptr = val->val.ad;
break;
case EAF_TYPE_LC_SET:
if (val->type != T_LCLIST)
runtime( "Setting lclist attribute to non-lclist value" );
l->attrs[0].u.ptr = val->val.ad;
break;
default: bug("Unknown type in e,S");
}
f_rta_cow(fs);
l->next = *fs->eattrs;
*fs->eattrs = l;
return F_NOP;
}
}
static inline enum filter_return
f_lval_set(struct filter_state *fs, const struct f_lval *lv, const struct f_val *val)
{
switch (lv->type) {
case F_LVAL_STACK:
fs->stack->vstk[fs->stack->vcnt] = *val;
fs->stack->vcnt++;
return F_NOP;
case F_LVAL_EXCEPTION:
{
/* Drop every sub-block including ourselves */
while ((fs->stack->ecnt-- > 0) && !(fs->stack->estk[fs->stack->ecnt].emask & lv->exception))
;
/* Now we are at the catch frame; if no such, try to convert to accept/reject. */
if (!fs->stack->ecnt)
if (lv->exception == FE_RETURN)
if (val->type == T_BOOL)
if (val->val.i)
return F_ACCEPT;
else
return F_REJECT;
else
runtime("Can't return non-bool from non-function");
else
runtime("Unhandled exception 0x%x: %s", lv->exception, val_format_str(fs, val));
/* Set the value stack position, overwriting the former implicit void */
fs->stack->vcnt = fs->stack->estk[fs->stack->ecnt].ventry;
/* Copy the return value */
fs->stack->vstk[fs->stack->vcnt - 1] = *val;
return F_NOP;
}
case F_LVAL_VARIABLE:
fs->stack->vstk[fs->stack->estk[fs->stack->ecnt-1].vbase + lv->sym->offset] = *val;
return F_NOP;
case F_LVAL_PREFERENCE:
ACCESS_RTE;
if (val->type != T_INT)
runtime("Preference must be integer, got 0x%02x", val->type);
if (val->val.i > 0xFFFF)
runtime("Preference is at most 65536");
f_rte_cow(fs);
(*fs->rte)->pref = val->val.i;
return F_NOP;
case F_LVAL_SA:
return f_rta_set(fs, lv->sa, val);
case F_LVAL_EA:
return f_ea_set(fs, lv->da, val);
default:
bug("This shall never happen");
}
}
/**
* interpret
* @fs: filter state
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* @what: filter to interpret
*
* Interpret given tree of filter instructions. This is core function
* of filter system and does all the hard work.
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*
* 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
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* are either integers, or pointers to instruction trees. Common
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* instructions like +, that have two expressions as arguments use
* TWOARGS macro to get both of them evaluated.
*/
static enum filter_return
interpret(struct filter_state *fs, const struct f_line *line, struct f_val *val)
{
/* No arguments allowed */
ASSERT(line->args == 0);
/* Initialize the filter stack */
struct filter_stack *fstk = fs->stack;
fstk->vcnt = line->vars;
memset(fstk->vstk, 0, sizeof(struct f_val) * line->vars);
/* The same as with the value stack. Not resetting the stack for performance reasons. */
fstk->ecnt = 1;
fstk->estk[0].line = line;
fstk->estk[0].pos = 0;
#define curline fstk->estk[fstk->ecnt-1]
#if DEBUGGING
debug("Interpreting line.");
f_dump_line(line, 1);
#endif
while (fstk->ecnt > 0) {
while (curline.pos < curline.line->len) {
const struct f_line_item *what = &(curline.line->items[curline.pos++]);
switch (what->fi_code) {
#define res fstk->vstk[fstk->vcnt]
#define v1 fstk->vstk[fstk->vcnt]
#define v2 fstk->vstk[fstk->vcnt + 1]
#define v3 fstk->vstk[fstk->vcnt + 2]
#include "filter/inst-interpret.c"
#undef res
#undef v1
#undef v2
#undef v3
#undef runtime
#undef ACCESS_RTE
#undef ACCESS_EATTRS
}
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}
/* End of current line. Drop local variables before exiting. */
fstk->vcnt -= curline.line->vars;
fstk->vcnt -= curline.line->args;
fstk->ecnt--;
/* If the caller wants to store the result somewhere, do it. */
if (fstk->ecnt) {
const struct f_line_item *caller = &(curline.line->items[curline.pos-1]);
if (caller->result.type != F_LVAL_STACK) {
enum filter_return fret = f_lval_set(fs, &(caller->result), &fstk->vstk[--fstk->vcnt]);
if (fret != F_NOP)
return fret;
}
}
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}
if (fstk->vcnt == 0) {
if (val) {
log_rl(&rl_runtime_err, L_ERR "filters: No value left on stack");
return F_ERROR;
}
return F_NOP;
}
if (val && (fstk->vcnt == 1)) {
*val = fstk->vstk[0];
return F_NOP;
}
log_rl(&rl_runtime_err, L_ERR "Too many items left on stack: %u", fstk->vcnt);
return F_ERROR;
}
/**
* 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 modified) 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.
*/
enum filter_return
f_run(const 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 );
/* Initialize the filter state */
FS_INIT(
.rte = rte,
.pool = tmp_pool,
.flags = flags,
);
LOG_BUFFER_INIT(filter_state.buf);
/* Run the interpreter itself */
enum filter_return fret = interpret(&filter_state, filter->root, NULL);
if (filter_state.old_rta) {
/*
* Cached rta was modified and filter_state->rte contains now an uncached one,
* sharing some part with the cached one. The cached rta should
* be freed (if rte was originally COW, filter_state->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
* filter_state->old_rta, and these may be freed during rta_free(filter_state->old_rta).
* This is not the problem if rte was COW, because original rte
* also holds the same rta.
*/
if (!rte_cow) {
/* Cache the new attrs */
(*filter_state.rte)->attrs = rta_lookup((*filter_state.rte)->attrs);
/* Drop cached ea_list pointer */
filter_state.eattrs = NULL;
}
/* Uncache the old attrs and drop the pointer as it is invalid now. */
rta_free(filter_state.old_rta);
filter_state.old_rta = NULL;
}
/* Process the filter output, log it and return */
if (fret < F_ACCEPT) {
if (!(filter_state.flags & FF_SILENT))
log_rl(&rl_runtime_err, L_ERR "Filter %s did not return accept nor reject. Make up your mind", filter_name(filter));
return F_ERROR;
}
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DBG( "done (%u)\n", res.val.i );
return fret;
}
/**
* f_eval_rte run a filter line for an uncached route
* @expr: filter line to run
* @rte: route being filtered, may be modified
* @tmp_pool: all filter allocations go from this pool
*
* This specific filter entry point runs the given filter line
* (which must not have any arguments) on the given route.
*
* The route MUST NOT have REF_COW set and its attributes MUST NOT
* be cached by rta_lookup().
*/
enum filter_return
f_eval_rte(const struct f_line *expr, struct rte **rte, struct linpool *tmp_pool)
{
FS_INIT(
.rte = rte,
.pool = tmp_pool,
);
LOG_BUFFER_INIT(filter_state.buf);
ASSERT(!((*rte)->flags & REF_COW));
ASSERT(!rta_is_cached((*rte)->attrs));
return interpret(&filter_state, expr, NULL);
}
/*
* f_eval get a value of a term
* @expr: filter line containing the term
* @tmp_pool: long data may get allocated from this pool
* @pres: here the output will be stored
*/
enum filter_return
f_eval(const struct f_line *expr, struct linpool *tmp_pool, struct f_val *pres)
{
FS_INIT(
.pool = tmp_pool,
);
LOG_BUFFER_INIT(filter_state.buf);
enum filter_return fret = interpret(&filter_state, expr, pres);
return fret;
}
/*
* f_eval_int get an integer value of a term
* Called internally from the config parser, uses its internal memory pool
* for allocations. Do not call in other cases.
*/
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uint
f_eval_int(const struct f_line *expr)
{
/* Called independently in parse-time to eval expressions */
FS_INIT(
.pool = cfg_mem,
);
struct f_val val;
LOG_BUFFER_INIT(filter_state.buf);
if (interpret(&filter_state, expr, &val) > F_RETURN)
cf_error("Runtime error while evaluating expression");
if (val.type != T_INT)
cf_error("Integer expression expected");
return val.val.i;
}
/*
* f_eval_buf get a value of a term and print it to the supplied buffer
*/
enum filter_return
f_eval_buf(const struct f_line *expr, struct linpool *tmp_pool, buffer *buf)
{
struct f_val val;
enum filter_return fret = f_eval(expr, tmp_pool, &val);
if (fret > F_RETURN)
val_format(&val, buf);
return fret;
}
/**
* filter_same - compare two filters
* @new: first filter to be compared
* @old: second filter to be compared
*
* 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(const struct filter *new, const 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;
if ((!old->sym) && (!new->sym))
return f_same(new->root, old->root);
if ((!old->sym) || (!new->sym))
return 0;
if (strcmp(old->sym->name, new->sym->name))
return 0;
return new->sym->flags & SYM_FLAG_SAME;
}
/**
* filter_commit - do filter comparisons on all the named functions and filters
*/
void
filter_commit(struct config *new, struct config *old)
{
if (!old)
return;
struct symbol *sym, *osym;
WALK_LIST(sym, new->symbols)
switch (sym->class) {
case SYM_FUNCTION:
if ((osym = cf_find_symbol(old, sym->name)) &&
(osym->class == SYM_FUNCTION) &&
f_same(sym->function, osym->function))
sym->flags |= SYM_FLAG_SAME;
else
sym->flags &= ~SYM_FLAG_SAME;
break;
case SYM_FILTER:
if ((osym = cf_find_symbol(old, sym->name)) &&
(osym->class == SYM_FILTER) &&
f_same(sym->filter->root, osym->filter->root))
sym->flags |= SYM_FLAG_SAME;
else
sym->flags &= ~SYM_FLAG_SAME;
break;
}
}