bird/filter/filter.c
Ondrej Zajicek (work) a2527ee53d Filter: Improve handling of stack frames in filter bytecode
When f_line is done, we have to pop the stack frame. The old code just
removed nominal number of args/vars. Change it to use stored ventry value
modified by number of returned values. This allows to allocate variables
on a stack frame during execution of f_lines instead of just at start.

But we need to know the number of returned values for a f_line. It is 1
for term, 0 for cmd. Store that to f_line during linearization.
2022-06-27 21:13:32 +02:00

513 lines
14 KiB
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, later translated
* into lists called &f_line. All the instructions are defined and documented
* in |filter/f-inst.c| definition file.
*
* Filters use a &f_val structure for their data. Each &f_val
* contains type and value (types are constants prefixed with %T_).
* Look into |filter/data.h| for more information and appropriate calls.
*/
#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/ip.h"
#include "lib/net.h"
#include "lib/flowspec.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"
/* Exception bits */
enum f_exception {
FE_RETURN = 0x1,
};
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;
};
_Thread_local static struct filter_state filter_state;
_Thread_local static struct filter_stack filter_stack;
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
*/
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 struct tbf rl_runtime_err = TBF_DEFAULT_LOG_LIMITS;
/**
* interpret
* @fs: filter state
* @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.
*/
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]
#ifdef LOCAL_DEBUG
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 vv(i) fstk->vstk[fstk->vcnt + (i)]
#define v1 vv(0)
#define v2 vv(1)
#define v3 vv(2)
#define runtime(fmt, ...) do { \
if (!(fs->flags & FF_SILENT)) \
log_rl(&rl_runtime_err, L_ERR "filters, line %d: " fmt, what->lineno, ##__VA_ARGS__); \
return F_ERROR; \
} while(0)
#define falloc(size) lp_alloc(fs->pool, size)
#define fpool fs->pool
#define ACCESS_EATTRS do { if (!fs->eattrs) f_cache_eattrs(fs); } while (0)
#include "filter/inst-interpret.c"
#undef res
#undef v1
#undef v2
#undef v3
#undef runtime
#undef falloc
#undef fpool
#undef ACCESS_EATTRS
}
}
/* End of current line. Drop local variables before exiting. */
fstk->vcnt = curline.ventry + curline.line->results;
fstk->ecnt--;
}
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 */
filter_state = (struct filter_state) {
.stack = &filter_stack,
.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;
}
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)
{
filter_state = (struct filter_state) {
.stack = &filter_stack,
.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)
{
filter_state = (struct filter_state) {
.stack = &filter_stack,
.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.
*/
uint
f_eval_int(const struct f_line *expr)
{
/* Called independently in parse-time to eval expressions */
filter_state = (struct filter_state) {
.stack = &filter_stack,
.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; see log for details");
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;
}
}
void filters_dump_all(void)
{
struct symbol *sym;
WALK_LIST(sym, config->symbols) {
switch (sym->class) {
case SYM_FILTER:
debug("Named filter %s:\n", sym->name);
f_dump_line(sym->filter->root, 1);
break;
case SYM_FUNCTION:
debug("Function %s:\n", sym->name);
f_dump_line(sym->function, 1);
break;
case SYM_PROTO:
{
debug("Protocol %s:\n", sym->name);
struct channel *c;
WALK_LIST(c, sym->proto->proto->channels) {
debug(" Channel %s (%s) IMPORT", c->name, net_label[c->net_type]);
if (c->in_filter == FILTER_ACCEPT)
debug(" ALL\n");
else if (c->in_filter == FILTER_REJECT)
debug(" NONE\n");
else if (c->in_filter == FILTER_UNDEF)
debug(" UNDEF\n");
else if (c->in_filter->sym) {
ASSERT(c->in_filter->sym->filter == c->in_filter);
debug(" named filter %s\n", c->in_filter->sym->name);
} else {
debug("\n");
f_dump_line(c->in_filter->root, 2);
}
}
}
}
}
}