/* * Filters: utility functions * * Copyright 1998 Pavel Machek * * 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] #define prevline fstk->estk[fstk->ecnt-2] #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); } } } } } }