Add new variable expression that we can use to attach symbols in
runtime, this allows us to redefine variables via new keyword, eg.
table ip x {
chain y {
define address = { 1.1.1.1, 2.2.2.2 }
ip saddr $address
redefine address = { 3.3.3.3 }
ip saddr $address
}
}
# nft list ruleset
table ip x {
chain y {
ip saddr { 1.1.1.1, 2.2.2.2 }
ip saddr { 3.3.3.3 }
}
}
Note that redefinition just places a new symbol version before the
existing one, so symbol lookups always find the latest version. The
undefine keyword decrements the reference counter and removes the symbol
from the list, so it cannot be used anymore. Still, previous references
to this symbol via variable expression are still valid.
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: undefine should not remove symbols for parent scope, only for
current one.
include/expression.h | 10 +++++++++-
include/rule.h | 5 ++++-
src/evaluate.c | 21 ++++++++++++---------
src/expression.c | 39 +++++++++++++++++++++++++++++++++++++++
src/parser_bison.y | 9 ++++-----
src/rule.c | 39 +++++++++++++++++++++++++++++++++------
6 files changed, 101 insertions(+), 22 deletions(-)
diff --git a/include/expression.h b/include/expression.h
index 26182120f63d..7b9b62297150 100644
--- a/include/expression.h
+++ b/include/expression.h
@@ -16,6 +16,7 @@
* @EXPR_INVALID: uninitialized type, should not happen
* @EXPR_VERDICT: nftables verdict expression
* @EXPR_SYMBOL: unparsed symbol
+ * @EXPR_VARIABLE: variable
* @EXPR_VALUE: literal numeric or string expression
* @EXPR_PREFIX: prefixed expression
* @EXPR_RANGE: literal range
@@ -41,6 +42,7 @@ enum expr_types {
EXPR_INVALID,
EXPR_VERDICT,
EXPR_SYMBOL,
+ EXPR_VARIABLE,
EXPR_VALUE,
EXPR_PREFIX,
EXPR_RANGE,
@@ -97,7 +99,6 @@ extern const char *expr_op_symbols[];
enum symbol_types {
SYMBOL_VALUE,
- SYMBOL_DEFINE,
SYMBOL_SET,
};
@@ -226,6 +227,10 @@ struct expr {
enum symbol_types symtype;
};
struct {
+ /* EXPR_VARIABLE */
+ struct symbol *sym;
+ };
+ struct {
/* EXPR_VERDICT */
int verdict;
const char *chain;
@@ -387,6 +392,9 @@ static inline void symbol_expr_set_type(struct expr *expr,
expr->dtype = dtype;
}
+struct expr *variable_expr_alloc(const struct location *loc,
+ struct scope *scope, struct symbol *sym);
+
extern struct expr *constant_expr_alloc(const struct location *loc,
const struct datatype *dtype,
enum byteorder byteorder,
diff --git a/include/rule.h b/include/rule.h
index 531222ce1efc..58c4aeef700e 100644
--- a/include/rule.h
+++ b/include/rule.h
@@ -73,18 +73,21 @@ extern void scope_release(const struct scope *scope);
* @list: scope symbol list node
* @identifier: identifier
* @expr: initializer
+ * @refcnt: reference counter
*/
struct symbol {
struct list_head list;
const char *identifier;
struct expr *expr;
+ int refcnt;
};
extern void symbol_bind(struct scope *scope, const char *identifier,
struct expr *expr);
-extern int symbol_unbind(struct scope *scope, const char *identifier);
+extern int symbol_unbind(const struct scope *scope, const char *identifier);
extern struct symbol *symbol_lookup(const struct scope *scope,
const char *identifier);
+struct symbol *symbol_get(const struct scope *scope, const char *identifier);
enum table_flags {
TABLE_F_DORMANT = (1 << 0),
diff --git a/src/evaluate.c b/src/evaluate.c
index 40a9292fe53a..cc8eac83f1d9 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -168,7 +168,6 @@ static struct table *table_lookup_global(struct eval_ctx *ctx)
static int expr_evaluate_symbol(struct eval_ctx *ctx, struct expr **expr)
{
struct error_record *erec;
- struct symbol *sym;
struct table *table;
struct set *set;
struct expr *new;
@@ -183,14 +182,6 @@ static int expr_evaluate_symbol(struct eval_ctx *ctx, struct expr **expr)
return -1;
}
break;
- case SYMBOL_DEFINE:
- sym = symbol_lookup((*expr)->scope, (*expr)->identifier);
- if (sym == NULL)
- return expr_error(ctx->msgs, *expr,
- "undefined identifier '%s'",
- (*expr)->identifier);
- new = expr_clone(sym->expr);
- break;
case SYMBOL_SET:
ret = cache_update(ctx->nf_sock, ctx->cache, ctx->cmd->op,
ctx->msgs, ctx->debug_mask & NFT_DEBUG_NETLINK, ctx->octx);
@@ -1776,6 +1767,16 @@ static int expr_evaluate_meta(struct eval_ctx *ctx, struct expr **exprp)
return expr_evaluate_primary(ctx, exprp);
}
+static int expr_evaluate_variable(struct eval_ctx *ctx, struct expr **exprp)
+{
+ struct expr *new = expr_clone((*exprp)->sym->expr);
+
+ expr_free(*exprp);
+ *exprp = new;
+
+ return expr_evaluate(ctx, exprp);
+}
+
static int expr_evaluate(struct eval_ctx *ctx, struct expr **expr)
{
if (ctx->debug_mask & NFT_DEBUG_EVALUATION) {
@@ -1791,6 +1792,8 @@ static int expr_evaluate(struct eval_ctx *ctx, struct expr **expr)
switch ((*expr)->ops->type) {
case EXPR_SYMBOL:
return expr_evaluate_symbol(ctx, expr);
+ case EXPR_VARIABLE:
+ return expr_evaluate_variable(ctx, expr);
case EXPR_SET_REF:
return 0;
case EXPR_VALUE:
diff --git a/src/expression.c b/src/expression.c
index 393c1b2b2cfe..ee75284e79b4 100644
--- a/src/expression.c
+++ b/src/expression.c
@@ -254,6 +254,45 @@ struct expr *symbol_expr_alloc(const struct location *loc,
return expr;
}
+static void variable_expr_print(const struct expr *expr,
+ struct output_ctx *octx)
+{
+ nft_print(octx, "$%s", expr->sym->identifier);
+}
+
+static void variable_expr_clone(struct expr *new, const struct expr *expr)
+{
+ new->scope = expr->scope;
+ new->sym = expr->sym;
+
+ expr->sym->refcnt++;
+}
+
+static void variable_expr_destroy(struct expr *expr)
+{
+ expr->sym->refcnt--;
+}
+
+static const struct expr_ops variable_expr_ops = {
+ .type = EXPR_VARIABLE,
+ .name = "variable",
+ .print = variable_expr_print,
+ .clone = variable_expr_clone,
+ .destroy = variable_expr_destroy,
+};
+
+struct expr *variable_expr_alloc(const struct location *loc,
+ struct scope *scope, struct symbol *sym)
+{
+ struct expr *expr;
+
+ expr = expr_alloc(loc, &variable_expr_ops, &invalid_type,
+ BYTEORDER_INVALID, 0);
+ expr->scope = scope;
+ expr->sym = sym;
+ return expr;
+}
+
static void constant_expr_print(const struct expr *expr,
struct output_ctx *octx)
{
diff --git a/src/parser_bison.y b/src/parser_bison.y
index 58bc680503d7..ee6729f11abd 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -771,8 +771,6 @@ common_block : INCLUDE QUOTED_STRING stmt_separator
{
struct scope *scope = current_scope(state);
- /* ignore missing identifier */
- symbol_unbind(scope, $2);
symbol_bind(scope, $2, $4);
xfree($2);
}
@@ -2584,16 +2582,17 @@ match_stmt : relational_expr
variable_expr : '$' identifier
{
struct scope *scope = current_scope(state);
+ struct symbol *sym;
- if (symbol_lookup(scope, $2) == NULL) {
+ sym = symbol_get(scope, $2);
+ if (!sym) {
erec_queue(error(&@2, "unknown identifier '%s'", $2),
state->msgs);
xfree($2);
YYERROR;
}
- $$ = symbol_expr_alloc(&@$, SYMBOL_DEFINE,
- scope, $2);
+ $$ = variable_expr_alloc(&@$, scope, sym);
xfree($2);
}
;
diff --git a/src/rule.c b/src/rule.c
index c0b42b1c186b..b331416ac066 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -467,6 +467,7 @@ void scope_release(const struct scope *scope)
struct symbol *sym, *next;
list_for_each_entry_safe(sym, next, &scope->symbols, list) {
+ assert(sym->refcnt == 1);
list_del(&sym->list);
xfree(sym->identifier);
expr_free(sym->expr);
@@ -481,22 +482,48 @@ void symbol_bind(struct scope *scope, const char *identifier, struct expr *expr)
sym = xzalloc(sizeof(*sym));
sym->identifier = xstrdup(identifier);
sym->expr = expr;
+ sym->refcnt = 1;
- list_add_tail(&sym->list, &scope->symbols);
+ list_add(&sym->list, &scope->symbols);
}
-int symbol_unbind(struct scope *scope, const char *identifier)
+struct symbol *symbol_get(const struct scope *scope, const char *identifier)
{
struct symbol *sym;
sym = symbol_lookup(scope, identifier);
if (!sym)
- return -1;
+ return NULL;
+
+ sym->refcnt++;
+ return sym;
+}
+
+static void symbol_put(struct symbol *sym)
+{
+ if (--sym->refcnt == 0) {
+ xfree(sym->identifier);
+ expr_free(sym->expr);
+ xfree(sym);
+ }
+}
+
+static void symbol_remove(struct symbol *sym)
+{
list_del(&sym->list);
- xfree(sym->identifier);
- expr_free(sym->expr);
- xfree(sym);
+ symbol_put(sym);
+}
+
+int symbol_unbind(const struct scope *scope, const char *identifier)
+{
+ struct symbol *sym, *next;
+
+ list_for_each_entry_safe(sym, next, &scope->symbols, list) {
+ if (!strcmp(sym->identifier, identifier))
+ symbol_remove(sym);
+ }
+
return 0;
}
--
2.11.0
--
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