[PATCH nft v2 1/2] evaluate: rename recursion counter to recursion.binop

[Florian Westphal <fw@xxxxxxxxx>]

The existing recursion counter is used by the binop expression to detect
if we've completely followed all the binops.

We can only chain up to NFT_MAX_EXPR_RECURSION binops, but the evaluation
step can perform constant-folding, so we must recurse until we found the
rightmost (last) binop in the chain.

Then we can check the post-eval chain to see if it is something that can
be serialized later (i.e., if we are within the NFT_MAX_EXPR_RECURSION
after constant folding) or not.

Thus we can't reuse the existing ctx->recursion counter for other
expressions; entering the initial expr_evaluate_binop with
ctx->recursion > 0 would break things.

Therefore rename this to an embedded structure.
This allows us to add a new recursion counter in a followup patch.

Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
 v2: I'm resending this as per last discussion.
 There are no changes in this patch.

 include/rule.h |  8 ++++++--
 src/evaluate.c | 10 +++++-----
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/rule.h b/include/rule.h
index 85a0d9c0b524..e7e80a41506c 100644
--- a/include/rule.h
+++ b/include/rule.h
@@ -756,6 +756,10 @@ extern void cmd_free(struct cmd *cmd);
 #include <payload.h>
 #include <expression.h>
 
+struct eval_recursion {
+	uint16_t binop;
+};
+
 /**
  * struct eval_ctx - evaluation context
  *
@@ -767,7 +771,7 @@ extern void cmd_free(struct cmd *cmd);
  * @set:	current set
  * @stmt:	current statement
  * @stmt_len:	current statement template length
- * @recursion:  expr evaluation recursion counter
+ * @recursion:  expr evaluation recursion counters
  * @cache:	cache context
  * @debug_mask: debugging bitmask
  * @ectx:	expression context
@@ -783,7 +787,7 @@ struct eval_ctx {
 	struct set		*set;
 	struct stmt		*stmt;
 	uint32_t		stmt_len;
-	uint32_t		recursion;
+	struct eval_recursion	recursion;
 	struct expr_ctx		ectx;
 	struct proto_ctx	_pctx[2];
 	const struct proto_desc	*inner_desc;
diff --git a/src/evaluate.c b/src/evaluate.c
index e8e4aa2df4ca..2878a23c24ee 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1522,11 +1522,11 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 	unsigned int max_shift_len = ctx->ectx.len;
 	int ret = -1;
 
-	if (ctx->recursion >= USHRT_MAX)
+	if (ctx->recursion.binop >= USHRT_MAX)
 		return expr_binary_error(ctx->msgs, op, NULL,
 					 "Binary operation limit %u reached ",
-					 ctx->recursion);
-	ctx->recursion++;
+					 ctx->recursion.binop);
+	ctx->recursion.binop++;
 
 	if (expr_evaluate(ctx, &op->left) < 0)
 		return -1;
@@ -1611,7 +1611,7 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 	}
 
 
-	if (ctx->recursion == 0)
+	if (ctx->recursion.binop == 0)
 		BUG("recursion counter underflow");
 
 	/* can't check earlier: evaluate functions might do constant-merging + expr_free.
@@ -1619,7 +1619,7 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 	 * So once we've evaluate everything check for remaining length of the
 	 * binop chain.
 	 */
-	if (--ctx->recursion == 0) {
+	if (--ctx->recursion.binop == 0) {
 		unsigned int to_linearize = 0;
 
 		op = *expr;
-- 
2.49.0