[nft PATCH v4 13/32] evaluate: support shifts larger than the width of the left operand

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If we want to left-shift a value of narrower type and assign the result
to a variable of a wider type, we are constrained to only shifting up to
the width of the narrower type.  Thus:

  add rule t c meta mark set ip dscp << 2

works, but:

  add rule t c meta mark set ip dscp << 8

does not, even though the lvalue is large enough to accommodate the
result.

Evaluation of the left-hand operand of a shift overwrites the `len`
field of the evaluation context when `expr_evaluate_primary` is called.
Instead, preserve the `len` value of the evaluation context for shifts,
and support shifts up to that size, even if they are larger than the
length of the left operand.

Update netlink_delinearize.c to handle the case where the length of a
shift expression does not match that of its left-hand operand.

Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx>
---
 src/evaluate.c            | 23 ++++++++++++++---------
 src/netlink_delinearize.c |  4 ++--
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/evaluate.c b/src/evaluate.c
index be493f85010c..ee4da5a2b889 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1116,14 +1116,18 @@ static int constant_binop_simplify(struct eval_ctx *ctx, struct expr **expr)
 static int expr_evaluate_shift(struct eval_ctx *ctx, struct expr **expr)
 {
 	struct expr *op = *expr, *left = op->left, *right = op->right;
+	unsigned int shift = mpz_get_uint32(right->value);
+	unsigned int op_len = left->len;
 
-	if (mpz_get_uint32(right->value) >= left->len)
-		return expr_binary_error(ctx->msgs, right, left,
-					 "%s shift of %u bits is undefined "
-					 "for type of %u bits width",
-					 op->op == OP_LSHIFT ? "Left" : "Right",
-					 mpz_get_uint32(right->value),
-					 left->len);
+	if (shift >= op_len) {
+		if (shift >= ctx->ectx.len)
+			return expr_binary_error(ctx->msgs, right, left,
+						 "%s shift of %u bits is undefined for type of %u bits width",
+						 op->op == OP_LSHIFT ? "Left" : "Right",
+						 shift,
+						 op_len);
+		op_len = ctx->ectx.len;
+	}
 
 	/* Both sides need to be in host byte order */
 	if (byteorder_conversion(ctx, &op->left, BYTEORDER_HOST_ENDIAN) < 0)
@@ -1134,7 +1138,7 @@ static int expr_evaluate_shift(struct eval_ctx *ctx, struct expr **expr)
 
 	op->dtype     = &integer_type;
 	op->byteorder = BYTEORDER_HOST_ENDIAN;
-	op->len       = left->len;
+	op->len	      = op_len;
 
 	if (expr_is_constant(left))
 		return constant_binop_simplify(ctx, expr);
@@ -1167,6 +1171,7 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 {
 	struct expr *op = *expr, *left, *right;
 	const char *sym = expr_op_symbols[op->op];
+	unsigned int ectx_len = ctx->ectx.len;
 
 	if (expr_evaluate(ctx, &op->left) < 0)
 		return -1;
@@ -1174,7 +1179,7 @@ static int expr_evaluate_binop(struct eval_ctx *ctx, struct expr **expr)
 
 	if (op->op == OP_LSHIFT || op->op == OP_RSHIFT)
 		__expr_set_context(&ctx->ectx, &integer_type,
-				   left->byteorder, ctx->ectx.len, 0);
+				   left->byteorder, ectx_len, 0);
 	if (expr_evaluate(ctx, &op->right) < 0)
 		return -1;
 	right = op->right;
diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index cf5359bf269e..9f6fdee3e92d 100644
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -486,7 +486,7 @@ static struct expr *netlink_parse_bitwise_bool(struct netlink_parse_ctx *ctx,
 		mpz_ior(m, m, o);
 	}
 
-	if (left->len > 0 && mpz_scan0(m, 0) == left->len) {
+	if (left->len > 0 && mpz_scan0(m, 0) >= left->len) {
 		/* mask encompasses the entire value */
 		expr_free(mask);
 	} else {
@@ -536,7 +536,7 @@ static struct expr *netlink_parse_bitwise_shift(struct netlink_parse_ctx *ctx,
 	right->byteorder = BYTEORDER_HOST_ENDIAN;
 
 	expr = binop_expr_alloc(loc, op, left, right);
-	expr->len = left->len;
+	expr->len = nftnl_expr_get_u32(nle, NFTNL_EXPR_BITWISE_LEN) * BITS_PER_BYTE;
 
 	return expr;
 }
-- 
2.35.1




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