evaluate: propagate binop_transfer() adjustment to set key size

The right shift transfer may be result in adjusting the set key size,
eg. ip6 dscp results in fetching 6 bits that are splitted between two
bytes, hence the set element ends up being 16 bytes long.

Reported-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

Author: ummakynes

src/evaluate.c

@@ -1282,8 +1282,9 @@ static int expr_evaluate_map(struct eval_ctx *ctx, struct expr **expr)
 		if (binop_transfer(ctx, expr) < 0)
 			return -1;
 
-		map = *expr;
+		ctx->set->key->len = ctx->ectx.len;
 		ctx->set = NULL;
+		map = *expr;
 		map->mappings->set->flags |= map->mappings->set->init->set_flags;
 		break;
 	case EXPR_SYMBOL: