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===================================================
Open vSwitch Configuration Database Specification
===================================================
Basic Notation
--------------
OVSDB uses JSON, as defined by RFC 4627, for its schema format and its
wire protocol format. The JSON implementation in Open vSwitch has the
following limitations:
- Null bytes (\u0000) are not allowed in strings.
- Only UTF-8 encoding is supported. (RFC 4627 also mentions
UTF-16BE, UTF-16LE, and UTF-32.)
- RFC 4627 says that names within a JSON object should be unique.
The Open vSwitch JSON parser discards all but the last value
for a name that is specified more than once.
The descriptions below use the following shorthand notations for JSON
values. Additional notation is presented later.
<string>
A JSON string. Any Unicode string is allowed, as specified by RFC
4627. Implementations may disallow null bytes.
<id>
A JSON string matching [a-zA-Z_][a-zA-Z0-9_]*.
<id>s that begin with _ are reserved to the implementation and may
not be used by the user.
<version>
A JSON string that contains a version number that matches
[0-9]+\.[0-9]+\.[0-9]+
<boolean>
A JSON true or false value.
<number>
A JSON number.
<integer>
A JSON number with an integer value, within a certain range
(currently -2**63...+2**63-1).
<json-value>
Any JSON value.
<nonnull-json-value>
Any JSON value except null.
<error>
A JSON object with the following members:
"error": <string> required
"details": <string> optional
The value of the "error" member is a short string, specified in
this document, that broadly indicates the class of the error.
Most "error" strings are specific to contexts described elsewhere
in this document, but the following "error" strings may appear in
any context where an <error> is permitted:
"error": "resources exhausted"
The operation requires more resources (memory, disk, CPU,
etc.) than are currently available to the database server.
"error": "I/O error"
Problems accessing the disk, network, or other required
resources prevented the operation from completing.
Database implementations may use "error" strings not specified
in this document to indicate errors that do not fit into any of
the specified categories.
Optionally, an <error> may include a "details" member, whose value
is a string that describes the error in more detail for the
benefit of a human user or administrator. This document does not
specify the format or content of the "details" string.
An <error> may also have other members that describe the error in
more detail. This document does not specify the names or values
of these members.
Schema Format
-------------
An Open vSwitch configuration database consists of a set of tables,
each of which has a number of columns and zero or more rows. A schema
is represented by <database-schema>, as described below.
<database-schema>
A JSON object with the following members:
"name": <id> required
"version": <version> required
"tables": {<id>: <table-schema>, ...} required
The "name" identifies the database as a whole. It must be
provided to most JSON-RPC requests to identify the database being
operated on. The value of "tables" is a JSON object whose names
are table names and whose values are <table-schema>s.
The "version" reports the version of the database schema. Because
this is a recent addition to the schema format, OVSDB permits it
to be omitted, but future versions of OVSDB will require it to be
present. Open vSwitch semantics for "version" are described in
ovs-vswitchd.conf.db(5).
<table-schema>
A JSON object with the following members:
"columns": {<id>: <column-schema>, ...} required
"maxRows": <integer> optional
The value of "columns" is a JSON object whose names are column
names and whose values are <column-schema>s.
Every table has the following columns whose definitions are not
included in the schema:
"_uuid": This column, which contains exactly one UUID value,
is initialized to a random value by the database engine when
it creates a row. It is read-only, and its value never
changes during the lifetime of a row.
"_version": Like "_uuid", this column contains exactly one
UUID value, initialized to a random value by the database
engine when it creates a row, and it is read-only. However,
its value changes to a new random value whenever any other
field in the row changes. Furthermore, its value is
ephemeral: when the database is closed and reopened, or when
the database process is stopped and then started again, each
"_version" also changes to a new random value.
If "maxRows" is specified, as a positive integer, it limits the
maximum number of rows that may be present in the table. This is
a "deferred" constraint, enforced only at transaction commit time
(see the "transact" request below). If "maxRows" is not
specified, the size of the table is limited only by the resources
available to the database server.
<column-schema>
A JSON object with the following members:
"type": <type> required
"ephemeral": <boolean> optional
"mutable": <boolean> optional
The "type" specifies the type of data stored in this column. If
"ephemeral" is specified as true, then this column's values are
not guaranteed to be durable; they may be lost when the database
restarts. If "mutable" is specified as false, then this column's
values may not be modified after they are initially set with the
"insert" operation.
<type>
The type of a database column. Either an <atomic-type> or a JSON
object that describes the type of a database column, with the
following members:
"key": <base-type> required
"value": <base-type> optional
"min": <integer> optional
"max": <integer> or "unlimited" optional
If "min" or "max" is not specified, each defaults to 1. If "max"
is specified as "unlimited", then there is no specified maximum
number of elements, although the implementation will enforce some
limit. After considering defaults, "min" must be exactly 0 or
exactly 1, "max" must be at least 1, and "max" must be greater
than or equal to "min".
If "min" and "max" are both 1 and "value" is not specified, the
type is the scalar type specified by "key".
If "min" is not 1 or "max" is not 1, or both, and "value" is not
specified, the type is a set of scalar type "key".
If "value" is specified, the type is a map from type "key" to type
"value".
<base-type>
The type of a key or value in a database column. Either an
<atomic-type> or a JSON object with the following members:
"type": <atomic-type> required
"enum": <value> optional
"minInteger": <integer> optional, integers only
"maxInteger": <integer> optional, integers only
"minReal": <real> optional, reals only
"maxReal": <real> optional, reals only
"minLength": <integer> optional, strings only
"maxLength": <integer> optional, strings only
"refTable": <id> optional, uuids only
"refType": "strong" or "weak" optional, only with "refTable"
An <atomic-type> by itself is equivalent to a JSON object with a
single member "type" whose value is the <atomic-type>.
"enum" may be specified as a <value> whose type is a set of one
or more values specified for the member "type". If "enum" is
specified, then the valid values of the <base-type> are limited to
those in the <value>.
"enum" is mutually exclusive with the following constraints.
If "type" is "integer", then "minInteger" or "maxInteger" or both
may also be specified, restricting the valid integer range. If
both are specified, then the maxInteger must be greater than or
equal to minInteger.
If "type" is "real", then "minReal" or "maxReal" or both may also
be specified, restricting the valid real range. If both are
specified, then the maxReal must be greater than or equal to
minReal.
If "type" is "string", then "minLength" and "maxLength" or both
may be specified, restricting the valid length of value strings.
If both are specified, then maxLength must be greater than or
equal to minLength. String length is measured in characters (not
bytes or UTF-16 code units).
If "type" is "uuid", then "refTable", if present, must be the name
of a table within this database. If "refTable" is specified, then
"refType" may also be specified. If "refTable" is set, the effect
depends on "refType":
- If "refType" is "strong" or if "refType" is omitted, the
allowed UUIDs are limited to UUIDs for rows in the named
table.
- If "refType" is "weak", then any UUIDs are allowed, but
UUIDs that do not correspond to rows in the named table will
be automatically deleted.
"refTable" constraints are "deferred" constraints: they are
enforced only at transaction commit time (see the "transact"
request below). The other contraints on <base-type> are
"immediate", enforced immediately by each operation.
<atomic-type>
One of the strings "integer", "real", "boolean", "string", or
"uuid", representing the specified scalar type.
Wire Protocol
-------------
The database wire protocol is implemented in JSON-RPC 1.0. We
encourage use of JSON-RPC over stream connections instead of JSON-RPC
over HTTP, for these reasons:
* JSON-RPC is a peer-to-peer protocol, but HTTP is a client-server
protocol, which is a poor match. Thus, JSON-RPC over HTTP
requires the client to periodically poll the server to receive
server requests.
* HTTP is more complicated than stream connections and doesn't
provide any corresponding advantage.
* The JSON-RPC specification for HTTP transport is incomplete.
We are using TCP port 6632 for the database JSON-RPC connection.
The database wire protocol consists of the following JSON-RPC methods:
list_dbs
........
Request object members:
"method": "list_dbs" required
"params": [] required
"id": <nonnull-json-value> required
Response object members:
"result": [<db-name>, ...]
"error": null
"id": same "id" as request
This operation retrieves an array whose elements are <db-name>s
that name the databases that can be accessed over this JSON-RPC
connection.
get_schema
..........
Request object members:
"method": "get_schema" required
"params": [<db-name>] required
"id": <nonnull-json-value> required
Response object members:
"result": <database-schema>
"error": null
"id": same "id" as request
This operation retrieves a <database-schema> that describes hosted
database <db-name>.
transact
........
Request object members:
"method": "transact" required
"params": [<db-name>, <operation>*] required
"id": <nonnull-json-value> required
Response object members:
"result": [<object>*]
"error": null
"id": same "id" as request
The "params" array for this method consists of a <db-name> that
identifies the database to which the transaction applies, followed by
zero or more JSON objects, each of which represents a single database
operation. The "Operations" section below describes the valid
operations.
The value of "id" must be unique among all in-flight transactions
within the current JSON-RPC session. Otherwise, the server may return
a JSON-RPC error.
The database server executes each of the specified operations in the
specified order, except that if an operation fails, then the remaining
operations are not executed.
The set of operations is executed as a single atomic, consistent,
isolated transaction. The transaction is committed only if every
operation succeeds. Durability of the commit is not guaranteed unless
the "commit" operation, with "durable" set to true, is included in the
operation set (see below).
Regardless of whether errors occur, the response is always a JSON-RPC
response with null "error" and a "result" member that is an array with
the same number of elements as "params". Each element of the "result"
array corresponds to the same element of the "params" array. The
"result" array elements may be interpreted as follows:
- A JSON object that does not contain an "error" member indicates
that the operation completed successfully. The specific members
of the object are specified below in the descriptions of
individual operations. Some operations do not produce any
results, in which case the object will have no members.
- An <error>, which indicates that the operation completed with an
error.
- A JSON null value indicates that the operation was not attempted
because a prior operation failed.
In general, "result" contains some number of successful results,
possibly followed by an error, in turn followed by enough JSON null
values to match the number of elements in "params". There is one
exception: if all of the operations succeed, but the results cannot be
committed, then "result" will have one more element than "params",
with the additional element an <error>. The possible "error" strings
include at least the following:
"error": "referential integrity violation"
When the commit was attempted, a column's value referenced the
UUID for a row that did not exist in the table named by the
column's <base-type> key or value "refTable" that has a
"refType" of "strong". (This can be caused by inserting a row
that references a nonexistent row, by deleting a row that is
still referenced by another row, by specifying the UUID for a
row in the wrong table, and other ways.)
"error": "constraint violation"
A column with a <base-type> key or value "refTable" whose
"refType" is "weak" became empty due to deletion(s) caused
because the rows that it referenced were deleted (or never
existed, if the column's row was inserted within the
transaction), and this column is not allowed to be empty
because its <type> has a "min" of 1.
"error": "constraint violation"
The number of rows in a table exceeds the maximum number
permitted by the table's "maxRows" value (see <table-schema>).
If "params" contains one or more "wait" operations, then the
transaction may take an arbitrary amount of time to complete. The
database implementation must be capable of accepting, executing, and
replying to other transactions and other JSON-RPC requests while a
transaction or transactions containing "wait" operations are
outstanding on the same or different JSON-RPC sessions.
The section "Notation for the Wire Protocol" below describes
additional notation for use with the wire protocol. After that, the
"Operations" section describes each operation.
cancel
......
Request object members:
"method": "cancel" required
"params": [the "id" for an outstanding request] required
"id": null required
Response object members:
<no response>
This JSON-RPC notification instructs the database server to
immediately complete or cancel the "transact" request whose "id" is
the same as the notification's "params" value.
If the "transact" request can be completed immediately, then the
server sends a response in the form described for "transact", above.
Otherwise, the server sends a JSON-RPC error response of the following
form:
"result": null
"error": "canceled"
"id": the request "id" member
The "cancel" notification itself has no reply.
monitor
.......
Request object members:
"method": "monitor" required
"params": [<db-name>, <json-value>, <monitor-requests>] required
"id": <nonnull-json-value> required
<monitor-requests> is an object that maps from a table name to an
array of <monitor-request> objects. For backward compatibility, a
single <monitor-request> may be used instead of an array; it is
treated as a single-element array.
Each <monitor-request> is an object with the following members:
"columns": [<column>*] optional
"select": <monitor-select> optional
<monitor-select> is an object with the following members:
"initial": <boolean> optional
"insert": <boolean> optional
"delete": <boolean> optional
"modify": <boolean> optional
Response object members:
"result": <table-updates>
"error": null
"id": same "id" as request
This JSON-RPC request enables a client to replicate tables or subsets
of tables within database <db-name>. Each element of
<monitor-requests> specifies a table to be replicated. The JSON-RPC
response to the "monitor" includes the initial contents of each table,
unless disabled (see below). Afterward, when changes to those tables
are committed, the changes are automatically sent to the client using
the "update" monitor notification. This monitoring persists until the
JSON-RPC session terminates or until the client sends a
"monitor_cancel" JSON-RPC request.
Each <monitor-request> describes how to monitor columns in a table:
The circumstances in which an "update" notification is sent for a
row within the table are determined by <monitor-select>:
If "initial" is omitted or true, every row in the table is
sent as part of the reply to the "monitor" request.
If "insert" is omitted or true, "update" notifications are
sent for rows newly inserted into the table.
If "delete" is omitted or true, "update" notifications are
sent for rows deleted from the table.
If "modify" is omitted or true, "update" notifications are
sent whenever when a row in the table is modified.
The "columns" member specifies the columns whose values are
monitored. It must not contain duplicates. If "columns" is
omitted, all columns in the table, except for "_uuid", are
monitored.
If there is more than one <monitor-request> in an array of them, then
each <monitor-request> in the array should specify both "columns" and
"select", and the "columns" must be non-overlapping sets.
The "result" in the JSON-RPC response to the "monitor" request is a
<table-updates> object (see below) that contains the contents of the
tables for which "initial" rows are selected. If no tables' initial
contents are requested, then "result" is an empty object.
update
......
Notification object members:
"method": "update"
"params": [<json-value>, <table-updates>]
"id": null
The <json-value> in "params" is the same as the value passed as the
<json-value> in "params" for the "monitor" request.
<table-updates> is an object that maps from a table name to a
<table-update>.
A <table-update> is an object that maps from the row's UUID (as a
36-byte string) to a <row-update> object.
A <row-update> is an object with the following members:
"old": <row> present for "delete" and "modify" updates
"new": <row> present for "initial", "insert", and "modify" updates
This JSON-RPC notification is sent from the server to the client to
tell it about changes to a monitored table (or the initial state of a
modified table). Each table in which one or more rows has changed (or
whose initial view is being presented) is represented in "updates".
Each row that has changed (or whose initial view is being presented)
is represented in its <table-update> as a member with its name taken
from the row's _uuid member. The corresponding value is a
<row-update>:
The "old" member is present for "delete" and "modify" updates.
For "delete" updates, each monitored column is included. For
"modify" updates, the prior value of each monitored column whose
value has changed is included (monitored columns that have not
changed are represented in "new").
The "new" member is present for "initial", "insert", and "modify"
updates. For "initial" and "insert" updates, each monitored
column is included. For "modify" updates, the new value of each
monitored column is included.
monitor_cancel
..............
Request object members:
"method": "monitor_cancel" required
"params": [<json-value>] required
"id": <nonnull-json-value> required
Response object members:
"result": {}
"error": null
"id": the request "id" member
Cancels the ongoing table monitor request, identified by the
<json-value> in "params" matching the <json-value> in "params" for an
ongoing "monitor" request. No more "update" messages will be sent for
this table monitor.
echo
....
Request object members:
"method": "echo" required
"params": JSON array with any contents required
"id": <json-value> required
Response object members:
"result": same as "params"
"error": null
"id": the request "id" member
Both the JSON-RPC client and the server must implement this request.
This JSON-RPC request and response can be used to implement connection
keepalives, by allowing the server to check that the client is still
there or vice versa.
Notation for the Wire Protocol
------------------------------
<db-name>
An <id> that names a database. The valid <db-name>s can be
obtained using a "list-db" request. The <db-name> is taken from
the "name" member of <database-schema>.
<table>
An <id> that names a table.
<column>
An <id> that names a table column.
<row>
A JSON object that describes a table row or a subset of a table
row. Each member is the name of a table column paired with the
<value> of that column.
<value>
A JSON value that represents the value of a column in a table row,
one of <atom>, a <set>, or a <map>.
<atom>
A JSON value that represents a scalar value for a column, one of
<string>, <number>, <boolean>, <uuid>, <named-uuid>.
<set>
Either an <atom>, representing a set with exactly one element, or
a 2-element JSON array that represents a database set value. The
first element of the array must be the string "set" and the second
element must be an array of zero or more <atom>s giving the values
in the set. All of the <atom>s must have the same type.
<map>
A 2-element JSON array that represents a database map value. The
first element of the array must be the string "map" and the second
element must be an array of zero or more <pair>s giving the values
in the map. All of the <pair>s must have the same key and value
types.
(JSON objects are not used to represent <map> because JSON only
allows string names in an object.)
<pair>
A 2-element JSON array that represents a pair within a database
map. The first element is an <atom> that represents the key, the
second element is an <atom> that represents the value.
<uuid>
A 2-element JSON array that represents a UUID. The first element
of the array must be the string "uuid" and the second element must
be a 36-character string giving the UUID in the format described
by RFC 4122. For example, the following <uuid> represents the
UUID 550e8400-e29b-41d4-a716-446655440000:
["uuid", "550e8400-e29b-41d4-a716-446655440000"]
<named-uuid>
A 2-element JSON array that represents the UUID of a row inserted
in an "insert" operation within the same transaction. The first
element of the array must be the string "named-uuid" and the
second element should be the string specified as the "uuid-name"
for an "insert" operation within the same transaction. For
example, if an "insert" operation within this transaction
specifies a "uuid-name" of "myrow", the following <named-uuid>
represents the UUID created by that operation:
["named-uuid", "myrow"]
A <named-uuid> may be used anywhere a <uuid> is valid.
<condition>
A 3-element JSON array of the form [<column>, <function>,
<value>] that represents a test on a column value.
Except as otherwise specified below, <value> must have the same
type as <column>.
The meaning depends on the type of <column>:
integer
real
<function> must be "<", "<=", "==", "!=", ">=", ">",
"includes", or "excludes".
The test is true if the column's value satisfies the
relation <function> <value>, e.g. if the column has value
1 and <value> is 2, the test is true if <function> is "<",
"<=" or "!=", but not otherwise.
"includes" is equivalent to "=="; "excludes" is equivalent
to "!=".
boolean
string
uuid
<function> must be "!=", "==", "includes", or "excludes".
If <function> is "==" or "includes", the test is true if
the column's value equals <value>. If <function> is "!="
or "excludes", the test is inverted.
set
map
<function> must be "!=", "==", "includes", or "excludes".
If <function> is "==", the test is true if the column's
value contains exactly the same values (for sets) or pairs
(for maps). If <function> is "!=", the test is inverted.
If <function> is "includes", the test is true if the
column's value contains all of the values (for sets) or
pairs (for maps) in <value>. The column's value may also
contain other values or pairs.
If <function> is "excludes", the test is true if the
column's value does not contain any of the values (for
sets) or pairs (for maps) in <value>. The column's value
may contain other values or pairs not in <value>.
If <function> is "includes" or "excludes", then the
required type of <value> is slightly relaxed, in that it
may have fewer than the minimum number of elements
specified by the column's type. If <function> is
"excludes", then the required type is additionally relaxed
in that <value> may have more than the maximum number of
elements specified by the column's type.
<function>
One of "<", "<=", "==", "!=", ">=", ">", "includes", "excludes".
<mutation>
A 3-element JSON array of the form [<column>, <mutator>, <value>]
that represents a change to a column value.
Except as otherwise specified below, <value> must have the same
type as <column>.
The meaning depends on the type of <column>:
integer
real
<mutator> must be "+=", "-=", "*=", "/=" or (integer only)
"%=". The value of <column> is changed to the sum,
difference, product, quotient, or remainder, respectively,
of <column> and <value>.
Constraints on <column> are ignored when parsing <value>.
boolean
string
uuid
No valid <mutator>s are currently defined for these types.
set
Any <mutator> valid for the set's element type may be
applied to the set, in which case the mutation is applied
to each member of the set individually. <value> must be a
scalar value of the same type as the set's element type,
except that contraints are ignored.
If <mutator> is "insert", then each of the values in the
set in <value> is added to <column> if it is not already
present. The required type of <value> is slightly
relaxed, in that it may have fewer than the minimum number
of elements specified by the column's type.
If <mutator> is "delete", then each of the values in the
set in <value> is removed from <column> if it is present
there. The required type is slightly relaxed in that
<value> may have more or less than the maximum number of
elements specified by the column's type.
map
<mutator> must be "insert" or "delete".
If <mutator> is "insert", then each of the key-value pairs
in the map in <value> is added to <column> only if its key
is not already present. The required type of <value> is
slightly relaxed, in that it may have fewer than the
minimum number of elements specified by the column's type.
If <mutator> is "delete", then <value> may have the same
type as <column> (a map type) or it may be a set whose
element type is the same as <column>'s key type:
- If <value> is a map, the mutation deletes each
key-value pair in <column> whose key and value equal
one of the key-value pairs in <value>.
- If <value> is a set, the mutation deletes each
key-value pair in <column> whose key equals one of
the values in <value>.
For "delete", <value> may have any number of elements,
regardless of restrictions on the number of elements in
<column>.
<mutator>
One of "+=", "-=", "*=", "/=", "%=", "insert", "delete".
Operations
----------
Each of the available operations is described below.
insert
......
Request object members:
"op": "insert" required
"table": <table> required
"row": <row> required
"uuid-name": <id> optional
Result object members:
"uuid": <uuid>
Semantics:
Inserts "row" into "table".
If "row" does not specify values for all the columns in "table",
those columns receive default values. The default value for a
column depends on its type. The default for a column whose <type>
specifies a "min" of 0 is an empty set or empty map. Otherwise,
the default is a single value or a single key-value pair, whose
value(s) depend on its <atomic-type>:
- "integer" or "real": 0
- "boolean": false
- "string": "" (the empty string)
- "uuid": 00000000-0000-0000-0000-000000000000
The new row receives a new, randomly generated UUID.
If "uuid-name" is supplied, then it is an error if <id> is not
unique among the "uuid-name"s supplied on all the "insert"
operations within this transaction.
The UUID for the new row is returned as the "uuid" member of the
result.
Errors:
"error": "duplicate uuid-name"
The same "uuid-name" appears on another "insert" operation
within this transaction.
"error": "constraint violation"
One of the values in "row" does not satisfy the immediate
constraints for its column's <base-type>. This error will
occur for columns that are not explicitly set by "row" if the
default value does not satisfy the column's constraints.
select
......
Request object members:
"op": "select" required
"table": <table> required
"where": [<condition>*] required
"columns": [<column>*] optional
Result object members:
"rows": [<row>*]
Semantics:
Searches "table" for rows that match all the conditions specified
in "where". If "where" is an empty array, every row in "table" is
selected.
The "rows" member of the result is an array of objects. Each
object corresponds to a matching row, with each column
specified in "columns" as a member, the column's name as the
member name and its value as the member value. If "columns"
is not specified, all the table's columns are included. If
two rows of the result have the same values for all included
columns, only one copy of that row is included in "rows".
Specifying "_uuid" within "columns" will avoid dropping
duplicates, since every row has a unique UUID.
The ordering of rows within "rows" is unspecified.
update
......
Request object members:
"op": "update" required
"table": <table> required
"where": [<condition>*] required
"row": <row> required
Result object members:
"count": <integer>
Semantics:
Updates rows in a table.
Searches "table" for rows that match all the conditions
specified in "where". For each matching row, changes the
value of each column specified in "row" to the value for that
column specified in "row".
The "_uuid" and "_version" columns of a table may not be directly
updated with this operation. Columns designated read-only in the
schema also may not be updated.
The "count" member of the result specifies the number of rows
that matched.
Errors:
"error": "constraint violation"
One of the values in "row" does not satisfy the immediate
constraints for its column's <base-type>.
mutate
......
Request object members:
"op": "mutate" required
"table": <table> required
"where": [<condition>*] required
"mutations": [<mutation>*] required
Result object members:
"count": <integer>
Semantics:
Mutates rows in a table.
Searches "table" for rows that match all the conditions specified
in "where". For each matching row, mutates its columns as
specified by each <mutation> in "mutations", in the order
specified.
The "_uuid" and "_version" columns of a table may not be directly
modified with this operation. Columns designated read-only in the
schema also may not be updated.
The "count" member of the result specifies the number of rows
that matched.
Errors:
"error": "domain error"
The result of the mutation is not mathematically defined,
e.g. division by zero.
"error": "range error"
The result of the mutation is not representable within the
database's format, e.g. an integer result outside the range
INT64_MIN...INT64_MAX or a real result outside the range
-DBL_MAX...DBL_MAX.