FreeRADIUS InkBridge

Expressions

Expressions can be used inside of dynamic expansions, or inside of conditions.

The following operators are supported (in order of precedence).

Operator Description

&

binary AND

|

binary OR

<<

left shift

>>

right shift

+

addition

-

subtraction

*

multiplication

/

division

%

remainder

^

xor

(…​)

sub-expression

The following unary operators are also supported:

Operator Description

-

unary minus

~

unary complement

!

unary not

Operator precedence follows the normal rules. Division by zero means that the entire expression is invalid.

See the edit documentation for a list of attribute editing operators.

Conditions

Conditions in expressions are also supported. For example:

&NAS-Port = 5 + (&User-Name == "bob")

This expression will return 6 if the users name is bob, and 5 otherwise.

Similarly, expressions are also supported in conditions. There is no need to use %{expr:…​} in conditions, as was needed in earlier versions of the server. You can just use math in-place.

You do not even need to use %{expr:…​} in double-quoted strings. You can just put math in-place, as with the following example:

&Filter-Id = "Adding %{NAS-Port} + 4 = %{&NAS-Port + 4}"

Data Types

The new expression parser accepts significantly more data types than the old rlm_expr module. The rlm_expr module assumed that all inputs were signed 64-bit integers. Any attempt to use other data types resulted in an error.

For example, the ` operator can be applied to `string` and `octet` data types. (And incidentally, `-` is the inverse of `!)

&Reply-Message := "foo" + "bar"

Will result in &Reply-Message == "foobar".

The suffix can then be "subtracted" off, with:

&Reply-Message -= "bar"

Will result in &Reply-Message == "foo" !.

Note that the -= operator behaves differently from earlier versions of the server! Since the server no longer needs update sections, we could re-purpose the operator.

Other data types will generally yield results which make sense. For example:

  • adding an integer to an ipv4prefix type will result in an ipv4addr data type,

  • & and | will work on string and octets data types,

  • Using & with ipv4addr data types an uint32 will result in an ipv4prefix data type,

  • `ipv4addr`s can be subtracted, and will return a number,

  • date`s can be subtracted, and will return a `time_delta,

  • operations on integers are upgraded to the next largest integer size when necessary,

  • the logical operators && and || return the value which caused them to succeed, e.g. &Foo := (&User-Password || "help") will return the contents of &User-Name if it exists, otherwise it will return the string help.

In most cases, the data types are derived from the attribute dictionaries. However, it is sometimes necessary to force the fields (or output) of an expression to be parsed in a particular manner.

Casts

Type casting is supported via the (type) syntax. The old-style syntax of <type> is accepted, but is deprecated.

&NAS-Port-Id = (uint32) "%sql("SELECT...") + 4

Errors

Mathematical operations which cause overflow, underflow, or division by zero will return a null result. This result will propagate through any calculations, so that an expression which relies on null will generally also return null.

A null result can be removed via the || operator. For example:

&NAS-Port-Id = (5 - "foo") || 6

Will return 6, as the left side expression of the || operator evaluates to null.