&Attribute References

Syntax

&Attribute-Name

The &Attribute-Name operator returns a reference to the named attribute.

When used as an existence check in a condition, the condition evaluates to true if the attribute exists. Otherwise, the condition evaluates to false.

When used elsewhere, such as in switch, it returns the value of the named attribute.

Examples

&User-Name
&NAS-IP-Address

Lists

The attribute reference can also be qualified with a list reference. When no list is given, the server looks in the input packet list for the named attribute.

Examples

&request.User-Name
&reply.NAS-IP-Address

Array References

Syntax

&Attribute-Name[<integer]

When an attribute appears multiple times in a list, this syntax allows you to address the attributes as if they were array entries. The <integer> value defines which attribute to address. The [0] value refers to the first attributes, [1] refers to the second attribute, etc.

Examples

&EAP-Message[1]
&reply.NAS-IP-Address[2]

Parent / child references

Syntax

&Attribute-Name.Attribute-Name

In some cases, attributes are nested or grouped. The child reference syntax is used to address a particular child attribute. Multiple levels of parent / child nesting can be performed by simply appending the name of another child attribute, separated by the . character.

Examples

&TLV-One.Child-one
&TLV-One.Child-one.Child-Three
&reply.TLV[3].Child-Two

Putting it All Together

All of the above syntaxes can be used interchangeably, at any nesting level. The examples are presented

Examples

&TLV-One.Child-one[3].Child-Three
&reply.TLV[3].Child-Two

Removing ambuguity from the configuration files

The server does not use the & character to distinguish attribute names from other strings.

Without the &, it is more difficult to parse the configuration file clearly. You could interpret a string as hello-there either as a literal string "hello-there", or as a reference to an attribute named hello-there.

Adding the leading & character means that attribute references are now easily distinguishable from literal strings. The use of the leading & character is highly recommended.