Blue Coat Systems Proxy SG manual Exception Layers, Forward Layers

Chapter 2: Managing Content Policy Language

<Exception> Layers

<Exception> layers are evaluated when a proxy transaction is terminated by an exception. This could be caused by a bad request (for example, the request URL names a non-existent server) or by setting the deny or exception() properties in policy. Policy in an exception layer can be used to control how access logging is performed for exceptions, such as authentication_failed. It can also be used to modify the HTTP response headers in the exception page that is sent to the client.

The syntax is:

<Exception [label]> [exception_condition][exception_properties] ...

exception_content

where:

•The <Exception> layer defines the transactions evaluated against this policy, and restricts the triggers and properties allowed in the rules used in the layer.

•The optional label, separated from the layer type by space, is a CPL User-defined Identifier.

•The optional exception_condition is a list of triggers, all of which must evaluate to true before the layer content is evaluated. For more information on using conditions, see Chapter 3: "Condition Reference". See also the following Layer Guards section.

•The optional exception_properties is a list of properties set if any of the rules in the layer match. These act as defaults, and can be overridden by property settings in specific rules in the layer. For more information on using properties, see Chapter 4: "Property Reference". See also the following Layer Guards section.

<Forward> Layers

<Forward> layers are evaluated when the current transaction requires an upstream connection (and only then: forward policy will not be evaluated for a cache hit). <Forward> layers use the server_url= tests rather than the url= tests so that they are guaranteed to honor any policy that rewrites the URL.

The syntax is:

<Forward [label]> [forward_condition][forward_properties] ...

forward_content

where:

•The <Forward> layer defines the transactions evaluated against this policy, and restricts the triggers and properties allowed in the rules used in the layer.

•The optional label, separated from the layer type by space, is a CPL User-defined Identifier.

•The optional forward_condition is a list of triggers, all of which must evaluate to true before the layer content is evaluated. For more information on using conditions, see Chapter 3: "Condition Reference". See also the following Layer Guards section.

•The optional forward_properties is a list of properties set if any of the rules in the layer match. These act as defaults, and can be overridden by property settings in specific rules in the layer. For more information on using properties, see Chapter 4: "Property Reference". See also the following Layer Guards section.

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