Flexible hostname lookup when using a proxy

Flexible hostname lookup is needed when using a proxy.

CICS acting as a client can consume services/APIs on both internal (customer) and external (internet) networks. When consuming external services, CICS needs to route requests out through a proxy in order to access the internet. CICS provides samples programs DFH$WBPI and DFH$WBEX to deliver this capability. Documentation for DFH$WBEX suggests, "... you can load or build a table that matches host names to appropriate proxy servers or marks them as barred, which can then be used as a look-up table during processing of the EXEC CICS WEB OPEN command.".

Sample program DFH$WBEX makes the routing decision based on the hostname of the target service. However the sample implementation is quite simplistic, making the decision based on a hard-coded hostname prefix of 'www'. The limitations are:
- only a single filter value is supported;
- the filter value is a prefix only;
- the filter value is hard-coded within the assembler code, which reduces visibility of the configuration to application development and support teams, and requires systems programmers to manage application configuration;
- the sample is written in assembler, and skills to enhance the sample further are scarce.

In reality a more sophisticated solution is needed, with 1 or more of the following features:
- support a list of multiple hostnames;
- support wildcards in filter pattern matching, or specifically a way to specify a hostname suffix;
- externalise the filter specification (perhaps to a USS file) rather than hard-coding in the program;
- if customisation of a sample program will be required, provide the sample in a maintainable form, perhaps written in C.

Example hostname specification for services hosted externally:
partner.*.transport.gov.au
*.service-now.com
portal.motorweb.com.au

Refer to discussion with Alan Hollingshead via CICS Advocacy.