Installation guide

DC 900-1325I 79
Chapter
6
LAN Message Filtering
This chapter describes the recommended approach to implementing a server-resident
filter that edits messages moving to and from the WAN. This approach is appropriate
regardless of whether the client application transferring data executes on the Freeway
server itself (such as an SRA) or on a remote computer connected to the Freeway server
through a LAN.
The message multiplexor (msgmux) process controls the movement of all messages to
and from the WAN. Provisions are made to allow you as the application writer to “fil-
ter” these messages, changing the message content to meet your requirements. See
Figure 6–1.
Note
In the strictest sense, the term “SRA” is inappropriate for describ-
ing the filter functions because they do not comprise a stand-alone
application program, but rather are individual functions of the
msgmux task. Also, the example filter program (filter.c) is compiled
as a shared object rather than an executable application. However,
in the rest of this chapter the term “SRA” is used to refer to either
the server-resident filter function or a server-resident application.
The Freeway performs two actions designed to make running customized filter SRAs
possible:
1. It checks for the existence of a library file called fwymod.so in the directory
/usr/local/freeway/boot.src/, and if that file exists, loads it dynamically into the Free-