3Com CoreBuilder 3500, Implementation Manual

Page: 217 / 592

Tools for Writing Filters 217
Tools for Writing
Filters
The following tools can be used to create packet filters.
■
ASCII Text Editor
■
Built-in Line Editor
■
Web Management Filter Builder Tool
ASCII Text Editor
You can create a new custom packet filter using an ASCII-based text
editor (such as EMACS, vi, or Notepad). By using an ASCII-based text
editor on a networked workstation, you can create multiple copies of the
packet filter definition, which you can then store and copy onto one or
more systems from the workstation. This method also allows you to
archive copies of filter definitions and put them under source code
control.
Built-in Line Editor You can create a new custom packet filter using the line editor that is
built into the Administration Console. The built-in text editor provides a
minimal set of EMACS-style editing functions that you can use to edit a
packet filter definition one line at a time. A single line is limited to no
more than 79 characters. The number of lines is limited only by available
memory.
Because the built-in editor is deliberately limited in scope, this method is
most suited to making small temporary changes to a running filter.
The built-in editor assumes a terminal capability no higher than a glass tty
(that is, it does not assume an addressable screen). You can place any
ASCII printable character into the editing buffer at the cursor position. If
the number of characters in the line buffer exceed the maximum number
of characters permitted for the line, the characters that fall outside
maximum line length are discarded. The built-in editor initially operates in
insert
mode. Table 29 summarizes the commands that the editor
supports.