Книга: Linux Network Administrator Guide, Second Edition
The Lefthand Side
The Lefthand Side
In the lefthand side of a rewriting rule, you specify a pattern that will match an address you wish to transform. Most characters are matched literally, but there are a number of characters that have special meaning; these are described in the following list. The rewrite rules for the lefthand side are:
$@
Match exactly zero tokens
$*
Match zero or more tokens
$+
Match one or more tokens
$-
Match exactly one token
$= x
Match any phrase in class x
$~ x
Match any word not in class x
A token is a string of characters delimited by spaces. There is no way to include spaces in a token, nor is it necessary, as the expression patterns are flexible enough to work around this need. When a rule matches an address, the text matched by each of the patterns in the expression will be assigned to special variables that we'll use in the righthand side. The only exception to this is the $@, which matches no tokens and therefore will never generate text to be used on the righthand side.
Оглавление книги
- The Righthand Side
- 4.4.4 The Dispatcher
- About the author
- Chapter 7. The state machine
- Appendix E. Other resources and links
- Example NAT machine in theory
- The final stage of our NAT machine
- Compiling the user-land applications
- The conntrack entries
- Untracked connections and the raw table
- Speed considerations
- Basics of the iptables command