Design and Implementation

sf Firewall Software--a TCP/IP packet filter for Linux

Version 0.1, last edited on November 7th, 1996

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Table Of Contents

  1. The Structure of the sf Firewall
    1. Overview
      1. The Components
      2. Packet Handling
    2. Patching the Linux Kernel
      1. Description of the Kernel Filter Module Stub
  2. Interaction between the Components
    1. Loading the Kernel Filter Module
    2. Starting the Firewall Daemon--the Firewall Device
    3. Configuring the Filter Function through the Firewall Device
    4. Reconfiguring the Filter Function
    5. Reading the Active Rules from the Firewall Device
  3. The Firewall Daemon
    1. Detecting if the Firewall Daemon is already Running
    2. Signals and the Firewall Pipe
    3. Starting External Commands
    4. The Event Mechanism
    5. Error Handling
    6. Avoiding Duplicate Log Entries
    7. Variables and Time-Outs
    8. Counter Intelligence
  4. Enhancing the Firewall Daemon
    1. Adding New Keywords
    2. Enhancing the Counter Intelligence
  5. Configuration Data
    1. Filter Rules
    2. Notification Structure
    3. Configuring the Filter
  6. The Packet Filter
    1. Address Spoofing
    2. Fragmentation
    3. TCP
    4. Rules
    5. Log Information
    6. Configuration and Control Routines


Copyright © 1996 Robert Muchsel and Roland Schmid.

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