pike Module

Bogdan-Andrei Iancu

   voice-system.ro

Edited by

Bogdan-Andrei Iancu

   Copyright © 2003 FhG FOKUS
   Revision History
   Revision $Revision: 4630 $ $Date: 2008-08-06 12:08:33 +0200
                              (Mi, 06 Aug 2008) $
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview
        1.2. Dependencies

              1.2.1. Kamailio Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. sampling_time_unit (integer)
              1.3.2. reqs_density_per_unit (integer)
              1.3.3. remove_latency (integer)
              1.3.4. pike_log_level (integer)

        1.4. Exported Functions

              1.4.1. pike_check_req()

        1.5. Exported MI Functions

              1.5.1. pike_list

   2. Developer Guide

   List of Examples

   1.1. Set sampling_time_unit parameter
   1.2. Set reqs_density_per_unit parameter
   1.3. Set remove_latency parameter
   1.4. Set pike_log_level parameter
   1.5. pike_check_req usage
   2.1. Tree of IP addresses

Chapter 1. Admin Guide

1.1. Overview

   The module keeps trace of all (or selected ones) incoming
   request's IP source and blocks the ones that exceeded some
   limit. Works simultaneous for IPv4 and IPv6 addresses.

   The module does not implement any actions on blocking - it just
   simply reports that there is a high traffic from an IP; what to
   do, is the administator decision (via scripting).

1.2. Dependencies

1.2.1. Kamailio Modules

   The following modules must be loaded before this module:
     * No dependencies on other Kamailio modules.

1.2.2. External Libraries or Applications

   The following libraries or applications must be installed
   before running Kamailio with this module loaded:
     * None.

1.3. Exported Parameters

1.3.1. sampling_time_unit (integer)

   Time period used for sampling (or the sampling accuracy ;-) ).
   The smaller the better, but slower. If you want to detect
   peeks, use a small one. To limit the access (like total number
   of requests on a long period of time) to a proxy resource (a
   gateway for ex), use a bigger value of this parameter.

   IMPORTANT: a too small value may lead to performance penalties
   due timer process overloading.

   Default value is 2.

   Example 1.1. Set sampling_time_unit parameter
...
modparam("pike", "sampling_time_unit", 10)
...

1.3.2. reqs_density_per_unit (integer)

   How many requests should be allowed per sampling_time_unit
   before blocking all the incoming request from that IP.
   Practically, the blocking limit is between ( let's have
   x=reqs_density_per_unit) x and 3*x for IPv4 addresses and
   between x and 8*x for ipv6 addresses.

   Default value is 30.

   Example 1.2. Set reqs_density_per_unit parameter
...
modparam("pike", "reqs_density_per_unit", 30)
...

1.3.3. remove_latency (integer)

   For how long the IP address will be kept in memory after the
   last request from that IP address. It's a sort of timeout
   value.

   Default value is 120.

   Example 1.3. Set remove_latency parameter
...
modparam("pike", "remove_latency", 130)
...

1.3.4. pike_log_level (integer)

   Log level to be used by module to auto report the blocking
   (only first time) and unblocking of IPs detected as source of
   floods.

   Default value is 1 (L_WARN).

   Example 1.4. Set pike_log_level parameter
...
modparam("pike", "pike_log_level", -1)
...

1.4. Exported Functions

1.4.1.  pike_check_req()

   Process the source IP of the current request and returns false
   if the IP was exceeding the blocking limit.

   Return codes:
     * 1 (true) - IP is not to be blocked or internal error
       occured.

Warning
       IMPORTANT: in case of internal error, the function returns
       true to avoid reporting the current processed IP as
       blocked.
     * -1 (false) - IP is source of flooding, being previously
       detected
     * -2 (false) - IP is detected as a new source of flooding -
       first time detection

   This function can be used from REQUEST_ROUTE.

   Example 1.5. pike_check_req usage
...
if (!pike_check_req()) { exit; };
...

1.5. Exported MI Functions

1.5.1.  pike_list

   Lists the nodes in the pike tree.

   Name: pike_list

   Parameters: none

   MI FIFO Command Format:
                :pike_list:_reply_fifo_file_
                _empty_line_

Chapter 2. Developer Guide

   One single tree (for both IPv4 and IPv6) is used. Each node
   contains a byte, the IP addresses stretching from root to the
   leafs.

   Example 2.1. Tree of IP addresses
           / 193 - 175 - 132 - 164
tree root /                  \ 142
          \ 195 - 37 - 78 - 163
           \ 79 - 134

   To detect the whole address, step by step, from the root to the
   leafs, the nodes corresponding to each byte of the ip address
   are expanded. In order to be expended a node has to be hit for
   a given number of times (possible by different addresses; in
   the previous example, the node "37" was expended by the
   195.37.78.163 and 195.37.79.134 hits).

   For 193.175.132.164 with x= reqs_density_per_unit:
     * After first req hits -> the "193" node is built.
     * After x more hits, the "175" node is build; the hits of
       "193" node are split between itself and its child--both of
       them gone have x/2.
     * And so on for node "132" and "164".
     * Once "164" build the entire address can be found in the
       tree. "164" becomes a leaf. After it will be hit as a leaf
       for x times, it will become "RED" (further request from
       this address will be blocked).

   So, to build and block this address were needed 3*x hits. Now,
   if reqs start coming from 193.175.132.142, the first 3 bytes
   are already in the tree (they are shared with the previous
   address), so I will need only x hits (to build node "142" and
   to make it "RED") to make this address also to be blocked. This
   is the reason for the variable number of hits necessary to
   block an IP.

   The maximum number of hits to turn an address red are (n is the
   address's number of bytes):

   1 (first byte) + x (second byte) + (x / 2) * (n - 2) (for the
   rest of the bytes) + (n - 1) (to turn the node to red).

   So, for IPv4 (n = 4) will be 3x and for IPv6 (n = 16) will be
   9x. The minimum number of hits to turn an address red is x.
