pike Module

Bogdan-Andrei Iancu

Voice Sistem SRL

Edited by

Bogdan-Andrei Iancu

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. sampling_time_unit (integer)
3.2. reqs_density_per_unit (integer)
3.3. remove_latency (integer)
3.4. pike_log_level (integer)
4. Functions
4.1. pike_check_req()
5. MI Commands
5.1. pike_list
2. RPC calls
1. pike.top
3. 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
3.1. Tree of IP addresses

Chapter 1. Admin Guide

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).

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • No dependencies on other Kamailio modules.

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

  • None.

3. Parameters

3.1. sampling_time_unit (integer)

Time period in seconds 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)

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)

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, in seconds. Note that it is not the duration to keep the IP in state 'blocked'. An IP is unblocked next occurence of 'sampling_time_unit' that does not exceed 'reqs_density_per_unit'. Keeping an IP in memory results in faster reaching of blocked state -- see the notes about the limits of getting to state 'blocked'.

Default value is 120.

Example 1.3. Set remove_latency parameter

modparam("pike", "remove_latency", 130)

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)

4. Functions

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.


    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; };

5. MI Commands

5.1.  pike_list

Lists the nodes in the pike tree.

Name: pike_list

Parameters: none

MI FIFO Command Format:


Chapter 2. RPC calls

Table of Contents

1. pike.top

1.  pike.top

Pike.top behaves like a 'top' command and shows source IP addresses of incoming requestes to pike_check_req() function.

The IP list is sorted by sum of leaf hits (prev and curr) descending and in second level by hits.

Some IPs could be marked as HOT depending on theirs request rates.

pike.top command takes one string parameter which specifies what kind of nodes you are interested in. Possible values are HOT or ALL. If no argument is given, it behaves as HOT was used.

Marking nodes HOT is done on server side, client only presents given data and make some postprocessing like sorting.

Output of this command is a simple dump of ip_tree nodes marked as ip-leafs.

Chapter 3. 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 3.1. 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 and hits).

For 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, 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.