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pike Module
Bogdan-Andrei Iancu
voice-system.ro
Edited by
Bogdan-Andrei Iancu
Copyright 2003 FhG FOKUS
_________________________________________________________
Table of Contents
1. User's Guide
1.1. Overview
1.2. Dependencies
1.2.1. OpenSER 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)
1.4. Exported Functions
1.4.1. pike_check_req()
2. Developer's Guide
3. Frequently Asked Questions
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. pike_check_req usage
2-1. Tree of IP addresses
_________________________________________________________
Chapter 1. User's 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 the there is an high traffic from an
IP; what to do, is the administator decision (via scripting).
_________________________________________________________
1.2. Dependencies
1.2.1. OpenSER Modules
The following modules must be loaded before this module:
* No dependencies on other OpenSER modules.
_________________________________________________________
1.2.2. External Libraries or Applications
The following libraries or applications must be installed
before running OpenSER 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)
...
_________________________________________________________
1.4. 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.
IMPORTANT: in case of internal error, the function returns
true to avoid reporting the current processed IP as blocked.
This function can be used from REQUEST_ROUTE.
Example 1-4. pike_check_req usage
...
if (!pike_check_req()) { break; };
...
_________________________________________________________
Chapter 2. Developer's 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.
_________________________________________________________
Chapter 3. Frequently Asked Questions
3.1. Where can I find more about OpenSER?
3.2. Where can I post a question about this module?
3.3. How can I report a bug?
3.1. Where can I find more about OpenSER?
Take a look at http://openser.org/.
3.2. Where can I post a question about this module?
First at all check if your question was already answered on
one of our mailing lists:
* User Mailing List -
http://openser.org/cgi-bin/mailman/listinfo/users
* Developer Mailing List -
http://openser.org/cgi-bin/mailman/listinfo/devel
E-mails regarding any stable OpenSER release should be sent to
<users@openser.org> and e-mails regarding development versions
should be sent to <devel@openser.org>.
If you want to keep the mail private, send it to
<team@openser.org>.
3.3. How can I report a bug?
Please follow the guidelines provided at:
http://sourceforge.net/tracker/?group_id=139143.
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