Help in extending netfilter


 
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Old 09-13-2005
Help in extending netfilter

Hi everybody,
I have to write a module for matching in netfilter , extending the netfilter but I'm facing some problems can somebody guide me in that. I know that I need to write matching module working in kernel space and a program in userspace. I went through the HOWTO on netfilter-hacking but faced following problems :
1. In kernel module how is match function different from checkentry function (I got this confusion because a 0 return in checkentry and setting hotdrop to 1 seemed to do same thing). Please explain the meaning of each function elaborately.

2. As described in the HOWTO there is a structure in header file iptables.h that I need for program in userspace but I'm not able to locate this headerfile where can I find it.

If possible please send me an example of any module with both the kernel module and program for taking user input in userspace.

Thanks in advance.

Last edited by Trusted Penguin; 09-15-2005 at 11:59 AM..
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FIREWALLD.SERVICE(5)						 firewalld.service					      FIREWALLD.SERVICE(5)

NAME
firewalld.service - firewalld service configuration files SYNOPSIS
/etc/firewalld/services/service.xml /usr/lib/firewalld/services/service.xml DESCRIPTION
A firewalld service configuration file provides the information of a service entry for firewalld. The most important configuration options are ports, modules and destination addresses. This example configuration file shows the structure of an service configuration file: <?xml version="1.0" encoding="utf-8"?> <service> <short>My Service</short> <description>description</description> <port port="137" protocol="tcp"/> <module name="nf_conntrack_netbios_ns"/> <destination ipv4="224.0.0.251" ipv6="ff02::fb"/> </service> OPTIONS
The config can contain these tags and attributes. Some of them are mandatory, others optional. service The mandatory service start and end tag defines the service. This tag can only be used once in a service configuration file. There are optional attributes for services: version="string" To give the service a version. short Is an optional start and end tag and is used to give an icmptype a more readable name. description Is an optional start and end tag to have a description for a icmptype. port Is an optional empty-element tag and can be used several times to have more than one port entry. All attributes of a port entry are mandatory: port="string" The port string can be a single port number or a port range portid-portid or also empty to match a protocol only. protocol="string" If a port is given, the protocol value can either be tcp or udp. If no port is given, it can be any protocol from /etc/protocols to have a protocol match only. module Is an optional empty-element tag and can be used several times to enable more than one netfilter kernel helper for the service. A module entry has exactly one attribute: name="string" Defines the name of the kernel netfilter helper as a string. destination Is an optional empty-element tag and can be used only once. The destination specifies the destination network as a network IP address (optional with /mask), or a plain IP address. The use of hostnames is not recommended, because these will only be resolved at service activation and transmitted to the kernel. For more information in this element, please have a look at --destination in iptables(8) and ip6tables(8). ipv4="address[/mask]" The IPv4 destination address with optional mask. ipv6="address[/mask]" The IPv6 destination address with optional mask. SEE ALSO
firewall-applet(1), firewalld(1), firewall-cmd(1), firewall-config(1), firewalld.conf(5), firewalld.direct(5), firewalld.icmptype(5), firewalld.lockdown-whitelist(5), firewall-offline-cmd(1), firewalld.richlanguage(5), firewalld.service(5), firewalld.zone(5), firewalld.zones(5) NOTES
firewalld home page at fedorahosted.org: http://fedorahosted.org/firewalld/ More documentation with examples: http://fedoraproject.org/wiki/FirewallD AUTHORS
Thomas Woerner <twoerner@redhat.com> Developer Jiri Popelka <jpopelka@redhat.com> Developer firewalld 0.3.9 FIREWALLD.SERVICE(5)