Linux Firewall-related /proc Entries

    Date15 Jul 2003
    CategoryFirewalls
    7702
    Posted ByAnthony Pell
    Most people, when creating a Linux firewall, concentrate soley on manipulating kernel network filters: the rulesets you create using userspace tools such as iptables (2.4 kernels,) ipchains (2.2 kernels,) or even ipfwadm (2.0 kernels). However there are kernel variables -- . . . Most people, when creating a Linux firewall, concentrate soley on manipulating kernel network filters: the rulesets you create using userspace tools such as iptables (2.4 kernels,) ipchains (2.2 kernels,) or even ipfwadm (2.0 kernels). However there are kernel variables -- independent of any kernel filtering rules -- that affect how the kernel handles network packets. This article will discuss these variables and the effect they have on the network security of your Linux host or firewall.

    There are many settings inside the Linux kernel that can vary from machine to machine. Traditionally, these were set at compile time, or sometimes were modifiable through oft-esoteric system calls. For example each machine has a host name which would be set at boot time using the sethostname(2) system call, while iptables reads and modifies your Netfilter rules using getsockopt(2) and setsockopt(2), respectively.

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