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Date:      Thu, 16 Aug 2001 14:30:38 -0700
From:      "Crist J. Clark" <cristjc@earthlink.net>
To:        Simon Williams <freebsd-questions@FreeBSD.ORG>
Subject:   Re: LINT & IPFIREWALL options
Message-ID:  <20010816143038.J4232@blossom.cjclark.org>
In-Reply-To: <Y%2BVMc%2BTyMDf7Ewcq@sis-domain.demon.co.uk>; from freebsd@sis-domain.demon.co.uk on Thu, Aug 16, 2001 at 09:55:14PM %2B0100
References:  <Y%2BVMc%2BTyMDf7Ewcq@sis-domain.demon.co.uk>

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On Thu, Aug 16, 2001 at 09:55:14PM +0100, Simon Williams wrote:

[snip]

> After reading through the kernel customisation part of the handbook, I 
> copied the GENERIC file (in /usr/src/sys/i386/conf) to a file named 
> CUSTOM & started editing it.  I removed support for all the hardware I 
> don't have, leaving in a couple of types of network card that I may use 
> later on.  I also saw IPFIREWALL & friends in LINT, but not in CUSTOM, 
> so I added the following lines:

As pointed out in the inline documentation of LINT,

> options         MROUTING

This option is for multicast routing. Are you doing multicast?
Probably not.

> options         IPFIREWALL
> options         IPFIREWALL_VERBOSE

You want these two. Enables ipfw(8) in the kernel and logging from
ipfw(8).

> options         IPFIREWALL_FORWARD

You probably do not want this. You only need it if you will have 'fwd'
rules in your firewall.

> options         IPFIREWALL_VERBOSE_LIMIT=100

I like to raise this a bit.

> options         IPV6FIREWALL
> options         IPV6FIREWALL_VERBOSE
> options         IPV6FIREWALL_VERBOSE_LIMIT=100

If you aren't using IPv6, don't add them.

> options         IPDIVERT

This is if you have 'divert' rules in your firewall which are usually
associated with doing NAT. Will you be doing NAT?

> options         IPFILTER
> options         IPFILTER_LOG
> options         IPFILTER_DEFAULT_BLOCK

These are for IPFilter, ipf(5,8), not ipfw(8). More below.

> options         IPSTEALTH

This is a good way to DoS yourself. If you don't know what it does,
you don't need it.

> Now when I booted this kernel, it recognised the network card, but a 
> ping returned "No route to host."

It is more likely that your firewall is misconfigured and not a
problem with the kernel per sae. 

>  From reading some past posts from this list, I saw that IPFilter is 
> another (old?) firewall application.  Does this mean those lines are for 
> ipfilter instead of ipfw?

Yep. IPFilter is a third party firewall maintained outside of
FreeBSD. It is included in the base distribution and is maintained
within FreeBSD by the author.

> Now that I have a working kernel & firewall, I just wanted to know why 
> LINT shows firewall options that aren't in GENERIC, yet firewalling 
> still works?

Are you rebooting to start the firewall? The boot sequence will
automagically load the ipfw(8) kernel module, /modules/ipfw.ko, at
boot if firewalling is enabled according to rc.conf(5).

> Also, this box will be doing firewalling/bandwidth 
> limiting/routeing (for an IP block) in about a weeks time; is there 
> anything I need to do to the kernel to support that or is it just ipfw 
> commands from here?

A few more things to add. See dummynet(4).
-- 
Crist J. Clark                           cjclark@alum.mit.edu

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