ipfw and carp problems

[Gerhard Schmidt]

Am 01.11.2014 06:56, schrieb Ian Smith:
> On Wed, 29 Oct 2014 20:55:16 +1100, Ian Smith wrote:
>  > In freebsd-questions Digest, Vol 543, Issue 2, Message: 1
>  > On Mon, 27 Oct 2014 15:16:33 +0100 Gerhard Schmidt <schmidt at ze.tum.de> wrote:
>  >  > Hi,
>  >  > 
>  >  > I have a small problem with ipfw an carp.
>  >  > 
>  >  > i have two server with two carp ips and a firewall via ipfw.
>  >  > 
>  >  > the problem is tha ipfw via modul is default to deny. So when the carp
>  >  > interfaces are initialized ipfw has no custom rules. Everything is
>  >  > denied, even the carp packets. So every time I reboot one of the hosts
>  >  > it comes up as master and after the firewall rules are initialized one
>  >  > of the servers is demoted to backup, which one seams to be random.
>  >  > 
>  >  > My problem is that my setup need a new server do come up as backup
>  >  > because is has to replicate the data from the running server before
>  >  > being able to act as master. There could be data loss if a newly booted
>  >  > server named master without prior replicating the data.
>  >  > 
>  >  > Is there a way to ensure that the firewall rules are up before the carp
>  >  > interfaces are initialized or to load the ipfw module with default to
>  >  > accept.
>  > 
>  > The canonical way was to build a custom kernel with ipfw included as per 
>  > http://www.freebsd.org/doc/handbook/firewalls-ipfw.html including 
>  > 'options IPFIREWALL_DEFAULT_TO_ACCEPT' .. however you can accomplish 
>  > this with a GENERIC (or other) kernel by adding to /boot/loader.conf:
>  > 
>  >   ipfw_load="YES"		# to load the ipfw module early
>  > 
>  > and adding to /etc/sysctl.conf
>  > 
>  >   net.inet.ip.fw.enable=0
>  >   net.inet6.ip6.fw.enable=0	# if using ipv6
>  > 
>  > /etc/rc.d/sysctl is run early (on 9.3, first) before other rc.d 
>  > scripts including netif and later ipfw, which will then only enable the 
>  > firewall after having loaded your ruleset.
>  > 
>  > I just tested this over ssh to a 9.3 GENERIC box not running ipfw:
>  > 
>  > root at x200:~/bin # kldload ipfw && sysctl net.inet.ip.fw.enable=0 \
>  > 	&& sysctl net.inet6.ip6.fw.enable=0
>  > net.inet.ip.fw.enable: 1 -> 0
>  > net.inet6.ip6.fw.enable: 1 -> 0
>  > root at x200:~/bin # ipfw show
>  > 65535 0 0 deny ip from any to any
>  > 
>  > which would have locked me out had it not worked :)
>  > 
>  > Of course you must accept that there is a vulnerable window between 
>  > starting net interfaces (netif) and starting ipfw, however miniscule.
> 
> Excuse replying to my own message, but I've since discovered that you 
> could also add 'net.inet.ip.fw.default_to_accept=1' to loader.conf as an 
> alternative.  I hadn't twigged that this one is a loader tunable, unlike 
> the sysctls mentioned above, and so can be set before ipfw.ko is loaded, 
> ie before the net.inet.ip[6].fw OIDs even exist.
> 
> Please let the list know if either of these methods solve your issue?

Sorry was out of town for a view days.

I did solve my problem with activating the default_to_accept tunable.

Since this server should be running 24/7 the slight exposure on start up
shouldn't be a problem especially because the services protected are
started way after firewall is initialized.

Regards
   Estartu


-- 
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Gerhard Schmidt                | E-Mail: schmidt at ze.tum.de
Technische Universität München | Jabber: estartu at ze.tum.de
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Tel: +49 89 289-25270          | PGP-PublicKey
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