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Date:      Tue, 4 Dec 2001 12:21:12 +0000
From:      Neil Darlow <neil@darlow.co.uk>
To:        freebsd-questions@freebsd.org
Subject:   ipfw rules lost
Message-ID:  <200112041221.fB4CLDM01931@router.darlow.co.uk>
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Hi,

I am running FreeBSD-4.4-RELENG as a cable router/firewall using ipfw and the 
simple ruleset.

This morning when attempting to login remotely via SSH I was locked out. 
Attaching a console and examining /var/log/messages showed the following 
messages:

Dec  4 05:38:20 router natd[273]: failed to write packet back (No route to 
host)
Dec  4 05:38:22 router natd[273]: failed to write packet back (No route to 
host)
Dec  4 05:38:22 router dhclient: New IP Address(rl0): 213.107.35.101
Dec  4 05:38:22 router dhclient: New Subnet Mask (rl0): 255.255.255.0
Dec  4 05:38:22 router dhclient: New Broadcast Address(rl0): 255.255.255.255
Dec  4 05:38:22 router dhclient: New Routers: 213.107.35.254
Dec  4 05:51:12 router ntpd[299]: sendto(130.159.196.118): Permission denied
Dec  4 07:38:22 router dhclient: send_packet: Permission denied

I use the simple ruleset of /etc/rc.firewall with overridden interface 
arguments provided by a dhclient-exit-hooks script. The override file had 
been updated at 05:38:22 and it's contents were as follows:

# Sourced by /etc/rc.firewall (simple)
oif=rl0
onet=213.107.35.0
omask=255.255.255.0
oip=213.107.35.101

Moving on, I decided to list the current contents of the ipfw ruleset and was 
surprised to see the following:

00100 allow ip from any to any via lo0
00200 deny ip from any to 127.0.0.0/8
00300 deny ip from 127.0.0.0/8 to any
65535 deny ip from any to any

This looks like the closed ruleset in /etc/rc.firewall. So for some reason 
the simple ruleset had been replaced by the closed ruleset. My 
dhclient-exit-hooks script contains the following logic to update the ipfw 
rules:

create_new_network() {
    local new_ip_address new_subnet_mask
    unset new_network

    while [ "${new_subnet_mask%.0}" != "$new_subnet_mask" ]
    do
        new_ip_address=${new_ip_address%.*}
        new_subnet_mask=${new_subnet_mask%.0}
        new_network=$new_network.0
    done

    new_network=$new_ip_address$new_network
    new_network=${new_network#.}
    new_network=${new_network%.255.255.255.255}
}

output_new_settings() {
    echo "# Sourced by /etc/rc.firewall (simple)" > /var/db/dhclient.override
    echo "oif=$interface" >> /var/db/dhclient.override
    echo "onet=$new_network" >> /var/db/dhclient.override
    echo "omask=$new_subnet_mask" >> /var/db/dhclient.override
    echo "oip=$new_ip_address" >> /var/db/dhclient.override
}

case "$reason" in
    BOUND|REBOOT)
        create_new_network
        output_new_settings
        . /etc/rc.firewall
        ;;
    REBIND|RENEW)
        if [ "$new_ip_address" != "$old_ip_address" -o \
             "$new_subnet_mask" != "$old_subnet_mask" ]
        then
            create_new_network
            output_new_settings
            . /etc/rc.firewall
        fi
        ;;
    *)
esac

This scheme has been working ok until today and I have tested it across IP 
address changes. Can anyone suggest where I might be going wrong or what 
might have caused this unexpected failure?

Regards,
Neil Darlow M.Sc.

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