On 10/08/2013 09:42 AM, Anand Raj Manickam wrote:
On Tue, Oct 8, 2013 at 1:06 PM, Rob Sterenborg (lists)
<lists@xxxxxxxxxxxxxxx> wrote:
On 10/08/2013 07:46 AM, Anand Raj Manickam wrote:
Is there a way to bypass nat ftp helper for a few connections and
allow the rest of the FTP connections to NAT with the FTP helper
module ?
The need is to NAT the FTP control and data connections without
conntrack-helpers .
See man iptables, specifically the raw table:
raw:
This table is used mainly for configuring exemptions from connection
tracking in combination with the NOTRACK target. It registers at the
netfilter hooks with higher priority and is thus called before ip_conntrack,
or any other IP tables. It provides the following built-in chains:
PREROUTING (for packets arriving via any network interface) OUTPUT (for
packets generated by local processes)
--
Rob
Thanks for your response Rob.
The setup is a router and I m tryin to SNAT so the choice i have is on
FORWARD / POSTROUTING chain.
I need connection tracking as i need to NAT the traffic without the
nat ftp helper module .
Look at these pages:
http://doc.powerdns.com/html/recursor-performance.html
http://www.stearns.org/pomlist/20030101-output/pom-userspace.html#raw
I've never had to use the raw table nor the NOTRACK target so my info is
likely hardly authoritative. But, I guess it would work something like this:
$ipt -t raw -A PREROUTING -d <ip_ftp_server> -p tcp -m multiport \
--dports 20,21 -j NOTRACK
$ipt -t raw -A PREROUTING -s <ip_ftp_server> -p tcp -m multiport \
--dports 20,21 -j NOTRACK
If I understand things correctly, this should make connections to/from
the specified FTP server untracked.
After that, you'd need static NAT rules to forward packets to and from
the FTP server. I don't know if Netfilter does NAT without connection
tracking. If not, then maybe iproute2 can help you there:
http://linux-ip.net/html/nat-stateless.html
--
Rob
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