Yes. I verified that. Also fy/i, when I enable simplex transparency (only to the client), proxy-1 to proxy-2 communication is successful. Find below the rules used for this scenario: iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to <proxy-1 port> iptables -t nat -A OUTPUT -p tcp --dport 80 -j DNAT --to <intf-ip>:<proxy2-port> With tproxy-mark enabled, am not able to achieve this. Also it was observed that the conntrack state for the OUTPUT-NAT immediately gets into CLOSE state as shown below. ipv4 2 tcp 6 8 CLOSE src=<client-IP> dst=<web_server-IP> sport=61000 dport=80 packets=3 bytes=140 src=<intf-ip> dst=<client-IP> sport=<proxy2-port> dport=61000 packets=1 bytes=60 mark=0 secmark=0 use=1 I doubt if it has got something to do with policy routing and the socket match. 2008/10/30 Balazs Scheidler <bazsi@balabit.hu>:
On Thu, 2008-10-30 at 01:24 +0530, Arun Srinivasan wrote:
Thank you.
Currently am facing an issue.. dunno if it is an issue. please clarify.
In a Linux box with tproxy4 (tproxy4-2.6.26-200809262032), I have two proxies, proxy-1 listening on port x and proxy-2 on port y.
With the tproxy rules (tproxy-mark, -m socket, and policy routing), I could redirect the incoming traffic to proxy-1 that listens on port x. However, the request from proxy-1 could not be redirected to proxy-2.
The second redirection from proxy-1 from proxy-2 is attempted through NAT - OUTPUT rule.
The configured rules are given below: ++++++++++++ FOR PROXY-1 +++++++++++++++ iptables -t mangle -A PREROUTING -p tcp --dport 80 -j TPROXY --on-port <proxy-1 port> --tproxy-mark 0x1/0x1 ip rule add fwmark 0x1 lookup 100 ip route add local 0.0.0.0/0 dev lo table 100
iptables -t mangle -N DIVERT iptables -t mangle -I PREROUTING -p tcp -m socket -j DIVERT iptables -t mangle -A DIVERT -j MARK --set-mark 0x1 iptables -t mangle -A DIVERT -j ACCEPT +++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++ FOR PROXY-2 +++++++++++++++++++++++++++++++++++++ iptables -t nat -A OUTPUT -p tcp --dport 80 -j DNAT --to <Interface IP>:<proxy-2 port> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The rule for proxy-2 makes only the TCP-SYN packet from proxy-1 to be redirected. Three-way handshake is not successful.
Am I missing out anything or is this the intended behavior?
This DNAT is a different matter, it has no connection to tproxy. Please check where the SYN-ACK is going (via tcpdump), it should be properly NAT-ed both ways.
Please check the conntrack table whether the appriopriate NAT mapping is there.
-- Bazsi
-- Regards, Arun S.