[tproxy] A general question on xt_socket
hi2arun at gmail.com
Tue Nov 4 10:32:32 CET 2008
Any updates/pointers on this?
2008/10/31 Arun Srinivasan <hi2arun at gmail.com>:
> 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
> I doubt if it has got something to do with policy routing and the socket match.
> 2008/10/30 Balazs Scheidler <bazsi at 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
> Arun S.
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