[tproxy] Question about warning message

Balazs Scheidler bazsi@balabit.hu
Mon, 25 Aug 2003 19:54:35 +0200

On Sun, Aug 24, 2003 at 08:08:54AM +0300, Yuval Pemper wrote:
> While running stress tests on our application, which uses the tproxy 
> patch, we see the following warning messages in dmesg:
> IP_TPROXY: error applying NAT mapping, hooknum=4 ....
> This warning message comes from the function ip_tproxy_setup_nat_bidir in 
> iptable_tproxy.c. It's printed if the result of calling ip_nat_setup_info 
> is different than NF_ACCEPT.
> I'm not sure what this warning means. The ip_tproxy_setup_nat_bidir 
> function continues normally after the warning is printed out. Any help in 
> shedding light on this will be greatly appreciated.

This means that the request NAT mapping to the given foreign addr:port pair
was reserved by another possibly timewaiting connection. I am currently
thinking on adding a feature which would make source port allocation more

This usually means that the connection initiated by the proxy will go out
unNATed with the source address it originally bound to.

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