nat:REDIRECT on localhost not working in Kernel 2.6

[Stephan Uhlmann <su@su2.info>]

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Hello netfilter friends,

I want to redirect all connections going to port 80 of a host to port 8080 of 
the same host. Of course I do it with the REDIRECT target:

iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8080
iptables -t nat -A OUTPUT -p tcp --dport 80 -j REDIRECT --to-ports 8080

The redirection of externally incoming connections via PREROUTING  works 
perfectly fine.

But I have the problem that locally generated connections are not redirected 
on machines with Linux Kernel 2.6 but on machines with Linux Kernel 2.4.

I tested:
SuSE Linux 9.0 (Kernel 2.4.21, iptables v1.2.8)  - works
SuSE Linux 9.1 (Kernel 2.6.5,  iptables v1.2.9)  - does not work
SuSE Linux 9.2 (Kernel 2.6.8,  iptables v1.2.11) - does not work
Gentoo Linux   (Kernel 2.6.9,  iptables v1.2.11) - does not work

"iptables -t nat -L -v" shows that no packet at all was catched by the OUTPUT 
chain. Instead it seems to go to the POSTROUTING chain. But the REDIRECT 
target can't be used in the POSTROUTING chain.

Is this a bug? Is this a feature? Did something change between Kernel 2.4 and 
2.6 in this regard?

I looked through the ChangeLogs and other docs but didn't find any hint.


Stephan

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