Linux-kernel mailing list archive 1998-42,: Re: Dynamic IP hack (PR#294)

# Re: Dynamic IP hack (PR#294)

Malware (Michael.Mueller4@post.rwth-aachen.de)
Sun, 18 Oct 1998 21:19:23 +0200

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Hi Andi,

you wrote:
> > > > Also, seems, this patch does not guarantee, that socket in established
> > > > state is not mangled. Not good.
> > >
> > > It's not a bug it's the feature. :-) If bit 2 (mask value 4) of
> > > sysctl_ip_dynaddr is set this does mean all packets are rewritten this
> > > does include these belonging to established connections. The goal is to
> > > avoid sending out packets with an invalid source address in order to get
> > > atleast an RST back.
> >
> > I apologize, but this thing is impossible to classify as a feature.
>
> Yes, it is not acceptable. IFF_DYNAMIC is much better @)

As I allready wrote I accept your idea to be the better way. But it
still needs the help of the old DynIP-hack to serve the purpose. On the
other hand the code I posted does allready work and I experienced no
problem in the daily use. Additionally it can be switched on/off on
runtime so that people who experience problems do not need to hassle
with it.

The IFF_DYNAMIC flag will change a lot for the local sockets but next to
nothing for masqueraded connections. I see three ways for masqueraded
TCP connections in ESTABLISHED state:

1. let the retransmits through as it currently happens
=> it still needs a RST from the other side to get the socket down

2. drop all packets that have masquerading entries with the wrong source
address
=> they timeout

3. send a faked RST to the source of masquereded connections as soon as
the source address is invalid
=> they will disappear fast

I think 2. is the cleanest solution for this case.

Malware

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