Re: [9fans] NAT implementation

[Patrick Kristiansen <patrick.kasserer@gmail.com>]

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2009/4/15 Devon H. O'Dell <devon.odell@gmail.com>

>
>
> I think #2 would be an easily testable and maybe more `correct' way to
> do this in Plan 9. I think doing an implementation directly in the IP
> path is easier, overall, but that's where my experience lies anyway.
>
Thanks, I'll try that.

>
>
> > Do you have any advices on how to capture packets and how to send them
> out
> > again after replacing src/dst addr and port?
>
> It's not quite that simple. At the simplest, when the packet goes out,
> you have to keep a tab of the destination host / port and source host
> / port. When a packet comes in, you look up the source host / port in
> the hash table (hashed by dest host / port). You rewrite the packet.
> You have to regenerate the packet checksum after rewriting it. You
> send it back out.


I know it's not that simple. But for the rewriting and keeping state stuff,
I can look at the existing implementations of nat, i.e. natd for freebsd.
The thing I need now is the stuff for capturing and sending packets using
pkt interfaces.

>
> > Are there any ways of testing NAT in a virtual machine? Right now I'm
> using
> > vmware and it would be nice to be able to test it without setting up a
> real
> > machine with two Ethernet interfaces.
>
> Sure, configure a couple VMs with hostonly networking and set up their
> IP addresses accordingly.
>
Nice, thanks.

>
> > -Patrick Kristiansen
>
> --dho
>
>

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