On Thursday, February 17, 2005 09:31:04 PM +0100 Niels Möller <nisse%lysator.liu.se@localhost> wrote:
Jeffrey Hutzelman <jhutz%cmu.edu@localhost> writes:We should be careful to specify exactly what we mean by "localhost", "127.0.0.1", and "::1". Do we mean that the ssh server should bind to the loopback address, or that it should listen on all loopback interfaces, regardless of address?As for IPv6, my reading of RFC3513 is that ::1 is the only localhost address. One may be able to set up routing for other addresses so that they behave the same way ::1, but I don't think that's anything an ssh implementation should be required to know about. For IPv6, "localhost interface" = "localhost address" = "::1" seems to be consistent with the referenced RFC, so I don't think there's any ambiguity.
No; you're making the same mistake of confusing an interface with an address. I believe that ::1 is the only loopback address; that is, it is the only address that means "the same machine".
A loopback _interface_ is one for which traffic sent on that interface is only received on that interface. Several operating systems allow the creation of multiple of these, and you can assign them whatever address you want and they still behave the same way. In some cases you can play games like setting up a loopback interface with a routable address, which is then reachable via TCP from outside the machine, even though it is not the address of any of the machine's physical interfaces.
This _does_ happen, and it has nothing to do with what network protocol you're running. We had to work around this in AFS, to avoid advertising addresses of loopback devices.
I think we want to be clear that if the client says to listen on 'localhost', the server SHOULD NOT listen on non-loopback addresses just because they happen to be the configured addresses of loopback interfaces.
-- Jeffrey T. Hutzelman (N3NHS) <jhutz+%cmu.edu@localhost> Sr. Research Systems Programmer School of Computer Science - Research Computing Facility Carnegie Mellon University - Pittsburgh, PA