Re: IPv6 socket behaviour different to IPv4?

[Darren Reed <darrenr%netbsd.org@localhost>]

On 4/06/2014 6:23 PM, Roy Marples wrote:
> On 04/06/2014 0:31, Darren Reed wrote:
> > On 4/06/2014 4:05 AM, Roy Marples wrote:
> > > On 03/06/2014 16:40, Darren Reed wrote:
> > > > But when I configure "fd00::1" or "1::1" as an IPv6 address, I would
> > > > expect that the system should be able to recognise that there is no
> > > > desire on my part to change the address should a conflict arise but
> > > > I can't see any way for the kernel to divine that when it is just 
> > > > given
> > > > an IP address.
> > >
> > > Why do you have this desire?
> > > If any address is on-link, DAD needs to be performed.
> >
> > Put yourself in an IPv6 only world...
>
> Not relevant to the discussion, the same logic also applies to IPv4 
> although this requires a good userland daemon like say dhcpcd.

In an IPv4 world, if I put "10.1.1.1 netbsd" in my hosts file and
manually assign 10.1.1.1 to any network interface, then I will
always be able to connect to 10.1.1.1 and thus "netbsd".

> DAD is performed using ARP and when the link goes down the address is 
> removed from the interface.

Except that DAD only marks an IP address as being unusable when
a duplicate is detected which is significantly different to an address
being unusable until an effort has been made to ensure it is unique.


> > In your /etc/hosts file, you have an entry in it for an IPv6 address
> > to be assigned to your hostname and no other line with your hostname.
> >
> > As soon as you disconnect from the network, you can no longer do
> > "ssh hostname".
>
> And this is a problem how exactly? `ssh localhost` still works.
> Sounds more like a local name resolution issue than an address 
> availability one.

Rinse and repeat by replacing "hostname" with a static IP address that
you have assigned to a network interface.

Darren