ip-token: unable to remove a token & multi-token handling & concurrent use w/ EUI64/privacy

ip-token: unable to remove a token & multi-token handling & concurrent use w/ EUI64/privacy

[Robin H. Johnson]

Hi,

Playing around with IPv6 tokens, I ran into a problem:
Once you have a token set on an interface, it's impossible to remove it!

# ip token set :: dev eth0
RTNETLINK answers: Invalid argument

This is a side-effect of rejecting ipv6_addr_any in inet6_set_iftoken.

While this gets fixed, I have two related feature requests for this:
- Please make it possible to configure multiple tokens on an interface:
  Use case: Deploying local services on well-known addresses inside a
  network without explicit prefix configuration.
- Adding a token causes other address generation methods to be disabled,
  this is problematic if you wish to prefer privacy addresses for
  outbound connections.

Design suggestion:
Convert from using a single token to using a list of tokens, with an
explicit default IPv6-any-addr (::) in the list, to represent that
other address generation should ALSO take place (EUI64/privacy).
Deletion of the any-addr from the list should disable EUI64/privacy
addresses.

-- 
Robin Hugh Johnson
Gentoo Linux: Developer, Infrastructure Lead, Foundation Trustee
E-Mail     : robbat2@gentoo.org
GnuPG FP   : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85

Re: ip-token: unable to remove a token & multi-token handling & concurrent use w/ EUI64/privacy

[Daniel Borkmann]

Hi Robin,

On 03/19/2016 07:53 PM, Robin H. Johnson wrote:
[...]
> Playing around with IPv6 tokens, I ran into a problem:
> Once you have a token set on an interface, it's impossible to remove it!
>
> # ip token set :: dev eth0
> RTNETLINK answers: Invalid argument

I'll have a look into a fix, I think this was intentional, but I currently
fail to recall a reason why (should have put a note into the commit log). ;)
The draft is pretty terse in any case, it seems as we only invalidate other
tokenized addresses, it should be okay to just remove it.

> This is a side-effect of rejecting ipv6_addr_any in inet6_set_iftoken.
>
> While this gets fixed, I have two related feature requests for this:
> - Please make it possible to configure multiple tokens on an interface:
>    Use case: Deploying local services on well-known addresses inside a
>    network without explicit prefix configuration.
> - Adding a token causes other address generation methods to be disabled,
>    this is problematic if you wish to prefer privacy addresses for
>    outbound connections.
>
> Design suggestion:
> Convert from using a single token to using a list of tokens, with an
> explicit default IPv6-any-addr (::) in the list, to represent that
> other address generation should ALSO take place (EUI64/privacy).
> Deletion of the any-addr from the list should disable EUI64/privacy
> addresses.

Seems you already have some patches, please feel free to send them. ;)

Thanks for the feedback!
Daniel