Re: kern/51531: Recent networking regression affecting installs

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Wed, Oct 05, 2016 at 02:45:01PM +0000, Andreas Gustafsson wrote:
> The following reply was made to PR kern/51531; it has been noted by GNATS.
> 
> From: Andreas Gustafsson <gson%gson.org@localhost>
> To: gnats-bugs%NetBSD.org@localhost
> Cc: kern-bug-people%netbsd.org@localhost,
>     gnats-admin%netbsd.org@localhost,
>     netbsd-bugs%netbsd.org@localhost,
>     gson%gson.org@localhost (Andreas Gustafsson)
> Subject: Re: kern/51531: Recent networking regression affecting installs
> Date: Wed, 5 Oct 2016 17:42:18 +0300
> 
>  Roy Marples wrote:
>  >  I think ifconfig -w 15 -W 5 should be added to sysinst before the ping
>  >  test to wait for DaD to clear.
>  
>  I think sysinst, and other existing code that configures IP addresses,
>  is not incorrect as written, and should not be required to do this.

I disagree, quite a bit. There are three options for such a program:
(1) It is dumb and just expects a newly configured interface to work
after some time. Nothing new here.
(2) It tries to be smart and checks immediately after configuration if
ping works. This has been wrong for a variety of network conditions
already, since link configuration itself can already take time in the
second range. WiFi can be even worse with slow authorisation. This
really is an application bug and not related to this issue at all.
(3) It tries to be even smarter and checks for link state changes before
ping. This still doesn't work properly for WiFi or 802.1x ports. DaD
timeouts are no different here.

In short, *any* assumption that a freshly configured network interface
is going to be ready RSN are wrong. There are some architectural issues
in that we currently have no way to report "this interface should be
usable now", which is shared with all the BSDs. But it is essentially
unrelated to the recent DaD changes.

Joerg