install/49231: Recent regressions in IPv4-only sysinst network install

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         49231
>Category:       install
>Synopsis:       Recent regressions in IPv4-only sysinst network install
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Sep 21 11:00:00 +0000 2014
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date 2014.09.20.15.10.41
>Organization:
>Environment:
System: NetBSD
Architecture: amd64
Machine: x86_64
>Description:

I am trying to install NetBSD-current using sysinst, fetching the
distribution sets by HTTP over IPv4.  This worked before, but
some time during the recent one-month period when sysinst was
broken for unrelated reasons (PR 49128), the problems described
below appeared.  Perhaps they were introduced by the commits to
sysinst/net.c (and others) by roy on September 12.

I'm answering "no" to the "Perform autoconfiguration?" question and
configuring the network manually.  The HTTP server holding the
distribution sets is specified by its numeric IPv4 address rather than
by domain name; things may fail differently (and earlier) if a domain
name is used.

I do not have IPv6 connectivity at this location.

Problem 1: sysinst asks for an IPv6 DNS server even though I don't
have an IPv6 network.  Since there was no obvious way to answer
"none", I just chose the first option displayed
(google-public-dns-a.google.com).

Problem 2: sysinst never asks for an IP4 DNS server.

Problem 3: sysinst runs ping6 to check if the network is up,
even though I don't have an IPv6 network.  As one might expect,
this fails.

Problem 4: sysinst never runs ping to checks if the IPv4 network is
up.  I think this is because in config_network(), the variable
network_up is set to false due to ping6 failing, and the ping
invocation is within "if (... & network_up)".

Problem 5: Sysinst no longer asks the question "Is the network
information you entered accurate for this machine in regular operation
and do you want it installed in /etc?", and no longer installs the
network configuration on the target machine.  I think this is also
because network_up is false, which causes mnt_net_config() to return
immediately.

Despite all this, sysinst successfully downloads and untars the
distribution sets and completes the installation, and never issues
any error messages other than the one about the failed ping6.  The
problems only really become apparent when you boot the installed
system and find that the network has not been configured.

>How-To-Repeat:

Do an IPv4-only network install using sysinst.  If successful, boot
the installed system and try to use the network.

>Fix:

>Unformatted: