install/58219: sysinst should check if IPv6 is available and set ip6addrctl_policy=ipv4_prefer if no

[nia%pkgsrc.org@localhost]

>Number:         58219
>Category:       install
>Synopsis:       sysinst should check if IPv6 is available and set ip6addrctl_policy=ipv4_prefer if no
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 01 08:10:00 +0000 2024
>Originator:     nia
>Release:        any netbsd release on QEMU
>Organization:
The AttemptingToConnectBSD Foundation
>Environment:
>Description:
Most virtual machines are buggy and report a fake ipv6 route.

NetBSD's tools like ftp will hang for far too long attempting to reach an ipv6 address.
>How-To-Repeat:
install netbsd in qemu, use ftp
>Fix:
set

ip6addrctl=YES
ip6addrctl_policy=ipv4_prefer

in rc.conf when ipv6 is unavailable.