From: Peter Hessler <phessler@theapt.org>
Subject: Re: installer: default to IPv6 autoconf if IPv4 is not configured
To: Andrew Hewus Fresh <andrew@afresh1.com>
Cc: Klemens Nanni <kn@openbsd.org>, OpenBSD tech <tech@openbsd.org>
Date: Sun, 16 Nov 2025 08:52:58 +0100

On 2025 Nov 15 (Sat) at 20:01:03 -0800 (-0800), Andrew Hewus Fresh wrote:
:On Fri, Nov 14, 2025 at 04:14:06PM +0000, Klemens Nanni wrote:
:> When you opt out of IPv4, the only sane default for IPv6 becomes 'autoconf'
:> as we cannot magically guess an address and 'none' means no network at all,
:> which is equivalent to not configuring the interface in the first place:
:> 
:> 	 Available network interfaces are: vio0 vlan0.
:> 	 Network interface to configure? (name, lladdr, '?', or 'done') [vio0] 
:> 	 IPv4 address for vio0? (or 'autoconf' or 'none') [autoconf] none
:> 	-IPv6 address for vio0? (or 'autoconf' or 'none') [none] 
:> 	+IPv6 address for vio0? (or 'autoconf' or 'none') [autoconf] 
:> 
:> The diff is trivial and the result is typing convenience for installs
:> (upgrades don't run these questions) in IPv6-mostly or -only networks.
:> 
:> Feedback? OK?
:
:I didn't have time to test this, but it looks OK to me and seems like a
:nice idea.  I wonder if we will ever get to the point where it makes
:sense to always default this to on.
:

The vast majority of networks I connect to (home, work, conference) have
IPv6; so I would be delighted by having IPv6 autoconf as the default.

-peter


: 
:> Index: install.sub
:> ===================================================================
:> RCS file: /cvs/src/distrib/miniroot/install.sub,v
:> diff -u -p -U9 -r1.1280 install.sub
:> --- install.sub	1 Nov 2025 12:54:17 -0000	1.1280
:> +++ install.sub	14 Nov 2025 15:34:26 -0000
:> @@ -1101,36 +1101,38 @@ v4_config() {
:>  	while :; do
:>  		ask_until "IPv4 address for $_if? (or 'autoconf' or 'none')" \
:>  			  "${_addr:-autoconf}"
:>  		case $resp in
:>  		none)	return
:>  			;;
:>  		a|autoconf|dhcp)
:>  			dhcp_request $_if
:>  			echo "inet autoconf" >>$_hn
:> +			USES_IPV4=true
:>  			return
:>  			;;
:>  		esac
:>  
:>  		_newaddr=$resp
:>  
:>  		# Ask for the netmask if the user did not use CIDR notation.
:>  		if [[ $_newaddr == */* ]]; then
:>  			ifconfig $_if $_newaddr up
:>  		else
:>  			ask_until "Netmask for $_if?" "${_mask:-255.255.255.0}"
:>  			ifconfig $_if $_newaddr netmask $resp
:>  		fi
:>  
:>  		set -- $(v4_info $_if)
:>  		if [[ -n $2 ]]; then
:>  			echo "inet $2 $3" >>$_hn
:>  			add_hostent "$2" "$_name"
:> +			USES_IPV4=true
:>  			return
:>  		fi
:>  
:>  		$AI && exit 1
:>  	done
:>  }
:>  
:>  # Obtain and output the inet6 information related to interface $1.
:>  # <flags>\n<addr> <prefixlen> <rest of inet6 line>[\n<more inet6 lines>]
:> @@ -1215,19 +1217,19 @@ v6_defroute() {
:>  # unless he chooses 'autoconf'.
:>  v6_config() {
:>  	local _if=$1 _name=$2 _hn=$3 _addr _newaddr _prefixlen
:>  
:>  	ifconfig lo0 inet6 >/dev/null 2>&1 || return
:>  
:>  	# Preset the default answers by preserving possibly existing
:>  	# configuration from previous runs.
:>  	set -- $(v6_info $_if)
:> -	if [[ $1 == *AUTOCONF6* ]]; then
:> +	if [[ $1 == *AUTOCONF6* ]] || ! $USES_IPV4; then
:>  		_addr=autoconf
:>  	elif [[ -n $2 ]]; then
:>  		_addr=$2
:>  		_prefixlen=$3
:>  	fi
:>  
:>  	# Nuke existing inet6 configuration.
:>  	ifconfig $_if -inet6
:>  
:> @@ -3657,18 +3659,19 @@ HTTP_LIST=/tmp/i/httplist
:>  HTTP_SEC=/tmp/i/httpsec
:>  INSTALL_METHOD=
:>  NIFS=0
:>  export PS1="$MODE# "
:>  PUB_KEY=/etc/signify/openbsd-${VERSION}-base.pub
:>  ROOTDEV=
:>  ROOTDISK=
:>  SETDIR="$VNAME/$ARCH"
:>  UPGRADE_BSDRD=false
:> +USES_IPV4=false
:>  V4_AUTOCONF=false
:>  V6_AUTOCONF=false
:>  WLANLIST=/tmp/i/wlanlist
:>  
:>  # Are we in a real release, or a snapshot?  If this is a snapshot
:>  # install media, default us to a snapshot directory.
:>  HTTP_SETDIR=$SETDIR
:>  set -- $(scan_dmesg "/^OpenBSD $VNAME\([^ ]*\).*$/s//\1/p")
:>  [[ $1 == -!(stable) ]] && HTTP_SETDIR=snapshots/$ARCH
:> 
:
:-- 
:andrew
:
:Whatever happened to the days when hacking started at the cerebral cortex 
:and not the keyboard?
:                      -- Sid from UserFriendly.org
:

-- 
An exotic journey in downtown Newark is in your future.