# Set the hostname from DHCP data if required

# A hostname can either be a short hostname or a FQDN.
# hostname_fqdn=true
# hostname_fqdn=false
# hostname_fqdn=server

# A value of server means just what the server says, don't manipulate it.
# This could lead to an inconsistent hostname on a DHCPv4 and DHCPv6 network
# where the DHCPv4 hostname is short and the DHCPv6 has an FQDN.
# DHCPv6 has no hostname option.
# RFC4702 section 3.1 says FQDN should be prefered over hostname.
#
# As such, the default is hostname_fqdn=true so that a consistent hostname
# is always assigned.
: ${hostname_fqdn:=true}

# If we used to set the hostname, but relinquish control of it, we should
# reset to the default value.
: ${hostname_default=}

# Some systems don't have hostname(1)
_hostname()
{
	if [ -z "${1+x}" ]; then
		if [ -r /proc/sys/kernel/hostname ]; then
			read name </proc/sys/kernel/hostname && echo "$name"
		elif command -v hostname >/dev/null 2>/dev/null; then
			hostname
		elif sysctl kern.hostname >/dev/null 2>&1; then
			sysctl -n kern.hostname
		elif sysctl kernel.hostname >/dev/null 2>&1; then
			sysctl -n kernel.hostname
		else
			return 1
		fi
		return $?
	fi

	if [ -w /proc/sys/kernel/hostname ]; then
		echo "$1" >/proc/sys/kernel/hostname
	elif [ -n "$1" ] && command -v hostname >/dev/null 2>&1; then
		hostname "$1"
	elif sysctl kern.hostname >/dev/null 2>&1; then
		sysctl -w "kern.hostname=$1" >/dev/null
	elif sysctl kernel.hostname >/dev/null 2>&1; then
		sysctl -w "kernel.hostname=$1" >/dev/null
	else
		# May fail to set a blank hostname
		hostname "$1"
	fi
}

is_default_hostname()
{
	case "$1" in
	""|"$hostname_default"|localhost|localhost.localdomain)
		return 0;;
	esac
	return 1
}

need_hostname()
{
	# Always load the hostname variable for future use
	hostname="$(_hostname)"
	is_default_hostname "$hostname" && return 0

	case "$force_hostname" in
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|1) return 0;;
	esac

	if [ -n "$old_fqdn" ]; then
		if ${hfqdn} || ! ${hshort}; then
			[ "$hostname" = "$old_fqdn" ]
		else
			[ "$hostname" = "${old_fqdn%%.*}" ]
		fi
	elif [ -n "$old_host_name" ]; then
		if ${hfqdn}; then
			if [ -n "$old_domain_name" ] &&
			   [ "$old_host_name" = "${old_host_name#*.}" ]
			then
				[ "$hostname" = \
				    "$old_host_name.$old_domain_name" ]
			else
				[ "$hostname" = "$old_host_name" ]
			fi
		elif ${hshort}; then
			[ "$hostname" = "${old_host_name%%.*}" ]
		else
			[ "$hostname" = "$old_host_name" ]
		fi
	else
		# No old hostname
		false
	fi
}

try_hostname()
{
	[ "$hostname" = "$1" ] && return 0
	if valid_domainname "$1"; then
		syslog info "Setting hostname: $1"
		_hostname "$1"
	else
		syslog err "Invalid hostname: $1"
	fi
}

set_hostname()
{
	hfqdn=false
	hshort=false
	case "$hostname_fqdn" in
	[Yy][Ee][Ss]|[Tt][Rr][Uu][Ee]|1)	hfqdn=true;;
	""|[Ss][Ee][Rr][Vv][Ee][Rr])		;;
	*)					hshort=true;;
	esac

	need_hostname || return

	if [ -n "$new_fqdn" ]; then
		if ${hfqdn} || ! ${hshort}; then
			try_hostname "$new_fqdn"
		else
			try_hostname "${new_fqdn%%.*}"
		fi
	elif [ -n "$new_host_name" ]; then
		if ${hfqdn}; then
			if [ -n "$new_domain_name" ] &&
			   [ "$new_host_name" = "${new_host_name#*.}" ]
			then
				try_hostname "$new_host_name.$new_domain_name"
			else
				try_hostname "$new_host_name"
			fi
		elif ${hshort}; then
			try_hostname "${new_host_name%%.*}"
		else
			try_hostname "$new_host_name"
		fi
	elif ! is_default_hostname "$hostname"; then
		try_hostname "$hostname_default"
	fi
}

# For ease of use, map DHCP6 names onto our DHCP4 names
case "$reason" in
BOUND6|RENEW6|REBIND6|REBOOT6|INFORM6)
	new_fqdn="$new_dhcp6_fqdn"
	old_fqdn="$old_dhcp6_fqdn"
	;;
esac

if $if_configured && $if_up && [ "$reason" != ROUTERADVERT ]; then
	set_hostname
fi