Cleanup and improve documentation for ip= parameter

initramfs-init.in

@@ -146,14 +146,6 @@ ip_choose_if() {
 	[ -e "$x" ] && echo ${x##*/} && return
 }
 
-# ip_set <device> <ip> <netmask> <gateway-ip>
-ip_set() {
-	ifconfig "$1" "$2" netmask "$3" || return $?
-	if [ -n "$4" ]; then
-		ip route add 0.0.0.0/0 via "$4" dev "$1" || return $?
-	fi
-}
-
 # if "ip=dhcp" is specified on the command line, we obtain an IP address
 # using udhcpc. we do this now and not by enabling kernel-mode DHCP because
 # kernel-model DHCP appears to require that network drivers be built into
@@ -162,19 +154,24 @@ ip_set() {
 #
 # You need af_packet.ko available as well modules for your Ethernet card.
 #
+# See https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt
+# for documentation on the format.
+#
 # Valid syntaxes:
-#   ip=client-ip:server-ip:gw-ip:netmask:hostname:device:autoconf
+#   ip=client-ip:server-ip:gw-ip:netmask:hostname:device:autoconf:
+#     :dns0-ip:dns1-ip:ntp0-ip
 #   ip=dhcp
-#   "server-ip" and "hostname" are not supported here.
+#   "server-ip", "hostname" and "ntp0-ip" are not supported here.
 # Default (when configure_ip is called without setting ip=):
 #   ip=dhcp
 #
 configure_ip() {
 	[ -n "$MAC_ADDRESS" ] && return
-	local ops=${KOPT_ip:-dhcp}
+
 	local IFS=':'
-	set -- $ops
+	set -- ${KOPT_ip:-dhcp}
 	unset IFS
+
 	local client_ip="$1"
 	local gw_ip="$3"
 	local netmask="$4"
@@ -182,16 +179,19 @@ configure_ip() {
 	local autoconf="$7"
 	local dns1="$8"
 	local dns2="$9"
+
 	case "$client_ip" in
-		off|none|'') return;;
+		off|none) return;;
 		dhcp) autoconf="dhcp";;
 	esac
 
 	[ -n "$device" ] || device=$(ip_choose_if)
+
 	if [ -z "$device" ]; then
 		echo "ERROR: IP requested but no network device was found"
 		return 1
 	fi
+
 	if [ "$autoconf" = "dhcp" ]; then
 		# automatic configuration
 		if [ ! -e /usr/share/udhcpc/default.script ]; then
@@ -199,18 +199,24 @@ configure_ip() {
 			return 1
 		fi
 		ebegin "Obtaining IP via DHCP ($device)..."
-		ifconfig $device 0.0.0.0
-		udhcpc -i $device -f -q
+		ifconfig "$device" 0.0.0.0
+		udhcpc -i "$device" -f -q
 		eend $?
 	else
 		# manual configuration
 		[ -n "$client_ip" -a -n "$netmask" ] || return
 		ebegin "Setting IP ($device)..."
-		ip_set "$device" "$client_ip" "$netmask" "$gw_ip"
+		if ifconfig "$device" "$client_ip" netmask "$netmask"; then
+			[ -z "$gw_ip" ] || ip route add 0.0.0.0/0 via "$gw_ip" dev "$device"
+		fi
 		eend $?
-		[ -n "$dns1" ] && echo "nameserver $dns1" >> /etc/resolv.conf
-		[ -n "$dns2" ] && echo "nameserver $dns2" >> /etc/resolv.conf
 	fi
+
+	# Never executes if variables are empty
+	for i in $dns1 $dns2; do
+		echo "nameserver $i" >> /etc/resolv.conf
+	done
+
 	MAC_ADDRESS=$(cat /sys/class/net/$device/address)
 }
 

mkinitfs-bootparam.7.in

@@ -50,11 +50,12 @@ Print debug information during boot.
 \fBinit_args=\fIARGUMENTS\fR
 Additional command like arguments for \fI/sbin/init\fR.
 .TP
-\fBip=\fICLIENT-IP\fR::\fIGATEWAY-IP\fR:\fINETMASK\fR::\fIINTERFACE\fR
-Specify the network configuration as a colon-separated list of variable length.
-The 3rd and the 5th list item is ignored. The format is compatible with the
-SYSAPPEND option of syslinux. Use \fBip=dhcp\fR for automatic configuration via
-DHCP.
+\fBip=\fICLIENT-IP\fR:\fISERVER-IP\fR:\fIGATEWAY-IP\fR:\fINETMASK\fR:\fIHOSTNAME\fR:\fIDEVICE\fR:\fIAUTOCONF\fR:\fIDNS-IP\fR:\fIDNS-IP\fR:\fINTP-IP\fR
+Specify the network configuration. The format is equivalent to the linux kernel
+option with the same name. Per default, the \fISERVER-IP\fR, \fIHOSTNAME\fR and
+\fINTP-IP\fR parameters are ignored by the initramfs. Consult the kernel
+documentation on \fInfsroot\fR for further information regarding the fields of
+this parameter.
 .TP
 \fBmodules=\fIMODULE\fR{,\fIMODULE\fR}
 Comma-sparated list of kernel modules to load explicitly.