[init/kexec/] More advanced network setup via KCL, could skip DHCP

If enough information if provided via KCL, we can skip the initial DHCP
request in stage 3.1. Currently we require IP address, subnet mask and
DNS server to skip DHCP. If we extend the boot server to supply a
fallback/default DNS server, we could even do without DNS which would
work in almost all cases.

kexec-reboot has been extended to make use of this feature, but can be
extended even more to provide up to date values from the current system
configuration. Currently, some of the values it provides to the new
kernel will be cached values from stage 3.1.
kexec-reboot also honors the ipxe menu id from the KCL if given, to
properly download the matching menu entry, which will take updates to
the entry into account (e.g. changed URLs to kernel/init).

1 files changed, 22 insertions, 7 deletions

diff --git a/core/rootfs/rootfs-stage31/data/inc/udhcpc-trigger b/core/rootfs/rootfs-stage31/data/inc/udhcpc-trigger
index 795dd8a0..cc7454e7 100755
--- a/core/rootfs/rootfs-stage31/data/inc/udhcpc-trigger
+++ b/core/rootfs/rootfs-stage31/data/inc/udhcpc-trigger
@@ -1,13 +1,27 @@
 #!/bin/ash
 
-exec >> /run/stdout
 exec 2>> /run/stderr
 set -x
 
 if [ "x$1" != "xbound" -a "x$1" != "xrenew" ] || [ "x$interface" != "xbr0" ] || [ -z "$ip" ]; then
+	echo "Ignoring DHCP hook '$1' for interface '$interface' -> '$ip'"
 	exit 0
 fi
 
+if [ "$ip" != "${ip#*/}" ]; then # CIDR
+	cidr="$ip"
+	ip="${ip%/*}"
+elif [ -n "$mask" ]; then
+	cidr="$ip/$mask"
+else
+	if [ -z "$subnet" ]; then
+		echo "$1 event with missing subnet mask"
+		exit 1
+	fi
+	# Non-CIDR + mask
+	cidr="$ip/$( ipcalc -s -p "$ip" "$subnet" | sed 's/.*=//' )"
+fi
+
 # If we already got an IP from KCL, see if it differs, and remove first if so
 # We just try to prevent everything from breaking if the DHCP server doesn't
 # objey the renew request by the client and hands out a new address
@@ -21,14 +35,14 @@ if [ -s "/run/firstip" ]; then
 		ip route del default 2>/dev/null
 		rm -f -- "/run/firstgw"
 		ip addr del "${OLD}" dev "${interface}" 2>/dev/null
-		ip addr add "${ip}/$(ipcalc -s -p "${ip}" "${subnet}" | sed s/.*=//)" dev "${interface}"
+		ip addr add "${cidr}" dev "${interface}"
 	fi
 else
 	#...no address configured yet, just add...
 	echo "..adding ${ip}.."
-	ip addr add "${ip}/$(ipcalc -s -p "${ip}" "${subnet}" | sed s/.*=//)" dev "${interface}"
+	ip addr add "${cidr}" dev "${interface}"
 fi
-echo -n "$ip" > "/run/firstip"
+printf "%s" "$ip" > "/run/firstip"
 
 # Same procedure for default gateway
 if [ -n "${router}" ]; then
@@ -42,7 +56,7 @@ if [ -n "${router}" ]; then
 	else
 		ip route add default via "$router"
 	fi
-	echo -n "$router" > "/run/firstgw"
+	printf "%s" "$router" > "/run/firstgw"
 fi
 
 rm -f -- "/etc/resolv.conf"
@@ -56,7 +70,7 @@ fi
 for serv in $dns; do
 	echo "nameserver $serv" >> "/etc/resolv.conf"
 done
-if [ -z "$domain" ]; then
+if [ -z "$domain" ] && [ -n "$dns" ]; then
 	# try to get domain via reverse lookup if empty
 	echo "..trying to get domain via DNS, as DHCP didn't supply one.."
 	fqdn=$(timeout -t 3 nslookup "$ip" | grep -E "^Address +[0-9]+: +$ip " | head -n 1 | awk '{print $4}')
@@ -92,7 +106,7 @@ done
 if [ -z "$hostname" ]; then
 	# as with domain, if there's no hostname, try to get via DNS
 	echo "..trying to get hostname via DNS, as DHCP didn't supply one.."
-	[ -z "$fqdn" ] && fqdn=$(timeout -t 3 nslookup "$ip" | grep -E "^Address +[0-9]+: +$ip " | head -n 1 | awk '{print $4}')
+	[ -z "$fqdn" ] && [ -n "$dns" ] && fqdn=$(timeout -t 3 nslookup "$ip" | grep -E "^Address +[0-9]+: +$ip " | head -n 1 | awk '{print $4}')
 	hostname="${fqdn%%.*}"
 elif [ -n "$domain" ]; then
 	fqdn="${hostname}.${domain}"
@@ -111,3 +125,4 @@ if [ -n "$hostname" ]; then
 	echo "SLX_HOSTNAME='$hostname'" >> "/run/config"
 fi
 
+exit 0