From 656254918425e4f0f46904eb1b27141f07f0e998 Mon Sep 17 00:00:00 2001
From: Jonathan Bauer
Date: Fri, 13 Aug 2021 15:26:59 +0200
Subject: [slx-network] rework hostname setup

try to cope for more corner cases and still do the right thing...
---
 .../slx-network/scripts/udhcpc-trigger.stage3      | 51 +++++++++++++---------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/modules.d/slx-network/scripts/udhcpc-trigger.stage3 b/modules.d/slx-network/scripts/udhcpc-trigger.stage3
index afac2027..402670d0 100755
--- a/modules.d/slx-network/scripts/udhcpc-trigger.stage3
+++ b/modules.d/slx-network/scripts/udhcpc-trigger.stage3
@@ -81,10 +81,13 @@ for srv in $dns; do
 	echo "nameserver $srv" >> "/etc/resolv.conf"
 done
 
+# always check DNS
+echo "Checking DNS record for this host..."
+[ -z "$fqdn" ] && fqdn="$(reverse_lookup "$ip")"
+[ -n "$fqdn" ] && fqdn_hostname="${fqdn%%.*}"
+
 if [ -z "$domain" ]; then
-	# try to get domain via reverse lookup if empty
-	echo "..trying to get domain via DNS, as DHCP didn't supply one.."
-	fqdn="$(reverse_lookup "$ip")"
+	echo "Getting domain via DNS, as DHCP didn't supply one.."
 	domain="${fqdn#*.}"
 fi
 
@@ -115,33 +118,41 @@ if [ -n "$ntpsrv" ]; then
 fi
 
 # Hostname
-# Ignore hostname/fqdn it if hostname was forced per KCL.
-if [ -n "$SLX_PXE_HOSTNAME" ]; then
-	echo "Hostname set via KCL, ignoring DHCP hostname: '$hostname'"
-	hostname="$SLX_PXE_HOSTNAME"
+if [ -n "$hostname" ]; then
+	if [ -n "$SLX_PXE_HOSTNAME" ] && [ "$hostname" != "$SLX_PXE_HOSTNAME" ]; then
+		echo "KCL and DHCP hostnames differ... assuming some KCL hack."
+		echo "Prefering KCL: '$SLX_PXE_HOSTNAME'."
+		hostname="$SLX_PXE_HOSTNAME"
+	fi
 else
-	if [ -z "$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 "$fqdn" ] && fqdn="$(reverse_lookup "$ip")"
-		hostname="${fqdn%%.*}"
-	elif [ -n "$domain" ]; then
-		fqdn="${hostname}.${domain%% *}" # in case domain is a list
+	echo "No hostname specified in DHCP, checking DNS record."
+	# We ignore the corner case where DHCP didn't supply a hostname but
+	# there is a hardcoded one via KCL as it seems unlikely, log it nonetheless
+	if [ -n "$SLX_PXE_HOSTNAME" ]; then
+		echo "DHCP didn't supply a hostname but one was supplied by KCL?" \
+			"This seems strange but using KCL hostname anyways."
+		hostname="$SLX_PXE_HOSTNAME"
+	else
+		# regular fallback to DNS and noname-* if needed
+		if [ -n "$fqdn_hostname" ]; then
+			echo "Using DNS record hostname: $fqdn_hostname."
+			hostname="$fqdn_hostname"
+		else
+			# no fallback hostname from DNS, use IP address
+			hostname="noname-${ip//./-}"
+		fi
+		if [ -n "$domain" ]; then
+			fqdn="${hostname}.${domain%% *}" # in case domain is a list
+		fi
 	fi
 fi
 
-if [ -z "$hostname" ]; then
-	# no fallback hostname from DNS, use IP address
-	hostname="noname-${ip//./-}"
-fi
-
 if [ -n "$hostname" ]; then
 	[ -z "$fqdn" ] && fqdn="$hostname"
 	echo "..setting hostname $hostname (fqdn: $fqdn).."
 	echo "$hostname" > "/proc/sys/kernel/hostname"
 	echo "$hostname" > "/etc/hostname"
 	echo "127.0.0.1 localhost" > "/etc/hosts"
-#	echo "127.0.1.1 $fqdn $hostname" >> "/etc/hosts"
 	echo "SLX_HOSTNAME='$hostname'" >> "$NETWORK_CONF"
 fi
 
-- 
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