Add simple STP timeout handler

This patch adds STP timeout error handling with arping. It's rather
simple since it only cares about the primary interface and blindly
assumes that if no gateway is available the root server is on the
same subnet.

modules.d/40network/check

@@ -2,7 +2,7 @@
 
 . $dracutfunctions
 
-for program in ip hostname; do 
+for program in ip arping; do 
   which $program >/dev/null 2>&1
   if [ $? -ne 0 ]; then
     dwarning "Could not find program \"$program\" required by network." 

modules.d/40network/install

@@ -1,5 +1,5 @@
 #!/bin/bash
-dracut_install ip dhclient brctl
+dracut_install ip dhclient brctl arping
 inst "$moddir/ifup" "/sbin/ifup"
 inst "$moddir/netroot" "/sbin/netroot"
 inst "$moddir/dhclient-script" "/sbin/dhclient-script"

modules.d/40network/netroot

@@ -77,6 +77,29 @@ done
 [ -e /tmp/net.$netif.hostname ]    && . /tmp/net.$netif.hostname
 [ -e /tmp/resolv.conf ] && cp -f /tmp/resolv.conf /etc/resolv.conf
 
+# Load interface options
+[ -e /tmp/net.$netif.override ] && . /tmp/net.$netif.override
+[ -e /tmp/dhclient.$netif.dhcpopts ] && . /tmp/dhclient.$netif.dhcpopts
+
+# Handle STP Timeout: arping default router or if not available the
+# root server. Note: This assumes that if no router is present the
+# root server is on the same subnet.
+#
+# TODO There's some netroot variants that don't (yet) have their 
+# server-ip netroot
+[ -n "$new_routers" ] && dest=${new_routers%%,*}
+[ -n "$gw" ] && dest=$gw
+if [ -z "$dest" ] ; then
+    dummy=${netroot#*:}
+    dummy=${dummy%%:*}
+    case "$dummy" in
+       [0-9]*\.[0-9]*\.[0-9]*\.[0-9]*) dest=$dummy;;
+    esac
+fi
+if [ -n "$dest" ] && ! arping -q -f -w 60 -I $netif $dest ; then
+    die "Resolving $dest via ARP on $netif failed"
+fi
+
 # Source netroot hooks before we start the handler
 source_all netroot