New function ipv4_prefix_to_netmask()

Allows calculation of netmask from prefix.

Signed-off-by: Martin Schwenke <martin@meltin.net>

1 files changed, 25 insertions, 0 deletions

diff --git a/autocluster b/autocluster
index 62cbdfd..3e9d88e 100755
--- a/autocluster
+++ b/autocluster
@@ -951,6 +951,31 @@ setup_base()
     run_hooks setup_base_hooks
 }
 
+ipv4_prefix_to_netmask ()
+{
+    local prefix="$1"
+
+    local div=$(($prefix / 8))
+    local mod=$(($prefix % 8))
+
+    local octet
+    for octet in 1 2 3 4 ; do
+	if [ $octet -le $div ] ; then
+	    echo -n "255"
+	elif [ $mod -ne 0 -a $octet -eq $(($div + 1)) ] ; then
+	    local shift=$((8 - $mod))
+	    echo -n $(( (255 >> $shift << $shift) ))
+	else
+	    echo -n 0
+	fi
+	if [ $octet -lt 4 ] ; then
+	    echo -n '.'
+	fi
+    done
+
+    echo
+}
+
 # setup various networking components
 setup_network()
 {