diff --git a/src/traffic_account_donation b/src/traffic_account_donation
index c1eff94..97fd8bf 100755
--- a/src/traffic_account_donation
+++ b/src/traffic_account_donation
@@ -1,8 +1,6 @@
 #!/bin/sh
 
-# config
-TMaxFile=/etc/traffic_limit
-BytesPerCent=5368709 # 1 GiB for 2 EUR
+source $(dirname $0)/traffic_common.sh	
 
 # annoy user
 echo "How many CENT have you donated to the collecting box?"
@@ -15,13 +13,11 @@ if [ "$Donation" -lt 0 ] 2>/dev/null || [ $? -eq 2 ]; then
 fi
 
 # calc and store new value
-BytesDonated=$(( $Donation *  $BytesPerCent ))
-TMax=$(cat $TMaxFile || echo 0)
-TMax=$((TMax + $BytesDonated))
+BytesDonated=$(( $Donation * $BytesPerCent ))
+TMax=$(($TMax + $BytesDonated))
 echo $TMax > $TMaxFile
 
-# TODO: log donation
-# TODO: log remote, once connection is up
+# TODO: log donation to some remote place
 
 # cheer user up
 echo "You have donated $((BytesDonated / 1024 / 1024)) MB." \
diff --git a/src/traffic_common.sh b/src/traffic_common.sh
new file mode 100644
index 0000000..3f52c2f
--- /dev/null
+++ b/src/traffic_common.sh
@@ -0,0 +1,16 @@
+# config
+IF=eth0.1
+TMaxFile=/etc/traffic_limit
+TPerFile=/etc/traffic_consumed
+TEphFile=/tmp/traffic_to_be_accounted
+TObsFile=/tmp/traffic_observed_since_ifup
+BytesPerCent=5368709 # 1 GiB for 2 EUR
+
+# TODO: MaxPerTimeGap=3600
+MaxPerTrafficDiff=$((100 * 1024 * 1024))
+
+# gather different traffic counters
+TMax=$(cat $TMaxFile 2>/dev/null || echo 0)
+TPer=$(cat $TPerFile 2>/dev/null || echo 0)
+TEph=$(cat $TEphFile 2>/dev/null || echo 0)
+TObs=$(cat $TObsFile 2>/dev/null || echo 0)
diff --git a/src/traffic_track b/src/traffic_track
index 37e4e7b..4a851b7 100755
--- a/src/traffic_track
+++ b/src/traffic_track
@@ -1,20 +1,8 @@
 #!/bin/sh
 
-# config
-IF=eth0.1
-TMaxFile=/etc/traffic_limit
-TPerFile=/etc/traffic_consumed
-TEphFile=/tmp/traffic_to_be_accounted
-TObsFile=/tmp/traffic_observed_since_ifup
+source $(dirname $0)/traffic_common.sh	
 
-# TODO: MaxPerTimeGap=3600
-MaxPerTrafficDiff=$((100 * 1024 * 1024))
-
-# gather different traffic counters
-TMax=$(cat $TMaxFile 2>/dev/null || echo 0)
-TPer=$(cat $TPerFile 2>/dev/null || echo 0)
-TEph=$(cat $TEphFile 2>/dev/null || echo 0)
-TObs=$(cat $TObsFile 2>/dev/null || echo 0)
+# update traffic counters
 TCur=$((
 	$(ip -s link show $IF \
 	| awk '{ if (FNR == 4) print $1 " + "; if (FNR == 6) print $1 }' \
@@ -25,9 +13,6 @@ if [ "$TCur" -lt 0 ] 2>/dev/null || [ $? -eq 2 ]; then
 	# TODO: log error
 	exit -1
 fi
-	
-
-# update traffic counters
 UpdatePer=false
 if [ $TCur -lt $TObs ]; then
 	# interface counter has been reset
@@ -38,8 +23,8 @@ else
 fi
 TObs=$TCur
 TPer=$(($TPer + $TEph))
-# TODO: also lock _once_ if TPer exceeds TMax
 if [ $TEph -gt $MaxPerTrafficDiff ]; then
+        # TODO: log _once_ if TPer exceeds TMax
 	TEph=0
 	echo $TPer > $TPerFile
 fi