From 7c28b957d470dc8c6d0431c499183561cf466080 Mon Sep 17 00:00:00 2001
From: Simon Moser <mosers@tf.uni-freiburg.de>
Date: Wed, 3 Nov 2021 19:47:28 +0100
Subject: [PATCH] Changed filter method to variable types [Close #13]

---
 proxy/main.go | 76 ++++++++++++++-------------------------------------
 1 file changed, 21 insertions(+), 55 deletions(-)

diff --git a/proxy/main.go b/proxy/main.go
index 29e03b7..b4575c6 100644
--- a/proxy/main.go
+++ b/proxy/main.go
@@ -113,8 +113,8 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 		if frame.EthernetType == layers.EthernetTypeARP {
 			arpPacket := packet.Layer(layers.LayerTypeARP).(*layers.ARP)
 			log.Debug(prefix, "ARP Type ", arpPacket.Operation)
-			filterIPb(prefix, &arpPacket.DstProtAddress, &arpPacket.SourceProtAddress, arpPacket.LayerType())
-			filterMACb(prefix, &arpPacket.DstHwAddress, &arpPacket.SourceHwAddress, arpPacket.LayerType())
+			filterIP(prefix, &arpPacket.DstProtAddress, &arpPacket.SourceProtAddress, arpPacket.LayerType())
+			filterMAC(prefix, &arpPacket.DstHwAddress, &arpPacket.SourceHwAddress, arpPacket.LayerType())
 		}
 
 		log.Debug("End packet")
@@ -150,9 +150,9 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 	}
 }
 
-// filterIP checks whether an IP target in net.IP format equals a given value. If yes, it is changed
-func filterIP(prefix string, dst *net.IP, src *net.IP, context gopacket.LayerType) {
-	var target *net.IP
+// filterIP checks whether an IP target selected from src and dst equals a given value. If yes, it is changed
+func filterIP(prefix string, dst interface{}, src interface{}, context gopacket.LayerType) {
+	var target interface{}
 	var condVal net.IP
 	var newVal net.IP
 	var which string
@@ -167,38 +167,21 @@ func filterIP(prefix string, dst *net.IP, src *net.IP, context gopacket.LayerTyp
 		condVal = OldIP
 		newVal = NewIP
 	}
-	if bytes.Equal(*target, condVal) {
-		*target = newVal
+	ip, isIp := target.(*net.IP)
+	bs, isBs := target.(*[]byte)
+	if isIp && bytes.Equal(*ip, condVal) {
+		*ip = newVal
 		log.Debugf("%s%s %s IP %s changed to %s", prefix, context, which, condVal, newVal)
 	}
-}
-
-// filterIPb checks whether an IP target in []byte format equals a given value. If yes, it is changed
-func filterIPb(prefix string, dst *[]byte, src *[]byte, context gopacket.LayerType) {
-	var target *[]byte
-	var condVal net.IP
-	var newVal net.IP
-	var which string
-	if prefix == cmd.In {
-		target = dst
-		which = "dst"
-		condVal = NewIP
-		newVal = OldIP
-	} else if prefix == cmd.Out {
-		target = src
-		which = "src"
-		condVal = OldIP
-		newVal = NewIP
-	}
-	if bytes.Equal(*target, condVal) {
-		*target = newVal
+	if isBs && bytes.Equal(*bs, condVal) {
+		*bs = newVal
 		log.Debugf("%s%s %s IP %s changed to %s", prefix, context, which, condVal, newVal)
 	}
 }
 
-// filterMAC checks whether a MAC target in net.HardwareAddr format equals a given value. If yes, it is changed
-func filterMAC(prefix string, dst *net.HardwareAddr, src *net.HardwareAddr, context gopacket.LayerType) {
-	var target *net.HardwareAddr
+// filterMAC checks whether a MAC target selected from src and dst equals a given value. If yes, it is changed
+func filterMAC(prefix string, dst interface{}, src interface{}, context gopacket.LayerType) {
+	var target interface{}
 	var condVal net.HardwareAddr
 	var newVal net.HardwareAddr
 	var which string
@@ -213,31 +196,14 @@ func filterMAC(prefix string, dst *net.HardwareAddr, src *net.HardwareAddr, cont
 		condVal = OldMac
 		newVal = NewMac
 	}
-	if bytes.Equal(*target, condVal) {
-		*target = newVal
+	mac, isMac := target.(*net.HardwareAddr)
+	bs, isBs := target.(*[]byte)
+	if isMac && bytes.Equal(*mac, condVal) {
+		*mac = newVal
 		log.Debugf("%s%s %s MAC %s changed to %s", prefix, context, which, condVal, newVal)
 	}
-}
-
-// filterMACb checks whether a MAC target in []byte format equals a given value. If yes, it is changed
-func filterMACb(prefix string, dst *[]byte, src *[]byte, context gopacket.LayerType) {
-	var target *[]byte
-	var condVal net.HardwareAddr
-	var newVal net.HardwareAddr
-	var which string
-	if prefix == cmd.In {
-		target = dst
-		which = "dst"
-		condVal = NewMac
-		newVal = OldMac
-	} else if prefix == cmd.Out {
-		target = src
-		which = "src"
-		condVal = OldMac
-		newVal = NewMac
-	}
-	if bytes.Equal(*target, condVal) {
-		*target = newVal
+	if isBs && bytes.Equal(*bs, condVal) {
+		*bs = newVal
 		log.Debugf("%s%s %s MAC %s changed to %s", prefix, context, which, condVal, newVal)
 	}
-}
+}
\ No newline at end of file