Fixed type and checksum issues [Close #7, Close #6]

proxy/main.go

@@ -3,13 +3,16 @@ package main
 import (
 	"encoding/binary"
 	"flag"
+	"fmt"
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
 	log "github.com/sirupsen/logrus"
 	"io"
 	"net"
 	"proxy/cmd"
+	"proxy/util"
 	"strconv"
+	"time"
 )
 
 var OldMac net.HardwareAddr
@@ -17,7 +20,6 @@ var NewMac net.HardwareAddr
 var OldIP net.IP
 var NewIP net.IP
 
-
 // Start the two plugs and run two concurrent forward methods
 func main() {
 	// Get command line arguments
@@ -32,8 +34,8 @@ func main() {
 	log.SetLevel(log.Level(*logLvl))
 	OldMac, _ = net.ParseMAC(*oldmac)
 	NewMac, _ = net.ParseMAC(*newmac)
-	OldIP = net.ParseIP(*oldip)
-	NewIP = net.ParseIP(*newip)
+	OldIP = net.ParseIP(*oldip).To4()
+	NewIP = net.ParseIP(*newip).To4()
 	log.SetFormatter(&log.TextFormatter{
 		DisableTimestamp: true,
 	})
@@ -49,7 +51,6 @@ func main() {
 
 // Reads from an input and writes to and output,
 // do things to the content in between.
-// For now only output the packet's information
 // Is meant to be run concurrently with "go pipeForward(...)"
 func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough bool) {
 	for {
@@ -67,6 +68,7 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 
 		// Convert frame to full stack packet
 		packet := gopacket.NewPacket(frameBytes, layers.LayerTypeEthernet, gopacket.Default)
+		isInteresting := false // Debug Help
 
 		// Handle Ethernet frame
 		frame := packet.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
@@ -88,6 +90,19 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 				log.Debug(prefix, "Outgoing IP rewritten ", ipv4Packet.SrcIP, NewMac)
 				ipv4Packet.SrcIP = NewIP
 			}
+
+			// Handle ICMP packet (based on IPv4)
+			if icmpLayer := packet.Layer(layers.LayerTypeICMPv4); icmpLayer != nil {
+				icmpPacket, _ := icmpLayer.(*layers.ICMPv4)
+				log.Infof("%s ICMP packet\nType/Code:\t%s\n", prefix, icmpPacket.TypeCode.String())
+			}
+
+			// Handle DHCP packet (based on IPv4)
+			if dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4); dhcpLayer != nil && !passthrough {
+				//dhcpPacket, _ := dhcpLayer.(*layers.DHCPv4)
+				log.Info(prefix, "DHCP packet dropped")
+				continue
+			}
 		}
 
 		// Handle ARP packet
@@ -95,7 +110,7 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 			arpPacket := packet.Layer(layers.LayerTypeARP).(*layers.ARP)
 			log.Infof(
 				"%sARP before modification\nAddrType:\t%s\nProtocol:\t%s\nOperation:\t%s\n"+
-					"SrcHwAddress:\t%s\nSrcProtAddress:\t%s\nDstHwAddress:\t%s\nDstProAddress:\t%s\n",
+					"SrcHwAddress:\t%s\nSrcProtAddress:\t%s\nDstHwAddress:\t%s\nDstProtAddress:\t%s\n",
 				prefix,
 				arpPacket.AddrType,
 				arpPacket.Protocol,
@@ -108,14 +123,14 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 
 			if !passthrough && prefix == cmd.In {
 				log.Debug(prefix, "Incoming MAC rewritten (ARP) ", net.HardwareAddr(arpPacket.DstHwAddress), OldMac)
+				if arpPacket.Operation == layers.ARPReply {
+					arpPacket.DstHwAddress = OldMac
 					arpPacket.DstProtAddress = OldIP
 					log.Infof(
 						"%sARP after modification\nDstProtAddress:\t%s\n",
 						prefix,
 						net.IP(arpPacket.DstProtAddress),
 					)
-				if arpPacket.Operation == layers.ARPReply {
-					arpPacket.DstHwAddress = OldMac
 					log.Infof(
 						"%sDstHwAddress:\t%s\n",
 						prefix,
@@ -135,22 +150,24 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough
 			}
 		}
 
-		// Handle DHCP packet
-		if dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4); dhcpLayer != nil {
-			//dhcpPacket, _ := dhcpLayer.(*layers.DHCPv4)
-			log.Info(prefix, "DHCP packet dropped")
-			continue
-		}
-
+		// Serialize packet back to binary
 		buf := gopacket.NewSerializeBuffer()
-		if err := gopacket.SerializePacket(buf, gopacket.SerializeOptions{}, packet); err != nil {
-			log.Error(prefix, "Error serializing packet to send")
+		opts := gopacket.SerializeOptions{ComputeChecksums: true, FixLengths: true}
+		if err := gopacket.SerializePacket(buf, opts, packet); err != nil {
+			log.Errorf("%s Error serializing packet to send\n%s\nSrc:\t%s\nDst:\t%s\n", prefix, err, frame.SrcMAC, frame.DstMAC)
 			continue
 		}
 		newFrameBytes := buf.Bytes()
 		newFrameLength := make([]byte, 2)
 		binary.BigEndian.PutUint16(newFrameLength, uint16(len(newFrameBytes)))
 
+		// Write interesting things to debug file
+		if isInteresting && !passthrough {
+			util.WriteBinary(fmt.Sprintf("/tmp/arp_%di.dat", time.Now().Unix()), frameBytes)
+			util.WriteBinary(fmt.Sprintf("/tmp/arp_%do.dat", time.Now().Unix()), newFrameBytes)
+			//util.WritePcap("xyz.pcap", packet.Data(), packet.Metadata().CaptureInfo)
+		}
+
 		// Forward original frame to other plug
 		writer.Write(newFrameLength)
 		writer.Write(newFrameBytes)

proxy/util/util.go

@@ -0,0 +1,32 @@
+package util
+
+import (
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	"github.com/google/gopacket/pcapgo"
+	log "github.com/sirupsen/logrus"
+	"io/ioutil"
+	"os"
+)
+
+func WritePcap(file string, data []byte, ci gopacket.CaptureInfo) {
+	f, err := os.Create(file)
+	if err != nil {
+		log.Errorf("Error writing pcap file %s", file)
+	}
+	defer f.Close()
+
+	r, err := pcapgo.NewNgWriter(f, layers.LinkTypeEthernet)
+	if err != nil {
+		log.Errorf("Error writing pcap file %s", file)
+	}
+	defer r.Flush()
+
+	err = r.WritePacket(ci, data)
+}
+
+func WriteBinary(file string, data []byte) {
+	if err := ioutil.WriteFile(file, data, 0644); err != nil {
+		log.Errorf("Error writing binary file %s", file)
+	}
+}