Display ARP nad DHCP packets

README.md

@@ -66,8 +66,8 @@ Keep in mind:
 
 ### Go:
 
-* Internet layer packet modification: https://github.com/google/gopacket / https://pkg.go.dev/github.com/google/gopacket
+* gopacket (~libpcap): https://github.com/google/gopacket / https://pkg.go.dev/github.com/google/gopacket
-* Link layer frame modification: https://github.com/mdlayher/ethernet / https://pkg.go.dev/github.com/mdlayher/ethernet (not recently updated, alternative?)
+* (Link layer frame modification: https://github.com/mdlayher/ethernet / https://pkg.go.dev/github.com/mdlayher/ethernet)
 
 ### Rust:
 

proxy/main.go

@@ -7,7 +7,6 @@ import (
 	"github.com/google/gopacket/layers"
 	_ "github.com/google/gopacket/layers"
 	"io"
-	"os"
 	"proxy/cmd"
 )
 
@@ -25,7 +24,7 @@ func main() {
 
 // Reads from an input and writes to and output,
 // do things to the content in between.
-// For now only output the frames information
+// 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) {
 	for {
@@ -36,7 +35,7 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string) {
 			break
 		}
 		frameLengthInt := int(binary.BigEndian.Uint16(frameLength))
-		os.Stdout.WriteString(fmt.Sprintf("%s Frame length: %d\n", prefix, frameLengthInt))
+		fmt.Printf("%s Frame length: %d\n", prefix, frameLengthInt)
 
 		// Read actual frame
 		frameBytes := make([]byte, frameLengthInt)
@@ -45,15 +44,23 @@ func pipeForward(reader io.Reader, writer io.Writer, prefix string) {
 			break
 		}
 
+		// Convert frame to full stack packet
 		packet := gopacket.NewPacket(frameBytes, layers.LayerTypeEthernet, gopacket.Default)
-		frame := packet.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
 
+		// Handle Ethernet frame
+		frame := packet.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
 		fmt.Printf("src: %s\ndst: %s\ntyp: %s\n", frame.SrcMAC, frame.DstMAC, frame.EthernetType)
 
-		switch frame.EthernetType {
+		// Handle ARP packet
-		case layers.EthernetTypeARP:
+		if frame.EthernetType == layers.EthernetTypeARP {
 			arpPacket := packet.Layer(layers.LayerTypeARP).(*layers.ARP)
-			fmt.Printf("%#v", arpPacket)
+			fmt.Printf("%sARP Packet:\n%#v\n", prefix, arpPacket)
+		}
+
+		// Handle DHCP packet
+		if dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4); dhcpLayer != nil {
+			dhcpPacket, _ := dhcpLayer.(*layers.DHCPv4)
+			fmt.Printf("%sDHCP Packet:\n%#v\n", prefix, dhcpPacket)
 		}
 
 		// Forward original frame to other plug