make compatable with windows. improve logging

go/README.md

@@ -1,12 +1,14 @@
 `sudo apt install libpcap-dev gcc`
 
 ```bash
-wlan2eth build wlan2eth.wlan2eth
+go mod tidy
-sudo ./wlan2eth
+go build wlan2eth
 ```
 
-If build fails, try `CGO_ENABLED=1`
+Run the program like this:
 
-# Issues
+```
+./wlan2eth --dhcp-modify-src --eth [name of ethernet] --wlan [name of wireless interface]
+```
 
-- To prevent forwarding duplicates, incoming hash of in packets are cached and checked against subsequent packets. This may cause issues where duplicate packets are blocked.  
+`--dhcp-modify-src` will modify the client address in the DHCP packets.

go/wlan2eth/arp/arp_request.go

@@ -10,7 +10,7 @@ import (
 	"wlan2eth/logger"
 )
 
-func HandleARPRequest(packet gopacket.Packet, srcSocket, dstSocket int, srcName, dstName string, srcMAC, dstMAC net.HardwareAddr, wlan0MAC net.HardwareAddr, eth0 string) {
+func HandleARPRequest(packet gopacket.Packet, srcSocket, dstSocket int, srcName, dstName string, srcMAC, dstMAC net.HardwareAddr, eth0MAC, wlan0MAC net.HardwareAddr, eth0 string) {
 	log := logger.GetLogger()
 
 	arpLayer := packet.Layer(layers.LayerTypeARP).(*layers.ARP)
@@ -19,7 +19,8 @@ func HandleARPRequest(packet gopacket.Packet, srcSocket, dstSocket int, srcName,
 	// Add the client to the bridgedClients map
 	srcIP := net.IP(arpLayer.SourceProtAddress)
 	srcHwAddr := arpLayer.SourceHwAddress
-	AddBridgedClient(srcIP, srcHwAddr, wlan0MAC, eth0)
+
+	AddBridgedClient(srcIP, srcHwAddr, eth0MAC, wlan0MAC, eth0)
 
 	// Check if the ARP request is an ARP announcement
 	isARPAnnouncement := bytes.Equal(arpLayer.SourceProtAddress, arpLayer.DstProtAddress)

go/wlan2eth/arp/clients.go

@@ -22,11 +22,28 @@ func (c ClientInfo) StringMAC() string {
 var bridgedClients = make(map[string]ClientInfo)
 var bridgedClientsLock sync.Mutex
 
-func AddBridgedClient(ip net.IP, mac net.HardwareAddr, wlan0MAC net.HardwareAddr, eth0 string) {
+func AddBridgedClient(ip net.IP, mac net.HardwareAddr, eth0MAC, wlan0MAC net.HardwareAddr, eth0 string) {
 	log := logger.GetLogger()
 
 	// Ignore the wlan0 MAC address
 	if bytes.Equal(mac, wlan0MAC) {
+		log.Debugf("Not adding client IP (wlan0): %s", ip)
+		return
+	}
+	if bytes.Equal(mac, eth0MAC) {
+		log.Debugf("Not adding client IP (eth0): %s", ip)
+		return
+	}
+	if ip.String() == "0.0.0.0" {
+		log.Debug("Not adding client IP: 0.0.0.0")
+		return
+	}
+	if isAPIPA(ip) {
+		log.Debugf("Not adding client IP (APIPA): %s", ip)
+		return
+	}
+	if isExcluded(ip) {
+		log.Debugf("Not adding client IP (excluded): %s", ip)
 		return
 	}
 
@@ -112,3 +129,16 @@ func AddClientRoutes(eth0 string) {
 		}
 	}
 }
+
+func isAPIPA(ip net.IP) bool {
+	apiStart := net.ParseIP("169.254.0.0").To4()
+	apiEnd := net.ParseIP("169.254.255.255").To4()
+	ip4 := ip.To4()
+
+	return ip4 != nil && bytes.Compare(ip4, apiStart) >= 0 && bytes.Compare(ip4, apiEnd) <= 0
+}
+
+func isExcluded(ip net.IP) bool {
+	ip4 := ip.To4()
+	return ip4 != nil && (ip4[3] == 0 || ip4[3] == 255)
+}

go/wlan2eth/dhcp/dhcp_response.go

@@ -9,7 +9,7 @@ import (
 	"wlan2eth/logger"
 )
 
-func HandleDHCPResponse(packet gopacket.Packet, srcSocket, dstSocket int, srcName, dstName string, srcMAC, dstMAC net.HardwareAddr, wlan0MAC net.HardwareAddr, modifyClientSrc bool, eth0 string) {
+func HandleDHCPResponse(packet gopacket.Packet, srcSocket, dstSocket int, srcName, dstName string, srcMAC, dstMAC, eth0MAC, wlan0MAC net.HardwareAddr, modifyClientSrc bool, eth0 string) {
 	log := logger.GetLogger()
 
 	// Get the DHCP layer
@@ -23,7 +23,7 @@ func HandleDHCPResponse(packet gopacket.Packet, srcSocket, dstSocket int, srcNam
 	dhcp := dhcpLayer.(*layers.DHCPv4)
 	clientIP := dhcp.YourClientIP
 	if !clientIP.IsUnspecified() {
-		arp.AddBridgedClient(clientIP, dhcp.ClientHWAddr, wlan0MAC, eth0)
+		arp.AddBridgedClient(clientIP, dhcp.ClientHWAddr, eth0MAC, wlan0MAC, eth0)
 	}
 
 	clientMAC, ok := transactionIDToClientMAC[dhcp.Xid]
@@ -40,15 +40,22 @@ func HandleDHCPResponse(packet gopacket.Packet, srcSocket, dstSocket int, srcNam
 	// Get the Ethernet layer and cast it to its type
 	ethLayer := packet.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
 
-	// Modify the Ethernet source MAC address of the DHCP packet to clientMAC
+	//// Modify the Ethernet source MAC address of the DHCP packet to clientMAC
-	ethLayer.SrcMAC = clientMAC
+	//ethLayer.SrcMAC = clientMAC
+
+	// Modify the Ethernet source MAC address to point it towards our bridged client
+	ethLayer.DstMAC = clientMAC
 
 	// Get the IPv4 and UDP layers and cast them to their respective types
 	ipLayer := packet.Layer(layers.LayerTypeIPv4).(*layers.IPv4)
 	udpLayer := packet.Layer(layers.LayerTypeUDP).(*layers.UDP)
 
 	// Set the network layer for the UDP checksum computation
-	udpLayer.SetNetworkLayerForChecksum(ipLayer)
+	err := udpLayer.SetNetworkLayerForChecksum(ipLayer)
+	if err != nil {
+		log.Errorf("Failed to set the network layer for the UDP checksum computation: %v", err)
+		return
+	}
 
 	// Serialize the modified packet
 	buf := gopacket.NewSerializeBuffer()
@@ -56,7 +63,7 @@ func HandleDHCPResponse(packet gopacket.Packet, srcSocket, dstSocket int, srcNam
 		FixLengths:       true,
 		ComputeChecksums: true,
 	}
-	err := gopacket.SerializeLayers(buf, opts, ethLayer, ipLayer, udpLayer, dhcp)
+	err = gopacket.SerializeLayers(buf, opts, ethLayer, ipLayer, udpLayer, dhcp)
 	if err != nil {
 		log.Errorf("Error serializing DHCP response: %v", err)
 		return

go/wlan2eth/wlan2eth.go

@@ -145,21 +145,23 @@ func forwardPackets(srcSocket, dstSocket int, srcName string, dstName string) {
 		packet := gopacket.NewPacket(readBuf[:n], layers.LayerTypeEthernet, gopacket.Default)
 
 		if packet.ErrorLayer() != nil {
-			log.Errorf("Packet is not in Ethernet format: %v", packet.ErrorLayer().Error())
+			log.Warningf("Packet is not in Ethernet format: %v\n%s", packet.ErrorLayer().Error(), packet)
 			continue
 		}
 
 		ethLayer := packet.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
 		if ethLayer == nil {
-			log.Error("Packet does not have Ethernet layer.")
+			log.Warningf("Packet does not have Ethernet layer:\n%s", packet)
 			continue
 		}
 
+		ipv4Layer := packet.Layer(layers.LayerTypeIPv4)
+
 		arpLayer := packet.Layer(layers.LayerTypeARP)
 		if arpLayer != nil {
 			arpPacket := arpLayer.(*layers.ARP)
 			if arpPacket.Operation == layers.ARPRequest {
-				arp.HandleARPRequest(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, wlan0MAC, eth0)
+				arp.HandleARPRequest(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, eth0MAC, wlan0MAC, eth0)
 				continue
 			} else if arpPacket.Operation == layers.ARPReply {
 				arp.HandleARPResponse(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, eth0MAC)
@@ -171,7 +173,7 @@ func forwardPackets(srcSocket, dstSocket int, srcName string, dstName string) {
 		if udpLayer != nil {
 			udp := udpLayer.(*layers.UDP)
 			if udp.SrcPort == layers.UDPPort(67) && udp.DstPort == layers.UDPPort(68) {
-				dhcp.HandleDHCPResponse(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, wlan0MAC, dhcpModifyClientSrc, eth0)
+				dhcp.HandleDHCPResponse(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, eth0MAC, wlan0MAC, dhcpModifyClientSrc, eth0)
 				continue
 			} else if udp.SrcPort == layers.UDPPort(68) && udp.DstPort == layers.UDPPort(67) {
 				dhcp.HandleDHCPRequest(packet, srcSocket, dstSocket, srcName, dstName, srcMAC, dstMAC, dhcpModifyClientSrc)
@@ -186,12 +188,10 @@ func forwardPackets(srcSocket, dstSocket int, srcName string, dstName string) {
 		rawPacket := readBuf[:n]
 
 		if len(rawPacket) < 14 {
-			fmt.Println("too short")
+			log.Warningf("Packet too short (is this a bug??):\n%s", packet)
 			continue
 		}
 
-		ipv4Layer := packet.Layer(layers.LayerTypeIPv4)
-
 		// Check if the packet is addressed for eth0
 		if bytes.Equal(ethLayer.DstMAC, eth0MAC) {
 			copy(rawPacket[0:6], gatewayMAC) // Modify the destination to gatewayMAC
@@ -223,7 +223,7 @@ func forwardPackets(srcSocket, dstSocket int, srcName string, dstName string) {
 
 			// Modify the source MAC address directly in the raw packet data
 			copy(rawPacket[6:12], srcMAC)
-		} else {
+		} else if printPackets {
 			log.Debugf("Packet was not IPv4!\n%s", packet)
 			continue
 		}
@@ -241,7 +241,30 @@ func forwardPackets(srcSocket, dstSocket int, srcName string, dstName string) {
 		if printPackets {
 			log.Debugf("Forwarded packet from %s to %s:\n%s", srcName, dstName, packet)
 		} else {
-			log.Debugf("Forwarded packet from %s to %s", srcName, dstName)
+			var arrow string
+			if srcName == wlan0 {
+				arrow = fmt.Sprintf("%s <- %s", eth0, wlan0)
+			} else {
+				arrow = fmt.Sprintf("%s -> %s", eth0, wlan0)
+			}
+
+			if ipv4Layer != nil {
+				ipv4Packet := ipv4Layer.(*layers.IPv4)
+				clientMAC, found := arp.GetClientMACByIP(ipv4Packet.DstIP)
+				var macADDR string
+				if found {
+					macADDR = net.HardwareAddr(clientMAC).String()
+				} else {
+					macADDR = ":::::"
+				}
+				log.WithFields(logrus.Fields{
+					"iface": srcName,
+					"IP":    ipv4Packet.DstIP.String(),
+					"MAC":   macADDR,
+				}).Debugf("Forwarded packet: %s", arrow)
+			} else {
+				log.Debugf("Forwarded packet: %s", arrow)
+			}
 		}
 		time.Sleep(1 * time.Millisecond)
 	}