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
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
	logLvl := flag.Int("log", 4, "allowed: 5 (debug), 4 (info), 3 (warning), 2 (error), 1 (fatal)")
	oldip := flag.String("oldip", "10.0.0.11", "IP before change")
	newip := flag.String("newip", "10.0.0.15", "IP after change")
	oldmac := flag.String("oldmac", "52:54:00:12:34:56", "MAC before change")
	newmac := flag.String("newmac", "52:54:00:12:34:aa", "MAC after change")
	passthrough := flag.Bool("passthrough", false, "Whether to pass every traffic through")
	proxy := flag.String("proxy", "1", "Number of the proxy switch")
	flag.Parse()
	log.SetLevel(log.Level(*logLvl))
	OldMac, _ = net.ParseMAC(*oldmac)
	NewMac, _ = net.ParseMAC(*newmac)
	OldIP = net.ParseIP(*oldip).To4()
	NewIP = net.ParseIP(*newip).To4()
	log.SetFormatter(&log.TextFormatter{
		DisableTimestamp: true,
	})
	c1 := cmd.New("vde_plug", "/run/vde/sw_main.sock")
	c2 := cmd.New("vde_plug", "/run/vde/sw_proxy"+*proxy+".sock")
	c1.Execute()
	c2.Execute()
	go pipeForward(c1.OutReader, c2.InWriter, cmd.In, *passthrough)
	go pipeForward(c2.OutReader, c1.InWriter, cmd.Out, *passthrough)
	c1.WaitH()
	c2.WaitH()
}

// Reads from an input and writes to and output,
// do things to the content in between.
// Is meant to be run concurrently with "go pipeForward(...)"
func pipeForward(reader io.Reader, writer io.Writer, prefix string, passthrough bool) {
	for {
		// Read frame length
		frameLength := make([]byte, 2)
		if _, err := reader.Read(frameLength); err == io.EOF {
			log.Fatal(prefix, "Error reading frame length")
		}

		// Read actual frame
		frameBytes := make([]byte, int(binary.BigEndian.Uint16(frameLength)))
		if _, err := reader.Read(frameBytes); err == io.EOF {
			log.Fatal(prefix, "Error reading frame data")
		}

		// 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)
		if prefix == cmd.In {
			log.Debug(prefix, "Incoming MAC rewritten ", frame.DstMAC, OldMac)
			frame.DstMAC = OldMac
		} else if prefix == cmd.Out {
			log.Debug(prefix, "Outgoing MAC rewritten ", frame.SrcMAC, NewMac)
			frame.SrcMAC = NewMac
		}

		// Handle IPv6 packet
		if ipv4layer := packet.Layer(layers.LayerTypeIPv4); ipv4layer != nil {
			ipv4Packet, _ := ipv4layer.(*layers.IPv4)
			if prefix == cmd.In {
				log.Debug(prefix, "Incoming IP rewritten ", ipv4Packet.DstIP, OldIP)
				ipv4Packet.DstIP = OldIP
			} else if prefix == cmd.Out {
				log.Debug(prefix, "Outgoing IP rewritten ", ipv4Packet.SrcIP, NewIP)
				ipv4Packet.SrcIP = NewIP
			}

			// Handle ICMP packet (based on IPv4)
			if icmpLayer := packet.Layer(layers.LayerTypeICMPv4); icmpLayer != nil {
				icmpPacket, _ := icmpLayer.(*layers.ICMPv4)
				log.Debugf("%s ICMP packet\nType/Code:\t%s\n", prefix, icmpPacket.TypeCode.String())
			}

			// Handle DHCP packet (based on IPv4) - drop for now
			if dhcpLayer := packet.Layer(layers.LayerTypeDHCPv4); dhcpLayer != nil && !passthrough {
				//dhcpPacket, _ := dhcpLayer.(*layers.DHCPv4)
				log.Info(prefix, "DHCP packet dropped")
				continue
			}

			// Handle TCP packet
			if tcpLayer := packet.Layer(layers.LayerTypeTCP); tcpLayer != nil {
				tcpPacket, _ := tcpLayer.(*layers.TCP)
				if err := tcpPacket.SetNetworkLayerForChecksum(ipv4Packet); err != nil {
					log.Error(prefix, "Error setting network layer for checksum", err)
				}
			}
		}

		// Drop IPv6 packets
		if ipv6layer := packet.Layer(layers.LayerTypeIPv6); ipv6layer != nil && !passthrough {
			log.Info(prefix, "IPv6 packet dropped")
			continue
		}

		// Handle ARP packet
		if frame.EthernetType == layers.EthernetTypeARP {
			arpPacket := packet.Layer(layers.LayerTypeARP).(*layers.ARP)
			log.Debugf(
				"%sARP before modification\nAddrType:\t%s\nProtocol:\t%s\nOperation:\t%s\n"+
					"SrcHwAddress:\t%s\nSrcProtAddress:\t%s\nDstHwAddress:\t%s\nDstProtAddress:\t%s\n",
				prefix,
				arpPacket.AddrType,
				arpPacket.Protocol,
				strconv.Itoa(int(arpPacket.Operation)),
				net.HardwareAddr(arpPacket.SourceHwAddress),
				net.IP(arpPacket.SourceProtAddress),
				net.HardwareAddr(arpPacket.DstHwAddress),
				net.IP(arpPacket.DstProtAddress),
			)

			if prefix == cmd.In {
				arpPacket.DstProtAddress = OldIP
				log.Debugf(
					"%sARP after modification\nDstProtAddress:\t%s\n",
					prefix,
					net.IP(arpPacket.DstProtAddress),
				)
				if arpPacket.Operation == layers.ARPReply {
					isInteresting = true
					arpPacket.DstHwAddress = OldMac
					log.Debugf(
						"%sDstHwAddress:\t%s\n",
						prefix,
						net.HardwareAddr(arpPacket.DstHwAddress),
					)
				}
			} else if prefix == cmd.Out {
				arpPacket.SourceHwAddress = NewMac
				arpPacket.SourceProtAddress = NewIP
				log.Debugf(
					"%sARP after modification\nSrcHwAddress:\t%s\nSrcProtAddress:\t%s\n",
					prefix,
					net.HardwareAddr(arpPacket.SourceHwAddress),
					net.IP(arpPacket.SourceProtAddress),
				)
			}
		}

		// Forward original frame to other plug
		if passthrough {
			writer.Write(frameLength)
			writer.Write(frameBytes)
			continue
		}

		// Serialize packet back to binary
		buf := gopacket.NewSerializeBuffer()
		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 {
			util.WriteBinary(fmt.Sprintf("/tmp/pck_%di.dat", time.Now().Unix()), frameBytes)
			util.WriteBinary(fmt.Sprintf("/tmp/pck_%do.dat", time.Now().Unix()), newFrameBytes)
			//util.WritePcap("xyz.pcap", packet.Data(), packet.Metadata().CaptureInfo)
		}

		// Forward modified frame to other plug
		writer.Write(newFrameLength)
		writer.Write(newFrameBytes)
	}
}