netmaker/nm-proxy/proxy/proxy.go

package proxy

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net"
	"time"

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/google/gopacket/pcap"
	"github.com/gravitl/netmaker/nm-proxy/common"
	"github.com/gravitl/netmaker/nm-proxy/wg"
	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
)

const (
	defaultBodySize = 10000
	defaultPort     = 51722
)

type Config struct {
	Port        int
	BodySize    int
	Addr        string
	RemoteKey   string
	LocalKey    string
	WgInterface *wg.WGIface
	PeerConf    *wgtypes.PeerConfig
}

// Proxy -  WireguardProxy proxies
type Proxy struct {
	Ctx    context.Context
	Cancel context.CancelFunc

	Config     Config
	RemoteConn *net.UDPAddr
	LocalConn  net.Conn
}

func GetInterfaceIpv4Addr(interfaceName string) (addr string, err error) {
	var (
		ief      *net.Interface
		addrs    []net.Addr
		ipv4Addr net.IP
	)
	if ief, err = net.InterfaceByName(interfaceName); err != nil { // get interface
		return
	}
	if addrs, err = ief.Addrs(); err != nil { // get addresses
		return
	}
	for _, addr := range addrs { // get ipv4 address
		if ipv4Addr = addr.(*net.IPNet).IP.To4(); ipv4Addr != nil {
			break
		}
	}
	if ipv4Addr == nil {
		return "", errors.New(fmt.Sprintf("interface %s don't have an ipv4 address\n", interfaceName))
	}
	return ipv4Addr.String(), nil
}

func GetInterfaceListenAddr(port int) (*net.UDPAddr, error) {
	locallistenAddr := "127.0.0.1"
	udpAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", locallistenAddr, port))
	if err != nil {
		return udpAddr, err
	}
	if !common.IsHostNetwork {
		addrs, err := getBoardCastAddress()
		if err != nil {
			return udpAddr, err
		}
		for _, addr := range addrs {
			if liAddr := addr.(*net.IPNet).IP; liAddr != nil {
				udpAddr.IP = liAddr
				break
			}
		}
	}

	return udpAddr, nil
}

func getBoardCastAddress() ([]net.Addr, error) {
	localnets, err := net.Interfaces()
	if err != nil {
		return nil, err
	}
	var (
		ief   net.Interface
		addrs []net.Addr
	)
	for _, ief = range localnets {
		if ief.Flags&net.FlagBroadcast != 0 && ief.Flags&net.FlagUp != 0 {
			addrs, err = ief.Addrs()
			if err == nil {
				return addrs, nil
			}

		}
	}
	return nil, errors.New("couldn't obtain the broadcast addr")
}

func StartSniffer(ctx context.Context, ifaceName, ingGwAddr, extClientAddr string, port int) {
	log.Println("Starting Packet Sniffer for iface: ", ifaceName)
	var (
		snapshotLen int32 = 1024
		promiscuous bool  = false
		err         error
		timeout     time.Duration = 1 * time.Microsecond
		handle      *pcap.Handle
	)
	// Open device
	handle, err = pcap.OpenLive(ifaceName, snapshotLen, promiscuous, timeout)
	if err != nil {
		log.Println("failed to start sniffer for iface: ", ifaceName, err)
		return
	}
	// if err := handle.SetBPFFilter(fmt.Sprintf("src %s and port %d", extClientAddr, port)); err != nil {
	// 	log.Println("failed to set bpf filter: ", err)
	// 	return
	// }
	defer handle.Close()

	// var tcp layers.TCP
	// var icmp layers.ICMPv4
	// var udp layers.UDP
	// parser := gopacket.NewDecodingLayerParser(layers.LayerTypeIPv4, &udp, &tcp, &icmp)

	packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
	for {
		select {
		case <-ctx.Done():
			log.Println("Stopping packet sniffer for iface: ", ifaceName, " port: ", port)
			return
		default:
			packet, err := packetSource.NextPacket()
			if err == nil {
				//processPkt(ifaceName, packet)
				ipLayer := packet.Layer(layers.LayerTypeIPv4)
				if ipLayer != nil {
					fmt.Println("IPv4 layer detected.")
					ip, _ := ipLayer.(*layers.IPv4)

					// IP layer variables:
					// Version (Either 4 or 6)
					// IHL (IP Header Length in 32-bit words)
					// TOS, Length, Id, Flags, FragOffset, TTL, Protocol (TCP?),
					// Checksum, SrcIP, DstIP
					fmt.Println("#########################")
					fmt.Printf("From %s to %s\n", ip.SrcIP, ip.DstIP)
					fmt.Println("Protocol: ", ip.Protocol.String())
					if (ip.SrcIP.String() == extClientAddr && ip.DstIP.String() != ingGwAddr) ||
						(ip.DstIP.String() == extClientAddr && ip.SrcIP.String() != ingGwAddr) {

						log.Println("-----> Fowarding PKT From: ", ip.SrcIP, " to: ", ip.DstIP)
						c, err := net.Dial("ip", ip.DstIP.String())
						if err == nil {
							c.Write(ip.Payload)
							c.Close()
						} else {
							log.Println("------> Failed to forward packet from sniffer: ", err)

						}
					}

					fmt.Println("#########################")
				}
			}
		}

	}
}

func processPkt(iface string, packet gopacket.Packet) {
	// Let's see if the packet is an ethernet packet
	// ethernetLayer := packet.Layer(layers.LayerTypeEthernet)
	// if ethernetLayer != nil {
	// 	fmt.Println("Ethernet layer detected.")
	// 	ethernetPacket, _ := ethernetLayer.(*layers.Ethernet)
	// 	fmt.Println("Source MAC: ", ethernetPacket.SrcMAC)
	// 	fmt.Println("Destination MAC: ", ethernetPacket.DstMAC)
	// 	// Ethernet type is typically IPv4 but could be ARP or other
	// 	fmt.Println("Ethernet type: ", ethernetPacket.EthernetType)
	// 	fmt.Println()
	// }

	// Let's see if the packet is IP (even though the ether type told us)
	ipLayer := packet.Layer(layers.LayerTypeIPv4)
	if ipLayer != nil {
		fmt.Println("IPv4 layer detected.")
		ip, _ := ipLayer.(*layers.IPv4)

		// IP layer variables:
		// Version (Either 4 or 6)
		// IHL (IP Header Length in 32-bit words)
		// TOS, Length, Id, Flags, FragOffset, TTL, Protocol (TCP?),
		// Checksum, SrcIP, DstIP
		fmt.Printf("From %s to %s\n", ip.SrcIP, ip.DstIP)
		fmt.Println("Protocol: ", ip.Protocol)
		fmt.Println()

	}

	// udpLayer := packet.Layer(layers.LayerTypeUDP)
	// if udpLayer != nil {
	// 	udp, _ := udpLayer.(*layers.UDP)
	// 	fmt.Printf("UDP: From port %d to %d\n", udp.SrcPort, udp.DstPort)
	// 	fmt.Println()
	// }

	// // Iterate over all layers, printing out each layer type
	// fmt.Println("All packet layers:")
	// for _, layer := range packet.Layers() {
	// 	fmt.Println("- ", layer.LayerType())
	// }

	// When iterating through packet.Layers() above,
	// if it lists Payload layer then that is the same as
	// this applicationLayer. applicationLayer contains the payload
	// applicationLayer := packet.ApplicationLayer()
	// if applicationLayer != nil {
	// 	fmt.Println("Application layer/Payload found.")
	// 	fmt.Printf("%s\n", applicationLayer.Payload())

	// 	// Search for a string inside the payload
	// 	if strings.Contains(string(applicationLayer.Payload()), "HTTP") {
	// 		fmt.Println("HTTP found!")
	// 	}
	// }

	// Check for errors
	if err := packet.ErrorLayer(); err != nil {
		fmt.Println("Error decoding some part of the packet:", err)
	}
}