You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: sockopt_linux.go
    path of file: ./repos/v2ray-core/transport/internet/tcp
    
    the code of the file until where you have to start completion: // +build linux
// +build !confonly

package tcp

import (
	"syscall"

	"v2ray.com/core/common/net"
	"v2ray.com/core/transport/internet"
)

const SO_ORIGINAL_DST = 80

func GetOriginalDestination(conn internet.Connection) (net.Destination, error) {
	sysrawconn, f := conn.(syscall.Conn)
	if !f {
		return net.Destination{}, newError("unable to get syscall.Conn")
	}
	rawConn, err := sysrawconn.SyscallConn()
	if err != nil {
		return net.Destination{}, newError("failed to get sys fd").Base(err)
	}
	var dest net.Destination
	err = rawConn.Control(func(fd uintptr) {
		addr, err := syscall.GetsockoptIPv6Mreq(int(fd), syscall.IPPROTO_IP, SO_ORIGINAL_DST)
		if err != nil {
			newError("failed to call getsockopt").Base(err).WriteToLog()
			retur
    
func GetOriginalDestination(conn internet.Connection) (net.Destination, error) {
	sysrawconn, f := conn.(syscall.Conn)
	if !f {
		return net.Destination{}, newError("unable to get syscall.Conn")
	}
	rawConn, err := sysrawconn.SyscallConn()
	if err != nil {
		return net.Destination{}, newError("failed to get sys fd").Base(err)
	}
	var dest net.Destination
	err = rawConn.Control(func(fd uintptr) {
		addr, err := syscall.GetsockoptIPv6Mreq(int(fd), syscall.IPPROTO_IP, SO_ORIGINAL_DST)
		if err != nil {
			newError("failed to call getsockopt").Base(err).WriteToLog()
			return
		}
		ip := net.IPAddress(addr.Multiaddr[4:8])
		port := uint16(addr.Multiaddr[2])<<8 + uint16(addr.Multiaddr[3])
		dest = net.TCPDestination(ip, net.Port(port))
	})
	if err != nil {
		return net.Destination{}, newError("failed to control connection").Base(err)
	}
	if !dest.IsValid() {
		return net.Destination{}, newError("failed to call getsockopt")
	}
	return dest, nil
}