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// +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()
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
}
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