//go:build linux
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// +build linux
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package tcp
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import (
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"syscall"
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"github.com/v2fly/v2ray-core/v5/common/net"
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"github.com/v2fly/v2ray-core/v5/transport/internet"
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)
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const SO_ORIGINAL_DST = 80 // nolint: revive,stylecheck
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func GetOriginalDestination(conn internet.Connection) (net.Destination, error) {
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sysrawconn, f := conn.(syscall.Conn)
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if !f {
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return net.Destination{}, newError("unable to get syscall.Conn")
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}
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rawConn, err := sysrawconn.SyscallConn()
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if err != nil {
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return net.Destination{}, newError("failed to get sys fd").Base(err)
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}
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var dest net.Destination
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err = rawConn.Control(func(fd uintptr) {
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var remoteIP net.IP
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switch addr := conn.RemoteAddr().(type) {
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case *net.TCPAddr:
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remoteIP = addr.IP
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case *net.UDPAddr:
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remoteIP = addr.IP
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default:
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newError("failed to call getsockopt").WriteToLog()
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return
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}
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if remoteIP.To4() != nil {
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// ipv4
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addr, err := syscall.GetsockoptIPv6Mreq(int(fd), syscall.IPPROTO_IP, SO_ORIGINAL_DST)
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if err != nil {
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newError("failed to call getsockopt").Base(err).WriteToLog()
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return
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}
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ip := net.IPAddress(addr.Multiaddr[4:8])
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port := uint16(addr.Multiaddr[2])<<8 + uint16(addr.Multiaddr[3])
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dest = net.TCPDestination(ip, net.Port(port))
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} else {
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// ipv6
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addr, err := syscall.GetsockoptIPv6MTUInfo(int(fd), syscall.IPPROTO_IPV6, SO_ORIGINAL_DST)
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if err != nil {
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newError("failed to call getsockopt").Base(err).WriteToLog()
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return
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}
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ip := net.IPAddress(addr.Addr.Addr[:])
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port := net.PortFromBytes([]byte{byte(addr.Addr.Port), byte(addr.Addr.Port >> 8)})
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dest = net.TCPDestination(ip, port)
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}
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})
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if err != nil {
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return net.Destination{}, newError("failed to control connection").Base(err)
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}
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if !dest.IsValid() {
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return net.Destination{}, newError("failed to call getsockopt")
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}
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return dest, nil
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}
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