Add redir tproxy and dns inbound

common/redir/redir_linux.go

@@ -0,0 +1,37 @@
+package redir
+
+import (
+	"net"
+	"net/netip"
+	"syscall"
+
+	M "github.com/sagernet/sing/common/metadata"
+)
+
+func GetOriginalDestination(conn net.Conn) (destination netip.AddrPort, err error) {
+	rawConn, err := conn.(syscall.Conn).SyscallConn()
+	if err != nil {
+		return
+	}
+	var rawFd uintptr
+	err = rawConn.Control(func(fd uintptr) {
+		rawFd = fd
+	})
+	if err != nil {
+		return
+	}
+	const SO_ORIGINAL_DST = 80
+	if conn.RemoteAddr().(*net.TCPAddr).IP.To4() != nil {
+		raw, err := syscall.GetsockoptIPv6Mreq(int(rawFd), syscall.IPPROTO_IP, SO_ORIGINAL_DST)
+		if err != nil {
+			return netip.AddrPort{}, err
+		}
+		return netip.AddrPortFrom(M.AddrFromIP(raw.Multiaddr[4:8]), uint16(raw.Multiaddr[2])<<8+uint16(raw.Multiaddr[3])), nil
+	} else {
+		raw, err := syscall.GetsockoptIPv6MTUInfo(int(rawFd), syscall.IPPROTO_IPV6, SO_ORIGINAL_DST)
+		if err != nil {
+			return netip.AddrPort{}, err
+		}
+		return netip.AddrPortFrom(M.AddrFromIP(raw.Addr.Addr[:]), raw.Addr.Port), nil
+	}
+}

common/redir/redir_other.go

@@ -0,0 +1,13 @@
+//go:build !linux
+
+package redir
+
+import (
+	"net"
+	"net/netip"
+	"os"
+)
+
+func GetOriginalDestination(conn net.Conn) (destination netip.AddrPort, err error) {
+	return netip.AddrPort{}, os.ErrInvalid
+}

common/redir/tproxy_linux.go

@@ -0,0 +1,132 @@
+package redir
+
+import (
+	"encoding/binary"
+	"net"
+	"net/netip"
+	"os"
+	"strconv"
+	"syscall"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	F "github.com/sagernet/sing/common/format"
+	M "github.com/sagernet/sing/common/metadata"
+
+	"golang.org/x/sys/unix"
+)
+
+func TProxy(fd uintptr, isIPv6 bool) error {
+	err := syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_TRANSPARENT, 1)
+	if err != nil {
+		return err
+	}
+	if isIPv6 {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, unix.IPV6_TRANSPARENT, 1)
+	}
+	return err
+}
+
+func TProxyUDP(fd uintptr, isIPv6 bool) error {
+	err := syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1)
+	if err != nil {
+		return err
+	}
+	if isIPv6 {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, unix.IPV6_RECVORIGDSTADDR, 1)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func GetOriginalDestinationFromOOB(oob []byte) (netip.AddrPort, error) {
+	controlMessages, err := unix.ParseSocketControlMessage(oob)
+	if err != nil {
+		return netip.AddrPort{}, err
+	}
+	for _, message := range controlMessages {
+		if message.Header.Level == unix.SOL_IP && message.Header.Type == unix.IP_RECVORIGDSTADDR {
+			return netip.AddrPortFrom(M.AddrFromIP(message.Data[4:8]), binary.BigEndian.Uint16(message.Data[2:4])), nil
+		} else if message.Header.Level == unix.SOL_IPV6 && message.Header.Type == unix.IPV6_RECVORIGDSTADDR {
+			return netip.AddrPortFrom(M.AddrFromIP(message.Data[8:24]), binary.BigEndian.Uint16(message.Data[2:4])), nil
+		}
+	}
+	return netip.AddrPort{}, E.New("not found")
+}
+
+func DialUDP(lAddr *net.UDPAddr, rAddr *net.UDPAddr) (*net.UDPConn, error) {
+	rSockAddr, err := udpAddrToSockAddr(rAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	lSockAddr, err := udpAddrToSockAddr(lAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	fd, err := syscall.Socket(udpAddrFamily(lAddr, rAddr), syscall.SOCK_DGRAM, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.SetsockoptInt(fd, syscall.SOL_IP, syscall.IP_TRANSPARENT, 1); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.Bind(fd, lSockAddr); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	if err = syscall.Connect(fd, rSockAddr); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	fdFile := os.NewFile(uintptr(fd), F.ToString("net-udp-dial-", rAddr))
+	defer fdFile.Close()
+
+	c, err := net.FileConn(fdFile)
+	if err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+
+	return c.(*net.UDPConn), nil
+}
+
+func udpAddrToSockAddr(addr *net.UDPAddr) (syscall.Sockaddr, error) {
+	switch {
+	case addr.IP.To4() != nil:
+		ip := [4]byte{}
+		copy(ip[:], addr.IP.To4())
+
+		return &syscall.SockaddrInet4{Addr: ip, Port: addr.Port}, nil
+
+	default:
+		ip := [16]byte{}
+		copy(ip[:], addr.IP.To16())
+
+		zoneID, err := strconv.ParseUint(addr.Zone, 10, 32)
+		if err != nil {
+			zoneID = 0
+		}
+
+		return &syscall.SockaddrInet6{Addr: ip, Port: addr.Port, ZoneId: uint32(zoneID)}, nil
+	}
+}
+
+func udpAddrFamily(lAddr, rAddr *net.UDPAddr) int {
+	if (lAddr == nil || lAddr.IP.To4() != nil) && (rAddr == nil || lAddr.IP.To4() != nil) {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}

common/redir/tproxy_other.go

@@ -0,0 +1,25 @@
+//go:build !linux
+
+package redir
+
+import (
+	"net"
+	"net/netip"
+	"os"
+)
+
+func TProxy(fd uintptr, isIPv6 bool) error {
+	return os.ErrInvalid
+}
+
+func TProxyUDP(fd uintptr, isIPv6 bool) error {
+	return os.ErrInvalid
+}
+
+func GetOriginalDestinationFromOOB(oob []byte) (netip.AddrPort, error) {
+	return netip.AddrPort{}, os.ErrInvalid
+}
+
+func DialUDP(network string, lAddr *net.UDPAddr, rAddr *net.UDPAddr) (*net.UDPConn, error) {
+	return nil, os.ErrInvalid
+}