github.com/database64128/shadowsocks-go@v1.10.2-0.20240315062903-143a773533f1/conn/conn_linux.go

package conn

import (
	"fmt"
	"net/netip"
	"unsafe"

	"golang.org/x/sys/unix"
)

// TransparentSocketControlMessageBufferSize specifies the buffer size for receiving IPV6_RECVORIGDSTADDR socket control messages.
const TransparentSocketControlMessageBufferSize = unix.SizeofCmsghdr + (unix.SizeofSockaddrInet6+unix.SizeofPtr-1) & ^(unix.SizeofPtr-1)

func setFwmark(fd, fwmark int) error {
	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_MARK, fwmark); err != nil {
		return fmt.Errorf("failed to set socket option SO_MARK: %w", err)
	}
	return nil
}

func setTrafficClass(fd int, network string, trafficClass int) error {
	// Set IP_TOS for both v4 and v6.
	if err := unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_TOS, trafficClass); err != nil {
		return fmt.Errorf("failed to set socket option IP_TOS: %w", err)
	}

	switch network {
	case "tcp4", "udp4":
	case "tcp6", "udp6":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_TCLASS, trafficClass); err != nil {
			return fmt.Errorf("failed to set socket option IPV6_TCLASS: %w", err)
		}
	default:
		return fmt.Errorf("unsupported network: %s", network)
	}

	return nil
}

func setTransparent(fd int, network string) error {
	switch network {
	case "tcp4", "udp4":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_TRANSPARENT, 1); err != nil {
			return fmt.Errorf("failed to set socket option IP_TRANSPARENT: %w", err)
		}
	case "tcp6", "udp6":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_TRANSPARENT, 1); err != nil {
			return fmt.Errorf("failed to set socket option IPV6_TRANSPARENT: %w", err)
		}
	default:
		return fmt.Errorf("unsupported network: %s", network)
	}
	return nil
}

func setPMTUD(fd int, network string) error {
	// Set IP_MTU_DISCOVER for both v4 and v6.
	if err := unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_MTU_DISCOVER, unix.IP_PMTUDISC_DO); err != nil {
		return fmt.Errorf("failed to set socket option IP_MTU_DISCOVER: %w", err)
	}

	switch network {
	case "tcp4", "udp4":
	case "tcp6", "udp6":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_MTU_DISCOVER, unix.IP_PMTUDISC_DO); err != nil {
			return fmt.Errorf("failed to set socket option IPV6_MTU_DISCOVER: %w", err)
		}
	default:
		return fmt.Errorf("unsupported network: %s", network)
	}

	return nil
}

func setRecvPktinfo(fd int, network string) error {
	switch network {
	case "udp4":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_PKTINFO, 1); err != nil {
			return fmt.Errorf("failed to set socket option IP_PKTINFO: %w", err)
		}
	case "udp6":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_RECVPKTINFO, 1); err != nil {
			return fmt.Errorf("failed to set socket option IPV6_RECVPKTINFO: %w", err)
		}
	default:
		return fmt.Errorf("unsupported network: %s", network)
	}
	return nil
}

func setRecvOrigDstAddr(fd int, network string) error {
	// Set IP_RECVORIGDSTADDR for both v4 and v6.
	if err := unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_RECVORIGDSTADDR, 1); err != nil {
		return fmt.Errorf("failed to set socket option IP_RECVORIGDSTADDR: %w", err)
	}

	switch network {
	case "udp4":
	case "udp6":
		if err := unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_RECVORIGDSTADDR, 1); err != nil {
			return fmt.Errorf("failed to set socket option IPV6_RECVORIGDSTADDR: %w", err)
		}
	default:
		return fmt.Errorf("unsupported network: %s", network)
	}

	return nil
}

func (fns setFuncSlice) appendSetTransparentFunc(transparent bool) setFuncSlice {
	if transparent {
		return append(fns, setTransparent)
	}
	return fns
}

func (fns setFuncSlice) appendSetRecvOrigDstAddrFunc(recvOrigDstAddr bool) setFuncSlice {
	if recvOrigDstAddr {
		return append(fns, setRecvOrigDstAddr)
	}
	return fns
}

func (lso ListenerSocketOptions) buildSetFns() setFuncSlice {
	return setFuncSlice{}.
		appendSetFwmarkFunc(lso.Fwmark).
		appendSetTrafficClassFunc(lso.TrafficClass).
		appendSetReusePortFunc(lso.ReusePort).
		appendSetTransparentFunc(lso.Transparent).
		appendSetPMTUDFunc(lso.PathMTUDiscovery).
		appendSetRecvPktinfoFunc(lso.ReceivePacketInfo).
		appendSetRecvOrigDstAddrFunc(lso.ReceiveOriginalDestAddr)
}

func ParseOrigDstAddrCmsg(cmsg []byte) (netip.AddrPort, error) {
	if len(cmsg) < unix.SizeofCmsghdr {
		return netip.AddrPort{}, fmt.Errorf("control message length %d is shorter than cmsghdr length", len(cmsg))
	}

	cmsghdr := (*unix.Cmsghdr)(unsafe.Pointer(&cmsg[0]))

	switch {
	case cmsghdr.Level == unix.IPPROTO_IP && cmsghdr.Type == unix.IP_ORIGDSTADDR && len(cmsg) >= unix.SizeofCmsghdr+unix.SizeofSockaddrInet4:
		sa := (*unix.RawSockaddrInet4)(unsafe.Pointer(&cmsg[unix.SizeofCmsghdr]))
		return SockaddrInet4ToAddrPort(sa), nil

	case cmsghdr.Level == unix.IPPROTO_IPV6 && cmsghdr.Type == unix.IPV6_ORIGDSTADDR && len(cmsg) >= unix.SizeofCmsghdr+unix.SizeofSockaddrInet6:
		sa := (*unix.RawSockaddrInet6)(unsafe.Pointer(&cmsg[unix.SizeofCmsghdr]))
		return SockaddrInet6ToAddrPort(sa), nil

	default:
		return netip.AddrPort{}, fmt.Errorf("unknown control message level %d type %d", cmsghdr.Level, cmsghdr.Type)
	}
}