clash/proxy/redir/utils_linux.go

96 lines
2 KiB
Go

// +build linux
package redir
import (
"fmt"
"net"
"os"
"strconv"
"syscall"
)
// dialUDP acts like net.DialUDP for transparent proxy.
// It binds to a non-local address(`lAddr`).
func dialUDP(network string, 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(network, 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), fmt.Sprintf("net-udp-dial-%s", rAddr.String()))
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(net string, lAddr, rAddr *net.UDPAddr) int {
switch net[len(net)-1] {
case '4':
return syscall.AF_INET
case '6':
return syscall.AF_INET6
}
if (lAddr == nil || lAddr.IP.To4() != nil) && (rAddr == nil || lAddr.IP.To4() != nil) {
return syscall.AF_INET
}
return syscall.AF_INET6
}