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fakeudp_linux.go
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fakeudp_linux.go
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//go:build linux
// +build linux
package dokodemo
import (
"fmt"
"net"
"os"
"syscall"
"golang.org/x/sys/unix"
)
func FakeUDP(addr *net.UDPAddr, mark int) (net.PacketConn, error) {
var af int
var sockaddr syscall.Sockaddr
if len(addr.IP) == 4 {
af = syscall.AF_INET
sockaddr = &syscall.SockaddrInet4{Port: addr.Port}
copy(sockaddr.(*syscall.SockaddrInet4).Addr[:], addr.IP)
} else {
af = syscall.AF_INET6
sockaddr = &syscall.SockaddrInet6{Port: addr.Port}
copy(sockaddr.(*syscall.SockaddrInet6).Addr[:], addr.IP)
}
var fd int
var err error
if fd, err = syscall.Socket(af, syscall.SOCK_DGRAM, 0); err != nil {
return nil, &net.OpError{Op: "fake", Err: fmt.Errorf("socket open: %s", err)}
}
if mark != 0 {
if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, mark); err != nil {
syscall.Close(fd)
return nil, &net.OpError{Op: "fake", Err: fmt.Errorf("set socket option: SO_MARK: %s", err)}
}
}
if err = syscall.SetsockoptInt(fd, syscall.SOL_IP, syscall.IP_TRANSPARENT, 1); err != nil {
syscall.Close(fd)
return nil, &net.OpError{Op: "fake", Err: fmt.Errorf("set socket option: IP_TRANSPARENT: %s", err)}
}
syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, unix.SO_REUSEPORT, 1)
if err = syscall.Bind(fd, sockaddr); err != nil {
syscall.Close(fd)
return nil, &net.OpError{Op: "fake", Err: fmt.Errorf("socket bind: %s", err)}
}
fdFile := os.NewFile(uintptr(fd), fmt.Sprintf("net-udp-fake-%s", addr.String()))
defer fdFile.Close()
packetConn, err := net.FilePacketConn(fdFile)
if err != nil {
syscall.Close(fd)
return nil, &net.OpError{Op: "fake", Err: fmt.Errorf("convert file descriptor to connection: %s", err)}
}
return packetConn, nil
}