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markedconn.go
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markedconn.go
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// +build linux
package markedconn
import (
"fmt"
"net"
"os"
"syscall"
)
// DialMarkedTCP creates a new TCP connection and marks it with the provided mark.
func DialMarkedTCP(network string, laddr, raddr *net.TCPAddr, mark int) (net.Conn, error) {
fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, 0)
if err != nil {
return nil, fmt.Errorf("Failed to create socket: %s", err)
}
err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, mark)
if err != nil {
return nil, fmt.Errorf("Failed to assing mark to socket: %s", err)
}
f := os.NewFile(uintptr(fd), raddr.String())
defer f.Close() // nolint
conn, err := net.FileConn(f)
if err != nil {
return nil, fmt.Errorf("Unable to create downstream connection: %s", err)
}
address := &syscall.SockaddrInet4{
Port: raddr.Port,
}
copy(address.Addr[:], raddr.IP.To4())
if err := syscall.SetNonblock(fd, false); err != nil {
conn.Close() // nolint
return nil, fmt.Errorf("unable to set socket options: %s", err)
}
if err := syscall.Connect(fd, address); err != nil {
conn.Close() // nolint
return nil, fmt.Errorf("Unable to connect: %s", err)
}
return conn, nil
}
// MarkConnection marks an existing connection with a mark
func MarkConnection(conn net.Conn, mark int) error {
setMark := func(fd uintptr) {
syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_MARK, mark) // nolint
}
rawconn, err := conn.(*net.TCPConn).SyscallConn()
if err != nil {
return err
}
return rawconn.Control(setMark)
}