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|
package l2tp
import (
"fmt"
"os"
"syscall"
"golang.org/x/sys/unix"
)
type controlPlane struct {
local, remote unix.Sockaddr
fd int
file *os.File
rc syscall.RawConn
connected bool
}
func (cp *controlPlane) recvFrom(p []byte) (n int, addr unix.Sockaddr, err error) {
cerr := cp.rc.Read(func(fd uintptr) bool {
n, addr, err = unix.Recvfrom(int(fd), p, unix.MSG_NOSIGNAL)
return err != unix.EAGAIN && err != unix.EWOULDBLOCK
})
if err != nil {
return n, addr, err
}
return n, addr, cerr
}
func (cp *controlPlane) write(b []byte) (n int, err error) {
if cp.connected {
return cp.file.Write(b)
}
return cp.writeTo(b, cp.remote)
}
func (cp *controlPlane) writeTo(p []byte, addr unix.Sockaddr) (n int, err error) {
return len(p), cp.sendto(p, addr)
}
func (cp *controlPlane) sendto(p []byte, to unix.Sockaddr) (err error) {
cerr := cp.rc.Write(func(fd uintptr) bool {
err = unix.Sendto(int(fd), p, unix.MSG_NOSIGNAL, to)
return err != unix.EAGAIN && err != unix.EWOULDBLOCK
})
if err != nil {
return err
}
return cerr
}
func (cp *controlPlane) close() (err error) {
if cp.file != nil {
err = cp.file.Close()
cp.file = nil
}
return
}
func (cp *controlPlane) connect() error {
err := unix.Connect(cp.fd, cp.remote)
if err == nil {
cp.connected = true
}
return err
}
func (cp *controlPlane) connectTo(sa unix.Sockaddr) error {
cp.remote = sa
return cp.connect()
}
func (cp *controlPlane) bind() error {
return unix.Bind(cp.fd, cp.local)
}
func tunnelSocket(family, protocol int) (fd int, err error) {
fd, err = unix.Socket(family, unix.SOCK_DGRAM, protocol)
if err != nil {
return -1, fmt.Errorf("socket: %v", err)
}
if err = unix.SetNonblock(fd, true); err != nil {
unix.Close(fd)
return -1, fmt.Errorf("failed to set socket nonblocking: %v", err)
}
flags, err := unix.FcntlInt(uintptr(fd), unix.F_GETFD, 0)
if err != nil {
unix.Close(fd)
return -1, fmt.Errorf("fcntl(F_GETFD): %v", err)
}
_, err = unix.FcntlInt(uintptr(fd), unix.F_SETFD, flags|unix.FD_CLOEXEC)
if err != nil {
unix.Close(fd)
return -1, fmt.Errorf("fcntl(F_SETFD, FD_CLOEXEC): %v", err)
}
return fd, nil
}
func newL2tpControlPlane(localAddr, remoteAddr unix.Sockaddr) (*controlPlane, error) {
var family, protocol int
switch localAddr.(type) {
case *unix.SockaddrInet4:
family = unix.AF_INET
protocol = unix.IPPROTO_UDP
case *unix.SockaddrInet6:
family = unix.AF_INET6
protocol = unix.IPPROTO_UDP
case *unix.SockaddrL2TPIP:
family = unix.AF_INET
protocol = unix.IPPROTO_L2TP
case *unix.SockaddrL2TPIP6:
family = unix.AF_INET6
protocol = unix.IPPROTO_L2TP
default:
return nil, fmt.Errorf("unexpected address type %T", localAddr)
}
fd, err := tunnelSocket(family, protocol)
if err != nil {
return nil, err
}
file := os.NewFile(uintptr(fd), "l2tp")
sc, err := file.SyscallConn()
if err != nil {
unix.Close(fd)
return nil, err
}
return &controlPlane{
local: localAddr,
remote: remoteAddr,
fd: fd,
file: file,
rc: sc,
connected: false,
}, nil
}
|
