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package sys
import (
"fmt"
"math"
"os"
"runtime"
"strconv"
"github.com/cilium/ebpf/internal/unix"
)
var ErrClosedFd = unix.EBADF
type FD struct {
raw int
}
func newFD(value int) *FD {
fd := &FD{value}
runtime.SetFinalizer(fd, (*FD).Close)
return fd
}
// NewFD wraps a raw fd with a finalizer.
//
// You must not use the raw fd after calling this function, since the underlying
// file descriptor number may change. This is because the BPF UAPI assumes that
// zero is not a valid fd value.
func NewFD(value int) (*FD, error) {
if value < 0 {
return nil, fmt.Errorf("invalid fd %d", value)
}
fd := newFD(value)
if value != 0 {
return fd, nil
}
dup, err := fd.Dup()
_ = fd.Close()
return dup, err
}
func (fd *FD) String() string {
return strconv.FormatInt(int64(fd.raw), 10)
}
func (fd *FD) Int() int {
return fd.raw
}
func (fd *FD) Uint() uint32 {
if fd.raw < 0 || int64(fd.raw) > math.MaxUint32 {
// Best effort: this is the number most likely to be an invalid file
// descriptor. It is equal to -1 (on two's complement arches).
return math.MaxUint32
}
return uint32(fd.raw)
}
func (fd *FD) Close() error {
if fd.raw < 0 {
return nil
}
value := int(fd.raw)
fd.raw = -1
fd.Forget()
return unix.Close(value)
}
func (fd *FD) Forget() {
runtime.SetFinalizer(fd, nil)
}
func (fd *FD) Dup() (*FD, error) {
if fd.raw < 0 {
return nil, ErrClosedFd
}
// Always require the fd to be larger than zero: the BPF API treats the value
// as "no argument provided".
dup, err := unix.FcntlInt(uintptr(fd.raw), unix.F_DUPFD_CLOEXEC, 1)
if err != nil {
return nil, fmt.Errorf("can't dup fd: %v", err)
}
return newFD(dup), nil
}
func (fd *FD) File(name string) *os.File {
fd.Forget()
return os.NewFile(uintptr(fd.raw), name)
}
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