n   uint32
		err error
	)
	switch runtime.GOOS {
	case "darwin", "ios":
		n, err = syscall.SysctlUint32("kern.ipc.somaxconn")
	case "freebsd":
		n, err = syscall.SysctlUint32("kern.ipc.soacceptqueue")
	case "netbsd":
		// NOTE: NetBSD has no somaxconn-like kernel state so far
	case "openbsd":
		n, err = syscall.SysctlUint32("kern.somaxconn")
	}
	if n == 0 || err != nil {
		return syscall.SOMAXCONN
	}

func adjustFileLimit(lim *Rlimit) {
	// On older macOS, setrlimit(RLIMIT_NOFILE, lim) with lim.Cur = infinity fails.
	// Set to the value of kern.maxfilesperproc instead.
	n, err := SysctlUint32("kern.maxfilesperproc")
	if err != nil {
		return
	}
	if lim.Cur > uint64(n) {
		lim.Cur = uint64(n)
	}

	ifanm := &wireFormat{extOff: sizeofIfAnnouncemsghdrDragonFlyBSD4, bodyOff: sizeofIfAnnouncemsghdrDragonFlyBSD4}
	ifanm.parse = ifanm.parseInterfaceAnnounceMessage

	rel, _ := syscall.SysctlUint32("kern.osreldate")
	if rel >= 500705 {
		// https://github.com/DragonFlyBSD/DragonFlyBSD/commit/43a373152df2d405c9940983e584e6a25e76632d
		// but only the size of struct ifa_msghdr actually changed
		rtmVersion = 7

			t.Errorf("failed to cleanup jail: %v", err)
		}
	})

	return int(id), root
}

func TestJailAttach(t *testing.T) {
	if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
		jailed, err := syscall.SysctlUint32("security.jail.jailed")
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(2)
		}
		if jailed != 1 {
			t.Fatalf("jailed = %d, want 1", jailed)
		}
		return
	}

	testenv.MustHaveGoBuild(t)

		ifmam = &wireFormat{extOff: sizeofIfmaMsghdrFreeBSD10, bodyOff: sizeofIfmaMsghdrFreeBSD10}
		ifanm = &wireFormat{extOff: sizeofIfAnnouncemsghdrFreeBSD10, bodyOff: sizeofIfAnnouncemsghdrFreeBSD10}
	}
	rel, _ := syscall.SysctlUint32("kern.osreldate")
	switch {
	case rel < 800000:
		if compatFreeBSD32 {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7
		}

// http://lists.dragonflybsd.org/pipermail/users/2019-September/358280.html
const _dragonflyABIChangeVersion = 500705

func supportsABI(ver uint32) bool {
	osreldateOnce.Do(func() { osreldate, _ = SysctlUint32("kern.osreldate") })
	return osreldate >= ver
}

type SockaddrDatalink struct {
	Len    uint8
	Family uint8
	Index  uint16
	Type   uint8
	Nlen   uint8
	Alen   uint8
	Slen   uint8