Method from_tap_fd

net_util/src/tap.rs:241–295

(fd: RawFd, num_queue_pairs: usize)

    }

    pub fn from_tap_fd(fd: RawFd, num_queue_pairs: usize) -> Result<Tap> {
        // Ensure that the file is opened non-blocking, this is particularly
        // needed when opened via the shell for macvtap.
        // SAFETY: FFI call
        let ret = unsafe {
            let mut flags = libc::fcntl(fd, libc::F_GETFL);
            flags |= libc::O_NONBLOCK;
            libc::fcntl(fd, libc::F_SETFL, flags)
        };
        if ret < 0 {
            return Err(Error::ConfigureTap(IoError::last_os_error()));
        }

        // SAFETY: fd is a tap fd
        let tap_file = unsafe { File::from_raw_fd(fd) };
        let mut ifreq: libc::ifreq = ifreq {
            ifr_name: [0; libc::IFNAMSIZ],
            ifr_ifru: __c_anonymous_ifr_ifru { ifru_flags: 0 },
        };

        // Get current config including name
        // SAFETY: IOCTL with correct arguments
        unsafe { Self::ioctl_with_mut_ref(&tap_file, libc::TUNGETIFF as c_ulong, &mut ifreq)? };

        let if_name = {
            let ifr_ptr = ifreq.ifr_name.as_ptr();
            // SAFETY: The `ifr_name` field of the union is a valid, nul-terminated C string since it
            // was just set by the ioctl call, and we checked for errors.
            // We immediately convert the `CStr` to the owned `CString, so the memory of the union field
            // is not accessed or mutated during the lifetime of the `Cstr`.
            unsafe { CStr::from_ptr(ifr_ptr).to_owned() }
        };

        // Try and update flags. Depending on how the tap was created (macvtap
        // or via open_named()) this might return -EEXIST so we just ignore that.
        // SAFETY: access union fields
        unsafe {
            ifreq.ifr_ifru.ifru_flags =
                (libc::IFF_TAP | libc::IFF_NO_PI | libc::IFF_VNET_HDR) as c_short;
            if num_queue_pairs > 1 {
                ifreq.ifr_ifru.ifru_flags |= libc::IFF_MULTI_QUEUE as c_short;
            }
        }
        // SAFETY: IOCTL with correct arguments
        let ret = unsafe { ioctl_with_mut_ref(&tap_file, libc::TUNSETIFF as c_ulong, &mut ifreq) };
        if ret < 0 && IoError::last_os_error().raw_os_error().unwrap() != libc::EEXIST {
            return Err(Error::ConfigureTap(IoError::last_os_error()));
        }

        let tap = Tap { tap_file, if_name };
        let vnet_hdr_size = vnet_hdr_len() as i32;
        tap.set_vnet_hdr_size(vnet_hdr_size)?;

        Ok(tap)
    }

    /// Set the host-side IP address for the tap interface.
    pub fn set_ip_addr(&self, ip_addr: IpAddr, netmask: Option<IpAddr>) -> Result<()> {