func()

in cni/internal/netlink.go [198:245]

• 36 lines of code
• 7 McCabe index (conditional complexity)

func (defaultNetlinkOps) CreateTap(name string, mtu int, ownerUID, ownerGID int) (netlink.Link, error) {
	tapLinkAttrs := netlink.NewLinkAttrs()
	tapLinkAttrs.Name = name
	tapLink := &netlink.Tuntap{
		LinkAttrs: tapLinkAttrs,

		// We want a tap device (L2) as opposed to a tun (L3)
		Mode: netlink.TUNTAP_MODE_TAP,

		// Firecracker does not support multiqueue tap devices at this time:
		// https://github.com/firecracker-microvm/firecracker/issues/750
		Queues: 1,

		Flags: netlink.TUNTAP_ONE_QUEUE | // single queue tap device
			netlink.TUNTAP_VNET_HDR, // parse vnet headers added by the vm's virtio_net implementation
	}

	err := netlink.LinkAdd(tapLink)
	if err != nil {
		return nil, errors.Wrap(err, "failed to create tap device")
	}

	for _, tapFd := range tapLink.Fds {
		err = unix.IoctlSetInt(int(tapFd.Fd()), unix.TUNSETOWNER, ownerUID)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to set tap %s owner to uid %d",
				name, ownerUID)
		}

		err = unix.IoctlSetInt(int(tapFd.Fd()), unix.TUNSETGROUP, ownerGID)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to set tap %s group to gid %d",
				name, ownerGID)
		}
	}

	err = netlink.LinkSetMTU(tapLink, mtu)
	if err != nil {
		return nil, errors.Wrapf(err, "failed to set tap device MTU to %d", mtu)
	}

	err = netlink.LinkSetUp(tapLink)
	if err != nil {
		return nil, errors.Wrap(err, "failed to set tap up")
	}

	return tapLink, nil
}