// SetupVeth sets up a virtual ethernet link.
// Should be in container netns.
func SetupVeth(contVethName string, mtu int, hostNS *os.File) (hostVeth, contVeth netlink.Link, err error) {
	var hostVethName string
	hostVethName, contVeth, err = makeVeth(contVethName, mtu)
	if err != nil {
		return
	}

	if err = netlink.LinkSetUp(contVeth); err != nil {
		err = fmt.Errorf("failed to set %q up: %v", contVethName, err)
		return
	}

	hostVeth, err = netlink.LinkByName(hostVethName)
	if err != nil {
		err = fmt.Errorf("failed to lookup %q: %v", hostVethName, err)
		return
	}

	if err = netlink.LinkSetUp(hostVeth); err != nil {
		err = fmt.Errorf("failed to set %q up: %v", contVethName, err)
		return
	}

	if err = netlink.LinkSetNsFd(hostVeth, int(hostNS.Fd())); err != nil {
		err = fmt.Errorf("failed to move veth to host netns: %v", err)
		return
	}

	return
}

// SetupVeth sets up a virtual ethernet link.
// Should be in container netns.
// TODO(eyakubovich): get rid of entropy and ask kernel to pick name via pattern
func SetupVeth(entropy, contVethName string, mtu int, hostNS *os.File) (hostVeth, contVeth netlink.Link, err error) {
	// NetworkManager (recent versions) will ignore veth devices that start with "veth"
	hostVethName := RandomVethName(entropy)
	hostVeth, err = makeVeth(hostVethName, contVethName, mtu)
	if err != nil {
		err = fmt.Errorf("failed to make veth pair: %v", err)
		return
	}

	if err = netlink.LinkSetUp(hostVeth); err != nil {
		err = fmt.Errorf("failed to set %q up: %v", hostVethName, err)
		return
	}

	contVeth, err = netlink.LinkByName(contVethName)
	if err != nil {
		err = fmt.Errorf("failed to lookup %q: %v", contVethName, err)
		return
	}

	if err = netlink.LinkSetUp(contVeth); err != nil {
		err = fmt.Errorf("failed to set %q up: %v", contVethName, err)
		return
	}

	if err = netlink.LinkSetNsFd(hostVeth, int(hostNS.Fd())); err != nil {
		err = fmt.Errorf("failed to move veth to host netns: %v", err)
		return
	}

	return
}

// ConfigureIface takes the result of IPAM plugin and
// applies to the ifName interface
func ConfigureIface(ifName string, res *Result) error {
	link, err := netlink.LinkByName(ifName)
	if err != nil {
		return fmt.Errorf("failed to lookup %q: %v", ifName, err)
	}

	if err := netlink.LinkSetUp(link); err != nil {
		return fmt.Errorf("failed to set %q UP: %v", ifName, err)
	}

	// TODO(eyakubovich): IPv6
	addr := &netlink.Addr{IPNet: &res.IP4.IP, Label: ""}
	if err = netlink.AddrAdd(link, addr); err != nil {
		return fmt.Errorf("failed to add IP addr to %q: %v", ifName, err)
	}

	for _, r := range res.IP4.Routes {
		gw := r.GW
		if gw == nil {
			gw = res.IP4.Gateway
		}
		if err = ip.AddRoute(&r.Dst, gw, link); err != nil {
			// we skip over duplicate routes as we assume the first one wins
			if !os.IsExist(err) {
				return fmt.Errorf("failed to add route '%v via %v dev %v': %v", r.Dst, gw, ifName, err)
			}
		}
	}

	return nil
}

func ensureBridge(brName string, mtu int, ipn *net.IPNet) (*netlink.Bridge, error) {
	br := &netlink.Bridge{
		LinkAttrs: netlink.LinkAttrs{
			Name: brName,
			MTU:  mtu,
		},
	}

	if err := netlink.LinkAdd(br); err != nil {
		if err != syscall.EEXIST {
			return nil, fmt.Errorf("could not add %q: %v", brName, err)
		}

		// it's ok if the device already exists as long as config is similar
		br, err = bridgeByName(brName)
		if err != nil {
			return nil, err
		}
	}

	if err := netlink.LinkSetUp(br); err != nil {
		return nil, err
	}

	if ipn != nil {
		return br, ensureBridgeAddr(br, ipn)
	}

	return br, nil
}

func (l *DHCPLease) acquire() error {
	c, err := newDHCPClient(l.link)
	if err != nil {
		return err
	}
	defer c.Close()

	if (l.link.Attrs().Flags & net.FlagUp) != net.FlagUp {
		log.Printf("Link %q down. Attempting to set up", l.link.Attrs().Name)
		if err = netlink.LinkSetUp(l.link); err != nil {
			return err
		}
	}

	pkt, err := backoffRetry(func() (*dhcp4.Packet, error) {
		ok, ack, err := c.Request()
		switch {
		case err != nil:
			return nil, err
		case !ok:
			return nil, fmt.Errorf("DHCP server NACK'd own offer")
		default:
			return &ack, nil
		}
	})
	if err != nil {
		return err
	}

	return l.commit(pkt)
}

func loUp() error {
	lo, err := netlink.LinkByName("lo")
	if err != nil {
		return fmt.Errorf("failed to lookup lo: %v", err)
	}

	if err := netlink.LinkSetUp(lo); err != nil {
		return fmt.Errorf("failed to set lo up: %v", err)
	}

	return nil
}

// setupTapDevice creates persistent tap devices
// and returns a newly created netlink.Link structure
func setupTapDevice() (netlink.Link, error) {
	ifName, err := tuntap.CreatePersistentIface(tuntap.Tap)
	if err != nil {
		return nil, fmt.Errorf("tuntap persist %v", err)
	}
	link, err := netlink.LinkByName(ifName)
	if err != nil {
		return nil, fmt.Errorf("cannot find link %q: %v", ifName, err)
	}
	err = netlink.LinkSetUp(link)
	if err != nil {
		return nil, fmt.Errorf("cannot set link up %q: %v", ifName, err)
	}
	return link, nil
}

// setupTapDevice creates persistent tap devices
// and returns a newly created netlink.Link structure
func setupTapDevice(podID types.UUID) (netlink.Link, error) {
	// network device names are limited to 16 characters
	// the suffix %d will be replaced by the kernel with a suitable number
	nameTemplate := fmt.Sprintf("rkt-%s-tap%%d", podID.String()[0:4])
	ifName, err := tuntap.CreatePersistentIface(nameTemplate, tuntap.Tap)
	if err != nil {
		return nil, fmt.Errorf("tuntap persist %v", err)
	}
	link, err := netlink.LinkByName(ifName)
	if err != nil {
		return nil, fmt.Errorf("cannot find link %q: %v", ifName, err)
	}
	err = netlink.LinkSetUp(link)
	if err != nil {
		return nil, fmt.Errorf("cannot set link up %q: %v", ifName, err)
	}
	return link, nil
}