/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

// Copyright 2015 CNI authors
// Copied from https://github.com/containernetworking/plugins/blob/9f1bf2a84828d2c16ea5912b53c0b6048bd00e7a/plugins/main/host-device/host-device.go on 2024-05-23

package main

import (
	"fmt"
	"net"

	"github.com/containernetworking/plugins/pkg/ns"
	"github.com/vishvananda/netlink"
)

// setTempName sets a temporary name for netdevice to avoid collisions with interfaces names.
func setTempName(dev netlink.Link) (netlink.Link, error) {
	tempName := fmt.Sprintf("%s%d", "temp_", dev.Attrs().Index)

	// rename to tempName
	if err := netlink.LinkSetName(dev, tempName); err != nil {
		return nil, fmt.Errorf("failed to rename device %q to %q: %v", dev.Attrs().Name, tempName, err)
	}

	// Get updated Link obj
	tempDev, err := netlink.LinkByName(tempName)
	if err != nil {
		return nil, fmt.Errorf("failed to find %q after rename to %q: %v", dev.Attrs().Name, tempName, err)
	}

	return tempDev, nil
}

func moveLinkIn(hostDev netlink.Link, containerNs ns.NetNS, ifName string) (netlink.Link, error) {
	origLinkFlags := hostDev.Attrs().Flags
	hostDevName := hostDev.Attrs().Name
	defaultNs, err := ns.GetCurrentNS()
	if err != nil {
		return nil, fmt.Errorf("failed to get host namespace: %v", err)
	}

	// Devices can be renamed only when down
	if err = netlink.LinkSetDown(hostDev); err != nil {
		return nil, fmt.Errorf("failed to set %q down: %v", hostDev.Attrs().Name, err)
	}

	// restore original link state in case of error
	defer func() {
		if err != nil {
			if origLinkFlags&net.FlagUp == net.FlagUp && hostDev != nil {
				_ = netlink.LinkSetUp(hostDev)
			}
		}
	}()

	hostDev, err = setTempName(hostDev)
	if err != nil {
		return nil, fmt.Errorf("failed to rename device %q to temporary name: %v", hostDevName, err)
	}

	// restore original netdev name in case of error
	defer func() {
		if err != nil && hostDev != nil {
			_ = netlink.LinkSetName(hostDev, hostDevName)
		}
	}()

	if err = netlink.LinkSetNsFd(hostDev, int(containerNs.Fd())); err != nil {
		return nil, fmt.Errorf("failed to move %q to container ns: %v", hostDev.Attrs().Name, err)
	}

	var contDev netlink.Link
	tempDevName := hostDev.Attrs().Name
	if err = containerNs.Do(func(_ ns.NetNS) error {
		var err error
		contDev, err = netlink.LinkByName(tempDevName)
		if err != nil {
			return fmt.Errorf("failed to find %q: %v", tempDevName, err)
		}

		// move netdev back to host namespace in case of error
		defer func() {
			if err != nil {
				_ = netlink.LinkSetNsFd(contDev, int(defaultNs.Fd()))
				// we need to get updated link object as link was moved back to host namespace
				_ = defaultNs.Do(func(_ ns.NetNS) error {
					hostDev, _ = netlink.LinkByName(tempDevName)
					return nil
				})
			}
		}()

		// Save host device name into the container device's alias property
		if err = netlink.LinkSetAlias(contDev, hostDevName); err != nil {
			return fmt.Errorf("failed to set alias to %q: %v", tempDevName, err)
		}
		// Rename container device to respect args.IfName
		if err = netlink.LinkSetName(contDev, ifName); err != nil {
			return fmt.Errorf("failed to rename device %q to %q: %v", tempDevName, ifName, err)
		}

		// restore tempDevName in case of error
		defer func() {
			if err != nil {
				_ = netlink.LinkSetName(contDev, tempDevName)
			}
		}()

		// Bring container device up
		if err = netlink.LinkSetUp(contDev); err != nil {
			return fmt.Errorf("failed to set %q up: %v", ifName, err)
		}

		// bring device down in case of error
		defer func() {
			if err != nil {
				_ = netlink.LinkSetDown(contDev)
			}
		}()

		// Retrieve link again to get up-to-date name and attributes
		contDev, err = netlink.LinkByName(ifName)
		if err != nil {
			return fmt.Errorf("failed to find %q: %v", ifName, err)
		}
		return nil
	}); err != nil {
		return nil, err
	}

	return contDev, nil
}

func moveLinkOut(containerNs ns.NetNS, ifName string) error {
	defaultNs, err := ns.GetCurrentNS()
	if err != nil {
		return err
	}
	defer defaultNs.Close()

	var tempName string
	var origDev netlink.Link
	err = containerNs.Do(func(_ ns.NetNS) error {
		dev, err := netlink.LinkByName(ifName)
		if err != nil {
			return fmt.Errorf("failed to find %q: %v", ifName, err)
		}
		origDev = dev

		// Devices can be renamed only when down
		if err = netlink.LinkSetDown(dev); err != nil {
			return fmt.Errorf("failed to set %q down: %v", ifName, err)
		}

		defer func() {
			// If moving the device to the host namespace fails, set its name back to ifName so that this
			// function can be retried. Also bring the device back up, unless it was already down before.
			if err != nil {
				_ = netlink.LinkSetName(dev, ifName)
				if dev.Attrs().Flags&net.FlagUp == net.FlagUp {
					_ = netlink.LinkSetUp(dev)
				}
			}
		}()

		newLink, err := setTempName(dev)
		if err != nil {
			return fmt.Errorf("failed to rename device %q to temporary name: %v", ifName, err)
		}
		dev = newLink
		tempName = dev.Attrs().Name

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

	if err != nil {
		return err
	}

	// Rename the device to its original name from the host namespace
	tempDev, err := netlink.LinkByName(tempName)
	if err != nil {
		return fmt.Errorf("failed to find %q in host namespace: %v", tempName, err)
	}

	if err = netlink.LinkSetName(tempDev, tempDev.Attrs().Alias); err != nil {
		// move device back to container ns so it may be retired
		defer func() {
			_ = netlink.LinkSetNsFd(tempDev, int(containerNs.Fd()))
			_ = containerNs.Do(func(_ ns.NetNS) error {
				lnk, err := netlink.LinkByName(tempName)
				if err != nil {
					return err
				}
				_ = netlink.LinkSetName(lnk, ifName)
				if origDev.Attrs().Flags&net.FlagUp == net.FlagUp {
					_ = netlink.LinkSetUp(lnk)
				}
				return nil
			})
		}()
		return fmt.Errorf("failed to restore %q to original name %q: %v", tempName, tempDev.Attrs().Alias, err)
	}

	return nil
}