bridge_network.go

package main

import (
	"errors"
	"fmt"

	"github.com/vishvananda/netlink"
)

const managedTapName = "tap0"

// managedTap identifies the exact TAP created by this process. The identity
// check in cleanup prevents a later interface reusing the name or index from
// being removed accidentally.
type managedTap struct {
	name    string
	index   int
	created bool

	lookupLink func(string) (netlink.Link, error)
	deleteLink func(netlink.Link) error
}

func (tap *managedTap) cleanup() error {
	if tap == nil || !tap.created {
		return nil
	}

	lookup := tap.lookupLink
	if lookup == nil {
		lookup = netlink.LinkByName
	}
	link, err := lookup(tap.name)
	if err != nil {
		var notFound netlink.LinkNotFoundError
		if errors.As(err, &notFound) {
			tap.created = false
			return nil
		}
		return fmt.Errorf("look up managed TAP %q for cleanup: %w", tap.name, err)
	}
	if link == nil || link.Attrs() == nil {
		return fmt.Errorf("managed TAP %q lookup returned no link", tap.name)
	}
	if link.Type() != "tuntap" {
		return fmt.Errorf("refusing to delete managed TAP %q: current link type is %q", tap.name, link.Type())
	}
	if link.Attrs().Index != tap.index {
		return fmt.Errorf("refusing to delete managed TAP %q: link index changed from %d to %d", tap.name, tap.index, link.Attrs().Index)
	}

	deleteLink := tap.deleteLink
	if deleteLink == nil {
		deleteLink = netlink.LinkDel
	}
	if err := deleteLink(link); err != nil {
		var notFound netlink.LinkNotFoundError
		if errors.As(err, &notFound) {
			tap.created = false
			return nil
		}
		return fmt.Errorf("delete managed TAP %q: %w", tap.name, err)
	}
	tap.created = false
	return nil
}