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devices.go
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devices.go
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// SPDX-License-Identifier: Apache-2.0
// Copyright Authors of Cilium
// This module implements Cilium's network device detection.
package linux
import (
"context"
"fmt"
"net"
"sort"
"strings"
"github.com/vishvananda/netlink"
"github.com/vishvananda/netns"
"golang.org/x/sys/unix"
"github.com/cilium/cilium/pkg/datapath/linux/probes"
"github.com/cilium/cilium/pkg/k8s"
"github.com/cilium/cilium/pkg/lock"
"github.com/cilium/cilium/pkg/logging/logfields"
"github.com/cilium/cilium/pkg/mac"
"github.com/cilium/cilium/pkg/node"
"github.com/cilium/cilium/pkg/option"
)
var (
excludedDevicePrefixes = []string{
"cilium_",
"lo",
"lxc",
"cni",
"docker",
}
// Route filter to look at all routing tables.
routeFilter = netlink.Route{
Table: unix.RT_TABLE_UNSPEC,
}
routeFilterMask = netlink.RT_FILTER_TABLE
)
type DeviceManager struct {
lock.Mutex
devices map[string]struct{}
filter deviceFilter
handle *netlink.Handle
netns netns.NsHandle
}
func NewDeviceManager() (*DeviceManager, error) {
return NewDeviceManagerAt(netns.None())
}
func NewDeviceManagerAt(netns netns.NsHandle) (*DeviceManager, error) {
handle, err := netlink.NewHandleAt(netns)
if err != nil {
return nil, err
}
return &DeviceManager{
devices: make(map[string]struct{}),
filter: deviceFilter(option.Config.GetDevices()),
handle: handle,
netns: netns,
}, err
}
// Detect tries to detect devices to which BPF programs may be loaded.
// See AreDevicesRequired() for features that require the device information.
//
// The devices are detected by looking at all the configured global unicast
// routes in the system.
func (dm *DeviceManager) Detect() ([]string, error) {
dm.Lock()
defer dm.Unlock()
dm.devices = make(map[string]struct{})
if err := dm.expandDevices(); err != nil {
return nil, err
}
if err := dm.expandDirectRoutingDevice(); err != nil {
return nil, err
}
l3DevOK := true
if !option.Config.EnableHostLegacyRouting {
// Probe whether BPF host routing is supported for L3 devices. This will
// invoke bpftool and requires root privileges, so we're only probing
// when necessary.
l3DevOK = supportL3Dev()
}
if len(option.Config.GetDevices()) == 0 && dm.AreDevicesRequired() {
// Detect the devices from the system routing table by finding the devices
// which have global unicast routes.
family := netlink.FAMILY_ALL
if option.Config.EnableIPv4 && !option.Config.EnableIPv6 {
family = netlink.FAMILY_V4
} else if !option.Config.EnableIPv4 && option.Config.EnableIPv6 {
family = netlink.FAMILY_V6
}
routes, err := dm.handle.RouteListFiltered(family, &routeFilter, routeFilterMask)
if err != nil {
return nil, fmt.Errorf("cannot retrieve routes for device detection: %w", err)
}
dm.updateDevicesFromRoutes(l3DevOK, routes)
} else {
for _, dev := range option.Config.GetDevices() {
dm.devices[dev] = struct{}{}
}
}
detectDirectRoutingDev := option.Config.DirectRoutingDeviceRequired()
if option.Config.DirectRoutingDeviceRequired() && option.Config.DirectRoutingDevice != "" {
dm.devices[option.Config.DirectRoutingDevice] = struct{}{}
detectDirectRoutingDev = false
}
detectIPv6MCastDev := option.Config.EnableIPv6NDP
if option.Config.IPv6MCastDevice != "" {
dm.devices[option.Config.IPv6MCastDevice] = struct{}{}
detectIPv6MCastDev = false
}
if detectDirectRoutingDev || detectIPv6MCastDev {
k8sNodeDev := ""
k8sNodeLink, err := findK8SNodeIPLink()
if err == nil {
k8sNodeDev = k8sNodeLink.Attrs().Name
dm.devices[k8sNodeDev] = struct{}{}
} else if k8s.IsEnabled() {
return nil, fmt.Errorf("k8s is enabled, but still failed to find node IP: %w", err)
}
if detectDirectRoutingDev {
// If only one device found, use that one. Otherwise use the device with k8s node IP.
if len(dm.devices) == 1 {
for dev := range dm.devices {
option.Config.DirectRoutingDevice = dev
break
}
} else if k8sNodeDev != "" {
option.Config.DirectRoutingDevice = k8sNodeDev
} else {
return nil, fmt.Errorf("unable to determine direct routing device. Use --%s to specify it",
option.DirectRoutingDevice)
}
log.WithField(option.DirectRoutingDevice, option.Config.DirectRoutingDevice).
Info("Direct routing device detected")
}
if detectIPv6MCastDev {
if k8sNodeLink != nil && k8sNodeLink.Attrs().Flags&net.FlagMulticast != 0 {
option.Config.IPv6MCastDevice = k8sNodeDev
log.WithField(option.IPv6MCastDevice, option.Config.IPv6MCastDevice).Info("IPv6 multicast device detected")
} else {
return nil, fmt.Errorf("unable to determine Multicast device. Use --%s to specify it",
option.IPv6MCastDevice)
}
}
}
deviceList := dm.getDeviceList()
option.Config.SetDevices(deviceList)
log.WithField(logfields.Devices, deviceList).Info("Detected devices")
return deviceList, nil
}
func (dm *DeviceManager) getDeviceList() []string {
devs := make([]string, 0, len(dm.devices))
for dev := range dm.devices {
devs = append(devs, dev)
}
sort.Strings(devs)
return devs
}
// Exclude devices that have one or more of these flags set.
var excludedIfFlagsMask uint32 = unix.IFF_SLAVE | unix.IFF_LOOPBACK
// isViableDevice returns true if the given link is usable and Cilium should attach
// programs to it.
func (dm *DeviceManager) isViableDevice(l3DevOK, hasDefaultRoute bool, link netlink.Link) bool {
name := link.Attrs().Name
// Do not consider any of the excluded devices.
for _, p := range excludedDevicePrefixes {
if strings.HasPrefix(name, p) {
log.WithField(logfields.Device, name).
Debugf("Skipping device as it has excluded prefix '%s'", p)
return false
}
}
// Skip devices that have an excluded interface flag set.
if link.Attrs().RawFlags&excludedIfFlagsMask != 0 {
log.WithField(logfields.Device, name).Debugf("Skipping device as it has excluded flag (%x)", link.Attrs().RawFlags)
return false
}
// Ignore L3 devices if we cannot support them.
if !l3DevOK && !mac.LinkHasMacAddr(link) {
log.WithField(logfields.Device, name).
Info("Ignoring L3 device; >= 5.8 kernel is required.")
return false
}
// If user specified devices or wildcards, then skip the device if it doesn't match.
if !dm.filter.match(name) {
return false
}
switch link.Type() {
case "veth":
// Skip veth devices that don't have a default route.
// This is a workaround for kubernetes-in-docker. We want to avoid
// veth devices in general as they may be leftovers from another CNI.
if !hasDefaultRoute {
log.WithField(logfields.Device, name).
Debug("Ignoring veth device as it has no default route")
return false
}
case "bridge", "openvswitch":
// Skip bridge devices as they're very unlikely to be used for K8s
// purposes. In the rare cases where a user wants to load datapath
// programs onto them they can override device detection with --devices.
log.WithField(logfields.Device, name).Debug("Ignoring bridge-like device")
return false
}
if link.Attrs().MasterIndex > 0 {
if master, err := dm.handle.LinkByIndex(link.Attrs().MasterIndex); err == nil {
switch master.Type() {
case "bridge", "openvswitch":
log.WithField(logfields.Device, name).Debug("Ignoring device attached to bridge")
return false
case "bond", "team":
log.WithField(logfields.Device, name).Debug("Ignoring bonded device")
return false
}
}
}
return true
}
type linkInfo struct {
hasDefaultRoute bool
}
// updateDevicesFromRoutes processes a batch of routes and updates the set of
// devices. Returns true if devices changed.
func (dm *DeviceManager) updateDevicesFromRoutes(l3DevOK bool, routes []netlink.Route) bool {
linkInfos := make(map[int]linkInfo)
// Collect all link indices mentioned in the route update batch
for _, route := range routes {
// Only consider devices that have global unicast routes,
// e.g. skip loopback, multicast and link local routes.
if route.Dst != nil && !route.Dst.IP.IsGlobalUnicast() {
continue
}
if route.Table == unix.RT_TABLE_LOCAL {
continue
}
linkInfo := linkInfos[route.LinkIndex]
linkInfo.hasDefaultRoute = linkInfo.hasDefaultRoute || route.Dst == nil
linkInfos[route.LinkIndex] = linkInfo
}
changed := false
for index, info := range linkInfos {
link, err := dm.handle.LinkByIndex(index)
if err != nil {
log.WithError(err).WithField(logfields.LinkIndex, index).
Warn("Failed to get link by index")
continue
}
name := link.Attrs().Name
// Skip devices we already know.
if _, exists := dm.devices[name]; exists {
continue
}
viable := dm.isViableDevice(l3DevOK, info.hasDefaultRoute, link)
if viable {
dm.devices[name] = struct{}{}
changed = true
} else {
log.WithField(logfields.Device, name).Debug("Skipping unviable device")
}
}
return changed
}
// Listen starts listening to changes to network devices. When devices change the new set
// of devices is sent on the returned channel.
func (dm *DeviceManager) Listen(ctx context.Context) (chan []string, error) {
l3DevOK := supportL3Dev()
routeChan := make(chan netlink.RouteUpdate)
closeChan := make(chan struct{})
err := netlink.RouteSubscribeWithOptions(routeChan, closeChan,
netlink.RouteSubscribeOptions{
// List existing routes to make sure we did not miss changes that happened after Detect().
ListExisting: true,
Namespace: &dm.netns,
})
if err != nil {
return nil, err
}
linkChan := make(chan netlink.LinkUpdate)
err = netlink.LinkSubscribeWithOptions(linkChan, closeChan, netlink.LinkSubscribeOptions{
ListExisting: false,
Namespace: &dm.netns,
})
if err != nil {
return nil, err
}
devicesChan := make(chan []string, 1)
// Find links deleted after Detect()
if allLinks, err := dm.handle.LinkList(); err == nil {
changed := false
linksByName := map[string]struct{}{}
for _, link := range allLinks {
linksByName[link.Attrs().Name] = struct{}{}
}
dm.Lock()
for name := range dm.devices {
if _, exists := linksByName[name]; !exists {
delete(dm.devices, name)
changed = true
}
}
devices := dm.getDeviceList()
dm.Unlock()
if changed {
log.WithField(logfields.Devices, devices).Info("Devices changed")
devicesChan <- devices
}
}
go func() {
log.Info("Listening for device changes")
for {
devicesChanged := false
var devices []string
select {
case <-ctx.Done():
log.Debug("context closed, Listen() stopping")
close(closeChan)
close(devicesChan)
// drain the route and link channels
for range routeChan {
}
for range linkChan {
}
return
case update := <-routeChan:
if update.Type == unix.RTM_NEWROUTE {
dm.Lock()
devicesChanged = dm.updateDevicesFromRoutes(l3DevOK, []netlink.Route{update.Route})
devices = dm.getDeviceList()
dm.Unlock()
}
case update := <-linkChan:
if update.Header.Type == unix.RTM_DELLINK {
name := update.Attrs().Name
dm.Lock()
if _, ok := dm.devices[name]; ok {
delete(dm.devices, name)
devicesChanged = true
}
devices = dm.getDeviceList()
dm.Unlock()
}
}
if devicesChanged {
log.WithField(logfields.Devices, devices).Info("Devices changed")
devicesChan <- devices
}
}
}()
return devicesChan, nil
}
func (dm *DeviceManager) AreDevicesRequired() bool {
return option.Config.EnableNodePort ||
option.Config.EnableHostFirewall ||
option.Config.EnableBandwidthManager
}
// expandDevices expands all wildcard device names to concrete devices.
// e.g. device "eth+" expands to "eth0,eth1" etc. Non-matching wildcards are ignored.
func (dm *DeviceManager) expandDevices() error {
expandedDevices, err := dm.expandDeviceWildcards(option.Config.GetDevices(), option.Devices)
if err != nil {
return err
}
option.Config.SetDevices(expandedDevices)
return nil
}
// expandDirectRoutingDevice expands all wildcard device names to concrete devices and picks a first one.
func (dm *DeviceManager) expandDirectRoutingDevice() error {
if option.Config.DirectRoutingDevice == "" {
return nil
}
expandedDevices, err := dm.expandDeviceWildcards([]string{option.Config.DirectRoutingDevice}, option.DirectRoutingDevice)
if err != nil {
return err
}
option.Config.DirectRoutingDevice = expandedDevices[0]
return nil
}
func (dm *DeviceManager) expandDeviceWildcards(devices []string, option string) ([]string, error) {
allLinks, err := dm.handle.LinkList()
if err != nil {
return nil, fmt.Errorf("device wildcard expansion failed to fetch devices: %w", err)
}
expandedDevicesMap := make(map[string]struct{})
for _, iface := range devices {
if strings.HasSuffix(iface, "+") {
prefix := strings.TrimRight(iface, "+")
for _, link := range allLinks {
attrs := link.Attrs()
if strings.HasPrefix(attrs.Name, prefix) {
expandedDevicesMap[attrs.Name] = struct{}{}
}
}
} else {
expandedDevicesMap[iface] = struct{}{}
}
}
if len(devices) > 0 && len(expandedDevicesMap) == 0 {
// User defined devices, but expansion yielded no devices. Fail here to not
// surprise with auto-detection.
return nil, fmt.Errorf("device wildcard expansion failed to detect devices. Please verify --%s option.",
option)
}
expandedDevices := make([]string, 0, len(expandedDevicesMap))
for dev := range expandedDevicesMap {
expandedDevices = append(expandedDevices, dev)
}
sort.Strings(expandedDevices)
return expandedDevices, nil
}
func findK8SNodeIPLink() (netlink.Link, error) {
nodeIP := node.GetK8sNodeIP()
if nodeIP == nil {
return nil, fmt.Errorf("failed to find K8s node device as node IP is not known")
}
var family int
if nodeIP.To4() != nil {
family = netlink.FAMILY_V4
} else {
family = netlink.FAMILY_V6
}
if addrs, err := netlink.AddrList(nil, family); err == nil {
for _, a := range addrs {
if a.IP.Equal(nodeIP) {
link, err := netlink.LinkByIndex(a.LinkIndex)
if err != nil {
return nil, err
}
return link, nil
}
}
}
return nil, fmt.Errorf("K8s node device not found")
}
// supportL3Dev returns true if the kernel is new enough to support BPF host routing of
// packets coming from L3 devices using bpf_skb_redirect_peer.
func supportL3Dev() bool {
probesManager := probes.NewProbeManager()
if h := probesManager.GetHelpers("sched_cls"); h != nil {
_, found := h["bpf_skb_change_head"]
return found
}
return false
}
type deviceFilter []string
func (lst deviceFilter) match(dev string) bool {
if len(lst) == 0 {
return true
}
for _, entry := range lst {
if strings.HasSuffix(entry, "+") {
prefix := strings.TrimRight(entry, "+")
return strings.HasPrefix(dev, prefix)
} else if dev == entry {
return true
}
}
return false
}