cilium-chain和物理网卡

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// pkg/option/config.go 
// AreDevicesRequired returns true if the agent needs to attach to the native
// devices to implement some features.
func (c *DaemonConfig) AreDevicesRequired() bool {
	return c.EnableNodePort || c.EnableHostFirewall || c.EnableBandwidthManager ||
		c.EnableWireguard || c.EnableHighScaleIPcache || c.EnableL2Announcements
}

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// pkg/datapath/loader/loader.go
// reloadHostDatapath (re)attaches BPF programs to:
// - native devices: ingress and (optionally) egress if certain features require it
func (l *Loader) reloadHostDatapath(ctx context.Context, ep datapath.Endpoint, objPath string) error {
    ...

	// Replace programs on physical devices.
	for _, device := range option.Config.GetDevices() {
		if _, err := netlink.LinkByName(device); err != nil {
			log.WithError(err).WithField("device", device).Warn("Link does not exist")
			continue
		}

		netdevObjPath := path.Join(ep.StateDir(), hostEndpointNetdevPrefix+device+".o")
		if err := patchHostNetdevDatapath(ep, objPath, netdevObjPath, device,
			node.GetMasqIPv4AddrsWithDevices(), node.GetMasqIPv6AddrsWithDevices()); err != nil {
			return err
		}

		progs := []progDefinition{
			{progName: symbolFromHostNetdevEp, direction: dirIngress},
		}

		// 这里就是上面提到的，如果不开启某些特性，宿主机网卡是不会加载eBPF程序的
		if option.Config.AreDevicesRequired() &&
			// Attaching bpf_host to cilium_wg0 is required for encrypting KPR
			// traffic. Only ingress prog (aka "from-netdev") is needed to handle
			// the rev-NAT xlations.
			device != wgTypes.IfaceName {

			progs = append(progs, progDefinition{symbolToHostNetdevEp, dirEgress})
		} else {
			// Remove any previously attached device from egress path if BPF
			// NodePort and host firewall are disabled.
			err := RemoveTCFilters(device, netlink.HANDLE_MIN_EGRESS)
			if err != nil {
				log.WithField("device", device).Error(err)
			}
		}

		// replaceDatapath本质上是调用tc在宿主机上进行eBPF的程序的加载和卸载
		finalize, err := replaceDatapath(ctx, device, netdevObjPath, progs, "")
		if err != nil {
			scopedLog := ep.Logger(Subsystem).WithFields(logrus.Fields{
				logfields.Path: objPath,
				logfields.Veth: device,
			})
			if ctx.Err() == nil {
				scopedLog.WithError(err).Warningf("JoinEP: Failed to load program for physical device %s", device)
			}
			return err
		}
		defer finalize()
	}

	return nil
}

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kube-proxy-replacement: partial
enable-node-port: "false"
enable-host-firewall: "false"

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apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
  name: "l4-rule"
spec:
  endpointSelector:
    matchLabels:
      app: network-multitool
  ingress:
  - fromEndpoints:
    - matchLabels:
        app: network-multitool
    toPorts:
    - ports:
      - port: "80"
        protocol: TCP