文章目录

Multus 概述
Multus 使用
- Multus DaemonSet 的作用
- Multus 的使用
- Multus 的处理
- - 1. 从 input 加载 netConf, 将 cni 配置加载到 netConf.Delegates
  - 2. 加载委托插件（delegate）并将其添加至 multus 配置
  - - 2.1. 尝试解析 Pod 注解中 multus 配置
    - 2.2. 获取指定的 Network-attachment-definition
  - 3. 加载 delegate 后

Multus 概述

Kubernetes 的 POD 默认不支持多网卡设置，我们通过 Multus CNI 来为 Pod 建立多网络接口。

Multus 使用

Multus 安装很简单

$ git clone https://github.com/intel/multus-cni.git && cd multus-cni
$ cat ./images/multus-daemonset.yml | kubectl apply -f -

Multus DaemonSet 的作用

启动一个 Multus 守护程序集，这会在每个节点上运行一个 pod，它在每个节点上放置一个 Multus 二进制文件/opt/cni/bin
读取按字典顺序（按字母顺序）的第一个配置文件/etc/cni/net.d，并在每个节点上为 Multus 创建一个新的配置文件/etc/cni/net.d/00-multus.conf，此配置是自动生成的，并且基于默认网络配置（假定为按字母顺序排列的第一个配置）
在每个节点上创建一个/etc/cni/net.d/multus.d目录，其中包含 Multus 访问 Kubernetes API 的身份验证信息。
安装 network-attachment-definition CRD，这个 CRD 存储着其他 CNI 的信息，在 Multus 看到使用此资源时，会调用设置的 CNI 去配置网络。

其中第二点，安装 Multus 会将原有的 CNI 作为代理的一部分放到自己的 CNI 配置中，当 work 时，也会使用之前的 CNI 创建第一张网卡。
如图:
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-qlPG0OVy-1670220998992)(/img/multus.png)]

配置变化, 可以看到原有的 CNI 配置完全存在于 Multus 的 delegates 里，通过配置变化，containerd 调用 CNI 时实际调用的是 Multus 的 CNI。

/etc/cni/net.d/01-kube-ovn.conflist 
{
    "name":"kube-ovn",
    "cniVersion":"0.3.1",
    "plugins":[
        {
            "type":"kube-ovn",
            "server_socket":"/run/openvswitch/kube-ovn-daemon.sock"
        },
        {
            "type":"portmap",
            "capabilities":{
                "portMappings":true
            }
        }
    ]
}

cat /etc/cni/net.d/00-multus.conf | jq
{
  "capabilities": {
    "portMappings": true
  },
  "cniVersion": "0.3.1",
  "delegates": [
    {
      "cniVersion": "0.3.1",
      "name": "kube-ovn",
      "plugins": [
        {
          "server_socket": "/run/openvswitch/kube-ovn-daemon.sock",
          "type": "kube-ovn"
        },
        {
          "capabilities": {
            "portMappings": true
          },
          "type": "portmap"
        }
      ]
    }
  ],
  "logLevel": "debug",
  "logToStderr": true,
  "kubeconfig": "/etc/cni/net.d/multus.d/multus.kubeconfig",
  "name": "multus-cni-network",
  "type": "multus"
}

Multus 的使用

希望两个网卡都使用 kube-ovn 为 pod 创建
Network-Attachment-Definition 创建

apiVersion: v1
kind: Namespace
metadata:
  name: mec-nets
---
apiVersion: "k8s.cni.cncf.io/v1"
kind: NetworkAttachmentDefinition
metadata:
  name: attachnet1
  namespace: mec-nets
spec:
  config: '{
      "cniVersion": "0.3.0",
      "type": "kube-ovn",
      "server_socket": "/run/openvswitch/kube-ovn-daemon.sock",
      "provider": "attachnet1.mec-nets.ovn"
    }

创建 Pod

apiVersion: v1
kind: Pod
metadata:
  name: pod9
  annotations:
    ovn.kubernetes.io/logical_switch: subnet-ipv4-ns-demo-100
    k8s.v1.cni.cncf.io/networks: mec-nets/attachnet1   # 选择 NetworkAttachmentDefinition
    attachnet1.mec-nets.ovn.kubernetes.io/logical_switch: subnet-ipv4-ns-demo-100
spec:
  containers:
  - name: pod9
    command: ["/bin/ash", "-c", "trap : TERM INT; sleep 36000 & wait"]
    image: rancher/curl
  nodeSelector:
    kubernetes.io/hostname: eci2

Multus 的处理

符合 CNI 的标准规范，在 containerd 调用 plugin (multus 二进制) 后，multus 进行处理

pkg/multus/miltus.go L557

func CmdAdd(args *skel.CmdArgs, exec invoke.Exec, kubeClient *k8s.ClientInfo) (cnitypes.Result, error) {
    n, err := types.LoadNetConf(args.StdinData)
}

1. 从 input 加载 netConf, 将 cni 配置加载到 netConf.Delegates

n, err := types.LoadNetConf(args.StdinData)

2. 加载委托插件（delegate）并将其添加至 multus 配置

	_, kc, err := k8s.TryLoadPodDelegates(pod, n, kubeClient, resourceMap)
	if err != nil {
		return nil, cmdErr(k8sArgs, "error loading k8s delegates k8s args: %v", err)
	}

2.1. 尝试解析 Pod 注解中 multus 配置

v1.multus-cni.io/default-network
是否携带 v1.multus-cni.io/default-network 键值对
pkg/k8sclient/k8sclient.go L323

func TryLoadPodDelegates(pod *v1.Pod, conf *types.NetConf, clientInfo *ClientInfo, resourceMap map[string]*types.ResourceInfo) (int, *ClientInfo, error) {
	var err error
    ......
    delegate, err := tryLoadK8sPodDefaultNetwork(clientInfo, pod, conf)
	if err != nil {
		return 0, nil, logging.Errorf("TryLoadPodDelegates: error in loading K8s cluster default network from pod annotation: %v", err)
	}
	if delegate != nil {
		logging.Debugf("TryLoadPodDelegates: Overwrite the cluster default network with %v from pod annotations", delegate)

		conf.Delegates[0] = delegate
	}

k8s.v1.cni.cncf.io/networks
是否携带 k8s.v1.cni.cncf.io/networks 键值对, 可以看到该配置可以多个。

	networks, err := GetPodNetwork(pod)

parsePodNetworkAnnotation 拆解 k8s.v1.cni.cncf.io/networks 对应的值用于初始化 types.NetworkSelectionElement 并追加至切片：

func GetPodNetwork(pod *v1.Pod) ([]*types.NetworkSelectionElement, error) {
	logging.Debugf("GetPodNetwork: %v", pod)

	netAnnot := pod.Annotations[networkAttachmentAnnot]
	defaultNamespace := pod.ObjectMeta.Namespace

	if len(netAnnot) == 0 {
		return nil, &NoK8sNetworkError{"no kubernetes network found"}
	}

	networks, err := parsePodNetworkAnnotation(netAnnot, defaultNamespace)
	if err != nil {
		return nil, err
	}
	return networks, nil
}

像上面示例 pod9 中 mec-nets/attachnet1, network 的 Name 是 attachnet1, Namespace 是 mec-nets, InterfaceRequest 可以命名网卡名称, 如果要 eth10 则命名为 mec-nets/attachnet1@eth10

2.2. 获取指定的 Network-attachment-definition

	if networks != nil {
		delegates, err := GetNetworkDelegates(clientInfo, pod, networks, conf, resourceMap)

		if err != nil {
			if _, ok := err.(*NoK8sNetworkError); ok {
				return 0, clientInfo, nil
			}
			return 0, nil, logging.Errorf("TryLoadPodDelegates: error in getting k8s network for pod: %v", err)
		}

		if err = conf.AddDelegates(delegates); err != nil {
			return 0, nil, err
		}

		return len(delegates), clientInfo, err
	}

getKubernetesDelegate
pkg/k8sclient/k8sclient.go L254

func getKubernetesDelegate(client *ClientInfo, net *types.NetworkSelectionElement, confdir string, pod *v1.Pod, resourceMap map[string]*types.ResourceInfo) (*types.DelegateNetConf, map[string]*types.ResourceInfo, error) {

	logging.Debugf("getKubernetesDelegate: %v, %v, %s, %v, %v", client, net, confdir, pod, resourceMap)
	customResource, err := client.NetClient.NetworkAttachmentDefinitions(net.Namespace).Get(context.TODO(), net.Name, metav1.GetOptions{})
	if err != nil {
		errMsg := fmt.Sprintf("cannot find a network-attachment-definition (%s) in namespace (%s): %v", net.Name, net.Namespace, err)
		if client != nil {
			client.Eventf(pod, v1.EventTypeWarning, "NoNetworkFound", errMsg)
		}
		return nil, resourceMap, logging.Errorf("getKubernetesDelegate: " + errMsg)
	}
......
	configBytes, err := netutils.GetCNIConfig(customResource, confdir)
	if err != nil {
		return nil, resourceMap, err
	}

	delegate, err := types.LoadDelegateNetConf(configBytes, net, deviceID, resourceName)
	if err != nil {
		return nil, resourceMap, err
	}

	return delegate, resourceMap, nil
}

解析后得到 NetworkAttachmentDefinition 的 spec 字段中的配置字符串：

{ 
    "cniVersion": "0.3.0", 
    "type": "kube-ovn", 
    "server_socket": "/run/openvswitch/kube-ovn-daemon.sock",
    "provider": "attachnet1.mec-nets.ovn" 
}

使用该 NAD 的 CNI delegate 使用 kube-ovn CNI。

3. 加载 delegate 后

在补充完配置结构体后，遍历它的 Delegates 字段：
/pkg/multus/multus.go L612

	var result, tmpResult cnitypes.Result
	var netStatus []nettypes.NetworkStatus
	for idx, delegate := range n.Delegates {
		ifName := getIfname(delegate, args.IfName, idx)

3.1 获取网卡名称
如果 attachnet1/mec-nets@eth10 这种已配置的，会根据索引 + net 确定网卡名

func getIfname(delegate *types.DelegateNetConf, argif string, idx int) string {
	logging.Debugf("getIfname: %v, %s, %d", delegate, argif, idx)
	if delegate.IfnameRequest != "" {
		return delegate.IfnameRequest
	}
	if delegate.MasterPlugin {
		// master plugin always uses the CNI-provided interface name
		return argif
	}

	// Otherwise construct a unique interface name from the delegate's
	// position in the delegate list
	return fmt.Sprintf("net%d", idx)
}

3.2 使用 DelegateAdd 为 pod 配置网络

	if delegate.ConfListPlugin {
		result, err = conflistAdd(rt, delegate.Bytes, multusNetconf, exec)
		if err != nil {
			return nil, err
		}
	} else {
		result, err = confAdd(rt, delegate.Bytes, multusNetconf, exec)
		if err != nil {
			return nil, err
		}
	}

func conflistAdd(rt *libcni.RuntimeConf, rawnetconflist []byte, multusNetconf *types.NetConf, exec invoke.Exec) (cnitypes.Result, error) {
	logging.Debugf("conflistAdd: %v, %s", rt, string(rawnetconflist))
	// In part, adapted from K8s pkg/kubelet/dockershim/network/cni/cni.go
	binDirs := filepath.SplitList(os.Getenv("CNI_PATH"))
	binDirs = append([]string{multusNetconf.BinDir}, binDirs...)
	cniNet := libcni.NewCNIConfigWithCacheDir(binDirs, multusNetconf.CNIDir, exec)

	confList, err := libcni.ConfListFromBytes(rawnetconflist)
	if err != nil {
		return nil, logging.Errorf("conflistAdd: error converting the raw bytes into a conflist: %v", err)
	}

	result, err := cniNet.AddNetworkList(context.Background(), confList, rt)
	if err != nil {
		return nil, err
	}

	return result, nil
}

func conflistAdd(rt *libcni.RuntimeConf, rawnetconflist []byte, multusNetconf *types.NetConf, exec invoke.Exec) (cnitypes.Result, error) {
	logging.Debugf("conflistAdd: %v, %s", rt, string(rawnetconflist))
	// In part, adapted from K8s pkg/kubelet/dockershim/network/cni/cni.go
	binDirs := filepath.SplitList(os.Getenv("CNI_PATH"))
	binDirs = append([]string{multusNetconf.BinDir}, binDirs...)
	cniNet := libcni.NewCNIConfigWithCacheDir(binDirs, multusNetconf.CNIDir, exec)

	confList, err := libcni.ConfListFromBytes(rawnetconflist)
	if err != nil {
		return nil, logging.Errorf("conflistAdd: error converting the raw bytes into a conflist: %v", err)
	}

	result, err := cniNet.AddNetworkList(context.Background(), confList, rt)
	if err != nil {
		return nil, err
	}

	return result, nil
}

3.3 执行多次 CNI 网络插件的 ADD 操作。
如 pod9 的日志
debug

conflistAdd: &{24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c /var/run/netns/cni-3b58095c-52a9-c2c4-d9ba-ad30f44fee13 eth0 [[IgnoreUnknown true] [K8S_POD_NAMESPACE default] [K8S_POD_NAME pod9] [K8S_POD_INFRA_CONTAINER_ID 24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c] [K8S_POD_UID 3da6f436-bb79-461e-8595-6779f972ca76] [K8S_POD_NAMESPACE default] [K8S_POD_NAME pod9] [K8S_POD_INFRA_CONTAINER_ID 24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c] [K8S_POD_UID 3da6f436-bb79-461e-8595-6779f972ca76] [IgnoreUnknown 1]] map[] }, {"cniVersion":"0.3.1","name":"kube-ovn","plugins":[{"server_socket":"/run/openvswitch/kube-ovn-daemon.sock","type":"kube-ovn"},{"capabilities":{"portMappings":true},"type":"portmap"}]}


confAdd: &{24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c /var/run/netns/cni-3b58095c-52a9-c2c4-d9ba-ad30f44fee13 net1 [[IgnoreUnknown true] [K8S_POD_NAMESPACE default] [K8S_POD_NAME pod9] [K8S_POD_INFRA_CONTAINER_ID 24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c] [K8S_POD_UID 3da6f436-bb79-461e-8595-6779f972ca76] [K8S_POD_NAMESPACE default] [K8S_POD_NAME pod9] [K8S_POD_INFRA_CONTAINER_ID 24a1efa35675f1382fa12a5849c0597bf4bcb7e4c1d7764dc2b5f3701b57b11c] [K8S_POD_UID 3da6f436-bb79-461e-8595-6779f972ca76] [IgnoreUnknown 1]] map[] }, {"cniVersion":"0.3.0","name":"attachnet1","provider":"attachnet1.mec-nets.ovn","server_socket":"/run/openvswitch/kube-ovn-daemon.sock","type":"kube-ovn"}