上一篇介绍了bridge的实现，这里介绍一下calico的实现。和上一篇的结构一样的，先看add然后看del，具体添加网卡的代码如下：

func cmdAdd(args *skel.CmdArgs) error {
    // Unmarshal the network config, and perform validation
    conf := NetConf{}
    if err := json.Unmarshal(args.StdinData, &conf); err != nil {
        return fmt.Errorf("failed to load netconf: %v", err)
    }

    cniVersion := conf.CNIVersion

    ConfigureLogging(conf.LogLevel)

    workload, orchestrator, err := GetIdentifiers(args)
    if err != nil {
        return err
    }

    logger := CreateContextLogger(workload)

    // Allow the nodename to be overridden by the network config
    updateNodename(conf, logger)

    logger.WithFields(log.Fields{
        "Orchestrator": orchestrator,
        "Node":         nodename,
    }).Info("Extracted identifiers")

    logger.WithFields(log.Fields{"NetConfg": conf}).Info("Loaded CNI NetConf")
    calicoClient, err := CreateClient(conf)
    if err != nil {
        return err
    }

    // Always check if there's an existing endpoint.
    endpoints, err := calicoClient.WorkloadEndpoints().List(api.WorkloadEndpointMetadata{
        Node:         nodename,
        Orchestrator: orchestrator,
        Workload:     workload})
    if err != nil {
        return err
    }

    logger.Debugf("Retrieved endpoints: %v", endpoints)

    var endpoint *api.WorkloadEndpoint
    if len(endpoints.Items) == 1 {
        endpoint = &endpoints.Items[0]
    }

    fmt.Fprintf(os.Stderr, "Calico CNI checking for existing endpoint: %v\n", endpoint)

    // Collect the result in this variable - this is ultimately what gets "returned" by this function by printing
    // it to stdout.
    var result *current.Result

    // If running under Kubernetes then branch off into the kubernetes code, otherwise handle everything in this
    // function.
    if orchestrator == "k8s" {
        if result, err = k8s.CmdAddK8s(args, conf, nodename, calicoClient, endpoint); err != nil {
            return err
        }
    } else {
        // Default CNI behavior - use the CNI network name as the Calico profile.
        profileID := conf.Name

        if endpoint != nil {
            // There is an existing endpoint - no need to create another.
            // This occurs when adding an existing container to a new CNI network
            // Find the IP address from the endpoint and use that in the response.
            // Don't create the veth or do any networking.
            // Just update the profile on the endpoint. The profile will be created if needed during the
            // profile processing step.
            fmt.Fprintf(os.Stderr, "Calico CNI appending profile: %s\n", profileID)
            endpoint.Spec.Profiles = append(endpoint.Spec.Profiles, profileID)
            result, err = CreateResultFromEndpoint(endpoint)
            logger.WithField("result", result).Debug("Created result from endpoint")
            if err != nil {
                return err
            }
        } else {
            // There's no existing endpoint, so we need to do the following:
            // 1) Call the configured IPAM plugin to get IP address(es)
            // 2) Configure the Calico endpoint
            // 3) Create the veth, configuring it on both the host and container namespace.

            // 1) Run the IPAM plugin and make sure there's an IP address returned.
            logger.WithFields(log.Fields{"paths": os.Getenv("CNI_PATH"),
                "type": conf.IPAM.Type}).Debug("Looking for IPAM plugin in paths")
            ipamResult, err := ipam.ExecAdd(conf.IPAM.Type, args.StdinData)
            logger.WithField("IPAM result", ipamResult).Info("Got result from IPAM plugin")
            if err != nil {
                return err
            }

            // Convert IPAM result into current Result.
            // IPAM result has a bunch of fields that are optional for an IPAM plugin
            // but required for a CNI plugin, so this is to populate those fields.
            // See CNI Spec doc for more details.
            result, err = current.NewResultFromResult(ipamResult)
            if err != nil {
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }

            if len(result.IPs) == 0 {
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return goerrors.New("IPAM plugin returned missing IP config")
            }

            // Parse endpoint labels passed in by Mesos, and store in a map.
            labels := map[string]string{}
            for _, label := range conf.Args.Mesos.NetworkInfo.Labels.Labels {
                labels[label.Key] = label.Value
            }

            // 2) Create the endpoint object
            endpoint = api.NewWorkloadEndpoint()
            endpoint.Metadata.Name = args.IfName
            endpoint.Metadata.Node = nodename
            endpoint.Metadata.Orchestrator = orchestrator
            endpoint.Metadata.Workload = workload
            endpoint.Metadata.Labels = labels
            endpoint.Spec.Profiles = []string{profileID}

            logger.WithField("endpoint", endpoint).Debug("Populated endpoint (without nets)")
            if err = PopulateEndpointNets(endpoint, result); err != nil {
                // Cleanup IP allocation and return the error.
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }
            logger.WithField("endpoint", endpoint).Info("Populated endpoint (with nets)")

            fmt.Fprintf(os.Stderr, "Calico CNI using IPs: %s\n", endpoint.Spec.IPNetworks)

            // 3) Set up the veth
            hostVethName, contVethMac, err := DoNetworking(args, conf, result, logger, "")
            if err != nil {
                // Cleanup IP allocation and return the error.
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }

            logger.WithFields(log.Fields{
                "HostVethName":     hostVethName,
                "ContainerVethMac": contVethMac,
            }).Info("Networked namespace")

            mac, err := net.ParseMAC(contVethMac)
            if err != nil {
                // Cleanup IP allocation and return the error.
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }

            endpoint.Spec.MAC = &cnet.MAC{HardwareAddr: mac}
            endpoint.Spec.InterfaceName = hostVethName
        }

        // Write the endpoint object (either the newly created one, or the updated one with a new ProfileIDs).
        if _, err := calicoClient.WorkloadEndpoints().Apply(endpoint); err != nil {
            // Cleanup IP allocation and return the error.
            ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
            return err
        }

        logger.WithField("endpoint", endpoint).Info("Wrote endpoint to datastore")
    }

    // Handle profile creation - this is only done if there isn't a specific policy handler.
    if conf.Policy.PolicyType == "" {
        logger.Debug("Handling profiles")
        // Start by checking if the profile already exists. If it already exists then there is no work to do.
        // The CNI plugin never updates a profile.
        exists := true
        _, err = calicoClient.Profiles().Get(api.ProfileMetadata{Name: conf.Name})
        if err != nil {
            _, ok := err.(errors.ErrorResourceDoesNotExist)
            if ok {
                exists = false
            } else {
                // Cleanup IP allocation and return the error.
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }
        }

        if !exists {
            // The profile doesn't exist so needs to be created. The rules vary depending on whether k8s is being used.
            // Under k8s (without full policy support) the rule is permissive and allows all traffic.
            // Otherwise, incoming traffic is only allowed from profiles with the same tag.
            fmt.Fprintf(os.Stderr, "Calico CNI creating profile: %s\n", conf.Name)
            var inboundRules []api.Rule
            if orchestrator == "k8s" {
                inboundRules = []api.Rule{{Action: "allow"}}
            } else {
                inboundRules = []api.Rule{{Action: "allow", Source: api.EntityRule{Tag: conf.Name}}}
            }

            profile := &api.Profile{
                Metadata: api.ProfileMetadata{
                    Name: conf.Name,
                    Tags: []string{conf.Name},
                },
                Spec: api.ProfileSpec{
                    EgressRules:  []api.Rule{{Action: "allow"}},
                    IngressRules: inboundRules,
                },
            }

            logger.WithField("profile", profile).Info("Creating profile")

            if _, err := calicoClient.Profiles().Create(profile); err != nil {
                // Cleanup IP allocation and return the error.
                ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return err
            }
        }
    }

    // Set Gateway to nil. Calico-IPAM doesn't set it, but host-local does.
    // We modify IPs subnet received from the IPAM plugin (host-local),
    // so Gateway isn't valid anymore. It is also not used anywhere by Calico.
    for _, ip := range result.IPs {
        ip.Gateway = nil
    }

    // Print result to stdout, in the format defined by the requested cniVersion.
    return types.PrintResult(result, cniVersion)
}

创建和bridge很相似，不过这里代码有点长，一步一步解析，calico实现了标准的cni的实现，当然可以在kubernetes下面，也可以在任何cni的容器管理平台之上运行。先看k8s相关实现k8s.CmdAddK8s，

func CmdAddK8s(args *skel.CmdArgs, conf utils.NetConf, nodename string, calicoClient *calicoclient.Client, endpoint *api.WorkloadEndpoint) (*current.Result, error) {
    var err error
    var result *current.Result

    k8sArgs := utils.K8sArgs{}
    err = types.LoadArgs(args.Args, &k8sArgs)
    if err != nil {
        return nil, err
    }

    utils.ConfigureLogging(conf.LogLevel)

    workload, orchestrator, err := utils.GetIdentifiers(args)
    if err != nil {
        return nil, err
    }
    logger := utils.CreateContextLogger(workload)
    logger.WithFields(log.Fields{
        "Orchestrator": orchestrator,
        "Node":         nodename,
    }).Info("Extracted identifiers for CmdAddK8s")

    if endpoint != nil {
        // This happens when Docker or the node restarts. K8s calls CNI with the same parameters as before.
        // Do the networking (since the network namespace was destroyed and recreated).
        // There's an existing endpoint - no need to create another. Find the IP address from the endpoint
        // and use that in the response.
        result, err = utils.CreateResultFromEndpoint(endpoint)
        if err != nil {
            return nil, err
        }
        logger.WithField("result", result).Debug("Created result from existing endpoint")
        // If any labels changed whilst the container was being restarted, they will be picked up by the policy
        // controller so there's no need to update the labels here.
    } else {
        client, err := newK8sClient(conf, logger)
        if err != nil {
            return nil, err
        }
        logger.WithField("client", client).Debug("Created Kubernetes client")

        if conf.IPAM.Type == "host-local" && strings.EqualFold(conf.IPAM.Subnet, "usePodCidr") {
            // We've been told to use the "host-local" IPAM plugin with the Kubernetes podCidr for this node.
            // Replace the actual value in the args.StdinData as that's what's passed to the IPAM plugin.
            fmt.Fprintf(os.Stderr, "Calico CNI fetching podCidr from Kubernetes\n")
            var stdinData map[string]interface{}
            if err := json.Unmarshal(args.StdinData, &stdinData); err != nil {
                return nil, err
            }
            podCidr, err := getPodCidr(client, conf, nodename)
            if err != nil {
                return nil, err
            }
            logger.WithField("podCidr", podCidr).Info("Fetched podCidr")
            stdinData["ipam"].(map[string]interface{})["subnet"] = podCidr
            fmt.Fprintf(os.Stderr, "Calico CNI passing podCidr to host-local IPAM: %s\n", podCidr)
            args.StdinData, err = json.Marshal(stdinData)
            if err != nil {
                return nil, err
            }
            logger.WithField("stdin", string(args.StdinData)).Debug("Updated stdin data")
        }

        labels := make(map[string]string)
        annot := make(map[string]string)

        // Only attempt to fetch the labels and annotations from Kubernetes
        // if the policy type has been set to "k8s". This allows users to
        // run the plugin under Kubernetes without needing it to access the
        // Kubernetes API
        if conf.Policy.PolicyType == "k8s" {
            var err error

            labels, annot, err = getK8sLabelsAnnotations(client, k8sArgs)
            if err != nil {
                return nil, err
            }
            logger.WithField("labels", labels).Debug("Fetched K8s labels")
            logger.WithField("annotations", annot).Debug("Fetched K8s annotations")

            // Check for calico IPAM specific annotations and set them if needed.
            if conf.IPAM.Type == "calico-ipam" {

                v4pools := annot["cni.projectcalico.org/ipv4pools"]
                v6pools := annot["cni.projectcalico.org/ipv6pools"]

                if len(v4pools) != 0 || len(v6pools) != 0 {
                    var stdinData map[string]interface{}
                    if err := json.Unmarshal(args.StdinData, &stdinData); err != nil {
                        return nil, err
                    }
                    var v4PoolSlice, v6PoolSlice []string

                    if len(v4pools) > 0 {
                        if err := json.Unmarshal([]byte(v4pools), &v4PoolSlice); err != nil {
                            logger.WithField("IPv4Pool", v4pools).Error("Error parsing IPv4 IPPools")
                            return nil, err
                        }

                        if _, ok := stdinData["ipam"].(map[string]interface{}); !ok {
                            logger.Fatal("Error asserting stdinData type")
                            os.Exit(0)
                        }
                        stdinData["ipam"].(map[string]interface{})["ipv4_pools"] = v4PoolSlice
                        logger.WithField("ipv4_pools", v4pools).Debug("Setting IPv4 Pools")
                    }
                    if len(v6pools) > 0 {
                        if err := json.Unmarshal([]byte(v6pools), &v6PoolSlice); err != nil {
                            logger.WithField("IPv6Pool", v6pools).Error("Error parsing IPv6 IPPools")
                            return nil, err
                        }

                        if _, ok := stdinData["ipam"].(map[string]interface{}); !ok {
                            logger.Fatal("Error asserting stdinData type")
                            os.Exit(0)
                        }
                        stdinData["ipam"].(map[string]interface{})["ipv6_pools"] = v6PoolSlice
                        logger.WithField("ipv6_pools", v6pools).Debug("Setting IPv6 Pools")
                    }

                    newData, err := json.Marshal(stdinData)
                    if err != nil {
                        logger.WithField("stdinData", stdinData).Error("Error Marshaling data")
                        return nil, err
                    }
                    args.StdinData = newData
                    logger.WithField("stdin", string(args.StdinData)).Debug("Updated stdin data")
                }
            }
        }

        ipAddrsNoIpam := annot["cni.projectcalico.org/ipAddrsNoIpam"]
        ipAddrs := annot["cni.projectcalico.org/ipAddrs"]

        // switch based on which annotations are passed or not passed.
        switch {
        case ipAddrs == "" && ipAddrsNoIpam == "":
            // Call IPAM plugin if ipAddrsNoIpam or ipAddrs annotation is not present.
            logger.Debugf("Calling IPAM plugin %s", conf.IPAM.Type)
            ipamResult, err := ipam.ExecAdd(conf.IPAM.Type, args.StdinData)
            if err != nil {
                return nil, err
            }
            logger.Debugf("IPAM plugin returned: %+v", ipamResult)

            // Convert IPAM result into current Result.
            // IPAM result has a bunch of fields that are optional for an IPAM plugin
            // but required for a CNI plugin, so this is to populate those fields.
            // See CNI Spec doc for more details.
            result, err = current.NewResultFromResult(ipamResult)
            if err != nil {
                utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return nil, err
            }

            if len(result.IPs) == 0 {
                utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
                return nil, errors.New("IPAM plugin returned missing IP config")
            }

        case ipAddrs != "" && ipAddrsNoIpam != "":
            // Can't have both ipAddrs and ipAddrsNoIpam annotations at the same time.
            e := fmt.Errorf("Can't have both annotations: 'ipAddrs' and 'ipAddrsNoIpam' in use at the same time")
            logger.Error(e)
            return nil, e
        case ipAddrsNoIpam != "":
            // ipAddrsNoIpam annotation is set so bypass IPAM, and set the IPs manually.
            overriddenResult, err := overrideIPAMResult(ipAddrsNoIpam, logger)
            if err != nil {
                return nil, err
            }
            logger.Debugf("Bypassing IPAM to set the result to: %+v", overriddenResult)

            // Convert overridden IPAM result into current Result.
            // This method fill in all the empty fields necessory for CNI output according to spec.
            result, err = current.NewResultFromResult(overriddenResult)
            if err != nil {
                return nil, err
            }

            if len(result.IPs) == 0 {
                return nil, errors.New("Failed to build result")
            }

        case ipAddrs != "":
            // When ipAddrs annotation is set, we call out to the configured IPAM plugin
            // requesting the specific IP addresses included in the annotation.
            result, err = ipAddrsResult(ipAddrs, conf, args, logger)
            if err != nil {
                return nil, err
            }
            logger.Debugf("IPAM result set to: %+v", result)
        }

        // Create the endpoint object and configure it.
        endpoint = api.NewWorkloadEndpoint()
        endpoint.Metadata.Name = args.IfName
        endpoint.Metadata.Node = nodename
        endpoint.Metadata.ActiveInstanceID = args.ContainerID
        endpoint.Metadata.Orchestrator = orchestrator
        endpoint.Metadata.Workload = workload
        endpoint.Metadata.Labels = labels

        // Set the profileID according to whether Kubernetes policy is required.
        // If it's not, then just use the network name (which is the normal behavior)
        // otherwise use one based on the Kubernetes pod's Namespace.
        if conf.Policy.PolicyType == "k8s" {
            endpoint.Spec.Profiles = []string{fmt.Sprintf("k8s_ns.%s", k8sArgs.K8S_POD_NAMESPACE)}
        } else {
            endpoint.Spec.Profiles = []string{conf.Name}
        }

        // Populate the endpoint with the output from the IPAM plugin.
        if err = utils.PopulateEndpointNets(endpoint, result); err != nil {
            // Cleanup IP allocation and return the error.
            utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
            return nil, err
        }
        logger.WithField("endpoint", endpoint).Info("Populated endpoint")
    }
    fmt.Fprintf(os.Stderr, "Calico CNI using IPs: %s\n", endpoint.Spec.IPNetworks)

    // Whether the endpoint existed or not, the veth needs (re)creating.
    hostVethName := k8sbackend.VethNameForWorkload(workload)
    _, contVethMac, err := utils.DoNetworking(args, conf, result, logger, hostVethName)
    if err != nil {
        // Cleanup IP allocation and return the error.
        logger.Errorf("Error setting up networking: %s", err)
        utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
        return nil, err
    }

    mac, err := net.ParseMAC(contVethMac)
    if err != nil {
        // Cleanup IP allocation and return the error.
        logger.Errorf("Error parsing MAC (%s): %s", contVethMac, err)
        utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
        return nil, err
    }
    endpoint.Spec.MAC = &cnet.MAC{HardwareAddr: mac}
    endpoint.Spec.InterfaceName = hostVethName
    logger.WithField("endpoint", endpoint).Info("Added Mac and interface name to endpoint")

    // Write the endpoint object (either the newly created one, or the updated one)
    if _, err := calicoClient.WorkloadEndpoints().Apply(endpoint); err != nil {
        // Cleanup IP allocation and return the error.
        utils.ReleaseIPAllocation(logger, conf.IPAM.Type, args.StdinData)
        return nil, err
    }
    logger.Info("Wrote updated endpoint to datastore")

    return result, nil
}

1、先通过newK8sClient创建kubernetes client。判断conf.IPAM.Type ipam的网络实现，当然calico自身已经具备一个calico-ipam的网络管理实现，如果使用host-local网络配置并且配置了usePodCidr的话，通过k8s获取podCidr，这个里面需要在k8s里面设置node的podCidr。

2、判读网络策略是否使用k8s。这个里面通过k8s api获取pod的annotation，并且添加一个calico/k8s_ns，关联空间的的一个label。

3.下面进入calico-ipam的地址分配，这里先要判断k8s是否以及指定IP地址，如果没有设置，调用ipamResult, err := ipam.ExecAdd(conf.IPAM.Type, args.StdinData)分配IP;如果ipAddrs != “”说明指定IP了，就不需要ipam分配，直接告诉ipam地址被占用返回地址result, err = ipAddrsResult(ipAddrs, conf, args, logger)，k8s除了设置ippool内的IP地址，还支持自己定义非IPAM管理的ip地址ipAddrsNoIpam != “”，这个就不需要ipam了。

4.创建网络卡，这个和bridge的实现是一样的，通过 utils.DoNetworking实现，这个函数里面通过netlink.LinkAdd创建一个网卡对veth，主机端一cali开通，后面11位是容器的id开头。然后就是把网卡插入容器内设置IP和路由，这个都和bridge一样，具体代码如下

if err = ip.AddDefaultRoute(gw, contVeth); err != nil {
                    return fmt.Errorf("failed to add route %v", err)
                }

if err = netlink.AddrAdd(contVeth, &netlink.Addr{IPNet: &addr.Address}); err != nil {
                    return fmt.Errorf("failed to add IP addr to %q: %v", contVethName, err)
                }

还有就是设置主机路由了，就是设置目标IP是容器的流量都交个容器在主机端的网卡就是cali-xxxxxxxxx那个网卡。

5.然后就可以创建endpoint的了，先装配各种参数，然后通过calicoClient.WorkloadEndpoints().Apply(endpoint)创建这个endpoint。一个calico的endpoint代表一个网络点，可以简单理解为网卡的别名，就是kubernetes有了pod，但一个pod有多个endpoint一样，解耦。一个calico的endpoint包含一些metadata信息
如：

        endpoint.Metadata.Name = args.IfName
        endpoint.Metadata.Node = nodename
        endpoint.Metadata.ActiveInstanceID = args.ContainerID
        endpoint.Metadata.Orchestrator = orchestrator
        endpoint.Metadata.Workload = workload
        endpoint.Metadata.Labels = labels

还有一些网卡信息

endpoint.Spec.MAC = &cnet.MAC{HardwareAddr: mac}
endpoint.Spec.InterfaceName = hostVethName