作者：张华 发表于：2021-01-25
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如OpenStack中的Secrity Group可以用来在传统服务应用架构中来实现层与层这的网络访问规则，但对于容器化的服务场景，一个容器一个应用粒度更小，且主机节点的个数和 IP地址都 是快速变化的，这样分层防火墙的思路不再可行。Calico就是这样一个工具，通过修改每个节点上的iptables与路由来实现容器间数据的路由和访问控制，并通过etcd协调节点配置信息。 K8s Network Policy可使用Calico作为CNI实现隔离性，只有匹配规则的流量才能进入pod，同理只有匹配规则的流量才可以离开pod。
Canal是Flannel与Calico的结合，访问控制部分由Calico(calico-node -felix)实现, 网络部分仍由Flannel实现(Calico有BGP路由与IPIP隧道两种，Flannel则有Vxlan隧道)。
Calico的网络规则的用法可参见(https://www.open-open.com/news/view/1a7c496), k8s通过CNI集成Canal能使用Calico实现的网络规则部分，但用法是怎样的呢(可参见－https://www.jianshu.com/p/331235d8bcbb）：

  • 通过kubectl client创建NetworkPolicy资源
  • calico的policy-controller(calico-kube-controllers集成了calicoctl用于写policy)监听networkpolicy资源，获取到后写入calico的etcd数据库
  • node上calico-felix从etcd数据库中获取policy资源，调用iptables做相应配置。

Calico policy架构

在node上最终生成的最终iptables如下：
在这里插入图片描述

测试环境信息

kubernetes-master/0, kubernetes-worker/0, kubernetes-worker/1的IP如下：

kubernetes-master/0*      active    idle   3        10.5.2.205      6443/tcp        Kubernetes master running.
  canal/2*                active    idle            10.5.2.205                      Flannel subnet 10.1.49.1/24
  containerd/2*           active    idle            10.5.2.205                      Container runtime available
kubernetes-worker/0*      active    idle   4        10.5.3.197      80/tcp,443/tcp  Kubernetes worker running.
  canal/0                 active    idle            10.5.3.197                      Flannel subnet 10.1.94.1/24
  containerd/0            active    idle            10.5.3.197                      Container runtime available
kubernetes-worker/1       active    idle   5        10.5.4.4        80/tcp,443/tcp  Kubernetes worker running.
  canal/1                 active    idle            10.5.4.4                        Flannel subnet 10.1.3.1/24
  containerd/1            active    idle            10.5.4.4                        Container runtime available

$ kubectl get pods -o wide
NAME                            READY   STATUS    RESTARTS   AGE    IP          NODE                NOMINATED NODE   READINESS GATES
ubuntu-debug-794979f648-4dj8w   1/1     Running   1          118m   10.1.3.14   juju-11ff05-k8s-5   <none>           <none>
ubuntu-debug-794979f648-fwdmv   1/1     Running   1          118m   10.1.94.7   juju-11ff05-k8s-4   <none>           <none>

canal中的flannel提供pod-to-pod通信

flannel内的tunnel网段是10.1.0.0/16，vxlan类型：

# etcdctl --cert-file /etc/ssl/flannel/client-cert.pem --key-file /etc/ssl/flannel/client-key.pem --ca-file /etc/ssl/flannel/client-ca.pem -endpoints=https://10.5.1.44:2379 get /coreos.com/network/config
{"Network": "10.1.0.0/16", "Backend": {"Type": "vxlan"}}

flannel为kubernetes-master/0, kubernetes-worker/0, kubernetes-worker/1分配的subnet分别是：

root@juju-11ff05-k8s-4:~# etcdctl --cert-file /etc/ssl/flannel/client-cert.pem --key-file /etc/ssl/flannel/client-key.pem --ca-file /etc/ssl/flannel/client-ca.pem -endpoints=https://10.5.1.44:2379 ls /coreos.com/network/subnets/
/coreos.com/network/subnets/10.1.94.0-24 (kubernetes-worker/0)
/coreos.com/network/subnets/10.1.3.0-24  (kubernetes-worker/1)
/coreos.com/network/subnets/10.1.49.0-24 (kubernetes-master/0)

flannel是根据subnet.env分配的，kubernetes-master/0, kubernetes-worker/0, kubernetes-worker/1均应有下列配置，下面只是粘出了kubernetes-worker/0上的例子：

root@juju-11ff05-k8s-4:~# cat /run/flannel/subnet.env 
FLANNEL_NETWORK=10.1.0.0/16
FLANNEL_SUBNET=10.1.94.1/24
FLANNEL_MTU=8908
FLANNEL_IPMASQ=true

root@juju-11ff05-k8s-4:~# ip addr show flannel.1 |grep global
    inet 10.1.94.0/32 scope global flannel.1

防火墙应该允许该子网的流量进入

#on kubernetes-worker/0, it should ALLOW 10.1.94.0/24
root@juju-11ff05-k8s-4:~# iptables-save |grep 10.1.94 |grep POST
-A POSTROUTING ! -s 10.1.0.0/16 -d 10.1.94.0/24 -j RETURN
# iptables -t nat -nvL |grep 'Chain POSTROUTING' -A9
Chain POSTROUTING (policy ACCEPT 1447 packets, 89820 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 1885  119K KUBE-POSTROUTING  all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* kubernetes postrouting rules */
    8   460 fan-egress  all  --  *      *       252.0.0.0/8          0.0.0.0/0           
  183 11249 RETURN     all  --  *      *       10.1.0.0/16          10.1.0.0/16         
    6   360 MASQUERADE  all  --  *      *       10.1.0.0/16         !224.0.0.0/4         
    0     0 RETURN     all  --  *      *      !10.1.0.0/16          10.1.94.0/24        
    0     0 MASQUERADE  all  --  *      *      !10.1.0.0/16          10.1.0.0/16

另外，底层docker或contained也应该将etcd中为每个节点配置的subnet加载进去：

  • 如果使用docker, 容器内的流量会先到docker0, 然后根据下列路由到flannel.1
  • 如果使用containerd，是通过下列的/etc/cni/net.d/10-canal.conflist文件将subnet设置进flannel的。

canal中的Calico/Felix提供网络访问规则

本来calico的felix（通过calico-node -felix运行）是运行在每个节点上负责配置路由及网络访问规则的，现在路由这块不做还是由Flannel来做，所以主要用到felix的网络访问规则。calio的felix的访问规则这块由下列iptables实现(详见Calico网络模型 - https://www.cnblogs.com/menkeyi/p/11364977.html)，但尚不清楚canal有没有作其他更改。
在这里插入图片描述

root@juju-11ff05-k8s-4:~# route -n |grep flannel
10.1.3.0        10.1.3.0        255.255.255.0   UG    0      0        0 flannel.1
10.1.49.0       10.1.49.0       255.255.255.0   UG    0      0        0 flannel.1

接着流量会被封装成vxlan tunnel送到对方endpoint.
Calico如何管网络策略的还没研究清楚(我估计上节中的充许防火墙规则就是这块设置的，当然只是猜测)。

root@juju-11ff05-k8s-4:~# ip addr show |grep cali -A1
6: cali8215eb6fd4a@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether ee:ee:ee:ee:ee:ee brd ff:ff:ff:ff:ff:ff link-netns cni-262d6f97-ad60-b48b-85e1-ee180b620c30
--
7: cali105686d7bac@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether ee:ee:ee:ee:ee:ee brd ff:ff:ff:ff:ff:ff link-netns cni-09304b68-97b3-c72b-2bd6-b47d9f626890

root@juju-11ff05-k8s-4:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.5.0.1        0.0.0.0         UG    100    0        0 ens3
10.1.3.0        10.1.3.0        255.255.255.0   UG    0      0        0 flannel.1
10.1.49.0       10.1.49.0       255.255.255.0   UG    0      0        0 flannel.1
10.1.94.6       0.0.0.0         255.255.255.255 UH    0      0        0 cali105686d7bac
10.1.94.7       0.0.0.0         255.255.255.255 UH    0      0        0 cali8215eb6fd4a
10.5.0.0        0.0.0.0         255.255.0.0     U     0      0        0 ens3
169.254.169.254 10.5.0.1        255.255.255.255 UGH   100    0        0 ens3
252.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 fan-252
root@juju-11ff05-k8s-4:~# ip netns exec cni-09304b68-97b3-c72b-2bd6-b47d9f626890 route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         169.254.1.1     0.0.0.0         UG    0      0        0 eth0
169.254.1.1     0.0.0.0         255.255.255.255 UH    0      0        0 eth0
root@juju-11ff05-k8s-4:~# ip netns exec cni-262d6f97-ad60-b48b-85e1-ee180b620c30 route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         169.254.1.1     0.0.0.0         UG    0      0        0 eth0
169.254.1.1     0.0.0.0         255.255.255.255 UH    0      0        0 eth0


root@juju-11ff05-k8s-4:~# ctr c ls
CONTAINER      IMAGE                                              RUNTIME                  
calico-node    rocks.canonical.com:443/cdk/calico/node:v3.10.1    io.containerd.runc.v2    

root@juju-11ff05-k8s-4:~# ip netns
cni-09304b68-97b3-c72b-2bd6-b47d9f626890 (id: 1)
cni-262d6f97-ad60-b48b-85e1-ee180b620c30 (id: 0)

root@juju-11ff05-k8s-4:~# ip netns exec cni-09304b68-97b3-c72b-2bd6-b47d9f626890 ip addr show |grep eth0
3: eth0@if7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    inet 10.1.94.6/32 scope global eth0
root@juju-11ff05-k8s-4:~# ip netns exec cni-262d6f97-ad60-b48b-85e1-ee180b620c30 ip addr show |grep eth0
3: eth0@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    inet 10.1.94.7/32 scope global eth0

root@juju-11ff05-k8s-4:~# cat /etc/cni/net.d/10-canal.conflist 
{
  "name": "cdk-canal",
  "cniVersion": "0.3.0",
  "plugins": [
    {
      "type": "calico",
      "etcd_endpoints": "https://10.5.1.44:2379",
      "etcd_key_file": "/opt/calicoctl/etcd-key",
      "etcd_cert_file": "/opt/calicoctl/etcd-cert",
      "etcd_ca_cert_file": "/opt/calicoctl/etcd-ca",
      "log_level": "info",
      "ipam": {
        "type": "host-local",
        "subnet": "10.1.94.1/24"
      },
      "policy": {
        "type": "k8s"
      },
      "kubernetes": {
        "kubeconfig": "/root/cdk/kubeconfig"
      }
    },
    {
      "type": "portmap",
      "capabilities": {"portMappings": true},
      "snat": true
    }
  ]
}

iptables提供Service-to-Pod通信

以dashboard为例：

$ kubectl get services -A |grep kubernetes-dashboard
kubernetes-dashboard              dashboard-metrics-scraper                ClusterIP   10.152.183.92    <none>        8000/TCP                 3d22h
kubernetes-dashboard              kubernetes-dashboard                     ClusterIP   10.152.183.89    <none>        443/TCP                  3d22h
$ kubectl describe --namespace kubernetes-dashboard service kubernetes-dashboard |grep -E 'IPs|Endpoints|Port'
IPs:               10.152.183.89
Port:              <unset>  443/TCP
TargetPort:        8443/TCP
Endpoints:         10.1.3.16:8443
$ kubectl get pods -A -o wide |grep dashboard
kubernetes-dashboard              dashboard-metrics-scraper-74757fb5b7-9rqxd                1/1     Running   1          3d22h   10.1.3.17    juju-11ff05-k8s-5   <none>           <none>
kubernetes-dashboard              kubernetes-dashboard-64f87676d4-s26bs                     1/1     Running   1          3d22h   10.1.3.16    juju-11ff05-k8s-5   <none>           <none>

# 如果有多个endpoint也就会有多个KUBE-SEP-xxx实实现LB, 其中MARK-MASQ用于set mark
root@juju-11ff05-k8s-4:~# iptables-save |grep kubernetes-dashboard
-A KUBE-SERVICES ! -s 10.1.0.0/16 -d 10.152.183.89/32 -p tcp -m comment --comment "kubernetes-dashboard/kubernetes-dashboard cluster IP" -m tcp --dport 443 -j KUBE-MARK-MASQ #egress
-A KUBE-SERVICES -d 10.152.183.89/32 -p tcp -m comment --comment "kubernetes-dashboard/kubernetes-dashboard cluster IP" -m tcp --dport 443 -j KUBE-SVC-CEZPIJSAUFW5MYPQ       #ingress
-A KUBE-SVC-CEZPIJSAUFW5MYPQ -m comment --comment "kubernetes-dashboard/kubernetes-dashboard" -j KUBE-SEP-RMJCCMAWKQ3DCGZP
-A KUBE-SEP-RMJCCMAWKQ3DCGZP -s 10.1.3.16/32 -m comment --comment "kubernetes-dashboard/kubernetes-dashboard" -j KUBE-MARK-MASQ                      #egress
-A KUBE-SEP-RMJCCMAWKQ3DCGZP -p tcp -m comment --comment "kubernetes-dashboard/kubernetes-dashboard" -m tcp -j DNAT --to-destination 10.1.3.16:8443  #ingress

相关服务

systemctl status flannel
systemctl status calico-node.service
systemctl status snap.kubelet.daemon.service

附录 - 一个客户问题

一个客户有一个k8s over vSphere managed by juju 环境，报告使用 goldpinger发现pod间网络不通。
先是遇到问题https://bugs.launchpad.net/juju/+bug/1831244，juju controllers与vSphere之间存在用户名和密码的问题，这样"juju status --format yaml"能看到controller处于suspended状态（注意：只有带–format yaml才能看到得）。
解决1831244之后就可以正常创建新节点了，将那个失败的keycloak pod迁移到新节点，问题依然存在，'kubectl logs’看到keycloak失败原因是： ‘Caused by: java.net.UnknownHostException: postgres’
显然，keycloak依赖于postgres service, 存在dns问题。
coredns并没有从旧节新移到新节点，旧节点上存在一个问题, canal的flannel使用的subnet(/run/flannel/subnet.env)与canal的calico使用的subnet(/etc/cni/net.d/10-canal.conflist)不一致，这样导致旧节点上的iptables下列倒数第二行就弄错了，没有充许flannel的数据包。

grep -A9 "Chain POSTROUTING" sos_commands/networking/iptables_-t_nat_-nvL
Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1411K 88M cali-POSTROUTING all -- * * 0.0.0.0/0 0.0.0.0/0 /* cali:O3lYWMrLQYEMJtB5 */
1378K 86M CNI-HOSTPORT-MASQ all -- * * 0.0.0.0/0 0.0.0.0/0 /* CNI portfwd requiring masquerade */
1376K 86M KUBE-POSTROUTING all -- * * 0.0.0.0/0 0.0.0.0/0 /* kubernetes postrouting rules */
800K 50M RETURN all -- * * 172.17.240.0/20 172.17.240.0/20
0 0 MASQUERADE all -- * * 172.17.240.0/20 !224.0.0.0/4
0 0 RETURN all -- * * !172.17.240.0/20 172.17.247.0/24
521K 31M MASQUERADE all -- * * !172.17.240.0/20 172.17.240.0/20

下列语句可以查询etcd中每个节点的subnet配置：

juju run -u kubernetes-worker/<N> etcdctl --cert-file /etc/ssl/flannel/client-cert.pem --key-file /etc/ssl/flannel/client-key.pem --ca-file /etc/ssl/flannel/client-ca.pem -endpoints=https://10.1.234.195:2379,https://10.1.234.196:2379,https://10.1.234.203:2379 ls /coreos.com/network/subnets/

需要先从etcd里删除它　－　rm /coreos.com/network/subnets/172.17.247.0-24
然后重它systemctl restart flannel.service, 接着将 /run/flannel/subnet.env的subnet更新为正确的subnet, 之后通过“ip a s flannel.1 ”确认。最后：
systemctl restart calico-node.service
systemctl restart snap.kubelet.daemon.service

calicoctl测试

juju ssh kubernetes-worker/0 -- sudo -s
#https://docs.projectcalico.org/getting-started/clis/calicoctl/install
curl -O -L  https://github.com/projectcalico/calicoctl/releases/download/v3.17.1/calicoctl
cp calicoctl /usr/bin/ && chmod +x /usr/bin/calicoctl
#copy env variable like ETCD_ENDPOINTS from the output of 'ps -ef |grep calicoctl'
ETCD_ENDPOINTS=https://10.5.0.131:2379 ETCD_CA_CERT_FILE=/opt/calicoctl/etcd-ca ETCD_CERT_FILE=/opt/calicoctl/etcd-cert ETCD_KEY_FILE=/opt/calicoctl/etcd-key calicoctl get networkPolicy
ETCD_ENDPOINTS=https://10.5.0.131:2379 ETCD_CA_CERT_FILE=/opt/calicoctl/etcd-ca ETCD_CERT_FILE=/opt/calicoctl/etcd-cert ETCD_KEY_FILE=/opt/calicoctl/etcd-key calicoctl get globalNetworkPolicy

k8s networkpolicy - https://docs.projectcalico.org/security/kubernetes-network-policy
calico networkpolicy - https://docs.projectcalico.org/security/calico-network-policy
cat << EOF | sudo tee calicoPolicyTest.yaml
apiVersion: projectcalico.org/v3
kind: GlobalNetworkPolicy
metadata:
  name: deny-circle-blue
spec:
  selector: k8s-app == 'kubernetes-dashboard'
  ingress:
  - action: Deny
    protocol: TCP
    destination:
      ports:
      - 22
EOF
ETCD_ENDPOINTS=https://10.5.0.131:2379 ETCD_CA_CERT_FILE=/opt/calicoctl/etcd-ca ETCD_CERT_FILE=/opt/calicoctl/etcd-cert ETCD_KEY_FILE=/opt/calicoctl/etcd-key calicoctl get globalNetworkPolicy
#go to the worker which dashboard pos is on (kubectl get pod -A -o wide |grep dash)
iptables-save |grep 2222

在这里插入图片描述

reference

[1] https://courses.academy.tigera.io/courses/course-v1:tigera+CCO-L1+CCO-L1-2020/course/

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