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k8s网络问题以及容器跨宿主机通信原理

news 2026/2/9 4:04:16

【0】资源配置文件

[root@mcwk8s03 mcwtest]# ls
mcwdeploy.yaml
[root@mcwk8s03 mcwtest]# cat mcwdeploy.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:labels:app: mcwpythonname: mcwtest-deploy
spec:replicas: 1selector:matchLabels:app: mcwpythontemplate:metadata:labels:app: mcwpythonspec:containers:- command:- sh- -c- echo 123 >>/mcw.txt && cd / && rm -rf /etc/yum.repos.d/* && curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo  && yum install -y python2  && python2 -m SimpleHTTPServer 20000image: centosimagePullPolicy: IfNotPresentname: mcwtestdnsPolicy: "None"dnsConfig:nameservers:- 8.8.8.8- 8.8.4.4searches:#- namespace.svc.cluster.local- my.dns.search.suffixoptions:- name: ndotsvalue: "5"
---
apiVersion: v1
kind: Service
metadata:name: mcwtest-svc
spec:ports:- name: mcwportport: 2024protocol: TCPtargetPort: 20000selector:app: mcwpythontype: NodePort
[root@mcwk8s03 mcwtest]#

[1]查看服务部分通，部分不通

[root@mcwk8s03 mcwtest]# kubectl get svc 
NAME          TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.2.0.1     <none>        443/TCP          583d
mcwtest-svc   NodePort    10.2.0.155   <none>        2024:41527/TCP   133m
nginx         ClusterIP   None         <none>        80/TCP           413d
[root@mcwk8s03 mcwtest]# curl -I 10.2.0.155
curl: (7) Failed connect to 10.2.0.155:80; Connection timed out
[root@mcwk8s03 mcwtest]# curl -I 10.0.0.33:41527
curl: (7) Failed connect to 10.0.0.33:41527; Connection refused
[root@mcwk8s03 mcwtest]# curl -I 10.0.0.36:41527
curl: (7) Failed connect to 10.0.0.36:41527; Connection timed out
[root@mcwk8s03 mcwtest]# curl -I 10.0.0.35:41527
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.7.18
Date: Tue, 04 Jun 2024 16:38:18 GMT
Content-type: text/html; charset=ANSI_X3.4-1968
Content-Length: 816[root@mcwk8s03 mcwtest]#

【2】查看，能通的IP，是因为在容器所在的宿主机，因此需要排查容器跨宿主机是否可以通信

[root@mcwk8s03 mcwtest]# kubectl get pod -o wide|grep mcwtest
mcwtest-deploy-6465665557-g9zjd     1/1     Running            0          37m    172.17.98.13   mcwk8s05   <none>           <none>
[root@mcwk8s03 mcwtest]# kubectl get nodes -o wide
NAME       STATUS   ROLES    AGE    VERSION    INTERNAL-IP   EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION          CONTAINER-RUNTIME
mcwk8s05   Ready    <none>   580d   v1.15.12   10.0.0.35     <none>        CentOS Linux 7 (Core)   3.10.0-693.el7.x86_64   docker://20.10.21
mcwk8s06   Ready    <none>   580d   v1.15.12   10.0.0.36     <none>        CentOS Linux 7 (Core)   3.10.0-693.el7.x86_64   docker://20.10.21
[root@mcwk8s03 mcwtest]#

【3】排查容器是否可以跨宿主机IP，首先这个容器是在这个宿主机上，应该优先排查这个宿主机是否能到其他机器的docker0 IP

[root@mcwk8s03 mcwtest]# ifconfig docker
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500inet 172.17.83.1  netmask 255.255.255.0  broadcast 172.17.83.255ether 02:42:e9:a4:51:4f  txqueuelen 0  (Ethernet)RX packets 0  bytes 0 (0.0 B)RX errors 0  dropped 0  overruns 0  frame 0TX packets 0  bytes 0 (0.0 B)TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0[root@mcwk8s03 mcwtest]# [root@mcwk8s05 /]# ifconfig docker
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450inet 172.17.98.1  netmask 255.255.255.0  broadcast 172.17.98.255inet6 fe80::42:18ff:fee1:e8fc  prefixlen 64  scopeid 0x20<link>ether 02:42:18:e1:e8:fc  txqueuelen 0  (Ethernet)RX packets 548174  bytes 215033771 (205.0 MiB)RX errors 0  dropped 0  overruns 0  frame 0TX packets 632239  bytes 885330301 (844.3 MiB)TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0[root@mcwk8s05 /]# [root@mcwk8s06 ~]# ifconfig docker
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450inet 172.17.9.1  netmask 255.255.255.0  broadcast 172.17.9.255inet6 fe80::42:f0ff:fefa:133e  prefixlen 64  scopeid 0x20<link>ether 02:42:f0:fa:13:3e  txqueuelen 0  (Ethernet)RX packets 229  bytes 31724 (30.9 KiB)RX errors 0  dropped 0  overruns 0  frame 0TX packets 212  bytes 53292 (52.0 KiB)TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0[root@mcwk8s06 ~]# 可以看到，05宿主机是不通其他机器的docker0的，03 06是互通的
[root@mcwk8s05 /]# ping -c 1 172.17.83.1
PING 172.17.83.1 (172.17.83.1) 56(84) bytes of data.
^C
--- 172.17.83.1 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms[root@mcwk8s05 /]# ping -c 1 172.17.9.1
PING 172.17.9.1 (172.17.9.1) 56(84) bytes of data.
^C
--- 172.17.9.1 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms[root@mcwk8s05 /]# [root@mcwk8s06 ~]# ping -c 1 172.17.83.1
PING 172.17.83.1 (172.17.83.1) 56(84) bytes of data.
64 bytes from 172.17.83.1: icmp_seq=1 ttl=64 time=0.246 ms--- 172.17.83.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.246/0.246/0.246/0.000 ms
[root@mcwk8s06 ~]#

【4】可以看到，etcd里面，没有005宿主机的docker网段的

[root@mcwk8s03 mcwtest]# etcdctl ls /coreos.com/network/subnets
/coreos.com/network/subnets/172.17.9.0-24
/coreos.com/network/subnets/172.17.83.0-24
[root@mcwk8s03 mcwtest]# etcdctl get /coreos.com/network/subnets/172.17.9.0-24
{"PublicIP":"10.0.0.36","BackendType":"vxlan","BackendData":{"VtepMAC":"2a:2c:21:3a:58:21"}}
[root@mcwk8s03 mcwtest]# etcdctl get /coreos.com/network/subnets/172.17.83.0-24
{"PublicIP":"10.0.0.33","BackendType":"vxlan","BackendData":{"VtepMAC":"b2:83:33:7b:fd:37"}}
[root@mcwk8s03 mcwtest]#

【5】重启005的flannel服务，如果不重启docker0,那么网络就会有点问题，docker0不会被分配新的网段IP

[root@mcwk8s05 ~]# systemctl restart flanneld.service 
[root@mcwk8s05 ~]# ifconfig flannel.1
flannel.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450inet 172.17.89.0  netmask 255.255.255.255  broadcast 0.0.0.0inet6 fe80::3470:76ff:feea:39b8  prefixlen 64  scopeid 0x20<link>ether 36:70:76:ea:39:b8  txqueuelen 0  (Ethernet)RX packets 1  bytes 40 (40.0 B)RX errors 0  dropped 0  overruns 0  frame 0TX packets 9  bytes 540 (540.0 B)TX errors 0  dropped 8 overruns 0  carrier 0  collisions 0[root@mcwk8s05 ~]# ifconfig docker
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450inet 172.17.98.1  netmask 255.255.255.0  broadcast 172.17.98.255inet6 fe80::42:18ff:fee1:e8fc  prefixlen 64  scopeid 0x20<link>ether 02:42:18:e1:e8:fc  txqueuelen 0  (Ethernet)RX packets 551507  bytes 216568663 (206.5 MiB)RX errors 0  dropped 0  overruns 0  frame 0TX packets 635860  bytes 891305864 (850.0 MiB)TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0[root@mcwk8s05 ~]# systemctl restart docker
[root@mcwk8s05 ~]# ifconfig docker
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450inet 172.17.89.1  netmask 255.255.255.0  broadcast 172.17.89.255inet6 fe80::42:18ff:fee1:e8fc  prefixlen 64  scopeid 0x20<link>ether 02:42:18:e1:e8:fc  txqueuelen 0  (Ethernet)RX packets 552135  bytes 216658479 (206.6 MiB)RX errors 0  dropped 0  overruns 0  frame 0TX packets 636771  bytes 892057926 (850.7 MiB)TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0[root@mcwk8s05 ~]#

【6】再次查看，etcd已经有了05节点的这个网段了

[root@mcwk8s03 mcwtest]# etcdctl ls /coreos.com/network/subnets
/coreos.com/network/subnets/172.17.83.0-24
/coreos.com/network/subnets/172.17.9.0-24
/coreos.com/network/subnets/172.17.89.0-24
[root@mcwk8s03 mcwtest]# etcdctl get /coreos.com/network/subnets/172.17.89.0-24
{"PublicIP":"10.0.0.35","BackendType":"vxlan","BackendData":{"VtepMAC":"36:70:76:ea:39:b8"}}
[root@mcwk8s03 mcwtest]#

【7】再次测试，05节点的，可以nodeport访问到了

[root@mcwk8s03 mcwtest]# kubectl get svc
NAME          TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.2.0.1     <none>        443/TCP          583d
mcwtest-svc   NodePort    10.2.0.155   <none>        2024:33958/TCP   154m
nginx         ClusterIP   None         <none>        80/TCP           413d
[root@mcwk8s03 mcwtest]# curl -I 10.2.0.155:2024
curl: (7) Failed connect to 10.2.0.155:2024; Connection timed out
[root@mcwk8s03 mcwtest]# curl -I 10.0.0.33:33958
curl: (7) Failed connect to 10.0.0.33:33958; Connection refused
[root@mcwk8s03 mcwtest]# curl -I 10.0.0.35:33958
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.7.18
Date: Tue, 04 Jun 2024 16:59:03 GMT
Content-type: text/html; charset=ANSI_X3.4-1968
Content-Length: 816[root@mcwk8s03 mcwtest]# curl -I 10.0.0.36:33958
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.7.18
Date: Tue, 04 Jun 2024 16:59:12 GMT
Content-type: text/html; charset=ANSI_X3.4-1968
Content-Length: 816[root@mcwk8s03 mcwtest]#

【8】03节点不通，可能是03是master，但是它本身好像不作为node,就是个单纯的master，所以没法当做nodeIP去访问。但是集群IP，无法访问，是怎么回事呢

[root@mcwk8s03 mcwtest]# kubectl get svc
NAME          TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.2.0.1     <none>        443/TCP          583d
mcwtest-svc   NodePort    10.2.0.155   <none>        2024:33958/TCP   157m
nginx         ClusterIP   None         <none>        80/TCP           413d
[root@mcwk8s03 mcwtest]# kubectl get nodes
NAME       STATUS   ROLES    AGE    VERSION
mcwk8s05   Ready    <none>   580d   v1.15.12
mcwk8s06   Ready    <none>   580d   v1.15.12
[root@mcwk8s03 mcwtest]#

【9】路由方面，重启flannel，etcd里面会重新写入新的网段，并且其他节点也会有这个新的网段的路由，需要重启该宿主机的docker，给容器重新分配新的IP用吧，应该。

之前03 master只有一个flanel的路由，

[root@mcwk8s03 mcwtest]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.9.0      172.17.9.0      255.255.255.0   UG    0      0        0 flannel.1
172.17.83.0     0.0.0.0         255.255.255.0   U     0      0        0 docker0
[root@mcwk8s03 mcwtest]#05 node重启之后，03上多出来一个05 node的flannel路由，
[root@mcwk8s03 mcwtest]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.9.0      172.17.9.0      255.255.255.0   UG    0      0        0 flannel.1
172.17.83.0     0.0.0.0         255.255.255.0   U     0      0        0 docker0
172.17.89.0     172.17.89.0     255.255.255.0   UG    0      0        0 flannel.1
[root@mcwk8s03 mcwtest]# 06好的node也是如此
之前：
[root@mcwk8s06 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.9.0      0.0.0.0         255.255.255.0   U     0      0        0 docker0
172.17.83.0     172.17.83.0     255.255.255.0   UG    0      0        0 flannel.1
[root@mcwk8s06 ~]# 
操作之后，多了个路由
[root@mcwk8s06 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.9.0      0.0.0.0         255.255.255.0   U     0      0        0 docker0
172.17.83.0     172.17.83.0     255.255.255.0   UG    0      0        0 flannel.1
172.17.89.0     172.17.89.0     255.255.255.0   UG    0      0        0 flannel.1
[root@mcwk8s06 ~]# 05node之前是有两个路由，但是都是错误的
[root@mcwk8s05 /]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.59.0     172.17.59.0     255.255.255.0   UG    0      0        0 flannel.1
172.17.61.0     172.17.61.0     255.255.255.0   UG    0      0        0 flannel.1
172.17.98.0     0.0.0.0         255.255.255.0   U     0      0        0 docker0
[root@mcwk8s05 /]#05重启之后，也更新了路由为正确的
[root@mcwk8s05 /]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.254      0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
172.17.9.0      172.17.9.0      255.255.255.0   UG    0      0        0 flannel.1
172.17.83.0     172.17.83.0     255.255.255.0   UG    0      0        0 flannel.1
172.17.89.0     0.0.0.0         255.255.255.0   U     0      0        0 docker0
[root@mcwk8s05 /]#

【10】然后看看集群IP为啥不通，这直接原因应该是没有ipvs规则。

[root@mcwk8s03 mcwtest]# kubectl get svc
NAME          TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.2.0.1     <none>        443/TCP          583d
mcwtest-svc   NodePort    10.2.0.155   <none>        2024:33958/TCP   3h3m
nginx         ClusterIP   None         <none>        80/TCP           413d
[root@mcwk8s03 mcwtest]# curl -I 10.2.0.155:2024 
curl: (7) Failed connect to 10.2.0.155:2024; Connection timed out
[root@mcwk8s03 mcwtest]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
[root@mcwk8s03 mcwtest]# systemctl status kube-proxy
Unit kube-proxy.service could not be found.
[root@mcwk8s03 mcwtest]# 其它节点都是有ipvs规则的，有时间确认下，ipvsadm规则是哪个服务创建的，应该是kube-proxy创建的吧，我们的03 master是没有部署kube-proxy，这样的话，没有ipvs规则并且无法在master上访问集群IP就说的通了。如过是这样的话，也就是容器集群IP之间的通信，跟ipvs有关，跟apiserver是否挂了没有直接关系，不影响，有时间验证
[root@mcwk8s05 /]# ipvsadm -Ln|grep -C 1 10.2.0.155-> 172.17.89.4:9090             Masq    1      0          0         
TCP  10.2.0.155:2024 rr-> 172.17.89.10:20000           Masq    1      0          0         
[root@mcwk8s05 /]# 
[root@mcwk8s05 /]# curl -I 10.2.0.155:2024
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.7.18
Date: Tue, 04 Jun 2024 17:34:45 GMT
Content-type: text/html; charset=ANSI_X3.4-1968
Content-Length: 816[root@mcwk8s05 /]#

【综上】

单节点的容器网络用nodeIP：nodeport等之类的用不了了，可以优先检查下docker0 网关是不是不通了；如果flannel等网络服务重启之后，即使是pod方式部署的网络插件，也要看下重启docker服务，让容器分配新的网段。比如某次flannel oom总是重启，导致kube001网络故障;每个机器，好像都有其他节点的flannel.1网卡网段的路由，使用当前机器的flannel.1的网卡接口；并且有当前节点docker0网段的路由，是走的 0.0.0.0网关，走默认路由由上面可以知道，svc里面有个是clusterIP用的端口，clusterIP是用ipvs规则管理，进行数据转发的；nodeip clusterIP的ipvs规则进行转发，因为转发到后端容器IP，当前宿主机有所有node的flannel网段的路由，所有flannel网关以及docker0都正常且对应网段的话，那么就是用这两个接口实现容器跨宿主机通信的。而至于访问nodeip:nodeport以及clusterIP：port是怎么知道把流量给到正确的pod的，这里是通过ipvs规则来实现寻找到后端pod的，转发到pod对应的IP和端口的时候，又根据当前机器有所有网络插件flannel，也就是每个宿主机单独网段的路由条目，让它们知道自己要去走flannel.1接口。而etcd保存有哪个网段是哪个宿主机，有对应宿主机IP，找到宿主机IP了，那么在该机器上转发到的pod机器，在那个宿主机上就是能用该IP，使用docker0进行通信的，因为单个宿主机上的容器，都是通过docker0进行通信，并且互通的。只有跨宿主机通信容器的时候，才会根据路由，找到flannel.1接口，然后在etcd找到是那个宿主机上的容器，然后找到这个容器，完成通信。flannel网络插件这样，其它网络插件原理类似；ipvs网络代理模式是这个作用，iptables网络代理模式作用类似。

文章转载自：马昌伟

原文链接：https://www.cnblogs.com/machangwei-8/p/18236417

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