root@ubuntu:~# kubectl get svc
NAME          TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.96.0.1        <none>        443/TCP          243d
my-nginx      ClusterIP   10.110.79.116    <none>        8280/TCP         35d
my-nginx-np   NodePort    10.99.1.231      <none>        8081:31199/TCP   35d
web2          NodePort    10.110.171.213   <none>        8097:31866/TCP   19d
root@ubuntu:~# kubectl get svc my-nginx-np -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"run":"my-nginx"},"name":"my-nginx-np","namespace":"default"},"spec":{"ports":[{"nodePort":31199,"port":8080,"protocol":"TCP","targetPort":80}],"selector":{"run":"my-nginx"},"type":"NodePort"},"status":{"loadBalancer":{}}}
  creationTimestamp: "2021-05-12T08:39:09Z"
  labels:
    run: my-nginx
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .: {}
          f:kubectl.kubernetes.io/last-applied-configuration: {}
        f:labels:
          .: {}
          f:run: {}
      f:spec:
        f:externalTrafficPolicy: {}
        f:ports:
          .: {}
          k:{"port":8081,"protocol":"TCP"}:
            .: {}
            f:nodePort: {}
            f:port: {}
            f:protocol: {}
            f:targetPort: {}
        f:selector:
          .: {}
          f:run: {}
        f:sessionAffinity: {}
        f:type: {}
    manager: kubectl
    operation: Update
    time: "2021-05-12T08:47:48Z"
  name: my-nginx-np
  namespace: default
  resourceVersion: "39417422"
  selfLink: /api/v1/namespaces/default/services/my-nginx-np
  uid: 1ef49071-e7b5-4a92-8785-b5158606731e
spec:
  clusterIP: 10.99.1.231
  externalTrafficPolicy: Cluster
  ports:
  - nodePort: 31199
    port: 8081
    protocol: TCP
    targetPort: 80
  selector:
    run: my-nginx
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}
root@ubuntu:~# 

root@ubuntu:~# kubectl get pod 
NAME                                READY   STATUS             RESTARTS   AGE
debian-6c44fc6956-ltsrt             0/1     CrashLoopBackOff   4773       16d
mc1                                 2/2     Running            0          16d
my-deployment-68bdbbb5cc-bbszv      0/1     ImagePullBackOff   0          35d
my-deployment-68bdbbb5cc-nrst9      0/1     ImagePullBackOff   0          35d
my-deployment-68bdbbb5cc-rlgzt      0/1     ImagePullBackOff   0          35d
my-nginx-5dc4865748-jqx54           1/1     Running            2          35d
my-nginx-5dc4865748-pcrbg           1/1     Running            2          35d
nginx                               0/1     ImagePullBackOff   0          35d
nginx-deployment-6b474476c4-r6z5b   1/1     Running            0          8d
nginx-deployment-6b474476c4-w6xh9   1/1     Running            0          8d
web2-6d784f67bf-4gqq2               1/1     Running            0          19d
root@ubuntu:~# 

root@ubuntu:~# kubectl -n  default     describe pod  my-nginx-5dc4865748-jqx54 | grep  Container
Containers:
    Container ID:   containerd://270994804d4c87638dcfd98a9ca1489f8c268998a0930cc5d3eef52887797777
  ContainersReady   True 
root@ubuntu:~# kubectl -n  default     describe pod  my-nginx-5dc4865748-pcrbg | grep  Container
Containers:
    Container ID:   containerd://7617bb50d622d23fb26feaffba96c832ea53d48bad66502e18dd4f77480d3d98
  ContainersReady   True 
root@ubuntu:~# 

root@ubuntu:~#  crictl inspect 270994804d4c87638dcfd98a9ca1489f8c268998a0930cc5d3eef52887797777 | grep -i pid
    "pid": 27134,
            "pid": 1
            "type": "pid"
root@ubuntu:~#  crictl inspect 7617bb50d622d23fb26feaffba96c832ea53d48bad66502e18dd4f77480d3d98 | grep -i pid
    "pid": 27324,
            "pid": 1
            "type": "pid"
root@ubuntu:~# 

从客户端ping

root@cloud:~# telnet 10.10.16.82  31199
Trying 10.10.16.82...
Connected to 10.10.16.82.
Escape character is '^]'.
^CConnection closed by foreign host.
root@cloud:~# telnet 10.10.16.82  31199
Trying 10.10.16.82...
Connected to 10.10.16.82.
Escape character is '^]'.
^CConnection closed by foreign host.
root@cloud:~# 

root@ubuntu:~# nsenter -n --target  27134 
root@ubuntu:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0@if641: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default 
    link/ether fa:66:b3:ab:05:9f brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.244.0.19/24 brd 10.244.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::f866:b3ff:feab:59f/64 scope link 
       valid_lft forever preferred_lft forever
root@ubuntu:~# tcpdump -i eth0 icmp -nnvv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
^C
0 packets captured
0 packets received by filter
0 packets dropped by kernel
root@ubuntu:~# tcpdump -i eth0 tcp -nnvv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
09:25:08.212080 IP (tos 0x10, ttl 63, id 25166, offset 0, flags [DF], proto TCP (6), length 60)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [S], cksum 0x0331 (correct), seq 1619805106, win 64240, options [mss 1460,sackOK,TS val 3487078452 ecr 0,nop,wscale 7], length 0

root@ubuntu:~# nsenter -n --target  27324 
root@ubuntu:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0@if642: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default 
    link/ether 6e:5a:30:bc:6d:5b brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.244.0.20/24 brd 10.244.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6c5a:30ff:febc:6d5b/64 scope link 
       valid_lft forever preferred_lft forever
root@ubuntu:~# tcpdump -i eth0 icmp -nnvv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
^C
0 packets captured
0 packets received by filter
0 packets dropped by kernel
root@ubuntu:~# tcpdump -i eth0 tcp -nnvv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
09:25:08.212027 IP (tos 0x10, ttl 63, id 25166, offset 0, flags [DF], proto TCP (6), length 60)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [S], cksum 0x0331 (correct), seq 1619805106, win 64240, options [mss 1460,sackOK,TS val 3487078452 ecr 0,nop,wscale 7], length 0
09:25:08.212074 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 60)
    10.244.0.20.80 > 10.244.0.1.10054: Flags [S.], cksum 0x162b (incorrect -> 0x6794), seq 465847927, ack 1619805107, win 64308, options [mss 1410,sackOK,TS val 2479727984 ecr 3487078452,nop,wscale 7], length 0
09:25:08.212185 IP (tos 0x10, ttl 63, id 25167, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [.], cksum 0x8f6c (correct), seq 1, ack 1, win 502, options [nop,nop,TS val 3487078453 ecr 2479727984], length 0
09:25:13.484043 IP (tos 0x10, ttl 63, id 25168, offset 0, flags [DF], proto TCP (6), length 57)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [P.], cksum 0x74d4 (correct), seq 1:6, ack 1, win 502, options [nop,nop,TS val 3487083725 ecr 2479727984], length 5: HTTP
09:25:13.484079 IP (tos 0x0, ttl 64, id 51806, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.20.80 > 10.244.0.1.10054: Flags [.], cksum 0x1623 (incorrect -> 0x6636), seq 1, ack 6, win 503, options [nop,nop,TS val 2479733256 ecr 3487083725], length 0
09:25:13.484223 IP (tos 0x0, ttl 64, id 51807, offset 0, flags [DF], proto TCP (6), length 363)
    10.244.0.20.80 > 10.244.0.1.10054: Flags [P.], cksum 0x175a (incorrect -> 0x1b1c), seq 1:312, ack 6, win 503, options [nop,nop,TS val 2479733257 ecr 3487083725], length 311: HTTP, length: 311
        HTTP/1.1 400 Bad Request
        Server: nginx/1.19.10
        Date: Thu, 17 Jun 2021 01:25:13 GMT
        Content-Type: text/html
        Content-Length: 158
        Connection: close

        <html>
        <head><title>400 Bad Request</title></head>
        <body>
        <center><h1>400 Bad Request</h1></center>
        <hr><center>nginx/1.19.10</center>
        </body>
        </html>
09:25:13.484321 IP (tos 0x0, ttl 64, id 51808, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.20.80 > 10.244.0.1.10054: Flags [F.], cksum 0x1623 (incorrect -> 0x64fd), seq 312, ack 6, win 503, options [nop,nop,TS val 2479733257 ecr 3487083725], length 0
09:25:13.484367 IP (tos 0x10, ttl 63, id 25169, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [.], cksum 0x6500 (correct), seq 6, ack 312, win 501, options [nop,nop,TS val 3487083725 ecr 2479733257], length 0
09:25:13.484412 IP (tos 0x10, ttl 63, id 25170, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.10054 > 10.244.0.20.80: Flags [F.], cksum 0x64fe (correct), seq 6, ack 313, win 501, options [nop,nop,TS val 3487083725 ecr 2479733257], length 0
09:25:13.484427 IP (tos 0x0, ttl 64, id 51809, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.20.80 > 10.244.0.1.10054: Flags [.], cksum 0x1623 (incorrect -> 0x64fc), seq 313, ack 7, win 503, options [nop,nop,TS val 2479733257 ecr 3487083725], length 0

再telnet 一次

root@cloud:~# telnet 10.10.16.82  31199
Trying 10.10.16.82...
Connected to 10.10.16.82.
Escape character is '^]'.
^CConnection closed by foreign host.
root@cloud:~#

root@ubuntu:~# nsenter -n --target  27134 
root@ubuntu:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0@if641: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default 
    link/ether fa:66:b3:ab:05:9f brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.244.0.19/24 brd 10.244.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::f866:b3ff:feab:59f/64 scope link 
       valid_lft forever preferred_lft forever

09:27:27.397163 IP (tos 0x10, ttl 63, id 60223, offset 0, flags [DF], proto TCP (6), length 60)
    10.244.0.1.28407 > 10.244.0.19.80: Flags [S], cksum 0x6fd3 (correct), seq 882875289, win 64240, options [mss 1460,sackOK,TS val 3487217637 ecr 0,nop,wscale 7], length 0
09:27:27.397214 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 60)
    10.244.0.19.80 > 10.244.0.1.28407: Flags [S.], cksum 0x162a (incorrect -> 0xceca), seq 1817758467, ack 882875290, win 64308, options [mss 1410,sackOK,TS val 1135551962 ecr 3487217637,nop,wscale 7], length 0
09:27:27.397305 IP (tos 0x10, ttl 63, id 60224, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.28407 > 10.244.0.19.80: Flags [.], cksum 0xf6a2 (correct), seq 1, ack 1, win 502, options [nop,nop,TS val 3487217638 ecr 1135551962], length 0
09:27:29.680979 IP (tos 0x10, ttl 63, id 60225, offset 0, flags [DF], proto TCP (6), length 57)
    10.244.0.1.28407 > 10.244.0.19.80: Flags [P.], cksum 0xe7b7 (correct), seq 1:6, ack 1, win 502, options [nop,nop,TS val 3487219921 ecr 1135551962], length 5: HTTP
09:27:29.681014 IP (tos 0x0, ttl 64, id 57110, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.19.80 > 10.244.0.1.28407: Flags [.], cksum 0x1622 (incorrect -> 0xe4c6), seq 1, ack 6, win 503, options [nop,nop,TS val 1135554245 ecr 3487219921], length 0
09:27:29.681118 IP (tos 0x0, ttl 64, id 57111, offset 0, flags [DF], proto TCP (6), length 363)
    10.244.0.19.80 > 10.244.0.1.28407: Flags [P.], cksum 0x1759 (incorrect -> 0x96a7), seq 1:312, ack 6, win 503, options [nop,nop,TS val 1135554245 ecr 3487219921], length 311: HTTP, length: 311
        HTTP/1.1 400 Bad Request
        Server: nginx/1.19.10
        Date: Thu, 17 Jun 2021 01:27:29 GMT
        Content-Type: text/html
        Content-Length: 158
        Connection: close

        <html>
        <head><title>400 Bad Request</title></head>
        <body>
        <center><h1>400 Bad Request</h1></center>
        <hr><center>nginx/1.19.10</center>
        </body>
        </html>
09:27:29.681157 IP (tos 0x0, ttl 64, id 57112, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.19.80 > 10.244.0.1.28407: Flags [F.], cksum 0x1622 (incorrect -> 0xe38e), seq 312, ack 6, win 503, options [nop,nop,TS val 1135554245 ecr 3487219921], length 0
09:27:29.681210 IP (tos 0x10, ttl 63, id 60226, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.28407 > 10.244.0.19.80: Flags [.], cksum 0xe390 (correct), seq 6, ack 312, win 501, options [nop,nop,TS val 3487219922 ecr 1135554245], length 0
09:27:29.681255 IP (tos 0x10, ttl 63, id 60227, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.1.28407 > 10.244.0.19.80: Flags [F.], cksum 0xe38e (correct), seq 6, ack 313, win 501, options [nop,nop,TS val 3487219922 ecr 1135554245], length 0
09:27:29.681270 IP (tos 0x0, ttl 64, id 57113, offset 0, flags [DF], proto TCP (6), length 52)
    10.244.0.19.80 > 10.244.0.1.28407: Flags [.], cksum 0x1622 (incorrect -> 0xe38b), seq 313, ack 7, win 503, options [nop,nop,TS val 1135554246 ecr 3487219922], length 0