Record a troubleshooting of 8472 port conflict in k8s vxlan overlay network

chanjarster 2020-11-10 11:25:00
record troubleshooting port conflict k8s


Environmental Science

The server :172.17.17.20-22 Three servers ( Convinced aCloud Virtualization platform )

Operating system version :CentOS 7.8

Kernel version :3.10

The phenomenon

stay 20-22 Install on three platforms K8S colony ( adopt rancher Of rke install ), After installation , Find access to each node 80 port , Only 20 The server can return normally , The rest are Gateway Timeout. Use Rancher That's what we're offering hear Overlay The Internet is not working .

The screening process

Check network connectivity

according to Rancher It's mentioned in the document ,Host Of 8472/udp The port is Flannel/Calico Of VXLAN Overlay Network private port , That is, all cross Host The network communication between containers goes through this port . therefore :

stay 172.17.17.22 On , use tcpdump Grab the bag that was sent out :

tcpdump -nn 'udp and src host 172.17.17.22 and dst port 8472'

Open another one 22 Terminal , perform curl http://localhost Be able to see 22->20 Of UDP package , See the picture below :

tcpdump-1.jpg

stay 172.17.17.20 On , use tcpdump Grab the bag you received :

tcpdump -nn 'udp and src host 172.17.17.22 and dst port 8472'

It turns out that no bags have been caught .

Check the virtual machine network security group

Reasonably suspect that the virtual machine network security group has not been released 8472/udp Port access rights , stay 22 Upper use netcat send data :

nc -u 172.17.17.20 8472

Random typing, carriage return transmission , Here's the picture :

image.png

It turns out that 20 You can catch the bag you've received :

image.png

This shows that the network security group is not blocking 8472/udp Port access .

Preliminary assumption

It is suspected that the data are convincing aCloud The network of virtualization platform is filtered out . For the following reasons :

  1. k8s The use is based on VXLAN Of Overlay network,VNI=1, And based on UDP agreement . And deeply convinced aCloud High probability also uses VXLAN do Overlay The Internet .
  2. ordinary udp Protocol data transfer tcpdump Be able to catch a bag ( See front )
  3. tcpdump Position in the network stack inbound stay iptables Before ,outbound stay iptables after ( Information ). If tcpdump Be able to catch the bag that's coming out , So the statement is really sent out . If inbound Didn't catch the accepted bag , So it means that the packet did not arrive at the network card .

terms of settlement

After communicating with deeply convinced students , It was confirmed that the physical machine was also used 8472/udp Port to do Overlay The Internet , The two are in conflict , So when UDP The bag contains OTV After the data content , First of all, be aCloud Intercept , The result is virtual machine 8472/udp The port can't receive data .

Will the physical machine's 8472/udp After the port is changed , Problem solving .

PS. 8472/udp Or a Famous port

terms of settlement 2

It can also be in rke establish k8s Modify when clustering flannel The port of , Need modification cluster.yml( Reference documents ).

If you're using a canal The network plugin ( Default ):

...
network:
plugin: canal
options:
canal_flannel_backend_type: vxlan
canal_flannel_backend_port: "8872"
...

If I use theta flannel The network plugin :

...
network:
plugin: flannel
options:
flannel_backend_type: vxlan
flannel_backend_port: "8872"
...

stay Rancher When creating a custom cluster in , You need to customize the cluster parameters to modify the port ( Reference documents ).

If I use theta canal The network plugin ( Default ):

rancher_kubernetes_engine_config:
...
network:
options:
flannel_backend_type: vxlan
flannel_backend_port: "8872"
plugin: canal

If I use theta flannel The network plugin :

rancher_kubernetes_engine_config:
...
network:
options:
flannel_backend_type: vxlan
flannel_backend_port: "8872"
plugin: flannel
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