P4 learning - p4runtime

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Reference resources ：https://blog.csdn.net/qq_33681684/article/details/123646883

In this exercise , We will use P4Runtime Send stream entries to the switch , Instead of using switches CLI. We will be based on your basic_tunnel The same used in the exercise P4 Program to build .P4 The program has been renamed to advanced_tunnel.p4 And added two counters (ingressTunnelCounter, egressTunnelCounter) And two new moves (myTunnel_ingress, myTunnel_egress).

You will use starter Program mycontroller.py and p4runtime_lib Directory to create the host 1 And host 2 Table entries required for channel communication between .

Description of the control plane
P4 The program defines a package processing pipeline , But the rules in each table are inserted by the control plane . In this case ,mycontroller.py Realized our control plane , Instead of installing static table entries as we did in the previous exercise .

Important note : One .p4 The file will be compiled to generate a Info The document contains table id Such information is the basis for the control plane to issue specific rules ; Regenerate into a configuration file （ Format according to target And decide ） Send the data plane as a packet processing pipeline. The control plane also passes through p4runtime Data plane management .

Step one ： Run incomplete code

• sudo make run （ compile advanced_tunnel.p4, start-up mininet Instance building topology , by hosts Distribute IP）
  
• h1 ping h2, Normal communication is not available at this time , Because there are no rules on the switch at this time , So I can't receive any reply
  
• Open another terminal , function mycontroller.py. This will install advanced_tunnel.p4 Program and load on the switch tunnel ingress rules. The program every 2 Print once per second tunnel ingress and egres Count . You should see s1 Of tunnel ingress The counter is increasing ：
  because s1 and s2 Between transit rules Not yet , So I can only see s1 Enter tunnel count .
  
• Ctrl-C stop it mycontroller.py, complete switches The flow between is based on the tunnel ID forwarding rules. open mycontroller.py, complete TODO part . At present, every switch is in accordance with the purpose IP Address maps traffic into the tunnel . The goal is to write a tunnel based ID Rules for forwarding traffic between switches .

Step two ： Start to realize tunnel forwarding

mycontroller.py Is a basic control plane , It will do the following ：
1. by P4Runtime Service establishment to switches Of gRPC Connect ;
2.Pushes the P4 program to each switch. push P4 Program to each switches;
3. by h1 To h2 Write rules for the two tunnels between ,h1 To h2 Tunnel ID 100,h2 To h1 Tunnel ID 200;
4. Every time 2 Read once per second tunnel ingress and egress Count of .

Work will be on writeTunnelRules Function to write tunnel transmission rules , This function will match the tunnel ID And forward the packet to the next hop .

In the experiment , Will use p4runtime_lib Some classes and methods under ：
helper.py
Contains for parsing p4info Of documents P4InfoHelper class .
Provide entity name and ID The transformation method of .
structure P4Runtime table Of P4 Relevant parts of the program .

switch.py
contain SwitchConnection class , This class gets gRPC client stub, And establish a connection to the switch .
Provide helper Method , Is used to construct P4Runtime The protocol buffer messages are and processed P4Runtime gRPC The service call

bmv2.py
contain Bmv2SwitchConnection, It expands SwitchConnections, And provide BMv2 Specific equipment loads to load P4 Program .

convert.py
Provide a convenient way , take friendly String and number encoding 、 Byte string required to decode into protocol buffer message .
Helper.py Use

Step three ： Run the solution

Open another terminal to execute python file , The control plane will rules Distribute to the data plane . Then you will see the count increase
./my_controller.py

At this time, log in through the command line s1, look down switch The forwarding rules are as follows ：
simple_switch_CLI --thrift-port 9090

Purpose IP10.0.2.2/32 Conduct LPM matching , Into the tunnel 100（ According to the 64 It's hexadecimal ）.
Exactly match the tunnel ID100, To the interface 2.
Tunnel ID yes 200（ Show c8 It's hexadecimal ）, encapsulation 08–0111 Of h1 Of Mac, To the interface 1.