P4 Switch (program protocol independent packer processor )-I

P4 advantages：

Program protocol (P4 programs specify how a switch processes packets.)Target independent (P4 is suitable for describing everything from high- performance forwarding ASICs to software switches.)Field Reconfigurable (P4 allows network engineers to change the way their switches process packets after they are deployed.)

Environment on ubuntu 18.04 (password:ubuntu)

sudo apt-get install git curl wget gedit -ygit clone https://github.com/mininet/mininet.gitcd mininetutil/install.sh -a      //install all the packets

you need to try to install :

https://github.com/p4lang/behavioral-model (behavioral-model is a software platform to run the p4)https://github.com/p4lang/p4c (Compile the p4 program)https://github.com/nsg-ethz/p4-utils

some example and tutorials:
https://github.com/nsg-ethz/p4-learning

Review the basic topology of mininet:
h1----h2

#!/usr/bin/pythonfrom mininet.net import Mininetfrom mininet.node import Hostfrom mininet.cli import CLIfrom mininet.link import TCLink, Intffrom mininet.log import setLogLevel, infofrom subprocess import calldef myNetwork():    net = Mininet()            //Step3.    h2 = net.addHost('h2')     //Step4.    h1 = net.addHost('h1')     //Step5.     info( '*** Add links\n')       net.addLink(h1, h2)        //Step6.    info( '*** Starting network\n')     net.build()                //Step7.    CLI(net)                   //Step8. CLI means command line interface.    net.stop()if __name__ == '__main__':     // Step1.Start from here!!!    setLogLevel( 'info' )    myNetwork()                // Step2.

Let's write the first p4 program
H1----H2 let h1 can ping h2
Parser-->Ingress-->Egress-->Deparser
you need three files: basic.p4 cmd.txt p4app.json

1.basic.p4

/* -*- P4_16 -*- */#include <core.p4>#include <v1model.p4>/************************************************************************************************ H E A D E R S  ************************************************************************************************************/ struct metadata {    /* empty */} struct headers {} /************************************************************************************************ P A R S E R  ************************************************************************************************************/parser MyParser(packet_in packet,                out headers hdr,                inout metadata meta,                inout standard_metadata_t standard_metadata) {    state start {        transition accept;       //---->Analysis of the end    }} /*************************************************************************************   C H E C K S U M    V E R I F I C A T I O N   **************************************************************************************/ control MyVerifyChecksum(inout headers hdr, inout metadata meta) {      apply {  }}/***************************************************************************************  I N G R E S S   P R O C E S S I N G   ********************************************************************************************/control MyIngress(inout headers hdr,                  inout metadata meta,                  inout standard_metadata_t standard_metadata) {    action drop() {        mark_to_drop(standard_metadata);    }    action forward(bit<9> port) {        standard_metadata.egress_spec = port;      }    table phy_forward {                     //phy_forward is table name        key = {            standard_metadata.ingress_port: exact;   //The system itself has a variable that stores which packets come in from which packets.        }        actions = {            forward;            drop;        }        size = 1024;                       //1024 means this table can store 1024 rules         default_action = drop();           //If the packet does not find a matching rule, throw it away    apply {        phy_forward.apply();    }}/*****************************************************************************************  E G R E S S   P R O C E S S I N G   ********************************************************************************************/control MyEgress(inout headers hdr,                 inout metadata meta,                 inout standard_metadata_t standard_metadata) {    apply {  }}/**************************************************************************************   C H E C K S U M    C O M P U T A T I O N   ***************************************************************************************/control MyComputeChecksum(inout headers  hdr, inout metadata meta) {     apply {    }}/************************************************************************************************  D E P A R S E R  ********************************************************************************************************/control MyDeparser(packet_out packet, in headers hdr) {    apply {    }}/************************************************************************************************  S W I T C H  ********************************************************************************************************/V1Switch(MyParser(),MyVerifyChecksum(),MyIngress(),MyEgress(),MyComputeChecksum(),MyDeparser()) main;

2.cmd.txt

table_add phy_forward forward 1 => 2table_add phy_forward forward 2 => 1

3.p4app.json

{  "program": "basic.p4",  "switch": "simple_switch",  "compiler": "p4c",  "options": "--target bmv2 --arch v1model --std p4-16",  "switch_cli": "simple_switch_CLI",  "cli": true,  "pcap_dump": true,  "enable_log": true,  "topo_module": {    "file_path": "",    "module_name": "p4utils.mininetlib.apptopo",    "object_name": "AppTopoStrategies"  },  "controller_module": null,  "topodb_module": {    "file_path": "",    "module_name": "p4utils.utils.topology",    "object_name": "Topology"  },  "mininet_module": {    "file_path": "",    "module_name": "p4utils.mininetlib.p4net",    "object_name": "P4Mininet"  },  "topology": {                             //You can start here!!!    "links": [["h1", "s1"], ["h2", "s1"]],    "hosts": {      "h1": {      },      "h2": {      }    },    "switches": {      "s1": {        "cli_input": "cmd.txt",        "program": "basic.p4"      }    }  }}

you can use p4run to run the program, also you can use this command simple_switch_CLI --thrift-port 9090 to dynamically change packet forwarding rules.