20210510 Programming Protocol-independent Packet Processors ( P4 ) - 1

課堂資料

https://kknews.cc/zh-tw/tech/jkxkk4q.htmlkknews.cc

P4: programming protocol-independent packet processors: ACM SIGCOMM Computer Communication Review: Vol 44, No 3ACM SIGCOMM Computer Communication Review

GitHub - nsg-ethz/p4-utils: Extension to Mininet that makes P4 networks easier to buildGitHub

P4 是用於編程與協議無關的包處理器的高級語言，其與SDN控制協議（如 OpenFlow）結合使用，在當前形式下，OpenFlow 顯式指定其所操作的協議標頭

幾年來，這個集合已經從 12個字段 增加到 41個字段，這增加了規範的複雜性，同時仍然沒有提供添加新標頭的靈活性

我們有三個目標：

1. 現場可重配置性：程序員應該能夠在交換機部署數據包後改變交換機處理數據包的方式

2. 協議獨立性：交換機不應綁定到任何特定的網絡協議

3. 目標獨立性：程序員應該能夠獨立於底層硬件的細節來描述數據包處理功能

http://csie.nqu.edu.tw/smallko/sdn/p4utils-basic.htmcsie.nqu.edu.tw

http://csie.nqu.edu.tw/smallko/sdn/p4_forwarding.htmcsie.nqu.edu.tw

課堂練習

1

Terminal 01

cd p4-test/1

gedit p4app.json basic.p4 cmd.txt 

gedit

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": false,
  "enable_log": false,
  "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": {
    "links": [["h1", "s1"], ["h2", "s1"]],
    "hosts": {
      "h1": {
      },
      "h2": {
      }
    },
    "switches": {
      "s1": {
        "cli_input": "cmd.txt",
        "program": "basic.p4"
      }
    }
  }
}

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;
    }
}
 
/*************************************************************************
************   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 {
        key = {
            standard_metadata.ingress_port: exact;
        }
        actions = {
            forward;
            drop;
        }
        size = 1024;
        default_action = drop();
    }
    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;

cmd.txt

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

Terminal 02

cd 1

sed -i '/^$/d' p4app.json

sed -i '/^$/d' basic.p4

sed -i '/^$/d' cmd.txt

p4run

net

h1 ping h2 -c 5

table_clear phy_forward後

h1 ping h2 -c 5

table_add phy_forward後

h1 ping h2 -c 5

Terminal 03

simple_switch_CLI --thrift-port 9090

table_info phy_forward

table_dump phy_forward

table_clear phy_forward

table_dump phy_forward

table_add phy_forward forward 1 => 2

table_add phy_forward forward 2 => 1

table_dump phy_forward

cd ..

1 - 1

Terminal 01

cd 1-1

gedit p4app.json basic.p4

gedit

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": {
    "assignment_strategy": "l2", 

    "links": [["h1", "s1"], ["h2", "s2"], ["s1", "s2"]],

    "hosts": {

      "h1": {

      },

      "h2": {

      }

    },

    "switches": {

      "s1": {

        "cli_input":"cmd1.txt",
        "program": "basic.p4"

      },
      "s2": {

        "cli_input":"cmd2.txt",
        "program": "basic.p4"

      }	

    }

  }

}

Terminal 02

cd 1-1

p4run

h1 ping h2 -c 5

2

Terminal 01

cd p4-test

cd 2

誤關

gedit basic.p4 cmd.txt p4app.json

p4run

h1 ping h2 -c 5

變更mac_forward後

h1 ping h2 -c 5

gedit

basic.p4

/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>

/*************************************************************************
*********************** H E A D E R S  ***********************************
*************************************************************************/

header ethernet_t {
    bit<48> dstAddr;
    bit<48> srcAddr;
    bit<16>   etherType;
}

 
struct metadata {
    /* empty */
}

 

struct headers {
  ethernet_t   ethernet;
}

 

/*************************************************************************
*********************** 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 parse_ethernet;
    }

     state parse_ethernet {
        packet.extract(hdr.ethernet);
        transition accept;
     }	
}

 

/*************************************************************************

************   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 mac_forward {
        key = {
            hdr.ethernet.dstAddr: exact;
        }

        actions = {
            forward;
            drop;
        }
        size = 1024;
        default_action = drop();
    }

    apply {
        mac_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 {
      packet.emit(hdr.ethernet);
    }
}

/*************************************************************************
***********************  S W I T C H  *******************************
*************************************************************************/

V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()

) main;

cmd.txt

table_add mac_forward forward 00:00:0a:00:01:01 => 1
table_add mac_forward forward 00:00:0a:00:01:02 => 2

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": {
    "links": [["h1", "s1"], ["h2", "s1"]],
    "hosts": {
      "h1": {
      },
      "h2": {
      }
    },
    "switches": {
      "s1": {
        "cli_input": "cmd.txt",
        "program": "basic.p4"
      }
    }
  }
}

Terminal 02

simple_switch_CLI --thrift-port 9090

help

table_dump mac_forward

table_clear mac_forward

table_dump mac_forward

Terminal 01

ls

rm basic.p4i basic.json topology.db

rm -rf log pcap

ls

p4run

h1 ping h2 -c 5

變更mac_forward => 1後

h1 ping h2 -c 5

變更mac_forward => 2後

h1 ping h2 -c 5

exit

p4run

查看完log之後

h1 ping h2 -c 5

Terminal 02

simple_switch_CLI --thrift-port 9090

table_add mac_forward forward 00:00:0a:00:01:01 => 1

table_add mac_forward forward 00:00:0a:00:01:02 => 2

table_dump mac_forward

p4run 後

cd p4-test

cd 2

cd log

gedit s1.log