# 網路模擬與分析(5/10): P4
###### tags: `Mininet`、`P4`

---

**--------------目前為純 code 及 result，詳解部分之後更新--------------**

---
## Physical Layer Forwarding


p4-utils 框架需要: `basic.p4`、`p4app.json`和`cmd.txt`

/* -*- 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;
    }

    # 定義table
    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;

{
  "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"
      }
    }
  }
}

# 執行動作/表格名稱/執行動作/匹配 => 執行動作
table_add phy_forward forward 1 => 2
table_add phy_forward forward 2 => 1

執行`p4run`

h1 ping h2


開啟另一台終端機使用`simple_switch_CLI --thrift-port 9090`

進入後使用`table_info phy_forward`去查看所有資訊

使用`table_dump phy_forward`查看規則表

---

### Physical Forwaring 延伸

`gedit p4app.json basic.p4`

{

  "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"

      }	

    }

  }

}

使用`p4run`

進入後使用`h1 ping h2 -c 5`

---

## Reference

1. https://kknews.cc/zh-tw/tech/jkxkk4q.html
2. https://dl.acm.org/doi/10.1145/2656877.2656890
3. https://www.youtube.com/watch?v=euDS8MHaW3I&feature=emb_title
4. https://www.youtube.com/watch?v=QbTboYkIBjE
5. https://github.com/nsg-ethz/p4-utils
6. http://csie.nqu.edu.tw/smallko/sdn/p4utils-basic.htm
7. http://csie.nqu.edu.tw/smallko/sdn/p4_forwarding.htm