1, Experimental purpose

Master P4 under V1Model framework_ 16 program structure and basic syntax
Be able to use P4 for simple data plane programming

2, Experimental environment

Download the virtual machine software Oracle VisualBox or VMware;
Install Ubuntu 16.04 Desktop amd64 in the virtual machine, and install the complete Mininet and P4 development environment;
Provide P4 image P4-Suite2018.ova, extraction code: egwf

3, Experimental requirements

Learn the P4 official sample tutorial, link: https://github.com/p4lang/tutorials， Understand the basic syntax of P4-16 version and the P4 code structure based on V1Model, and complete the following exercises:

(1) Basic requirements

Be familiar with the basic forwarding principle of switch IPv4 using P4, write P4 program, and realize IPv4 tunnel forwarding in the following topology

• Supplement basic in P4 tutorial_ tunnel.p4

/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
const bit<16> TYPE_MYTUNNEL = 0x1212;
const bit<16> TYPE_IPV4 = 0x800;
/*************************************************************************
*********************** H E A D E R S  ***********************************
*************************************************************************/
typedef bit<9>  egressSpec_t;
typedef bit<48> macAddr_t;
typedef bit<32> ip4Addr_t;
header ethernet_t {
    macAddr_t dstAddr;
    macAddr_t srcAddr;
    bit<16>   etherType;
}
header myTunnel_t {
    bit<16> proto_id;
    bit<16> dst_id;
}
header ipv4_t {
    bit<4>    version;
    bit<4>    ihl;
    bit<8>    diffserv;
    bit<16>   totalLen;
    bit<16>   identification;
    bit<3>    flags;
    bit<13>   fragOffset;
    bit<8>    ttl;
    bit<8>    protocol;
    bit<16>   hdrChecksum;
    ip4Addr_t srcAddr;
    ip4Addr_t dstAddr;
}
struct metadata {
    /* empty */
}
struct headers {
    ethernet_t   ethernet;
    myTunnel_t   myTunnel;
    ipv4_t       ipv4;
}
/*************************************************************************
*********************** 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 select(hdr.ethernet.etherType) {
            TYPE_MYTUNNEL: parse_myTunnel;
            TYPE_IPV4: parse_ipv4;
            default: accept;
        }
    } 
    state parse_myTunnel {
        packet.extract(hdr.myTunnel);
        transition select(hdr.myTunnel.proto_id) {
            TYPE_IPV4: parse_ipv4;
            default: accept;
        }
    }
    state parse_ipv4 {
        packet.extract(hdr.ipv4);
        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 ipv4_forward(macAddr_t dstAddr, egressSpec_t port) {
        standard_metadata.egress_spec = port;
        hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;
        hdr.ethernet.dstAddr = dstAddr;
        hdr.ipv4.ttl = hdr.ipv4.ttl - 1;
    }
   
    table ipv4_lpm {
        key = {
            hdr.ipv4.dstAddr: lpm;
        }
        actions = {
            ipv4_forward;
            drop;
            NoAction;
        }
        size = 1024;
        default_action = drop()
    }
    action myTunnel_forward(egressSpec_t port) {
        standard_metadata.egress_spec = port;
    }
    table myTunnel_exact {
        key = {
            hdr.myTunnel.dst_id: exact;
        }
        actions = {
            myTunnel_forward;
            drop;
        }
        size = 1024;
        default_action = drop();
    }
    apply {
        if (hdr.ipv4.isValid() && !hdr.myTunnel.isValid()) {
            // Process only non-tunneled IPv4 packets
            ipv4_lpm.apply();
        }
        if (hdr.myTunnel.isValid()) {
           // process tunneled packets
            myTunnel_exact.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 {
    update_checksum(
        hdr.ipv4.isValid(),
            { hdr.ipv4.version,
          hdr.ipv4.ihl,
              hdr.ipv4.diffserv,
              hdr.ipv4.totalLen,
              hdr.ipv4.identification,
              hdr.ipv4.flags,
              hdr.ipv4.fragOffset,
              hdr.ipv4.ttl,
              hdr.ipv4.protocol,
              hdr.ipv4.srcAddr,
              hdr.ipv4.dstAddr },
            hdr.ipv4.hdrChecksum,
            HashAlgorithm.csum16);
    }
}
 
/*************************************************************************
***********************  D E P A R S E R  *******************************
*************************************************************************/
control MyDeparser(packet_out packet, in headers hdr) {
    apply {
        packet.emit(hdr.ethernet);
        packet.emit(hdr.myTunnel);
        packet.emit(hdr.ipv4);
    }
} 
/*************************************************************************
***********************  S W I T C H  *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;

make run

Compile and run the above program

xterm h1 h2 h3

Open the terminal and run it in h2 and h3

./receive.py

Start listening

Start sending packets to h2 and h3 when running on the h1 command line
1. Tunnel not used:

• Using the command in h1

./send.py 10.0.2.2 "102192121"

• Using the command in h1

./send.py 10.0.3.3 "102192121"

As shown in the figure, without tunnel forwarding, when h1 sends a message to h2, h3 cannot receive it, and when h1 sends a message to h3, h2 cannot receive it.
2. Use tunnel:

• Using the command in h1

./send.py 10.0.2.2 "102192121 tunnel" --dst_id 3

When using tunnel forwarding, packets in h1 ignore the destination ip address of 10.0.2.2, and according to dst_id service h3.

4, Personal summary:

The experimental design is still difficult. There is a problem in installing the software, which is easy to solve. It is difficult to learn P4 later. Finally, I asked the students how to do it. There were errors due to code problems.
，
After modifying the program code, the problem was solved. The later packet transmission is relatively simple, and the main problem is the programming.
In general, this experiment has learned a lot of new knowledge and understood P4 under the V1Model framework_ 16 program structure and basic syntax, as well as being able to use P4 for simple data plane programming, which has benefited me a lot.