main.p4

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

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

const bit<16> TYPE_IPV4 = 0x0800;
const bit<16> TYPE_IPV6 = 0x86DD;
const bit<16> TYPE_FEED = 0xFEED;

typedef bit<9>  egressSpec_t;

header ethernet_t {
    bit<48>   dstAddr;
    bit<48>   srcAddr;
    bit<16>   etherType;
}
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;
    bit<32> srcAddr;
    bit<32> dstAddr;
}


struct metadata {
    /* empty */
}

struct headers {
    ethernet_t   ethernet;
    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_IPV4: parse_ipv4;
            // TYPE_IPV6: parse_ipv6;
            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 set_output(egressSpec_t p) {
        standard_metadata.egress_spec = p;
    }
    
    table my_ports {
        key = {
            standard_metadata.ingress_port: exact;
        }
        actions = {
            set_output;
            drop;
        }
        size = 64;
        const entries = {
            (9w1) : set_output(9w2);
            (9w2) : set_output(9w1);
        }
    }
    action ipv4_forward(egressSpec_t p, bit<48> dmac) {
        standard_metadata.egress_spec = p;
        hdr.ethernet.dstAddr = dmac;
        hdr.ipv4.ttl = hdr.ipv4.ttl - 1 ;
    }

    table ipv4_routing {
        key = {
            hdr.ipv4.dstAddr: lpm;
        }
        actions = {
            ipv4_forward;
            drop;
        }
        size = 1024;
    }

    table debug {
        key = {
            standard_metadata.ingress_port: exact;
            hdr.ethernet.dstAddr: exact;
            hdr.ethernet.srcAddr: exact;
            hdr.ipv4.ttl : exact;
            hdr.ipv4.version: exact;
            hdr.ipv4.ihl: exact;
            hdr.ipv4.diffserv: exact;
            hdr.ipv4.totalLen: exact;
            hdr.ipv4.identification: exact;
            hdr.ipv4.flags: exact;
            hdr.ipv4.fragOffset: exact;
            hdr.ipv4.ttl: exact;
            hdr.ipv4.protocol: exact;
            hdr.ipv4.hdrChecksum: exact;
            hdr.ipv4.srcAddr: exact;
            hdr.ipv4.dstAddr: exact;
        }
        actions = {
            set_output;
            drop;
        }
        size = 64;
    }
    
    apply {
        my_ports.apply();
        if (hdr.ipv4.isValid()){
            ipv4_routing.apply();
        }
        debug.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) {
    /*
       The egress_port of a packet MUST be selected during INGRESS processing, 
       and egress processing is NOT allowed to change it.
        
        https://p4.org/p4-spec/docs/PSA-v1.1.0.html#appendix-rationale-egress
    */
    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);
        packet.emit(hdr.ipv4);
    }
}

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

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