header_type ethernet_t {
    fields {
        dstAddr : 48;
        srcAddr : 48;
        etherType : 16;
    }
}

header_type ipv4_base_t {
    fields {
        version : 4; 
        ihl : 4;
        diffserv : 8;
        totalLen : 16;
        identification : 16;
        flags : 3;
        fragOffset : 13;
        ttl : 8;
        protocol : 8;
        hdrChecksum : 16;
        srcAddr : 32;
        dstAddr : 32;
    }
}

// End of Option List
#define IPV4_OPTION_EOL_VALUE 0x00
header_type ipv4_option_EOL_t {
    fields {
        value : 8;
    }
}

// No operation
#define IPV4_OPTION_NOP_VALUE 0x01
header_type ipv4_option_NOP_t {
    fields {
        value : 8;
    }
}

#define IPV4_OPTION_SECURITY_VALUE 0x82
header_type ipv4_option_security_t {
    fields {
        value : 8;
        len : 8;
        security : 72;
    }
}

#define IPV4_OPTION_TIMESTAMP_VALUE 0x44
header_type ipv4_option_timestamp_t {
    fields {
        value : 8;
        len : 8;
        data : *;
    }
    length : len;
    max_length : 40;
}

header_type intrinsic_metadata_t {
    fields {
        mcast_grp : 4;
        egress_rid : 4;
        mcast_hash : 16;
        lf_field_list: 32;
    }
}

header_type my_metadata_t {
    fields {
        parse_ipv4_counter : 8;
    }
}

header ethernet_t ethernet;
header ipv4_base_t ipv4_base;
header ipv4_option_EOL_t ipv4_option_EOL[3];
header ipv4_option_NOP_t ipv4_option_NOP[3];
header ipv4_option_security_t ipv4_option_security;
header ipv4_option_timestamp_t ipv4_option_timestamp;
metadata intrinsic_metadata_t intrinsic_metadata;
metadata my_metadata_t my_metadata;

@pragma header_ordering ethernet ipv4_base ipv4_option_security ipv4_option_NOP ipv4_option_timestamp ipv4_option_EOL
parser start {
    return parse_ethernet;
}

#define ETHERTYPE_IPV4 0x0800
parser parse_ethernet {
    extract(ethernet);
    return select(ethernet.etherType) {
        ETHERTYPE_IPV4 : parse_ipv4;
        default: ingress;   
    }
}

parser parse_ipv4 {
    extract(ipv4_base);
    set_metadata(my_metadata.parse_ipv4_counter, ipv4_base.ihl * 4 - 20);
    return select(ipv4_base.ihl) {
        0x05 : ingress;
        default : parse_ipv4_options;
    }
}

parser parse_ipv4_options {
    // match on byte counter and option value
    return select(my_metadata.parse_ipv4_counter, current(0, 8)) {
        0x0000 mask 0xff00 : ingress;
        0x0000 mask 0x00ff : parse_ipv4_option_EOL;
        0x0001 mask 0x00ff : parse_ipv4_option_NOP;
        0x0082 mask 0x00ff : parse_ipv4_option_security;
        0x0044 mask 0x00ff : parse_ipv4_option_timestamp;
    }
}

parser parse_ipv4_option_EOL {
    extract(ipv4_option_EOL[next]);
    set_metadata(my_metadata.parse_ipv4_counter,
                 my_metadata.parse_ipv4_counter - 1);
    return parse_ipv4_options;
}

parser parse_ipv4_option_NOP {
    extract(ipv4_option_NOP[next]);
    set_metadata(my_metadata.parse_ipv4_counter,
                 my_metadata.parse_ipv4_counter - 1);
    return parse_ipv4_options;
}

parser parse_ipv4_option_security {
    extract(ipv4_option_security);
    // security option must have length 11 bytes
    set_metadata(my_metadata.parse_ipv4_counter,
                 my_metadata.parse_ipv4_counter - 11);
    return parse_ipv4_options;
}

parser parse_ipv4_option_timestamp {
    extract(ipv4_option_timestamp);
    set_metadata(my_metadata.parse_ipv4_counter,
                 my_metadata.parse_ipv4_counter - ipv4_option_timestamp.len);
    return parse_ipv4_options;
}

field_list ipv4_checksum_list {
        ipv4_base.version;
        ipv4_base.ihl;
        ipv4_base.diffserv;
        ipv4_base.totalLen;
        ipv4_base.identification;
        ipv4_base.flags;
        ipv4_base.fragOffset;
        ipv4_base.ttl;
        ipv4_base.protocol;
        ipv4_base.srcAddr;
        ipv4_base.dstAddr;
        ipv4_option_security;
        ipv4_option_NOP[0];
        ipv4_option_timestamp;        
}

field_list_calculation ipv4_checksum {
    input {
        ipv4_checksum_list;
    }
    algorithm : csum16;
    output_width : 16;
}

calculated_field ipv4_base.hdrChecksum  {
    update ipv4_checksum;
}

action _drop() {
    drop();
}

action _nop() {
}

control ingress {

}

action format_options_security() {
    pop(ipv4_option_NOP, 3);
    pop(ipv4_option_EOL, 3);
    push(ipv4_option_EOL, 1);
    modify_field(ipv4_base.ihl, 8);
}

action format_options_timestamp() {
    pop(ipv4_option_NOP, 3);
    pop(ipv4_option_EOL, 3);
    // timestamp option is word-aligned so no need for NOP or EOL
    modify_field(ipv4_base.ihl, 5 + (ipv4_option_timestamp.len >> 3));
}

action format_options_both() {
    pop(ipv4_option_NOP, 3);
    pop(ipv4_option_EOL, 3);
    push(ipv4_option_NOP, 1);
    modify_field(ipv4_option_NOP[0].value, IPV4_OPTION_NOP_VALUE);
    modify_field(ipv4_base.ihl, 8 + (ipv4_option_timestamp.len >> 2));
}

table format_options {
    reads {
        ipv4_option_security : valid;
        ipv4_option_timestamp : valid;
    }
    actions {
        format_options_security;
        format_options_timestamp;
        format_options_both;
        _nop;
    }
    size : 4;
}

control egress {
    apply(format_options);
}