// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: CERN-OHL-S-2.0


#include "hls_jfjoch.h"
#include "ip_header_checksum.h"

void ipv4(AXI_STREAM &eth_in,
          AXI_STREAM &udp_out,
          AXI_STREAM &icmp_out,
          ap_uint<32> fpga_ipv4_addr,
          ap_uint<1> direct) {
#pragma HLS INTERFACE ap_ctrl_none port=return
#pragma HLS INTERFACE axis register both port=eth_in
#pragma HLS INTERFACE axis register both port=udp_out
#pragma HLS INTERFACE axis register both port=icmp_out
#pragma HLS INTERFACE ap_none register port=fpga_ipv4_addr
#pragma HLS INTERFACE ap_none register port=direct

#pragma HLS PIPELINE II=1 style=flp
    enum ipv4_dest {DEST_UDP = 0, DEST_ICMP = 1, DEST_IGNORE=2};
    enum ipv4_state {INSPECT_HEADER, FORWARD, DISCARD};
    static ipv4_state state = INSPECT_HEADER;
    static ipv4_dest dest;
    packet_512_t packet_in;
    if (eth_in.read_nb(packet_in)) {
        if (state == INSPECT_HEADER) {
            dest = DEST_IGNORE;
            ap_uint<4> ip_version = packet_in.data(eth_payload_pos + 8 - 1, eth_payload_pos + 4);
            ap_uint<8> ipv4_protocol = packet_in.data(eth_payload_pos + 80 - 1, eth_payload_pos + 72);

            ap_uint<32> ipv4_dest_ip = packet_in.data(eth_payload_pos + 128 + 31, eth_payload_pos + 128);
            ap_uint<16> ipv4_header_checksum_check = computeCheckSum20B(
                    packet_in.data(eth_payload_pos + 159, eth_payload_pos));

            if ((ip_version == 4)
                && (ipv4_header_checksum_check == 0)) {
                // IP is version 4 + IP address is correct + checksum is OK
                // Possibly the conditions can be relaxed for broadcast ICMP
                if ((ipv4_protocol == PROTOCOL_UDP)
                    && ((ipv4_dest_ip == fpga_ipv4_addr)
                        || (ipv4_dest_ip == IPV4_BROADCAST)
                        || direct)) {
                    // For UDP packets the following is OK:
                    //    * correct IP
                    //    * broadcast (e.g. timing)
                    //    * direct settings - no address enforced
                    state = FORWARD;
                    dest = DEST_UDP;
                } else if ((ipv4_protocol == PROTOCOL_ICMP) && (ipv4_dest_ip == fpga_ipv4_addr)) {
                    // IPv4 address is enforced (don't want broadcast pings)
                    // Has to be from 100G network
                    state = FORWARD;
                    dest = DEST_ICMP;
                }
            }
        }

        switch (dest) {
            case DEST_UDP:
                udp_out.write(packet_in);
                break;
            case DEST_ICMP:
                icmp_out.write(packet_in);
                break;
            default:
                break;
        }

        if (packet_in.last)
            state = INSPECT_HEADER;
    }
}