Trouble accessing C struct's fields

gistfile1.txt

const c = @cImport ({
  @cInclude("libnetfilter_queue/libnetfilter_queue.h");
});

fn callback(queue: ?*c.nfq_q_handle, msg: ?[*]c.nfgenmsg, data: ?*c.nfq_data, arbitrary: ?*c_void) c_int {
    const packet_header = try c.nfq_get_msg_packet_hdr(data) orelse return 0;
    const packet_id = c.ntohl(packet_header.*.packet_id);

    var payload: [*]u8 = undefined;
    const payload_len = c.nfq_get_payload(data, @ptrCast(?[*]?[*]u8, &payload));
    const payload_slice: []u8 = payload[0..@intCast(usize, payload_len)];

    var test_packet: Packet = undefined;
    _ = packets.parse_ip_packet(&test_packet, payload_slice);

    // Attempting to access `id` field of nfq_q_handle struct here
    if (queue.?.id == OUTPUT_QUEUE_ID) {
        warn("OUT ");
    } else {
        warn("IN  ");
    }
}