lokinet/llarp/nodedb.cpp

#include "nodedb.hpp"

#include "crypto/types.hpp"
#include "dht/kademlia.hpp"
#include "messages/fetch.hpp"
#include "router_contact.hpp"
#include "util/time.hpp"

#include <algorithm>
#include <unordered_map>
#include <utility>

static const std::string RC_FILE_EXT = ".signed";

namespace llarp
{
  static void
  EnsureSkiplist(fs::path nodedbDir)
  {
    if (not fs::exists(nodedbDir))
    {
      // if the old 'netdb' directory exists, move it to this one
      fs::path parent = nodedbDir.parent_path();
      fs::path old = parent / "netdb";
      if (fs::exists(old))
        fs::rename(old, nodedbDir);
      else
        fs::create_directory(nodedbDir);
    }

    if (not fs::is_directory(nodedbDir))
      throw std::runtime_error{fmt::format("nodedb {} is not a directory", nodedbDir)};
  }

  NodeDB::NodeDB(fs::path root, std::function<void(std::function<void()>)> diskCaller, Router* r)
      : _router{*r}
      , _root{std::move(root)}
      , _disk(std::move(diskCaller))
      , _next_flush_time{time_now_ms() + FLUSH_INTERVAL}
  {
    EnsureSkiplist(_root);
    fetch_counters.clear();
  }

  std::optional<RemoteRC>
  NodeDB::get_rc_by_rid(const RouterID& rid)
  {
    if (auto itr = rc_lookup.find(rid); itr != rc_lookup.end())
      return itr->second;

    return std::nullopt;
  }

  std::optional<RemoteRC>
  NodeDB::get_random_rc() const
  {
    std::optional<RemoteRC> rand = std::nullopt;

    std::sample(known_rcs.begin(), known_rcs.end(), &*rand, 1, csrng);
    return rand;
  }

  std::optional<std::vector<RemoteRC>>
  NodeDB::get_n_random_rcs(size_t n, bool exact) const
  {
    auto rand = std::make_optional<std::vector<RemoteRC>>();
    rand->reserve(n);

    std::sample(known_rcs.begin(), known_rcs.end(), std::back_inserter(*rand), n, csrng);
    if (rand->size() < (exact ? n : 1))
      rand.reset();
    return rand;
  }
  std::optional<RemoteRC>
  NodeDB::get_random_rc_conditional(std::function<bool(RemoteRC)> hook) const
  {
    std::optional<RemoteRC> rand = get_random_rc();

    if (rand and hook(*rand))
      return rand;

    size_t i = 0;

    for (const auto& rc : known_rcs)
    {
      if (not hook(rc))
        continue;

      if (++i <= 1)
      {
        rand = rc;
        continue;
      }

      size_t x = csrng() % (i + 1);
      if (x <= 1)
        rand = rc;
    }

    return rand;
  }

  std::optional<std::vector<RemoteRC>>
  NodeDB::get_n_random_rcs_conditional(
      size_t n, std::function<bool(RemoteRC)> hook, bool exact) const
  {
    auto selected = std::make_optional<std::vector<RemoteRC>>();
    selected->reserve(n);

    size_t i = 0;

    for (const auto& rc : known_rcs)
    {
      // ignore any RC's that do not pass the condition
      if (not hook(rc))
        continue;

      // load the first n RC's that pass the condition into selected
      if (++i <= n)
      {
        selected->push_back(rc);
        continue;
      }

      // replace selections with decreasing probability per iteration
      size_t x = csrng() % (i + 1);
      if (x < n)
        (*selected)[x] = rc;
    }

    if (selected->size() < (exact ? n : 1))
      selected.reset();
    return selected;
  }

  void
  NodeDB::Tick(llarp_time_t now)
  {
    if (_next_flush_time == 0s)
      return;

    if (now > _next_flush_time)
    {
      _router.loop()->call([this]() {
        _next_flush_time += FLUSH_INTERVAL;
        // make copy of all rcs
        std::vector<RemoteRC> copy;

        for (const auto& item : rc_lookup)
          copy.push_back(item.second);

        // flush them to disk in one big job
        // TODO: split this up? idk maybe some day...
        _disk([this, data = std::move(copy)]() {
          for (const auto& rc : data)
            rc.write(get_path_by_pubkey(rc.router_id()));
        });
      });
    }
  }

  fs::path
  NodeDB::get_path_by_pubkey(const RouterID& pubkey) const
  {
    return _root / (pubkey.ToString() + RC_FILE_EXT);
  }

  bool
  NodeDB::want_rc(const RouterID& rid) const
  {
    if (not _router.is_service_node())
      return true;

    return known_rids.count(rid);
  }

  void
  NodeDB::set_bootstrap_routers(BootstrapList& from_router)
  {
    _bootstraps.merge(from_router);
    _bootstraps.randomize();
  }

  bool
  NodeDB::process_fetched_rcs(std::set<RemoteRC>& rcs)
  {
    std::set<RemoteRC> confirmed_set, unconfirmed_set;

    // the intersection of local RC's and received RC's is our confirmed set
    std::set_intersection(
        known_rcs.begin(),
        known_rcs.end(),
        rcs.begin(),
        rcs.end(),
        std::inserter(confirmed_set, confirmed_set.begin()));

    // the intersection of the confirmed set and received RC's is our unconfirmed set
    std::set_intersection(
        rcs.begin(),
        rcs.end(),
        confirmed_set.begin(),
        confirmed_set.end(),
        std::inserter(unconfirmed_set, unconfirmed_set.begin()));

    // the total number of rcs received
    const auto num_received = static_cast<double>(rcs.size());
    // the number of returned "good" rcs (that are also found locally)
    const auto inter_size = confirmed_set.size();

    const auto fetch_threshold = (double)inter_size / num_received;

    /** We are checking 2 things here:
        1) The number of "good" rcs is above MIN_GOOD_RC_FETCH_TOTAL
        2) The ratio of "good" rcs to total received is above MIN_GOOD_RC_FETCH_THRESHOLD
    */
    bool success = false;
    if (success =
            inter_size > MIN_GOOD_RC_FETCH_TOTAL and fetch_threshold > MIN_GOOD_RC_FETCH_THRESHOLD;
        success)
    {
      // set rcs to be intersection set
      rcs = std::move(confirmed_set);

      process_results(std::move(unconfirmed_set), unconfirmed_rcs, known_rcs);
    }

    return success;
  }

  bool
  NodeDB::ingest_fetched_rcs(std::set<RemoteRC> rcs)
  {
    // if we are not bootstrapping, we should check the rc's against the ones we currently hold
    if (not _using_bootstrap_fallback)
    {
      log::critical(logcat, "Checking returned RCs against locally held...");

      auto success = process_fetched_rcs(rcs);

      log::critical(
          logcat, "RCs returned by FetchRC {} by trust model", success ? "approved" : "rejected");
      return success;
    }

    while (!rcs.empty())
      put_rc_if_newer(std::move(rcs.extract(rcs.begin()).value()));

    return true;
  }

  /** We only call into this function after ensuring two conditions:
        1) We have received all 12 responses from the queried RouterID sources, whether that
          response was a timeout or not
        2) Of those responses, less than 4 were errors of any sorts

      Upon receiving each response from the rid fetch sources, the returned rid's are incremented
      in fetch_counters. This greatly simplifies the analysis required by this function to the
      determine success or failure:
        - If the frequency of each rid is above a threshold, it is accepted
        - If the number of accepted rids is below a certain amount, the set is rejected

      Logically, this function performs the following basic analysis of the returned RIDs:
        1) All responses are coalesced into a union set with no repetitions
        2) If we are bootstrapping:
            - The routerID's returned
  */
  bool
  NodeDB::process_fetched_rids()
  {
    std::set<RouterID> union_set, confirmed_set, unconfirmed_set;

    for (const auto& [rid, count] : fetch_counters)
    {
      if (count > MIN_RID_FETCH_FREQ)
        union_set.insert(rid);
      else
        unconfirmed_set.insert(rid);
    }

    // get the intersection of accepted rids and local rids
    std::set_intersection(
        known_rids.begin(),
        known_rids.end(),
        union_set.begin(),
        union_set.end(),
        std::inserter(confirmed_set, confirmed_set.begin()));

    // the total number of rids received
    const auto num_received = (double)fetch_counters.size();
    // the total number of received AND accepted rids
    const auto union_size = union_set.size();

    const auto fetch_threshold = (double)union_size / num_received;

    /** We are checking 2 things here:
        1) The ratio of received/accepted to total received is above GOOD_RID_FETCH_THRESHOLD.
           This tells us how well the rid source's sets of rids "agree" with one another
        2) The total number received is above MIN_RID_FETCH_TOTAL. This ensures that we are
           receiving a sufficient amount to make a comparison of any sorts
    */
    bool success = false;
    if (success = (fetch_threshold > GOOD_RID_FETCH_THRESHOLD)
            and (union_size > MIN_GOOD_RID_FETCH_TOTAL);
        success)
    {
      process_results(std::move(unconfirmed_set), unconfirmed_rids, known_rids);

      known_rids.merge(confirmed_set);
    }

    return success;
  }

  void
  NodeDB::ingest_rid_fetch_responses(const RouterID& source, std::set<RouterID> rids)
  {
    if (rids.empty())
    {
      fail_sources.insert(source);
      return;
    }

    for (const auto& rid : rids)
      fetch_counters[rid] += 1;
  }

  void
  NodeDB::fetch_initial(bool is_snode)
  {
    auto sz = num_rcs();

    if (sz < MIN_ACTIVE_RCS)
    {
      log::critical(logcat, "{}/{} RCs held locally... BOOTSTRAP TIME", sz, MIN_ACTIVE_RCS);
      fallback_to_bootstrap();
    }
    else if (is_snode)
    {
      // service nodes who have sufficient local RC's can bypass initial fetching
      _needs_initial_fetch = false;
    }
    else
    {
      _fetching_initial = true;
      // Set fetch source as random selection of known active client routers
      fetch_source = *std::next(known_rids.begin(), csrng() % known_rids.size());
      fetch_rcs(true);
    }
  }

  void
  NodeDB::fetch_rcs(bool initial)
  {
    auto& num_failures = fetch_failures;

    // base case; this function is called recursively
    if (num_failures > MAX_FETCH_ATTEMPTS)
    {
      fetch_rcs_result(initial, true);
      return;
    }

    std::vector<RouterID> needed;
    const auto now = time_point_now();

    if (not initial)
    {
      for (const auto& [rid, rc] : rc_lookup)
      {
        if (now - rc.timestamp() > RouterContact::OUTDATED_AGE)
          needed.push_back(rid);
      }
    }

    RouterID& src = fetch_source;
    log::critical(
        logcat,
        "Sending{} FetchRCs request to {} for {} RCs",
        initial ? " initial" : "",
        src,
        initial ? "all of the" : std::to_string(needed.size()));

    if (initial)
      _router.next_initial_fetch_attempt = now + INITIAL_ATTEMPT_INTERVAL;

    _router.last_rc_fetch = now;

    _router.link_manager().fetch_rcs(
        src,
        FetchRCMessage::serialize(_router.last_rc_fetch, needed),
        [this, source = src, initial](oxen::quic::message m) mutable {
          if (m.timed_out)
          {
            log::critical(logcat, "RC fetch to {} timed out!", source);
            fetch_rcs_result(initial, m.timed_out);
            return;
          }
          try
          {
            oxenc::bt_dict_consumer btdc{m.body()};
            // TODO: can this just combine with the above failure case...?
            if (m.is_error())
            {
              auto reason = btdc.require<std::string_view>(messages::STATUS_KEY);
              log::critical(logcat, "RC fetch to {} returned error: {}", source, reason);
              fetch_rcs_result(initial, m.is_error());
              return;
            }

            auto btlc = btdc.require<oxenc::bt_list_consumer>("rcs"sv);

            std::set<RemoteRC> rcs;

            while (not btlc.is_finished())
              rcs.emplace(btlc.consume_dict_data());

            // if process_fetched_rcs returns false, then the trust model rejected the fetched RC's
            fetch_rcs_result(initial, not ingest_fetched_rcs(std::move(rcs)));
          }
          catch (const std::exception& e)
          {
            log::critical(
                logcat, "Failed to parse RC fetch response from {}: {}", source, e.what());
            fetch_rcs_result(initial, true);
            return;
          }
        });
  }

  void
  NodeDB::fetch_rids(bool initial)
  {
    // base case; this function is called recursively
    if (fetch_failures > MAX_FETCH_ATTEMPTS)
    {
      fetch_rids_result(initial);
      return;
    }

    if (rid_sources.empty())
    {
      reselect_router_id_sources(rid_sources);
    }

    if (not initial and rid_sources.empty())
    {
      log::error(logcat, "Attempting to fetch RouterIDs, but have no source from which to do so.");
      fallback_to_bootstrap();
      return;
    }

    fetch_counters.clear();

    RouterID& src = fetch_source;
    _router.last_rid_fetch = llarp::time_point_now();

    for (const auto& target : rid_sources)
    {
      log::critical(logcat, "Sending FetchRIDs request to {} via {}", target, src);
      _router.link_manager().fetch_router_ids(
          src,
          FetchRIDMessage::serialize(target),
          [this, source = src, target, initial](oxen::quic::message m) mutable {
            if (m.is_error())
            {
              auto err = "RID fetch from {} via {} {}"_format(
                  target, source, m.timed_out ? "timed out" : "failed");
              log::critical(link_cat, err);
              ingest_rid_fetch_responses(target);
              fetch_rids_result(initial);
              return;
            }

            try
            {
              oxenc::bt_dict_consumer btdc{m.body()};

              btdc.required("routers");
              auto router_id_strings = btdc.consume_list<std::vector<ustring>>();

              btdc.require_signature("signature", [&source](ustring_view msg, ustring_view sig) {
                if (sig.size() != 64)
                  throw std::runtime_error{"Invalid signature: not 64 bytes"};
                if (not crypto::verify(source, msg, sig))
                  throw std::runtime_error{
                      "Failed to verify signature for fetch RouterIDs response."};
              });

              std::set<RouterID> router_ids;

              for (const auto& s : router_id_strings)
              {
                if (s.size() != RouterID::SIZE)
                {
                  log::critical(
                      link_cat, "RID fetch from {} via {} returned bad RouterID", target, source);
                  ingest_rid_fetch_responses(target);
                  fetch_rids_result(initial);
                  return;
                }

                router_ids.emplace(s.data());
              }

              ingest_rid_fetch_responses(target, std::move(router_ids));
              fetch_rids_result(initial);  // success
              return;
            }
            catch (const std::exception& e)
            {
              log::critical(link_cat, "Error handling fetch RouterIDs response: {}", e.what());
              ingest_rid_fetch_responses(target);
              fetch_rids_result(initial);
            }
          });
    }
  }

  void
  NodeDB::fetch_rcs_result(bool initial, bool error)
  {
    if (error)
    {
      if (++fetch_failures >= MAX_FETCH_ATTEMPTS)
      {
        log::critical(
            logcat,
            "RC fetching from {} reached failure threshold ({}); falling back to bootstrap...",
            fetch_source,
            MAX_FETCH_ATTEMPTS);

        fallback_to_bootstrap();
        return;
      }

      if (initial)
        _needs_initial_fetch = true;

      // If we have passed the last last conditional, then it means we are not bootstrapping
      // and the current fetch_source has more attempts before being rotated. As a result, we
      // find new non-bootstrap RC fetch source and try again buddy
      fetch_source = (initial) ? *std::next(known_rids.begin(), csrng() % known_rids.size())
                               : std::next(rc_lookup.begin(), csrng() % rc_lookup.size())->first;

      fetch_rcs(initial);
    }
    else
    {
      log::critical(logcat, "Successfully fetched RC's from {}", fetch_source);
      post_fetch_rcs(initial);
    }
  }

  void
  NodeDB::fetch_rids_result(bool initial)
  {
    if (fetch_failures >= MAX_FETCH_ATTEMPTS)
    {
      log::critical(
          logcat,
          "Failed {} attempts to fetch RID's from {}; reverting to bootstrap...",
          MAX_FETCH_ATTEMPTS,
          fetch_source);

      fallback_to_bootstrap();
      return;
    }

    auto n_responses = RID_SOURCE_COUNT - fail_sources.size();

    if (n_responses < RID_SOURCE_COUNT)
    {
      log::critical(logcat, "Received {}/{} fetch RID requests", n_responses, RID_SOURCE_COUNT);
      return;
    }

    auto n_fails = fail_sources.size();

    if (n_fails <= MAX_RID_ERRORS)
    {
      log::critical(
          logcat, "RID fetching was successful ({}/{} acceptable errors)", n_fails, MAX_RID_ERRORS);

      // this is where the trust model will do verification based on the similarity of the sets
      if (process_fetched_rids())
      {
        log::critical(logcat, "Accumulated RID's accepted by trust model");
        post_fetch_rids(initial);
        return;
      }

      log::critical(
          logcat, "Accumulated RID's rejected by trust model, reselecting all RID sources...");
      reselect_router_id_sources(rid_sources);
      ++fetch_failures;
    }
    else
    {
      // we had 4 or more failed requests, so we will need to rotate our rid sources
      log::critical(
          logcat, "RID fetching found {} failures; reselecting failed RID sources...", n_fails);
      ++fetch_failures;
      reselect_router_id_sources(fail_sources);
    }

    fetch_rids(initial);
  }

  // This function is only called after a successful FetchRC request
  void
  NodeDB::post_fetch_rcs(bool initial)
  {
    _needs_rebootstrap = false;
    _needs_initial_fetch = false;
    _using_bootstrap_fallback = false;
    fail_sources.clear();
    fetch_failures = 0;

    if (initial)
      fetch_rids(initial);
  }

  void
  NodeDB::post_fetch_rids(bool initial)
  {
    fail_sources.clear();
    fetch_failures = 0;
    fetch_counters.clear();
    _needs_rebootstrap = false;
    _using_bootstrap_fallback = false;

    if (initial)
    {
      _needs_initial_fetch = false;
      _fetching_initial = false;
      _initial_completed = true;
    }
  }

  void
  NodeDB::fallback_to_bootstrap()
  {
    log::critical(logcat, "{} called", __PRETTY_FUNCTION__);
    auto at_max_failures = bootstrap_attempts >= MAX_BOOTSTRAP_FETCH_ATTEMPTS;

    // base case: we have failed to query all bootstraps, or we received a sample of
    // the network, but the sample was unusable or unreachable. We will also enter this
    // if we are on our first fallback to bootstrap so we can set the fetch_source (by
    // checking not using_bootstrap_fallback)
    if (at_max_failures || not _using_bootstrap_fallback)
    {
      bootstrap_attempts = 0;

      // Fail case: if we have returned to the front of the bootstrap list, we're in a
      // bad spot; we are unable to do anything
      if (_using_bootstrap_fallback)
      {
        auto err = fmt::format(
            "ERROR: ALL BOOTSTRAPS ARE BAD... REATTEMPTING IN {}...", BOOTSTRAP_COOLDOWN);
        log::error(logcat, err);

        bootstrap_cooldown();
        return;
      }
    }

    auto& rc = (_using_bootstrap_fallback) ? _bootstraps.next() : _bootstraps.current();
    fetch_source = rc.router_id();

    // By passing the last conditional, we ensure this is set to true
    _using_bootstrap_fallback = true;
    _needs_rebootstrap = false;
    ++bootstrap_attempts;

    log::critical(logcat, "Dispatching BootstrapRC fetch request to {}", fetch_source);

    auto is_snode = _router.is_service_node();

    auto num_needed =
        is_snode ? SERVICE_NODE_BOOTSTRAP_SOURCE_COUNT : CLIENT_BOOTSTRAP_SOURCE_COUNT;

    _router.link_manager().fetch_bootstrap_rcs(
        rc,
        BootstrapFetchMessage::serialize(
            is_snode ? std::make_optional(_router.router_contact) : std::nullopt, num_needed),
        [this, is_snode = _router.is_service_node(), src = rc.router_id()](
            oxen::quic::message m) mutable {
          log::critical(logcat, "Received response to BootstrapRC fetch request...");

          if (not m)
          {
            log::warning(
                logcat,
                "BootstrapRC fetch request to {} failed (error {}/{})",
                src,
                bootstrap_attempts,
                MAX_BOOTSTRAP_FETCH_ATTEMPTS);
            fallback_to_bootstrap();
            return;
          }

          size_t num = 0;

          try
          {
            oxenc::bt_dict_consumer btdc{m.body()};

            {
              auto btlc = btdc.require<oxenc::bt_list_consumer>("rcs"sv);

              while (not btlc.is_finished())
              {
                auto rc = RemoteRC{btlc.consume_dict_data()};
                put_rc(rc);
                ++num;
              }
            }
          }
          catch (const std::exception& e)
          {
            log::warning(
                logcat,
                "Failed to parse BootstrapRC fetch response from {} (error {}/{}): {}",
                src,
                bootstrap_attempts,
                MAX_BOOTSTRAP_FETCH_ATTEMPTS,
                e.what());
            fallback_to_bootstrap();
            return;
          }

          log::critical(
              logcat,
              "BootstrapRC fetch response from {} returned {}/{} needed RCs",
              src,
              num,
              MIN_ACTIVE_RCS);

          if (not is_snode)
          {
            log::critical(
                logcat,
                "Client completed processing BootstrapRC fetch; proceeding to initial fetch");
            fetch_initial();
          }
          else
          {
            log::critical(logcat, "Service node completed processing BootstrapRC fetch!");
            post_snode_bootstrap();
          }
        });
  }

  void
  NodeDB::post_snode_bootstrap()
  {
    _needs_rebootstrap = false;
    _using_bootstrap_fallback = false;
    _needs_initial_fetch = false;
  }

  void
  NodeDB::bootstrap_cooldown()
  {
    _needs_rebootstrap = true;
    _using_bootstrap_fallback = false;
    _router.next_bootstrap_attempt = llarp::time_point_now() + BOOTSTRAP_COOLDOWN;
  }

  void
  NodeDB::reselect_router_id_sources(std::set<RouterID> specific)
  {
    replace_subset(rid_sources, specific, known_rids, RID_SOURCE_COUNT, csrng);
  }

  void
  NodeDB::set_router_whitelist(
      const std::vector<RouterID>& whitelist,
      const std::vector<RouterID>& greylist,
      const std::vector<RouterID>& greenlist)
  {
    log::critical(
        logcat,
        "Oxend provided {}/{}/{} (white/gray/green) routers",
        whitelist.size(),
        greylist.size(),
        greenlist.size());

    if (whitelist.empty())
      return;

    _registered_routers.clear();
    _registered_routers.insert(whitelist.begin(), whitelist.end());
    _registered_routers.insert(greylist.begin(), greylist.end());
    _registered_routers.insert(greenlist.begin(), greenlist.end());

    _router_whitelist.clear();
    _router_whitelist.insert(whitelist.begin(), whitelist.end());
    _router_greylist.clear();
    _router_greylist.insert(greylist.begin(), greylist.end());
    _router_greenlist.clear();
    _router_greenlist.insert(greenlist.begin(), greenlist.end());

    log::critical(
        logcat,
        "Service node holding {}:{} (whitelist:registered) after oxend integration",
        _router_whitelist.size(),
        _registered_routers.size());
  }

  std::optional<RouterID>
  NodeDB::get_random_whitelist_router() const
  {
    std::optional<RouterID> rand = std::nullopt;

    std::sample(_router_whitelist.begin(), _router_whitelist.end(), &*rand, 1, csrng);
    return rand;
  }

  bool
  NodeDB::is_connection_allowed(const RouterID& remote) const
  {
    if (not _router.is_service_node())
    {
      if (_pinned_edges.size() && _pinned_edges.count(remote) == 0
          && not _bootstraps.contains(remote))
        return false;
    }

    return known_rids.count(remote) or _router_greylist.count(remote);
  }

  bool
  NodeDB::is_first_hop_allowed(const RouterID& remote) const
  {
    if (_pinned_edges.size() && _pinned_edges.count(remote) == 0)
      return false;

    return true;
  }

  void
  NodeDB::store_bootstraps()
  {
    if (_bootstraps.empty())
      return;

    for (const auto& rc : _bootstraps)
    {
      put_rc(rc);
    }

    log::critical(logcat, "NodeDB stored {} bootstrap routers", _bootstraps.size());
  }

  void
  NodeDB::load_from_disk()
  {
    if (_root.empty())
      return;

    std::vector<fs::path> purge;

    const auto now = time_now_ms();

    for (const auto& f : fs::directory_iterator{_root})
    {
      if (not f.is_regular_file() or f.path().extension() != RC_FILE_EXT)
        continue;

      RemoteRC rc{};

      if (not rc.read(f) or rc.is_expired(now))
      {
        // try loading it, purge it if it is junk or expired
        purge.push_back(f);
        continue;
      }

      const auto& rid = rc.router_id();

      auto [itr, b] = known_rcs.insert(std::move(rc));
      rc_lookup.emplace(rid, *itr);
      known_rids.insert(rid);
    }

    if (not purge.empty())
    {
      log::warning(logcat, "removing {} invalid RCs from disk", purge.size());

      for (const auto& fpath : purge)
        fs::remove(fpath);
    }
  }

  void
  NodeDB::save_to_disk() const
  {
    if (_root.empty())
      return;

    _router.loop()->call([this]() {
      for (const auto& rc : rc_lookup)
      {
        rc.second.write(get_path_by_pubkey(rc.first));
      }
    });
  }

  bool
  NodeDB::has_rc(const RemoteRC& rc) const
  {
    return known_rcs.count(rc);
  }

  bool
  NodeDB::has_rc(const RouterID& pk) const
  {
    return rc_lookup.count(pk);
  }

  std::optional<RemoteRC>
  NodeDB::get_rc(const RouterID& pk) const
  {
    if (auto itr = rc_lookup.find(pk); itr != rc_lookup.end())
      return itr->second;

    return std::nullopt;
  }

  void
  NodeDB::remove_router(RouterID pk)
  {
    _router.loop()->call([this, pk]() {
      rc_lookup.erase(pk);
      remove_many_from_disk_async({pk});
    });
  }

  void
  NodeDB::remove_stale_rcs()
  {
    auto cutoff_time = time_point_now();

    cutoff_time -=
        _router.is_service_node() ? RouterContact::OUTDATED_AGE : RouterContact::LIFETIME;

    for (auto itr = rc_lookup.begin(); itr != rc_lookup.end();)
    {
      if (cutoff_time > itr->second.timestamp())
      {
        log::info(logcat, "Pruning RC for {}, as it is too old to keep.", itr->first);
        known_rcs.erase(itr->second);
        rc_lookup.erase(itr);
        continue;
      }
      itr++;
    }
  }

  bool
  NodeDB::put_rc(RemoteRC rc, rc_time now)
  {
    const auto& rid = rc.router_id();

    if (rid == _router.local_rid())
      return false;

    known_rcs.erase(rc);
    rc_lookup.erase(rid);

    auto [itr, b] = known_rcs.insert(std::move(rc));
    rc_lookup.emplace(rid, *itr);
    known_rids.insert(rid);

    last_rc_update_times[rid] = now;
    return true;
  }

  size_t
  NodeDB::num_rcs() const
  {
    return known_rcs.size();
  }

  size_t
  NodeDB::num_rids() const
  {
    return known_rids.size();
  }

  bool
  NodeDB::verify_store_gossip_rc(const RemoteRC& rc)
  {
    if (registered_routers().count(rc.router_id()))
      return put_rc_if_newer(rc);

    return false;
  }

  void
  NodeDB::verify_gossip_bfetch_rc(const RemoteRC& rc)
  {
    if (auto maybe = get_rc(rc.router_id()))
    {
      if (maybe->other_is_newer(rc))
        put_rc(rc);
    }
    else
    {
      if (put_rc(rc))
        _router.link_manager().gossip_rc(_router.local_rid(), rc);
    }
  }

  bool
  NodeDB::put_rc_if_newer(RemoteRC rc)
  {
    if (auto maybe = get_rc(rc.router_id()))
    {
      if (maybe->other_is_newer(rc))
        return put_rc(rc);

      return false;
    }

    return put_rc(rc);
  }

  void
  NodeDB::remove_many_from_disk_async(std::unordered_set<RouterID> remove) const
  {
    if (_root.empty())
      return;

    // build file list
    std::set<fs::path> files;

    for (auto id : remove)
      files.emplace(get_path_by_pubkey(std::move(id)));

    // remove them from the disk via the diskio thread
    _disk([files]() {
      for (auto fpath : files)
        fs::remove(fpath);
    });
  }

  RemoteRC
  NodeDB::find_closest_to(llarp::dht::Key_t location) const
  {
    return _router.loop()->call_get([this, location]() -> RemoteRC {
      RemoteRC rc{};
      const llarp::dht::XorMetric compare(location);

      visit_all([&rc, compare](const auto& otherRC) {
        const auto& rid = rc.router_id();

        if (rid.IsZero() || compare(dht::Key_t{otherRC.router_id()}, dht::Key_t{rid}))
        {
          rc = otherRC;
          return;
        }
      });
      return rc;
    });
  }

  std::vector<RemoteRC>
  NodeDB::find_many_closest_to(llarp::dht::Key_t location, uint32_t numRouters) const
  {
    return _router.loop()->call_get([this, location, numRouters]() -> std::vector<RemoteRC> {
      std::vector<const RemoteRC*> all;

      all.reserve(known_rcs.size());

      for (auto& entry : rc_lookup)
      {
        all.push_back(&entry.second);
      }

      auto it_mid = numRouters < all.size() ? all.begin() + numRouters : all.end();

      std::partial_sort(
          all.begin(), it_mid, all.end(), [compare = dht::XorMetric{location}](auto* a, auto* b) {
            return compare(*a, *b);
          });

      std::vector<RemoteRC> closest;
      closest.reserve(numRouters);
      for (auto it = all.begin(); it != it_mid; ++it)
        closest.push_back(**it);

      return closest;
    });
  }
}  // namespace llarp