lokinet/llarp/path/path.cpp

#include "path.hpp"

#include <llarp/exit/exit_messages.hpp>
#include <llarp/link/i_link_manager.hpp>
#include <llarp/messages/discard.hpp>
#include <llarp/messages/relay_commit.hpp>
#include <llarp/messages/relay_status.hpp>
#include "pathbuilder.hpp"
#include "transit_hop.hpp"
#include <llarp/profiling.hpp>
#include <llarp/router/abstractrouter.hpp>
#include <llarp/routing/dht_message.hpp>
#include <llarp/routing/path_latency_message.hpp>
#include <llarp/routing/transfer_traffic_message.hpp>
#include <llarp/util/buffer.hpp>
#include <llarp/util/endian.hpp>
#include <llarp/tooling/path_event.hpp>

#include <deque>
#include <queue>

namespace llarp
{
  namespace path
  {
    Path::Path(
        const std::vector<RouterContact>& h,
        PathSet* parent,
        PathRole startingRoles,
        std::string shortName)
        : m_PathSet(parent), _role(startingRoles), m_shortName(std::move(shortName))

    {
      hops.resize(h.size());
      size_t hsz = h.size();
      for (size_t idx = 0; idx < hsz; ++idx)
      {
        hops[idx].rc = h[idx];
        do
        {
          hops[idx].txID.Randomize();
        } while (hops[idx].txID.IsZero());

        do
        {
          hops[idx].rxID.Randomize();
        } while (hops[idx].rxID.IsZero());
      }

      for (size_t idx = 0; idx < hsz - 1; ++idx)
      {
        hops[idx].txID = hops[idx + 1].rxID;
      }
      // initialize parts of the introduction
      intro.router = hops[hsz - 1].rc.pubkey;
      intro.pathID = hops[hsz - 1].txID;
      if (parent)
        EnterState(ePathBuilding, parent->Now());
    }

    void
    Path::SetBuildResultHook(BuildResultHookFunc func)
    {
      m_BuiltHook = func;
    }

    bool
    Path::HandleUpstream(const llarp_buffer_t& X, const TunnelNonce& Y, AbstractRouter* r)
    {
      if (not m_UpstreamReplayFilter.Insert(Y))
        return false;
      return IHopHandler::HandleUpstream(X, Y, r);
    }

    bool
    Path::HandleDownstream(const llarp_buffer_t& X, const TunnelNonce& Y, AbstractRouter* r)
    {
      if (not m_DownstreamReplayFilter.Insert(Y))
        return false;
      return IHopHandler::HandleDownstream(X, Y, r);
    }

    RouterID
    Path::Endpoint() const
    {
      return hops[hops.size() - 1].rc.pubkey;
    }

    PubKey
    Path::EndpointPubKey() const
    {
      return hops[hops.size() - 1].rc.pubkey;
    }

    PathID_t
    Path::TXID() const
    {
      return hops[0].txID;
    }

    PathID_t
    Path::RXID() const
    {
      return hops[0].rxID;
    }

    bool
    Path::IsReady() const
    {
      if (Expired(llarp::time_now_ms()))
        return false;
      return intro.latency > 0s && _status == ePathEstablished;
    }

    bool
    Path::IsEndpoint(const RouterID& r, const PathID_t& id) const
    {
      return hops[hops.size() - 1].rc.pubkey == r && hops[hops.size() - 1].txID == id;
    }

    RouterID
    Path::Upstream() const
    {
      return hops[0].rc.pubkey;
    }

    const std::string&
    Path::ShortName() const
    {
      return m_shortName;
    }

    std::string
    Path::HopsString() const
    {
      std::stringstream ss;
      for (const auto& hop : hops)
        ss << RouterID(hop.rc.pubkey) << " -> ";
      return ss.str();
    }

    bool
    Path::HandleLRSM(uint64_t status, std::array<EncryptedFrame, 8>& frames, AbstractRouter* r)
    {
      uint64_t currentStatus = status;

      size_t index = 0;
      std::optional<RouterID> failedAt;
      while (index < hops.size())
      {
        if (!frames[index].DoDecrypt(hops[index].shared))
        {
          currentStatus = LR_StatusRecord::FAIL_DECRYPT_ERROR;
          failedAt = hops[index].rc.pubkey;
          break;
        }
        llarp::LogDebug("decrypted LRSM frame from ", hops[index].rc.pubkey);

        llarp_buffer_t* buf = frames[index].Buffer();
        buf->cur = buf->base + EncryptedFrameOverheadSize;

        LR_StatusRecord record;
        // successful decrypt
        if (!record.BDecode(buf))
        {
          llarp::LogWarn("malformed frame inside LRCM from ", hops[index].rc.pubkey);
          currentStatus = LR_StatusRecord::FAIL_MALFORMED_RECORD;
          failedAt = hops[index].rc.pubkey;
          break;
        }
        llarp::LogDebug("Decoded LR Status Record from ", hops[index].rc.pubkey);

        currentStatus = record.status;
        if ((record.status & LR_StatusRecord::SUCCESS) != LR_StatusRecord::SUCCESS)
        {
          if (record.status & LR_StatusRecord::FAIL_CONGESTION and index == 0)
          {
            // first hop building too fast
            failedAt = hops[index].rc.pubkey;
            break;
          }
          // failed at next hop
          if (index + 1 < hops.size())
          {
            failedAt = hops[index + 1].rc.pubkey;
          }
          else
          {
            failedAt = hops[index].rc.pubkey;
          }
          break;
        }
        ++index;
      }

      if ((currentStatus & LR_StatusRecord::SUCCESS) == LR_StatusRecord::SUCCESS)
      {
        llarp::LogDebug("LR_Status message processed, path build successful");
        r->loop()->call([r, self = shared_from_this()] { self->HandlePathConfirmMessage(r); });
      }
      else
      {
        if (failedAt)
        {
          r->NotifyRouterEvent<tooling::PathBuildRejectedEvent>(Endpoint(), RXID(), *failedAt);
          LogWarn(Name(), " build failed at ", *failedAt);
          r->routerProfiling().MarkHopFail(*failedAt);
        }
        else
          r->routerProfiling().MarkPathFail(this);
        llarp::LogDebug("LR_Status message processed, path build failed");

        if (currentStatus & LR_StatusRecord::FAIL_TIMEOUT)
        {
          llarp::LogDebug("Path build failed due to timeout");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_CONGESTION)
        {
          llarp::LogDebug("Path build failed due to congestion");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_DEST_UNKNOWN)
        {
          llarp::LogDebug(
              "Path build failed due to one or more nodes giving destination "
              "unknown");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_DEST_INVALID)
        {
          llarp::LogDebug(
              "Path build failed due to one or more nodes considered an "
              "invalid destination");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_CANNOT_CONNECT)
        {
          llarp::LogDebug(
              "Path build failed due to a node being unable to connect to the "
              "next hop");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_MALFORMED_RECORD)
        {
          llarp::LogDebug(
              "Path build failed due to a malformed record in the build status "
              "message");
        }
        else if (currentStatus & LR_StatusRecord::FAIL_DECRYPT_ERROR)
        {
          llarp::LogDebug(
              "Path build failed due to a decrypt error in the build status "
              "message");
        }
        else
        {
          llarp::LogDebug("Path build failed for an unspecified reason");
        }
        RouterID edge{};
        if (failedAt)
          edge = *failedAt;
        r->loop()->call([r, self = shared_from_this(), edge]() {
          self->EnterState(ePathFailed, r->Now());
          self->m_PathSet->HandlePathBuildFailedAt(self, edge);
        });
      }

      // TODO: meaningful return value?
      return true;
    }  // namespace path

    void
    Path::EnterState(PathStatus st, llarp_time_t now)
    {
      if (st == ePathFailed)
      {
        _status = st;
        return;
      }
      if (st == ePathExpired && _status == ePathBuilding)
      {
        _status = st;
        m_PathSet->HandlePathBuildTimeout(shared_from_this());
      }
      else if (st == ePathBuilding)
      {
        LogInfo("path ", Name(), " is building");
        buildStarted = now;
      }
      else if (st == ePathEstablished && _status == ePathBuilding)
      {
        LogInfo("path ", Name(), " is built, took ", now - buildStarted);
      }
      else if (st == ePathTimeout && _status == ePathEstablished)
      {
        LogInfo("path ", Name(), " died");
        _status = st;
        m_PathSet->HandlePathDied(shared_from_this());
      }
      else if (st == ePathEstablished && _status == ePathTimeout)
      {
        LogInfo("path ", Name(), " reanimated");
      }
      _status = st;
    }

    util::StatusObject
    PathHopConfig::ExtractStatus() const
    {
      util::StatusObject obj{
          {"lifetime", to_json(lifetime)},
          {"router", rc.pubkey.ToHex()},
          {"txid", txID.ToHex()},
          {"rxid", rxID.ToHex()}};
      return obj;
    }

    util::StatusObject
    Path::ExtractStatus() const
    {
      auto now = llarp::time_now_ms();

      util::StatusObject obj{
          {"intro", intro.ExtractStatus()},
          {"lastRecvMsg", to_json(m_LastRecvMessage)},
          {"lastLatencyTest", to_json(m_LastLatencyTestTime)},
          {"buildStarted", to_json(buildStarted)},
          {"expired", Expired(now)},
          {"expiresSoon", ExpiresSoon(now)},
          {"expiresAt", to_json(ExpireTime())},
          {"ready", IsReady()},
          {"txRateCurrent", m_LastTXRate},
          {"rxRateCurrent", m_LastRXRate},
          {"replayTX", m_UpstreamReplayFilter.Size()},
          {"replayRX", m_DownstreamReplayFilter.Size()},
          {"hasExit", SupportsAnyRoles(ePathRoleExit)}};

      std::vector<util::StatusObject> hopsObj;
      std::transform(
          hops.begin(),
          hops.end(),
          std::back_inserter(hopsObj),
          [](const auto& hop) -> util::StatusObject { return hop.ExtractStatus(); });
      obj["hops"] = hopsObj;

      switch (_status)
      {
        case ePathBuilding:
          obj["status"] = "building";
          break;
        case ePathEstablished:
          obj["status"] = "established";
          break;
        case ePathTimeout:
          obj["status"] = "timeout";
          break;
        case ePathExpired:
          obj["status"] = "expired";
          break;
        case ePathFailed:
          obj["status"] = "failed";
          break;
        case ePathIgnore:
          obj["status"] = "ignored";
          break;
        default:
          obj["status"] = "unknown";
          break;
      }
      return obj;
    }

    void
    Path::Rebuild()
    {
      std::vector<RouterContact> newHops;
      for (const auto& hop : hops)
        newHops.emplace_back(hop.rc);
      LogInfo(Name(), " rebuilding on ", ShortName());
      m_PathSet->Build(newHops);
    }

    void
    Path::Tick(llarp_time_t now, AbstractRouter* r)
    {
      if (Expired(now))
        return;

      m_LastRXRate = m_RXRate;
      m_LastTXRate = m_TXRate;

      m_RXRate = 0;
      m_TXRate = 0;

      if (_status == ePathBuilding)
      {
        if (buildStarted == 0s)
          return;
        if (now >= buildStarted)
        {
          const auto dlt = now - buildStarted;
          if (dlt >= path::build_timeout)
          {
            LogWarn(Name(), " waited for ", dlt, " and no path was built");
            r->routerProfiling().MarkPathFail(this);
            EnterState(ePathExpired, now);
            return;
          }
        }
      }
      // check to see if this path is dead
      if (_status == ePathEstablished)
      {
        auto dlt = now - m_LastLatencyTestTime;
        if (dlt > path::latency_interval && m_LastLatencyTestID == 0)
        {
          // bail doing test if we are active
          if (now - m_LastRecvMessage < path::latency_interval)
            return;
          routing::PathLatencyMessage latency;
          latency.T = randint();
          m_LastLatencyTestID = latency.T;
          m_LastLatencyTestTime = now;
          SendRoutingMessage(latency, r);
          FlushUpstream(r);
          return;
        }
        dlt = now - m_LastRecvMessage;
        if (dlt >= path::alive_timeout)
        {
          LogWarn(Name(), " waited for ", dlt, " and path looks dead");
          r->routerProfiling().MarkPathFail(this);
          EnterState(ePathTimeout, now);
        }
      }
    }

    void
    Path::HandleAllUpstream(std::vector<RelayUpstreamMessage> msgs, AbstractRouter* r)
    {
      for (const auto& msg : msgs)
      {
        if (r->SendToOrQueue(Upstream(), &msg))
        {
          m_TXRate += msg.X.size();
        }
        else
        {
          LogDebug("failed to send upstream to ", Upstream());
        }
      }
      r->linkManager().PumpLinks();
    }

    void
    Path::UpstreamWork(TrafficQueue_ptr msgs, AbstractRouter* r)
    {
      std::vector<RelayUpstreamMessage> sendmsgs(msgs->size());
      size_t idx = 0;
      for (auto& ev : *msgs)
      {
        const llarp_buffer_t buf(ev.first);
        TunnelNonce n = ev.second;
        for (const auto& hop : hops)
        {
          CryptoManager::instance()->xchacha20(buf, hop.shared, n);
          n ^= hop.nonceXOR;
        }
        auto& msg = sendmsgs[idx];
        msg.X = buf;
        msg.Y = ev.second;
        msg.pathid = TXID();
        ++idx;
      }
      r->loop()->call([self = shared_from_this(), data = std::move(sendmsgs), r]() mutable {
        self->HandleAllUpstream(std::move(data), r);
      });
    }

    void
    Path::FlushUpstream(AbstractRouter* r)
    {
      if (m_UpstreamQueue && not m_UpstreamQueue->empty())
      {
        TrafficQueue_ptr data = nullptr;
        std::swap(m_UpstreamQueue, data);
        r->QueueWork(
            [self = shared_from_this(), data, r]() { self->UpstreamWork(std::move(data), r); });
      }
    }

    void
    Path::FlushDownstream(AbstractRouter* r)
    {
      if (m_DownstreamQueue && not m_DownstreamQueue->empty())
      {
        TrafficQueue_ptr data = nullptr;
        std::swap(m_DownstreamQueue, data);
        r->QueueWork(
            [self = shared_from_this(), data, r]() { self->DownstreamWork(std::move(data), r); });
      }
    }

    bool
    Path::Expired(llarp_time_t now) const
    {
      if (_status == ePathFailed)
        return true;
      if (_status == ePathBuilding)
        return false;
      if (_status == ePathEstablished || _status == ePathTimeout)
      {
        return now >= ExpireTime();
      }
      return true;
    }

    std::string
    Path::Name() const
    {
      std::stringstream ss;
      ss << "TX=" << TXID() << " RX=" << RXID();
      if (m_PathSet)
        ss << " on " << m_PathSet->Name();
      return ss.str();
    }

    void
    Path::DownstreamWork(TrafficQueue_ptr msgs, AbstractRouter* r)
    {
      std::vector<RelayDownstreamMessage> sendMsgs(msgs->size());
      size_t idx = 0;
      for (auto& ev : *msgs)
      {
        const llarp_buffer_t buf(ev.first);
        sendMsgs[idx].Y = ev.second;
        for (const auto& hop : hops)
        {
          sendMsgs[idx].Y ^= hop.nonceXOR;
          CryptoManager::instance()->xchacha20(buf, hop.shared, sendMsgs[idx].Y);
        }
        sendMsgs[idx].X = buf;
        ++idx;
      }
      r->loop()->call([self = shared_from_this(), msgs = std::move(sendMsgs), r]() mutable {
        self->HandleAllDownstream(std::move(msgs), r);
      });
    }

    void
    Path::HandleAllDownstream(std::vector<RelayDownstreamMessage> msgs, AbstractRouter* r)
    {
      for (const auto& msg : msgs)
      {
        const llarp_buffer_t buf{msg.X};
        m_RXRate += buf.sz;
        if (HandleRoutingMessage(buf, r))
        {
          r->loop()->wakeup();
          m_LastRecvMessage = r->Now();
        }
      }
    }

    bool
    Path::HandleRoutingMessage(const llarp_buffer_t& buf, AbstractRouter* r)
    {
      if (!r->ParseRoutingMessageBuffer(buf, this, RXID()))
      {
        LogWarn("Failed to parse inbound routing message");
        return false;
      }
      return true;
    }

    bool
    Path::HandleUpdateExitVerifyMessage(
        const routing::UpdateExitVerifyMessage& msg, AbstractRouter* r)
    {
      (void)r;
      if (m_UpdateExitTX && msg.T == m_UpdateExitTX)
      {
        if (m_ExitUpdated)
          return m_ExitUpdated(shared_from_this());
      }
      if (m_CloseExitTX && msg.T == m_CloseExitTX)
      {
        if (m_ExitClosed)
          return m_ExitClosed(shared_from_this());
      }
      return false;
    }

    bool
    Path::SendRoutingMessage(const routing::IMessage& msg, AbstractRouter* r)
    {
      std::array<byte_t, MAX_LINK_MSG_SIZE / 2> tmp;
      llarp_buffer_t buf(tmp);
      // should help prevent bad paths with uninitialized members
      // FIXME: Why would we get uninitialized IMessages?
      if (msg.version != LLARP_PROTO_VERSION)
        return false;
      if (!msg.BEncode(&buf))
      {
        LogError("Bencode failed");
        DumpBuffer(buf);
        return false;
      }
      // make nonce
      TunnelNonce N;
      N.Randomize();
      buf.sz = buf.cur - buf.base;
      // pad smaller messages
      if (buf.sz < pad_size)
      {
        // randomize padding
        CryptoManager::instance()->randbytes(buf.cur, pad_size - buf.sz);
        buf.sz = pad_size;
      }
      buf.cur = buf.base;
      LogDebug("send routing message ", msg.S, " with ", buf.sz, " bytes to endpoint ", Endpoint());
      return HandleUpstream(buf, N, r);
    }

    bool
    Path::HandlePathTransferMessage(
        const routing::PathTransferMessage& /*msg*/, AbstractRouter* /*r*/)
    {
      LogWarn("unwarranted path transfer message on tx=", TXID(), " rx=", RXID());
      return false;
    }

    bool
    Path::HandleDataDiscardMessage(const routing::DataDiscardMessage& msg, AbstractRouter* r)
    {
      MarkActive(r->Now());
      if (m_DropHandler)
        return m_DropHandler(shared_from_this(), msg.P, msg.S);
      return true;
    }

    bool
    Path::HandlePathConfirmMessage(AbstractRouter* r)
    {
      LogDebug("Path Build Confirm, path: ", ShortName());
      const auto now = llarp::time_now_ms();
      if (_status == ePathBuilding)
      {
        // finish initializing introduction
        intro.expiresAt = buildStarted + hops[0].lifetime;

        r->routerProfiling().MarkPathSuccess(this);

        // persist session with upstream router until the path is done
        r->PersistSessionUntil(Upstream(), intro.expiresAt);
        MarkActive(now);
        // send path latency test
        routing::PathLatencyMessage latency;
        latency.T = randint();
        latency.S = NextSeqNo();
        m_LastLatencyTestID = latency.T;
        m_LastLatencyTestTime = now;
        if (!SendRoutingMessage(latency, r))
          return false;
        FlushUpstream(r);
        return true;
      }
      LogWarn("got unwarranted path confirm message on tx=", RXID(), " rx=", RXID());
      return false;
    }

    bool
    Path::HandlePathConfirmMessage(const routing::PathConfirmMessage& /*msg*/, AbstractRouter* r)
    {
      return HandlePathConfirmMessage(r);
    }

    bool
    Path::HandleHiddenServiceFrame(const service::ProtocolFrame& frame)
    {
      MarkActive(m_PathSet->Now());
      return m_DataHandler && m_DataHandler(shared_from_this(), frame);
    }

    bool
    Path::HandlePathLatencyMessage(const routing::PathLatencyMessage& msg, AbstractRouter* r)
    {
      const auto now = r->Now();
      MarkActive(now);
      if (msg.L == m_LastLatencyTestID)
      {
        intro.latency = now - m_LastLatencyTestTime;
        m_LastLatencyTestID = 0;
        EnterState(ePathEstablished, now);
        if (m_BuiltHook)
          m_BuiltHook(shared_from_this());
        m_BuiltHook = nullptr;
        LogDebug("path latency is now ", intro.latency, " for ", Name());
        return true;
      }

      LogWarn("unwarranted path latency message via ", Upstream());
      return false;
    }

    /// this is the Client's side of handling a DHT message. it's handled
    /// in-place.
    bool
    Path::HandleDHTMessage(const dht::IMessage& msg, AbstractRouter* r)
    {
      MarkActive(r->Now());
      routing::DHTMessage reply;
      if (!msg.HandleMessage(r->dht(), reply.M))
        return false;
      if (reply.M.size())
        return SendRoutingMessage(reply, r);
      return true;
    }

    bool
    Path::HandleCloseExitMessage(const routing::CloseExitMessage& msg, AbstractRouter* /*r*/)
    {
      /// allows exits to close from their end
      if (SupportsAnyRoles(ePathRoleExit | ePathRoleSVC))
      {
        if (msg.Verify(EndpointPubKey()))
        {
          LogInfo(Name(), " had its exit closed");
          _role &= ~ePathRoleExit;
          return true;
        }

        LogError(Name(), " CXM from exit with bad signature");
      }
      else
        LogError(Name(), " unwarranted CXM");
      return false;
    }

    bool
    Path::SendExitRequest(const routing::ObtainExitMessage& msg, AbstractRouter* r)
    {
      LogInfo(Name(), " sending exit request to ", Endpoint());
      m_ExitObtainTX = msg.T;
      return SendRoutingMessage(msg, r);
    }

    bool
    Path::SendExitClose(const routing::CloseExitMessage& msg, AbstractRouter* r)
    {
      LogInfo(Name(), " closing exit to ", Endpoint());
      // mark as not exit anymore
      _role &= ~ePathRoleExit;
      return SendRoutingMessage(msg, r);
    }

    bool
    Path::HandleObtainExitMessage(const routing::ObtainExitMessage& msg, AbstractRouter* r)
    {
      (void)msg;
      (void)r;
      LogError(Name(), " got unwarranted OXM");
      return false;
    }

    bool
    Path::HandleUpdateExitMessage(const routing::UpdateExitMessage& msg, AbstractRouter* r)
    {
      (void)msg;
      (void)r;
      LogError(Name(), " got unwarranted UXM");
      return false;
    }

    bool
    Path::HandleRejectExitMessage(const routing::RejectExitMessage& msg, AbstractRouter* r)
    {
      if (m_ExitObtainTX && msg.T == m_ExitObtainTX)
      {
        if (!msg.Verify(EndpointPubKey()))
        {
          LogError(Name(), "RXM invalid signature");
          return false;
        }
        LogInfo(Name(), " ", Endpoint(), " Rejected exit");
        MarkActive(r->Now());
        return InformExitResult(llarp_time_t(msg.B));
      }
      LogError(Name(), " got unwarranted RXM");
      return false;
    }

    bool
    Path::HandleGrantExitMessage(const routing::GrantExitMessage& msg, AbstractRouter* r)
    {
      if (m_ExitObtainTX && msg.T == m_ExitObtainTX)
      {
        if (!msg.Verify(EndpointPubKey()))
        {
          LogError(Name(), " GXM signature failed");
          return false;
        }
        // we now can send exit traffic
        _role |= ePathRoleExit;
        LogInfo(Name(), " ", Endpoint(), " Granted exit");
        MarkActive(r->Now());
        return InformExitResult(0s);
      }
      LogError(Name(), " got unwarranted GXM");
      return false;
    }

    bool
    Path::InformExitResult(llarp_time_t B)
    {
      auto self = shared_from_this();
      bool result = true;
      for (const auto& hook : m_ObtainedExitHooks)
        result &= hook(self, B);
      m_ObtainedExitHooks.clear();
      return result;
    }

    bool
    Path::HandleTransferTrafficMessage(
        const routing::TransferTrafficMessage& msg, AbstractRouter* r)
    {
      // check if we can handle exit data
      if (!SupportsAnyRoles(ePathRoleExit | ePathRoleSVC))
        return false;
      // handle traffic if we have a handler
      if (!m_ExitTrafficHandler)
        return false;
      bool sent = msg.X.size() > 0;
      auto self = shared_from_this();
      for (const auto& pkt : msg.X)
      {
        if (pkt.size() <= 8)
          return false;
        uint64_t counter = bufbe64toh(pkt.data());
        if (m_ExitTrafficHandler(
                self, llarp_buffer_t(pkt.data() + 8, pkt.size() - 8), counter, msg.protocol))
        {
          MarkActive(r->Now());
          EnterState(ePathEstablished, r->Now());
        }
      }
      return sent;
    }

  }  // namespace path
}  // namespace llarp