Merging upstream version 1.9.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 822 insertions, 0 deletions

diff --git a/doq.cc b/doq.cc
new file mode 100644
index 0000000..247b67a
--- /dev/null
+++ b/doq.cc
@@ -0,0 +1,822 @@
+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "doq.hh"
+
+#ifdef HAVE_DNS_OVER_QUIC
+#include <quiche.h>
+
+#include "dolog.hh"
+#include "iputils.hh"
+#include "misc.hh"
+#include "sstuff.hh"
+#include "threadname.hh"
+
+#include "dnsdist-dnsparser.hh"
+#include "dnsdist-ecs.hh"
+#include "dnsdist-proxy-protocol.hh"
+#include "dnsdist-tcp.hh"
+#include "dnsdist-random.hh"
+
+#include "doq-common.hh"
+
+using namespace dnsdist::doq;
+
+#if 0
+#define DEBUGLOG_ENABLED
+#define DEBUGLOG(x) std::cerr << x << std::endl;
+#else
+#define DEBUGLOG(x)
+#endif
+
+class Connection
+{
+public:
+  Connection(const ComboAddress& peer, QuicheConfig config, QuicheConnection conn) :
+    d_peer(peer), d_conn(std::move(conn)), d_config(std::move(config))
+  {
+  }
+  Connection(const Connection&) = delete;
+  Connection(Connection&&) = default;
+  Connection& operator=(const Connection&) = delete;
+  Connection& operator=(Connection&&) = default;
+  ~Connection() = default;
+
+  ComboAddress d_peer;
+  QuicheConnection d_conn;
+  QuicheConfig d_config;
+
+  std::unordered_map<uint64_t, PacketBuffer> d_streamBuffers;
+  std::unordered_map<uint64_t, PacketBuffer> d_streamOutBuffers;
+};
+
+static void sendBackDOQUnit(DOQUnitUniquePtr&& unit, const char* description);
+
+struct DOQServerConfig
+{
+  DOQServerConfig(QuicheConfig&& config_, uint32_t internalPipeBufferSize) :
+    config(std::move(config_))
+  {
+    {
+      auto [sender, receiver] = pdns::channel::createObjectQueue<DOQUnit>(pdns::channel::SenderBlockingMode::SenderNonBlocking, pdns::channel::ReceiverBlockingMode::ReceiverNonBlocking, internalPipeBufferSize);
+      d_responseSender = std::move(sender);
+      d_responseReceiver = std::move(receiver);
+    }
+  }
+  DOQServerConfig(const DOQServerConfig&) = delete;
+  DOQServerConfig(DOQServerConfig&&) = default;
+  DOQServerConfig& operator=(const DOQServerConfig&) = delete;
+  DOQServerConfig& operator=(DOQServerConfig&&) = default;
+  ~DOQServerConfig() = default;
+
+  using ConnectionsMap = std::map<PacketBuffer, Connection>;
+
+  LocalHolders holders;
+  ConnectionsMap d_connections;
+  QuicheConfig config;
+  ClientState* clientState{nullptr};
+  std::shared_ptr<DOQFrontend> df{nullptr};
+  pdns::channel::Sender<DOQUnit> d_responseSender;
+  pdns::channel::Receiver<DOQUnit> d_responseReceiver;
+};
+
+/* these might seem useless, but they are needed because
+   they need to be declared _after_ the definition of DOQServerConfig
+   so that we can use a unique_ptr in DOQFrontend */
+DOQFrontend::DOQFrontend() = default;
+DOQFrontend::~DOQFrontend() = default;
+
+class DOQTCPCrossQuerySender final : public TCPQuerySender
+{
+public:
+  DOQTCPCrossQuerySender() = default;
+
+  [[nodiscard]] bool active() const override
+  {
+    return true;
+  }
+
+  void handleResponse([[maybe_unused]] const struct timeval& now, TCPResponse&& response) override
+  {
+    if (!response.d_idstate.doqu) {
+      return;
+    }
+
+    auto unit = std::move(response.d_idstate.doqu);
+    if (unit->dsc == nullptr) {
+      return;
+    }
+
+    unit->response = std::move(response.d_buffer);
+    unit->ids = std::move(response.d_idstate);
+    DNSResponse dnsResponse(unit->ids, unit->response, unit->downstream);
+
+    dnsheader cleartextDH{};
+    memcpy(&cleartextDH, dnsResponse.getHeader().get(), sizeof(cleartextDH));
+
+    if (!response.isAsync()) {
+
+      static thread_local LocalStateHolder<vector<DNSDistResponseRuleAction>> localRespRuleActions = g_respruleactions.getLocal();
+      static thread_local LocalStateHolder<vector<DNSDistResponseRuleAction>> localCacheInsertedRespRuleActions = g_cacheInsertedRespRuleActions.getLocal();
+
+      dnsResponse.ids.doqu = std::move(unit);
+
+      if (!processResponse(dnsResponse.ids.doqu->response, *localRespRuleActions, *localCacheInsertedRespRuleActions, dnsResponse, false)) {
+        if (dnsResponse.ids.doqu) {
+
+          sendBackDOQUnit(std::move(dnsResponse.ids.doqu), "Response dropped by rules");
+        }
+        return;
+      }
+
+      if (dnsResponse.isAsynchronous()) {
+        return;
+      }
+
+      unit = std::move(dnsResponse.ids.doqu);
+    }
+
+    if (!unit->ids.selfGenerated) {
+      double udiff = unit->ids.queryRealTime.udiff();
+      vinfolog("Got answer from %s, relayed to %s (quic, %d bytes), took %f us", unit->downstream->d_config.remote.toStringWithPort(), unit->ids.origRemote.toStringWithPort(), unit->response.size(), udiff);
+
+      auto backendProtocol = unit->downstream->getProtocol();
+      if (backendProtocol == dnsdist::Protocol::DoUDP && unit->tcp) {
+        backendProtocol = dnsdist::Protocol::DoTCP;
+      }
+      handleResponseSent(unit->ids, udiff, unit->ids.origRemote, unit->downstream->d_config.remote, unit->response.size(), cleartextDH, backendProtocol, true);
+    }
+
+    ++dnsdist::metrics::g_stats.responses;
+    if (unit->ids.cs != nullptr) {
+      ++unit->ids.cs->responses;
+    }
+
+    sendBackDOQUnit(std::move(unit), "Cross-protocol response");
+  }
+
+  void handleXFRResponse(const struct timeval& now, TCPResponse&& response) override
+  {
+    return handleResponse(now, std::move(response));
+  }
+
+  void notifyIOError([[maybe_unused]] const struct timeval& now, TCPResponse&& response) override
+  {
+    if (!response.d_idstate.doqu) {
+      return;
+    }
+
+    auto unit = std::move(response.d_idstate.doqu);
+    if (unit->dsc == nullptr) {
+      return;
+    }
+
+    /* this will signal an error */
+    unit->response.clear();
+    unit->ids = std::move(response.d_idstate);
+    sendBackDOQUnit(std::move(unit), "Cross-protocol error");
+  }
+};
+
+class DOQCrossProtocolQuery : public CrossProtocolQuery
+{
+public:
+  DOQCrossProtocolQuery(DOQUnitUniquePtr&& unit, bool isResponse)
+  {
+    if (isResponse) {
+      /* happens when a response becomes async */
+      query = InternalQuery(std::move(unit->response), std::move(unit->ids));
+    }
+    else {
+      /* we need to duplicate the query here because we might need
+         the existing query later if we get a truncated answer */
+      query = InternalQuery(PacketBuffer(unit->query), std::move(unit->ids));
+    }
+
+    /* it might have been moved when we moved unit->ids */
+    if (unit) {
+      query.d_idstate.doqu = std::move(unit);
+    }
+
+    /* we _could_ remove it from the query buffer and put in query's d_proxyProtocolPayload,
+       clearing query.d_proxyProtocolPayloadAdded and unit->proxyProtocolPayloadSize.
+       Leave it for now because we know that the onky case where the payload has been
+       added is when we tried over UDP, got a TC=1 answer and retried over TCP/DoT,
+       and we know the TCP/DoT code can handle it. */
+    query.d_proxyProtocolPayloadAdded = query.d_idstate.doqu->proxyProtocolPayloadSize > 0;
+    downstream = query.d_idstate.doqu->downstream;
+  }
+
+  void handleInternalError()
+  {
+    sendBackDOQUnit(std::move(query.d_idstate.doqu), "DOQ internal error");
+  }
+
+  std::shared_ptr<TCPQuerySender> getTCPQuerySender() override
+  {
+    query.d_idstate.doqu->downstream = downstream;
+    return s_sender;
+  }
+
+  DNSQuestion getDQ() override
+  {
+    auto& ids = query.d_idstate;
+    DNSQuestion dnsQuestion(ids, query.d_buffer);
+    return dnsQuestion;
+  }
+
+  DNSResponse getDR() override
+  {
+    auto& ids = query.d_idstate;
+    DNSResponse dnsResponse(ids, query.d_buffer, downstream);
+    return dnsResponse;
+  }
+
+  DOQUnitUniquePtr&& releaseDU()
+  {
+    return std::move(query.d_idstate.doqu);
+  }
+
+private:
+  static std::shared_ptr<DOQTCPCrossQuerySender> s_sender;
+};
+
+std::shared_ptr<DOQTCPCrossQuerySender> DOQCrossProtocolQuery::s_sender = std::make_shared<DOQTCPCrossQuerySender>();
+
+static bool tryWriteResponse(Connection& conn, const uint64_t streamID, PacketBuffer& response)
+{
+  size_t pos = 0;
+  while (pos < response.size()) {
+    auto res = quiche_conn_stream_send(conn.d_conn.get(), streamID, &response.at(pos), response.size() - pos, true);
+    if (res == QUICHE_ERR_DONE) {
+      response.erase(response.begin(), response.begin() + static_cast<ssize_t>(pos));
+      return false;
+    }
+    if (res < 0) {
+      quiche_conn_stream_shutdown(conn.d_conn.get(), streamID, QUICHE_SHUTDOWN_WRITE, static_cast<uint64_t>(DOQ_Error_Codes::DOQ_INTERNAL_ERROR));
+      return true;
+    }
+    pos += res;
+  }
+
+  return true;
+}
+
+static void handleResponse(DOQFrontend& frontend, Connection& conn, const uint64_t streamID, PacketBuffer& response)
+{
+  if (response.empty()) {
+    ++frontend.d_errorResponses;
+    quiche_conn_stream_shutdown(conn.d_conn.get(), streamID, QUICHE_SHUTDOWN_WRITE, static_cast<uint64_t>(DOQ_Error_Codes::DOQ_UNSPECIFIED_ERROR));
+    return;
+  }
+  ++frontend.d_validResponses;
+  auto responseSize = static_cast<uint16_t>(response.size());
+  const std::array<uint8_t, 2> sizeBytes = {static_cast<uint8_t>(responseSize / 256), static_cast<uint8_t>(responseSize % 256)};
+  response.insert(response.begin(), sizeBytes.begin(), sizeBytes.end());
+  if (!tryWriteResponse(conn, streamID, response)) {
+    conn.d_streamOutBuffers[streamID] = std::move(response);
+  }
+}
+
+void DOQFrontend::setup()
+{
+  auto config = QuicheConfig(quiche_config_new(QUICHE_PROTOCOL_VERSION), quiche_config_free);
+  d_quicheParams.d_alpn = std::string(DOQ_ALPN.begin(), DOQ_ALPN.end());
+  configureQuiche(config, d_quicheParams, false);
+  d_server_config = std::make_unique<DOQServerConfig>(std::move(config), d_internalPipeBufferSize);
+}
+
+void DOQFrontend::reloadCertificates()
+{
+  auto config = QuicheConfig(quiche_config_new(QUICHE_PROTOCOL_VERSION), quiche_config_free);
+  d_quicheParams.d_alpn = std::string(DOQ_ALPN.begin(), DOQ_ALPN.end());
+  configureQuiche(config, d_quicheParams, false);
+  std::atomic_store_explicit(&d_server_config->config, std::move(config), std::memory_order_release);
+}
+
+static std::optional<std::reference_wrapper<Connection>> getConnection(DOQServerConfig::ConnectionsMap& connMap, const PacketBuffer& connID)
+{
+  auto iter = connMap.find(connID);
+  if (iter == connMap.end()) {
+    return std::nullopt;
+  }
+  return iter->second;
+}
+
+static void sendBackDOQUnit(DOQUnitUniquePtr&& unit, const char* description)
+{
+  if (unit->dsc == nullptr) {
+    return;
+  }
+  try {
+    if (!unit->dsc->d_responseSender.send(std::move(unit))) {
+      ++dnsdist::metrics::g_stats.doqResponsePipeFull;
+      vinfolog("Unable to pass a %s to the DoQ worker thread because the pipe is full", description);
+    }
+  }
+  catch (const std::exception& e) {
+    vinfolog("Unable to pass a %s to the DoQ worker thread because we couldn't write to the pipe: %s", description, e.what());
+  }
+}
+
+static std::optional<std::reference_wrapper<Connection>> createConnection(DOQServerConfig& config, const PacketBuffer& serverSideID, const PacketBuffer& originalDestinationID, const ComboAddress& local, const ComboAddress& peer)
+{
+  auto quicheConfig = std::atomic_load_explicit(&config.config, std::memory_order_acquire);
+  auto quicheConn = QuicheConnection(quiche_accept(serverSideID.data(), serverSideID.size(),
+                                                   originalDestinationID.data(), originalDestinationID.size(),
+                                                   // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
+                                                   reinterpret_cast<const struct sockaddr*>(&local),
+                                                   local.getSocklen(),
+                                                   // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
+                                                   reinterpret_cast<const struct sockaddr*>(&peer),
+                                                   peer.getSocklen(),
+                                                   quicheConfig.get()),
+                                     quiche_conn_free);
+
+  if (config.df && !config.df->d_quicheParams.d_keyLogFile.empty()) {
+    quiche_conn_set_keylog_path(quicheConn.get(), config.df->d_quicheParams.d_keyLogFile.c_str());
+  }
+
+  auto conn = Connection(peer, std::move(quicheConfig), std::move(quicheConn));
+  auto pair = config.d_connections.emplace(serverSideID, std::move(conn));
+  return pair.first->second;
+}
+
+std::unique_ptr<CrossProtocolQuery> getDOQCrossProtocolQueryFromDQ(DNSQuestion& dnsQuestion, bool isResponse)
+{
+  if (!dnsQuestion.ids.doqu) {
+    throw std::runtime_error("Trying to create a DoQ cross protocol query without a valid DoQ unit");
+  }
+
+  auto unit = std::move(dnsQuestion.ids.doqu);
+  if (&dnsQuestion.ids != &unit->ids) {
+    unit->ids = std::move(dnsQuestion.ids);
+  }
+
+  unit->ids.origID = dnsQuestion.getHeader()->id;
+
+  if (!isResponse) {
+    if (unit->query.data() != dnsQuestion.getMutableData().data()) {
+      unit->query = std::move(dnsQuestion.getMutableData());
+    }
+  }
+  else {
+    if (unit->response.data() != dnsQuestion.getMutableData().data()) {
+      unit->response = std::move(dnsQuestion.getMutableData());
+    }
+  }
+
+  return std::make_unique<DOQCrossProtocolQuery>(std::move(unit), isResponse);
+}
+
+static void processDOQQuery(DOQUnitUniquePtr&& doqUnit)
+{
+  const auto handleImmediateResponse = [](DOQUnitUniquePtr&& unit, [[maybe_unused]] const char* reason) {
+    DEBUGLOG("handleImmediateResponse() reason=" << reason);
+    auto conn = getConnection(unit->dsc->df->d_server_config->d_connections, unit->serverConnID);
+    handleResponse(*unit->dsc->df, *conn, unit->streamID, unit->response);
+    unit->ids.doqu.reset();
+  };
+
+  auto& ids = doqUnit->ids;
+  ids.doqu = std::move(doqUnit);
+  auto& unit = ids.doqu;
+  uint16_t queryId = 0;
+  ComboAddress remote;
+
+  try {
+
+    remote = unit->ids.origRemote;
+    DOQServerConfig* dsc = unit->dsc;
+    auto& holders = dsc->holders;
+    ClientState& clientState = *dsc->clientState;
+
+    if (!holders.acl->match(remote)) {
+      vinfolog("Query from %s (DoQ) dropped because of ACL", remote.toStringWithPort());
+      ++dnsdist::metrics::g_stats.aclDrops;
+      unit->response.clear();
+
+      handleImmediateResponse(std::move(unit), "DoQ query dropped because of ACL");
+      return;
+    }
+
+    if (unit->query.size() < sizeof(dnsheader)) {
+      ++dnsdist::metrics::g_stats.nonCompliantQueries;
+      ++clientState.nonCompliantQueries;
+      unit->response.clear();
+
+      handleImmediateResponse(std::move(unit), "DoQ non-compliant query");
+      return;
+    }
+
+    ++clientState.queries;
+    ++dnsdist::metrics::g_stats.queries;
+    unit->ids.queryRealTime.start();
+
+    {
+      /* don't keep that pointer around, it will be invalidated if the buffer is ever resized */
+      dnsheader_aligned dnsHeader(unit->query.data());
+
+      if (!checkQueryHeaders(*dnsHeader, clientState)) {
+        dnsdist::PacketMangling::editDNSHeaderFromPacket(unit->query, [](dnsheader& header) {
+          header.rcode = RCode::ServFail;
+          header.qr = true;
+          return true;
+        });
+        unit->response = std::move(unit->query);
+
+        handleImmediateResponse(std::move(unit), "DoQ invalid headers");
+        return;
+      }
+
+      if (dnsHeader->qdcount == 0) {
+        dnsdist::PacketMangling::editDNSHeaderFromPacket(unit->query, [](dnsheader& header) {
+          header.rcode = RCode::NotImp;
+          header.qr = true;
+          return true;
+        });
+        unit->response = std::move(unit->query);
+
+        handleImmediateResponse(std::move(unit), "DoQ empty query");
+        return;
+      }
+
+      queryId = ntohs(dnsHeader->id);
+    }
+
+    auto downstream = unit->downstream;
+    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
+    unit->ids.qname = DNSName(reinterpret_cast<const char*>(unit->query.data()), static_cast<int>(unit->query.size()), sizeof(dnsheader), false, &unit->ids.qtype, &unit->ids.qclass);
+    DNSQuestion dnsQuestion(unit->ids, unit->query);
+    dnsdist::PacketMangling::editDNSHeaderFromPacket(dnsQuestion.getMutableData(), [&ids](dnsheader& header) {
+      const uint16_t* flags = getFlagsFromDNSHeader(&header);
+      ids.origFlags = *flags;
+      return true;
+    });
+    unit->ids.cs = &clientState;
+
+    auto result = processQuery(dnsQuestion, holders, downstream);
+    if (result == ProcessQueryResult::Drop) {
+      handleImmediateResponse(std::move(unit), "DoQ dropped query");
+      return;
+    }
+    if (result == ProcessQueryResult::Asynchronous) {
+      return;
+    }
+    if (result == ProcessQueryResult::SendAnswer) {
+      if (unit->response.empty()) {
+        unit->response = std::move(unit->query);
+      }
+      if (unit->response.size() >= sizeof(dnsheader)) {
+        const dnsheader_aligned dnsHeader(unit->response.data());
+
+        handleResponseSent(unit->ids.qname, QType(unit->ids.qtype), 0., unit->ids.origDest, ComboAddress(), unit->response.size(), *dnsHeader, dnsdist::Protocol::DoQ, dnsdist::Protocol::DoQ, false);
+      }
+      handleImmediateResponse(std::move(unit), "DoQ self-answered response");
+      return;
+    }
+
+    ++dnsdist::metrics::g_stats.responses;
+    if (unit->ids.cs != nullptr) {
+      ++unit->ids.cs->responses;
+    }
+
+    if (result != ProcessQueryResult::PassToBackend) {
+      handleImmediateResponse(std::move(unit), "DoQ no backend available");
+      return;
+    }
+
+    if (downstream == nullptr) {
+      handleImmediateResponse(std::move(unit), "DoQ no backend available");
+      return;
+    }
+
+    unit->downstream = downstream;
+
+    std::string proxyProtocolPayload;
+    /* we need to do this _before_ creating the cross protocol query because
+       after that the buffer will have been moved */
+    if (downstream->d_config.useProxyProtocol) {
+      proxyProtocolPayload = getProxyProtocolPayload(dnsQuestion);
+    }
+
+    unit->ids.origID = htons(queryId);
+    unit->tcp = true;
+
+    /* this moves unit->ids, careful! */
+    auto cpq = std::make_unique<DOQCrossProtocolQuery>(std::move(unit), false);
+    cpq->query.d_proxyProtocolPayload = std::move(proxyProtocolPayload);
+
+    if (downstream->passCrossProtocolQuery(std::move(cpq))) {
+      return;
+    }
+    // NOLINTNEXTLINE(bugprone-use-after-move): it was only moved if the call succeeded
+    unit = cpq->releaseDU();
+    handleImmediateResponse(std::move(unit), "DoQ internal error");
+    return;
+  }
+  catch (const std::exception& e) {
+    vinfolog("Got an error in DOQ question thread while parsing a query from %s, id %d: %s", remote.toStringWithPort(), queryId, e.what());
+    handleImmediateResponse(std::move(unit), "DoQ internal error");
+    return;
+  }
+}
+
+static void doq_dispatch_query(DOQServerConfig& dsc, PacketBuffer&& query, const ComboAddress& local, const ComboAddress& remote, const PacketBuffer& serverConnID, const uint64_t streamID)
+{
+  try {
+    auto unit = std::make_unique<DOQUnit>(std::move(query));
+    unit->dsc = &dsc;
+    unit->ids.origDest = local;
+    unit->ids.origRemote = remote;
+    unit->ids.protocol = dnsdist::Protocol::DoQ;
+    unit->serverConnID = serverConnID;
+    unit->streamID = streamID;
+
+    processDOQQuery(std::move(unit));
+  }
+  catch (const std::exception& exp) {
+    vinfolog("Had error handling DoQ DNS packet from %s: %s", remote.toStringWithPort(), exp.what());
+  }
+}
+
+static void flushResponses(pdns::channel::Receiver<DOQUnit>& receiver)
+{
+  for (;;) {
+    try {
+      auto tmp = receiver.receive();
+      if (!tmp) {
+        return;
+      }
+
+      auto unit = std::move(*tmp);
+      auto conn = getConnection(unit->dsc->df->d_server_config->d_connections, unit->serverConnID);
+      if (conn) {
+        handleResponse(*unit->dsc->df, *conn, unit->streamID, unit->response);
+      }
+    }
+    catch (const std::exception& e) {
+      errlog("Error while processing response received over DoQ: %s", e.what());
+    }
+    catch (...) {
+      errlog("Unspecified error while processing response received over DoQ");
+    }
+  }
+}
+
+static void flushStalledResponses(Connection& conn)
+{
+  for (auto streamIt = conn.d_streamOutBuffers.begin(); streamIt != conn.d_streamOutBuffers.end();) {
+    const auto& streamID = streamIt->first;
+    auto& response = streamIt->second;
+    if (quiche_conn_stream_writable(conn.d_conn.get(), streamID, response.size()) == 1) {
+      if (tryWriteResponse(conn, streamID, response)) {
+        streamIt = conn.d_streamOutBuffers.erase(streamIt);
+        continue;
+      }
+    }
+    ++streamIt;
+  }
+}
+
+static void handleReadableStream(DOQFrontend& frontend, ClientState& clientState, Connection& conn, uint64_t streamID, const ComboAddress& client, const PacketBuffer& serverConnID)
+{
+  auto& streamBuffer = conn.d_streamBuffers[streamID];
+  while (true) {
+    bool fin = false;
+    auto existingLength = streamBuffer.size();
+    streamBuffer.resize(existingLength + 512);
+    auto received = quiche_conn_stream_recv(conn.d_conn.get(), streamID,
+                                            &streamBuffer.at(existingLength), 512,
+                                            &fin);
+    if (received == 0 || received == QUICHE_ERR_DONE) {
+      streamBuffer.resize(existingLength);
+      return;
+    }
+    if (received < 0) {
+      ++dnsdist::metrics::g_stats.nonCompliantQueries;
+      ++clientState.nonCompliantQueries;
+      quiche_conn_stream_shutdown(conn.d_conn.get(), streamID, QUICHE_SHUTDOWN_WRITE, static_cast<uint64_t>(DOQ_Error_Codes::DOQ_PROTOCOL_ERROR));
+      return;
+    }
+
+    streamBuffer.resize(existingLength + received);
+    if (fin) {
+      break;
+    }
+  }
+
+  if (streamBuffer.size() < (sizeof(uint16_t) + sizeof(dnsheader))) {
+    ++dnsdist::metrics::g_stats.nonCompliantQueries;
+    ++clientState.nonCompliantQueries;
+    quiche_conn_stream_shutdown(conn.d_conn.get(), streamID, QUICHE_SHUTDOWN_WRITE, static_cast<uint64_t>(DOQ_Error_Codes::DOQ_PROTOCOL_ERROR));
+    return;
+  }
+
+  uint16_t payloadLength = streamBuffer.at(0) * 256 + streamBuffer.at(1);
+  streamBuffer.erase(streamBuffer.begin(), streamBuffer.begin() + 2);
+  if (payloadLength != streamBuffer.size()) {
+    ++dnsdist::metrics::g_stats.nonCompliantQueries;
+    ++clientState.nonCompliantQueries;
+    quiche_conn_stream_shutdown(conn.d_conn.get(), streamID, QUICHE_SHUTDOWN_WRITE, static_cast<uint64_t>(DOQ_Error_Codes::DOQ_PROTOCOL_ERROR));
+    return;
+  }
+  DEBUGLOG("Dispatching query");
+  doq_dispatch_query(*(frontend.d_server_config), std::move(streamBuffer), clientState.local, client, serverConnID, streamID);
+  conn.d_streamBuffers.erase(streamID);
+}
+
+static void handleSocketReadable(DOQFrontend& frontend, ClientState& clientState, Socket& sock, PacketBuffer& buffer)
+{
+  // destination connection ID, will have to be sent as original destination connection ID
+  PacketBuffer serverConnID;
+  // source connection ID, will have to be sent as destination connection ID
+  PacketBuffer clientConnID;
+  PacketBuffer tokenBuf;
+  while (true) {
+    ComboAddress client;
+    buffer.resize(4096);
+    if (!sock.recvFromAsync(buffer, client) || buffer.empty()) {
+      return;
+    }
+    DEBUGLOG("Received DoQ datagram of size " << buffer.size() << " from " << client.toStringWithPort());
+
+    uint32_t version{0};
+    uint8_t type{0};
+    std::array<uint8_t, QUICHE_MAX_CONN_ID_LEN> scid{};
+    size_t scid_len = scid.size();
+    std::array<uint8_t, QUICHE_MAX_CONN_ID_LEN> dcid{};
+    size_t dcid_len = dcid.size();
+    std::array<uint8_t, MAX_TOKEN_LEN> token{};
+    size_t token_len = token.size();
+
+    auto res = quiche_header_info(buffer.data(), buffer.size(), LOCAL_CONN_ID_LEN,
+                                  &version, &type,
+                                  scid.data(), &scid_len,
+                                  dcid.data(), &dcid_len,
+                                  token.data(), &token_len);
+    if (res != 0) {
+      DEBUGLOG("Error in quiche_header_info: " << res);
+      continue;
+    }
+
+    serverConnID.assign(dcid.begin(), dcid.begin() + dcid_len);
+    clientConnID.assign(scid.begin(), scid.begin() + scid_len);
+    auto conn = getConnection(frontend.d_server_config->d_connections, serverConnID);
+
+    if (!conn) {
+      DEBUGLOG("Connection not found");
+      if (type != static_cast<uint8_t>(DOQ_Packet_Types::QUIC_PACKET_TYPE_INITIAL)) {
+        DEBUGLOG("Packet is not initial");
+        continue;
+      }
+
+      if (!quiche_version_is_supported(version)) {
+        DEBUGLOG("Unsupported version");
+        ++frontend.d_doqUnsupportedVersionErrors;
+        handleVersionNegociation(sock, clientConnID, serverConnID, client, buffer);
+        continue;
+      }
+
+      if (token_len == 0) {
+        /* stateless retry */
+        DEBUGLOG("No token received");
+        handleStatelessRetry(sock, clientConnID, serverConnID, client, version, buffer);
+        continue;
+      }
+
+      tokenBuf.assign(token.begin(), token.begin() + token_len);
+      auto originalDestinationID = validateToken(tokenBuf, client);
+      if (!originalDestinationID) {
+        ++frontend.d_doqInvalidTokensReceived;
+        DEBUGLOG("Discarding invalid token");
+        continue;
+      }
+
+      DEBUGLOG("Creating a new connection");
+      conn = createConnection(*frontend.d_server_config, serverConnID, *originalDestinationID, clientState.local, client);
+      if (!conn) {
+        continue;
+      }
+    }
+    DEBUGLOG("Connection found");
+    quiche_recv_info recv_info = {
+      // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
+      reinterpret_cast<struct sockaddr*>(&client),
+      client.getSocklen(),
+      // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
+      reinterpret_cast<struct sockaddr*>(&clientState.local),
+      clientState.local.getSocklen(),
+    };
+
+    auto done = quiche_conn_recv(conn->get().d_conn.get(), buffer.data(), buffer.size(), &recv_info);
+    if (done < 0) {
+      continue;
+    }
+
+    if (quiche_conn_is_established(conn->get().d_conn.get()) || quiche_conn_is_in_early_data(conn->get().d_conn.get())) {
+      auto readable = std::unique_ptr<quiche_stream_iter, decltype(&quiche_stream_iter_free)>(quiche_conn_readable(conn->get().d_conn.get()), quiche_stream_iter_free);
+
+      uint64_t streamID = 0;
+      while (quiche_stream_iter_next(readable.get(), &streamID)) {
+        handleReadableStream(frontend, clientState, *conn, streamID, client, serverConnID);
+      }
+
+      flushEgress(sock, conn->get().d_conn, client, buffer);
+    }
+    else {
+      DEBUGLOG("Connection not established");
+    }
+  }
+}
+
+// this is the entrypoint from dnsdist.cc
+void doqThread(ClientState* clientState)
+{
+  try {
+    std::shared_ptr<DOQFrontend>& frontend = clientState->doqFrontend;
+
+    frontend->d_server_config->clientState = clientState;
+    frontend->d_server_config->df = clientState->doqFrontend;
+
+    setThreadName("dnsdist/doq");
+
+    Socket sock(clientState->udpFD);
+    sock.setNonBlocking();
+
+    auto mplexer = std::unique_ptr<FDMultiplexer>(FDMultiplexer::getMultiplexerSilent());
+
+    auto responseReceiverFD = frontend->d_server_config->d_responseReceiver.getDescriptor();
+    mplexer->addReadFD(sock.getHandle(), [](int, FDMultiplexer::funcparam_t&) {});
+    mplexer->addReadFD(responseReceiverFD, [](int, FDMultiplexer::funcparam_t&) {});
+    std::vector<int> readyFDs;
+    PacketBuffer buffer(4096);
+    while (true) {
+      readyFDs.clear();
+      mplexer->getAvailableFDs(readyFDs, 500);
+
+      try {
+        if (std::find(readyFDs.begin(), readyFDs.end(), sock.getHandle()) != readyFDs.end()) {
+          handleSocketReadable(*frontend, *clientState, sock, buffer);
+        }
+
+        if (std::find(readyFDs.begin(), readyFDs.end(), responseReceiverFD) != readyFDs.end()) {
+          flushResponses(frontend->d_server_config->d_responseReceiver);
+        }
+
+        for (auto conn = frontend->d_server_config->d_connections.begin(); conn != frontend->d_server_config->d_connections.end();) {
+          quiche_conn_on_timeout(conn->second.d_conn.get());
+
+          flushEgress(sock, conn->second.d_conn, conn->second.d_peer, buffer);
+
+          if (quiche_conn_is_closed(conn->second.d_conn.get())) {
+#ifdef DEBUGLOG_ENABLED
+            quiche_stats stats;
+            quiche_path_stats path_stats;
+
+            quiche_conn_stats(conn->second.d_conn.get(), &stats);
+            quiche_conn_path_stats(conn->second.d_conn.get(), 0, &path_stats);
+
+            DEBUGLOG("Connection (DoQ) closed, recv=" << stats.recv << " sent=" << stats.sent << " lost=" << stats.lost << " rtt=" << path_stats.rtt << "ns cwnd=" << path_stats.cwnd);
+#endif
+            conn = frontend->d_server_config->d_connections.erase(conn);
+          }
+          else {
+            flushStalledResponses(conn->second);
+            ++conn;
+          }
+        }
+      }
+      catch (const std::exception& exp) {
+        vinfolog("Caught exception in the main DoQ thread: %s", exp.what());
+      }
+      catch (...) {
+        vinfolog("Unknown exception in the main DoQ thread");
+      }
+    }
+  }
+  catch (const std::exception& e) {
+    DEBUGLOG("Caught fatal error in the main DoQ thread: " << e.what());
+  }
+}
+
+#endif /* HAVE_DNS_OVER_QUIC */