3 files changed, 972 insertions, 0 deletions
diff --git a/dom/webtransport/parent/WebTransportParent.cpp b/dom/webtransport/parent/WebTransportParent.cpp
new file mode 100644
index 0000000000..c9f7943cc3
--- /dev/null
+++ b/dom/webtransport/parent/WebTransportParent.cpp
@@ -0,0 +1,836 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebTransportParent.h"
+#include "Http3WebTransportSession.h"
+#include "mozilla/StaticPrefs_network.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ClientInfo.h"
+#include "mozilla/dom/WebTransportBinding.h"
+#include "mozilla/dom/WebTransportLog.h"
+#include "mozilla/net/WebTransportHash.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "nsIEventTarget.h"
+#include "nsIOService.h"
+#include "nsIPrincipal.h"
+#include "nsIWebTransport.h"
+#include "nsStreamUtils.h"
+#include "nsIWebTransportStream.h"
+
+using IPCResult = mozilla::ipc::IPCResult;
+
+namespace mozilla::dom {
+
+NS_IMPL_ISUPPORTS(WebTransportParent, WebTransportSessionEventListener);
+
+using CreateWebTransportPromise =
+    MozPromise<WebTransportReliabilityMode, nsresult, true>;
+WebTransportParent::~WebTransportParent() {
+  LOG(("Destroying WebTransportParent %p", this));
+}
+
+void WebTransportParent::Create(
+    const nsAString& aURL, nsIPrincipal* aPrincipal,
+    const mozilla::Maybe<IPCClientInfo>& aClientInfo, const bool& aDedicated,
+    const bool& aRequireUnreliable, const uint32_t& aCongestionControl,
+    nsTArray<WebTransportHash>&& aServerCertHashes,
+    Endpoint<PWebTransportParent>&& aParentEndpoint,
+    std::function<void(std::tuple<const nsresult&, const uint8_t&>)>&&
+        aResolver) {
+  LOG(("Created WebTransportParent %p %s %s %s congestion=%s", this,
+       NS_ConvertUTF16toUTF8(aURL).get(),
+       aDedicated ? "Dedicated" : "AllowPooling",
+       aRequireUnreliable ? "RequireUnreliable" : "",
+       aCongestionControl ==
+               (uint32_t)dom::WebTransportCongestionControl::Throughput
+           ? "ThroughPut"
+           : (aCongestionControl ==
+                      (uint32_t)dom::WebTransportCongestionControl::Low_latency
+                  ? "Low-Latency"
+                  : "Default")));
+
+  if (!StaticPrefs::network_webtransport_enabled()) {
+    aResolver(ResolveType(
+        NS_ERROR_DOM_NOT_ALLOWED_ERR,
+        static_cast<uint8_t>(WebTransportReliabilityMode::Pending)));
+    return;
+  }
+
+  if (!aParentEndpoint.IsValid()) {
+    aResolver(ResolveType(
+        NS_ERROR_INVALID_ARG,
+        static_cast<uint8_t>(WebTransportReliabilityMode::Pending)));
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(mozilla::net::gIOService);
+  nsresult rv =
+      mozilla::net::gIOService->NewWebTransport(getter_AddRefs(mWebTransport));
+  if (NS_FAILED(rv)) {
+    aResolver(ResolveType(
+        rv, static_cast<uint8_t>(WebTransportReliabilityMode::Pending)));
+    return;
+  }
+
+  mOwningEventTarget = GetCurrentSerialEventTarget();
+  MOZ_ASSERT(aPrincipal);
+  nsCOMPtr<nsIURI> uri;
+  rv = NS_NewURI(getter_AddRefs(uri), aURL);
+  if (NS_FAILED(rv)) {
+    aResolver(ResolveType(
+        NS_ERROR_INVALID_ARG,
+        static_cast<uint8_t>(WebTransportReliabilityMode::Pending)));
+    return;
+  }
+
+  nsTArray<RefPtr<nsIWebTransportHash>> nsServerCertHashes;
+  for (const auto& hash : aServerCertHashes) {
+    nsCString alg = hash.algorithm();
+    nsServerCertHashes.AppendElement(
+        new net::WebTransportHash(alg, hash.value()));
+  }
+
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      "WebTransport AsyncConnect",
+      [self = RefPtr{this}, uri = std::move(uri),
+       nsServerCertHashes = std::move(nsServerCertHashes),
+       principal = RefPtr{aPrincipal},
+       flags = nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+       clientInfo = aClientInfo] {
+        LOG(("WebTransport %p AsyncConnect", self.get()));
+        if (NS_FAILED(self->mWebTransport->AsyncConnectWithClient(
+                uri, std::move(nsServerCertHashes), principal, flags, self,
+                clientInfo))) {
+          LOG(("AsyncConnect failure; we should get OnSessionClosed"));
+        }
+      });
+
+  // Bind to SocketThread for IPC - connection creation/destruction must
+  // hit MainThread, but keep all other traffic on SocketThread.  Note that
+  // we must call aResolver() on this (PBackground) thread.
+  mSocketThread = do_GetService(NS_SOCKETTRANSPORTSERVICE_CONTRACTID, &rv);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+  InvokeAsync(mSocketThread, __func__,
+              [parentEndpoint = std::move(aParentEndpoint), runnable = r,
+               resolver = std::move(aResolver), p = RefPtr{this}]() mutable {
+                {
+                  MutexAutoLock lock(p->mMutex);
+                  p->mResolver = resolver;
+                }
+
+                LOG(("Binding parent endpoint"));
+                if (!parentEndpoint.Bind(p)) {
+                  return CreateWebTransportPromise::CreateAndReject(
+                      NS_ERROR_FAILURE, __func__);
+                }
+                // IPC now holds a ref to parent
+                // Send connection to the server via MainThread
+                NS_DispatchToMainThread(runnable, NS_DISPATCH_NORMAL);
+
+                return CreateWebTransportPromise::CreateAndResolve(
+                    WebTransportReliabilityMode::Supports_unreliable, __func__);
+              })
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [p = RefPtr{this}](
+              const CreateWebTransportPromise::ResolveOrRejectValue& aValue) {
+            if (aValue.IsReject()) {
+              std::function<void(ResolveType)> resolver;
+              {
+                MutexAutoLock lock(p->mMutex);
+                resolver = std::move(p->mResolver);
+              }
+              if (resolver) {
+                resolver(
+                    ResolveType(aValue.RejectValue(),
+                                static_cast<uint8_t>(
+                                    WebTransportReliabilityMode::Pending)));
+              }
+            }
+          });
+}
+
+void WebTransportParent::ActorDestroy(ActorDestroyReason aWhy) {
+  LOG(("ActorDestroy WebTransportParent %d", aWhy));
+}
+
+// We may not receive this response if the child side is destroyed without
+// `Close` or `Shutdown` being explicitly called.
+IPCResult WebTransportParent::RecvClose(const uint32_t& aCode,
+                                        const nsACString& aReason) {
+  LOG(("Close for %p received, code = %u, reason = %s", this, aCode,
+       PromiseFlatCString(aReason).get()));
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_ASSERT(!mClosed);
+    mClosed.Flip();
+  }
+  mWebTransport->CloseSession(aCode, aReason);
+  Close();
+  return IPC_OK();
+}
+
+class BidiReceiveStream : public nsIWebTransportStreamCallback {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIWEBTRANSPORTSTREAMCALLBACK
+
+  BidiReceiveStream(
+      WebTransportParent::CreateBidirectionalStreamResolver&& aResolver,
+      std::function<
+          void(uint64_t, WebTransportParent::OnResetOrStopSendingCallback&&,
+               nsIWebTransportBidirectionalStream* aStream)>&& aStreamCallback,
+      Maybe<int64_t> aSendOrder, nsCOMPtr<nsISerialEventTarget>& aSocketThread)
+      : mResolver(aResolver),
+        mStreamCallback(std::move(aStreamCallback)),
+        mSendOrder(aSendOrder),
+        mSocketThread(aSocketThread) {}
+
+ private:
+  virtual ~BidiReceiveStream() = default;
+  WebTransportParent::CreateBidirectionalStreamResolver mResolver;
+  std::function<void(uint64_t,
+                     WebTransportParent::OnResetOrStopSendingCallback&&,
+                     nsIWebTransportBidirectionalStream* aStream)>
+      mStreamCallback;
+  Maybe<int64_t> mSendOrder;
+  nsCOMPtr<nsISerialEventTarget> mSocketThread;
+};
+
+class UniReceiveStream : public nsIWebTransportStreamCallback {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIWEBTRANSPORTSTREAMCALLBACK
+
+  UniReceiveStream(
+      WebTransportParent::CreateUnidirectionalStreamResolver&& aResolver,
+      std::function<void(uint64_t,
+                         WebTransportParent::OnResetOrStopSendingCallback&&,
+                         nsIWebTransportSendStream* aStream)>&& aStreamCallback,
+      Maybe<int64_t> aSendOrder, nsCOMPtr<nsISerialEventTarget>& aSocketThread)
+      : mResolver(aResolver),
+        mStreamCallback(std::move(aStreamCallback)),
+        mSendOrder(aSendOrder),
+        mSocketThread(aSocketThread) {}
+
+ private:
+  virtual ~UniReceiveStream() = default;
+  WebTransportParent::CreateUnidirectionalStreamResolver mResolver;
+  std::function<void(uint64_t,
+                     WebTransportParent::OnResetOrStopSendingCallback&&,
+                     nsIWebTransportSendStream* aStream)>
+      mStreamCallback;
+  Maybe<int64_t> mSendOrder;
+  nsCOMPtr<nsISerialEventTarget> mSocketThread;
+};
+
+NS_IMPL_ISUPPORTS(BidiReceiveStream, nsIWebTransportStreamCallback)
+NS_IMPL_ISUPPORTS(UniReceiveStream, nsIWebTransportStreamCallback)
+
+// nsIWebTransportStreamCallback:
+NS_IMETHODIMP BidiReceiveStream::OnBidirectionalStreamReady(
+    nsIWebTransportBidirectionalStream* aStream) {
+  LOG(("Bidirectional stream ready!"));
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+
+  aStream->SetSendOrder(mSendOrder);
+
+  RefPtr<mozilla::ipc::DataPipeSender> inputsender;
+  RefPtr<mozilla::ipc::DataPipeReceiver> inputreceiver;
+  nsresult rv =
+      NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                  getter_AddRefs(inputsender), getter_AddRefs(inputreceiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  uint64_t id;
+  Unused << aStream->GetStreamId(&id);
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  aStream->GetInputStream(getter_AddRefs(inputStream));
+  MOZ_ASSERT(inputStream);
+  nsCOMPtr<nsISupports> inputCopyContext;
+  rv = NS_AsyncCopy(inputStream, inputsender, mSocketThread,
+                    NS_ASYNCCOPY_VIA_WRITESEGMENTS,  // can we use READSEGMENTS?
+                    mozilla::ipc::kDefaultDataPipeCapacity, nullptr, nullptr,
+                    true, true, getter_AddRefs(inputCopyContext));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  RefPtr<mozilla::ipc::DataPipeSender> outputsender;
+  RefPtr<mozilla::ipc::DataPipeReceiver> outputreceiver;
+  rv =
+      NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                  getter_AddRefs(outputsender), getter_AddRefs(outputreceiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  nsCOMPtr<nsIAsyncOutputStream> outputStream;
+  aStream->GetOutputStream(getter_AddRefs(outputStream));
+  MOZ_ASSERT(outputStream);
+  nsCOMPtr<nsISupports> outputCopyContext;
+  rv = NS_AsyncCopy(outputreceiver, outputStream, mSocketThread,
+                    NS_ASYNCCOPY_VIA_READSEGMENTS,
+                    mozilla::ipc::kDefaultDataPipeCapacity, nullptr, nullptr,
+                    true, true, getter_AddRefs(outputCopyContext));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  LOG(("Returning BidirectionalStream pipe to content"));
+  mResolver(BidirectionalStream(id, inputreceiver, outputsender));
+
+  auto onResetOrStopSending =
+      [inputCopyContext(inputCopyContext), outputCopyContext(outputCopyContext),
+       inputsender(inputsender),
+       outputreceiver(outputreceiver)](nsresult aError) {
+        LOG(("onResetOrStopSending err=%x", static_cast<uint32_t>(aError)));
+        NS_CancelAsyncCopy(inputCopyContext, aError);
+        inputsender->CloseWithStatus(aError);
+        NS_CancelAsyncCopy(outputCopyContext, aError);
+        outputreceiver->CloseWithStatus(aError);
+      };
+
+  // Store onResetOrStopSending in WebTransportParent::mBidiStreamCallbackMap
+  // and onResetOrStopSending will be called when a stream receives STOP_SENDING
+  // or RESET.
+  mStreamCallback(id,
+                  WebTransportParent::OnResetOrStopSendingCallback(
+                      std::move(onResetOrStopSending)),
+                  aStream);
+  return NS_OK;
+}
+
+NS_IMETHODIMP UniReceiveStream::OnBidirectionalStreamReady(
+    nsIWebTransportBidirectionalStream* aStream) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+UniReceiveStream::OnUnidirectionalStreamReady(
+    nsIWebTransportSendStream* aStream) {
+  LOG(("Unidirectional stream ready!"));
+  // We should be on the Socket Thread
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+
+  aStream->SetSendOrder(mSendOrder);
+
+  RefPtr<::mozilla::ipc::DataPipeSender> sender;
+  RefPtr<::mozilla::ipc::DataPipeReceiver> receiver;
+  nsresult rv = NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                            getter_AddRefs(sender), getter_AddRefs(receiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  uint64_t id;
+  Unused << aStream->GetStreamId(&id);
+  nsCOMPtr<nsIAsyncOutputStream> outputStream;
+  aStream->GetOutputStream(getter_AddRefs(outputStream));
+  MOZ_ASSERT(outputStream);
+  nsCOMPtr<nsISupports> copyContext;
+  rv = NS_AsyncCopy(receiver, outputStream, mSocketThread,
+                    NS_ASYNCCOPY_VIA_READSEGMENTS,
+                    mozilla::ipc::kDefaultDataPipeCapacity, nullptr, nullptr,
+                    true, true, getter_AddRefs(copyContext));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mResolver(rv);
+    return rv;
+  }
+
+  LOG(("Returning UnidirectionalStream pipe to content"));
+  // pass the DataPipeSender to the content process
+  mResolver(UnidirectionalStream(id, sender));
+
+  auto onResetOrStopSending = [copyContext(copyContext),
+                               receiver(receiver)](nsresult aError) {
+    LOG(("onResetOrStopSending err=%x", static_cast<uint32_t>(aError)));
+    NS_CancelAsyncCopy(copyContext, aError);
+    receiver->CloseWithStatus(aError);
+  };
+
+  // Store onResetOrStopSending in WebTransportParent::mStreamCallbackMap and
+  // onResetOrStopSending will be called when a stream receives STOP_SENDING.
+  mStreamCallback(id,
+                  WebTransportParent::OnResetOrStopSendingCallback(
+                      std::move(onResetOrStopSending)),
+                  aStream);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BidiReceiveStream::OnUnidirectionalStreamReady(
+    nsIWebTransportSendStream* aStream) {
+  return NS_ERROR_FAILURE;
+}
+
+JS_HAZ_CAN_RUN_SCRIPT NS_IMETHODIMP UniReceiveStream::OnError(uint8_t aError) {
+  nsresult rv = aError == nsIWebTransport::INVALID_STATE_ERROR
+                    ? NS_ERROR_DOM_INVALID_STATE_ERR
+                    : NS_ERROR_FAILURE;
+  LOG(("CreateStream OnError: %u", aError));
+  mResolver(rv);
+  return NS_OK;
+}
+
+JS_HAZ_CAN_RUN_SCRIPT NS_IMETHODIMP BidiReceiveStream::OnError(uint8_t aError) {
+  nsresult rv = aError == nsIWebTransport::INVALID_STATE_ERROR
+                    ? NS_ERROR_DOM_INVALID_STATE_ERR
+                    : NS_ERROR_FAILURE;
+  LOG(("CreateStream OnError: %u", aError));
+  mResolver(rv);
+  return NS_OK;
+}
+
+IPCResult WebTransportParent::RecvSetSendOrder(uint64_t aStreamId,
+                                               Maybe<int64_t> aSendOrder) {
+  if (aSendOrder) {
+    LOG(("Set sendOrder=%" PRIi64 " for streamId %" PRIu64, aSendOrder.value(),
+         aStreamId));
+  } else {
+    LOG(("Set sendOrder=null for streamId %" PRIu64, aStreamId));
+  }
+  if (auto entry = mUniStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mStream->SetSendOrder(aSendOrder);
+  } else if (auto entry = mBidiStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mStream->SetSendOrder(aSendOrder);
+  }
+  return IPC_OK();
+}
+
+IPCResult WebTransportParent::RecvCreateUnidirectionalStream(
+    Maybe<int64_t> aSendOrder, CreateUnidirectionalStreamResolver&& aResolver) {
+  LOG(("%s for %p received, useSendOrder=%d, sendOrder=%" PRIi64, __func__,
+       this, aSendOrder.isSome(),
+       aSendOrder.isSome() ? aSendOrder.value() : 0));
+
+  auto streamCb =
+      [self = RefPtr{this}](
+          uint64_t aStreamId,
+          WebTransportParent::OnResetOrStopSendingCallback&& aCallback,
+          nsIWebTransportSendStream* aStream) {
+        self->mUniStreamCallbackMap.InsertOrUpdate(
+            aStreamId, StreamHash<nsIWebTransportSendStream>{
+                           std::move(aCallback), aStream});
+      };
+  RefPtr<UniReceiveStream> callback = new UniReceiveStream(
+      std::move(aResolver), std::move(streamCb), aSendOrder, mSocketThread);
+  nsresult rv;
+  rv = mWebTransport->CreateOutgoingUnidirectionalStream(callback);
+  if (NS_FAILED(rv)) {
+    callback->OnError(0);  // XXX
+  }
+  return IPC_OK();
+}
+
+IPCResult WebTransportParent::RecvCreateBidirectionalStream(
+    Maybe<int64_t> aSendOrder, CreateBidirectionalStreamResolver&& aResolver) {
+  LOG(("%s for %p received, useSendOrder=%d, sendOrder=%" PRIi64, __func__,
+       this, aSendOrder.isSome(),
+       aSendOrder.isSome() ? aSendOrder.value() : 0));
+
+  auto streamCb =
+      [self = RefPtr{this}](
+          uint64_t aStreamId,
+          WebTransportParent::OnResetOrStopSendingCallback&& aCallback,
+          nsIWebTransportBidirectionalStream* aStream) {
+        self->mBidiStreamCallbackMap.InsertOrUpdate(
+            aStreamId, StreamHash<nsIWebTransportBidirectionalStream>{
+                           std::move(aCallback), aStream});
+      };
+  RefPtr<BidiReceiveStream> callback = new BidiReceiveStream(
+      std::move(aResolver), std::move(streamCb), aSendOrder, mSocketThread);
+  nsresult rv;
+  rv = mWebTransport->CreateOutgoingBidirectionalStream(callback);
+  if (NS_FAILED(rv)) {
+    callback->OnError(0);  // XXX
+  }
+  return IPC_OK();
+}
+
+// We recieve this notification from the WebTransportSessionProxy if session was
+// successfully created at the end of
+// WebTransportSessionProxy::OnStopRequest
+NS_IMETHODIMP
+WebTransportParent::OnSessionReady(uint64_t aSessionId) {
+  MOZ_ASSERT(mOwningEventTarget);
+  MOZ_ASSERT(!mOwningEventTarget->IsOnCurrentThread());
+
+  LOG(("Created web transport session, sessionID = %" PRIu64 ", for %p",
+       aSessionId, this));
+
+  mSessionReady = true;
+
+  // Retarget to socket thread. After this, WebTransportParent and
+  // |mWebTransport| should be only accessed on the socket thread.
+  nsresult rv = mWebTransport->RetargetTo(mSocketThread);
+  if (NS_FAILED(rv)) {
+    mOwningEventTarget->Dispatch(NS_NewRunnableFunction(
+        "WebTransportParent::OnSessionReady Failed",
+        [self = RefPtr{this}, result = rv] {
+          MutexAutoLock lock(self->mMutex);
+          if (!self->mClosed && self->mResolver) {
+            self->mResolver(ResolveType(
+                result, static_cast<uint8_t>(
+                            WebTransportReliabilityMode::Supports_unreliable)));
+            self->mResolver = nullptr;
+          }
+        }));
+    return NS_OK;
+  }
+
+  mOwningEventTarget->Dispatch(NS_NewRunnableFunction(
+      "WebTransportParent::OnSessionReady", [self = RefPtr{this}] {
+        MutexAutoLock lock(self->mMutex);
+        if (!self->mClosed && self->mResolver) {
+          self->mResolver(ResolveType(
+              NS_OK, static_cast<uint8_t>(
+                         WebTransportReliabilityMode::Supports_unreliable)));
+          self->mResolver = nullptr;
+          if (self->mExecuteAfterResolverCallback) {
+            self->mExecuteAfterResolverCallback();
+            self->mExecuteAfterResolverCallback = nullptr;
+          }
+        } else {
+          if (self->mClosed) {
+            LOG(("Session already closed at OnSessionReady %p", self.get()));
+          } else {
+            LOG(("No resolver at OnSessionReady %p", self.get()));
+          }
+        }
+      }));
+
+  return NS_OK;
+}
+
+// We receive this notification from the WebTransportSessionProxy if session
+// creation was unsuccessful at the end of
+// WebTransportSessionProxy::OnStopRequest
+NS_IMETHODIMP
+WebTransportParent::OnSessionClosed(const bool aCleanly,
+                                    const uint32_t aErrorCode,
+                                    const nsACString& aReason) {
+  nsresult rv = NS_OK;
+
+  MOZ_ASSERT(mOwningEventTarget);
+  MOZ_ASSERT(!mOwningEventTarget->IsOnCurrentThread());
+
+  // currently we just know if session was closed gracefully or not.
+  // we need better error propagation from lower-levels of http3
+  // webtransport session and it's subsequent error mapping to DOM.
+  // XXX See Bug 1806834
+  if (!mSessionReady) {
+    // this is an unclean close (we never got to ready)
+    LOG(("webtransport %p session creation failed code= %u, reason= %s", this,
+         aErrorCode, PromiseFlatCString(aReason).get()));
+    // we know we haven't gone Ready yet
+    rv = NS_ERROR_FAILURE;
+    mOwningEventTarget->Dispatch(NS_NewRunnableFunction(
+        "WebTransportParent::OnSessionClosed",
+        [self = RefPtr{this}, result = rv] {
+          MutexAutoLock lock(self->mMutex);
+          if (!self->mClosed && self->mResolver) {
+            self->mResolver(ResolveType(
+                result, static_cast<uint8_t>(
+                            WebTransportReliabilityMode::Supports_unreliable)));
+            self->mResolver = nullptr;
+          }
+        }));
+  } else {
+    {
+      MutexAutoLock lock(mMutex);
+      if (mResolver) {
+        LOG(("[%p] NotifyRemoteClosed to be called later", this));
+        // NotifyRemoteClosed needs to wait until mResolver is invoked.
+        mExecuteAfterResolverCallback = [self = RefPtr{this}, aCleanly,
+                                         aErrorCode,
+                                         reason = nsCString{aReason}]() {
+          self->NotifyRemoteClosed(aCleanly, aErrorCode, reason);
+        };
+        return NS_OK;
+      }
+    }
+    // https://w3c.github.io/webtransport/#web-transport-termination
+    // Step 1: Let cleanly be a boolean representing whether the HTTP/3
+    // stream associated with the CONNECT request that initiated
+    // transport.[[Session]] is in the "Data Recvd" state. [QUIC]
+    // XXX not calculated yet
+    NotifyRemoteClosed(aCleanly, aErrorCode, aReason);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP WebTransportParent::OnStopSending(uint64_t aStreamId,
+                                                nsresult aError) {
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  LOG(("WebTransportParent::OnStopSending %p stream id=%" PRIx64, this,
+       aStreamId));
+  if (auto entry = mUniStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mCallback.OnResetOrStopSending(aError);
+    mUniStreamCallbackMap.Remove(aStreamId);
+  } else if (auto entry = mBidiStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mCallback.OnResetOrStopSending(aError);
+    mBidiStreamCallbackMap.Remove(aStreamId);
+  }
+  if (CanSend()) {
+    Unused << SendOnStreamResetOrStopSending(aStreamId,
+                                             StopSendingError(aError));
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP WebTransportParent::OnResetReceived(uint64_t aStreamId,
+                                                  nsresult aError) {
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  LOG(("WebTransportParent::OnResetReceived %p stream id=%" PRIx64, this,
+       aStreamId));
+  if (auto entry = mUniStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mCallback.OnResetOrStopSending(aError);
+    mUniStreamCallbackMap.Remove(aStreamId);
+  } else if (auto entry = mBidiStreamCallbackMap.Lookup(aStreamId)) {
+    entry->mCallback.OnResetOrStopSending(aError);
+    mBidiStreamCallbackMap.Remove(aStreamId);
+  }
+  if (CanSend()) {
+    Unused << SendOnStreamResetOrStopSending(aStreamId, ResetError(aError));
+  }
+  return NS_OK;
+}
+
+void WebTransportParent::NotifyRemoteClosed(bool aCleanly, uint32_t aErrorCode,
+                                            const nsACString& aReason) {
+  LOG(("webtransport %p session remote closed cleanly=%d code= %u, reason= %s",
+       this, aCleanly, aErrorCode, PromiseFlatCString(aReason).get()));
+  mSocketThread->Dispatch(NS_NewRunnableFunction(
+      __func__, [self = RefPtr{this}, aErrorCode, reason = nsCString{aReason},
+                 aCleanly]() {
+        // Tell the content side we were closed by the server
+        Unused << self->SendRemoteClosed(aCleanly, aErrorCode, reason);
+        // Let the other end shut down the IPC channel after RecvClose()
+      }));
+}
+
+// This method is currently not used by WebTransportSessionProxy to inform of
+// any session related events. All notification is recieved via
+// WebTransportSessionProxy::OnSessionReady and
+// WebTransportSessionProxy::OnSessionClosed methods
+NS_IMETHODIMP
+WebTransportParent::OnSessionReadyInternal(
+    mozilla::net::Http3WebTransportSession* aSession) {
+  Unused << aSession;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebTransportParent::OnIncomingStreamAvailableInternal(
+    mozilla::net::Http3WebTransportStream* aStream) {
+  // XXX implement once DOM WebAPI supports creation of streams
+  Unused << aStream;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebTransportParent::OnIncomingUnidirectionalStreamAvailable(
+    nsIWebTransportReceiveStream* aStream) {
+  // Note: we need to hold a reference to the stream if we want to get stats,
+  // etc
+  LOG(("%p IncomingUnidirectonalStream available", this));
+
+  // We must be on the Socket Thread
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+
+  RefPtr<DataPipeSender> sender;
+  RefPtr<DataPipeReceiver> receiver;
+  nsresult rv = NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                            getter_AddRefs(sender), getter_AddRefs(receiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  aStream->GetInputStream(getter_AddRefs(inputStream));
+  MOZ_ASSERT(inputStream);
+  rv = NS_AsyncCopy(inputStream, sender, mSocketThread,
+                    NS_ASYNCCOPY_VIA_WRITESEGMENTS,
+                    mozilla::ipc::kDefaultDataPipeCapacity);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  LOG(("%p Sending UnidirectionalStream pipe to content", this));
+  // pass the DataPipeReceiver to the content process
+  uint64_t id;
+  Unused << aStream->GetStreamId(&id);
+  Unused << SendIncomingUnidirectionalStream(id, receiver);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebTransportParent::OnIncomingBidirectionalStreamAvailable(
+    nsIWebTransportBidirectionalStream* aStream) {
+  // Note: we need to hold a reference to the stream if we want to get stats,
+  // etc
+  LOG(("%p IncomingBidirectonalStream available", this));
+
+  // We must be on the Socket Thread
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+
+  RefPtr<DataPipeSender> inputSender;
+  RefPtr<DataPipeReceiver> inputReceiver;
+  nsresult rv =
+      NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                  getter_AddRefs(inputSender), getter_AddRefs(inputReceiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  aStream->GetInputStream(getter_AddRefs(inputStream));
+  MOZ_ASSERT(inputStream);
+  rv = NS_AsyncCopy(inputStream, inputSender, mSocketThread,
+                    NS_ASYNCCOPY_VIA_WRITESEGMENTS,
+                    mozilla::ipc::kDefaultDataPipeCapacity);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  RefPtr<DataPipeSender> outputSender;
+  RefPtr<DataPipeReceiver> outputReceiver;
+  rv =
+      NewDataPipe(mozilla::ipc::kDefaultDataPipeCapacity,
+                  getter_AddRefs(outputSender), getter_AddRefs(outputReceiver));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIAsyncOutputStream> outputStream;
+  aStream->GetOutputStream(getter_AddRefs(outputStream));
+  MOZ_ASSERT(outputStream);
+  rv = NS_AsyncCopy(outputReceiver, outputStream, mSocketThread,
+                    NS_ASYNCCOPY_VIA_READSEGMENTS,
+                    mozilla::ipc::kDefaultDataPipeCapacity);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  LOG(("%p Sending BidirectionalStream pipe to content", this));
+  // pass the DataPipeSender to the content process
+  uint64_t id;
+  Unused << aStream->GetStreamId(&id);
+  Unused << SendIncomingBidirectionalStream(id, inputReceiver, outputSender);
+  return NS_OK;
+}
+
+::mozilla::ipc::IPCResult WebTransportParent::RecvGetMaxDatagramSize(
+    GetMaxDatagramSizeResolver&& aResolver) {
+  LOG(("WebTransportParent RecvGetMaxDatagramSize"));
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  MOZ_ASSERT(mWebTransport);
+  MOZ_ASSERT(!mMaxDatagramSizeResolver);
+
+  mMaxDatagramSizeResolver = std::move(aResolver);
+  // maximum datagram size for the session is returned from network stack
+  // synchronously via WebTransportSessionEventListener::OnMaxDatagramSize
+  // interface
+  mWebTransport->GetMaxDatagramSize();
+  return IPC_OK();
+}
+
+// The promise sent in this request will be resolved
+// in OnOutgoingDatagramOutCome which is called synchronously from
+// WebTransportSessionProxy::SendDatagram
+::mozilla::ipc::IPCResult WebTransportParent::RecvOutgoingDatagram(
+    nsTArray<uint8_t>&& aData, const TimeStamp& aExpirationTime,
+    OutgoingDatagramResolver&& aResolver) {
+  LOG(("WebTransportParent sending datagram"));
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  MOZ_ASSERT(mWebTransport);
+
+  Unused << aExpirationTime;
+
+  MOZ_ASSERT(!mOutgoingDatagramResolver);
+  mOutgoingDatagramResolver = std::move(aResolver);
+  // XXX we need to forward the timestamps to the necko stack
+  // timestamp should be checked in the necko for expiry
+  // See Bug 1818300
+  // currently this calls OnOutgoingDatagramOutCome synchronously
+  // Neqo won't call us back if the id == 0!
+  // We don't use the ID for anything currently; rework of the stack
+  // to implement proper HighWatermark buffering will require
+  // changes here anyways.
+  static uint64_t sDatagramId = 1;
+  LOG_VERBOSE(("Sending datagram %" PRIu64 ", length %zu", sDatagramId,
+               aData.Length()));
+  Unused << mWebTransport->SendDatagram(aData, sDatagramId++);
+
+  return IPC_OK();
+}
+
+NS_IMETHODIMP WebTransportParent::OnDatagramReceived(
+    const nsTArray<uint8_t>& aData) {
+  // We must be on the Socket Thread
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+
+  LOG(("WebTransportParent received datagram length = %zu", aData.Length()));
+
+  TimeStamp ts = TimeStamp::Now();
+  Unused << SendIncomingDatagram(aData, ts);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP WebTransportParent::OnDatagramReceivedInternal(
+    nsTArray<uint8_t>&& aData) {
+  // this method is used only for internal notificaiton within necko
+  // we dont expect to receive any notification with on this interface
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WebTransportParent::OnOutgoingDatagramOutCome(
+    uint64_t aId, WebTransportSessionEventListener::DatagramOutcome aOutCome) {
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  // XXX - do we need better error mappings for failures?
+  nsresult result = NS_ERROR_FAILURE;
+  Unused << result;
+  Unused << aId;
+
+  if (aOutCome == WebTransportSessionEventListener::DatagramOutcome::SENT) {
+    result = NS_OK;
+    LOG(("Sent datagram id= %" PRIu64, aId));
+  } else {
+    LOG(("Didn't send datagram id= %" PRIu64, aId));
+  }
+
+  // This assumes the stack is calling us back synchronously!
+  MOZ_ASSERT(mOutgoingDatagramResolver);
+  mOutgoingDatagramResolver(result);
+  mOutgoingDatagramResolver = nullptr;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP WebTransportParent::OnMaxDatagramSize(uint64_t aSize) {
+  LOG(("Max datagram size is %" PRIu64, aSize));
+  MOZ_ASSERT(mSocketThread->IsOnCurrentThread());
+  MOZ_ASSERT(mMaxDatagramSizeResolver);
+  mMaxDatagramSizeResolver(aSize);
+  mMaxDatagramSizeResolver = nullptr;
+  return NS_OK;
+}
+}  // namespace mozilla::dom
diff --git a/dom/webtransport/parent/WebTransportParent.h b/dom/webtransport/parent/WebTransportParent.h
new file mode 100644
index 0000000000..8b1b1a6867
--- /dev/null
+++ b/dom/webtransport/parent/WebTransportParent.h
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_WEBTRANSPORT_PARENT_WEBTRANSPORTPARENT_H_
+#define DOM_WEBTRANSPORT_PARENT_WEBTRANSPORTPARENT_H_
+
+#include "ErrorList.h"
+#include "mozilla/dom/ClientIPCTypes.h"
+#include "mozilla/dom/FlippedOnce.h"
+#include "mozilla/dom/PWebTransportParent.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/PBackgroundSharedTypes.h"
+#include "nsISupports.h"
+#include "nsIPrincipal.h"
+#include "nsIWebTransport.h"
+#include "nsIWebTransportStream.h"
+#include "nsTHashMap.h"
+
+namespace mozilla::dom {
+
+enum class WebTransportReliabilityMode : uint8_t;
+
+class WebTransportParent : public PWebTransportParent,
+                           public WebTransportSessionEventListener {
+  using IPCResult = mozilla::ipc::IPCResult;
+
+ public:
+  WebTransportParent() = default;
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_WEBTRANSPORTSESSIONEVENTLISTENER
+
+  void Create(const nsAString& aURL, nsIPrincipal* aPrincipal,
+              const mozilla::Maybe<IPCClientInfo>& aClientInfo,
+              const bool& aDedicated, const bool& aRequireUnreliable,
+              const uint32_t& aCongestionControl,
+              nsTArray<WebTransportHash>&& aServerCertHashes,
+              Endpoint<PWebTransportParent>&& aParentEndpoint,
+              std::function<void(std::tuple<const nsresult&, const uint8_t&>)>&&
+                  aResolver);
+
+  IPCResult RecvClose(const uint32_t& aCode, const nsACString& aReason);
+
+  IPCResult RecvSetSendOrder(uint64_t aStreamId, Maybe<int64_t> aSendOrder);
+
+  IPCResult RecvCreateUnidirectionalStream(
+      Maybe<int64_t> aSendOrder,
+      CreateUnidirectionalStreamResolver&& aResolver);
+  IPCResult RecvCreateBidirectionalStream(
+      Maybe<int64_t> aSendOrder, CreateBidirectionalStreamResolver&& aResolver);
+
+  ::mozilla::ipc::IPCResult RecvOutgoingDatagram(
+      nsTArray<uint8_t>&& aData, const TimeStamp& aExpirationTime,
+      OutgoingDatagramResolver&& aResolver);
+
+  ::mozilla::ipc::IPCResult RecvGetMaxDatagramSize(
+      GetMaxDatagramSizeResolver&& aResolver);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  class OnResetOrStopSendingCallback final {
+   public:
+    explicit OnResetOrStopSendingCallback(
+        std::function<void(nsresult)>&& aCallback)
+        : mCallback(std::move(aCallback)) {}
+    ~OnResetOrStopSendingCallback() = default;
+
+    void OnResetOrStopSending(nsresult aError) { mCallback(aError); }
+
+   private:
+    std::function<void(nsresult)> mCallback;
+  };
+
+ protected:
+  virtual ~WebTransportParent();
+
+ private:
+  void NotifyRemoteClosed(bool aCleanly, uint32_t aErrorCode,
+                          const nsACString& aReason);
+
+  using ResolveType = std::tuple<const nsresult&, const uint8_t&>;
+  nsCOMPtr<nsISerialEventTarget> mSocketThread;
+  Atomic<bool> mSessionReady{false};
+
+  mozilla::Mutex mMutex{"WebTransportParent::mMutex"};
+  std::function<void(ResolveType)> mResolver MOZ_GUARDED_BY(mMutex);
+  // This is needed because mResolver is resolved on the background thread and
+  // OnSessionClosed is called on the socket thread.
+  std::function<void()> mExecuteAfterResolverCallback MOZ_GUARDED_BY(mMutex);
+  OutgoingDatagramResolver mOutgoingDatagramResolver;
+  GetMaxDatagramSizeResolver mMaxDatagramSizeResolver;
+  FlippedOnce<false> mClosed MOZ_GUARDED_BY(mMutex);
+
+  nsCOMPtr<nsIWebTransport> mWebTransport;
+  nsCOMPtr<nsIEventTarget> mOwningEventTarget;
+
+  // What we need to be able to lookup by streamId
+  template <typename T>
+  struct StreamHash {
+    OnResetOrStopSendingCallback mCallback;
+    nsCOMPtr<T> mStream;
+  };
+  nsTHashMap<nsUint64HashKey, StreamHash<nsIWebTransportBidirectionalStream>>
+      mBidiStreamCallbackMap;
+  nsTHashMap<nsUint64HashKey, StreamHash<nsIWebTransportSendStream>>
+      mUniStreamCallbackMap;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // DOM_WEBTRANSPORT_PARENT_WEBTRANSPORTPARENT_H_
diff --git a/dom/webtransport/parent/moz.build b/dom/webtransport/parent/moz.build
new file mode 100644
index 0000000000..f3486cc8c7
--- /dev/null
+++ b/dom/webtransport/parent/moz.build
@@ -0,0 +1,22 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.dom += [
+    "WebTransportParent.h",
+]
+
+UNIFIED_SOURCES += [
+    "WebTransportParent.cpp",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+LOCAL_INCLUDES += [
+    "/netwerk/base",
+    "/netwerk/protocol/http",
+]