quic: fix readable stream truncation on stop-sending, abort & timeout

lib/internal/blob.js

@@ -575,7 +575,12 @@ function createBlobReaderStream(reader) {
 const kMaxBatchChunks = 16;
 
 async function* createBlobReaderIterable(reader, options = kEmptyObject) {
-  const { getReadError } = options;
+  // getEndError(status) lets the caller map a read ending to an error, or null.
+  // It is consulted both on a read failure (status < 0, always an error - we
+  // fall back to a generic one if the caller returns null) and on a clean EOS
+  // (status 0, an error only if the caller returns one, e.g. a stream that
+  // ended before its FIN).
+  const { getEndError } = options;
   let wakeup = PromiseWithResolvers();
   reader.setWakeup(wakeup.resolve);
 
@@ -601,8 +606,8 @@ async function* createBlobReaderIterable(reader, options = kEmptyObject) {
           break;
         }
         if (pullResult.status < 0) {
-          error = typeof getReadError === 'function' ?
-            getReadError(pullResult.status) :
+          error = (typeof getEndError === 'function' &&
+                   getEndError(pullResult.status)) ||
             new ERR_INVALID_STATE('The reader is not readable');
           break;
         }
@@ -618,7 +623,11 @@ async function* createBlobReaderIterable(reader, options = kEmptyObject) {
         yield batch;
       }
 
-      if (eos) return;
+      if (eos) {
+        const eosError = typeof getEndError === 'function' ? getEndError(0) : null;
+        if (eosError) throw eosError;
+        return;
+      }
       if (error) throw error;
 
       if (blocked) {

lib/internal/quic/quic.js

@@ -1647,30 +1647,35 @@ class QuicStream {
     // Non-readable stream (outbound-only unidirectional, or closed)
     if (!inner.reader) return;
 
-    yield* createBlobReaderIterable(inner.reader, {
-      getReadError: () => {
-        // The read side ends for one of three reasons:
-        //   * Clean FIN received from the peer (state.finReceived
-        //     === true). The iterator stops without calling this;
-        //     fall through to the generic state error if it does.
-        //   * Peer sent us a RESET_STREAM. The C++ side records the
-        //     code in state.resetCode regardless of whether the JS
-        //     onreset handler was attached. state.finReceived stays
-        //     false because no FIN was seen.
-        //   * We aborted locally via stream.resetStream() or
-        //     stream.stopSending(). Both paths run EndReadable in
-        //     C++, setting state.readEnded without setting
-        //     state.finReceived. There is no peer code to surface.
-        if (inner.state.readEnded && !inner.state.finReceived) {
-          const peerResetCode = inner.state.resetCode;
-          if (peerResetCode !== undefined && peerResetCode > 0n) {
-            return new ERR_QUIC_STREAM_RESET(Number(peerResetCode));
-          }
-          return new ERR_QUIC_STREAM_ABORTED(
-            'Stream aborted before FIN was received');
+    // Maps the read side's end state to the error to surface, or null if it
+    // ended cleanly. state.finReceived is set only when the peer explicitly
+    // sent a FIN, confirming we got the whole stream - the one and only clean
+    // ending. Returns null in that case. Without a FIN the read side is
+    // truncated, for one of these reasons:
+    //   * Peer sent us a RESET_STREAM. The C++ side records the
+    //     code in state.resetCode regardless of whether the JS
+    //     onreset handler was attached. state.finReceived stays
+    //     false because no FIN was seen.
+    //   * We aborted locally via stream.stopSending(). This runs EndReadable
+    //     in C++, setting state.readEnded but not state.finReceived. There
+    //     is no peer code to surface.
+    //   * The session was torn down before a FIN arrived (a local or peer
+    //     connection close, an idle timeout, or any error), again leaving
+    //     state.finReceived false.
+    const readTruncationError = () => {
+      if (inner.state.readEnded && !inner.state.finReceived) {
+        const peerResetCode = inner.state.resetCode;
+        if (peerResetCode !== undefined && peerResetCode > 0n) {
+          return new ERR_QUIC_STREAM_RESET(Number(peerResetCode));
         }
-        return new ERR_INVALID_STATE('The stream is not readable');
-      },
+        return new ERR_QUIC_STREAM_ABORTED(
+          'Stream aborted before FIN was received');
+      }
+      return null;
+    };
+
+    yield* createBlobReaderIterable(inner.reader, {
+      getEndError: readTruncationError,
     });
   }
 

src/quic/streams.cc

@@ -1403,13 +1403,6 @@ BaseObjectPtr<Blob::Reader> Stream::get_reader() {
   return reader;
 }
 
-void Stream::set_final_size(uint64_t final_size) {
-  DCHECK_IMPLIES(state()->fin_received == 1,
-                 final_size <= STAT_GET(Stats, final_size));
-  state()->fin_received = 1;
-  STAT_SET(Stats, final_size, final_size);
-}
-
 void Stream::set_outbound(std::shared_ptr<DataQueue> source) {
   if (!source || !is_writable()) return;
   Debug(this, "Setting the outbound data source");
@@ -1605,13 +1598,20 @@ void Stream::EndWritable() {
   state()->write_ended = 1;
 }
 
-void Stream::EndReadable(std::optional<uint64_t> maybe_final_size) {
+void Stream::EndReadable(std::optional<uint64_t> maybe_final_size,
+                         bool clean_fin) {
   if (!is_readable()) return;
   state()->read_ended = 1;
+  // fin_received marks a clean completion of the read side (a real FIN). Any
+  // unclean end (reset/abort/session teardown) truncates the stream, which
+  // the JS reader will expose as a read error later.
+  if (clean_fin) state()->fin_received = 1;
   // Flush any accumulated data before capping so the reader can see it.
   FlushAccumulation();
-  set_final_size(maybe_final_size.value_or(STAT_GET(Stats, bytes_received)));
-  inbound_->cap(STAT_GET(Stats, final_size));
+  const uint64_t final_size =
+      maybe_final_size.value_or(STAT_GET(Stats, bytes_received));
+  STAT_SET(Stats, final_size, final_size);
+  inbound_->cap(final_size);
   // Notify the JS reader so it can see EOS. Pass fin=true so the
   // wakeup promise resolves with a value the iterator can check to
   // avoid waiting for another wakeup that will never come.
@@ -1640,8 +1640,9 @@ void Stream::Destroy(QuicError error) {
   // End the writable before marking as destroyed.
   EndWritable();
 
-  // Also end the readable side if it isn't already.
-  EndReadable();
+  // Also end the readable side if it isn't already. If not already ended,
+  // this will eventually surface as a error, since the data is truncated.
+  EndReadable(std::nullopt, /* clean_fin = */ false);
 
   // We are going to release our reference to the outbound_ queue here.
   outbound_.reset();
@@ -1688,7 +1689,7 @@ void Stream::ReceiveData(const uint8_t* data,
   // end the readable side if this is the last bit of data we've received.
   Debug(this, "Receiving %zu bytes of data", len);
   if (state()->read_ended == 1 || len == 0) {
-    if (flags.fin) EndReadable();
+    if (flags.fin) EndReadable(std::nullopt, /* clean_fin = */ true);
     return;
   }
 
@@ -1761,7 +1762,7 @@ void Stream::ReceiveData(const uint8_t* data,
 
   if (flags.fin) {
     FlushAccumulation();
-    EndReadable();
+    EndReadable(std::nullopt, /* clean_fin = */ true);
   } else if (reader_ && was_empty) {
     // Notify the reader once when the accumulator transitions from empty
     // to non-empty. This wakes the reader exactly once per accumulation
@@ -1800,7 +1801,7 @@ void Stream::ReceiveStreamReset(uint64_t final_size, QuicError error) {
         final_size,
         error);
   state()->reset_code = error.code();
-  EndReadable(final_size);
+  EndReadable(final_size, /* clean_fin = */ false);
   EmitReset(error);
 }
 
@@ -1823,7 +1824,7 @@ void Stream::DoStreamReset(error_code code) {
 }
 
 void Stream::SendStopSending(error_code code) {
-  EndReadable();
+  EndReadable(std::nullopt, /* clean_fin = */ false);
 
   if (!is_pending()) {
     // If the stream is a local unidirectional there's nothing to do here.

src/quic/streams.h

@@ -309,7 +309,10 @@ class Stream final : public AsyncWrap,
   void Commit(size_t datalen, bool fin = false);
 
   void EndWritable();
-  void EndReadable(std::optional<uint64_t> maybe_final_size = std::nullopt);
+  // clean_fin indicates the read side is ending because a real FIN frame was
+  // received from the peer (as opposed to a reset, a local abort, or the
+  // session being torn down). Anything else => truncated read.
+  void EndReadable(std::optional<uint64_t> maybe_final_size, bool clean_fin);
   void EntryRead(size_t amount) override;
   void BeforePull() override;
 
@@ -398,7 +401,6 @@ class Stream final : public AsyncWrap,
   // Gets a reader for the data received for this stream from the peer,
   BaseObjectPtr<Blob::Reader> get_reader();
 
-  void set_final_size(uint64_t amount);
   void set_outbound(std::shared_ptr<DataQueue> source);
 
   // Streaming outbound support

test/parallel/test-quic-stream-iteration-reset.mjs

@@ -1,66 +1,55 @@
 // Flags: --experimental-quic --experimental-stream-iter --no-warnings
 
-// Test: peer RESET_STREAM causes iterator to error.
-// When the server resets the stream, the client's async iterator
-// should throw or return early.
+// Test: a peer RESET_STREAM truncates the readable. The async iterator
+// delivers the data received before the reset, then throws
+// ERR_QUIC_STREAM_RESET (carrying the peer's code) at the end - rather than
+// ending cleanly.
 
 import { hasQuic, skip, mustCall } from '../common/index.mjs';
-import * as assert from 'node:assert';
+import { setTimeout as delay } from 'node:timers/promises';
+import assert from 'node:assert';
 
-const { ok, rejects } = assert;
+const { strictEqual } = assert;
 
 if (!hasQuic) {
   skip('QUIC is not enabled');
 }
 
 const { listen, connect } = await import('../common/quic.mjs');
 
-const encoder = new TextEncoder();
-
-const serverReady = Promise.withResolvers();
-
 const serverEndpoint = await listen(mustCall((serverSession) => {
   serverSession.onstream = mustCall(async (stream) => {
-    // Reset the stream from the server side.
+    stream.writer.write(new Uint8Array(1000).fill(7));
+    while (stream.stats.maxOffsetAcknowledged < 1000n) await delay(5);
     stream.resetStream(42n);
-    await rejects(stream.closed, mustCall((err) => {
-      assert.ok(err);
-      return true;
-    }));
-    serverReady.resolve();
-    await serverSession.closed;
+    stream.closed.catch(() => {});
   });
-}), { transportParams: { maxIdleTimeout: 1 } });
+}));
 
 const clientSession = await connect(serverEndpoint.address, {
   transportParams: { maxIdleTimeout: 1 },
 });
 await clientSession.opened;
 
-const stream = await clientSession.createBidirectionalStream({
-  body: encoder.encode('will be reset by server'),
-});
-
-// Set up the closed handler before the reset to avoid unhandled rejection.
-const closedPromise = rejects(stream.closed, mustCall((err) => {
-  assert.ok(err);
-  return true;
-}));
-
-await serverReady.promise;
+// Keep our write side open so the stream stays alive while we read.
+const stream = await clientSession.createBidirectionalStream();
+await stream.writer.write(new Uint8Array([1]));
+stream.closed.catch(() => {});
 
-// The async iterator should either throw or return early when the
-// peer resets the readable side.
+let received = 0;
+let threw;
 try {
-  for await (const batch of stream) {
-    // May receive some data before the reset arrives.
-    ok(Array.isArray(batch));
+  for await (const chunk of stream) {
+    for (const c of chunk) received += c.byteLength;
   }
-} catch {
-  // The iterator may throw when the reset arrives mid-iteration.
+} catch (err) {
+  threw = err;
 }
 
-// Either way, the stream should close.
-await closedPromise;
-await clientSession.closed;
+// The buffered data was delivered before the error.
+strictEqual(received, 1000);
+// The reset surfaced as a reset error (with its code), not a clean end.
+strictEqual(threw?.code, 'ERR_QUIC_STREAM_RESET');
+
+clientSession.close();
 await serverEndpoint.close();

test/parallel/test-quic-stream-iteration-truncated.mjs

@@ -0,0 +1,58 @@
+// Flags: --experimental-quic --experimental-stream-iter --no-warnings
+
+// Test: a readable stream truncated by the connection idle timeout delivers
+// the data it received, then surfaces the truncation as an error at the end of
+// iteration - rather than a silent clean end-of-stream that would make an
+// incomplete stream look complete.
+
+import { hasQuic, skip, mustCall } from '../common/index.mjs';
+import assert from 'node:assert';
+
+const { strictEqual } = assert;
+
+if (!hasQuic) {
+  skip('QUIC is not enabled');
+}
+
+const { listen, connect } = await import('../common/quic.mjs');
+
+// The body sends 1000 bytes then hangs (never a FIN), so the only thing that
+// ends the client's read side is the connection idle timeout.
+async function* stallingBody() {
+  yield new Uint8Array(1000).fill(7);
+  await new Promise(() => {});
+}
+
+const serverEndpoint = await listen(mustCall((serverSession) => {
+  serverSession.onstream = mustCall((stream) => {
+    stream.setBody(stallingBody());
+    stream.closed.catch(() => {});
+  });
+}));
+
+const clientSession = await connect(serverEndpoint.address, {
+  // Short connection idle timeout so the truncation happens quickly.
+  transportParams: { maxIdleTimeout: 1 },
+});
+await clientSession.opened;
+
+const stream = await clientSession.createBidirectionalStream();
+await stream.writer.write(new Uint8Array([1]));
+stream.closed.catch(() => {});
+
+let received = 0;
+let threw;
+try {
+  for await (const chunk of stream) {
+    for (const c of chunk) received += c.byteLength;
+  }
+} catch (err) {
+  threw = err;
+}
+
+// All the buffered data was delivered before the error.
+strictEqual(received, 1000);
+// The truncation surfaced as an error at the end, not a clean end-of-stream.
+strictEqual(threw?.code, 'ERR_QUIC_STREAM_ABORTED');
+
+await serverEndpoint.close();

test/parallel/test-quic-stream-setbody-errors.mjs

@@ -55,7 +55,13 @@ await clientSession.opened;
     message: /writer already accessed/,
   });
 
-  for await (const _ of stream) { /* drain */ } // eslint-disable-line no-unused-vars
+  // The server handles only the first stream and then closes its session, so
+  // this stream is never answered and never receives a FIN. Reading it
+  // therefore surfaces the truncation rather than ending cleanly.
+  await assert.rejects((async () => {
+    // eslint-disable-next-line no-unused-vars
+    for await (const _ of stream) { /* drain */ }
+  })(), { code: 'ERR_QUIC_STREAM_ABORTED' });
   await stream.closed;
 }