fix(download): disable uTP to prevent ENOBUFS socket exhaustion crashes - #21
Merged
Conversation
WebTorrent's uTP transport uses utp-native, which allocates an independent UDP socket for every outgoing peer connection attempt. Under heavy swarm discovery and peer reconnection churn, Windows rapidly exhausts socket buffer space and dynamic ports (WSAENOBUFS / ENOBUFS: 'no buffer space available').
Furthermore, when binding fails with ENOBUFS, utp-native's UTP.connect emits an 'error' event on an orphaned EventEmitter that has no error listener registered, triggering an unhandled exception that crashes the entire application.
Disabling uTP via { utp: false } instructs WebTorrent to connect to peers exclusively via standard TCP. TCP connections are universally supported by all BitTorrent clients, fully error-handled, pooled, and do not exhaust ephemeral UDP socket buffers.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
What and why
WebTorrent's uTP implementation relies on the native \utp-native\ dependency. In \utp-native, each outgoing peer connection attempts to bind a new, independent UDP socket on an ephemeral port (
ew UTP()\ -> \uv_udp_bind(0, '0.0.0.0')) rather than multiplexing traffic over a single shared UDP socket.
Under active swarm discovery and peer reconnection churn, rapidly opening dozens to hundreds of UDP sockets exhausts the OS socket buffer space and dynamic port pool—especially on Windows, which triggers Winsock error 10055 (\WSAENOBUFS\ / \code: 'ENOBUFS', 'no buffer space available').
Furthermore, when \�inding.utp_napi_bind\ throws \ENOBUFS, \utp-native\ schedules \process.nextTick(emitError, this, err)\ on the underlying \UTP\ socket instance. Because \UTP.connect\ only returns the connection stream (\conn) without attaching an error handler to the orphaned \UTP\ socket instance, this error is emitted with 0 listeners, escalating into an unhandled \uncaughtException\ that instantly terminates the process.
This fix passes \utp: false\ to the \WebTorrent\ constructor options in \ensureClient(), forcing peer traffic over standard TCP. Standard BitTorrent TCP (BEP 3) is supported by 100% of BitTorrent clients, fully error-handled, pooled, and immune to ephemeral UDP socket buffer exhaustion.
Checklist
pm run typecheck\ is clean
pm test\ passes (586 tests across 67 test files)