Repository navigation
fix(network-stack): drop guest-closed sessions once our FIN is acked - #157
Open
TadahiroYamamura wants to merge 2 commits into
Open
TadahiroYamamura wants to merge 2 commits into
TadahiroYamamura wants to merge 2 commits into
Conversation
When the guest sent its FIN first, the session stayed in natTable even after the guest acked our FIN, and a later SYN on the same 4-tuple was ignored. Track receiving the guest's FIN and sending our own separately from `state`, which gets overwritten, and drop the session once both are set and our FIN is acked. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This was referenced Oct 6, 2026
…FIN is acked When the guest's FIN arrived in FIN_WAIT, the session was dropped even if our FIN was still unacked (CLOSING in RFC 9293), so a retransmitted FIN or the final ACK hit no session. Drop it right away only when our FIN is already acked; otherwise leave it to the ACK handling added in the previous commit. Combined with earendil-works#159, every guest-initiated close of a connection without an upstream takes this path. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This branch has not been deployed
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
A2 of #155.
Problem
When the guest sends its FIN first, the connection is not removed from natTable even after Gondolin's FIN is ACKed. When the guest reconnects on the same 4-tuple, the new SYN hits the leftover session and is ignored, and
connect()hangs for 132–134s and fails (reproduced withcurl --local-port).Fix
Record "received the guest's FIN" and "sent our FIN" on the session, separately from
state, which gets overwritten. Once both are set and our FIN is ACKed (vmAck === mySeq), remove the session.Tests
Please check
statestrings and added two flags. Replacingstatewith flags would be cleaner, but we avoided it because the diff would get larger. B2 in the issue can probably be fixed with the same flagsonTcpCloseis not called when the session is removed. At that point the host socket is closed in both directions, andnet.tscleans up its own bookkeeping on the socket's close. This matches the existing "remove when the guest's FIN arrives inFIN_WAIT" pathnetwork-stack.ts). If both are merged, the correct order is "advancemyAck→guestFinReceived = true→onTcpClose"Suggested CHANGELOG entry
Fix TCP sessions the guest closed first never being removed, which made a later connection on the same 4-tuple hang until its SYN retries ran out.
🤖 AI (Claude Code) was used for the investigation and for writing the code.
Contribution Agreement
Please ensure this PR follows the guidelines in
CONTRIBUTING.md.By submitting this pull request, I confirm the following:
I understand that the entity Earendil Inc. (incorporated in the state of Delaware in 2025) needs some rights from me in order to utilize my contributions in this PR. As a contributor I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Earendil Inc. can use, modify, copy, and redistribute my contributions, under Earendil Inc.'s choice of terms.