fix(endpoint): route shared-socket QUIC packets by destination CID

[richard-ramos]

Summary

This PR makes QUIC endpoints that share a UDP socket route received packets by destination connection ID before handing them to an lsquic engine. Known CIDs are tracked from lsquic callbacks and connection creation, while unknown Initial packets are routed to the server context so new inbound connections can still be accepted.

It also defines lsquic_cid_t in the prelude and excludes it from Futhark generation to avoid the invalid generated aligned layout.

[Copilot]

Pull request overview

This PR updates packet routing for endpoints that share a single UDP socket between client and server lsquic engines, by extracting the destination Connection ID (DCID) from incoming QUIC packets and forwarding each packet to the owning engine when possible. This addresses cross-dial scenarios where both endpoints are simultaneously dialing and accepting on the same underlying listener socket.

Changes:

• Added CID tracking to QuicContext and wired lsquic CID lifecycle callbacks (new/live/old SCIDs) to maintain an owned-CID set per engine.
• Implemented DCID extraction in QuicEndpoint.receiveDatagram and routed datagrams to the client/server context that owns the destination CID (fallback: deliver to both for unknown CIDs/handshakes).
• Added a cross-dial regression test covering concurrent bidirectional dialing between two endpoints.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_connection.nim	Adds a new cross-dial test to reproduce/guard shared-socket routing issues.
lsquic/endpoint.nim	Parses packet DCID and routes datagrams to the owning context instead of always delivering to both.
lsquic/context/context.nim	Introduces CID keying/tracking, plus lsquic CID update callbacks and helpers (ownsCid, trackConnectionCid).
lsquic/context/client.nim	Initializes CID tracking, registers CID update callbacks, and tracks the initial connection CID on dial.
lsquic/context/server.nim	Initializes CID tracking, registers CID update callbacks, and tracks the initial connection CID on accept.
lsquic/context/io.nim	Adds trace logging around packet input/output and send failures for debugging routing/IO behavior.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.