implement RPC support for inbound UDP connect() event

[ThomasRubini]

This implements RPC support for the new UDP connect custom event, so that we can call it from edgeworker.

Please note that EVENT_TYPE's value may change after approval depending on the feedback I'll get on the internal PR.

[ask-bonk]

UdpConnectCustomEvent::sendRpc() now calls EventDispatcher.udpConnect(), but Server::WorkerdBootstrapImpl::EventDispatcherImpl never overrides that method. The generated default rejects the request, so an edgeworker cannot deliver the UDP flow. Add the endpoint near jsRpcSession() and retain the worker while receiveRpc() awaits the handler:

    kj::Promise<void> udpConnect(UdpConnectContext context) override {
      auto worker = getWorker();
      auto& workerRef = *worker;
      return api::UdpConnectCustomEvent::receiveRpc(context, workerRef).attach(kj::mv(worker));
    }

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

PR #7433 adds bidirectional Cap'n Proto RPC transport for inbound UDP connect() events.

1. P1: The server dispatcher never implements udpConnect, so remote calls are rejected by the generated default handler. Posted a suggested fix: implement RPC support for inbound UDP connect() event #7433 (comment)

Limerick incoming!
A UDP flow sought its way,
But dispatch never joined the relay.
With a handler in line,
The packets align,
And the endpoint can answer all day.

github run

[codecov-commenter]

Codecov Report

❌ Patch coverage is 72.51462% with 47 lines in your changes missing coverage. Please review.
✅ Project coverage is 38.04%. Comparing base (b93fa71) to head (18de5f2).

Files with missing lines	Patch %	Lines
src/workerd/api/sockets.c++	63.49%	35 Missing and 11 partials ⚠️
src/workerd/server/server-test.c++	97.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7433      +/-   ##
==========================================
+ Coverage   37.96%   38.04%   +0.07%     
==========================================
  Files         836      836              
  Lines      257859   258027     +168     
  Branches    20397    20414      +17     
==========================================
+ Hits        97908    98157     +249     
+ Misses     148370   148258     -112     
- Partials    11581    11612      +31     

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[ask-bonk]

LGTM

github run