[sairex53]

When the parent TCP listener hits EMFILE or ENFILE, the current accept loop closes newConns, causing the port-forwarding worker to exit. The listener then stops forwarding connections permanently even after descriptors become available.

Retry these descriptor-exhaustion errors with capped exponential backoff, reset the delay after a successful accept, and make the wait interruptible during shutdown. Other accept errors retain the existing behavior.

Add tests for recovery after EMFILE and ENFILE, prompt shutdown during the retry delay, and termination on a non-retryable accept error.

Fixes #536.

Testing:

• go test ./pkg/port/builtin/parent/tcp -count=1
• go test -race ./pkg/port/builtin/parent/tcp -count=1
• go vet ./pkg/port/builtin/parent/tcp
• go build ./cmd/rootlesskit
• git diff --check

[AkihiroSuda]

Testing

Did you test it with an actual instance of Docker, nerdctl, or something else?