Module network_engine 

The pure state machine behind network record and replay.

The engine models the guest-visible state of each outbound TCP channel: which inbound bytes have been released to the guest, whether the peer closed or reset the connection, how many bytes the guest transmitted, and the receive low-water mark. It performs no I/O. The runtime asks it what a guest recv, poll or send observes at a given global time, and in record mode feeds it the bytes it pulled from the host.

Determinism rests on the release rule of NetworkReleaseV1: an input becomes visible once global time has reached the time at which the recording first observed it and the guest has transmitted at least as many bytes on that channel as it had by then. Both quantities are functions of the guest’s own deterministic execution, so a replay never depends on host timing, and a replay that follows the recorded schedule observes every input at the same check that the recording did.

A blocking receive completes once enough bytes are available to satisfy its target, all at once. Linux may copy a partial segment into the buffer of a waiting reader before the rest arrives; the engine instead hands out the bytes as if they had arrived together, which is one of the outcomes Linux permits.

Structs

NetworkEngine

The guest-visible network state of one record or replay run.

SendMark

Where a recorded send left a channel’s outbound stream: its offset, and how many output events (accepted chunks and refused sends) the channel has recorded. A blocking send that waits for buffer space passes its mark back with its next chunk; any output event in between changes events, even a refusal, which does not move offset.

Enums

NetworkArrival

Something the recorder pulled from a host socket.

NetworkEngineError

A failure that ends the run: the guest asked for something the recording cannot answer, or that this version does not model.

NetworkRecvOutcome

What a guest receive observes.

NetworkReply

The answer to a NetworkRequest.

NetworkRequest

One engine operation, carried from a guest thread to the global state.

ReplaySendOutcome

What NetworkEngine::replay_send did with a guest send.

Constants

REPLAY_STALL_LIMIT

How long past an input’s recorded arrival, in global (virtual) time, replay waits for the guest to send the bytes that gate it before declaring that the guest diverged. It has the same length as the host waits of record mode, but those are wall-clock waits.