Struct UdpFlow 

pub struct UdpFlow {
    pub client: SocketAddr,
    pub backend_id: Option<String>,
    pub backend_addr: Option<SocketAddr>,
    pub phase: FlowPhase,
    pub config: ClusterConfig,
    pub requests_seen: u32,
    pub responses_seen: u32,
    pub idle_deadline: Instant,
    pub timer_gen: u64,
    pub first_upstream_pending: bool,
    pub pending_payload: Option<Vec<u8>>,
}

Per-admitted-flow state. Slab slot payload owned by the manager.

Fields

client: SocketAddr

Real (pre-NAT) client source address — the symmetric NAT return target and the PPv2 source address.

backend_id: Option<String>

Resolved backend id, set on BackendResolved.

backend_addr: Option<SocketAddr>

Resolved backend address, set on BackendResolved.

phase: FlowPhase

Lifecycle phase.

config: ClusterConfig

Captured per-cluster knobs (responses/requests/timeouts/PPv2). Captured at admission so a mid-flow reconfig does not change a live flow’s teardown contract (stable affinity).

requests_seen: u32

Client datagrams forwarded so far (counts toward requests).

responses_seen: u32

Backend replies returned so far (counts toward responses).

idle_deadline: Instant

Absolute idle deadline; reset on every datagram in either direction.

timer_gen: u64

Generation token. Incremented every time the idle deadline is pushed back. A wheel expiry only closes the flow when its captured generation still matches — defeating the stale-close busy-loop bug.

first_upstream_pending: bool

True until the first upstream datagram is sent; gates PPv2 prefixing when proxy_protocol_every_datagram is false (first-datagram-only).

pending_payload: Option<Vec<u8>>

One-slot buffer for a client datagram that arrived while AwaitingBackend. Flushed on BackendResolved. A second datagram in the window replaces it (newest wins) rather than allocating an unbounded queue.

Implementations

impl UdpFlow

pub fn new(client: SocketAddr, config: ClusterConfig, now: Instant) -> Self

Create a flow for client, awaiting a backend, with its idle deadline armed front_timeout from now.

pub fn touch(&mut self, timeout: Duration, now: Instant) -> u64

Push the idle deadline back to now + timeout and bump the generation token so any in-flight wheel expiry for the old deadline is invalidated. Returns the new generation so the manager can re-arm the wheel.

pub fn on_client_datagram(&mut self, now: Instant) -> u64

Record that one client datagram was actually forwarded upstream: bump the requests counter and refresh the front idle deadline. Returns the new generation token. Call this only at a real forward site — a datagram merely buffered while AwaitingBackend and later overwritten (newest-wins) must NOT count, or a burst during await could trip the requests cap having delivered fewer than requests datagrams. Use touch for the buffer-only idle refresh.

pub fn on_backend_datagram(&mut self, now: Instant) -> u64

Record that one backend reply was returned; refresh the back idle deadline. Returns the new generation token.

pub fn set_phase(&mut self, next: FlowPhase)

Transition the flow to next, asserting the move is legal. The lifecycle is strictly forward: AwaitingBackend → Established → Closing, with a self-loop allowed only into Closing (idempotent close). A backward move (Established → AwaitingBackend) or skipping straight from AwaitingBackend → Closing is allowed only into Closing (a flow may be aborted before it establishes); every other transition is a bug.

Debug-only guard — the assignment itself is unconditional so release behavior is identical.

pub fn requests_exhausted(&self) -> bool

Whether the requests knob has been exhausted (0 = unlimited).

pub fn responses_exhausted(&self) -> bool

Whether the responses knob has been exhausted (0 = unlimited). A DNS flow with responses = 1 closes after its single reply.

pub fn teardown_reason(&self) -> Option<CloseReason>

The teardown reason if any knob is exhausted, else None. Idle is handled separately by the manager via the timer wheel.

pub fn take_proxy_protocol(&mut self) -> bool

Whether this upstream datagram should carry a PPv2 DGRAM prefix, given the cluster’s first-datagram-only vs every-datagram policy. Marks the first-datagram bookkeeping as consumed.

Trait Implementations

impl Clone for UdpFlow

fn clone(&self) -> UdpFlow

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for UdpFlow

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.