Enum InheritedSocketFate 

pub enum InheritedSocketFate {
    Adopted,
    Refused,
    Unclaimed,
}

What a proxy would do with a listening socket handed to its activate_listener(address).

Server::notify_activate_listener asks BEFORE it pulls a descriptor out of the SCM table, because Listeners::get_* removes the entry as it hands it over while activate() returns on its if self.active guard without consuming anything. Taking a descriptor that nothing will consume drops the owning wrapper on the floor and closes the inherited socket unused — the accept backlog or receive buffer with it (sozu#1342).

Variants

Adopted

A listener exists at the address and is not active: it adopts the socket. Take the descriptor.

Refused

A listener exists at the address and is already active on a socket of its own. activate() short-circuits, so nothing consumes this descriptor now. Close it deliberately.

Not because it could never be adopted: give_back_listener clears active and keeps the listener object, so DeactivateListener followed by ActivateListener — an operator-reachable feature, covered by e2e/src/tests/listener_reactivation_tests.rs — brings this address back to Adopted. Closing here is therefore irreversible: scm_listeners is filled once in Server::new and never refilled, so a reactivation after this point binds a fresh socket.

It is a deliberate trade, not a claim about the lifetime. The only thing this descriptor carries is the connections queued on it at hand-off, and their value decays — the peers behind them time out or reset while the address is served by the listener’s own socket. The cost of keeping it is continuous instead: the descriptor is the retiring worker’s listening socket, still bound with SO_REUSEPORT and registered with no event loop, so the kernel is expected to keep giving it a share of incoming connections that nobody accepts. (That last step follows from SO_REUSEPORT load-balancing semantics; nothing here measures it.) A decaying backlog is not worth an indefinite share of new connections.

Unclaimed

No listener at the address yet. Keep the descriptor in the table: an AddListener + ActivateListener pair can still arrive and adopt it, which is exactly what an upgrade does when the initial state carries the listeners inactive and activates them afterwards.

Trait Implementations

impl Clone for InheritedSocketFate

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for InheritedSocketFate

impl Debug for InheritedSocketFate

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

Formats the value using the given formatter.

impl Eq for InheritedSocketFate

impl PartialEq for InheritedSocketFate

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for InheritedSocketFate