Struct NeighborCache 

pub struct NeighborCache { /* private fields */ }

The neighbor cache: the stack’s map of IP addresses to hardware addresses.

It holds one entry per neighbor, keyed by the interface it is reachable through plus its IP address. Entries are filled in by ARP and neighbor discovery, and expire after 60 s unless traffic from the neighbor refreshes them.

Access it with Stack::neighbor_cache and Stack::neighbor_cache_mut.

Implementations

impl NeighborCache

pub fn get(&self, iface: IfaceHandle, addr: IpAddr) -> Option<Neighbor>

Get the entry for a neighbor.

An entry that expired is reported as NeighborState::Stale from the next poll on, until the stack reuses its slot. Before that poll it is still Reachable, with an expires_at that has passed.

pub fn iter(&self) -> impl Iterator<Item = Neighbor> + '_

Iterate over all entries.

pub fn insert( &mut self, iface: IfaceHandle, addr: IpAddr, hardware_addr: HardwareAddress, expires_at: Instant, ) -> Result<(), NotUnicast>

Add or replace an entry, mapping addr on iface to hardware_addr.

expires_at is when the entry stops being used. There are no static entries. To keep an entry, insert it again before it expires.

The stack changes the entry too:

• Traffic from the neighbor sets it to expire 60 s later.
• ARP or neighbor discovery replaces it if the neighbor answers with a different hardware address.

If the cache is full, another entry is evicted to make room.

Errors

• NotUnicast: if addr or hardware_addr is not unicast. The cache is left unchanged.

pub fn remove(&mut self, iface: IfaceHandle, addr: IpAddr) -> Option<Neighbor>

Remove the entry for a neighbor, returning it if there was one.

Removing an entry whose resolution is still in progress drops the packets parked on it at the next poll.

pub fn retain(&mut self, f: impl FnMut(&Neighbor) -> bool)

Keep only the entries for which f returns true.

Same caveat as NeighborCache::remove for entries being resolved.

pub fn clear_iface(&mut self, iface: IfaceHandle)

Remove all entries for one interface.

Same caveat as NeighborCache::remove for entries being resolved.

pub fn clear(&mut self)

Remove all entries.

Same caveat as NeighborCache::remove for entries being resolved.

pub fn len(&self) -> usize

Number of entries.

pub fn is_empty(&self) -> bool

Whether the cache is empty.

Trait Implementations

impl Debug for NeighborCache

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

Formats the value using the given formatter.