Hans.IP4.ArpTable

Arp Table

data ArpTable

The Arp table consists of a map of IP4 to Mac, as well as a heap that orders the IP4 addresses according to when their corresponding entries should be expired.

NOTE: There's currently no way to limit the memory use of the arp table, but that might not be a huge problem as the entries are added based on requests from higher layers.

INVARIANT: there should never be entries in the map that aren't also in the heap.

newArpTable :: Config -> IO ArpTable

Update

addEntry :: ArpTable -> IP4 -> Mac -> IO ()

Insert an entry into the Arp table, and unblock any waiting actions.

markUnreachable :: ArpTable -> IP4 -> IO ()

If nobody has responded to queries for this address, notify any waiters that there is no mac associated.

NOTE: in the future, it might be nice to keep an entry in the table that indicates that this host is unreachable.

Query

lookupEntry :: ArpTable -> IP4 -> IO (Maybe Mac)

Lookup an entry in the Arp table.

resolveAddr :: ArpTable -> IP4 -> WaitStrategy res -> IO (QueryResult res)

Returns either the address, or an empty MVar that will eventually contain the Mac, or Nothing if the Arp request fails.

data QueryResult res

Constructors

Known !Mac

Unknown !Bool res

data WaitStrategy res

blockingStrategy :: WaitStrategy (MVar (Maybe Mac))

Have the entry block on a

writeChanStrategy :: Maybe DeviceStats -> (Maybe Mac -> Maybe msg) -> BoundedChan msg -> WaitStrategy ()

Write the discovered Mac to a bounded channel, passing it through a filtering function first.