Module `Dns.Probe`

Implements the core of the unique name probing part of a Multicast DNS (mDNS) responder.

type state

The internal data structure representing the of the probing part of an mDNS responder.

type datagram = Packet.t * Ipaddr.V4.t * int

A DNS packet to be sent with its destination IP address and UDP port number.

type action =

| Nothing
(*
The protocol is idle because all names have been confirmed unique.
*)
| ToSend of datagram
(*
The caller shall send the specified datagram.
*)
| Delay of float
(*
The caller shall wait for the specified duration in seconds.
*)
| Continue
(*
The caller should invoke do_probe again.
*)
| NotReady
(*
The call was unexpected. This may indicate a bug in the caller, and should be logged.
*)
| Stop
(*
stop has been called.
*)

The I/O action that the caller of this module must take.

val new_state : Loader.db -> state

Initialises a new mDNS probe protocol.

val add_name : state -> Name.t -> state

Marks a Name.t as unique. The name will be included in the next probe cycle.

val do_probe : state -> state * action

Initiates the probe protocol and returns the I/O action that the caller should take.

val on_send_complete : state -> state * action

After completing a ToSend action, call this function to continue the probe protocol.

val on_delay_complete : state -> state * action

After completing a Delay action, call this function to continue the probe protocol.

val is_first_complete : state -> bool

Returns true if the first probe cycle has completed successfully.

type conflict =

| NoConflict
(*
No conflict occurred.
*)
| ConflictRestart
(*
A conflict occurred. The caller should interrupt any Delay action that is currently executing, if possible.
*)

Indicates whether the received datagram caused a restart of the probe cycle due to a conflict.

val on_response_received : state -> Packet.t -> state * conflict

Call this function when an mDNS response packet is received, in order to check for conflicting resource records.

val on_query_received : 
  state ->
  Packet.t ->
  Packet.t ->
  Packet.t * state * conflict

Call this function when an mDNS query packet is received, in order to check for simultaneous probe conflicts.

val is_confirmed : state -> Name.t -> bool

Returns true if the name has been confirmed unique (probed successfully). This is intended for controlling the cache flush bit.

val stop : state -> state

Stops executing the protocol.

package dns