package dns-resolver

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Module S.TCP

type nonrec error = private [>
  1. | Tcpip.Tcp.error
]

The type for TCP errors.

type nonrec write_error = private [>
  1. | Tcpip.Tcp.write_error
]

The type for TCP write errors.

type ipaddr = Ipaddr.t

The type for IP address representations.

type flow

A flow represents the state of a single TCP stream that is connected to an endpoint.

type t

The type representing the internal state of the TCP layer.

val disconnect : t -> unit Lwt.t

Disconnect from the TCP layer. While this might take some time to complete, it can never result in an error.

include Mirage_flow.S with type flow := flow and type error := error and type write_error := write_error
val pp_error : error Fmt.t

pp_error is the pretty-printer for errors.

val pp_write_error : write_error Fmt.t

pp_write_error is the pretty-printer for write errors.

read flow blocks until some data is available and returns a fresh buffer containing it.

The returned buffer will be of a size convenient to the flow implementation, but will always have at least 1 byte.

When read returns `Eof or an error, close (or shutdown) should be called on the flow by the client. Once read returned `Eof or an error, no subsequent read call will be successful.

val write : flow -> Cstruct.t -> (unit, write_error) result Lwt.t

write flow buffer writes a buffer to the flow. There is no indication when the buffer has actually been sent and, therefore, it must not be reused. The contents may be transmitted in separate packets, depending on the underlying transport. The result Ok () indicates success, Error `Closed indicates that the connection is now closed and therefore the data could not be written. Other errors are possible.

The promise is resolved when the buffer has been accepted by the implementation (if a partial write occured, write will wait until the remainder of the buffer has been accepted by the implementation).

If write returns an error, close (or shutdown) should be called on the flow by the client. Once write returned an error, no subsequent write or writev call will be successful.

val writev : flow -> Cstruct.t list -> (unit, write_error) result Lwt.t

writev flow buffers writes a sequence of buffers to the flow. There is no indication when the buffers have actually been sent and, therefore, they must not be reused. The result Ok () indicates success, Error `Closed indicates that the connection is now closed and therefore the data could not be written. Other errors are possible.

The promise is resolved when the buffers have been accepted by the implementation (if a partial write occured, writev will wait until all buffers have been accepted by the implementation).

If writev returns an error, close (or shutdown) should be called on the flow by the client. Once writev returned an error, no subsequent writev or write call will be successful.

val shutdown : flow -> [ `read | `write | `read_write ] -> unit Lwt.t

shutdown flow mode shuts down the flow for the specific mode: A flow which is shutdown `read (or `read_write) will never be read again (subsequent calls will return `Eof); a flow which is shutdown `write (or `read_write) flushes all pending writes and signals the remote endpoint there won't be any future write or writev calls (subsequent calls will return `Closed). E.g. in TCP, the signalling is done by sending a segment with the FIN flag.

If this flow is layered upon another flow' (e.g. TLS over TCP), and the internal state after shutdown is `Closed, close on the underlying flow' is executed.

val close : flow -> unit Lwt.t

close flow terminates the flow and frees all associated data. Any subsequent read or write will return an error. A subsequent close will not do anything (esp. not raising an exception), but it may log an error.

If this flow is layered upon another flow' (e.g. TLS over TCP), close on the underlying flow' is executed.

val dst : flow -> ipaddr * int

Get the destination IP address and destination port that a flow is currently connected to.

val src : flow -> ipaddr * int

Get the source IP address and source port that a flow is currently connected to.

val write_nodelay : flow -> Cstruct.t -> (unit, write_error) result Lwt.t

write_nodelay flow buffer writes the contents of buffer to the flow. The thread blocks until all data has been successfully transmitted to the remote endpoint. Buffering within the layer is minimized in this mode. Note that this API will change in a future revision to be a per-flow attribute instead of a separately exposed function.

val writev_nodelay : flow -> Cstruct.t list -> (unit, write_error) result Lwt.t

writev_nodelay flow buffers writes the contents of buffers to the flow. The thread blocks until all data has been successfully transmitted to the remote endpoint. Buffering within the layer is minimized in this mode. Note that this API will change in a future revision to be a per-flow attribute instead of a separately exposed function.

val create_connection : ?keepalive:Tcpip.Tcp.Keepalive.t -> t -> (ipaddr * int) -> (flow, error) result Lwt.t

create_connection ~keepalive t (addr,port) opens a TCP connection to the specified endpoint.

If the optional argument ?keepalive is provided then TCP keep-alive messages will be sent to the server when the connection is idle. If no responses are received then eventually the connection will be disconnected: read will return Ok `Eof and write will return Error `Closed

val listen : t -> port:int -> ?keepalive:Tcpip.Tcp.Keepalive.t -> (flow -> unit Lwt.t) -> unit

listen t ~port ~keepalive callback listens on port. The callback is executed for each flow that was established. If keepalive is provided, this configuration will be applied before calling callback.

val unlisten : t -> port:int -> unit

unlisten t ~port stops any listener on port.

val input : t -> src:ipaddr -> dst:ipaddr -> Cstruct.t -> unit Lwt.t

input t returns an input function continuation to be passed to the underlying IP layer.