Module Arp_packet

Conversion between wire and high-level data

The high-level datatype can be decoded and encoded to bytes to be sent on the wire. ARP specifies hardware and protocol addresses, but this implementation picks Ethernet and IPv4 statically. While decoding can result in an error, encoding can not.

type op =
| Request
| Reply
val op_to_int : op -> int
val int_to_op : int -> op option
type t = {
operation : op;
source_mac : Macaddr.t;
source_ip : Ipaddr.V4.t;
target_mac : Macaddr.t;
target_ip : Ipaddr.V4.t;
}

The high-level ARP frame consisting of the two address pairs and an operation.

val size : int

size is the size of an ARP frame.

val pp : Stdlib.Format.formatter -> t -> unit

pp ppf t prints the frame t on ppf.

val equal : t -> t -> bool

equal a b returns true if frames a and b are equal, false otherwise.

type error =
| Too_short
| Unusable
| Unknown_operation of Cstruct.uint16

The type of possible errors during decoding

  • Too_short if the provided buffer is not long enough
  • Unusable if the protocol or hardware address type is not IPv4 and Ethernet
  • Unknown_operation if it is neither a request nor a reply
val pp_error : Stdlib.Format.formatter -> error -> unit

pp_error ppf err prints the error err on ppf.

Decoding

val decode : Cstruct.t -> (t, error) Stdlib.result

decode buf attempts to decode the buffer into an ARP frame t.

Encoding

val encode : t -> Cstruct.t

encode t is a buf, a freshly allocated buffer, which contains the encoded ARP frame t.

val encode_into : t -> Cstruct.t -> unit

encode_into t buf encodes t into the buffer buf at offset 0.

raises Invalid_argument

if the buffer buf is too small (below 28 bytes).