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icmp.ml
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icmp.ml
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(*
* Copyright (c) 2010-2011 Anil Madhavapeddy <anil@recoil.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*)
open Lwt
open Printf
open Nettypes
cstruct icmpv4 {
uint8_t ty;
uint8_t code;
uint16_t csum;
uint16_t id;
uint16_t seq
} as big_endian
type t = {
ip: Ipv4.t;
}
let input t src frame ipv4_hdr ipv4_payload =
match get_icmpv4_ty ipv4_payload with
|0 -> (* echo reply *)
return (printf "ICMP: discarding echo reply\n%!")
|8 -> (* echo request *)
(* convert the echo request into an echo reply *)
let csum =
let orig_csum = get_icmpv4_csum ipv4_payload in
let shift = if orig_csum > 0xffff -0x0800 then 0x0801 else 0x0800 in
(orig_csum + shift) land 0xffff in
set_icmpv4_ty ipv4_payload 0;
set_icmpv4_csum ipv4_payload csum;
(* stick an IPv4 header on the front and transmit *)
lwt (ipv4_frame, ipv4_len) =
Ipv4.get_header ~frame ~proto:`ICMP ~dest_ip:src t.ip in
let ipv4_frame = Cstruct.set_len ipv4_frame ipv4_len in
Ipv4.write t.ip ipv4_frame ipv4_payload >|= fun () ->
OS.Io_page.recycle Cstruct.(frame.buffer)
|ty ->
printf "ICMP unknown ty %d\n" ty;
return ()
let create ip =
let t = { ip } in
Ipv4.attach ip (`ICMP (input t));
let th,_ = Lwt.task () in
Lwt.on_cancel th (fun () ->
printf "ICMP: shutting down\n%!";
Ipv4.detach ip `ICMP;
);
t, th