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Calculate checksums even for Accept action

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If packet has been NAT'd then we certainly need to recalculate the checksum,
but even for direct pass-through it might have been received with an invalid
checksum due to checksum offload. For now, recalculate full checksum in all
cases.

See #1.
This commit is contained in:
Thomas Leonard 2016-01-03 14:14:00 +00:00
parent 96bc12c591
commit 491dbd9323
1 changed files with 7 additions and 4 deletions
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11
firewall.ml
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@ -10,13 +10,18 @@ module Log = (val Logs.src_log src : Logs.LOG)
(* Transmission *)
let transmit ~frame iface =
(* If packet has been NAT'd then we certainly need to recalculate the checksum,
but even for direct pass-through it might have been received with an invalid
checksum due to checksum offload. For now, recalculate full checksum in all
cases. *)
let frame = fixup_checksums frame |> Cstruct.concat in
let packet = Cstruct.shift frame Wire_structs.sizeof_ethernet in
iface#writev [packet]
let forward_ipv4 t frame =
let packet = Cstruct.shift frame Wire_structs.sizeof_ethernet in
match Router.target t packet with
| Some iface -> iface#writev [packet]
| Some iface -> transmit ~frame iface
| None -> return ()
(* Packet classification *)
@ -71,9 +76,7 @@ let pp_packet fmt {src; dst; proto; frame = _} =
(* NAT *)
let translate t frame =
match Nat_rewrite.translate t.Router.nat frame with
| None -> None
| Some frame -> Some (fixup_checksums frame |> Cstruct.concat)
Nat_rewrite.translate t.Router.nat frame
let random_user_port () =
1024 + Random.int (0xffff - 1024)