fix buffer size for control messages

examples/app/app.nim

@@ -1,6 +1,7 @@
 import asyncdispatch, asyncnet, os, strformat, strutils, tables
 from nativeSockets import Domain, SockType, Protocol
 from net import IpAddress, Port, isIpAddress, `$`
+from posix import CMSG_SPACE
 import asyncutils
 import ../../message
 import random
@@ -77,7 +78,8 @@ proc handleServerMessages(conn: ServerConnection) {.async.} =
 proc handlePunchdMessages(conn: PunchdConnection) {.async.} =
   while true:
     let fd = conn.sock.getFd.AsyncFD
-    let resp = await fd.asyncRecvMsg(size = 400, cmsgSize = sizeof(AsyncFD))
+    let cmsgSize = CMSG_SPACE(sizeof(AsyncFD).csize_t)
+    let resp = await fd.asyncRecvMsg(400, cmsgSize)
     let line = resp.data.strip(leading = false, trailing = true, chars = {'\n'})
     echo "received punchd message: ", line
     let args = line.parseArgs(3, 1)

examples/app/asyncutils.nim

@@ -34,7 +34,7 @@ proc getFd*(cmsg: ControlMessage): AsyncFD =
   result = cast[ptr AsyncFD](cmsg.data.cstring)[]
 
 proc asyncRecvMsg*(fd: AsyncFD, size: int = BufferSize,
-                   cmsgSize: int = BufferSize):
+                   cmsgSize: csize_t = BufferSize.csize_t):
                    Future[tuple[data: string, cmsgs: seq[ControlMessage]]] =
   var retFuture = newFuture[tuple[data: string,
                                   cmsgs: seq[ControlMessage]]]("asyncRecvMsg")
@@ -55,7 +55,7 @@ proc asyncRecvMsg*(fd: AsyncFD, size: int = BufferSize,
     var msg = Tmsghdr(msg_iov: addr iovec,
                       msg_iovlen: 1,
                       msg_control: addr cmsgBuffer[0],
-                      msg_controllen: cmsgSize.SockLen)
+                      msg_controllen: cmsgBuffer.len.SockLen)
 
     let res = recvmsg(sock.SocketHandle, addr msg, 0)
     if res < 0: