[Click] FromDevice on OS-X pooling up packets...

[Nicholas Weaver]

	A minor strangeness on FromDevice:

This is the example configuration I'm using...


FromDevice(en0, PROMISC true) -> CheckIPHeader(14) ->
           IPClassifier(dst udp port 68) -> 
           IPPrint('reply  ') -> 

           CheckDHCPMsg() -> 
           IPPrint('replyok') ->

dhcpc :: DHCPClient(ca:fe:ba:be:00:01, LEASE_CALL newlease.run)
     -> UDPIPEncap(0.0.0.0, bootpc, 255.255.255.255, bootps) 
     -> EtherEncap(0x0800, ca:fe:ba:be:00:01, ff:ff:ff:ff:ff:ff)
     -> IPPrint('request:') -> en0queue::Queue() -> ToDevice(en0);

dhcpc[1] -> dhcp_udp :: UDPIPEncap(0.0.0.0, bootpc, 255.255.255.255, bootps)
     -> EtherEncap(0x0800, ca:fe:ba:be:00:01, ff:ff:ff:ff:ff:ff)
     -> IPPrint('detail:') -> en0queue;

newlease :: Script(TYPE PASSIVE,
   goto end $(not $1),
   write dhcp_udp.src $2,
   write dhcp_udp.dst $3)

(Basically, the DHCPClient example)


The interesting thing, the FromDevice is not receiving individual packets, but only processing data after enough packets are read.  I can see a TCPdump where the DHCP replies are being received, but they are not being received by the click script until I do some activity to dump a bunch of network traffic to the interface (eg, web fetch).

Any thoughts/comments?