locking ifpromisc (struct ifnet)

[John Giacomoni]

Currently how should one lock a struct ifnet* so one can safely use
ifpromisc on it?

I'm writting a module similar to the bpf, however I am failing to
follow the correct way to safely establish locking.  Grabbing
[Giant does not seem correct as Giant is being removed]

my understanding is that one uses ifunit to convert
if_name -> struct ifnet *ifp
and then one uses the *ifp in the ifpromisc call.

the safety I'm referring to would be:
a) device deallocation in between  ifunit and ifpromisc.

b) simultaneous calls to ifpromisc

d) a simultaneous ifpromisc call and the device being removed and
deallocated.

my guess would be to grab IFNET_RLOCK or IFNET_WLOCK, then do the
ifunit name -> ifp translation, ifpromisc, then the IFNET_UN[RW]LOCK


is this correct?

for the present?

for the future?

is there a way to acquire a struct ifnet* and keep it around safely?
[perhaps some kind of notification system for when an ifp is no
  longer valid?]

thanks

John G


--

University of Colorado at Boulder          John.Giacomoni at colorado.edu
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