On 2013/10/03 5:45 PM, "Theodore Ts'o" <tytso@xxxxxxx> wrote: >On Thu, Oct 03, 2013 at 11:06:58PM +0000, Dilger, Andreas wrote: >> >> The Lustre cfs_get_random_bytes() incorporates (via cfs_rand()) a seed >> which also hashes in the addresses from any network interfaces that are >> configured. >> Conversely, cfs_rand() also is seeded at startup from >>get_random_bytes() in >> case a hardware RNG is available. This ensures even with identical >>initial >> conditions cfs_get_random_bytes() gets a different random stream on each >> node. > >With modern kernels, the /dev/random driver has the >add_device_randomness() interface which is used to mix in >personalization information, which includes the network MAC address. >So that particular concern should be covered without the hack of >mixing in cfs_rand(). I think that depends on the network driver. The Cray systems have some very strange networking hardware that is beyond our control - definitely not ethernet or Infiniband. I'll have to ask the Cray folks if their network drivers do this today. >> I'm not against cleaning this up, if there is some mechanism for the >> startup code to add in the node interface addresses into the entropy >> pool, and this is also used to perturb the prandom_u32() sequence >> after that point. > >That's handled too, via the late initcall prandom_reseed(). > >Cheers, > > - Ted > Cheers, Andreas -- Andreas Dilger Lustre Software Architect Intel High Performance Data Division _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
