Re: [Xen-devel] [PATCH 5 of 9] xl: Add function to generate random uuid and use it

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Tue, 2010-07-27 at 17:02 +0100, Ian Jackson wrote:
> Gianni Tedesco writes ("Re: [Xen-devel] [PATCH 5 of 9] xl: Add function to 
> generate random uuid and use it"):
> > Nothing wrong with the patch but draws my attention to the fact that
> > this method seems far too likely to collide UUID's, for example in xl
> > invocations started during the same second. Why not use system entropy
> > pool? eg. scanf contents of /proc/sys/kernel/rand/uuid... I'm aware this
> > ought to be portable but PRNG can always be a fallback.
> 
> Yes.
> 
> We should probably use /dev/urandom (on Linux, or I think /dev/random
> on BSD).  If that's not available then we should use rand_r seeded
> with time and pid.

Or perhaps libuuid? It's is used by blktap2 so we already need it, at
least on Linux.

Ian.


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