Unbound 1.7.1 failing on some kvm servers

W.C.A. Wijngaards wouter at nlnetlabs.nl
Mon May 28 07:25:30 UTC 2018


Hi James,

On 25/05/18 19:06, James Cloos via Unbound-users wrote:
>>>>>> James Cloos via Unbound-users <unbound-users at unbound.net> writes:
> 
>> I have a number of kvm instances running debian where unbound 1.7.1
>> fails.
> 
> An LD_PRELOAD lib which implments getentropy(3) via read(3)ing
> urandom(4) solved the bug.
> 
> Unbound *always* should fall back to urandom(4) when getentropy(3)
> results in ENOSYS, even when compiled against a kernel which advertizes
> support for getrandom(2).

But Unbound does that!  It falls back to that when the other results in
ENOSYS.

What could be happening is that configure detects arc4random.  If that
is the case, Unbound calls that arc4random.  And then this library call
has to call getentropy, and it could be that that could does not
fallback?  You can check the configure output for the arc4random check.
Or afterwards in config.log or config.h (HAVE_ARC4RANDOM is defined or
not defined).

If that is not the case, then we'd need to go for having log printout
for debug to see what happens.

Best regards, Wouter

> 
> -JimC
> 


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