[launchd-dev] launchd & mDNSResponder: "Policy denied Mach service lookup"

[Damien Sorresso]

On Aug 1, 2009, at 11:38 PM, Björn Giesler wrote:
> Hi,
>
> I've recently migrated to a new MacBook Pro, and since that  
> migration, found that Bonjour no longer worked, and indeed that all  
> applications that used Bonjour just hang. I've traced this to what  
> looks like a problem in the interaction of mDNSResponder and  
> launchd; the log messages I get are lots of
>
> com.apple.launchd[1] (com.apple.mDNSResponder[2551]): Policy denied  
> Mach service lookup: com.apple.distributed_notifications.2
>
> etc.etc. with different services.
>
> I don't yet quite understand how launchd and launched processes  
> interact. Why is launchd responsible for service lookups for other  
> applications? Where are policies stored? etc. The manpage says  
> nothing about this.
>
> I've tried looking for the above message in the launchd code and  
> found it in launchd_core_logic.c in the SULeopard branch, which  
> introduces the mspolicy_* functions, but I'm afraid I can't make  
> much sense of it. I'll try to compile my own launchd and step  
> through it, but it would be nice if somebody could push me in the  
> right direction. (Is there even some documentation on this?) As a  
> Unix rc guy, launchd is a twisty maze of passages, all alike...


mDNSResponder has a policy set on it saying that is is allowed to look  
up only a certain set of MachService names.  
"com.apple.distributed_notifications.2" is not in that list, so we log  
a warning about it. There's probably a framework behind the scenes  
that mDNSResponder uses that is looking up that service.

It's basically a harmless error (I don't believe distributed  
notifications are essential to mDNSResponder's function), but feel  
free to file a bug against mDNSResponder.
-- 
Damien Sorresso
BSD Engineering
Apple Inc.

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