mDSNResponder goes into endless loop

Question

Level 1

9 points

mDSNResponder goes into endless loop

Since updating to Snow Leopard, mDSNResponder stays in a constantly active loop.
Little Snitch tells me who's making what connections at what time, and as soon as I launch Safari 4.0.3 it shows mDNSResponder constantly active, even after I quit Safari. (I noticed that Firefox does the same thing, but Camino doesn't start this endless mDNSResponder loop).

The mDNSResponder activity only stops if I force it to stop. With Leopard, and all OSs before it, mDNSResponder activated when it needed to, then stopped after each process was complete.

I sample mDNSResponder in Activity Monitor and it even says it's in a loop.
This certainly is not correct. Any info would be appreciated. Thanks.

iMac 24" (2009), Mac OS X (10.6), Qwest DSL internet connection

Posted on Sep 1, 2009 11:31 PM

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Answer 1

Snoop Dogg

Level 4

1,502 points

Sep 1, 2009 11:35 PM in response to DemoRay

Hi DemoRay. Can you post the mDNSResponder sample from Activity Monitor?

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Answer 2

DemoRay Author

Level 1

9 points

Sep 1, 2009 11:37 PM in response to Snoop Dogg

Thanks for your reply.
No matter how many times I sample the process, it says basically this same thing.
Here's the sample from Activity Monitor:

Analysis of sampling mDNSResponder (pid 37) every 1 millisecond
Call graph:
2689 Thread_370 DispatchQueue_1: com.apple.main-thread (serial)
2689 start
2689 _start
2689 main
2689 CFRunLoopRun
2689 CFRunLoopRunSpecific
2689 __CFRunLoopRun
2689 mach_msg
2689 mach msgtrap
2689 Thread_407 DispatchQueue_2: com.apple.libdispatch-manager (serial)
2689 start_wqthread
2689 pthreadwqthread
2689 dispatch_workerthread2
2689 dispatch_queueinvoke
2689 dispatch_mgrinvoke
2689 kevent
2689 Thread_492
2689 thread_start
2689 pthreadstart
2689 KQueueLoop
2686 kevent
3 mDNS_Execute
3 SendQueries
3 uDNS_CheckCurrentQuestion
3 mDNSPlatformUDPSocket
3 SetupSocket
1 bind
1 setsockopt
1 socket

Total number in stack (recursive counted multiple, when >=5):

Sort by top of stack, same collapsed (when >= 5):
kevent 5375
mach msgtrap 2689

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Answer 3

Dogcow-Moof

Level 8

36,851 points

Sep 2, 2009 3:27 AM in response to DemoRay

Unless you're running Little Snitch 2.2 beta, the current release version is incompatible with Snow Leopard, which could be your issue right there.

http://www.obdev.at/products/littlesnitch/faq.html

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Answer 4

DemoRay Author

Level 1

9 points

Sep 2, 2009 8:38 AM in response to Dogcow-Moof

Yes, I actually am using the Little Snitch 2.2 beta which is compatible with SL, so that's not the issue.
But thanks for the reply.

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Answer 5

Sep 2, 2009 9:07 AM in response to DemoRay

Why do you think that what you're seeing is (a) not normal, (b) causing some problem, or (c) in any way different to Tiger or Leopard?

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Answer 6

Sep 2, 2009 9:09 AM in response to DemoRay

Are you sure it's not the issue? I'd say, quit Little Snitch altogether (remove it) and see if the issue clears up. Then you will know for sure: Little Snitch does cause all sorts of issues.

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Answer 7

DemoRay Author

Level 1

9 points

Sep 3, 2009 3:26 PM in response to William Lloyd

Thanks for the suggestions, but I have removed Little Snitch, it is definitely not the issue.
For some reason, ONLY in Snow Leopard, my network is constantly sending and receiving data. ALWAYS. It never stops unless I force it to.
Before Snow Leopard, mDSNResponder would quickly resolve the host name, then go idle until the next task. Now it loops endlessly, sending and receiving data at all times. This is unnecessary and a sign that something is not right.

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Answer 8

Snoop Dogg

Level 4

1,502 points

Sep 3, 2009 3:30 PM in response to DemoRay

No, it's a sign that mDNSResponder is doing all DNS lookups in SnowLeopard, where in previous versions of Mac OS X, it only did lookups for Bonjour related stuff. That's why it's doing a lot when loading a web page in Safari. It's handling all the DNS lookups for you.

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Answer 9

Snoop Dogg

Level 4

1,502 points

Sep 3, 2009 3:31 PM in response to DemoRay

No, it's a sign that mDNSResponder is doing all DNS lookups in SnowLeopard, where in previous versions of Mac OS X, it only did lookups for Bonjour related stuff. That's why it's doing a lot when loading a web page in Safari. It's handling all the DNS lookups for you.

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Answer 10

DemoRay Author

Level 1

9 points

Sep 3, 2009 9:11 PM in response to Snoop Dogg

Actually, I've got good news.
After screwing with this issue for three days with no results, I finally started from scratch. I erased and installed Snow Leopard from the beginning, and the problem has solved itself.

Previously I had upgraded from Leopard to Snow Leopard, because I only bought the Upgrade DVD. So I went and bought the full install version of SL, did an Erase and Install, and voila, the mDNSResponder went back to working properly, and so did a few other irritating issues that had appeared since upgrading to SL.

It's a drastic measure to start over from scratch, and it can be a real chore, but I'm glad I did it.

I'm happy again! Thank you all for your help.

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Answer 11

Sep 4, 2009 9:39 PM in response to DemoRay

umm DemoRay.... im sorry to tell you that there is no difference from the "update" version and the "full" version of Snow Leopard, the only difference the second time might be that you "erased" the hard drive before install... and i hope/doubt u didnt "buy" 2 versions... seeing as they are the same...

On the topic at hand... mDSNResponder does have alot more activity in snow leopard do to the new features it handles, but see my topic that can help you reduce the traffic within it:

http://forums.macrumors.com/showthread.php?p=8417664#post8417664

it should help =)

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Answer 12

DemoRay Author

Level 1

9 points

Sep 5, 2009 3:16 AM in response to MWithersIT

Yes, as I said in my last post, I did erase and install once I got the full version. Seeing as how the Upgrade version does not give you that option, I did need the full version to do it. And once again, it made all the difference.

Thanks for the tip on reducing mDNSResponder traffic.

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Answer 13

The hatter

Level 9

61,031 points

Sep 5, 2009 5:29 AM in response to DemoRay

To erase before install, just have to go to Utility menu, open Disk Utility, before beginning Install.

I used that to repair hard drive first, then installed.

Erasing the hard drive and not your Mac Extended HFS+ volume, also insures that the parition tables are setup correctly.

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Answer 14

Sep 5, 2009 7:47 AM in response to DemoRay

Seriously... I hope u didnt pay twice... i mean, the "update" disk/dmg you bought/downloaded can be "booted" to and then your hard drive can be "formatted" from disk utility within disk-boot-up...

so the only difference was you wanted to get a pretty cover that doesnt say update =P

oh, i just noticed, the guy above me stated same thing =)

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Answer 15

Sep 5, 2009 2:40 PM in response to DemoRay

Update: i found a site that claims to have links for new snow leopard support, one of which "how to disable bonjour without disabling mDNSResponder in OSX 10.6"... which is what i have been waiting for!!:

http://www.xlr8yourmac.com/index.html#S25936

http://support.apple.com/kb/HT3789?viewlocale=en_US

BUT THE SECOND LINK IS BROKEN!!! i still dont know how to do this!!

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