Date: Sun, 18 Jul 1999 10:02:14 +0930 From: Greg Lehey <grog@lemis.com> To: Walter Hafner <hafner@in.tum.de> Cc: Walter Hafner <hafner@informatik.tu-muenchen.de>, questions@FreeBSD.ORG Subject: Re: strange NFS problem Message-ID: <19990718100214.53907@mojave.lemis.com> In-Reply-To: <14218.63691.589830.15439@hprbg5.informatik.tu-muenchen.de>; from Walter Hafner on Tue, Jul 13, 1999 at 10:28:59AM %2B0200 References: <14218.4014.47678.998590@hprbg5.informatik.tu-muenchen.de> <srjwvw5dd71.fsf@hprbg5.informatik.tu-muenchen.de> <19990713112452.U21403@freebie.lemis.com> <14218.63691.589830.15439@hprbg5.informatik.tu-muenchen.de>
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On Tuesday, 13 July 1999 at 10:28:59 +0200, Walter Hafner wrote:
> Thanks for your help. Here's a little more info to clarify things:
>
>> On Monday, 12 July 1999 at 17:54:22 +0200, Walter Hafner wrote:
>>> Host A: FreeBSD 2.2.8 STABLE, NFS Server
>>> Host B: FreeBSD 3.1 RELEASE, NFS Client
>>>
>>> When I do a
>>>
>>> mount /mount/w3proj1/export/data
>>>
>>> on B it hangs forever. When I start mountd with -d on A, it tells me
>>> "mount successful" or something similar (don't have the machine at
>>> hand.)
>>
>> Is system B multi-homed? In other words, does it have more than one
>> IP address? There's a bug in the system which will cause it to accept
>> the mount, but possibly reply with the "other" IP address. This will
>> cause a hang which you can only resolve with a reboot. See PR
>> kern/9612 for more details.
>
> "A", the NFS _server_ is multi-homed. It answers to 6 IP-addresses and
> about 15 names.
Ah. It wasn't quite clear from your description which way round
things run. Yes, this still sounds like the same scenario. Note that
the DNS doesn't have anything to do with the problem, except to
possibly confuse things further.
> I know, what you want to say now ("NFS is Bad(tm) for WWW machines"),
Well, I won't say that.
> I mounted from the DNS-Server CNAME, not from the primary name.
As I said, the DNS is not important. The IP addresses are.
>>> Never mind. I found the problem (apart from the bogus "2" option in
>>> /etc/fstab :-)
>>>
>>> I didn't mount from the machines "A" record name, but from on of the
>>> machines "CNAME"s. The FreeBSD 3.1 mount doesn't seem to like this.
>>
>> If my reasoning above is correct, I don't think that's the solution,
>> unless by changing the name you removed the duplicate IP addresses.
>
> I don't quite understand, what you mean by "removed the duplicate IP
> addresses". All addresses are still valid. I'm no kernel hacker. All I
> can say is: it works now. I tried both configurations (mountpoints) and
> can repeat the behaviour at any time.
The problem appears to be: you do a DNS lookup and get a random IP out
of the ones to which the name answers. You send a mount request to
this address. The request gets accepted, but the answer comes from
the IP address of the interface to the network on which the reply is
sent. Since B isn't looking for that, it rejects it and hangs on the
original reply.
> Looks like the behaviour you describe in 9612. I can especcially verify
> this part:
>
> : Here the mount succeeds on the server side, but the reply contains the
> : address 192.109.197.137, not 139.130.136.133, and is thus rejected by
> : panic. The mount process hangs in sbwait and is not stoppable.
>
> But it seems to me, that mounts from the name in the "A" record always
> succeed.
Remember, it has nothing to do with the names.
> If I can be any help in tracking the bug down, I'll help.
Thanks, but we've tracked down the problem. The real question is, how
do we fix it? I'm looking at that, but I need enough time to
investigate.
Greg
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