Linux-NFS Archive on lore.kernel.org
 help / color / Atom feed
From: Chuck Lever <chuck.lever@oracle.com>
To: Robbie Harwood <rharwood@redhat.com>, Simo Sorce <simo@redhat.com>
Cc: Jeff Layton <jlayton@redhat.com>,
	Bruce Fields <bfields@fieldses.org>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: Fedora 32 rpc.gssd misbehavior
Date: Thu, 30 Jul 2020 13:59:12 -0400
Message-ID: <4EB4AE01-F6D4-4E8F-86BF-C8BB07E63517@oracle.com> (raw)
In-Reply-To: <jlg7dulylq6.fsf@redhat.com>



> On Jul 30, 2020, at 1:08 PM, Robbie Harwood <rharwood@redhat.com> wrote:
> 
> Simo Sorce <simo@redhat.com> writes:
> 
>> On Wed, 2020-07-29 at 14:27 -0400, Chuck Lever wrote:
>>>> On Jul 29, 2020, at 1:19 PM, Chuck Lever <chuck.lever@oracle.com> wrote:
>>>> 
>>>> Hi!
>>>> 
>>>> I recently updated my test systems from EL7 to Fedora 32, and
>>>> NFSv4.0 with Kerberos has stopped working.
>>>> 
>>>> I mount with "klimt.ib" as before. The client workload stops
>>>> dead when the server tries to perform its first CB_RECALL.
>>>> 
>>>> I added some client instrumentation:
>>>> 
>>>>  kernel: NFSv4: Callback principal (nfs@klimt.ib.1015granger.net) does not match acceptor (nfs@klimt.ib).
>>>>  kernel: NFS: NFSv4 callback contains invalid cred
>>>> 
>>>> I boosted gssd verbosity, and it says:
>>>> 
>>>>  rpc.gssd[986]: doing downcall: lifetime_rec=72226 acceptor=nfs@klimt.ib
>>>> 
>>>> But it knows the full hostname for the server:
>>>> 
>>>>  rpc.gssd[986]: Full hostname for 'klimt.ib' is 'klimt.ib.1015granger.net'
>>>> 
>>>> 
>>>> The acceptor appears to come from the Kerberos library. Shouldn't
>>>> it be canonicalized? If so, should the Kerberos library do it, or
>>>> should gssd? Since this behavior appeared after an upgrade, I
>>>> suspect a Kerberos library regression. But it could be config-
>>>> related, since both systems were re-imaged from the ground up.
>>>> 
>>>> Also noticing some other problems on the server (missing hostname
>>>> strings in debug messages, sssd_kcm infinite loops, and gssd
>>>> sending garbage to the client after the NULL request that
>>>> establishes the callback context).
>>>> 
>>>> But let's look at the client acceptor problem first.
>>> 
>>> I believe I found the problem.
>>> 
>>> 8bffe8c5ec1a ("gssd: add /etc/nfs.conf support") added a number of gssd config
>>> options to /etc/nfs.conf, including "avoid-dns". The default setting of avoid-
>>> dns is 1. When I set this option on my client system explicitly to 0, NFSv4.0
>>> with Kerberos works again.
>>> 
>>> Is there a reason the default setting is 1?
>>> 
>> 
>> Now that you mention DNS, this may be an interaction between a new
>> default in Fedora 32 and how your environment is setup re DNS.
>> 
>> In F32 we changed the option dns_canonicalize_hostname from 'true' to
>> 'fallback'.
>> This is a transitional state to eventually move it to 'false' at some
>> point in the future.
>> 
>> What it changes in practice is that it will first try the name passed
>> in *as is* and only as a fallback try a CNAME if the name passed is not
>> resolved as an A name. If you have principals in the KDC for both
>> names, but you do not have keys in the keytab for both, you can have
>> transitional issues.
>> 
>> Additionally we discovered a bug that causes non qualified names to
>> fail resolution with the 'fallback' option.
>> If your name in the principal is really not qualified it will try to
>> qualify it anyway, so if your principal is literally nfs/foo@FOO
>> libgssapi may try to use nfs/foo.my.domdain@FOO, where "my.domain" is
>> what is defined in resolv.conf search path.
>> 
>> We are trying to address this regression.
>> 
>> So try to set dns_canonicalize_hostname to true to see if that may
>> influence your issue. If so, please let me know, as we still need to
>> address this where possible.
> 
> Also, please try setting `qualify_shortname = ""`.  (I did update the
> config file we ship with Fedora, but upstream's default turns that on.
> This is a temporary workaround while we merge something better
> upstream.)

For completeness, I tried:

avoid-dns = 1
dns_canonicalize_hostname = fallback
qualify_shortname = ""

which is the default configuration out of the shrink wrap.

The workload hangs as before, and the acceptor is unqualified:

rpc.gssd[985]: doing downcall: lifetime_rec=84046 acceptor=nfs@klimt.ib


The test is:

Configured domain name is "1015granger.net"

Fully-qualified client hostname is "manet.ib.granger.net"

Fully-qualified server hostname is "klimt.ib.granger.net"

mount command is "mount -o vers=4.0,sec=sys klimt.ib:/export /mnt"

In this case, both systems have keytabs and service principals, so
the client automatically attempts to establish a GSS context for
lease management and callback operations. The failure occurs because
the server's principal is nfs@klimt.ib.1015granger.net but the
acceptor now matches the server hostname from the mount command line,
which is not always fully qualified.


--
Chuck Lever




  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-29 17:19 Chuck Lever
2020-07-29 18:27 ` Chuck Lever
2020-07-30 14:43   ` Steve Dickson
2020-07-30 16:14   ` Simo Sorce
2020-07-30 17:08     ` Robbie Harwood
2020-07-30 17:59       ` Chuck Lever [this message]
2020-07-30 19:10         ` Simo Sorce
2020-07-30 19:39           ` Chuck Lever
2020-07-30 17:09     ` Chuck Lever
2020-07-30 17:57       ` Simo Sorce
2020-07-30 18:07         ` Chuck Lever
2020-07-30 18:20           ` Simo Sorce
2020-07-30 18:29             ` Chuck Lever
2020-07-30 18:55               ` Simo Sorce

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4EB4AE01-F6D4-4E8F-86BF-C8BB07E63517@oracle.com \
    --to=chuck.lever@oracle.com \
    --cc=bfields@fieldses.org \
    --cc=jlayton@redhat.com \
    --cc=linux-nfs@vger.kernel.org \
    --cc=rharwood@redhat.com \
    --cc=simo@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nfs/0 linux-nfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nfs linux-nfs/ https://lore.kernel.org/linux-nfs \
		linux-nfs@vger.kernel.org
	public-inbox-index linux-nfs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-nfs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git