Re: [PATCH 02/14] nfsd: Add missing gen_confirm in nfsd4_setclientid()

[Kinglong Mee <kinglongmee@gmail.com>]

On 7/16/2015 04:49, J. Bruce Fields wrote:
> On Wed, Jul 15, 2015 at 04:47:48PM -0400, J. Bruce Fields wrote:
>> On Mon, Jul 13, 2015 at 05:29:41PM +0800, Kinglong Mee wrote:
>>> Commit 294ac32e99 "nfsd: protect clid and verifier generation with client_lock"
>>> have moved gen_confirm() to gen_clid().
>>
>> This means the statement in that earlier commit is wrong:
>>
>> 	
>> 	With this, there's no need to keep two counters as they'd always
>> 	be in sync anyway, so just use the clientid_counter for both.
>>
>> Looks to me like this may need a separate counter to eliminate the
>> possibibility of returning the same confirm twice for a one clientid?

Yes, nfsd will generate same confirm for one clientid in one second.

 verf[0] = (__force __be32)jiffies;
 verf[1] = (__force __be32)nn->clientid_counter;

for case 1: probable callback update, the new unconf client needs
a different confirm.

Rereading rfc7530,
   x  be the value of the client.id subfield of the SETCLIENTID4args
      structure.

   v  be the value of the client.verifier subfield of the
      SETCLIENTID4args structure.

   c  be the value of the client ID field returned in the
      SETCLIENTID4resok structure.

   k  represent the value combination of the callback and callback_ident
      fields of the SETCLIENTID4args structure.

   s  be the setclientid_confirm value returned in the SETCLIENTID4resok
      structure.

   { v, x, c, k, s }  be a quintuple for a client record.  A client
      record is confirmed if there has been a SETCLIENTID_CONFIRM
      operation to confirm it.  Otherwise, it is unconfirmed.  An
      unconfirmed record is established by a SETCLIENTID call.

... /* case 1: probable callback update */ ... 

   o  The server checks if it has recorded a confirmed record for { v,
      x, c, l, s }, where l may or may not equal k.  If so, and since
      the id verifier v of the request matches that which is confirmed
      and recorded, the server treats this as a probable callback
      information update and records an unconfirmed { v, x, c, k, t }
      and leaves the confirmed { v, x, c, l, s } in place, such that
      t != s.  It does not matter whether k equals l or not.  Any
      pre-existing unconfirmed { v, x, c, *, * } is removed.

      The server returns { c, t }.  It is indeed returning the old
      clientid4 value c, because the client apparently only wants to
      update callback value k to value l.  It's possible this request is
      one from the Byzantine router that has stale callback information,
      but this is not a problem.  The callback information update is
      only confirmed if followed up by a SETCLIENTID_CONFIRM { c, t }.

      The server awaits confirmation of k via SETCLIENTID_CONFIRM
      { c, t }.

      The server does NOT remove client (lock/share/delegation) state
      for x.

> 
> (but frankly I can never completely review changes to the
> setclientid/setclientid_confirm behavior without rereading RFC 7530
> 16.33.5 every time, which is a slog.  Might help to contrive a pynfs
> test derived from that text which tests for this particular behavior.)
> 

Make sense.
I will make it later.

thanks,
Kinglong Mee


>>
>> --b.
>>
>>>
>>> After it, setclientid will return a bad reply with all zero confirms
>>> after copy_clid().
>>>
>>> Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
>>> ---
>>>  fs/nfsd/nfs4state.c | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index e0a4556..b1f84fc 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -3042,10 +3042,11 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>>  	unconf = find_unconfirmed_client_by_name(&clname, nn);
>>>  	if (unconf)
>>>  		unhash_client_locked(unconf);
>>> -	if (conf && same_verf(&conf->cl_verifier, &clverifier))
>>> +	if (conf && same_verf(&conf->cl_verifier, &clverifier)) {
>>>  		/* case 1: probable callback update */
>>>  		copy_clid(new, conf);
>>> -	else /* case 4 (new client) or cases 2, 3 (client reboot): */
>>> +		gen_confirm(new, nn);
>>> +	} else /* case 4 (new client) or cases 2, 3 (client reboot): */
>>>  		gen_clid(new, nn);
>>>  	new->cl_minorversion = 0;
>>>  	gen_callback(new, setclid, rqstp);
>>> -- 
>>> 2.4.3
>