[cifs-protocol] 117060115827644 Question about DRS client behaviour with linked attributes

[Tim Beale]

Hi Sreekanth,

Thanks for the link. I'd already seen that article (or one very
similar), but it does provide a lot of useful information about replication.

The Docs issues I mentioned in the conference call are as follows:

1). A fortnight ago, I raised a minor issue with MS-DRSR 4.1.10.6.14
ProcessLinkValue(). i.e.
https://msdn.microsoft.com/en-us/library/dd207759.aspx

In the following block of code that checks the link target, it looks
like it's missing a null check for targetObject.

targetObject = GetDSNameFromAttrVal(replValinf.attrTyp, replValInf.pAval)
if ((IsRecycleBinEnabled() and targetObject!isRecycled) or
    (not IsRecycleBinEnabled() and targetObject!isDeleted)) then
    if (DRS_GET_TGT in ulMoreFlags) then
        /* nothing to do */
        return 0
    else
        return ERROR_DS_DRA_RECYCLED_TARGET
endif

Presumably it should also return ERROR_DS_DRA_RECYCLED_TARGET if
targetObject is null, as this is what triggers the use of the
DRS_GET_TGT flag.

2). Related to this, the error code used here isn't documented, i.e. it
isn't listed on https://msdn.microsoft.com/en-us/library/cc231199.aspx

I think it should be something like:

ERROR_DS_DRA_RECYCLED_TARGET            0x000021BF

Thanks for your help.

Tim

On 08/06/17 09:56, Sreekanth Nadendla wrote:
> Hello Tim, below is the article I mentioned and it provides some useful details about Linked value replication scenarios.
> https://technet.microsoft.com/en-us/library/cc772726(v=ws.10).aspx
>
>
> Regards,
> Sreekanth Nadendla
> Microsoft Windows Open Specifications
>
> -----Original Message-----
> From: Sreekanth Nadendla 
> Sent: Thursday, June 1, 2017 5:03 PM
> To: 'Tim Beale' <timbeale at catalyst.net.nz>
> Cc: cifs-protocol at lists.samba.org; MSSolve Case Email <casemail at microsoft.com>
> Subject: 117060115827644 Question about DRS client behaviour with linked attributes
>
> Hello Tim, I will be assisting you with this issue. 
>
> Regards,
> Sreekanth Nadendla
> Microsoft Windows Open Specifications
>
> -----Original Message-----
> From: Tim Beale [mailto:timbeale at catalyst.net.nz] 
> Sent: Wednesday, May 31, 2017 8:18 PM
> To: Interoperability Documentation Help <dochelp at microsoft.com>; cifs-protocol at lists.samba.org
> Subject: Question about DRS client behaviour with linked attributes
>
> Hi,
>
> We're trying to add DRS GET_TGT support to Samba and have a question about the behaviour of linked attributes. We noticed that you can sometimes get linked attributes that span a partition.
>
> For example you can have an object in the Configuration partition with a linked attribute to an object in the Domain partition:
> dn:
> CN=RWDC,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=SAMDOM,DC=EXAMPLE,DC=COM
> serverReference: CN=RWDC,OU=Domain Controllers,DC=SAMDOM,DC=EXAMPLE,DC=COM
>
> And you can also have an object in the Domain partition with a linked attribute to an object in the Configuration partition:
> dn: CN=RWDC,CN=Topology,CN=Domain System Volume,CN=DFSR-GlobalSettings,CN=System,DC=SAMDOM,DC=EXAMPLE,DC=COM
> serverReference: CN=NTDS
> Settings,CN=RWDC,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=SAMDOM,DC=EXAMPLE,DC=COM
>
> From what I could see from testing, when the DRS_GET_TGT flag is set in the ReplicateNCRequestMsg, Windows does not resolve a target object that is in another partition. 
>
> This results in a cyclical dependency between the partitions being replicated, E.g. you can't commit all the linked attributes in the Domain partition until all the objects in the Configuration partition have been received, but you can't commit all the linked attributes in the Configuration partition until all the objects in the Domain partition have been received. This problem could be resolved if you manage to replicate the target object before the link is replicated.
>
> My question is: how does the Windows replication behaviour resolve this problem?
> - Does this mean the client always has to replicate the partitions in parallel? i.e. it can't replicate them in series because it can't commit an entire partition until it has received portions of another partition.
> - What happens when the client encounters a linked attribute with an unknown target object? ProcessLinkValue() in the MS-DRSR seems to imply the client will ignore it (if it's already tried with GET_TGT). So how does the client ensure that it receives the linked attribute eventually?
>
> Thanks for your help.
>
> Tim
>

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