As the protocol documentation support team, we have the responsibility of helping the users of our published Microsoft Open Protocol Documentation achieve successful interoperability with Windows. There’s more to interoperability than just good technical documentation; engagement with partners is essential.
One of our team’s most active partners is the Samba team, whose main areas are remote file system and Active Directory. Recently, I had the chance to attend the second Samba IO Lab hosted in the Microsoft Enterprise Engineering Center (ECC), an event dedicated to testing the Samba implementation against Windows. It was an incredible experience for me to support the testing and debugging activities during the event. We achieved very positive results at the end of week in a pretty dramatic fashion, as described in Andrew Bartlett’s blog. In this blog, I would like to share my experiences and thoughts from the perspective of a supporting Escalation Engineer.
The Samba IO event was held in the ECC from 09/21 to 09/25. Before the event, the ECC already set up the testing environment that consists of four domains with different domain functional levels. Everyone in the event felt that the lab environment was excellent. A group of five Samba developers arrived after attending another interoperability event. The Samba team was prepared to test protocols they implemented or changed lately, including DRSR, LDAP with complete schema and AES support in Netlogon. The main focus was to have a Windows DC join to a Samba domain that holds all FSMO roles and perform a complete replication.
After the initial meeting, it was decided that I would work with Tridge (Andrew Tridgell) on the main issue of domain join and replication, while other Samba team members started working on protocol testing using the Microsoft Protocol Documentation test suites. At the time, the AD Domain Servicecould not be installed due to an internal error when dcPromo was run to promote the Windows Server 2008 R2 to a DC in a Samba domain. Our first approach was to check log files generated in domain join and the DC promotion processes and the very detailed logs produced by Samba. We identified that the problem happened somewhere after domain join, but before any replication was attempted. The error can be linked to many possible root causes. We tried several approaches associated with the error and nothing worked. We finally decided that we would capture a Time Travel Trace and run live debugging with Windows source attached. We also captured ETW trace to assist in identifying the module for debugging. (Even though I used private symbols to assist in the debugging, any developer can still utilize the Windows debugger and public symbols, to gain more information about the parameters passed into and returned from the interface functions.) In this way, I could run debugging to figure out the real reason behind the behavior and Samba team could make changes based on the information I provided and also continue their debugging and code modification in parallel. After a whole day of debugging , we finally found out that the root cause of problem was that the RootDomainSID returned from a Samba DC through LDAP query of attribute ncName uses upper case letters (A to F) for the string representation of SID. But Windows only processes the string representation of SID in lower case. We were very excited, thinking that replication would start and everything should work right away. Just as Andrew documented in his blog, the moment didn’t come for another four days, with many traces analyzed and more than ten problems identified and fixed. This proved that tracing through the source code for the logic at this detailed level can be very useful for the debugging of interoperability solutions.
After a long week (> 60 hours) of working side by side with Samba team, I was really impressed by the Samba team’s professionalism, passion, dedication, protocol knowledge, programming and debugging skills and team work spirit and really enjoyed working with the entire team. Many times, they identified problems quickly and made correct changes on the fly. We shared many happy and frustrated moments and everyone agreed that we had a very productive week. Without the joint debugging effort between the Samba and Microsoft teams, it would not be possible to achieve so much while they were here. Hopefully this can become a model for the future Interoperability lab events for Samba and other partners.
I am looking forward to working on the Samba IO event again in the future!