We have updated the paper to handle empty non-terminals as per the RFCs properly. The updated paper is available through the above PDF link.


The Domain Name System (DNS) plays a vital role in today’s Internet but relies on complex distributed management of host records. DNS misconfiguration related outages have rendered popular services like GitHub, HBO, LinkedIn, and Azure inaccessible for extended periods. This paper introduces GRoot, the first verifier that performs static analysis of DNS configuration files enabling proactive and exhaustive checking for common DNS bugs; by contrast, existing solutions are reactive and incomplete. GRoot uses a new, fast verification algorithm based on generating and enumerating DNS query equivalence classes. GRoot symbolically executes the set of queries in each equivalence class to efficiently find (or prove the absence of) any bugs such as rewrite loops. To prove the correctness of our approach, we develop a formal semantic model of DNS resolution. Applied to the configuration files from a campus network with over a hundred thousand records, GRoot revealed 109 bugs within seconds. When applied to internal zone files consisting of over $3.5$ million records from a large infrastructure service provider, GRoot revealed around $160k$ issues of blackholing, initiating a cleanup. Finally, on a synthetic dataset with over $65$ million real records, we find GRoot can scale to networks with tens of millions of records.

BibTeX Citation

    author = {Kakarla, Siva Kesava Reddy and 
              Beckett, Ryan and
              Arzani, Behnaz and
              Millstein, Todd and
              Varghese, George},
    title = {GRoot: Proactive Verification of DNS Configurations},
    year = {2020},
    isbn = {9781450379557},
    publisher = {Association for Computing Machinery},
    address = {New York, NY, USA},
    url = {},
    doi = {10.1145/3387514.3405871},
    booktitle = {Proceedings of the Annual Conference of the ACM Special Interest Group on Data Communication on the Applications, Technologies, Architectures, and Protocols for Computer Communication},
    pages = {310–328},
    numpages = {19},
    keywords = {Static Analysis, Verification, DNS, Formal Methods},
    location = {Virtual Event, USA},
    series = {SIGCOMM ’20}