Affiliation:
1. Cornell University, USA
2. ENS Rennes, France
Abstract
P4 is a domain-specific language for programming and specifying packet-processing systems. It is based on an elegant design with high-level abstractions like parsers and match-action pipelines that can be compiled to efficient implementations in software or hardware. Unfortunately, like many industrial languages, P4 has developed without a formal foundation. The P4 Language Specification is a 160-page document with a mixture of informal prose, graphical diagrams, and pseudocode, leaving many aspects of the language semantics up to individual compilation targets. The P4 reference implementation is a complex system, running to over 40KLoC of C++ code, with support for only a few targets. Clearly neither of these artifacts is suitable for formal reasoning about P4 in general.
This paper presents a new framework, called Petr4, that puts P4 on a solid foundation. Petr4 consists of a clean-slate definitional interpreter and a core calculus that models a fragment of P4. Petr4 is not tied to any particular target: the interpreter is parameterized over an interface that collects features delegated to targets in one place, while the core calculus overapproximates target-specific behaviors using non-determinism.
We have validated the interpreter against a suite of over 750 tests from the P4 reference implementation, exercising our target interface with tests for different targets. We validated the core calculus with a proof of type-preserving termination. While developing Petr4, we reported dozens of bugs in the language specification and the reference implementation, many of which have been fixed.
Funder
Infosys
Fujitsu
Defense Advanced Research Projects Agency
National Science Foundation
Keysight Technologies
Publisher
Association for Computing Machinery (ACM)
Subject
Safety, Risk, Reliability and Quality,Software
Cited by
11 articles.
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1. P4b: A Translator from P4 Programs to Boogie;Proceedings of the 31st ACM Joint European Software Engineering Conference and Symposium on the Foundations of Software Engineering;2023-11-30
2. P4R-Type: A Verified API for P4 Control Plane Programs;Proceedings of the ACM on Programming Languages;2023-10-16
3. P4Testgen: An Extensible Test Oracle For P4-16;Proceedings of the ACM SIGCOMM 2023 Conference;2023-09
4. Semantics and Scheduling for Machine Knitting Compilers;ACM Transactions on Graphics;2023-07-26
5. Toward Highly Reliable Programmable Data Planes: Verification of P4 Code Generation;2023 IEEE 9th International Conference on Network Softwarization (NetSoft);2023-06-19