SNMP for Common Lisp

Simple Network Management Protocol (SNMP) is widely used for management of Internet-based network today. In Lisp community, there’re large Lisp-based applications which may need be monitored, and there’re Lispers who may need to monitor other remote systems which are either Lisp-based or not. However, the relationship between Lisp and SNMP haven’t been studied enough during past 20 years. The cl-net-snmp project has developed a new Common Lisp package which implemented the SNMP protocol. On client side, it can be used to query remote SNMP peers, and on server side, it brings SNMP capability into Common Lisp based applications, which could be monitored from remote through any SNMP-based management system. It’s also a flexible platform for researches on network management and SNMP itself. But the most important, this project tries to prove: Common Lisp is the most fit language to implement SNMP. Different from other exist SNMP projects on Common Lisp, cl-net-snmp is clearly targeted on full SNMP protocol support include SNMPv3 and server-side work (agent). During the development, an general ASN.1 compiler and runtime package and an portable UDP networking package are also implemented, which would be useful for other related projects. In this paper, the author first introduces the SNMP protocol and a quick tutorial of cl-net-snmp on both client and server sides, and then the Lisp native design and the implementation details of the ASN.1 and SNMP package, especially the “code generation”’ approach on compiling SNMP MIB definitions from ASN.1 into Common Lisp.

💡 Research Summary

The paper presents “cl‑net‑snmp”, a comprehensive Common Lisp library that implements the Simple Network Management Protocol (SNMP) across all three major versions (v1, v2c, and v3) and provides both client‑side and server‑side functionality. The authors begin by outlining the ubiquity of SNMP in network management and the lack of Lisp‑centric solutions over the past two decades. Existing Lisp projects (e.g., SYSMAN, Valkama’s wrappers) either lack full protocol support, are no longer maintained, or rely on external C libraries, leaving a gap for a pure Lisp implementation that can handle the full MIB (Management Information Base) ecosystem.

The core contribution of the work is a tightly integrated stack consisting of: (1) an ASN.1 compiler that parses MIB definitions and generates Common Lisp source code; (2) a BER (Basic Encoding Rules) encoder/decoder built on a portable CLOS‑based framework; and (3) a high‑level API that abstracts UDP socket handling, session management, and security parameters. The ASN.1 compiler maps ASN.1 SEQUENCE directly to Lisp lists, and OBJECT‑IDENTIFIERs to integer vectors, allowing the compiler to emit defclass forms that represent MIB tables as CLOS classes. This enables object‑oriented access to MIB entries and supports a SQL‑like query interface (snmp:snmp-select) that internally optimizes table retrieval by using a minimal number of GET‑NEXT and GET requests, dramatically reducing packet traffic compared with traditional WALK operations.

On the client side, the library defines three session classes (v1-session, v2c-session, v3-session) and provides the snmp:open-session function and the with-open-session macro for concise resource management. For SNMPv3, the API requires explicit specification of user name, authentication protocol (MD5 or SHA1), and privacy protocol (DES), supporting the three security levels defined by the standard. The library also supplies convenience functions such as asn.1:oid for OID parsing and default parameters for common use‑cases, allowing one‑line queries like (snmp:snmp-get "host" "sysName.0").

The server component is equally lightweight: invoking snmp:enable-snmp-service spawns a dedicated Lisp thread that listens on a configurable UDP port (default 8161) and responds to SNMPv1/v2c requests using the same MIB definitions compiled at load time. Although access control is not yet implemented, the design is modular enough to accommodate future extensions such as SNMPv3 agent support and ACLs.

Portability is a major focus. The UDP networking layer abstracts over the usocket library, enabling the code to run on major Lisp implementations (CMUCL, SBCL, Clozure CL, LispWorks, Allegro CL, Scieneer CL) and operating systems (Linux, Solaris, macOS, Windows). The authors report successful testing across these platforms, demonstrating the library’s robustness.

The paper contrasts the “hard way” (full MIB awareness, name‑to‑OID mapping, dynamic MIB loading) with the “simple way” (using raw numeric OIDs without type information). By choosing the hard way, cl‑net‑snmp preserves all semantic information from the MIB, allowing developers to write high‑level, type‑safe code without manually handling OID tables. The generated CLOS classes can be extended at runtime, making it possible to load new MIB modules on the fly—a capability rarely seen in other language bindings.

Performance considerations are discussed through a concrete example: retrieving the ifTable from IF‑MIB. Using snmp:snmp-select, the library issues only four UDP packets to fetch two rows, whereas a traditional WALK would require 44 packets. This efficiency stems from the pre‑computed table structure and the selective use of GET‑NEXT to discover row counts before bulk fetching.

The authors conclude by emphasizing that Lisp’s macro system and runtime introspection make it uniquely suited for protocol implementations that require both low‑level byte manipulation and high‑level abstraction. They outline future work, including full SNMPv3 agent support, richer security features, implementation of SQL‑like WHERE clauses, and dynamic MIB reload/unload mechanisms.

In summary, “cl‑net‑snmp” demonstrates that Common Lisp can serve as an ideal language for implementing complex network management protocols. It delivers a full‑featured, portable, and extensible SNMP stack, bridges the gap between MIB specifications and executable code through automatic code generation, and introduces high‑level query capabilities that simplify network monitoring tasks for Lisp developers.