Interface contracts for TinyOS

Abstract

TinyOS applications are built with software components that communicate through narrow interfaces. Since components enable finegrained code reuse, this approach has been successful in creating applications that make very efficient use of the limited code and data memory on sensor network nodes. However, the other important benefit of components-rapid application development through black-box reuse-remains largely unrealized because in many cases interfaces have implied usage constraints that can be the source of frustrating program errors. Developers are commonly forced to read the source code for components, partially defeating the purpose of using components in the first place. Our research helps solve these problems by allowing developers to explicitly specify and enforce component interface contracts. Due to the extensive reuse of the most common interfaces, implementing contracts for a small number of frequently reused interfaces permitted us to extensively check a number of applications. We uncovered some subtle and previously unknown bugs in applications that have been in common use for years.

On software verification for sensor nodes

“…While its scope is limited to TOSThreads applications written in C, it avoids some of the costs of system-wide veri!cation by writing models for the interfaces to system calls (in the style of the runtime interface contracts Archer et al (2007)). Calling amRadioReceive(&msg, ...) from the application is modelled so that it preserves its original behaviour: the call returns any of a set of error codes, and the msg variable receives (possibly nondeterministic) data.…”

Bug-Free Sensors: The Automatic Verification of Context-Aware TinyOS Applications

“…the verification of a null-pointer claim for PatientNode takes 24.5s. The interface contracts [6] act like our own checks of interface use, only at runtime. Both differ from our tool in providing safety at runtime-when the sensor node is possibly deployed out of reach.…”

Using CSP to Model and Analyze TinyOS Applications

“…To support such analysis, Archer et al [15] recently proposed the addition of interface contract specifications to TinyOS applications. Contracts are checked at runtime, and can provide useful diagnostic information when an error is encountered.…”