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arXiv 1708.05904cs.PL
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有状态网络的抽象解释

Abstract Interpretation of Stateful Networks

Kalev Alpernas, Roman Manevich, Aurojit Panda, Mooly Sagiv, Scott Shenker, Sharon Shoham, Yaron Velner

摘要:

现代网络通过维护其节点上的状态来实现鲁棒性和可扩展性。这些节点被称为中间盒,对网络功能至关重要。然而,中间盒的存在大大复杂化了网络验证的任务。以前的工作表明,这个问题是不可判定的一般和EXPSPACE完全时,抽象出的数据包到达的顺序。我们描述了一个新的算法,保守地检查有状态网络的隔离特性。该算法的渐近复杂度是多项式的网络的大小,虽然是指数的查询的最大数量的本地状态,中间盒可以做,这往往是小的。我们的算法是合理的,即,它绝不会错过违反安全性的情况,但可能无法验证某些属性。该算法通过以下方式执行动态抽象解释:(1)抽象出分组处理的顺序和每个分组到达的次数,(2)抽象出不同中间盒的状态与信道内容之间的相关性,以及(3)通过中间盒状态对每个分组的影响单独表示中间盒状态,而不是考虑整个状态空间。我们表明,抽象不失去精度时,中间盒可能会在任何状态下重置。这是令人鼓舞的,因为许多真正的中间盒重置,例如,在达到某个会话超时之后或由于硬件故障。

英文摘要:

Modern networks achieve robustness and scalability by maintaining states on their nodes. These nodes are referred to as middleboxes and are essential for network functionality. However, the presence of middleboxes drastically complicates the task of network verification. Previous work showed that the problem is undecidable in general and EXPSPACE-complete when abstracting away the order of packet arrival. We describe a new algorithm for conservatively checking isolation properties of stateful networks. The asymptotic complexity of the algorithm is polynomial in the size of the network, albeit being exponential in the maximal number of queries of the local state that a middlebox can do, which is often small. Our algorithm is sound, i.e., it can never miss a violation of safety but may fail to verify some properties. The algorithm performs on-the fly abstract interpretation by (1) abstracting away the order of packet processing and the number of times each packet arrives, (2) abstracting away correlations between states of different middleboxes and channel contents, and (3) representing middlebox states by their effect on each packet separately, rather than taking into account the entire state space. We show that the abstractions do not lose precision when middleboxes may reset in any state. This is encouraging since many real middleboxes reset, e.g., after some session timeout is reached or due to hardware failure.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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