libneurosim is a general library that provides interfaces and common utility code for neuronal simulators. Currently it provides the ConnectionGenerator interface. The ConnectionGenerator API is a standard interface supporting efficient generation of network connectivity during model setup in neuronal network simulators. It is intended as an abstraction isolating both sides of the API: any simulator can use a given connection generator and a given simulator can use any library providing the ConnectionGenerator interface. It was initially developed to support the use of libcsa from NEST.