This is an emulator of the POSIX network API, designed for use with fuzzers via LD_PRELOAD.

Fuzzers are often incomptatible with applications which perform network IO. Some libraries conveniently support buffer-based IO, used for example by this OpenSSL fuzzer.

But fuzzers rarely explore the full state space of the IO functions that are called by an application. Network functions like recv can return all kinds of errors at any moment, and can send or receive 1..N bytes for any N bytes requested. Such unusual (but legal) responses from the network API can activate code paths that have never been tested before and discover bugs previously overlooked.

I wrote this in mid 2018 and I haven't touched (or used) it since. It is unfinished and it needs more cowbell. I'm releasing it by popular request, and I currently cannot provide support, but I will accept PRs.