Warn users about insane maxconnections. #6289

There's some comments where users make statements about how they set their maxconnections to stupid levels (1000+) believing that they will contribute to the network or be safer accepting zero confirmation transactions. Should the client be warning them about how crazy that is, or enforcing some sort of hard cap for the configuration? It seems unlikely that any node is actually able to sustain that number of connections without either becoming unusably slow or running out of file descriptors.

Running out of file descriptors is avoided, see https://github.com/bitcoin/bitcoin/blob/master/src/init.cpp#L727 . It tries to compensate and print a warning to the log, but if not possible it gives an error at startup.

More generally, what is "insane" depends on the hardware and OS. It's entirely possible to handle 1000 connections if there is enough memory available.

Fair enough.