SO_SNDBUF and SO_RCVBUF are hard-coded

The two parameters that govern the size of the kernel network buffers are hard-coded to 128k. This is very inflexible and even not defining them would be better as the default value is user-configurable at the kernel level.

Optionally, the parameters can be made configurable inside Maxscale. This way the kernel defaults do not have to be adjusted to allow MaxScale to use more memory if other applications are running on the same machine.