User-space networking stack API allows user-space daemon to
provide TCP/IP stack implementation for NuttX network.
Main use for this is to allow use and seamless integration of
HW-provided TCP/IP stacks to NuttX.
For example, user-space daemon can translate /dev/usrsock
API requests to HW TCP/IP API requests while rest of the
user-space can access standard socket API, with socket
descriptors that can be used with NuttX system calls.
net/socket, net/tcp, net/udp: Add logic to select the domain of the outputgoing packet before sending any UDP or TCP packet. This sets the bit to indicate the IPv4 or IPv6 domain and the correct offset to the output going payload data.
