Squashed commit of the following:
net/udp: Address most of the issues with UDP write buffering. There is a remaining issue with handling one network going down in a multi-network environment. None of this has been test but it is certainly ready for test. Hence, the feature is marked EXPERIMENTAL.
net/udp: Some baby steps toward a corrected write buffering design.
net/udp: Remove pesky write buffer macros.
Eliminate trailing space at the end of lines.
net/udp: A little more UDP write buffering logic. Still at least on big gaping hole in the design.
net/udp: Undefined CONFIG_NET_SENDTO_TIMEOUT.
net/udp: Crude, naive port of the TCP write buffering logic into UDP. This commit is certainly non-functional and is simply a starting point for the implementatin of UDP write buffering.
net/udp: Rename udp/udp_psock_sendto.c udp/udp_psock_sendto_unbuffered.c.
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.
