add SO_CNX_ADVICE to sys/socket.h, new in linux v4.6
add SO_CNX_ADVICE to sys/socket.h, new in linux v4.6

new socket option so application can give advice about routing
path quality of connected udp sockets, added in linux commit
a87cb3e48ee86d29868d3f59cfb9ce1a8fa63314

chardi/musl,chardi/musl,chardi/musl