Added Multihoming feature to LWIP (ability to use more than one network interfaces) for increasing networking reliability.
This involves:
LWIP interface
LWIP IP routing
DNS storage
Sockets (bind to interface name possibility)
possibility to add non default network interface
cellular middleware modifications if cellular connection is used
Currently, LwIP segment retransmission time is 12, which is very long
time as each timeout doubles the retransmission timeout.
Make that to 6 as that is same what we use in Nanostack.
For speeding up of LWIP in RZ/A1, I added four new config processes in mbed_lib.json and lwipopts.h, overriden those values.
Since RZ/A1 incorporates a large memory, can actualize speeding up by running with the override value.
Also those new config processes will be helpful for more customize.