This commit adds support to simulate Thread radio over IPv6.
With this commit, a simulation will be simulated over either IPv6 or IPv4.
If it's simulated on IPv6, it communicates with other simulation nodes
in IPv6 group `ff02::116`. And if it's simulated on IPv4, it communicates
with other simulation nodes in IPv4 group `224.0.0.116`.
Note that simulating virtual time is not included in this commit.
This commit adds a argument `-L`/`--local-host` to simulation platform
to specify the source IP address for packets simulating 15.4
frames. This allows the simulation packets being transmitted over
different network interfaces, so that the simulation can run on
different hosts.
This can be used to enable multiple emulation devices(e.g. Android
Virtual Device) communicating to each other over emulated Thread
radio.
The argument accepts either an IPv4 address or a network interface
name. In the latter case, the first found IPv4 address on that
interface will be used will be used.
This commit introduces a new module, `simul_utils.h`, under
`simulation` platform. This module provides common utility functions,
primarily related to socket operations (for emulation of radio or
TREL interface). The new functions are used by `radio.c` and
`trel.c`, consolidating code and preventing repetition.
Yakun Xu