Allow the sim to set the MTU of netdevice and support the jumbo frame.

[liqinhuixm]

Summary

Support the jumbo frame in the sim.

• First, support setting mtu on sim;
• Then, optimize the use of iob by jumbo frame packets, and pre-alloc an iob in the protocol stack for each jumbo frame packet, supporting the ICMP, UDP and TCP.

Impact

The sim can support the JUMBO frame packets.

Testing

• First, configure the options,

CONFIG_SIM_NETDEV_MTU = 3000
CONFIG_NET_JUMBO_FRAME=y

• Then, we use the ICMP to test.

ping -s 3000 10.0.1.1

• Finally, capture packets on nuttx0 using the Wireshark. We should be able to see ICMP packets with the length of 3042 bytes.