public IpHeader getIpHeader() {
        return mIpHeader;
    }
ICMP messages are sent using the basic IP header. The first octet of the data portion of the
datagram is a ICMP type field; the value of this field determines the format of the remaining
data. Any field labeled "unused" is reserved for later extensions and must be zero when sent,
but receivers should not use these fields (except to include them in the checksum).
Unless otherwise noted under the individual format descriptions, the values of the internet
header fields are as follows:

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Code      |          Checksum             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              TBD                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            Optional                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

See https://tools.ietf.org/html/rfc792

@author Megatron King
@since 2018-10-10 23:04
netbare-core/src/main/java/com/github/megatronking/netbare/ip/IcmpHeader.java