question: public int write ( byte [ ] destMac , byte [ ] packet , int offset , int byteCount ) { if ( destMac == null ) { throw new NullPointerException ( "destMac == null" ) ; } if ( packet == null ) { throw new NullPointerException ( "packet == null" ) ; } Arrays . checkOffsetAndCount ( packet . length , offset , byteCount ) ; if ( destMac . length != 6 ) { throw new IllegalArgumentException ( "MAC length must be 6: " + destMac . length ) ; } return sendPacket ( fd , mInterfaceName , mProtocolType , destMac , packet , offset , byteCount ) ; }
target:  Writes a raw packet to the desired interface.  A L2 header will be added which includes the specified destination address, our source MAC, and the specified protocol type.  The caller is responsible for computing correct IP-header and payload checksums.