What is the meaning of __attribute__ ((packed))?
A14. In modern computer architectures, the internal representation of a struct with a bunch of fields might contain some bytes of inner padding to align the fields with the word boundaries (this is done for performance reasons). However when you try to send this data, you do not want to send unnecessary padding, because the receiving machine might have a different internal representation. So, what you want the compiler to do is to eliminate any padding, and to pack all fields back to back, so that the internal and the network representation are the same (except perhaps for byte ordering). This is the role of the PACK directives.
