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[ns] how to determine the value of hdr_cmn::size_



Hi, all

There is one question about how to determine the value of hdr_cmn::size_.

For example, in DSDV.cc, the function "makeUpdate(int)" allocates application
data like this, p->allocdata((change_count * 9) +1), then it sets hdrc->size to 
"change_count * 12 + IP_HDR_LEN"(hdrc->size = change_count * 12 + IP_HDR_LEN).
I don't know why it do this way. Why not setting hdrc->size_ to "change_count * 9 + IP_HDR_LEN"?

thank you for your help

Meng