On 2015-09-07 11:35, Olivier MATZ wrote: >> Wonder why do we need to do that? >> Probably head mbuf is out of space and want to expand it using >> pktmbuf_chain()? >> So in that case seems logical: >> 1) allocate new mbuf (it's pkt_len will be 0) >> b) call pktmbuf_chain() > > By experience, having empty segments in the middle of a mbuf > chain is problematic (functions getting ptr at offsets, some pmds > or hardware may behave badly), I wanted to avoid that risk. > > Now, the use-case you described is legitimate. Another option would > be to have another function pktmbuf_append_new(m) that returns a new > mbuf that is already chained to the other.
I see with that method in that you have to remember to actually update pkt_len in the head buffer when chaining an empty mbuf. Anyway, to disallow this behavior should probably not be the responsibility of rte_pktmbuf_chain(), so I'm fine with leaving the check out. // Simon
