On Fri, 2016-01-08 at 15:56 +0000, Paul Durrant wrote: > > -----Original Message----- > [snip] > > > * Guest transmit > > > * ============== > > > * > > > + * This is the 'wire' format for packets: > > > + * Fragment 1: netif_tx_request_t - flags = NETTXF_* > > > + * size = total packet size > > > + * [Extra 1: netif_extra_info_t] - (only if fragment 1 flags > > > include > > > + * NETTXF_extra_info) > > > + * [Extra N: netif_extra_info_t] - (only if extra N-1 flags > > > include > > > + * XEN_NETIF_EXTRA_MORE) > > > + * ... > > > + * Fragment N: netif_tx_request_t - (only if fragment N-1 flags > > > include > > > + * NETTXF_more_data) > > > > For Fragment 2 is it the Flags of Fragment N-1 = 1 which are relevant, > > or > > the flags in the optional Extra N which may be in the middle (i.e. the > > immediately preceding slot)? > > It's Fragment N-1's flags. The flags on the Extras are not relevant.
I think it would be worth saying that explicitly, even though your text is strictly correct someone might not quite follow. > In fact the only Extra flag defined is the one that says there's another > Extra :-) As opposed to extra types of which there are several. > > > > > Am I correct in remembering that in the presence of NETTXF_more_data the > > only way to know the actual size of Fragment 1 is to take away the total of > > all the extras from Frag 1's size? > > That's right. Can you add a note please? > > Same Q re which NETRXF_more_data is relevant. > > > > Same answer :-) Same request ;-) > > In this path there is no indication of the total packet size other than > > adding everything up? > > > > Correct. Again perhaps worth a note. > > Given that they differ in a subtle way would a quick but explicit > > "NOTE: RX > > and TX differ" be a useful addition do you think? > > > > Yes, that's probably a good plan. I'll stick an extra comment in to that > effect. Ta. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
