> -----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. In fact the only Extra flag defined is the one that says there's another Extra :-) > > 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. > > > + * flags = 0 > > + * size = fragment size > > + * > > * Ring slot size is 12 octets, however not all request/response > > * structs use the full size. > > * > > @@ -202,6 +202,19 @@ > > * Guest receive > > * ============= > > * > > + * This is the 'wire' format for packets: > > + * Fragment 1: netif_rx_request_t - flags = NETRXF_* > > + * size = fragment size > > + * [Extra 1: netif_extra_info_t] - (only if fragment 1 flags include > > + * NETRXF_extra_info) > > + * [Extra N: netif_extra_info_t] - (only if extra N-1 flags include > > + * XEN_NETIF_EXTRA_MORE) > > + * ... > > + * Fragment N: netif_rx_request_t - (only if fragment N-1 flags include > > + * NETRXF_more_data) > > + * flags = 0 > > + * size = fragment size > > Same Q re which NETRXF_more_data is relevant. > Same answer :-) > In this path there is no indication of the total packet size other than > adding everything up? > Correct. > 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. Paul > > + * > > * Ring slot size is 8 octets. > > * > > * rx request (netif_rx_request_t) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
