On Thu, Mar 23, 2017 at 08:07:33PM +0100, Richard Cochran wrote: > On Thu, Mar 23, 2017 at 05:21:45PM +0100, Miroslav Lichvar wrote: > > A better approach might be a control message that would provide the > > original interface index together with the length of the packet, so > > the application could transpose the HW timestamp and map the HW > > interface to the PHC. > > This sounds better than trying to auto-magically transpose and correct > for link speed. > > BTW, isn't there already a control message for "original interface > index"?
There is the PACKET_ORIGDEV option, but it works only with packet sockets, and it doesn't look to me like it could be easily turned into a SO_ORIGDEV option. If there was such an option and also a SO_ORIGLEN option, I think that would work nicely for me. > > The two values could be saved in the skb_shared_info structure. Now > > my question is if they could be useful also for other things than > > timestamping > > such as? I'm not sure. What people do with PACKET_ORIGDEV and would it make sense with other sockets? Googling "PACKET_ORIGDEV" shows implementations of some low-level protocols. > > and if it should be a new socket option which would work > > on any socket independently from timestamping, or if it should rather > > be a new flag for the SO_TIMESTAMPING option. If the latter, would it > > make sense to put them in the skb_shared_hwtstamps structure and > > modify all drivers to set the values when a HW timestamp is captured > > instead of adding more code to __netif_receive_skb_core() or similar? > > This information is solely for a highly specialized NTP application. > No normal program would ever need this, AFAICT. So, if possible, > getting the original frame length should be done in a way that doesn't > affect users that don't need it. Ok. I'll put the two fields to skb_shared_hwtstamps, taking the place of the old syststamp field, and try to avoid adding any code to paths not specific to timestamping. Thanks, -- Miroslav Lichvar
