On Jun 22, 2015, at 3:54 AM, David Garijo <dgman...@live.com> wrote: > Hello, > > I've been thinking of the possibility of adding hardware > support for NTP so that it can timestamp the packets sent and received more > accurately.
OK. NTP talks to local hardware which provides timestamps via clock drivers. Unless you're a vendor releasing a new line of hardware, you'd probably want to use the existing SHM clock driver: https://www.eecis.udel.edu/~mills/ntp/html/drivers/driver28.html > An example of this would be to overwrite the timestamp of the packets (by > hardware) right > before sending/receiving them with the actual time of departure/arrival if a > "hardware support" option is enabled (like some kind of timestamp unit). A common example would be IEEE 1588 Precision Time Protocol timestamp format which is somewhat commonly implemented in ethernet hardware. > It sounds as if I would need to modify the project heavily, so I suppose the > best > and most realistic approach would be to add a new option to the (Linux) > kernel instead of rewriting the ntp programs offered. Hardware timestamp support already exists in the Linux kernel. Consider: http://www.mjmwired.net/kernel/Documentation/networking/timestamping.txt > The code for the NTP daemon (ntpd) is quite complex, so I'm not quite sure > how nor when the packets are sent/received/timestamped. On the other > hand, as far as I've noticed, sntp uses libevent and recvfrom/sendto to > handle the packets, so I tend to think that maybe I should start by taking a > look at sys/socket.h instead of worrying about anything ntp related. Any > suggestions? Do you know of an ideal file/function that I should edit? Well, first you need to figure out whether you're changing kernel drivers to support a new hardware timestamp source, or whether you want to talk to ntpd via SHM or your own clock driver. Regards, -- -Chuck _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
