[Interest] Packet arrival-time resolution? QUdpSocket

[Jason H]

I was wondering what the maximum packet arrival time granularity is for Qt (On linux) using a normal timestamp, I can easily do 1ms. However if I was dealing with a raw socket descriptor, timing below this there is a ioctl() call I can do to get a lower resolution for the packet arrival time. I'm not sure how well this would play with Qt's internals though. For now my packet is UDP,  but if needed, I'd like to be able to extend it to TCP. I'm trying to time sync 2-3 systems on the same LAN. Ultimately, actual time of day isn't needed, just the amount of time of travel between the hosts. On a RaspberyPi zero

Has anyone done anything like this? Any tips? Many thanks in advance.