On Tue, Mar 21, 2023 at 10:43 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > Vincent Li <vincent.mc.li@xxxxxxxxx> writes: > > > On Mon, Mar 20, 2023 at 2:57 PM Vincent Li <vincent.mc.li@xxxxxxxxx> wrote: > >> > >> On Mon, Mar 20, 2023 at 10:15 AM Jesper Dangaard Brouer > >> <jbrouer@xxxxxxxxxx> wrote: > >> > > >> > > >> > On 20/03/2023 16.33, Vincent Li wrote: > >> > > > >> > > if I have a XDP based firewall to block ip access based on system > >> > > localtime/wall time, is it still impossible like what mentioned here > >> > > https://github.com/xdp-project/xdp-tutorial/issues/204#issuecomment-819419800? > >> > > If so, is there any way to workaround this? > >> > > >> > You could use the BPF-helper named: bpf_ktime_get_tai_ns() > >> > > >> > See man clock_gettime(2). It is the same as CLOCK_TAI, which is > >> > (currently) offset with 37 sec to CLOCK_REALTIME which is wall-clock. > >> > > > > > sorry a follow-up question, the bpf_ktime_get_tai_ns will return time > > as nano seconds, right? > > I do not need the nanoseconds precision, I only need HH:MM like hours > > and minutes of the day, for example 10:30 = 10 * 60 + 30 is good > > enough, > > any trick get that from bpf_ktime_get_tai_ns() > > Populate the time at latest midnight from userspace when installing the > program and calculate offsets from that? > Yes, I populated the map with 10 * 60 + 30 from user space, the remaining question is how to get minutes of the day from bpf_ktime_get_tai_ns(), I guess that is what you mean to calculate the offsets from kernel bpf code?
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