Re: [PATCH] dhcp,dhcp6,icmp6,time: Convert timestamps to CLOCK_BOOTTIME

[Denis Kenzior <denkenz at gmail.com>]

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Hi Andrew,

On 5/17/22 19:35, Andrew Zaborowski wrote:
> The frame reception timestamps obtained for DHCPv4, DHCPv6 and ICMPv6
> frames from the kernel are based on CLOCK_REALTIME, there's no option to
> switch them to CLOCK_BOOTTIME, which we use across our retransmission and
> renew logic.  Add a time-private.h utility to convert the timestamps
> right where we read them from recvmsg() to produce CLOCK_BOOTTIME based
> times.  This isn't 100% bulletproof because the offset between the two
> clocks can vary between the time the frame was received by the kernel and
> the time we read the offset.  The probability is very low though and we
> have no better solution at this time other than fixing it in the kernel.
> Using CLOCK_REALTIME for frame reception timestamps seems to mainly
> create potential for problems in the common usages.
> 
> Fixes: c78ad1bb6d7e ("dhcp: Set lease expiry based on frame reception times")
> ---
>   ell/dhcp-transport.c  |  3 ++-
>   ell/dhcp6-transport.c |  5 +++--
>   ell/icmp6.c           |  2 +-
>   ell/time-private.h    |  1 +
>   ell/time.c            | 34 ++++++++++++++++++++++++++++++++++
>   6 files changed, 44 insertions(+), 6 deletions(-)
> 

Applied, thanks.

Regards,
-Denis