[chrony-dev] Re: chrony 3.4+ on multihomed machines forces wrong interface

[Arkadiusz Miśkiewicz <arekm@xxxxxxxx>]

On 28/04/2020 11:43, Arkadiusz Miśkiewicz wrote:

> Now why kernel discards such sendmsg() without immediate error - no idea.

This is about similar problem and explains things

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=781732


Anyway forcing interface index looks to be wrong (bypasses routing
table) solution to problem which that commit tried to fix.

> 
> 5fc7674e366fa1bfda162bdaba57243cff0a55a7 is the first bad commit
> commit 5fc7674e366fa1bfda162bdaba57243cff0a55a7
> Author: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
> Date:   Wed Aug 29 10:56:14 2018 +0200
> 
>     ntp: set interface index in IP*_PKTINFO when responding
> 
>     When a server with multiple interfaces in the same network is sending a
>     response, setting the ipi_spec_dst/ipi6_addr field of the IP*_PKTINFO
>     control message selects the source address, but not necessarily the
>     interface. The packet has the expected source address, but it may be
>     sent by an interface that doesn't have the address.
> 
>     Set the ipi_ifindex/ipi6_ifindex field to respond on the same interface
>     as the request was received from to avoid asymmetries in delay and
>     timestamping.
> 
>  ntp_io.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 


-- 
Arkadiusz Miśkiewicz, arekm / ( maven.pl | pld-linux.org )

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