DSCP issue in timesync #476
Description
systemd version the issue has been seen with
255
Used distribution
Ubuntu 24.04
Linux kernel version used
5.15.167.4-microsoft-standard-WSL2
CPU architectures issue was seen on
None
Component
No response
Expected behaviour you didn't see
No response
Unexpected behaviour you saw
On ubuntu22.04, systemd-timesyncd sync to NTP server on the internet. (Looks using systemd-v249.11)
But, ubuntu24.04, systemd-timesyncd don't sync to NTP server on the internet. (Looks using systemd-v255.4)
Same thing on ubuntu22.04 happens on PiOS bookworm on Raspberry Pi. (Looks using systemd-252.36)
Wireshark show me that, in case of IPTOS_DSCP_EF, the case of ubuntu24.04, and PiOS bookworm, response packet from the NTP server on the internet never comes back.
On the other hand, in case of IPTOS_LOW, the case of ubuntu22.04, response packets from the NTP server on the internet comes back, and can be sync to the NTP server on the internet.
I tried several NTP servers, like, time.windows.com, time.cloudflare.com, and ntp.nict.jp, but same result as above.
Also tried with IPv4 and IPv6 address of the NTP servers, but resulted the same.
Using ntpd instead, ntpd can change DSCP to 0 in ntp.conf, which made me to sync to NTP server on the internet, even on ubuntu24.04 and PiOS bookworm.
My ISP seems dropping packet with IPTOS_DSCP_EF.
There seems no way to change DSCP on timesyncd, looks hard coded, so I had to give up using systemd-timesyncd.
chrony can also change DSCP value in the configuration file, chrony.conf.
Is there any chance that systemd-timesyncd to be configurable about DSCP value, like ntpd, chrony?
If DSCP can be configurable to 0, I can come back to systemd-timesyncd again.
Hoping to hear good news.
Thanks reading.
Steps to reproduce the problem
No response