Description of problem:

When the DHCP lease is renewed and there's a change in the NTP server, the
dispatcher scripts are not run and therefore chrony is not updated
to use the new NTP server.

The only workaround is to bring down/up the connection via nmcli. After
the connection is brought back up, chrony shows the updated NTP server.

Version-Release number of selected component (if applicable):

This has been tested on NetworkManager-1.36.0-7.el8_6 and
NetworkManager-1.40.0-5.el8_7, both behave as described above.

When testing the same on NetworkManager-1.32.10-5.el8_5, a "dhcp4-change"
event is triggered when the NTP-server option changes, the dispatcher
scripts are run, and chrony is updated successfuly with the new NTP server.

Looks like a problem introduced in RHEL8.6 after NM was updated from 1.32 to 1.36

How reproducible:

Always

Steps to Reproduce:

• create a pair of veth, add a new ns for the peer, configure an IP on the
  peer, and build a DHCP NM connection on the client

$ sudo ip link add dhcpifc type veth peer name dhcpifd
$ sudo ip netns add dhcps
$ sudo ip link set dhcpifd netns dhcps

$ sudo nmcli con add con-name dhcpifc type ethernet \
ifname dhcpifc ipv6.method disabled ipv4.method auto \
ipv4.ignore-auto-routes yes

$ sudo ip netns exec dhcps ip add add 10.9.9.1/24 dev dhcpifd
$ sudo ip netns exec dhcps ip link set dhcpifd up

• Run a simple dnsmasq dhcp server with a short lease time on the peer interface:

$ sudo ip netns exec dhcps dnsmasq d -C <<EOF
interface=dhcpifd
port=0
dhcp-range=10.9.9.100,10.9.9.110,255.255.255.0,60s
dhcp-option=option:ntp-server,10.9.9.12
EOF

• Bring the DHCP connection up. Wait until the DHCP settings are configured

$ sudo nmcli con dhcpifc up

• Check the chrony sources. The NTP server provided initially is configured

$ sudo chronyc -n sources | grep 10.9
^? 10.9.9.12 0 7 0 - +0ns[ +0ns] +/- 0ns

• Before the DHCP is renewed, modify the NTP server option and re-run dnsmasq

$ sudo ip netns exec dhcps dnsmasq d -C <<EOF
interface=dhcpifd
port=0
dhcp-range=10.9.9.100,10.9.9.110,255.255.255.0,60s
dhcp-option=option:ntp-server,10.9.9.10
EOF

• After the renewal, re-check the chrony sources. The new NTP server has not been configured

$ sudo chronyc -n sources | grep 10.9
^? 10.9.9.12 0 8 0 - +0ns[ +0ns] +/- 0ns

Actual results:

Chrony is not updated to use new NTP server provided

Expected results:

Chrony should be updated to use new NTP server provided

Additional info:

This is easily reproducible on RHEL8.6+ and RHEL9 using the mentioned NetworkManager versions.
If there's log/trace required please let me know and I'll upload it.