DNS issues on NTP client

During NTP server querying through the `ntpclient.c`, different NTP server domain names (e.g., 0.uk.pool.ntp.org, 1.uk.pool.ntp.org) might resolve to the same set of IP addresses due to **DNS caching**. This can lead to **repeated queries to the same non-responsive IP addresses**, resulting in failures to obtain the correct time.

For example, in the following, there are some logs that I added to `ntpclient.c`, in order to understand why the NTP was failing:
```
[ 51.046000] [25] (Info) '0.pool.ntp.org' resolved to: 216.238.113.58
[ 51.046000] [25] (Info) ntpclient.c-447-gethostbyname for 0.pool.ntp.org OK
[ 51.046000] [25] (Info) ntpclient.c-480-Sending a NTP packet
[ 51.055000] [25] (Info) ntpclient.c-509-sendto ret: 68
[ 51.056000] [25] (Info) ntpclient.c-515-Recv a NTP packet
[ 56.055000] [25] (Info) ntpclient.c-521-recvfrom nbytes: -1
[ 56.056000] [25] (Info) '0.pool.ntp.org' resolved to: 216.238.113.58
[ 56.056000] [25] (Info) ntpclient.c-447-gethostbyname for 0.pool.ntp.org OK
[ 56.056000] [25] (Info) ntpclient.c-480-Sending a NTP packet
[ 56.063000] [25] (Info) ntpclient.c-509-sendto ret: 68
[ 56.063000] [25] (Info) ntpclient.c-515-Recv a NTP packet
[ 61.065000] [25] (Info) ntpclient.c-521-recvfrom nbytes: -1
[ 61.066000] [25] (Info) '0.pool.ntp.org' resolved to: 216.238.113.58
[ 61.066000] [25] (Info) ntpclient.c-447-gethostbyname for 0.pool.ntp.org OK
[ 61.066000] [25] (Info) ntpclient.c-480-Sending a NTP packet
[ 61.075000] [25] (Info) ntpclient.c-509-sendto ret: 68
[ 61.075000] [25] (Info) ntpclient.c-515-Recv a NTP packet
[ 66.075000] [25] (Info) ntpclient.c-521-recvfrom nbytes: -1
[ 66.076000] [25] (Info) '0.pool.ntp.org' resolved to: 216.238.113.58
[ 66.076000] [25] (Info) ntpclient.c-447-gethostbyname for 0.pool.ntp.org OK
[ 66.076000] [25] (Info) ntpclient.c-480-Sending a NTP packet
[ 66.085000] [25] (Info) ntpclient.c-509-sendto ret: 68
[ 66.085000] [25] (Info) ntpclient.c-515-Recv a NTP packet
[ 71.085000] [25] (Info) ntpclient.c-521-recvfrom nbytes: -1
[ 71.086000] [25] (Info) '0.pool.ntp.org' resolved to: 216.238.113.58
[ 71.086000] [25] (Info) ntpclient.c-447-gethostbyname for 0.pool.ntp.org OK
[ 71.086000] [25] (Info) ntpclient.c-480-Sending a NTP packet
[ 71.095000] [25] (Info) ntpclient.c-509-sendto ret: 68
[ 71.095000] [25] (Info) ntpclient.c-515-Recv a NTP packet
[ 76.095000] [25] (Info) ntpclient.c-521-recvfrom nbytes: -1
[ 76.095000] [25] (Info) ntpclient.c-563-ERROR: recvfrom() failed: 11
[ 76.095000] [25] (Info) ntpclient.c-589-The NTP client is terminating
```

To mitigate this issue, a possible option is to **flush the DNS cache after cycling through all configured NTP servers**, ensuring that subsequent DNS resolutions provide potentially new and responsive IP addresses, thereby increasing the likelihood of successful time synchronization. However, I cannot manipulate the DNS cache from the user space, unless I create an API for it.

Overall, do you have a workaround or a hack that I can use in order to solve this NTP issue? Or at least to force a new IP resolution for an NTP hostname after some failures?

Start by reading ntpclient.c around gethostbyname, the NTP query retry loop, and the configured-server cycle described in the logs. Determine whether the existing client can request a fresh resolution or whether a cache API is needed; done should be a documented, reproducible way to avoid repeatedly querying the same non-responsive address.

Written by the indexing model from the issue text.