[lwip-devel] [patch #9612] Bugfix: sntp server IP address not always saved after DNS lookup

[Tom Ferrin]

Follow-up Comment #4, patch #9612 (project lwip):

Having access to the IP address(es) currently being used by the SNTP app is
all about monitoring SNTP performance and is especially useful when multiple
servers are configured. The DNS address cache doesn't come into play at all,
except with respect to this bug fix. If the NTP server's address was in the
cache, then the SNTP app correctly noted the address. If it was not in the
cache, then the addr saved by SNTP was 0.0.0.0 and thus is not useful for
monitoring SNTP performance differences among servers. SNTP always uses the IP
address returned by the DNS server on each new NTP request, so the local copy
is not relied on for proper operation of the protocol. Note that the default
interval between time synchronization requests (SNTP_UPDATE_DELAY) is usually
60 minutes or more, so in an active network environment it is unlikely that
the NTP server address will still be in the DNS cache and thus, prior to this
bugfix, the address saved by SNTP was always 0.0.0.0. This bug fix only
ensures that a valid address is saved by SNTP regardless of whether or not it
was cached by the DNS server or had to be resolved through a DNS transaction. 
 

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