[Dnsmasq-discuss] Dnsmasq not resolving addresses for an hour

[John Knight]

Hi,

I think I may know what the issue is... it appears that the time may be changed by ntp in my failure scenario as suggested by the URLs referencing ntp in the dnsmasq.log file.  There are numerous references to difftime in dnsmasq code.  One of which acknowledges potential problem if the clock goes backwards... and is handled by comparing last_resolv >1.0 and < -1.0 to accommodate such a possibility.  However, in function poll_resolv(), the difftime() call checks for > 0.0, assuming the modification time of the file is greater than the last_change time.  If the time had changed on the router, then its possible that the modification time of the /etc/resolv.conf could be less than that of the last_change.  I think this needs to be a check for != 0.  If the time is changed negatively, then the existing code will not work properly me thinks.  Its imperative that latest gets set in order for the reload_servers() code to run... and if the time is not right, then the reload_servers() won't get called.  This specific code (poll_resolv) hasn't changed, and if I am right, it is also broken in 2.76.

What do you think?  I am going to make the change locally and re-test and see if I can make it fail again.  Unfortunately, it doesn't always fail, but I have reproduced it twice now, hopefully it will happen again if my fix is not right.

Best Regards,

John Knight

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