[Bug 13776] udhcpc allows short lease to expire

bugzilla at busybox.net bugzilla at busybox.net
Fri Apr 30 13:59:57 UTC 2021


https://bugs.busybox.net/show_bug.cgi?id=13776

--- Comment #4 from Paul <sinbad_4273 at yahoo.com> ---
You are exactly right. The ISP's modem has a coaxial cable coming in. It also
has a single ethernet port going out to the wireless router's WAN port. I have
installed dd-wrt on the wireless router that I bought/own.

After 61s (half of the 122s "assumed" lease time) udhcpc will try to renew but
this fails since the actual lease (60s) is already expired. There are timeouts,
delays, repeated renew reattempts with progressively shorter timeouts until
udhcpc eventually decides that the lease is lost. After a longer than normal
delay, this usually ends up with the internet working but maybe once every week
or two, manual dhcp release/renew or even router reboot are required. The modem
is turned off nightly for family reasons but the router is always on.

There also could be a bug in dd-wrt but the long delays and dd-wrt displaying a
remaining lease time of zero during all of the failed renew attempts, is a
result of this 122s lease assumption. Note that udhcpc assumes 122s but
correctly reports 60s to dd-wrt.

I'll try to get some actual udhcpc logs.

What is special about 60s timeouts? Why is udhcpc selecting (60s + 1s )*2 ?

Thanks for the help/explanations.

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