[Bug 13776] udhcpc allows short lease to expire

bugzilla at busybox.net bugzilla at busybox.net
Fri Apr 30 08:58:02 UTC 2021


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

--- Comment #3 from Denys Vlasenko <vda.linux at googlemail.com> ---
(In reply to Paul from comment #2)
The modem is supplied by the ISP so I have no control over it. When the modem
boots up it immediately (within seconds) gives the router a private ipv4
address (192.168.x.x) with a 60 second lease.

Please clarify. Modem and router are two different devices? Modem is connected
to ISP, and router is connected to this modem? Or I misunderstand?

> Once the modem does get online it gives the router a publicly routable IPv4 address with a lease of at least an hour.
> With stock router firmware the handoff from the short leased private address to the long leased public address was fast and smooth. With dd-wrt (which uses busybox's udhcpc) the handoff is long, shaky and sometimes fails altogether.

Please describe how it happens when it fials altogether. Waiting an extra
minute should not cause a permanent failure, I need to know more to understand
why that happens. udhcpc log (with increased verbosity if necessary) should
show what's going on.

> I'm not a networking expert and don't even understand what the comment "udhcpc: ensure at least one unicast renew attempt" means when the change to 122s was introduced.

It means "avoid always renewing the lease using broadcasts".

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