[lwip-devel] [bug #60043] DHCP - lwip 2.1.2 - Manage the very low value for lease time

[Vincent SELOSSE]

URL:
  <https://savannah.nongnu.org/bugs/?60043>

                 Summary: DHCP - lwip 2.1.2 - Manage the very low value for
lease time 
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: vincent_netatmo
            Submitted on: Thu 11 Feb 2021 04:35:57 PM UTC
                Category: DHCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: Other

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Details:

In RFC 2131, it was specify that 4.3. The minimum lease time restriction has
been removed.  

In fact if the lease time received = 60sec, the counter `tx_timeout` checked
in `dhcp_coarse_tmr()` will take the following value:  
* `t0_timeout` = 1 
* `t1_timeout` = 1 
* `t2_timeout` = 1 

In `dhcp_coarse_tmr()` the `if (dhcp->t0_timeout && (++dhcp->lease_used ==
dhcp->t0_timeout))` will be always true. `dhcp_renew()` and `dhcp_rebind()`
will be never called.  

My proposal is to change:
* `DHCP_COARSE_TIMER_SECS` = 1  
* Change `tx_timeout` variable type from 16bits -> 32bits 





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