[lwip-devel] [bug #51571] IP address is used after DHCP lease is expired

[Matthias Hofmann]

URL:
  <http://savannah.nongnu.org/bugs/?51571>

                 Summary: IP address is used after DHCP lease is expired
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: mhofmann
            Submitted on: Tue 25 Jul 2017 12:17:42 PM UTC
                Category: DHCP
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.0.0

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Details:

When testing DHCP of the lwip 2.0.0 release, I was surprised that the IP
address is still used after the lease time had expired.

I expected that the IP configuration is reset after the lease time is
expired.

For testing purpose I configured the DHCP server with a maximum lease time of
300 seconds.
I connected a eval board running lwip and wait until an IP address is
assigned.
Than I stop the DHCP server and wait until the lease time have expired and 2
DHCP Request were sent (1 unicast, 1 broadcast).

After this I ping the eval board with the expired IP address.


After searching in sources it looks like the root cause is that in the DHCP
state REBINDING, the IP address is not treated as "DHCP supplied".




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