misc/179540: dhclient does not apply changes to lease if IP unchanged

[Allen]

>Number:         179540
>Category:       misc
>Synopsis:       dhclient does not apply changes to lease if IP unchanged
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jun 13 18:40:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Allen
>Release:        8.2
>Organization:
>Environment:
FreeBSD mail.localdomain 8.2-STABLE FreeBSD 8.2-STABLE #0: Fri Oct 14 00:11:10 UTC 2011     root at freebsd-82-64.master.concord.internal:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
Upon lease renewal, if the IP address of the lease has not changed, other lease options that have changed are apparently ignored.  Only tested with a changing subnet mask but suspect other fields behave similarly.

A pfSense DHCP server serving multiple clients exhibited this behavior when the IP address of the pfSense LAN (and thus the DHCP pool) was changed from 192.168.28.1/22 to 192.168.28.1/20.

The new netmask (0xfffff000 / 255.255.240.0) is present in the client lease file, but ifconfig shows the old netmask (0xfffffc00 / 255.255.252.0) is still configured on the interface.

>How-To-Repeat:
1. Create a subnet with dhcp, e.g. 10.0.0.0/24 with 10.0.0.(200-250) as the dhcp pool.

2. Acquire a lease from this pool on a FreeBSD DHCP client.

3. Change the netmask of the DHCP server and pool to something wider, e.g. 10.0.0.0/22.

4. Await DHCP renewal on client.  The lease file will reflect the new subnet mask, but the new mask is not applied to the interface.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: