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analyse: critical bug in the counting code

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The problem is, that you simply count all lease occurrences in
dhcpd.leases, but only the last ones for each ip address are
valid.  The lease file is more like a logfile of what has been
done, than a real database.  To fix the counting issue, I'm using
a single hash (from uthash.h [1]) for the counting.  This way
only the last lease entry for each IP gets into my counting
structure.

When you remove the duplicates in prepare_data(), you don't have
the information anymore, if the active lease entry or the free
lease entry came last.  Simply deleting each ip from the touches
array, that is already in the leases array, gives you a big
chance to count wrong.  Another way of fixing this would be to
not only store the ips in your arrays, but a structure containing
the ip and a global lease entry counter.  Then you could delete
all entries except for the latest.

[1] http://uthash.sourceforge.net/

Reported-by: Huangy
Signed-off-by: Enno Grper <groepeen@cms.hu-berlin.de>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
This commit is contained in:
Enno Grper 2012-05-02 14:01:07 +02:00 • committed by Sami Kerola
parent 3ef5d6c07f
commit ae7747db87
10 changed files with 166 additions and 150 deletions
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32
TODO
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@ -1,32 +1,10 @@
### Bugs
> 1. from huangyu: china,fujian province,fuzhou
>
> according to my observation, every lease,for example,ip
> 192.168.0.123 perhaps appears many times in dhcpd.leases,but
> only the last time's state is the final valid state of this ip
> 192.168.0.123.
>
> No matter it appears how many times in dhcpd.leases,and no
> matter it has how many different state in dhcpd.leases. no
> matter it had been assigned to how many different mac-address.
> As long as it's last appearance's binding state is free in
> dhcpd.leases,then ,it's free,in other word,it's not active.
>
> and i notice that if a active lease time expired,dhcpd daemon
> will set this lease's binding state from active to free
> directly,without released state in this period.
>
> in other words, when a lease's binding state "active" follow by
> "free",not follow by "released";dhcpd-pools still think it's
> active.
>
> and another bug maybe is:
>
> i found dhcpd-pools didn't consider if the active lease's ends
> time is passed so it would still think the lease is active even
> if dhcpd daemon is stopped for a long time,the leases marked by
> "active" state in lease_file has expired in fact.
Reported-by: Huangyu: I found dhcpd-pools didn't consider if the
active lease's ends time is passed so it would still think the
lease is active even if dhcpd daemon is stopped for a long time,
the leases marked by "active" state in lease_file has expired in
fact.
### Feature requests