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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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20
src/dhcpd-pools.h
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@ -40,6 +40,7 @@
#include <arpa/inet.h>
#include <stddef.h>
#include <stdio.h>
#include <uthash.h>
/* Feature test switches */
#define _POSIX_SOURCE 1
@ -122,6 +123,16 @@ struct macaddr_t {
char *ip;
struct macaddr_t *next;
};
enum ltype {
ACTIVE,
FREE,
BACKUP
};
struct leases_t {
uint32_t ip; /* ip as key */
enum ltype type;
UT_hash_handle hh;
};
/* Global variables */
struct configuration_t config;
@ -133,11 +144,9 @@ struct shared_network_t *shared_networks;
unsigned int num_shared_networks;
struct range_t *ranges;
unsigned int num_ranges;
uint32_t *leases;
struct leases_t *leases;
unsigned long int num_leases;
uint32_t *touches;
unsigned long int num_touches;
uint32_t *backups;
unsigned long int num_backups;
struct macaddr_t *macaddr;
@ -200,5 +209,10 @@ int output_xml(void);
int output_csv(void);
/* Memory release, file closing etc */
void clean_up(void);
/* Hash functions */
void add_lease(int ip, enum ltype type);
struct leases_t * find_lease(int ip);
void delete_lease(struct leases_t * lease);
void delete_all_leases();
#endif /* DHCPD_POOLS_H */