From ed3747d52ae5cdea8ed0af42046c03a50065d8c2 Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Tue, 6 May 2014 20:42:21 +0200
Subject: [PATCH] ISC dhcpd reader: Don't add duplicate entries.

---
 src/isc.c | 48 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 13 deletions(-)

diff --git a/src/isc.c b/src/isc.c
index c1de786..5106442 100644
--- a/src/isc.c
+++ b/src/isc.c
@@ -32,11 +32,14 @@ struct isc_dhcp_lease {
 	struct isc_dhcp_lease* next;
 };
 
-static struct isc_dhcp_lease* dhcp_lease_new() {
+static struct isc_dhcp_lease* dhcp_lease_new(const char* hostname) {
 	struct isc_dhcp_lease* lease = whine_malloc(sizeof(*lease));
 
-	lease->name = NULL;
-	lease->fqdn = NULL;
+	lease->name = strdup(hostname);
+	if (daemon->domain_suffix) {
+		asprintf(&lease->fqdn, "%s.%s", hostname, daemon->domain_suffix);
+	}
+	lease->expires = 0;
 	lease->next = NULL;
 
 	return lease;
@@ -100,6 +103,19 @@ static time_t parse_lease_time(const char* token_date, const char* token_time) {
 	return time;
 }
 
+static struct isc_dhcp_lease* find_lease(const char* hostname, struct isc_dhcp_lease* leases) {
+	struct isc_dhcp_lease* lease = leases;
+
+	while (lease) {
+		if (strcmp(hostname, lease->name) == 0) {
+			return lease;
+		}
+		lease = lease->next;
+	}
+
+	return NULL;
+}
+
 static off_t lease_file_size = (off_t)0;
 static ino_t lease_file_inode = (ino_t)0;
 
@@ -185,20 +201,26 @@ void load_dhcp(time_t now) {
 						*dot = 0;
 					}
 
-					struct isc_dhcp_lease* lease = dhcp_lease_new();
-					lease->name = strdup(hostname);
-					lease->addr = host_address;
-					lease->expires = time_ends;
-					lease->next = NULL;
+					// Search for an existing lease in the list
+					// with the given host name and update the data
+					// if needed.
+					struct isc_dhcp_lease* lease = find_lease(hostname, leases);
 
-					if (daemon->domain_suffix) {
-						asprintf(&lease->fqdn, "%s.%s", hostname, daemon->domain_suffix);
-					}
+					// If no lease already exists, we create a new one
+					// and append it to the list.
+					if (!lease) {
+						lease = dhcp_lease_new(hostname);
 
-					if (leases)
 						lease->next = leases;
+						leases = lease;
+					}
 
-					leases = lease;
+					// Only update more recent leases.
+					if (lease->expires > time_ends)
+						continue;
+
+					lease->addr = host_address;
+					lease->expires = time_ends;
 				}
 			}
 		}
-- 
2.39.2