[master] Added configuration parameter, ping-cltt-secs (v4 operation only)

Merges in rt36283.

RELNOTES

@@ -88,7 +88,13 @@ Consortium.  This product includes cryptographic software written
 by Eric Young (eay@cryptsoft.com).
 
 		Changes since 4.4.1 (New Features)
-- none
+
+- A new configuration parameter, ping-cltt-secs (v4 operation only), has
+  been added to allow the user to specify the number of seconds that must
+  elapse since CLTT before a ping check is conducted.  Prior to this, the
+  value was hard coded at 60 seconds. Please see the server man pages for
+  a more detailed discussion.
+  [ISC-Bugs #36283]
 
 		Changes since 4.4.1 (Bug Fixes)
 
@@ -100,7 +106,6 @@ by Eric Young (eay@cryptsoft.com).
 
 		Changes since 4.4.0 (New Features)
 - none
-
 		Changes since 4.4.0 (Bug Fixes)
 
 - A delayed-ack value of 0 (the default), now correctly disables the delayed

includes/dhcpd.h

@@ -815,11 +815,17 @@ struct lease_state {
 #define SV_RELEASE_ON_ROAM		95
 #define SV_LOCAL_ADDRESS6		96
 #define SV_BIND_LOCAL_ADDRESS6		97
+#define SV_PING_CLTT_SECS		98
 
 #if !defined (DEFAULT_PING_TIMEOUT)
 # define DEFAULT_PING_TIMEOUT 1
 #endif
 
+#if !defined (DEFAULT_PING_CLTT_SECS)
+# define DEFAULT_PING_CLTT_SECS 60  /* in seconds */
+#endif
+
+
 #if !defined (DEFAULT_DELAYED_ACK)
 # define DEFAULT_DELAYED_ACK 0  /* default 0 disables delayed acking */
 #endif

server/dhcp.c

@@ -33,9 +33,15 @@
 
 static void maybe_return_agent_options(struct packet *packet,
 				       struct option_state *options);
+
 static int reuse_lease (struct packet* packet, struct lease* new_lease,
 			struct lease* lease, struct lease_state *state,
-			int offer);
+			int offer, int* same_client);
+
+static int do_ping_check(struct packet* packet, struct lease_state* state,
+                         struct lease* lease, TIME original_cltt,
+			 int same_client);
+
 #if defined(DHCPv6) && defined(DHCP4o6)
 static int locate_network6(struct packet *packet);
 #endif
@@ -2180,8 +2186,7 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
 	TIME default_lease_time;
 	struct option_cache *oc;
 	isc_result_t result;
-	TIME ping_timeout;
-	TIME lease_cltt;
+	TIME original_cltt;
 	struct in_addr from;
 	TIME remaining_time;
 	struct iaddr cip;
@@ -2190,18 +2195,18 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
 	isc_boolean_t enqueue = ISC_FALSE;
 #endif
 	int use_old_lease = 0;
+	int same_client = 0;
 
 	unsigned i, j;
 	int s1;
 	int ignorep;
-	struct timeval tv;
 
 	/* If we're already acking this lease, don't do it again. */
 	if (lease -> state)
 		return;
 
 	/* Save original cltt for comparison later. */
-	lease_cltt = lease->cltt;
+	original_cltt = lease->cltt;
 
 	/* If the lease carries a host record, remember it. */
 	if (hp)
@@ -3194,7 +3199,8 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
 
 		/* If dhcp-cache-threshold is enabled, see if "lease" can
 		 * be reused. */
-		use_old_lease = reuse_lease(packet, lt, lease, state, offer);
+		use_old_lease = reuse_lease(packet, lt, lease, state, offer,
+					    &same_client);
 		if (use_old_lease == 1) {
 			commit = 0;
 		}
@@ -3560,52 +3566,10 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
 	/* Hang the packet off the lease state. */
 	packet_reference (&lease -> state -> packet, packet, MDL);
 
-	/* If this is a DHCPOFFER, ping the lease address before actually
-	   sending the offer. */
-	if (offer == DHCPOFFER && !(lease -> flags & STATIC_LEASE) &&
-	    (((cur_time - lease_cltt) > 60) ||
-             (lease->binding_state == FTS_ABANDONED)) &&
-	    (!(oc = lookup_option (&server_universe, state -> options,
-				   SV_PING_CHECKS)) ||
-	     evaluate_boolean_option_cache (&ignorep, packet, lease,
-					    (struct client_state *)0,
-					    packet -> options,
-					    state -> options,
-					    &lease -> scope, oc, MDL))) {
-		icmp_echorequest (&lease -> ip_addr);
-
-		/* Determine whether to use configured or default ping timeout.
-		 */
-		if ((oc = lookup_option (&server_universe, state -> options,
-						SV_PING_TIMEOUT)) &&
-		    evaluate_option_cache (&d1, packet, lease, NULL,
-						packet -> options,
-						state -> options,
-						&lease -> scope, oc, MDL)) {
-			if (d1.len == sizeof (u_int32_t))
-				ping_timeout = getULong (d1.data);
-			else
-				ping_timeout = DEFAULT_PING_TIMEOUT;
-
-			data_string_forget (&d1, MDL);
-		} else
-			ping_timeout = DEFAULT_PING_TIMEOUT;
-
-#ifdef DEBUG
-		log_debug ("Ping timeout: %ld", (long)ping_timeout);
-#endif
-
-		/*
-		 * Set a timeout for 'ping-timeout' seconds from NOW, including
-		 * current microseconds.  As ping-timeout defaults to 1, the
-		 * exclusion of current microseconds causes a value somewhere
-		 * /between/ zero and one.
-		 */
-		tv.tv_sec = cur_tv.tv_sec + ping_timeout;
-		tv.tv_usec = cur_tv.tv_usec;
-		add_timeout (&tv, lease_ping_timeout, lease,
-			     (tvref_t)lease_reference,
-			     (tvunref_t)lease_dereference);
+	/* If this is a DHCPOFFER, send a ping (if appropriate) to the
+	 * lease address before actually we send the offer. */
+	if ((offer == DHCPOFFER) &&
+	    do_ping_check(packet, state, lease, original_cltt, same_client)) {
 		++outstanding_pings;
 	} else {
   		lease->cltt = cur_time;
@@ -3618,6 +3582,118 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
 	}
 }
 
+/*
+ * \brief Sends a ping to the lease ip_addr when appropriate
+ *
+ * A ping will be sent if all of the following are true:
+ *
+ * 1. Ping checks are enabled
+ * 2. The lease is neither active nor static
+ * 3. Any of the following is true:
+ *    a. The lease state is ABANDONED
+ *    b. This is the first offer of this lease (CLTT = 0)
+ *    c. The lease is being offered to a client other than its previous
+ *    owner
+ *    d. The lease is being offered to its previous owner and more than
+ *    cltt-secs have elapsed since CLTT of the original lease.
+ *
+ * \param packet inbound packet received from the client
+ * \param state lease options state
+ * \param lease lease to be offered (if one)
+ * \param original_cltt CLTT of the original lease
+ * \param same_client flag indicating if the client to be offered the
+ * lease is its previous owner
+ * \return Returns 1 if ping has been sent, 0 otherwise
+ */
+int do_ping_check(struct packet* packet, struct lease_state* state,
+		  struct lease* lease, TIME original_cltt,
+		  int same_client) {
+	TIME ping_timeout = DEFAULT_PING_TIMEOUT;
+	struct option_cache *oc = NULL;
+	struct data_string ds;
+	struct timeval tv;
+	int ignorep;
+
+	// Don't go any further if lease is active or static.
+	if (lease->binding_state == FTS_ACTIVE || lease->flags & STATIC_LEASE) {
+		return (0);
+	}
+
+	// If pings aren't enabled, punt.
+	oc = lookup_option (&server_universe, state -> options, SV_PING_CHECKS);
+	if (oc &&
+	    !(evaluate_boolean_option_cache (&ignorep, packet, lease,
+					   0, packet->options, state->options,
+					    &lease->scope, oc, MDL))) {
+		return (0);
+	}
+
+	// If it's not the first time for the same client and not an
+	// abandoned lease, we need to check the cltt threshold
+	if (same_client && original_cltt &&
+	    lease->binding_state != FTS_ABANDONED) {
+		TIME cltt_secs = DEFAULT_PING_CLTT_SECS;
+		memset(&ds, 0, sizeof(ds));
+		oc = lookup_option (&server_universe, state->options,
+				    SV_PING_CLTT_SECS);
+		if (oc &&
+		    (evaluate_option_cache (&ds, packet, lease, 0,
+					    packet->options, state->options,
+					    &lease->scope, oc, MDL))) {
+			if (ds.len == sizeof (u_int32_t)) {
+				cltt_secs = getULong (ds.data);
+			}
+
+			data_string_forget (&ds, MDL);
+		}
+
+		// Punt if it is too soon.
+		if (cur_time - original_cltt < cltt_secs) {
+			return (0);
+		}
+	}
+
+	// Send the ping.
+	icmp_echorequest (&lease->ip_addr);
+
+	/* Determine whether to use configured or default ping timeout. */
+	memset(&ds, 0, sizeof(ds));
+	oc = lookup_option (&server_universe, state->options, SV_PING_TIMEOUT);
+	if (oc &&
+	    (evaluate_option_cache (&ds, packet, lease, 0,
+				    packet->options, state->options,
+				    &lease->scope, oc, MDL))) {
+		if (ds.len == sizeof (u_int32_t)) {
+			ping_timeout = getULong (ds.data);
+		}
+
+		data_string_forget (&ds, MDL);
+	}
+
+#ifdef DEBUG
+	log_debug ("Pinging:%s, state: %d, same client? %s, "
+		   " orig_cltt %s, elasped: %ld" ,
+                   piaddr(lease->ip_addr),
+		   lease->binding_state,
+		   (same_client ? "y" : "n"),
+		   (original_cltt ? print_time(original_cltt) : "0"),
+		   (original_cltt ? (long)(cur_time - original_cltt) : 0));
+#endif
+
+	/*
+	 * Set a timeout for 'ping-timeout' seconds from NOW, including
+	 * current microseconds.  As ping-timeout defaults to 1, the
+	 * exclusion of current microseconds causes a value somewhere
+	 * /between/ zero and one.
+	*/
+	tv.tv_sec = cur_tv.tv_sec + ping_timeout;
+	tv.tv_usec = cur_tv.tv_usec;
+	add_timeout (&tv, lease_ping_timeout, lease, (tvref_t)lease_reference,
+		     (tvunref_t)lease_dereference);
+	return (1);
+}
+
+
 #if defined(DELAYED_ACK)
 
 /*
@@ -5628,7 +5704,10 @@ void use_host_decl_name(struct packet* packet,
  * \param packet inbound packet received from the client
  * \param new_lease candidate new lease to associate with the client
  * \param lease current lease associated with the client
- * \param options option state to search and update
+ * \param lease_state lease state to search and update
+ * \param offer type of DHCP response we're building
+ * \param[out] same_client pointer to int, that will be set to 1 if
+ * the two leases refer to the same client, 0 if not. Must NOT be null.
  *
  * \return 1 if the lease can be reused.
  */
@@ -5637,7 +5716,8 @@ reuse_lease (struct packet* packet,
 	     struct lease* new_lease,
 	     struct lease* lease,
 	     struct lease_state *state,
-	     int offer) {
+	     int offer,
+	     int *same_client) {
 	int reusable = 0;
 
 	/* To even consider reuse all of the following must be true:
@@ -5647,16 +5727,20 @@ reuse_lease (struct packet* packet,
 	 * 4 - the host declaration hasn't changed
 	 * 5 - the uid hasn't changed
 	 * 6 - the hardware address hasn't changed */
-	if ((lease->cannot_reuse == 0) &&
-	    (lease->binding_state == FTS_ACTIVE) &&
-	    (new_lease->ddns_cb == NULL) &&
-	    (lease->host == new_lease->host) &&
+
+	/* Check client equality separately so we can pass the result out. */
+	*same_client =
+	    (((lease->host == new_lease->host) &&
              (lease->uid_len == new_lease->uid_len) &&
-	    (memcmp(lease->uid, new_lease->uid, lease->uid_len) == 0) &&
+             (memcmp(lease->uid, new_lease->uid, new_lease->uid_len) == 0) &&
              (lease->hardware_addr.hlen == new_lease->hardware_addr.hlen) &&
              (memcmp(&lease->hardware_addr.hbuf[0],
                      &new_lease->hardware_addr.hbuf[0],
-		    lease->hardware_addr.hlen) == 0)) {
+                     lease->hardware_addr.hlen) == 0)) ? 1 : 0);
+
+	if ((lease->cannot_reuse == 0) &&
+	    (lease->binding_state == FTS_ACTIVE) &&
+	    (new_lease->ddns_cb == NULL) && *same_client) {
 		int thresh = DEFAULT_CACHE_THRESHOLD;
 		struct option_cache* oc = NULL;
 		struct data_string d1;

server/dhcpd.conf.5

@@ -3027,6 +3027,36 @@ checking - if its value is false, no ping check is done.
 .RE
 .PP
 The
+.I ping-cltt-secs
+statement
+.RS 0.25i
+.PP
+.B ping-cltt-secs
+.I seconds\fR\fB;\fR
+.PP
+The server will conduct a ping check if all the following conditions are true:
+.PP
+1. Ping checking is enabled.
+.PP
+2. The server is responding to a DISCOVER.
+.PP
+3. The lease to be offered is neither static nor active (i.e. still a valid
+lease).
+.PP
+4. And any of the following are true:
+    a. This will be the first offer of this lease (CLTT is 0).
+    b. The lease is being offered to a client other than its previous owner
+    c. The lease is being offered to its previous owner and more than
+    \fBping-cltt-secs\fR have elapsed since CLTT of the original lease.
+    d. The lease was abandoned and the server is attempting to reclaim it.
+
+.PP
+The \fBping-cltt-secs\fR statement allows the user to specify the amount of
+time that must elaspe after CLTT before a ping check will be conducted.
+The default value is sixty seconds.
+.RE
+.PP
+The
 .I ping-timeout
 statement
 .RS 0.25i

server/stables.c

@@ -291,6 +291,7 @@ static struct option server_options[] = {
 	{ "release-on-roam", "f",	&server_universe,  SV_RELEASE_ON_ROAM, 1 },
 	{ "local-address6", "6",	&server_universe,  SV_LOCAL_ADDRESS6, 1 },
 	{ "bind-local-address6", "f",	&server_universe,  SV_BIND_LOCAL_ADDRESS6, 1 },
+	{ "ping-cltt-secs", "T",	&server_universe,  SV_PING_CLTT_SECS, 1 },
 	{ NULL, NULL, NULL, 0, 0 }
 };