1.. SPDX-License-Identifier: GPL-2.0
2
3===========
4IPvs-sysctl
5===========
6
7/proc/sys/net/ipv4/vs/* Variables:
8==================================
9
10am_droprate - INTEGER
11	default 10
12
13	It sets the always mode drop rate, which is used in the mode 3
14	of the drop_rate defense.
15
16amemthresh - INTEGER
17	default 1024
18
19	It sets the available memory threshold (in pages), which is
20	used in the automatic modes of defense. When there is no
21	enough available memory, the respective strategy will be
22	enabled and the variable is automatically set to 2, otherwise
23	the strategy is disabled and the variable is  set  to 1.
24
25backup_only - BOOLEAN
26	- 0 - disabled (default)
27	- not 0 - enabled
28
29	If set, disable the director function while the server is
30	in backup mode to avoid packet loops for DR/TUN methods.
31
32conn_reuse_mode - INTEGER
33	1 - default
34
35	Controls how ipvs will deal with connections that are detected
36	port reuse. It is a bitmap, with the values being:
37
38	0: disable any special handling on port reuse. The new
39	connection will be delivered to the same real server that was
40	servicing the previous connection. This will effectively
41	disable expire_nodest_conn.
42
43	bit 1: enable rescheduling of new connections when it is safe.
44	That is, whenever expire_nodest_conn and for TCP sockets, when
45	the connection is in TIME_WAIT state (which is only possible if
46	you use NAT mode).
47
48	bit 2: it is bit 1 plus, for TCP connections, when connections
49	are in FIN_WAIT state, as this is the last state seen by load
50	balancer in Direct Routing mode. This bit helps on adding new
51	real servers to a very busy cluster.
52
53conntrack - BOOLEAN
54	- 0 - disabled (default)
55	- not 0 - enabled
56
57	If set, maintain connection tracking entries for
58	connections handled by IPVS.
59
60	This should be enabled if connections handled by IPVS are to be
61	also handled by stateful firewall rules. That is, iptables rules
62	that make use of connection tracking.  It is a performance
63	optimisation to disable this setting otherwise.
64
65	Connections handled by the IPVS FTP application module
66	will have connection tracking entries regardless of this setting.
67
68	Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled.
69
70cache_bypass - BOOLEAN
71	- 0 - disabled (default)
72	- not 0 - enabled
73
74	If it is enabled, forward packets to the original destination
75	directly when no cache server is available and destination
76	address is not local (iph->daddr is RTN_UNICAST). It is mostly
77	used in transparent web cache cluster.
78
79debug_level - INTEGER
80	- 0          - transmission error messages (default)
81	- 1          - non-fatal error messages
82	- 2          - configuration
83	- 3          - destination trash
84	- 4          - drop entry
85	- 5          - service lookup
86	- 6          - scheduling
87	- 7          - connection new/expire, lookup and synchronization
88	- 8          - state transition
89	- 9          - binding destination, template checks and applications
90	- 10         - IPVS packet transmission
91	- 11         - IPVS packet handling (ip_vs_in/ip_vs_out)
92	- 12 or more - packet traversal
93
94	Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled.
95
96	Higher debugging levels include the messages for lower debugging
97	levels, so setting debug level 2, includes level 0, 1 and 2
98	messages. Thus, logging becomes more and more verbose the higher
99	the level.
100
101drop_entry - INTEGER
102	- 0  - disabled (default)
103
104	The drop_entry defense is to randomly drop entries in the
105	connection hash table, just in order to collect back some
106	memory for new connections. In the current code, the
107	drop_entry procedure can be activated every second, then it
108	randomly scans 1/32 of the whole and drops entries that are in
109	the SYN-RECV/SYNACK state, which should be effective against
110	syn-flooding attack.
111
112	The valid values of drop_entry are from 0 to 3, where 0 means
113	that this strategy is always disabled, 1 and 2 mean automatic
114	modes (when there is no enough available memory, the strategy
115	is enabled and the variable is automatically set to 2,
116	otherwise the strategy is disabled and the variable is set to
117	1), and 3 means that that the strategy is always enabled.
118
119drop_packet - INTEGER
120	- 0  - disabled (default)
121
122	The drop_packet defense is designed to drop 1/rate packets
123	before forwarding them to real servers. If the rate is 1, then
124	drop all the incoming packets.
125
126	The value definition is the same as that of the drop_entry. In
127	the automatic mode, the rate is determined by the follow
128	formula: rate = amemthresh / (amemthresh - available_memory)
129	when available memory is less than the available memory
130	threshold. When the mode 3 is set, the always mode drop rate
131	is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
132
133expire_nodest_conn - BOOLEAN
134	- 0 - disabled (default)
135	- not 0 - enabled
136
137	The default value is 0, the load balancer will silently drop
138	packets when its destination server is not available. It may
139	be useful, when user-space monitoring program deletes the
140	destination server (because of server overload or wrong
141	detection) and add back the server later, and the connections
142	to the server can continue.
143
144	If this feature is enabled, the load balancer will expire the
145	connection immediately when a packet arrives and its
146	destination server is not available, then the client program
147	will be notified that the connection is closed. This is
148	equivalent to the feature some people requires to flush
149	connections when its destination is not available.
150
151expire_quiescent_template - BOOLEAN
152	- 0 - disabled (default)
153	- not 0 - enabled
154
155	When set to a non-zero value, the load balancer will expire
156	persistent templates when the destination server is quiescent.
157	This may be useful, when a user makes a destination server
158	quiescent by setting its weight to 0 and it is desired that
159	subsequent otherwise persistent connections are sent to a
160	different destination server.  By default new persistent
161	connections are allowed to quiescent destination servers.
162
163	If this feature is enabled, the load balancer will expire the
164	persistence template if it is to be used to schedule a new
165	connection and the destination server is quiescent.
166
167ignore_tunneled - BOOLEAN
168	- 0 - disabled (default)
169	- not 0 - enabled
170
171	If set, ipvs will set the ipvs_property on all packets which are of
172	unrecognized protocols.  This prevents us from routing tunneled
173	protocols like ipip, which is useful to prevent rescheduling
174	packets that have been tunneled to the ipvs host (i.e. to prevent
175	ipvs routing loops when ipvs is also acting as a real server).
176
177nat_icmp_send - BOOLEAN
178	- 0 - disabled (default)
179	- not 0 - enabled
180
181	It controls sending icmp error messages (ICMP_DEST_UNREACH)
182	for VS/NAT when the load balancer receives packets from real
183	servers but the connection entries don't exist.
184
185pmtu_disc - BOOLEAN
186	- 0 - disabled
187	- not 0 - enabled (default)
188
189	By default, reject with FRAG_NEEDED all DF packets that exceed
190	the PMTU, irrespective of the forwarding method. For TUN method
191	the flag can be disabled to fragment such packets.
192
193secure_tcp - INTEGER
194	- 0  - disabled (default)
195
196	The secure_tcp defense is to use a more complicated TCP state
197	transition table. For VS/NAT, it also delays entering the
198	TCP ESTABLISHED state until the three way handshake is completed.
199
200	The value definition is the same as that of drop_entry and
201	drop_packet.
202
203sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period
204	default 3 50
205
206	It sets synchronization threshold, which is the minimum number
207	of incoming packets that a connection needs to receive before
208	the connection will be synchronized. A connection will be
209	synchronized, every time the number of its incoming packets
210	modulus sync_period equals the threshold. The range of the
211	threshold is from 0 to sync_period.
212
213	When sync_period and sync_refresh_period are 0, send sync only
214	for state changes or only once when pkts matches sync_threshold
215
216sync_refresh_period - UNSIGNED INTEGER
217	default 0
218
219	In seconds, difference in reported connection timer that triggers
220	new sync message. It can be used to avoid sync messages for the
221	specified period (or half of the connection timeout if it is lower)
222	if connection state is not changed since last sync.
223
224	This is useful for normal connections with high traffic to reduce
225	sync rate. Additionally, retry sync_retries times with period of
226	sync_refresh_period/8.
227
228sync_retries - INTEGER
229	default 0
230
231	Defines sync retries with period of sync_refresh_period/8. Useful
232	to protect against loss of sync messages. The range of the
233	sync_retries is from 0 to 3.
234
235sync_qlen_max - UNSIGNED LONG
236
237	Hard limit for queued sync messages that are not sent yet. It
238	defaults to 1/32 of the memory pages but actually represents
239	number of messages. It will protect us from allocating large
240	parts of memory when the sending rate is lower than the queuing
241	rate.
242
243sync_sock_size - INTEGER
244	default 0
245
246	Configuration of SNDBUF (master) or RCVBUF (slave) socket limit.
247	Default value is 0 (preserve system defaults).
248
249sync_ports - INTEGER
250	default 1
251
252	The number of threads that master and backup servers can use for
253	sync traffic. Every thread will use single UDP port, thread 0 will
254	use the default port 8848 while last thread will use port
255	8848+sync_ports-1.
256
257snat_reroute - BOOLEAN
258	- 0 - disabled
259	- not 0 - enabled (default)
260
261	If enabled, recalculate the route of SNATed packets from
262	realservers so that they are routed as if they originate from the
263	director. Otherwise they are routed as if they are forwarded by the
264	director.
265
266	If policy routing is in effect then it is possible that the route
267	of a packet originating from a director is routed differently to a
268	packet being forwarded by the director.
269
270	If policy routing is not in effect then the recalculated route will
271	always be the same as the original route so it is an optimisation
272	to disable snat_reroute and avoid the recalculation.
273
274sync_persist_mode - INTEGER
275	default 0
276
277	Controls the synchronisation of connections when using persistence
278
279	0: All types of connections are synchronised
280
281	1: Attempt to reduce the synchronisation traffic depending on
282	the connection type. For persistent services avoid synchronisation
283	for normal connections, do it only for persistence templates.
284	In such case, for TCP and SCTP it may need enabling sloppy_tcp and
285	sloppy_sctp flags on backup servers. For non-persistent services
286	such optimization is not applied, mode 0 is assumed.
287
288sync_version - INTEGER
289	default 1
290
291	The version of the synchronisation protocol used when sending
292	synchronisation messages.
293
294	0 selects the original synchronisation protocol (version 0). This
295	should be used when sending synchronisation messages to a legacy
296	system that only understands the original synchronisation protocol.
297
298	1 selects the current synchronisation protocol (version 1). This
299	should be used where possible.
300
301	Kernels with this sync_version entry are able to receive messages
302	of both version 1 and version 2 of the synchronisation protocol.
303