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