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
160nat_icmp_send - BOOLEAN
161        0 - disabled (default)
162        not 0 - enabled
163
164        It controls sending icmp error messages (ICMP_DEST_UNREACH)
165        for VS/NAT when the load balancer receives packets from real
166        servers but the connection entries don't exist.
167
168secure_tcp - INTEGER
169        0  - disabled (default)
170
171	The secure_tcp defense is to use a more complicated TCP state
172	transition table. For VS/NAT, it also delays entering the
173	TCP ESTABLISHED state until the three way handshake is completed.
174
175        The value definition is the same as that of drop_entry and
176        drop_packet.
177
178sync_threshold - INTEGER
179        default 3
180
181        It sets synchronization threshold, which is the minimum number
182        of incoming packets that a connection needs to receive before
183        the connection will be synchronized. A connection will be
184        synchronized, every time the number of its incoming packets
185        modulus 50 equals the threshold. The range of the threshold is
186        from 0 to 49.
187
188snat_reroute - BOOLEAN
189	0 - disabled
190	not 0 - enabled (default)
191
192	If enabled, recalculate the route of SNATed packets from
193	realservers so that they are routed as if they originate from the
194	director. Otherwise they are routed as if they are forwarded by the
195	director.
196
197	If policy routing is in effect then it is possible that the route
198	of a packet originating from a director is routed differently to a
199	packet being forwarded by the director.
200
201	If policy routing is not in effect then the recalculated route will
202	always be the same as the original route so it is an optimisation
203	to disable snat_reroute and avoid the recalculation.
204
205sync_persist_mode - INTEGER
206	default 0
207
208	Controls the synchronisation of connections when using persistence
209
210	0: All types of connections are synchronised
211	1: Attempt to reduce the synchronisation traffic depending on
212	the connection type. For persistent services avoid synchronisation
213	for normal connections, do it only for persistence templates.
214	In such case, for TCP and SCTP it may need enabling sloppy_tcp and
215	sloppy_sctp flags on backup servers. For non-persistent services
216	such optimization is not applied, mode 0 is assumed.
217
218sync_version - INTEGER
219	default 1
220
221	The version of the synchronisation protocol used when sending
222	synchronisation messages.
223
224	0 selects the original synchronisation protocol (version 0). This
225	should be used when sending synchronisation messages to a legacy
226	system that only understands the original synchronisation protocol.
227
228	1 selects the current synchronisation protocol (version 1). This
229	should be used where possible.
230
231	Kernels with this sync_version entry are able to receive messages
232	of both version 1 and version 2 of the synchronisation protocol.
233