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
18conntrack - BOOLEAN
19	0 - disabled (default)
20	not 0 - enabled
21
22	If set, maintain connection tracking entries for
23	connections handled by IPVS.
24
25	This should be enabled if connections handled by IPVS are to be
26	also handled by stateful firewall rules. That is, iptables rules
27	that make use of connection tracking.  It is a performance
28	optimisation to disable this setting otherwise.
29
30	Connections handled by the IPVS FTP application module
31	will have connection tracking entries regardless of this setting.
32
33	Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled.
34
35cache_bypass - BOOLEAN
36        0 - disabled (default)
37        not 0 - enabled
38
39        If it is enabled, forward packets to the original destination
40        directly when no cache server is available and destination
41        address is not local (iph->daddr is RTN_UNICAST). It is mostly
42        used in transparent web cache cluster.
43
44debug_level - INTEGER
45	0          - transmission error messages (default)
46	1          - non-fatal error messages
47	2          - configuration
48	3          - destination trash
49	4          - drop entry
50	5          - service lookup
51	6          - scheduling
52	7          - connection new/expire, lookup and synchronization
53	8          - state transition
54	9          - binding destination, template checks and applications
55	10         - IPVS packet transmission
56	11         - IPVS packet handling (ip_vs_in/ip_vs_out)
57	12 or more - packet traversal
58
59	Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled.
60
61	Higher debugging levels include the messages for lower debugging
62	levels, so setting debug level 2, includes level 0, 1 and 2
63	messages. Thus, logging becomes more and more verbose the higher
64	the level.
65
66drop_entry - INTEGER
67        0  - disabled (default)
68
69        The drop_entry defense is to randomly drop entries in the
70        connection hash table, just in order to collect back some
71        memory for new connections. In the current code, the
72        drop_entry procedure can be activated every second, then it
73        randomly scans 1/32 of the whole and drops entries that are in
74        the SYN-RECV/SYNACK state, which should be effective against
75        syn-flooding attack.
76
77        The valid values of drop_entry are from 0 to 3, where 0 means
78        that this strategy is always disabled, 1 and 2 mean automatic
79        modes (when there is no enough available memory, the strategy
80        is enabled and the variable is automatically set to 2,
81        otherwise the strategy is disabled and the variable is set to
82        1), and 3 means that that the strategy is always enabled.
83
84drop_packet - INTEGER
85        0  - disabled (default)
86
87        The drop_packet defense is designed to drop 1/rate packets
88        before forwarding them to real servers. If the rate is 1, then
89        drop all the incoming packets.
90
91        The value definition is the same as that of the drop_entry. In
92        the automatic mode, the rate is determined by the follow
93        formula: rate = amemthresh / (amemthresh - available_memory)
94        when available memory is less than the available memory
95        threshold. When the mode 3 is set, the always mode drop rate
96        is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
97
98expire_nodest_conn - BOOLEAN
99        0 - disabled (default)
100        not 0 - enabled
101
102        The default value is 0, the load balancer will silently drop
103        packets when its destination server is not available. It may
104        be useful, when user-space monitoring program deletes the
105        destination server (because of server overload or wrong
106        detection) and add back the server later, and the connections
107        to the server can continue.
108
109        If this feature is enabled, the load balancer will expire the
110        connection immediately when a packet arrives and its
111        destination server is not available, then the client program
112        will be notified that the connection is closed. This is
113        equivalent to the feature some people requires to flush
114        connections when its destination is not available.
115
116expire_quiescent_template - BOOLEAN
117	0 - disabled (default)
118	not 0 - enabled
119
120	When set to a non-zero value, the load balancer will expire
121	persistent templates when the destination server is quiescent.
122	This may be useful, when a user makes a destination server
123	quiescent by setting its weight to 0 and it is desired that
124	subsequent otherwise persistent connections are sent to a
125	different destination server.  By default new persistent
126	connections are allowed to quiescent destination servers.
127
128	If this feature is enabled, the load balancer will expire the
129	persistence template if it is to be used to schedule a new
130	connection and the destination server is quiescent.
131
132nat_icmp_send - BOOLEAN
133        0 - disabled (default)
134        not 0 - enabled
135
136        It controls sending icmp error messages (ICMP_DEST_UNREACH)
137        for VS/NAT when the load balancer receives packets from real
138        servers but the connection entries don't exist.
139
140secure_tcp - INTEGER
141        0  - disabled (default)
142
143	The secure_tcp defense is to use a more complicated TCP state
144	transition table. For VS/NAT, it also delays entering the
145	TCP ESTABLISHED state until the three way handshake is completed.
146
147        The value definition is the same as that of drop_entry and
148        drop_packet.
149
150sync_threshold - INTEGER
151        default 3
152
153        It sets synchronization threshold, which is the minimum number
154        of incoming packets that a connection needs to receive before
155        the connection will be synchronized. A connection will be
156        synchronized, every time the number of its incoming packets
157        modulus 50 equals the threshold. The range of the threshold is
158        from 0 to 49.
159
160snat_reroute - BOOLEAN
161	0 - disabled
162	not 0 - enabled (default)
163
164	If enabled, recalculate the route of SNATed packets from
165	realservers so that they are routed as if they originate from the
166	director. Otherwise they are routed as if they are forwarded by the
167	director.
168
169	If policy routing is in effect then it is possible that the route
170	of a packet originating from a director is routed differently to a
171	packet being forwarded by the director.
172
173	If policy routing is not in effect then the recalculated route will
174	always be the same as the original route so it is an optimisation
175	to disable snat_reroute and avoid the recalculation.
176
177sync_version - INTEGER
178	default 1
179
180	The version of the synchronisation protocol used when sending
181	synchronisation messages.
182
183	0 selects the original synchronisation protocol (version 0). This
184	should be used when sending synchronisation messages to a legacy
185	system that only understands the original synchronisation protocol.
186
187	1 selects the current synchronisation protocol (version 1). This
188	should be used where possible.
189
190	Kernels with this sync_version entry are able to receive messages
191	of both version 1 and version 2 of the synchronisation protocol.
192