1 /proc/sys/net/ipv4/vs/* Variables:
6 It sets the always mode drop rate, which is used in the mode 3
7 of the drop_rate defense.
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.
19 0 - disabled (default)
22 If set, disable the director function while the server is
23 in backup mode to avoid packet loops for DR/TUN methods.
25 conn_reuse_mode - INTEGER
28 Controls how ipvs will deal with connections that are detected
29 port reuse. It is a bitmap, with the values being:
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.
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
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.
47 0 - disabled (default)
50 If set, maintain connection tracking entries for
51 connections handled by IPVS.
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.
58 Connections handled by the IPVS FTP application module
59 will have connection tracking entries regardless of this setting.
61 Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled.
63 cache_bypass - BOOLEAN
64 0 - disabled (default)
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.
73 0 - transmission error messages (default)
74 1 - non-fatal error messages
80 7 - connection new/expire, lookup and synchronization
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
87 Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled.
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
95 0 - disabled (default)
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
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.
112 drop_packet - INTEGER
113 0 - disabled (default)
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.
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.
126 expire_nodest_conn - BOOLEAN
127 0 - disabled (default)
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.
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.
144 expire_quiescent_template - BOOLEAN
145 0 - disabled (default)
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.
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.
160 ignore_tunneled - BOOLEAN
161 0 - disabled (default)
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).
170 nat_icmp_send - BOOLEAN
171 0 - disabled (default)
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.
179 0 - disabled (default)
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.
185 The value definition is the same as that of drop_entry and
188 sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period
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 sync_period equals the threshold. The range of the
196 threshold is from 0 to sync_period.
198 When sync_period and sync_refresh_period are 0, send sync only
199 for state changes or only once when pkts matches sync_threshold
201 sync_refresh_period - UNSIGNED INTEGER
204 In seconds, difference in reported connection timer that triggers
205 new sync message. It can be used to avoid sync messages for the
206 specified period (or half of the connection timeout if it is lower)
207 if connection state is not changed since last sync.
209 This is useful for normal connections with high traffic to reduce
210 sync rate. Additionally, retry sync_retries times with period of
211 sync_refresh_period/8.
213 sync_retries - INTEGER
216 Defines sync retries with period of sync_refresh_period/8. Useful
217 to protect against loss of sync messages. The range of the
218 sync_retries is from 0 to 3.
220 sync_qlen_max - UNSIGNED LONG
222 Hard limit for queued sync messages that are not sent yet. It
223 defaults to 1/32 of the memory pages but actually represents
224 number of messages. It will protect us from allocating large
225 parts of memory when the sending rate is lower than the queuing
228 sync_sock_size - INTEGER
231 Configuration of SNDBUF (master) or RCVBUF (slave) socket limit.
232 Default value is 0 (preserve system defaults).
234 snat_reroute - BOOLEAN
236 not 0 - enabled (default)
238 If enabled, recalculate the route of SNATed packets from
239 realservers so that they are routed as if they originate from the
240 director. Otherwise they are routed as if they are forwarded by the
243 If policy routing is in effect then it is possible that the route
244 of a packet originating from a director is routed differently to a
245 packet being forwarded by the director.
247 If policy routing is not in effect then the recalculated route will
248 always be the same as the original route so it is an optimisation
249 to disable snat_reroute and avoid the recalculation.
251 sync_persist_mode - INTEGER
254 Controls the synchronisation of connections when using persistence
256 0: All types of connections are synchronised
257 1: Attempt to reduce the synchronisation traffic depending on
258 the connection type. For persistent services avoid synchronisation
259 for normal connections, do it only for persistence templates.
260 In such case, for TCP and SCTP it may need enabling sloppy_tcp and
261 sloppy_sctp flags on backup servers. For non-persistent services
262 such optimization is not applied, mode 0 is assumed.
264 sync_version - INTEGER
267 The version of the synchronisation protocol used when sending
268 synchronisation messages.
270 0 selects the original synchronisation protocol (version 0). This
271 should be used when sending synchronisation messages to a legacy
272 system that only understands the original synchronisation protocol.
274 1 selects the current synchronisation protocol (version 1). This
275 should be used where possible.
277 Kernels with this sync_version entry are able to receive messages
278 of both version 1 and version 2 of the synchronisation protocol.