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