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 178pmtu_disc - BOOLEAN 179 0 - disabled 180 not 0 - enabled (default) 181 182 By default, reject with FRAG_NEEDED all DF packets that exceed 183 the PMTU, irrespective of the forwarding method. For TUN method 184 the flag can be disabled to fragment such packets. 185 186secure_tcp - INTEGER 187 0 - disabled (default) 188 189 The secure_tcp defense is to use a more complicated TCP state 190 transition table. For VS/NAT, it also delays entering the 191 TCP ESTABLISHED state until the three way handshake is completed. 192 193 The value definition is the same as that of drop_entry and 194 drop_packet. 195 196sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period 197 default 3 50 198 199 It sets synchronization threshold, which is the minimum number 200 of incoming packets that a connection needs to receive before 201 the connection will be synchronized. A connection will be 202 synchronized, every time the number of its incoming packets 203 modulus sync_period equals the threshold. The range of the 204 threshold is from 0 to sync_period. 205 206 When sync_period and sync_refresh_period are 0, send sync only 207 for state changes or only once when pkts matches sync_threshold 208 209sync_refresh_period - UNSIGNED INTEGER 210 default 0 211 212 In seconds, difference in reported connection timer that triggers 213 new sync message. It can be used to avoid sync messages for the 214 specified period (or half of the connection timeout if it is lower) 215 if connection state is not changed since last sync. 216 217 This is useful for normal connections with high traffic to reduce 218 sync rate. Additionally, retry sync_retries times with period of 219 sync_refresh_period/8. 220 221sync_retries - INTEGER 222 default 0 223 224 Defines sync retries with period of sync_refresh_period/8. Useful 225 to protect against loss of sync messages. The range of the 226 sync_retries is from 0 to 3. 227 228sync_qlen_max - UNSIGNED LONG 229 230 Hard limit for queued sync messages that are not sent yet. It 231 defaults to 1/32 of the memory pages but actually represents 232 number of messages. It will protect us from allocating large 233 parts of memory when the sending rate is lower than the queuing 234 rate. 235 236sync_sock_size - INTEGER 237 default 0 238 239 Configuration of SNDBUF (master) or RCVBUF (slave) socket limit. 240 Default value is 0 (preserve system defaults). 241 242sync_ports - INTEGER 243 default 1 244 245 The number of threads that master and backup servers can use for 246 sync traffic. Every thread will use single UDP port, thread 0 will 247 use the default port 8848 while last thread will use port 248 8848+sync_ports-1. 249 250snat_reroute - BOOLEAN 251 0 - disabled 252 not 0 - enabled (default) 253 254 If enabled, recalculate the route of SNATed packets from 255 realservers so that they are routed as if they originate from the 256 director. Otherwise they are routed as if they are forwarded by the 257 director. 258 259 If policy routing is in effect then it is possible that the route 260 of a packet originating from a director is routed differently to a 261 packet being forwarded by the director. 262 263 If policy routing is not in effect then the recalculated route will 264 always be the same as the original route so it is an optimisation 265 to disable snat_reroute and avoid the recalculation. 266 267sync_persist_mode - INTEGER 268 default 0 269 270 Controls the synchronisation of connections when using persistence 271 272 0: All types of connections are synchronised 273 1: Attempt to reduce the synchronisation traffic depending on 274 the connection type. For persistent services avoid synchronisation 275 for normal connections, do it only for persistence templates. 276 In such case, for TCP and SCTP it may need enabling sloppy_tcp and 277 sloppy_sctp flags on backup servers. For non-persistent services 278 such optimization is not applied, mode 0 is assumed. 279 280sync_version - INTEGER 281 default 1 282 283 The version of the synchronisation protocol used when sending 284 synchronisation messages. 285 286 0 selects the original synchronisation protocol (version 0). This 287 should be used when sending synchronisation messages to a legacy 288 system that only understands the original synchronisation protocol. 289 290 1 selects the current synchronisation protocol (version 1). This 291 should be used where possible. 292 293 Kernels with this sync_version entry are able to receive messages 294 of both version 1 and version 2 of the synchronisation protocol. 295
