1.. SPDX-License-Identifier: GPL-2.0 2 3=========== 4IPvs-sysctl 5=========== 6 7/proc/sys/net/ipv4/vs/* Variables: 8================================== 9 10am_droprate - INTEGER 11 default 10 12 13 It sets the always mode drop rate, which is used in the mode 3 14 of the drop_rate defense. 15 16amemthresh - INTEGER 17 default 1024 18 19 It sets the available memory threshold (in pages), which is 20 used in the automatic modes of defense. When there is no 21 enough available memory, the respective strategy will be 22 enabled and the variable is automatically set to 2, otherwise 23 the strategy is disabled and the variable is set to 1. 24 25backup_only - BOOLEAN 26 - 0 - disabled (default) 27 - not 0 - enabled 28 29 If set, disable the director function while the server is 30 in backup mode to avoid packet loops for DR/TUN methods. 31 32conn_reuse_mode - INTEGER 33 1 - default 34 35 Controls how ipvs will deal with connections that are detected 36 port reuse. It is a bitmap, with the values being: 37 38 0: disable any special handling on port reuse. The new 39 connection will be delivered to the same real server that was 40 servicing the previous connection. This will effectively 41 disable expire_nodest_conn. 42 43 bit 1: enable rescheduling of new connections when it is safe. 44 That is, whenever expire_nodest_conn and for TCP sockets, when 45 the connection is in TIME_WAIT state (which is only possible if 46 you use NAT mode). 47 48 bit 2: it is bit 1 plus, for TCP connections, when connections 49 are in FIN_WAIT state, as this is the last state seen by load 50 balancer in Direct Routing mode. This bit helps on adding new 51 real servers to a very busy cluster. 52 53conntrack - BOOLEAN 54 - 0 - disabled (default) 55 - not 0 - enabled 56 57 If set, maintain connection tracking entries for 58 connections handled by IPVS. 59 60 This should be enabled if connections handled by IPVS are to be 61 also handled by stateful firewall rules. That is, iptables rules 62 that make use of connection tracking. It is a performance 63 optimisation to disable this setting otherwise. 64 65 Connections handled by the IPVS FTP application module 66 will have connection tracking entries regardless of this setting. 67 68 Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled. 69 70cache_bypass - BOOLEAN 71 - 0 - disabled (default) 72 - not 0 - enabled 73 74 If it is enabled, forward packets to the original destination 75 directly when no cache server is available and destination 76 address is not local (iph->daddr is RTN_UNICAST). It is mostly 77 used in transparent web cache cluster. 78 79debug_level - INTEGER 80 - 0 - transmission error messages (default) 81 - 1 - non-fatal error messages 82 - 2 - configuration 83 - 3 - destination trash 84 - 4 - drop entry 85 - 5 - service lookup 86 - 6 - scheduling 87 - 7 - connection new/expire, lookup and synchronization 88 - 8 - state transition 89 - 9 - binding destination, template checks and applications 90 - 10 - IPVS packet transmission 91 - 11 - IPVS packet handling (ip_vs_in/ip_vs_out) 92 - 12 or more - packet traversal 93 94 Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled. 95 96 Higher debugging levels include the messages for lower debugging 97 levels, so setting debug level 2, includes level 0, 1 and 2 98 messages. Thus, logging becomes more and more verbose the higher 99 the level. 100 101drop_entry - INTEGER 102 - 0 - disabled (default) 103 104 The drop_entry defense is to randomly drop entries in the 105 connection hash table, just in order to collect back some 106 memory for new connections. In the current code, the 107 drop_entry procedure can be activated every second, then it 108 randomly scans 1/32 of the whole and drops entries that are in 109 the SYN-RECV/SYNACK state, which should be effective against 110 syn-flooding attack. 111 112 The valid values of drop_entry are from 0 to 3, where 0 means 113 that this strategy is always disabled, 1 and 2 mean automatic 114 modes (when there is no enough available memory, the strategy 115 is enabled and the variable is automatically set to 2, 116 otherwise the strategy is disabled and the variable is set to 117 1), and 3 means that the strategy is always enabled. 118 119drop_packet - INTEGER 120 - 0 - disabled (default) 121 122 The drop_packet defense is designed to drop 1/rate packets 123 before forwarding them to real servers. If the rate is 1, then 124 drop all the incoming packets. 125 126 The value definition is the same as that of the drop_entry. In 127 the automatic mode, the rate is determined by the follow 128 formula: rate = amemthresh / (amemthresh - available_memory) 129 when available memory is less than the available memory 130 threshold. When the mode 3 is set, the always mode drop rate 131 is controlled by the /proc/sys/net/ipv4/vs/am_droprate. 132 133expire_nodest_conn - BOOLEAN 134 - 0 - disabled (default) 135 - not 0 - enabled 136 137 The default value is 0, the load balancer will silently drop 138 packets when its destination server is not available. It may 139 be useful, when user-space monitoring program deletes the 140 destination server (because of server overload or wrong 141 detection) and add back the server later, and the connections 142 to the server can continue. 143 144 If this feature is enabled, the load balancer will expire the 145 connection immediately when a packet arrives and its 146 destination server is not available, then the client program 147 will be notified that the connection is closed. This is 148 equivalent to the feature some people requires to flush 149 connections when its destination is not available. 150 151expire_quiescent_template - BOOLEAN 152 - 0 - disabled (default) 153 - not 0 - enabled 154 155 When set to a non-zero value, the load balancer will expire 156 persistent templates when the destination server is quiescent. 157 This may be useful, when a user makes a destination server 158 quiescent by setting its weight to 0 and it is desired that 159 subsequent otherwise persistent connections are sent to a 160 different destination server. By default new persistent 161 connections are allowed to quiescent destination servers. 162 163 If this feature is enabled, the load balancer will expire the 164 persistence template if it is to be used to schedule a new 165 connection and the destination server is quiescent. 166 167ignore_tunneled - BOOLEAN 168 - 0 - disabled (default) 169 - not 0 - enabled 170 171 If set, ipvs will set the ipvs_property on all packets which are of 172 unrecognized protocols. This prevents us from routing tunneled 173 protocols like ipip, which is useful to prevent rescheduling 174 packets that have been tunneled to the ipvs host (i.e. to prevent 175 ipvs routing loops when ipvs is also acting as a real server). 176 177nat_icmp_send - BOOLEAN 178 - 0 - disabled (default) 179 - not 0 - enabled 180 181 It controls sending icmp error messages (ICMP_DEST_UNREACH) 182 for VS/NAT when the load balancer receives packets from real 183 servers but the connection entries don't exist. 184 185pmtu_disc - BOOLEAN 186 - 0 - disabled 187 - not 0 - enabled (default) 188 189 By default, reject with FRAG_NEEDED all DF packets that exceed 190 the PMTU, irrespective of the forwarding method. For TUN method 191 the flag can be disabled to fragment such packets. 192 193secure_tcp - INTEGER 194 - 0 - disabled (default) 195 196 The secure_tcp defense is to use a more complicated TCP state 197 transition table. For VS/NAT, it also delays entering the 198 TCP ESTABLISHED state until the three way handshake is completed. 199 200 The value definition is the same as that of drop_entry and 201 drop_packet. 202 203sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period 204 default 3 50 205 206 It sets synchronization threshold, which is the minimum number 207 of incoming packets that a connection needs to receive before 208 the connection will be synchronized. A connection will be 209 synchronized, every time the number of its incoming packets 210 modulus sync_period equals the threshold. The range of the 211 threshold is from 0 to sync_period. 212 213 When sync_period and sync_refresh_period are 0, send sync only 214 for state changes or only once when pkts matches sync_threshold 215 216sync_refresh_period - UNSIGNED INTEGER 217 default 0 218 219 In seconds, difference in reported connection timer that triggers 220 new sync message. It can be used to avoid sync messages for the 221 specified period (or half of the connection timeout if it is lower) 222 if connection state is not changed since last sync. 223 224 This is useful for normal connections with high traffic to reduce 225 sync rate. Additionally, retry sync_retries times with period of 226 sync_refresh_period/8. 227 228sync_retries - INTEGER 229 default 0 230 231 Defines sync retries with period of sync_refresh_period/8. Useful 232 to protect against loss of sync messages. The range of the 233 sync_retries is from 0 to 3. 234 235sync_qlen_max - UNSIGNED LONG 236 237 Hard limit for queued sync messages that are not sent yet. It 238 defaults to 1/32 of the memory pages but actually represents 239 number of messages. It will protect us from allocating large 240 parts of memory when the sending rate is lower than the queuing 241 rate. 242 243sync_sock_size - INTEGER 244 default 0 245 246 Configuration of SNDBUF (master) or RCVBUF (slave) socket limit. 247 Default value is 0 (preserve system defaults). 248 249sync_ports - INTEGER 250 default 1 251 252 The number of threads that master and backup servers can use for 253 sync traffic. Every thread will use single UDP port, thread 0 will 254 use the default port 8848 while last thread will use port 255 8848+sync_ports-1. 256 257snat_reroute - BOOLEAN 258 - 0 - disabled 259 - not 0 - enabled (default) 260 261 If enabled, recalculate the route of SNATed packets from 262 realservers so that they are routed as if they originate from the 263 director. Otherwise they are routed as if they are forwarded by the 264 director. 265 266 If policy routing is in effect then it is possible that the route 267 of a packet originating from a director is routed differently to a 268 packet being forwarded by the director. 269 270 If policy routing is not in effect then the recalculated route will 271 always be the same as the original route so it is an optimisation 272 to disable snat_reroute and avoid the recalculation. 273 274sync_persist_mode - INTEGER 275 default 0 276 277 Controls the synchronisation of connections when using persistence 278 279 0: All types of connections are synchronised 280 281 1: Attempt to reduce the synchronisation traffic depending on 282 the connection type. For persistent services avoid synchronisation 283 for normal connections, do it only for persistence templates. 284 In such case, for TCP and SCTP it may need enabling sloppy_tcp and 285 sloppy_sctp flags on backup servers. For non-persistent services 286 such optimization is not applied, mode 0 is assumed. 287 288sync_version - INTEGER 289 default 1 290 291 The version of the synchronisation protocol used when sending 292 synchronisation messages. 293 294 0 selects the original synchronisation protocol (version 0). This 295 should be used when sending synchronisation messages to a legacy 296 system that only understands the original synchronisation protocol. 297 298 1 selects the current synchronisation protocol (version 1). This 299 should be used where possible. 300 301 Kernels with this sync_version entry are able to receive messages 302 of both version 1 and version 2 of the synchronisation protocol. 303