linux/Documentation/networking/ipvs-sysctl.txt
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   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
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