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
  18cache_bypass - BOOLEAN
  19        0 - disabled (default)
  20        not 0 - enabled
  21
  22        If it is enabled, forward packets to the original destination
  23        directly when no cache server is available and destination
  24        address is not local (iph->daddr is RTN_UNICAST). It is mostly
  25        used in transparent web cache cluster.
  26
  27debug_level - INTEGER
  28        0          - transmission error messages (default)
  29        1          - non-fatal error messages
  30        2          - configuration
  31        3          - destination trash
  32        4          - drop entry
  33        5          - service lookup
  34        6          - scheduling
  35        7          - connection new/expire, lookup and synchronization
  36        8          - state transition
  37        9          - binding destination, template checks and applications
  38        10         - IPVS packet transmission
  39        11         - IPVS packet handling (ip_vs_in/ip_vs_out)
  40        12 or more - packet traversal
  41
  42        Only available when IPVS is compiled with the CONFIG_IPVS_DEBUG
  43
  44        Higher debugging levels include the messages for lower debugging
  45        levels, so setting debug level 2, includes level 0, 1 and 2
  46        messages. Thus, logging becomes more and more verbose the higher
  47        the level.
  48
  49drop_entry - INTEGER
  50        0  - disabled (default)
  51
  52        The drop_entry defense is to randomly drop entries in the
  53        connection hash table, just in order to collect back some
  54        memory for new connections. In the current code, the
  55        drop_entry procedure can be activated every second, then it
  56        randomly scans 1/32 of the whole and drops entries that are in
  57        the SYN-RECV/SYNACK state, which should be effective against
  58        syn-flooding attack.
  59
  60        The valid values of drop_entry are from 0 to 3, where 0 means
  61        that this strategy is always disabled, 1 and 2 mean automatic
  62        modes (when there is no enough available memory, the strategy
  63        is enabled and the variable is automatically set to 2,
  64        otherwise the strategy is disabled and the variable is set to
  65        1), and 3 means that that the strategy is always enabled.
  66
  67drop_packet - INTEGER
  68        0  - disabled (default)
  69
  70        The drop_packet defense is designed to drop 1/rate packets
  71        before forwarding them to real servers. If the rate is 1, then
  72        drop all the incoming packets.
  73
  74        The value definition is the same as that of the drop_entry. In
  75        the automatic mode, the rate is determined by the follow
  76        formula: rate = amemthresh / (amemthresh - available_memory)
  77        when available memory is less than the available memory
  78        threshold. When the mode 3 is set, the always mode drop rate
  79        is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
  80
  81expire_nodest_conn - BOOLEAN
  82        0 - disabled (default)
  83        not 0 - enabled
  84
  85        The default value is 0, the load balancer will silently drop
  86        packets when its destination server is not available. It may
  87        be useful, when user-space monitoring program deletes the
  88        destination server (because of server overload or wrong
  89        detection) and add back the server later, and the connections
  90        to the server can continue.
  91
  92        If this feature is enabled, the load balancer will expire the
  93        connection immediately when a packet arrives and its
  94        destination server is not available, then the client program
  95        will be notified that the connection is closed. This is
  96        equivalent to the feature some people requires to flush
  97        connections when its destination is not available.
  98
  99expire_quiescent_template - BOOLEAN
 100        0 - disabled (default)
 101        not 0 - enabled
 102
 103        When set to a non-zero value, the load balancer will expire
 104        persistent templates when the destination server is quiescent.
 105        This may be useful, when a user makes a destination server
 106        quiescent by setting its weight to 0 and it is desired that
 107        subsequent otherwise persistent connections are sent to a
 108        different destination server.  By default new persistent
 109        connections are allowed to quiescent destination servers.
 110
 111        If this feature is enabled, the load balancer will expire the
 112        persistence template if it is to be used to schedule a new
 113        connection and the destination server is quiescent.
 114
 115nat_icmp_send - BOOLEAN
 116        0 - disabled (default)
 117        not 0 - enabled
 118
 119        It controls sending icmp error messages (ICMP_DEST_UNREACH)
 120        for VS/NAT when the load balancer receives packets from real
 121        servers but the connection entries don't exist.
 122
 123secure_tcp - INTEGER
 124        0  - disabled (default)
 125
 126        The secure_tcp defense is to use a more complicated state
 127        transition table and some possible short timeouts of each
 128        state. In the VS/NAT, it delays the entering the ESTABLISHED
 129        until the real server starts to send data and ACK packet
 130        (after 3-way handshake).
 131
 132        The value definition is the same as that of drop_entry or
 133        drop_packet.
 134
 135sync_threshold - INTEGER
 136        default 3
 137
 138        It sets synchronization threshold, which is the minimum number
 139        of incoming packets that a connection needs to receive before
 140        the connection will be synchronized. A connection will be
 141        synchronized, every time the number of its incoming packets
 142        modulus 50 equals the threshold. The range of the threshold is
 143        from 0 to 49.
 144
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