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0c12582fbc
Dmitry Akindinov is reporting for a problem where SYNs are looping between the master and backup server when the backup server is used as real server in DR mode and has IPVS rules to function as director. Even when the backup function is enabled we continue to forward traffic and schedule new connections when the current master is using the backup server as real server. While this is not a problem for NAT, for DR and TUN method the backup server can not determine if a request comes from client or from director. To avoid such loops add new sysctl flag backup_only. It can be needed for DR/TUN setups that do not need backup and director function at the same time. When the backup function is enabled we stop any forwarding and pass the traffic to the local stack (real server mode). The flag disables the director function when the backup function is enabled. For setups that enable backup function for some virtual services and director function for other virtual services there should be another more complex solution to support DR/TUN mode, may be to assign per-virtual service syncid value, so that we can differentiate the requests. Reported-by: Dmitry Akindinov <dimak@stalker.com> Tested-by: German Myzovsky <lawyer@sipnet.ru> Signed-off-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: Simon Horman <horms@verge.net.au>
198 lines
7.6 KiB
Text
198 lines
7.6 KiB
Text
/proc/sys/net/ipv4/vs/* Variables:
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am_droprate - INTEGER
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default 10
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It sets the always mode drop rate, which is used in the mode 3
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of the drop_rate defense.
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amemthresh - INTEGER
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default 1024
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It sets the available memory threshold (in pages), which is
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used in the automatic modes of defense. When there is no
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enough available memory, the respective strategy will be
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enabled and the variable is automatically set to 2, otherwise
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the strategy is disabled and the variable is set to 1.
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backup_only - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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If set, disable the director function while the server is
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in backup mode to avoid packet loops for DR/TUN methods.
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conntrack - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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If set, maintain connection tracking entries for
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connections handled by IPVS.
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This should be enabled if connections handled by IPVS are to be
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also handled by stateful firewall rules. That is, iptables rules
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that make use of connection tracking. It is a performance
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optimisation to disable this setting otherwise.
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Connections handled by the IPVS FTP application module
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will have connection tracking entries regardless of this setting.
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Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled.
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cache_bypass - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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If it is enabled, forward packets to the original destination
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directly when no cache server is available and destination
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address is not local (iph->daddr is RTN_UNICAST). It is mostly
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used in transparent web cache cluster.
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debug_level - INTEGER
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0 - transmission error messages (default)
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1 - non-fatal error messages
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2 - configuration
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3 - destination trash
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4 - drop entry
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5 - service lookup
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6 - scheduling
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7 - connection new/expire, lookup and synchronization
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8 - state transition
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9 - binding destination, template checks and applications
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10 - IPVS packet transmission
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11 - IPVS packet handling (ip_vs_in/ip_vs_out)
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12 or more - packet traversal
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Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled.
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Higher debugging levels include the messages for lower debugging
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levels, so setting debug level 2, includes level 0, 1 and 2
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messages. Thus, logging becomes more and more verbose the higher
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the level.
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drop_entry - INTEGER
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0 - disabled (default)
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The drop_entry defense is to randomly drop entries in the
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connection hash table, just in order to collect back some
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memory for new connections. In the current code, the
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drop_entry procedure can be activated every second, then it
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randomly scans 1/32 of the whole and drops entries that are in
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the SYN-RECV/SYNACK state, which should be effective against
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syn-flooding attack.
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The valid values of drop_entry are from 0 to 3, where 0 means
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that this strategy is always disabled, 1 and 2 mean automatic
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modes (when there is no enough available memory, the strategy
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is enabled and the variable is automatically set to 2,
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otherwise the strategy is disabled and the variable is set to
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1), and 3 means that that the strategy is always enabled.
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drop_packet - INTEGER
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0 - disabled (default)
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The drop_packet defense is designed to drop 1/rate packets
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before forwarding them to real servers. If the rate is 1, then
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drop all the incoming packets.
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The value definition is the same as that of the drop_entry. In
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the automatic mode, the rate is determined by the follow
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formula: rate = amemthresh / (amemthresh - available_memory)
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when available memory is less than the available memory
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threshold. When the mode 3 is set, the always mode drop rate
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is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
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expire_nodest_conn - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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The default value is 0, the load balancer will silently drop
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packets when its destination server is not available. It may
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be useful, when user-space monitoring program deletes the
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destination server (because of server overload or wrong
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detection) and add back the server later, and the connections
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to the server can continue.
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If this feature is enabled, the load balancer will expire the
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connection immediately when a packet arrives and its
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destination server is not available, then the client program
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will be notified that the connection is closed. This is
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equivalent to the feature some people requires to flush
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connections when its destination is not available.
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expire_quiescent_template - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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When set to a non-zero value, the load balancer will expire
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persistent templates when the destination server is quiescent.
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This may be useful, when a user makes a destination server
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quiescent by setting its weight to 0 and it is desired that
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subsequent otherwise persistent connections are sent to a
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different destination server. By default new persistent
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connections are allowed to quiescent destination servers.
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If this feature is enabled, the load balancer will expire the
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persistence template if it is to be used to schedule a new
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connection and the destination server is quiescent.
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nat_icmp_send - BOOLEAN
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0 - disabled (default)
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not 0 - enabled
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It controls sending icmp error messages (ICMP_DEST_UNREACH)
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for VS/NAT when the load balancer receives packets from real
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servers but the connection entries don't exist.
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secure_tcp - INTEGER
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0 - disabled (default)
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The secure_tcp defense is to use a more complicated TCP state
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transition table. For VS/NAT, it also delays entering the
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TCP ESTABLISHED state until the three way handshake is completed.
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The value definition is the same as that of drop_entry and
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drop_packet.
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sync_threshold - INTEGER
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default 3
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It sets synchronization threshold, which is the minimum number
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of incoming packets that a connection needs to receive before
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the connection will be synchronized. A connection will be
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synchronized, every time the number of its incoming packets
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modulus 50 equals the threshold. The range of the threshold is
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from 0 to 49.
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snat_reroute - BOOLEAN
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0 - disabled
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not 0 - enabled (default)
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If enabled, recalculate the route of SNATed packets from
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realservers so that they are routed as if they originate from the
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director. Otherwise they are routed as if they are forwarded by the
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director.
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If policy routing is in effect then it is possible that the route
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of a packet originating from a director is routed differently to a
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packet being forwarded by the director.
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If policy routing is not in effect then the recalculated route will
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always be the same as the original route so it is an optimisation
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to disable snat_reroute and avoid the recalculation.
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sync_version - INTEGER
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default 1
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The version of the synchronisation protocol used when sending
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synchronisation messages.
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0 selects the original synchronisation protocol (version 0). This
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should be used when sending synchronisation messages to a legacy
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system that only understands the original synchronisation protocol.
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1 selects the current synchronisation protocol (version 1). This
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should be used where possible.
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Kernels with this sync_version entry are able to receive messages
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of both version 1 and version 2 of the synchronisation protocol.
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