docs: networking: convert ipvs-sysctl.txt to ReST

- add SPDX header;
- add a document title;
- mark lists as such;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 302 insertions, 0 deletions

diff --git a/Documentation/networking/ipvs-sysctl.rst b/Documentation/networking/ipvs-sysctl.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+===========
+IPvs-sysctl
+===========
+
+/proc/sys/net/ipv4/vs/* Variables:
+==================================
+
+am_droprate - INTEGER
+	default 10
+
+	It sets the always mode drop rate, which is used in the mode 3
+	of the drop_rate defense.
+
+amemthresh - INTEGER
+	default 1024
+
+	It sets the available memory threshold (in pages), which is
+	used in the automatic modes of defense. When there is no
+	enough available memory, the respective strategy will be
+	enabled and the variable is automatically set to 2, otherwise
+	the strategy is disabled and the variable is  set  to 1.
+
+backup_only - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	If set, disable the director function while the server is
+	in backup mode to avoid packet loops for DR/TUN methods.
+
+conn_reuse_mode - INTEGER
+	1 - default
+
+	Controls how ipvs will deal with connections that are detected
+	port reuse. It is a bitmap, with the values being:
+
+	0: disable any special handling on port reuse. The new
+	connection will be delivered to the same real server that was
+	servicing the previous connection. This will effectively
+	disable expire_nodest_conn.
+
+	bit 1: enable rescheduling of new connections when it is safe.
+	That is, whenever expire_nodest_conn and for TCP sockets, when
+	the connection is in TIME_WAIT state (which is only possible if
+	you use NAT mode).
+
+	bit 2: it is bit 1 plus, for TCP connections, when connections
+	are in FIN_WAIT state, as this is the last state seen by load
+	balancer in Direct Routing mode. This bit helps on adding new
+	real servers to a very busy cluster.
+
+conntrack - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	If set, maintain connection tracking entries for
+	connections handled by IPVS.
+
+	This should be enabled if connections handled by IPVS are to be
+	also handled by stateful firewall rules. That is, iptables rules
+	that make use of connection tracking.  It is a performance
+	optimisation to disable this setting otherwise.
+
+	Connections handled by the IPVS FTP application module
+	will have connection tracking entries regardless of this setting.
+
+	Only available when IPVS is compiled with CONFIG_IP_VS_NFCT enabled.
+
+cache_bypass - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	If it is enabled, forward packets to the original destination
+	directly when no cache server is available and destination
+	address is not local (iph->daddr is RTN_UNICAST). It is mostly
+	used in transparent web cache cluster.
+
+debug_level - INTEGER
+	- 0          - transmission error messages (default)
+	- 1          - non-fatal error messages
+	- 2          - configuration
+	- 3          - destination trash
+	- 4          - drop entry
+	- 5          - service lookup
+	- 6          - scheduling
+	- 7          - connection new/expire, lookup and synchronization
+	- 8          - state transition
+	- 9          - binding destination, template checks and applications
+	- 10         - IPVS packet transmission
+	- 11         - IPVS packet handling (ip_vs_in/ip_vs_out)
+	- 12 or more - packet traversal
+
+	Only available when IPVS is compiled with CONFIG_IP_VS_DEBUG enabled.
+
+	Higher debugging levels include the messages for lower debugging
+	levels, so setting debug level 2, includes level 0, 1 and 2
+	messages. Thus, logging becomes more and more verbose the higher
+	the level.
+
+drop_entry - INTEGER
+	- 0  - disabled (default)
+
+	The drop_entry defense is to randomly drop entries in the
+	connection hash table, just in order to collect back some
+	memory for new connections. In the current code, the
+	drop_entry procedure can be activated every second, then it
+	randomly scans 1/32 of the whole and drops entries that are in
+	the SYN-RECV/SYNACK state, which should be effective against
+	syn-flooding attack.
+
+	The valid values of drop_entry are from 0 to 3, where 0 means
+	that this strategy is always disabled, 1 and 2 mean automatic
+	modes (when there is no enough available memory, the strategy
+	is enabled and the variable is automatically set to 2,
+	otherwise the strategy is disabled and the variable is set to
+	1), and 3 means that that the strategy is always enabled.
+
+drop_packet - INTEGER
+	- 0  - disabled (default)
+
+	The drop_packet defense is designed to drop 1/rate packets
+	before forwarding them to real servers. If the rate is 1, then
+	drop all the incoming packets.
+
+	The value definition is the same as that of the drop_entry. In
+	the automatic mode, the rate is determined by the follow
+	formula: rate = amemthresh / (amemthresh - available_memory)
+	when available memory is less than the available memory
+	threshold. When the mode 3 is set, the always mode drop rate
+	is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
+
+expire_nodest_conn - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	The default value is 0, the load balancer will silently drop
+	packets when its destination server is not available. It may
+	be useful, when user-space monitoring program deletes the
+	destination server (because of server overload or wrong
+	detection) and add back the server later, and the connections
+	to the server can continue.
+
+	If this feature is enabled, the load balancer will expire the
+	connection immediately when a packet arrives and its
+	destination server is not available, then the client program
+	will be notified that the connection is closed. This is
+	equivalent to the feature some people requires to flush
+	connections when its destination is not available.
+
+expire_quiescent_template - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	When set to a non-zero value, the load balancer will expire
+	persistent templates when the destination server is quiescent.
+	This may be useful, when a user makes a destination server
+	quiescent by setting its weight to 0 and it is desired that
+	subsequent otherwise persistent connections are sent to a
+	different destination server.  By default new persistent
+	connections are allowed to quiescent destination servers.
+
+	If this feature is enabled, the load balancer will expire the
+	persistence template if it is to be used to schedule a new
+	connection and the destination server is quiescent.
+
+ignore_tunneled - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	If set, ipvs will set the ipvs_property on all packets which are of
+	unrecognized protocols.  This prevents us from routing tunneled
+	protocols like ipip, which is useful to prevent rescheduling
+	packets that have been tunneled to the ipvs host (i.e. to prevent
+	ipvs routing loops when ipvs is also acting as a real server).
+
+nat_icmp_send - BOOLEAN
+	- 0 - disabled (default)
+	- not 0 - enabled
+
+	It controls sending icmp error messages (ICMP_DEST_UNREACH)
+	for VS/NAT when the load balancer receives packets from real
+	servers but the connection entries don't exist.
+
+pmtu_disc - BOOLEAN
+	- 0 - disabled
+	- not 0 - enabled (default)
+
+	By default, reject with FRAG_NEEDED all DF packets that exceed
+	the PMTU, irrespective of the forwarding method. For TUN method
+	the flag can be disabled to fragment such packets.
+
+secure_tcp - INTEGER
+	- 0  - disabled (default)
+
+	The secure_tcp defense is to use a more complicated TCP state
+	transition table. For VS/NAT, it also delays entering the
+	TCP ESTABLISHED state until the three way handshake is completed.
+
+	The value definition is the same as that of drop_entry and
+	drop_packet.
+
+sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period
+	default 3 50
+
+	It sets synchronization threshold, which is the minimum number
+	of incoming packets that a connection needs to receive before
+	the connection will be synchronized. A connection will be
+	synchronized, every time the number of its incoming packets
+	modulus sync_period equals the threshold. The range of the
+	threshold is from 0 to sync_period.
+
+	When sync_period and sync_refresh_period are 0, send sync only
+	for state changes or only once when pkts matches sync_threshold
+
+sync_refresh_period - UNSIGNED INTEGER
+	default 0
+
+	In seconds, difference in reported connection timer that triggers
+	new sync message. It can be used to avoid sync messages for the
+	specified period (or half of the connection timeout if it is lower)
+	if connection state is not changed since last sync.
+
+	This is useful for normal connections with high traffic to reduce
+	sync rate. Additionally, retry sync_retries times with period of
+	sync_refresh_period/8.
+
+sync_retries - INTEGER
+	default 0
+
+	Defines sync retries with period of sync_refresh_period/8. Useful
+	to protect against loss of sync messages. The range of the
+	sync_retries is from 0 to 3.
+
+sync_qlen_max - UNSIGNED LONG
+
+	Hard limit for queued sync messages that are not sent yet. It
+	defaults to 1/32 of the memory pages but actually represents
+	number of messages. It will protect us from allocating large
+	parts of memory when the sending rate is lower than the queuing
+	rate.
+
+sync_sock_size - INTEGER
+	default 0
+
+	Configuration of SNDBUF (master) or RCVBUF (slave) socket limit.
+	Default value is 0 (preserve system defaults).
+
+sync_ports - INTEGER
+	default 1
+
+	The number of threads that master and backup servers can use for
+	sync traffic. Every thread will use single UDP port, thread 0 will
+	use the default port 8848 while last thread will use port
+	8848+sync_ports-1.
+
+snat_reroute - BOOLEAN
+	- 0 - disabled
+	- not 0 - enabled (default)
+
+	If enabled, recalculate the route of SNATed packets from
+	realservers so that they are routed as if they originate from the
+	director. Otherwise they are routed as if they are forwarded by the
+	director.
+
+	If policy routing is in effect then it is possible that the route
+	of a packet originating from a director is routed differently to a
+	packet being forwarded by the director.
+
+	If policy routing is not in effect then the recalculated route will
+	always be the same as the original route so it is an optimisation
+	to disable snat_reroute and avoid the recalculation.
+
+sync_persist_mode - INTEGER
+	default 0
+
+	Controls the synchronisation of connections when using persistence
+
+	0: All types of connections are synchronised
+
+	1: Attempt to reduce the synchronisation traffic depending on
+	the connection type. For persistent services avoid synchronisation
+	for normal connections, do it only for persistence templates.
+	In such case, for TCP and SCTP it may need enabling sloppy_tcp and
+	sloppy_sctp flags on backup servers. For non-persistent services
+	such optimization is not applied, mode 0 is assumed.
+
+sync_version - INTEGER
+	default 1
+
+	The version of the synchronisation protocol used when sending
+	synchronisation messages.
+
+	0 selects the original synchronisation protocol (version 0). This
+	should be used when sending synchronisation messages to a legacy
+	system that only understands the original synchronisation protocol.
+
+	1 selects the current synchronisation protocol (version 1). This
+	should be used where possible.
+
+	Kernels with this sync_version entry are able to receive messages
+	of both version 1 and version 2 of the synchronisation protocol.