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Documentation / networking / ipvs-sysctl.txt




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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:47 EST.

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