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Paul Gortmakerfaa52732013-06-21 14:56:12 -04001Documentation for /proc/sys/net/*
Shen Feng760df932009-04-02 16:57:20 -07002 (c) 1999 Terrehon Bowden <terrehon@pacbell.net>
3 Bodo Bauer <bb@ricochet.net>
4 (c) 2000 Jorge Nerin <comandante@zaralinux.com>
5 (c) 2009 Shen Feng <shen@cn.fujitsu.com>
6
7For general info and legal blurb, please look in README.
8
9==============================================================
10
11This file contains the documentation for the sysctl files in
Paul Gortmakerfaa52732013-06-21 14:56:12 -040012/proc/sys/net
Shen Feng760df932009-04-02 16:57:20 -070013
14The interface to the networking parts of the kernel is located in
Paul Gortmakerfaa52732013-06-21 14:56:12 -040015/proc/sys/net. The following table shows all possible subdirectories. You may
Shen Feng760df932009-04-02 16:57:20 -070016see only some of them, depending on your kernel's configuration.
17
18
19Table : Subdirectories in /proc/sys/net
20..............................................................................
21 Directory Content Directory Content
22 core General parameter appletalk Appletalk protocol
23 unix Unix domain sockets netrom NET/ROM
24 802 E802 protocol ax25 AX25
25 ethernet Ethernet protocol rose X.25 PLP layer
26 ipv4 IP version 4 x25 X.25 protocol
27 ipx IPX token-ring IBM token ring
28 bridge Bridging decnet DEC net
Ying Xuecc79dd12013-06-17 10:54:37 -040029 ipv6 IP version 6 tipc TIPC
Shen Feng760df932009-04-02 16:57:20 -070030..............................................................................
31
321. /proc/sys/net/core - Network core options
33-------------------------------------------------------
34
Eric Dumazet0a148422011-04-20 09:27:32 +000035bpf_jit_enable
36--------------
37
38This enables Berkeley Packet Filter Just in Time compiler.
39Currently supported on x86_64 architecture, bpf_jit provides a framework
40to speed packet filtering, the one used by tcpdump/libpcap for example.
41Values :
42 0 - disable the JIT (default value)
43 1 - enable the JIT
44 2 - enable the JIT and ask the compiler to emit traces on kernel log.
45
Shan Weic60f6aa2012-04-26 16:52:52 +000046dev_weight
47--------------
48
49The maximum number of packets that kernel can handle on a NAPI interrupt,
50it's a Per-CPU variable.
51Default: 64
52
stephen hemminger6da7c8f2013-08-27 16:19:08 -070053default_qdisc
54--------------
55
56The default queuing discipline to use for network devices. This allows
57overriding the default queue discipline of pfifo_fast with an
58alternative. Since the default queuing discipline is created with the
59no additional parameters so is best suited to queuing disciplines that
60work well without configuration like stochastic fair queue (sfq),
61CoDel (codel) or fair queue CoDel (fq_codel). Don't use queuing disciplines
62like Hierarchical Token Bucket or Deficit Round Robin which require setting
63up classes and bandwidths.
64Default: pfifo_fast
65
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030066busy_read
Eliezer Tamir2d48d672013-06-24 10:28:03 +030067----------------
Cong Wange0d10952013-08-01 11:10:25 +080068Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
Eliezer Tamircbf55002013-07-08 16:20:34 +030069Approximate time in us to busy loop waiting for packets on the device queue.
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030070This sets the default value of the SO_BUSY_POLL socket option.
71Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
72which is the preferred method of enabling. If you need to enable the feature
73globally via sysctl, a value of 50 is recommended.
Eliezer Tamircbf55002013-07-08 16:20:34 +030074Will increase power usage.
Eliezer Tamir2d48d672013-06-24 10:28:03 +030075Default: 0 (off)
76
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030077busy_poll
Eliezer Tamir06021292013-06-10 11:39:50 +030078----------------
Cong Wange0d10952013-08-01 11:10:25 +080079Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
Eliezer Tamircbf55002013-07-08 16:20:34 +030080Approximate time in us to busy loop waiting for events.
Eliezer Tamir2d48d672013-06-24 10:28:03 +030081Recommended value depends on the number of sockets you poll on.
82For several sockets 50, for several hundreds 100.
83For more than that you probably want to use epoll.
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030084Note that only sockets with SO_BUSY_POLL set will be busy polled,
85so you want to either selectively set SO_BUSY_POLL on those sockets or set
86sysctl.net.busy_read globally.
Eliezer Tamircbf55002013-07-08 16:20:34 +030087Will increase power usage.
Eliezer Tamir06021292013-06-10 11:39:50 +030088Default: 0 (off)
89
Shen Feng760df932009-04-02 16:57:20 -070090rmem_default
91------------
92
93The default setting of the socket receive buffer in bytes.
94
95rmem_max
96--------
97
98The maximum receive socket buffer size in bytes.
99
100wmem_default
101------------
102
103The default setting (in bytes) of the socket send buffer.
104
105wmem_max
106--------
107
108The maximum send socket buffer size in bytes.
109
110message_burst and message_cost
111------------------------------
112
113These parameters are used to limit the warning messages written to the kernel
114log from the networking code. They enforce a rate limit to make a
115denial-of-service attack impossible. A higher message_cost factor, results in
116fewer messages that will be written. Message_burst controls when messages will
117be dropped. The default settings limit warning messages to one every five
118seconds.
119
120warnings
121--------
122
123This controls console messages from the networking stack that can occur because
124of problems on the network like duplicate address or bad checksums. Normally,
125this should be enabled, but if the problem persists the messages can be
126disabled.
127
128netdev_budget
129-------------
130
131Maximum number of packets taken from all interfaces in one polling cycle (NAPI
132poll). In one polling cycle interfaces which are registered to polling are
Rami Rosen3cc75872013-05-17 09:10:34 +0000133probed in a round-robin manner.
Shen Feng760df932009-04-02 16:57:20 -0700134
135netdev_max_backlog
136------------------
137
138Maximum number of packets, queued on the INPUT side, when the interface
139receives packets faster than kernel can process them.
140
Eric Dumazet3b098e22010-05-15 23:57:10 -0700141netdev_tstamp_prequeue
142----------------------
143
144If set to 0, RX packet timestamps can be sampled after RPS processing, when
145the target CPU processes packets. It might give some delay on timestamps, but
146permit to distribute the load on several cpus.
147
148If set to 1 (default), timestamps are sampled as soon as possible, before
149queueing.
150
Shen Feng760df932009-04-02 16:57:20 -0700151optmem_max
152----------
153
154Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
155of struct cmsghdr structures with appended data.
156
1572. /proc/sys/net/unix - Parameters for Unix domain sockets
158-------------------------------------------------------
159
Li Xiaodong45dad7b2009-04-02 16:57:21 -0700160There is only one file in this directory.
161unix_dgram_qlen limits the max number of datagrams queued in Unix domain
Li Zefanca8b9952009-04-13 14:39:36 -0700162socket's buffer. It will not take effect unless PF_UNIX flag is specified.
Shen Feng760df932009-04-02 16:57:20 -0700163
164
1653. /proc/sys/net/ipv4 - IPV4 settings
166-------------------------------------------------------
167Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
168descriptions of these entries.
169
170
1714. Appletalk
172-------------------------------------------------------
173
174The /proc/sys/net/appletalk directory holds the Appletalk configuration data
175when Appletalk is loaded. The configurable parameters are:
176
177aarp-expiry-time
178----------------
179
180The amount of time we keep an ARP entry before expiring it. Used to age out
181old hosts.
182
183aarp-resolve-time
184-----------------
185
186The amount of time we will spend trying to resolve an Appletalk address.
187
188aarp-retransmit-limit
189---------------------
190
191The number of times we will retransmit a query before giving up.
192
193aarp-tick-time
194--------------
195
196Controls the rate at which expires are checked.
197
198The directory /proc/net/appletalk holds the list of active Appletalk sockets
199on a machine.
200
201The fields indicate the DDP type, the local address (in network:node format)
202the remote address, the size of the transmit pending queue, the size of the
203received queue (bytes waiting for applications to read) the state and the uid
204owning the socket.
205
206/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
207shows the name of the interface, its Appletalk address, the network range on
208that address (or network number for phase 1 networks), and the status of the
209interface.
210
211/proc/net/atalk_route lists each known network route. It lists the target
212(network) that the route leads to, the router (may be directly connected), the
213route flags, and the device the route is using.
214
215
2165. IPX
217-------------------------------------------------------
218
219The IPX protocol has no tunable values in proc/sys/net.
220
221The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
222socket giving the local and remote addresses in Novell format (that is
223network:node:port). In accordance with the strange Novell tradition,
224everything but the port is in hex. Not_Connected is displayed for sockets that
225are not tied to a specific remote address. The Tx and Rx queue sizes indicate
226the number of bytes pending for transmission and reception. The state
227indicates the state the socket is in and the uid is the owning uid of the
228socket.
229
230The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
231it gives the network number, the node number, and indicates if the network is
232the primary network. It also indicates which device it is bound to (or
233Internal for internal networks) and the Frame Type if appropriate. Linux
234supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
235IPX.
236
237The /proc/net/ipx_route table holds a list of IPX routes. For each route it
238gives the destination network, the router node (or Directly) and the network
239address of the router (or Connected) for internal networks.
Ying Xuecc79dd12013-06-17 10:54:37 -0400240
2416. TIPC
242-------------------------------------------------------
243
Erik Hugnea5325ae2014-08-28 09:08:47 +0200244tipc_rmem
245----------
246
Ying Xuecc79dd12013-06-17 10:54:37 -0400247The TIPC protocol now has a tunable for the receive memory, similar to the
248tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
249
250 # cat /proc/sys/net/tipc/tipc_rmem
251 4252725 34021800 68043600
252 #
253
254The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
255are scaled (shifted) versions of that same value. Note that the min value
256is not at this point in time used in any meaningful way, but the triplet is
257preserved in order to be consistent with things like tcp_rmem.
Erik Hugnea5325ae2014-08-28 09:08:47 +0200258
259named_timeout
260--------------
261
262TIPC name table updates are distributed asynchronously in a cluster, without
263any form of transaction handling. This means that different race scenarios are
264possible. One such is that a name withdrawal sent out by one node and received
265by another node may arrive after a second, overlapping name publication already
266has been accepted from a third node, although the conflicting updates
267originally may have been issued in the correct sequential order.
268If named_timeout is nonzero, failed topology updates will be placed on a defer
269queue until another event arrives that clears the error, or until the timeout
270expires. Value is in milliseconds.