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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
Phil Sutter2e641262015-09-15 10:33:07 +020057overriding the default of pfifo_fast with an alternative. Since the default
58queuing discipline is created without additional parameters so is best suited
59to queuing disciplines that work well without configuration like stochastic
60fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
61queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
62which require setting up classes and bandwidths. Note that physical multiqueue
63interfaces still use mq as root qdisc, which in turn uses this default for its
64leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
65default to noqueue.
stephen hemminger6da7c8f2013-08-27 16:19:08 -070066Default: pfifo_fast
67
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030068busy_read
Eliezer Tamir2d48d672013-06-24 10:28:03 +030069----------------
Cong Wange0d10952013-08-01 11:10:25 +080070Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
Eliezer Tamircbf55002013-07-08 16:20:34 +030071Approximate time in us to busy loop waiting for packets on the device queue.
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030072This sets the default value of the SO_BUSY_POLL socket option.
73Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
74which is the preferred method of enabling. If you need to enable the feature
75globally via sysctl, a value of 50 is recommended.
Eliezer Tamircbf55002013-07-08 16:20:34 +030076Will increase power usage.
Eliezer Tamir2d48d672013-06-24 10:28:03 +030077Default: 0 (off)
78
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030079busy_poll
Eliezer Tamir06021292013-06-10 11:39:50 +030080----------------
Cong Wange0d10952013-08-01 11:10:25 +080081Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
Eliezer Tamircbf55002013-07-08 16:20:34 +030082Approximate time in us to busy loop waiting for events.
Eliezer Tamir2d48d672013-06-24 10:28:03 +030083Recommended value depends on the number of sockets you poll on.
84For several sockets 50, for several hundreds 100.
85For more than that you probably want to use epoll.
Eliezer Tamir64b0dc52013-07-10 17:13:36 +030086Note that only sockets with SO_BUSY_POLL set will be busy polled,
87so you want to either selectively set SO_BUSY_POLL on those sockets or set
88sysctl.net.busy_read globally.
Eliezer Tamircbf55002013-07-08 16:20:34 +030089Will increase power usage.
Eliezer Tamir06021292013-06-10 11:39:50 +030090Default: 0 (off)
91
Shen Feng760df932009-04-02 16:57:20 -070092rmem_default
93------------
94
95The default setting of the socket receive buffer in bytes.
96
97rmem_max
98--------
99
100The maximum receive socket buffer size in bytes.
101
Willem de Bruijnb245be12015-01-30 13:29:32 -0500102tstamp_allow_data
103-----------------
104Allow processes to receive tx timestamps looped together with the original
105packet contents. If disabled, transmit timestamp requests from unprivileged
106processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
107Default: 1 (on)
108
109
Shen Feng760df932009-04-02 16:57:20 -0700110wmem_default
111------------
112
113The default setting (in bytes) of the socket send buffer.
114
115wmem_max
116--------
117
118The maximum send socket buffer size in bytes.
119
120message_burst and message_cost
121------------------------------
122
123These parameters are used to limit the warning messages written to the kernel
124log from the networking code. They enforce a rate limit to make a
125denial-of-service attack impossible. A higher message_cost factor, results in
126fewer messages that will be written. Message_burst controls when messages will
127be dropped. The default settings limit warning messages to one every five
128seconds.
129
130warnings
131--------
132
Joe Perchesba7a46f2014-11-11 10:59:17 -0800133This sysctl is now unused.
134
135This was used to control console messages from the networking stack that
136occur because of problems on the network like duplicate address or bad
137checksums.
138
139These messages are now emitted at KERN_DEBUG and can generally be enabled
140and controlled by the dynamic_debug facility.
Shen Feng760df932009-04-02 16:57:20 -0700141
142netdev_budget
143-------------
144
145Maximum number of packets taken from all interfaces in one polling cycle (NAPI
146poll). In one polling cycle interfaces which are registered to polling are
Rami Rosen3cc75872013-05-17 09:10:34 +0000147probed in a round-robin manner.
Shen Feng760df932009-04-02 16:57:20 -0700148
149netdev_max_backlog
150------------------
151
152Maximum number of packets, queued on the INPUT side, when the interface
153receives packets faster than kernel can process them.
154
Eric Dumazet960fb622014-11-16 06:23:05 -0800155netdev_rss_key
156--------------
157
158RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
159randomly generated.
160Some user space might need to gather its content even if drivers do not
161provide ethtool -x support yet.
162
163myhost:~# cat /proc/sys/net/core/netdev_rss_key
16484:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8: ... (52 bytes total)
165
166File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
167Note:
168/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
169but most drivers only use 40 bytes of it.
170
171myhost:~# ethtool -x eth0
172RX flow hash indirection table for eth0 with 8 RX ring(s):
173 0: 0 1 2 3 4 5 6 7
174RSS hash key:
17584:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47:25:42:97:74:ca:56:bb:b6:a1:d8:43:e3:c9:0c:fd:17:55:c2:3a:4d:69:ed:f1:42:89
176
Eric Dumazet3b098e22010-05-15 23:57:10 -0700177netdev_tstamp_prequeue
178----------------------
179
180If set to 0, RX packet timestamps can be sampled after RPS processing, when
181the target CPU processes packets. It might give some delay on timestamps, but
182permit to distribute the load on several cpus.
183
184If set to 1 (default), timestamps are sampled as soon as possible, before
185queueing.
186
Shen Feng760df932009-04-02 16:57:20 -0700187optmem_max
188----------
189
190Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
191of struct cmsghdr structures with appended data.
192
1932. /proc/sys/net/unix - Parameters for Unix domain sockets
194-------------------------------------------------------
195
Li Xiaodong45dad7b2009-04-02 16:57:21 -0700196There is only one file in this directory.
197unix_dgram_qlen limits the max number of datagrams queued in Unix domain
Li Zefanca8b9952009-04-13 14:39:36 -0700198socket's buffer. It will not take effect unless PF_UNIX flag is specified.
Shen Feng760df932009-04-02 16:57:20 -0700199
200
2013. /proc/sys/net/ipv4 - IPV4 settings
202-------------------------------------------------------
203Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
204descriptions of these entries.
205
206
2074. Appletalk
208-------------------------------------------------------
209
210The /proc/sys/net/appletalk directory holds the Appletalk configuration data
211when Appletalk is loaded. The configurable parameters are:
212
213aarp-expiry-time
214----------------
215
216The amount of time we keep an ARP entry before expiring it. Used to age out
217old hosts.
218
219aarp-resolve-time
220-----------------
221
222The amount of time we will spend trying to resolve an Appletalk address.
223
224aarp-retransmit-limit
225---------------------
226
227The number of times we will retransmit a query before giving up.
228
229aarp-tick-time
230--------------
231
232Controls the rate at which expires are checked.
233
234The directory /proc/net/appletalk holds the list of active Appletalk sockets
235on a machine.
236
237The fields indicate the DDP type, the local address (in network:node format)
238the remote address, the size of the transmit pending queue, the size of the
239received queue (bytes waiting for applications to read) the state and the uid
240owning the socket.
241
242/proc/net/atalk_iface lists all the interfaces configured for appletalk.It
243shows the name of the interface, its Appletalk address, the network range on
244that address (or network number for phase 1 networks), and the status of the
245interface.
246
247/proc/net/atalk_route lists each known network route. It lists the target
248(network) that the route leads to, the router (may be directly connected), the
249route flags, and the device the route is using.
250
251
2525. IPX
253-------------------------------------------------------
254
255The IPX protocol has no tunable values in proc/sys/net.
256
257The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
258socket giving the local and remote addresses in Novell format (that is
259network:node:port). In accordance with the strange Novell tradition,
260everything but the port is in hex. Not_Connected is displayed for sockets that
261are not tied to a specific remote address. The Tx and Rx queue sizes indicate
262the number of bytes pending for transmission and reception. The state
263indicates the state the socket is in and the uid is the owning uid of the
264socket.
265
266The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
267it gives the network number, the node number, and indicates if the network is
268the primary network. It also indicates which device it is bound to (or
269Internal for internal networks) and the Frame Type if appropriate. Linux
270supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
271IPX.
272
273The /proc/net/ipx_route table holds a list of IPX routes. For each route it
274gives the destination network, the router node (or Directly) and the network
275address of the router (or Connected) for internal networks.
Ying Xuecc79dd12013-06-17 10:54:37 -0400276
2776. TIPC
278-------------------------------------------------------
279
Erik Hugnea5325ae2014-08-28 09:08:47 +0200280tipc_rmem
281----------
282
Ying Xuecc79dd12013-06-17 10:54:37 -0400283The TIPC protocol now has a tunable for the receive memory, similar to the
284tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
285
286 # cat /proc/sys/net/tipc/tipc_rmem
287 4252725 34021800 68043600
288 #
289
290The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
291are scaled (shifted) versions of that same value. Note that the min value
292is not at this point in time used in any meaningful way, but the triplet is
293preserved in order to be consistent with things like tcp_rmem.
Erik Hugnea5325ae2014-08-28 09:08:47 +0200294
295named_timeout
296--------------
297
298TIPC name table updates are distributed asynchronously in a cluster, without
299any form of transaction handling. This means that different race scenarios are
300possible. One such is that a name withdrawal sent out by one node and received
301by another node may arrive after a second, overlapping name publication already
302has been accepted from a third node, although the conflicting updates
303originally may have been issued in the correct sequential order.
304If named_timeout is nonzero, failed topology updates will be placed on a defer
305queue until another event arrives that clears the error, or until the timeout
306expires. Value is in milliseconds.