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Based on kernel version 4.3. Page generated on 2015-11-02 12:51 EST.

1	Documentation for /proc/sys/net/*
2		(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	
7	For general info and legal blurb, please look in README.
8	
9	==============================================================
10	
11	This file contains the documentation for the sysctl files in
12	/proc/sys/net
13	
14	The interface  to  the  networking  parts  of  the  kernel  is  located  in
15	/proc/sys/net. The following table shows all possible subdirectories.  You may
16	see only some of them, depending on your kernel's configuration.
17	
18	
19	Table : 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
29	 ipv6      IP version 6        tipc       TIPC
30	..............................................................................
31	
32	1. /proc/sys/net/core - Network core options
33	-------------------------------------------------------
34	
35	bpf_jit_enable
36	--------------
37	
38	This enables Berkeley Packet Filter Just in Time compiler.
39	Currently supported on x86_64 architecture, bpf_jit provides a framework
40	to speed packet filtering, the one used by tcpdump/libpcap for example.
41	Values :
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	
46	dev_weight
47	--------------
48	
49	The maximum number of packets that kernel can handle on a NAPI interrupt,
50	it's a Per-CPU variable.
51	Default: 64
52	
53	default_qdisc
54	--------------
55	
56	The default queuing discipline to use for network devices. This allows
57	overriding the default of pfifo_fast with an alternative. Since the default
58	queuing discipline is created without additional parameters so is best suited
59	to queuing disciplines that work well without configuration like stochastic
60	fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
61	queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
62	which require setting up classes and bandwidths. Note that physical multiqueue
63	interfaces still use mq as root qdisc, which in turn uses this default for its
64	leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
65	default to noqueue.
66	Default: pfifo_fast
67	
68	busy_read
69	----------------
70	Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
71	Approximate time in us to busy loop waiting for packets on the device queue.
72	This sets the default value of the SO_BUSY_POLL socket option.
73	Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
74	which is the preferred method of enabling. If you need to enable the feature
75	globally via sysctl, a value of 50 is recommended.
76	Will increase power usage.
77	Default: 0 (off)
78	
79	busy_poll
80	----------------
81	Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
82	Approximate time in us to busy loop waiting for events.
83	Recommended value depends on the number of sockets you poll on.
84	For several sockets 50, for several hundreds 100.
85	For more than that you probably want to use epoll.
86	Note that only sockets with SO_BUSY_POLL set will be busy polled,
87	so you want to either selectively set SO_BUSY_POLL on those sockets or set
88	sysctl.net.busy_read globally.
89	Will increase power usage.
90	Default: 0 (off)
91	
92	rmem_default
93	------------
94	
95	The default setting of the socket receive buffer in bytes.
96	
97	rmem_max
98	--------
99	
100	The maximum receive socket buffer size in bytes.
101	
102	tstamp_allow_data
103	-----------------
104	Allow processes to receive tx timestamps looped together with the original
105	packet contents. If disabled, transmit timestamp requests from unprivileged
106	processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
107	Default: 1 (on)
108	
109	
110	wmem_default
111	------------
112	
113	The default setting (in bytes) of the socket send buffer.
114	
115	wmem_max
116	--------
117	
118	The maximum send socket buffer size in bytes.
119	
120	message_burst and message_cost
121	------------------------------
122	
123	These parameters  are used to limit the warning messages written to the kernel
124	log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
125	denial-of-service attack  impossible. A higher message_cost factor, results in
126	fewer messages that will be written. Message_burst controls when messages will
127	be dropped.  The  default  settings  limit  warning messages to one every five
128	seconds.
129	
130	warnings
131	--------
132	
133	This sysctl is now unused.
134	
135	This was used to control console messages from the networking stack that
136	occur because of problems on the network like duplicate address or bad
137	checksums.
138	
139	These messages are now emitted at KERN_DEBUG and can generally be enabled
140	and controlled by the dynamic_debug facility.
141	
142	netdev_budget
143	-------------
144	
145	Maximum number of packets taken from all interfaces in one polling cycle (NAPI
146	poll). In one polling cycle interfaces which are registered to polling are
147	probed in a round-robin manner.
148	
149	netdev_max_backlog
150	------------------
151	
152	Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
153	receives packets faster than kernel can process them.
154	
155	netdev_rss_key
156	--------------
157	
158	RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
159	randomly generated.
160	Some user space might need to gather its content even if drivers do not
161	provide ethtool -x support yet.
162	
163	myhost:~# cat /proc/sys/net/core/netdev_rss_key
164	84:50: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	
166	File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
167	Note:
168	/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
169	but most drivers only use 40 bytes of it.
170	
171	myhost:~# ethtool -x eth0
172	RX flow hash indirection table for eth0 with 8 RX ring(s):
173	    0:    0     1     2     3     4     5     6     7
174	RSS hash key:
175	84:50: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	
177	netdev_tstamp_prequeue
178	----------------------
179	
180	If set to 0, RX packet timestamps can be sampled after RPS processing, when
181	the target CPU processes packets. It might give some delay on timestamps, but
182	permit to distribute the load on several cpus.
183	
184	If set to 1 (default), timestamps are sampled as soon as possible, before
185	queueing.
186	
187	optmem_max
188	----------
189	
190	Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
191	of struct cmsghdr structures with appended data.
192	
193	2. /proc/sys/net/unix - Parameters for Unix domain sockets
194	-------------------------------------------------------
195	
196	There is only one file in this directory.
197	unix_dgram_qlen limits the max number of datagrams queued in Unix domain
198	socket's buffer. It will not take effect unless PF_UNIX flag is specified.
199	
200	
201	3. /proc/sys/net/ipv4 - IPV4 settings
202	-------------------------------------------------------
203	Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
204	descriptions of these entries.
205	
206	
207	4. Appletalk
208	-------------------------------------------------------
209	
210	The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
211	when Appletalk is loaded. The configurable parameters are:
212	
213	aarp-expiry-time
214	----------------
215	
216	The amount  of  time  we keep an ARP entry before expiring it. Used to age out
217	old hosts.
218	
219	aarp-resolve-time
220	-----------------
221	
222	The amount of time we will spend trying to resolve an Appletalk address.
223	
224	aarp-retransmit-limit
225	---------------------
226	
227	The number of times we will retransmit a query before giving up.
228	
229	aarp-tick-time
230	--------------
231	
232	Controls the rate at which expires are checked.
233	
234	The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
235	on a machine.
236	
237	The fields  indicate  the DDP type, the local address (in network:node format)
238	the remote  address,  the  size of the transmit pending queue, the size of the
239	received queue  (bytes waiting for applications to read) the state and the uid
240	owning the socket.
241	
242	/proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
243	shows the  name  of the interface, its Appletalk address, the network range on
244	that address  (or  network number for phase 1 networks), and the status of the
245	interface.
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
249	route flags, and the device the route is using.
250	
251	
252	5. IPX
253	-------------------------------------------------------
254	
255	The IPX protocol has no tunable values in proc/sys/net.
256	
257	The IPX  protocol  does,  however,  provide  proc/net/ipx. This lists each IPX
258	socket giving  the  local  and  remote  addresses  in  Novell  format (that is
259	network:node:port). In  accordance  with  the  strange  Novell  tradition,
260	everything but the port is in hex. Not_Connected is displayed for sockets that
261	are not  tied to a specific remote address. The Tx and Rx queue sizes indicate
262	the number  of  bytes  pending  for  transmission  and  reception.  The  state
263	indicates the  state  the  socket  is  in and the uid is the owning uid of the
264	socket.
265	
266	The /proc/net/ipx_interface  file lists all IPX interfaces. For each interface
267	it gives  the network number, the node number, and indicates if the network is
268	the primary  network.  It  also  indicates  which  device  it  is bound to (or
269	Internal for  internal  networks)  and  the  Frame  Type if appropriate. Linux
270	supports 802.3,  802.2,  802.2  SNAP  and DIX (Blue Book) ethernet framing for
271	IPX.
272	
273	The /proc/net/ipx_route  table  holds  a list of IPX routes. For each route it
274	gives the  destination  network, the router node (or Directly) and the network
275	address of the router (or Connected) for internal networks.
276	
277	6. TIPC
278	-------------------------------------------------------
279	
280	tipc_rmem
281	----------
282	
283	The TIPC protocol now has a tunable for the receive memory, similar to the
284	tcp_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	
290	The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
291	are scaled (shifted) versions of that same value.  Note that the min value
292	is not at this point in time used in any meaningful way, but the triplet is
293	preserved in order to be consistent with things like tcp_rmem.
294	
295	named_timeout
296	--------------
297	
298	TIPC name table updates are distributed asynchronously in a cluster, without
299	any form of transaction handling. This means that different race scenarios are
300	possible. One such is that a name withdrawal sent out by one node and received
301	by another node may arrive after a second, overlapping name publication already
302	has been accepted from a third node, although the conflicting updates
303	originally may have been issued in the correct sequential order.
304	If named_timeout is nonzero, failed topology updates will be placed on a defer
305	queue until another event arrives that clears the error, or until the timeout
306	expires. Value is in milliseconds.
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