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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:48 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	bpf_jit_harden
47	--------------
48	
49	This enables hardening for the Berkeley Packet Filter Just in Time compiler.
50	Supported are eBPF JIT backends. Enabling hardening trades off performance,
51	but can mitigate JIT spraying.
52	Values :
53		0 - disable JIT hardening (default value)
54		1 - enable JIT hardening for unprivileged users only
55		2 - enable JIT hardening for all users
56	
57	dev_weight
58	--------------
59	
60	The maximum number of packets that kernel can handle on a NAPI interrupt,
61	it's a Per-CPU variable.
62	Default: 64
63	
64	default_qdisc
65	--------------
66	
67	The default queuing discipline to use for network devices. This allows
68	overriding the default of pfifo_fast with an alternative. Since the default
69	queuing discipline is created without additional parameters so is best suited
70	to queuing disciplines that work well without configuration like stochastic
71	fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
72	queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
73	which require setting up classes and bandwidths. Note that physical multiqueue
74	interfaces still use mq as root qdisc, which in turn uses this default for its
75	leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
76	default to noqueue.
77	Default: pfifo_fast
78	
79	busy_read
80	----------------
81	Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
82	Approximate time in us to busy loop waiting for packets on the device queue.
83	This sets the default value of the SO_BUSY_POLL socket option.
84	Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
85	which is the preferred method of enabling. If you need to enable the feature
86	globally via sysctl, a value of 50 is recommended.
87	Will increase power usage.
88	Default: 0 (off)
89	
90	busy_poll
91	----------------
92	Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
93	Approximate time in us to busy loop waiting for events.
94	Recommended value depends on the number of sockets you poll on.
95	For several sockets 50, for several hundreds 100.
96	For more than that you probably want to use epoll.
97	Note that only sockets with SO_BUSY_POLL set will be busy polled,
98	so you want to either selectively set SO_BUSY_POLL on those sockets or set
99	sysctl.net.busy_read globally.
100	Will increase power usage.
101	Default: 0 (off)
102	
103	rmem_default
104	------------
105	
106	The default setting of the socket receive buffer in bytes.
107	
108	rmem_max
109	--------
110	
111	The maximum receive socket buffer size in bytes.
112	
113	tstamp_allow_data
114	-----------------
115	Allow processes to receive tx timestamps looped together with the original
116	packet contents. If disabled, transmit timestamp requests from unprivileged
117	processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
118	Default: 1 (on)
119	
120	
121	wmem_default
122	------------
123	
124	The default setting (in bytes) of the socket send buffer.
125	
126	wmem_max
127	--------
128	
129	The maximum send socket buffer size in bytes.
130	
131	message_burst and message_cost
132	------------------------------
133	
134	These parameters  are used to limit the warning messages written to the kernel
135	log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
136	denial-of-service attack  impossible. A higher message_cost factor, results in
137	fewer messages that will be written. Message_burst controls when messages will
138	be dropped.  The  default  settings  limit  warning messages to one every five
139	seconds.
140	
141	warnings
142	--------
143	
144	This sysctl is now unused.
145	
146	This was used to control console messages from the networking stack that
147	occur because of problems on the network like duplicate address or bad
148	checksums.
149	
150	These messages are now emitted at KERN_DEBUG and can generally be enabled
151	and controlled by the dynamic_debug facility.
152	
153	netdev_budget
154	-------------
155	
156	Maximum number of packets taken from all interfaces in one polling cycle (NAPI
157	poll). In one polling cycle interfaces which are registered to polling are
158	probed in a round-robin manner.
159	
160	netdev_max_backlog
161	------------------
162	
163	Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
164	receives packets faster than kernel can process them.
165	
166	netdev_rss_key
167	--------------
168	
169	RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
170	randomly generated.
171	Some user space might need to gather its content even if drivers do not
172	provide ethtool -x support yet.
173	
174	myhost:~# cat /proc/sys/net/core/netdev_rss_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: ... (52 bytes total)
176	
177	File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
178	Note:
179	/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
180	but most drivers only use 40 bytes of it.
181	
182	myhost:~# ethtool -x eth0
183	RX flow hash indirection table for eth0 with 8 RX ring(s):
184	    0:    0     1     2     3     4     5     6     7
185	RSS hash key:
186	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
187	
188	netdev_tstamp_prequeue
189	----------------------
190	
191	If set to 0, RX packet timestamps can be sampled after RPS processing, when
192	the target CPU processes packets. It might give some delay on timestamps, but
193	permit to distribute the load on several cpus.
194	
195	If set to 1 (default), timestamps are sampled as soon as possible, before
196	queueing.
197	
198	optmem_max
199	----------
200	
201	Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
202	of struct cmsghdr structures with appended data.
203	
204	2. /proc/sys/net/unix - Parameters for Unix domain sockets
205	-------------------------------------------------------
206	
207	There is only one file in this directory.
208	unix_dgram_qlen limits the max number of datagrams queued in Unix domain
209	socket's buffer. It will not take effect unless PF_UNIX flag is specified.
210	
211	
212	3. /proc/sys/net/ipv4 - IPV4 settings
213	-------------------------------------------------------
214	Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
215	descriptions of these entries.
216	
217	
218	4. Appletalk
219	-------------------------------------------------------
220	
221	The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
222	when Appletalk is loaded. The configurable parameters are:
223	
224	aarp-expiry-time
225	----------------
226	
227	The amount  of  time  we keep an ARP entry before expiring it. Used to age out
228	old hosts.
229	
230	aarp-resolve-time
231	-----------------
232	
233	The amount of time we will spend trying to resolve an Appletalk address.
234	
235	aarp-retransmit-limit
236	---------------------
237	
238	The number of times we will retransmit a query before giving up.
239	
240	aarp-tick-time
241	--------------
242	
243	Controls the rate at which expires are checked.
244	
245	The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
246	on a machine.
247	
248	The fields  indicate  the DDP type, the local address (in network:node format)
249	the remote  address,  the  size of the transmit pending queue, the size of the
250	received queue  (bytes waiting for applications to read) the state and the uid
251	owning the socket.
252	
253	/proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
254	shows the  name  of the interface, its Appletalk address, the network range on
255	that address  (or  network number for phase 1 networks), and the status of the
256	interface.
257	
258	/proc/net/atalk_route lists  each  known  network  route.  It lists the target
259	(network) that the route leads to, the router (may be directly connected), the
260	route flags, and the device the route is using.
261	
262	
263	5. IPX
264	-------------------------------------------------------
265	
266	The IPX protocol has no tunable values in proc/sys/net.
267	
268	The IPX  protocol  does,  however,  provide  proc/net/ipx. This lists each IPX
269	socket giving  the  local  and  remote  addresses  in  Novell  format (that is
270	network:node:port). In  accordance  with  the  strange  Novell  tradition,
271	everything but the port is in hex. Not_Connected is displayed for sockets that
272	are not  tied to a specific remote address. The Tx and Rx queue sizes indicate
273	the number  of  bytes  pending  for  transmission  and  reception.  The  state
274	indicates the  state  the  socket  is  in and the uid is the owning uid of the
275	socket.
276	
277	The /proc/net/ipx_interface  file lists all IPX interfaces. For each interface
278	it gives  the network number, the node number, and indicates if the network is
279	the primary  network.  It  also  indicates  which  device  it  is bound to (or
280	Internal for  internal  networks)  and  the  Frame  Type if appropriate. Linux
281	supports 802.3,  802.2,  802.2  SNAP  and DIX (Blue Book) ethernet framing for
282	IPX.
283	
284	The /proc/net/ipx_route  table  holds  a list of IPX routes. For each route it
285	gives the  destination  network, the router node (or Directly) and the network
286	address of the router (or Connected) for internal networks.
287	
288	6. TIPC
289	-------------------------------------------------------
290	
291	tipc_rmem
292	----------
293	
294	The TIPC protocol now has a tunable for the receive memory, similar to the
295	tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
296	
297	    # cat /proc/sys/net/tipc/tipc_rmem
298	    4252725 34021800        68043600
299	    #
300	
301	The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
302	are scaled (shifted) versions of that same value.  Note that the min value
303	is not at this point in time used in any meaningful way, but the triplet is
304	preserved in order to be consistent with things like tcp_rmem.
305	
306	named_timeout
307	--------------
308	
309	TIPC name table updates are distributed asynchronously in a cluster, without
310	any form of transaction handling. This means that different race scenarios are
311	possible. One such is that a name withdrawal sent out by one node and received
312	by another node may arrive after a second, overlapping name publication already
313	has been accepted from a third node, although the conflicting updates
314	originally may have been issued in the correct sequential order.
315	If named_timeout is nonzero, failed topology updates will be placed on a defer
316	queue until another event arrives that clears the error, or until the timeout
317	expires. Value is in milliseconds.
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