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Based on kernel version 4.1. Page generated on 2015-06-28 12:14 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 queue discipline of pfifo_fast with an
58	alternative. Since the default queuing discipline is created with the
59	no additional parameters so is best suited to queuing disciplines that
60	work well without configuration like stochastic fair queue (sfq),
61	CoDel (codel) or fair queue CoDel (fq_codel). Don't use queuing disciplines
62	like Hierarchical Token Bucket or Deficit Round Robin which require setting
63	up classes and bandwidths.
64	Default: pfifo_fast
65	
66	busy_read
67	----------------
68	Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
69	Approximate time in us to busy loop waiting for packets on the device queue.
70	This sets the default value of the SO_BUSY_POLL socket option.
71	Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
72	which is the preferred method of enabling. If you need to enable the feature
73	globally via sysctl, a value of 50 is recommended.
74	Will increase power usage.
75	Default: 0 (off)
76	
77	busy_poll
78	----------------
79	Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
80	Approximate time in us to busy loop waiting for events.
81	Recommended value depends on the number of sockets you poll on.
82	For several sockets 50, for several hundreds 100.
83	For more than that you probably want to use epoll.
84	Note that only sockets with SO_BUSY_POLL set will be busy polled,
85	so you want to either selectively set SO_BUSY_POLL on those sockets or set
86	sysctl.net.busy_read globally.
87	Will increase power usage.
88	Default: 0 (off)
89	
90	rmem_default
91	------------
92	
93	The default setting of the socket receive buffer in bytes.
94	
95	rmem_max
96	--------
97	
98	The maximum receive socket buffer size in bytes.
99	
100	tstamp_allow_data
101	-----------------
102	Allow processes to receive tx timestamps looped together with the original
103	packet contents. If disabled, transmit timestamp requests from unprivileged
104	processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
105	Default: 1 (on)
106	
107	
108	wmem_default
109	------------
110	
111	The default setting (in bytes) of the socket send buffer.
112	
113	wmem_max
114	--------
115	
116	The maximum send socket buffer size in bytes.
117	
118	message_burst and message_cost
119	------------------------------
120	
121	These parameters  are used to limit the warning messages written to the kernel
122	log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
123	denial-of-service attack  impossible. A higher message_cost factor, results in
124	fewer messages that will be written. Message_burst controls when messages will
125	be dropped.  The  default  settings  limit  warning messages to one every five
126	seconds.
127	
128	warnings
129	--------
130	
131	This sysctl is now unused.
132	
133	This was used to control console messages from the networking stack that
134	occur because of problems on the network like duplicate address or bad
135	checksums.
136	
137	These messages are now emitted at KERN_DEBUG and can generally be enabled
138	and controlled by the dynamic_debug facility.
139	
140	netdev_budget
141	-------------
142	
143	Maximum number of packets taken from all interfaces in one polling cycle (NAPI
144	poll). In one polling cycle interfaces which are registered to polling are
145	probed in a round-robin manner.
146	
147	netdev_max_backlog
148	------------------
149	
150	Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
151	receives packets faster than kernel can process them.
152	
153	netdev_rss_key
154	--------------
155	
156	RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
157	randomly generated.
158	Some user space might need to gather its content even if drivers do not
159	provide ethtool -x support yet.
160	
161	myhost:~# cat /proc/sys/net/core/netdev_rss_key
162	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)
163	
164	File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
165	Note:
166	/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
167	but most drivers only use 40 bytes of it.
168	
169	myhost:~# ethtool -x eth0
170	RX flow hash indirection table for eth0 with 8 RX ring(s):
171	    0:    0     1     2     3     4     5     6     7
172	RSS hash key:
173	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
174	
175	netdev_tstamp_prequeue
176	----------------------
177	
178	If set to 0, RX packet timestamps can be sampled after RPS processing, when
179	the target CPU processes packets. It might give some delay on timestamps, but
180	permit to distribute the load on several cpus.
181	
182	If set to 1 (default), timestamps are sampled as soon as possible, before
183	queueing.
184	
185	optmem_max
186	----------
187	
188	Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
189	of struct cmsghdr structures with appended data.
190	
191	2. /proc/sys/net/unix - Parameters for Unix domain sockets
192	-------------------------------------------------------
193	
194	There is only one file in this directory.
195	unix_dgram_qlen limits the max number of datagrams queued in Unix domain
196	socket's buffer. It will not take effect unless PF_UNIX flag is specified.
197	
198	
199	3. /proc/sys/net/ipv4 - IPV4 settings
200	-------------------------------------------------------
201	Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
202	descriptions of these entries.
203	
204	
205	4. Appletalk
206	-------------------------------------------------------
207	
208	The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
209	when Appletalk is loaded. The configurable parameters are:
210	
211	aarp-expiry-time
212	----------------
213	
214	The amount  of  time  we keep an ARP entry before expiring it. Used to age out
215	old hosts.
216	
217	aarp-resolve-time
218	-----------------
219	
220	The amount of time we will spend trying to resolve an Appletalk address.
221	
222	aarp-retransmit-limit
223	---------------------
224	
225	The number of times we will retransmit a query before giving up.
226	
227	aarp-tick-time
228	--------------
229	
230	Controls the rate at which expires are checked.
231	
232	The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
233	on a machine.
234	
235	The fields  indicate  the DDP type, the local address (in network:node format)
236	the remote  address,  the  size of the transmit pending queue, the size of the
237	received queue  (bytes waiting for applications to read) the state and the uid
238	owning the socket.
239	
240	/proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
241	shows the  name  of the interface, its Appletalk address, the network range on
242	that address  (or  network number for phase 1 networks), and the status of the
243	interface.
244	
245	/proc/net/atalk_route lists  each  known  network  route.  It lists the target
246	(network) that the route leads to, the router (may be directly connected), the
247	route flags, and the device the route is using.
248	
249	
250	5. IPX
251	-------------------------------------------------------
252	
253	The IPX protocol has no tunable values in proc/sys/net.
254	
255	The IPX  protocol  does,  however,  provide  proc/net/ipx. This lists each IPX
256	socket giving  the  local  and  remote  addresses  in  Novell  format (that is
257	network:node:port). In  accordance  with  the  strange  Novell  tradition,
258	everything but the port is in hex. Not_Connected is displayed for sockets that
259	are not  tied to a specific remote address. The Tx and Rx queue sizes indicate
260	the number  of  bytes  pending  for  transmission  and  reception.  The  state
261	indicates the  state  the  socket  is  in and the uid is the owning uid of the
262	socket.
263	
264	The /proc/net/ipx_interface  file lists all IPX interfaces. For each interface
265	it gives  the network number, the node number, and indicates if the network is
266	the primary  network.  It  also  indicates  which  device  it  is bound to (or
267	Internal for  internal  networks)  and  the  Frame  Type if appropriate. Linux
268	supports 802.3,  802.2,  802.2  SNAP  and DIX (Blue Book) ethernet framing for
269	IPX.
270	
271	The /proc/net/ipx_route  table  holds  a list of IPX routes. For each route it
272	gives the  destination  network, the router node (or Directly) and the network
273	address of the router (or Connected) for internal networks.
274	
275	6. TIPC
276	-------------------------------------------------------
277	
278	tipc_rmem
279	----------
280	
281	The TIPC protocol now has a tunable for the receive memory, similar to the
282	tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
283	
284	    # cat /proc/sys/net/tipc/tipc_rmem
285	    4252725 34021800        68043600
286	    #
287	
288	The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
289	are scaled (shifted) versions of that same value.  Note that the min value
290	is not at this point in time used in any meaningful way, but the triplet is
291	preserved in order to be consistent with things like tcp_rmem.
292	
293	named_timeout
294	--------------
295	
296	TIPC name table updates are distributed asynchronously in a cluster, without
297	any form of transaction handling. This means that different race scenarios are
298	possible. One such is that a name withdrawal sent out by one node and received
299	by another node may arrive after a second, overlapping name publication already
300	has been accepted from a third node, although the conflicting updates
301	originally may have been issued in the correct sequential order.
302	If named_timeout is nonzero, failed topology updates will be placed on a defer
303	queue until another event arrives that clears the error, or until the timeout
304	expires. Value is in milliseconds.
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