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Based on kernel version 3.19. Page generated on 2015-02-13 21:22 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	wmem_default
101	------------
102	
103	The default setting (in bytes) of the socket send buffer.
104	
105	wmem_max
106	--------
107	
108	The maximum send socket buffer size in bytes.
109	
110	message_burst and message_cost
111	------------------------------
112	
113	These parameters  are used to limit the warning messages written to the kernel
114	log from  the  networking  code.  They  enforce  a  rate  limit  to  make  a
115	denial-of-service attack  impossible. A higher message_cost factor, results in
116	fewer messages that will be written. Message_burst controls when messages will
117	be dropped.  The  default  settings  limit  warning messages to one every five
118	seconds.
119	
120	warnings
121	--------
122	
123	This sysctl is now unused.
124	
125	This was used to control console messages from the networking stack that
126	occur because of problems on the network like duplicate address or bad
127	checksums.
128	
129	These messages are now emitted at KERN_DEBUG and can generally be enabled
130	and controlled by the dynamic_debug facility.
131	
132	netdev_budget
133	-------------
134	
135	Maximum number of packets taken from all interfaces in one polling cycle (NAPI
136	poll). In one polling cycle interfaces which are registered to polling are
137	probed in a round-robin manner.
138	
139	netdev_max_backlog
140	------------------
141	
142	Maximum number  of  packets,  queued  on  the  INPUT  side, when the interface
143	receives packets faster than kernel can process them.
144	
145	netdev_rss_key
146	--------------
147	
148	RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
149	randomly generated.
150	Some user space might need to gather its content even if drivers do not
151	provide ethtool -x support yet.
152	
153	myhost:~# cat /proc/sys/net/core/netdev_rss_key
154	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)
155	
156	File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
157	Note:
158	/proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
159	but most drivers only use 40 bytes of it.
160	
161	myhost:~# ethtool -x eth0
162	RX flow hash indirection table for eth0 with 8 RX ring(s):
163	    0:    0     1     2     3     4     5     6     7
164	RSS hash key:
165	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
166	
167	netdev_tstamp_prequeue
168	----------------------
169	
170	If set to 0, RX packet timestamps can be sampled after RPS processing, when
171	the target CPU processes packets. It might give some delay on timestamps, but
172	permit to distribute the load on several cpus.
173	
174	If set to 1 (default), timestamps are sampled as soon as possible, before
175	queueing.
176	
177	optmem_max
178	----------
179	
180	Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
181	of struct cmsghdr structures with appended data.
182	
183	2. /proc/sys/net/unix - Parameters for Unix domain sockets
184	-------------------------------------------------------
185	
186	There is only one file in this directory.
187	unix_dgram_qlen limits the max number of datagrams queued in Unix domain
188	socket's buffer. It will not take effect unless PF_UNIX flag is specified.
189	
190	
191	3. /proc/sys/net/ipv4 - IPV4 settings
192	-------------------------------------------------------
193	Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
194	descriptions of these entries.
195	
196	
197	4. Appletalk
198	-------------------------------------------------------
199	
200	The /proc/sys/net/appletalk  directory  holds the Appletalk configuration data
201	when Appletalk is loaded. The configurable parameters are:
202	
203	aarp-expiry-time
204	----------------
205	
206	The amount  of  time  we keep an ARP entry before expiring it. Used to age out
207	old hosts.
208	
209	aarp-resolve-time
210	-----------------
211	
212	The amount of time we will spend trying to resolve an Appletalk address.
213	
214	aarp-retransmit-limit
215	---------------------
216	
217	The number of times we will retransmit a query before giving up.
218	
219	aarp-tick-time
220	--------------
221	
222	Controls the rate at which expires are checked.
223	
224	The directory  /proc/net/appletalk  holds the list of active Appletalk sockets
225	on a machine.
226	
227	The fields  indicate  the DDP type, the local address (in network:node format)
228	the remote  address,  the  size of the transmit pending queue, the size of the
229	received queue  (bytes waiting for applications to read) the state and the uid
230	owning the socket.
231	
232	/proc/net/atalk_iface lists  all  the  interfaces  configured for appletalk.It
233	shows the  name  of the interface, its Appletalk address, the network range on
234	that address  (or  network number for phase 1 networks), and the status of the
235	interface.
236	
237	/proc/net/atalk_route lists  each  known  network  route.  It lists the target
238	(network) that the route leads to, the router (may be directly connected), the
239	route flags, and the device the route is using.
240	
241	
242	5. IPX
243	-------------------------------------------------------
244	
245	The IPX protocol has no tunable values in proc/sys/net.
246	
247	The IPX  protocol  does,  however,  provide  proc/net/ipx. This lists each IPX
248	socket giving  the  local  and  remote  addresses  in  Novell  format (that is
249	network:node:port). In  accordance  with  the  strange  Novell  tradition,
250	everything but the port is in hex. Not_Connected is displayed for sockets that
251	are not  tied to a specific remote address. The Tx and Rx queue sizes indicate
252	the number  of  bytes  pending  for  transmission  and  reception.  The  state
253	indicates the  state  the  socket  is  in and the uid is the owning uid of the
254	socket.
255	
256	The /proc/net/ipx_interface  file lists all IPX interfaces. For each interface
257	it gives  the network number, the node number, and indicates if the network is
258	the primary  network.  It  also  indicates  which  device  it  is bound to (or
259	Internal for  internal  networks)  and  the  Frame  Type if appropriate. Linux
260	supports 802.3,  802.2,  802.2  SNAP  and DIX (Blue Book) ethernet framing for
261	IPX.
262	
263	The /proc/net/ipx_route  table  holds  a list of IPX routes. For each route it
264	gives the  destination  network, the router node (or Directly) and the network
265	address of the router (or Connected) for internal networks.
266	
267	6. TIPC
268	-------------------------------------------------------
269	
270	tipc_rmem
271	----------
272	
273	The TIPC protocol now has a tunable for the receive memory, similar to the
274	tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
275	
276	    # cat /proc/sys/net/tipc/tipc_rmem
277	    4252725 34021800        68043600
278	    #
279	
280	The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
281	are scaled (shifted) versions of that same value.  Note that the min value
282	is not at this point in time used in any meaningful way, but the triplet is
283	preserved in order to be consistent with things like tcp_rmem.
284	
285	named_timeout
286	--------------
287	
288	TIPC name table updates are distributed asynchronously in a cluster, without
289	any form of transaction handling. This means that different race scenarios are
290	possible. One such is that a name withdrawal sent out by one node and received
291	by another node may arrive after a second, overlapping name publication already
292	has been accepted from a third node, although the conflicting updates
293	originally may have been issued in the correct sequential order.
294	If named_timeout is nonzero, failed topology updates will be placed on a defer
295	queue until another event arrives that clears the error, or until the timeout
296	expires. Value is in milliseconds.
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