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>
7 For general info and legal blurb, please look in README.
9 ==============================================================
11 This file contains the documentation for the sysctl files in
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.
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 ..............................................................................
32 1. /proc/sys/net/core - Network core options
33 -------------------------------------------------------
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.
42 0 - disable the JIT (default value)
44 2 - enable the JIT and ask the compiler to emit traces on kernel log.
49 The maximum number of packets that kernel can handle on a NAPI interrupt,
50 it's a Per-CPU variable.
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.
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.
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.
93 The default setting of the socket receive buffer in bytes.
98 The maximum receive socket buffer size in bytes.
103 The default setting (in bytes) of the socket send buffer.
108 The maximum send socket buffer size in bytes.
110 message_burst and message_cost
111 ------------------------------
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
123 This sysctl is now unused.
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
129 These messages are now emitted at KERN_DEBUG and can generally be enabled
130 and controlled by the dynamic_debug facility.
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.
142 Maximum number of packets, queued on the INPUT side, when the interface
143 receives packets faster than kernel can process them.
145 netdev_tstamp_prequeue
146 ----------------------
148 If set to 0, RX packet timestamps can be sampled after RPS processing, when
149 the target CPU processes packets. It might give some delay on timestamps, but
150 permit to distribute the load on several cpus.
152 If set to 1 (default), timestamps are sampled as soon as possible, before
158 Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
159 of struct cmsghdr structures with appended data.
161 2. /proc/sys/net/unix - Parameters for Unix domain sockets
162 -------------------------------------------------------
164 There is only one file in this directory.
165 unix_dgram_qlen limits the max number of datagrams queued in Unix domain
166 socket's buffer. It will not take effect unless PF_UNIX flag is specified.
169 3. /proc/sys/net/ipv4 - IPV4 settings
170 -------------------------------------------------------
171 Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for
172 descriptions of these entries.
176 -------------------------------------------------------
178 The /proc/sys/net/appletalk directory holds the Appletalk configuration data
179 when Appletalk is loaded. The configurable parameters are:
184 The amount of time we keep an ARP entry before expiring it. Used to age out
190 The amount of time we will spend trying to resolve an Appletalk address.
192 aarp-retransmit-limit
193 ---------------------
195 The number of times we will retransmit a query before giving up.
200 Controls the rate at which expires are checked.
202 The directory /proc/net/appletalk holds the list of active Appletalk sockets
205 The fields indicate the DDP type, the local address (in network:node format)
206 the remote address, the size of the transmit pending queue, the size of the
207 received queue (bytes waiting for applications to read) the state and the uid
210 /proc/net/atalk_iface lists all the interfaces configured for appletalk.It
211 shows the name of the interface, its Appletalk address, the network range on
212 that address (or network number for phase 1 networks), and the status of the
215 /proc/net/atalk_route lists each known network route. It lists the target
216 (network) that the route leads to, the router (may be directly connected), the
217 route flags, and the device the route is using.
221 -------------------------------------------------------
223 The IPX protocol has no tunable values in proc/sys/net.
225 The IPX protocol does, however, provide proc/net/ipx. This lists each IPX
226 socket giving the local and remote addresses in Novell format (that is
227 network:node:port). In accordance with the strange Novell tradition,
228 everything but the port is in hex. Not_Connected is displayed for sockets that
229 are not tied to a specific remote address. The Tx and Rx queue sizes indicate
230 the number of bytes pending for transmission and reception. The state
231 indicates the state the socket is in and the uid is the owning uid of the
234 The /proc/net/ipx_interface file lists all IPX interfaces. For each interface
235 it gives the network number, the node number, and indicates if the network is
236 the primary network. It also indicates which device it is bound to (or
237 Internal for internal networks) and the Frame Type if appropriate. Linux
238 supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for
241 The /proc/net/ipx_route table holds a list of IPX routes. For each route it
242 gives the destination network, the router node (or Directly) and the network
243 address of the router (or Connected) for internal networks.
246 -------------------------------------------------------
251 The TIPC protocol now has a tunable for the receive memory, similar to the
252 tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
254 # cat /proc/sys/net/tipc/tipc_rmem
255 4252725 34021800 68043600
258 The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
259 are scaled (shifted) versions of that same value. Note that the min value
260 is not at this point in time used in any meaningful way, but the triplet is
261 preserved in order to be consistent with things like tcp_rmem.
266 TIPC name table updates are distributed asynchronously in a cluster, without
267 any form of transaction handling. This means that different race scenarios are
268 possible. One such is that a name withdrawal sent out by one node and received
269 by another node may arrive after a second, overlapping name publication already
270 has been accepted from a third node, although the conflicting updates
271 originally may have been issued in the correct sequential order.
272 If named_timeout is nonzero, failed topology updates will be placed on a defer
273 queue until another event arrives that clears the error, or until the timeout
274 expires. Value is in milliseconds.