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faa5273c | 1 | Documentation for /proc/sys/net/* |
760df93e SF |
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 | |
faa5273c | 12 | /proc/sys/net |
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13 | |
14 | The interface to the networking parts of the kernel is located in | |
faa5273c | 15 | /proc/sys/net. The following table shows all possible subdirectories. You may |
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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 | |
cc79dd1b | 29 | ipv6 IP version 6 tipc TIPC |
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30 | .............................................................................. |
31 | ||
32 | 1. /proc/sys/net/core - Network core options | |
33 | ------------------------------------------------------- | |
34 | ||
0a14842f ED |
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 | ||
4f3446bb DB |
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 | ||
c60f6aa8 SW |
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 | ||
6da7c8fc | 64 | default_qdisc |
65 | -------------- | |
66 | ||
67 | The default queuing discipline to use for network devices. This allows | |
2e64126b PS |
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. | |
6da7c8fc | 77 | Default: pfifo_fast |
78 | ||
64b0dc51 | 79 | busy_read |
06021292 | 80 | ---------------- |
e0d1095a | 81 | Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL) |
cbf55001 | 82 | Approximate time in us to busy loop waiting for packets on the device queue. |
64b0dc51 ET |
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. | |
cbf55001 | 87 | Will increase power usage. |
06021292 ET |
88 | Default: 0 (off) |
89 | ||
64b0dc51 | 90 | busy_poll |
2d48d67f | 91 | ---------------- |
e0d1095a | 92 | Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL) |
cbf55001 | 93 | Approximate time in us to busy loop waiting for events. |
2d48d67f ET |
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. | |
64b0dc51 ET |
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. | |
cbf55001 | 100 | Will increase power usage. |
2d48d67f ET |
101 | Default: 0 (off) |
102 | ||
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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 | ||
b245be1f WB |
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 | ||
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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 | ||
ba7a46f1 JP |
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. | |
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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 | |
3cc7587b | 158 | probed in a round-robin manner. |
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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 | ||
960fb622 ED |
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 | ||
3b098e2d ED |
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 | ||
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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 | ||
45dad7bd LX |
207 | There is only one file in this directory. |
208 | unix_dgram_qlen limits the max number of datagrams queued in Unix domain | |
ca8b9950 | 209 | socket's buffer. It will not take effect unless PF_UNIX flag is specified. |
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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. | |
cc79dd1b YX |
287 | |
288 | 6. TIPC | |
289 | ------------------------------------------------------- | |
290 | ||
a5325ae5 EH |
291 | tipc_rmem |
292 | ---------- | |
293 | ||
cc79dd1b YX |
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. | |
a5325ae5 EH |
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. |