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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 |
760df93e SF |
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 |
760df93e SF |
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 | ||
2110ba58 DB |
38 | This enables the BPF Just in Time (JIT) compiler. BPF is a flexible |
39 | and efficient infrastructure allowing to execute bytecode at various | |
40 | hook points. It is used in a number of Linux kernel subsystems such | |
41 | as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints) | |
42 | and security (e.g. seccomp). LLVM has a BPF back end that can compile | |
43 | restricted C into a sequence of BPF instructions. After program load | |
44 | through bpf(2) and passing a verifier in the kernel, a JIT will then | |
45 | translate these BPF proglets into native CPU instructions. There are | |
46 | two flavors of JITs, the newer eBPF JIT currently supported on: | |
014cd0a3 ME |
47 | - x86_64 |
48 | - arm64 | |
d2aaa3dc | 49 | - arm32 |
014cd0a3 ME |
50 | - ppc64 |
51 | - sparc64 | |
52 | - mips64 | |
d4dd2d75 | 53 | - s390x |
014cd0a3 | 54 | |
2110ba58 | 55 | And the older cBPF JIT supported on the following archs: |
014cd0a3 ME |
56 | - mips |
57 | - ppc | |
58 | - sparc | |
59 | ||
2110ba58 DB |
60 | eBPF JITs are a superset of cBPF JITs, meaning the kernel will |
61 | migrate cBPF instructions into eBPF instructions and then JIT | |
62 | compile them transparently. Older cBPF JITs can only translate | |
63 | tcpdump filters, seccomp rules, etc, but not mentioned eBPF | |
64 | programs loaded through bpf(2). | |
014cd0a3 | 65 | |
0a14842f ED |
66 | Values : |
67 | 0 - disable the JIT (default value) | |
68 | 1 - enable the JIT | |
69 | 2 - enable the JIT and ask the compiler to emit traces on kernel log. | |
70 | ||
4f3446bb DB |
71 | bpf_jit_harden |
72 | -------------- | |
73 | ||
2110ba58 DB |
74 | This enables hardening for the BPF JIT compiler. Supported are eBPF |
75 | JIT backends. Enabling hardening trades off performance, but can | |
76 | mitigate JIT spraying. | |
4f3446bb DB |
77 | Values : |
78 | 0 - disable JIT hardening (default value) | |
79 | 1 - enable JIT hardening for unprivileged users only | |
80 | 2 - enable JIT hardening for all users | |
81 | ||
74451e66 DB |
82 | bpf_jit_kallsyms |
83 | ---------------- | |
84 | ||
2110ba58 DB |
85 | When BPF JIT compiler is enabled, then compiled images are unknown |
86 | addresses to the kernel, meaning they neither show up in traces nor | |
87 | in /proc/kallsyms. This enables export of these addresses, which can | |
88 | be used for debugging/tracing. If bpf_jit_harden is enabled, this | |
89 | feature is disabled. | |
74451e66 DB |
90 | Values : |
91 | 0 - disable JIT kallsyms export (default value) | |
92 | 1 - enable JIT kallsyms export for privileged users only | |
93 | ||
c60f6aa8 SW |
94 | dev_weight |
95 | -------------- | |
96 | ||
97 | The maximum number of packets that kernel can handle on a NAPI interrupt, | |
98 | it's a Per-CPU variable. | |
99 | Default: 64 | |
100 | ||
3d48b53f MT |
101 | dev_weight_rx_bias |
102 | -------------- | |
103 | ||
104 | RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function | |
105 | of the driver for the per softirq cycle netdev_budget. This parameter influences | |
106 | the proportion of the configured netdev_budget that is spent on RPS based packet | |
107 | processing during RX softirq cycles. It is further meant for making current | |
108 | dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack. | |
109 | (see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based | |
110 | on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias). | |
111 | Default: 1 | |
112 | ||
113 | dev_weight_tx_bias | |
114 | -------------- | |
115 | ||
116 | Scales the maximum number of packets that can be processed during a TX softirq cycle. | |
117 | Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric | |
118 | net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog. | |
119 | Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias). | |
120 | Default: 1 | |
121 | ||
6da7c8fc | 122 | default_qdisc |
123 | -------------- | |
124 | ||
125 | The default queuing discipline to use for network devices. This allows | |
2e64126b PS |
126 | overriding the default of pfifo_fast with an alternative. Since the default |
127 | queuing discipline is created without additional parameters so is best suited | |
128 | to queuing disciplines that work well without configuration like stochastic | |
129 | fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use | |
130 | queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin | |
131 | which require setting up classes and bandwidths. Note that physical multiqueue | |
132 | interfaces still use mq as root qdisc, which in turn uses this default for its | |
133 | leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead | |
134 | default to noqueue. | |
6da7c8fc | 135 | Default: pfifo_fast |
136 | ||
64b0dc51 | 137 | busy_read |
06021292 | 138 | ---------------- |
e0d1095a | 139 | Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL) |
cbf55001 | 140 | Approximate time in us to busy loop waiting for packets on the device queue. |
64b0dc51 ET |
141 | This sets the default value of the SO_BUSY_POLL socket option. |
142 | Can be set or overridden per socket by setting socket option SO_BUSY_POLL, | |
143 | which is the preferred method of enabling. If you need to enable the feature | |
144 | globally via sysctl, a value of 50 is recommended. | |
cbf55001 | 145 | Will increase power usage. |
06021292 ET |
146 | Default: 0 (off) |
147 | ||
64b0dc51 | 148 | busy_poll |
2d48d67f | 149 | ---------------- |
e0d1095a | 150 | Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL) |
cbf55001 | 151 | Approximate time in us to busy loop waiting for events. |
2d48d67f ET |
152 | Recommended value depends on the number of sockets you poll on. |
153 | For several sockets 50, for several hundreds 100. | |
154 | For more than that you probably want to use epoll. | |
64b0dc51 ET |
155 | Note that only sockets with SO_BUSY_POLL set will be busy polled, |
156 | so you want to either selectively set SO_BUSY_POLL on those sockets or set | |
157 | sysctl.net.busy_read globally. | |
cbf55001 | 158 | Will increase power usage. |
2d48d67f ET |
159 | Default: 0 (off) |
160 | ||
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161 | rmem_default |
162 | ------------ | |
163 | ||
164 | The default setting of the socket receive buffer in bytes. | |
165 | ||
166 | rmem_max | |
167 | -------- | |
168 | ||
169 | The maximum receive socket buffer size in bytes. | |
170 | ||
b245be1f WB |
171 | tstamp_allow_data |
172 | ----------------- | |
173 | Allow processes to receive tx timestamps looped together with the original | |
174 | packet contents. If disabled, transmit timestamp requests from unprivileged | |
175 | processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set. | |
176 | Default: 1 (on) | |
177 | ||
178 | ||
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179 | wmem_default |
180 | ------------ | |
181 | ||
182 | The default setting (in bytes) of the socket send buffer. | |
183 | ||
184 | wmem_max | |
185 | -------- | |
186 | ||
187 | The maximum send socket buffer size in bytes. | |
188 | ||
189 | message_burst and message_cost | |
190 | ------------------------------ | |
191 | ||
192 | These parameters are used to limit the warning messages written to the kernel | |
193 | log from the networking code. They enforce a rate limit to make a | |
194 | denial-of-service attack impossible. A higher message_cost factor, results in | |
195 | fewer messages that will be written. Message_burst controls when messages will | |
196 | be dropped. The default settings limit warning messages to one every five | |
197 | seconds. | |
198 | ||
199 | warnings | |
200 | -------- | |
201 | ||
ba7a46f1 JP |
202 | This sysctl is now unused. |
203 | ||
204 | This was used to control console messages from the networking stack that | |
205 | occur because of problems on the network like duplicate address or bad | |
206 | checksums. | |
207 | ||
208 | These messages are now emitted at KERN_DEBUG and can generally be enabled | |
209 | and controlled by the dynamic_debug facility. | |
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210 | |
211 | netdev_budget | |
212 | ------------- | |
213 | ||
214 | Maximum number of packets taken from all interfaces in one polling cycle (NAPI | |
215 | poll). In one polling cycle interfaces which are registered to polling are | |
7acf8a1e MW |
216 | probed in a round-robin manner. Also, a polling cycle may not exceed |
217 | netdev_budget_usecs microseconds, even if netdev_budget has not been | |
218 | exhausted. | |
219 | ||
220 | netdev_budget_usecs | |
221 | --------------------- | |
222 | ||
223 | Maximum number of microseconds in one NAPI polling cycle. Polling | |
224 | will exit when either netdev_budget_usecs have elapsed during the | |
225 | poll cycle or the number of packets processed reaches netdev_budget. | |
760df93e SF |
226 | |
227 | netdev_max_backlog | |
228 | ------------------ | |
229 | ||
230 | Maximum number of packets, queued on the INPUT side, when the interface | |
231 | receives packets faster than kernel can process them. | |
232 | ||
960fb622 ED |
233 | netdev_rss_key |
234 | -------------- | |
235 | ||
236 | RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is | |
237 | randomly generated. | |
238 | Some user space might need to gather its content even if drivers do not | |
239 | provide ethtool -x support yet. | |
240 | ||
241 | myhost:~# cat /proc/sys/net/core/netdev_rss_key | |
242 | 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) | |
243 | ||
244 | File contains nul bytes if no driver ever called netdev_rss_key_fill() function. | |
245 | Note: | |
246 | /proc/sys/net/core/netdev_rss_key contains 52 bytes of key, | |
247 | but most drivers only use 40 bytes of it. | |
248 | ||
249 | myhost:~# ethtool -x eth0 | |
250 | RX flow hash indirection table for eth0 with 8 RX ring(s): | |
251 | 0: 0 1 2 3 4 5 6 7 | |
252 | RSS hash key: | |
253 | 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 | |
254 | ||
3b098e2d ED |
255 | netdev_tstamp_prequeue |
256 | ---------------------- | |
257 | ||
258 | If set to 0, RX packet timestamps can be sampled after RPS processing, when | |
259 | the target CPU processes packets. It might give some delay on timestamps, but | |
260 | permit to distribute the load on several cpus. | |
261 | ||
262 | If set to 1 (default), timestamps are sampled as soon as possible, before | |
263 | queueing. | |
264 | ||
760df93e SF |
265 | optmem_max |
266 | ---------- | |
267 | ||
268 | Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence | |
269 | of struct cmsghdr structures with appended data. | |
270 | ||
271 | 2. /proc/sys/net/unix - Parameters for Unix domain sockets | |
272 | ------------------------------------------------------- | |
273 | ||
45dad7bd LX |
274 | There is only one file in this directory. |
275 | unix_dgram_qlen limits the max number of datagrams queued in Unix domain | |
ca8b9950 | 276 | socket's buffer. It will not take effect unless PF_UNIX flag is specified. |
760df93e SF |
277 | |
278 | ||
279 | 3. /proc/sys/net/ipv4 - IPV4 settings | |
280 | ------------------------------------------------------- | |
281 | Please see: Documentation/networking/ip-sysctl.txt and ipvs-sysctl.txt for | |
282 | descriptions of these entries. | |
283 | ||
284 | ||
285 | 4. Appletalk | |
286 | ------------------------------------------------------- | |
287 | ||
288 | The /proc/sys/net/appletalk directory holds the Appletalk configuration data | |
289 | when Appletalk is loaded. The configurable parameters are: | |
290 | ||
291 | aarp-expiry-time | |
292 | ---------------- | |
293 | ||
294 | The amount of time we keep an ARP entry before expiring it. Used to age out | |
295 | old hosts. | |
296 | ||
297 | aarp-resolve-time | |
298 | ----------------- | |
299 | ||
300 | The amount of time we will spend trying to resolve an Appletalk address. | |
301 | ||
302 | aarp-retransmit-limit | |
303 | --------------------- | |
304 | ||
305 | The number of times we will retransmit a query before giving up. | |
306 | ||
307 | aarp-tick-time | |
308 | -------------- | |
309 | ||
310 | Controls the rate at which expires are checked. | |
311 | ||
312 | The directory /proc/net/appletalk holds the list of active Appletalk sockets | |
313 | on a machine. | |
314 | ||
315 | The fields indicate the DDP type, the local address (in network:node format) | |
316 | the remote address, the size of the transmit pending queue, the size of the | |
317 | received queue (bytes waiting for applications to read) the state and the uid | |
318 | owning the socket. | |
319 | ||
320 | /proc/net/atalk_iface lists all the interfaces configured for appletalk.It | |
321 | shows the name of the interface, its Appletalk address, the network range on | |
322 | that address (or network number for phase 1 networks), and the status of the | |
323 | interface. | |
324 | ||
325 | /proc/net/atalk_route lists each known network route. It lists the target | |
326 | (network) that the route leads to, the router (may be directly connected), the | |
327 | route flags, and the device the route is using. | |
328 | ||
329 | ||
330 | 5. IPX | |
331 | ------------------------------------------------------- | |
332 | ||
333 | The IPX protocol has no tunable values in proc/sys/net. | |
334 | ||
335 | The IPX protocol does, however, provide proc/net/ipx. This lists each IPX | |
336 | socket giving the local and remote addresses in Novell format (that is | |
337 | network:node:port). In accordance with the strange Novell tradition, | |
338 | everything but the port is in hex. Not_Connected is displayed for sockets that | |
339 | are not tied to a specific remote address. The Tx and Rx queue sizes indicate | |
340 | the number of bytes pending for transmission and reception. The state | |
341 | indicates the state the socket is in and the uid is the owning uid of the | |
342 | socket. | |
343 | ||
344 | The /proc/net/ipx_interface file lists all IPX interfaces. For each interface | |
345 | it gives the network number, the node number, and indicates if the network is | |
346 | the primary network. It also indicates which device it is bound to (or | |
347 | Internal for internal networks) and the Frame Type if appropriate. Linux | |
348 | supports 802.3, 802.2, 802.2 SNAP and DIX (Blue Book) ethernet framing for | |
349 | IPX. | |
350 | ||
351 | The /proc/net/ipx_route table holds a list of IPX routes. For each route it | |
352 | gives the destination network, the router node (or Directly) and the network | |
353 | address of the router (or Connected) for internal networks. | |
cc79dd1b YX |
354 | |
355 | 6. TIPC | |
356 | ------------------------------------------------------- | |
357 | ||
a5325ae5 EH |
358 | tipc_rmem |
359 | ---------- | |
360 | ||
cc79dd1b YX |
361 | The TIPC protocol now has a tunable for the receive memory, similar to the |
362 | tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max) | |
363 | ||
364 | # cat /proc/sys/net/tipc/tipc_rmem | |
365 | 4252725 34021800 68043600 | |
366 | # | |
367 | ||
368 | The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values | |
369 | are scaled (shifted) versions of that same value. Note that the min value | |
370 | is not at this point in time used in any meaningful way, but the triplet is | |
371 | preserved in order to be consistent with things like tcp_rmem. | |
a5325ae5 EH |
372 | |
373 | named_timeout | |
374 | -------------- | |
375 | ||
376 | TIPC name table updates are distributed asynchronously in a cluster, without | |
377 | any form of transaction handling. This means that different race scenarios are | |
378 | possible. One such is that a name withdrawal sent out by one node and received | |
379 | by another node may arrive after a second, overlapping name publication already | |
380 | has been accepted from a third node, although the conflicting updates | |
381 | originally may have been issued in the correct sequential order. | |
382 | If named_timeout is nonzero, failed topology updates will be placed on a defer | |
383 | queue until another event arrives that clears the error, or until the timeout | |
384 | expires. Value is in milliseconds. |