1 ================================ 1 ================================
2 Documentation for /proc/sys/net/ 2 Documentation for /proc/sys/net/
3 ================================ 3 ================================
4 4
5 Copyright 5 Copyright
6 6
7 Copyright (c) 1999 7 Copyright (c) 1999
8 8
9 - Terrehon Bowden <terrehon@pacbell.net 9 - Terrehon Bowden <terrehon@pacbell.net>
10 - Bodo Bauer <bb@ricochet.net> 10 - Bodo Bauer <bb@ricochet.net>
11 11
12 Copyright (c) 2000 12 Copyright (c) 2000
13 13
14 - Jorge Nerin <comandante@zaralinux.com 14 - Jorge Nerin <comandante@zaralinux.com>
15 15
16 Copyright (c) 2009 16 Copyright (c) 2009
17 17
18 - Shen Feng <shen@cn.fujitsu.com> 18 - Shen Feng <shen@cn.fujitsu.com>
19 19
20 For general info and legal blurb, please look 20 For general info and legal blurb, please look in index.rst.
21 21
22 ---------------------------------------------- 22 ------------------------------------------------------------------------------
23 23
24 This file contains the documentation for the s 24 This file contains the documentation for the sysctl files in
25 /proc/sys/net 25 /proc/sys/net
26 26
27 The interface to the networking parts of 27 The interface to the networking parts of the kernel is located in
28 /proc/sys/net. The following table shows all p 28 /proc/sys/net. The following table shows all possible subdirectories. You may
29 see only some of them, depending on your kerne 29 see only some of them, depending on your kernel's configuration.
30 30
31 31
32 Table : Subdirectories in /proc/sys/net 32 Table : Subdirectories in /proc/sys/net
33 33
34 ========= =================== = ========== == 34 ========= =================== = ========== ===================
35 Directory Content Directory Co 35 Directory Content Directory Content
36 ========= =================== = ========== == 36 ========= =================== = ========== ===================
37 802 E802 protocol mptcp Mu 37 802 E802 protocol mptcp Multipath TCP
38 appletalk Appletalk protocol netfilter Ne 38 appletalk Appletalk protocol netfilter Network Filter
39 ax25 AX25 netrom NE 39 ax25 AX25 netrom NET/ROM
40 bridge Bridging rose X. 40 bridge Bridging rose X.25 PLP layer
41 core General parameter tipc TI 41 core General parameter tipc TIPC
42 ethernet Ethernet protocol unix Un 42 ethernet Ethernet protocol unix Unix domain sockets
43 ipv4 IP version 4 x25 X. 43 ipv4 IP version 4 x25 X.25 protocol
44 ipv6 IP version 6 44 ipv6 IP version 6
45 ========= =================== = ========== == 45 ========= =================== = ========== ===================
46 46
47 1. /proc/sys/net/core - Network core options 47 1. /proc/sys/net/core - Network core options
48 ============================================ 48 ============================================
49 49
50 bpf_jit_enable 50 bpf_jit_enable
51 -------------- 51 --------------
52 52
53 This enables the BPF Just in Time (JIT) compil 53 This enables the BPF Just in Time (JIT) compiler. BPF is a flexible
54 and efficient infrastructure allowing to execu 54 and efficient infrastructure allowing to execute bytecode at various
55 hook points. It is used in a number of Linux k 55 hook points. It is used in a number of Linux kernel subsystems such
56 as networking (e.g. XDP, tc), tracing (e.g. kp 56 as networking (e.g. XDP, tc), tracing (e.g. kprobes, uprobes, tracepoints)
57 and security (e.g. seccomp). LLVM has a BPF ba 57 and security (e.g. seccomp). LLVM has a BPF back end that can compile
58 restricted C into a sequence of BPF instructio 58 restricted C into a sequence of BPF instructions. After program load
59 through bpf(2) and passing a verifier in the k 59 through bpf(2) and passing a verifier in the kernel, a JIT will then
60 translate these BPF proglets into native CPU i 60 translate these BPF proglets into native CPU instructions. There are
61 two flavors of JITs, the newer eBPF JIT curren 61 two flavors of JITs, the newer eBPF JIT currently supported on:
62 62
63 - x86_64 63 - x86_64
64 - x86_32 64 - x86_32
65 - arm64 65 - arm64
66 - arm32 66 - arm32
67 - ppc64 67 - ppc64
68 - ppc32 68 - ppc32
69 - sparc64 69 - sparc64
70 - mips64 70 - mips64
71 - s390x 71 - s390x
72 - riscv64 72 - riscv64
73 - riscv32 73 - riscv32
74 - loongarch64 <<
75 - arc <<
76 74
77 And the older cBPF JIT supported on the follow 75 And the older cBPF JIT supported on the following archs:
78 76
79 - mips 77 - mips
80 - sparc 78 - sparc
81 79
82 eBPF JITs are a superset of cBPF JITs, meaning 80 eBPF JITs are a superset of cBPF JITs, meaning the kernel will
83 migrate cBPF instructions into eBPF instructio 81 migrate cBPF instructions into eBPF instructions and then JIT
84 compile them transparently. Older cBPF JITs ca 82 compile them transparently. Older cBPF JITs can only translate
85 tcpdump filters, seccomp rules, etc, but not m 83 tcpdump filters, seccomp rules, etc, but not mentioned eBPF
86 programs loaded through bpf(2). 84 programs loaded through bpf(2).
87 85
88 Values: 86 Values:
89 87
90 - 0 - disable the JIT (default value) 88 - 0 - disable the JIT (default value)
91 - 1 - enable the JIT 89 - 1 - enable the JIT
92 - 2 - enable the JIT and ask the compi 90 - 2 - enable the JIT and ask the compiler to emit traces on kernel log.
93 91
94 bpf_jit_harden 92 bpf_jit_harden
95 -------------- 93 --------------
96 94
97 This enables hardening for the BPF JIT compile 95 This enables hardening for the BPF JIT compiler. Supported are eBPF
98 JIT backends. Enabling hardening trades off pe 96 JIT backends. Enabling hardening trades off performance, but can
99 mitigate JIT spraying. 97 mitigate JIT spraying.
100 98
101 Values: 99 Values:
102 100
103 - 0 - disable JIT hardening (default v 101 - 0 - disable JIT hardening (default value)
104 - 1 - enable JIT hardening for unprivi 102 - 1 - enable JIT hardening for unprivileged users only
105 - 2 - enable JIT hardening for all use 103 - 2 - enable JIT hardening for all users
106 104
107 where "privileged user" in this context means 105 where "privileged user" in this context means a process having
108 CAP_BPF or CAP_SYS_ADMIN in the root user name 106 CAP_BPF or CAP_SYS_ADMIN in the root user name space.
109 107
110 bpf_jit_kallsyms 108 bpf_jit_kallsyms
111 ---------------- 109 ----------------
112 110
113 When BPF JIT compiler is enabled, then compile 111 When BPF JIT compiler is enabled, then compiled images are unknown
114 addresses to the kernel, meaning they neither 112 addresses to the kernel, meaning they neither show up in traces nor
115 in /proc/kallsyms. This enables export of thes 113 in /proc/kallsyms. This enables export of these addresses, which can
116 be used for debugging/tracing. If bpf_jit_hard 114 be used for debugging/tracing. If bpf_jit_harden is enabled, this
117 feature is disabled. 115 feature is disabled.
118 116
119 Values : 117 Values :
120 118
121 - 0 - disable JIT kallsyms export (def 119 - 0 - disable JIT kallsyms export (default value)
122 - 1 - enable JIT kallsyms export for p 120 - 1 - enable JIT kallsyms export for privileged users only
123 121
124 bpf_jit_limit 122 bpf_jit_limit
125 ------------- 123 -------------
126 124
127 This enforces a global limit for memory alloca 125 This enforces a global limit for memory allocations to the BPF JIT
128 compiler in order to reject unprivileged JIT r 126 compiler in order to reject unprivileged JIT requests once it has
129 been surpassed. bpf_jit_limit contains the val 127 been surpassed. bpf_jit_limit contains the value of the global limit
130 in bytes. 128 in bytes.
131 129
132 dev_weight 130 dev_weight
133 ---------- 131 ----------
134 132
135 The maximum number of packets that kernel can 133 The maximum number of packets that kernel can handle on a NAPI interrupt,
136 it's a Per-CPU variable. For drivers that supp 134 it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
137 aggregated packet is counted as one packet in 135 aggregated packet is counted as one packet in this context.
138 136
139 Default: 64 137 Default: 64
140 138
141 dev_weight_rx_bias 139 dev_weight_rx_bias
142 ------------------ 140 ------------------
143 141
144 RPS (e.g. RFS, aRFS) processing is competing w 142 RPS (e.g. RFS, aRFS) processing is competing with the registered NAPI poll function
145 of the driver for the per softirq cycle netdev 143 of the driver for the per softirq cycle netdev_budget. This parameter influences
146 the proportion of the configured netdev_budget 144 the proportion of the configured netdev_budget that is spent on RPS based packet
147 processing during RX softirq cycles. It is fur 145 processing during RX softirq cycles. It is further meant for making current
148 dev_weight adaptable for asymmetric CPU needs 146 dev_weight adaptable for asymmetric CPU needs on RX/TX side of the network stack.
149 (see dev_weight_tx_bias) It is effective on a 147 (see dev_weight_tx_bias) It is effective on a per CPU basis. Determination is based
150 on dev_weight and is calculated multiplicative 148 on dev_weight and is calculated multiplicative (dev_weight * dev_weight_rx_bias).
151 149
152 Default: 1 150 Default: 1
153 151
154 dev_weight_tx_bias 152 dev_weight_tx_bias
155 ------------------ 153 ------------------
156 154
157 Scales the maximum number of packets that can 155 Scales the maximum number of packets that can be processed during a TX softirq cycle.
158 Effective on a per CPU basis. Allows scaling o 156 Effective on a per CPU basis. Allows scaling of current dev_weight for asymmetric
159 net stack processing needs. Be careful to avoi 157 net stack processing needs. Be careful to avoid making TX softirq processing a CPU hog.
160 158
161 Calculation is based on dev_weight (dev_weight 159 Calculation is based on dev_weight (dev_weight * dev_weight_tx_bias).
162 160
163 Default: 1 161 Default: 1
164 162
165 default_qdisc 163 default_qdisc
166 ------------- 164 -------------
167 165
168 The default queuing discipline to use for netw 166 The default queuing discipline to use for network devices. This allows
169 overriding the default of pfifo_fast with an a 167 overriding the default of pfifo_fast with an alternative. Since the default
170 queuing discipline is created without addition 168 queuing discipline is created without additional parameters so is best suited
171 to queuing disciplines that work well without 169 to queuing disciplines that work well without configuration like stochastic
172 fair queue (sfq), CoDel (codel) or fair queue 170 fair queue (sfq), CoDel (codel) or fair queue CoDel (fq_codel). Don't use
173 queuing disciplines like Hierarchical Token Bu 171 queuing disciplines like Hierarchical Token Bucket or Deficit Round Robin
174 which require setting up classes and bandwidth 172 which require setting up classes and bandwidths. Note that physical multiqueue
175 interfaces still use mq as root qdisc, which i 173 interfaces still use mq as root qdisc, which in turn uses this default for its
176 leaves. Virtual devices (like e.g. lo or veth) 174 leaves. Virtual devices (like e.g. lo or veth) ignore this setting and instead
177 default to noqueue. 175 default to noqueue.
178 176
179 Default: pfifo_fast 177 Default: pfifo_fast
180 178
181 busy_read 179 busy_read
182 --------- 180 ---------
183 181
184 Low latency busy poll timeout for socket reads 182 Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)
185 Approximate time in us to busy loop waiting fo 183 Approximate time in us to busy loop waiting for packets on the device queue.
186 This sets the default value of the SO_BUSY_POL 184 This sets the default value of the SO_BUSY_POLL socket option.
187 Can be set or overridden per socket by setting 185 Can be set or overridden per socket by setting socket option SO_BUSY_POLL,
188 which is the preferred method of enabling. If 186 which is the preferred method of enabling. If you need to enable the feature
189 globally via sysctl, a value of 50 is recommen 187 globally via sysctl, a value of 50 is recommended.
190 188
191 Will increase power usage. 189 Will increase power usage.
192 190
193 Default: 0 (off) 191 Default: 0 (off)
194 192
195 busy_poll 193 busy_poll
196 ---------------- 194 ----------------
197 Low latency busy poll timeout for poll and sel 195 Low latency busy poll timeout for poll and select. (needs CONFIG_NET_RX_BUSY_POLL)
198 Approximate time in us to busy loop waiting fo 196 Approximate time in us to busy loop waiting for events.
199 Recommended value depends on the number of soc 197 Recommended value depends on the number of sockets you poll on.
200 For several sockets 50, for several hundreds 1 198 For several sockets 50, for several hundreds 100.
201 For more than that you probably want to use ep 199 For more than that you probably want to use epoll.
202 Note that only sockets with SO_BUSY_POLL set w 200 Note that only sockets with SO_BUSY_POLL set will be busy polled,
203 so you want to either selectively set SO_BUSY_ 201 so you want to either selectively set SO_BUSY_POLL on those sockets or set
204 sysctl.net.busy_read globally. 202 sysctl.net.busy_read globally.
205 203
206 Will increase power usage. 204 Will increase power usage.
207 205
208 Default: 0 (off) 206 Default: 0 (off)
209 207
210 mem_pcpu_rsv <<
211 ------------ <<
212 <<
213 Per-cpu reserved forward alloc cache size in p <<
214 <<
215 rmem_default 208 rmem_default
216 ------------ 209 ------------
217 210
218 The default setting of the socket receive buff 211 The default setting of the socket receive buffer in bytes.
219 212
220 rmem_max 213 rmem_max
221 -------- 214 --------
222 215
223 The maximum receive socket buffer size in byte 216 The maximum receive socket buffer size in bytes.
224 217
225 rps_default_mask 218 rps_default_mask
226 ---------------- 219 ----------------
227 220
228 The default RPS CPU mask used on newly created 221 The default RPS CPU mask used on newly created network devices. An empty
229 mask means RPS disabled by default. 222 mask means RPS disabled by default.
230 223
231 tstamp_allow_data 224 tstamp_allow_data
232 ----------------- 225 -----------------
233 Allow processes to receive tx timestamps loope 226 Allow processes to receive tx timestamps looped together with the original
234 packet contents. If disabled, transmit timesta 227 packet contents. If disabled, transmit timestamp requests from unprivileged
235 processes are dropped unless socket option SOF 228 processes are dropped unless socket option SOF_TIMESTAMPING_OPT_TSONLY is set.
236 229
237 Default: 1 (on) 230 Default: 1 (on)
238 231
239 232
240 wmem_default 233 wmem_default
241 ------------ 234 ------------
242 235
243 The default setting (in bytes) of the socket s 236 The default setting (in bytes) of the socket send buffer.
244 237
245 wmem_max 238 wmem_max
246 -------- 239 --------
247 240
248 The maximum send socket buffer size in bytes. 241 The maximum send socket buffer size in bytes.
249 242
250 message_burst and message_cost 243 message_burst and message_cost
251 ------------------------------ 244 ------------------------------
252 245
253 These parameters are used to limit the warnin 246 These parameters are used to limit the warning messages written to the kernel
254 log from the networking code. They enforc 247 log from the networking code. They enforce a rate limit to make a
255 denial-of-service attack impossible. A higher 248 denial-of-service attack impossible. A higher message_cost factor, results in
256 fewer messages that will be written. Message_b 249 fewer messages that will be written. Message_burst controls when messages will
257 be dropped. The default settings limit wa 250 be dropped. The default settings limit warning messages to one every five
258 seconds. 251 seconds.
259 252
260 warnings 253 warnings
261 -------- 254 --------
262 255
263 This sysctl is now unused. 256 This sysctl is now unused.
264 257
265 This was used to control console messages from 258 This was used to control console messages from the networking stack that
266 occur because of problems on the network like 259 occur because of problems on the network like duplicate address or bad
267 checksums. 260 checksums.
268 261
269 These messages are now emitted at KERN_DEBUG a 262 These messages are now emitted at KERN_DEBUG and can generally be enabled
270 and controlled by the dynamic_debug facility. 263 and controlled by the dynamic_debug facility.
271 264
272 netdev_budget 265 netdev_budget
273 ------------- 266 -------------
274 267
275 Maximum number of packets taken from all inter 268 Maximum number of packets taken from all interfaces in one polling cycle (NAPI
276 poll). In one polling cycle interfaces which a 269 poll). In one polling cycle interfaces which are registered to polling are
277 probed in a round-robin manner. Also, a pollin 270 probed in a round-robin manner. Also, a polling cycle may not exceed
278 netdev_budget_usecs microseconds, even if netd 271 netdev_budget_usecs microseconds, even if netdev_budget has not been
279 exhausted. 272 exhausted.
280 273
281 netdev_budget_usecs 274 netdev_budget_usecs
282 --------------------- 275 ---------------------
283 276
284 Maximum number of microseconds in one NAPI pol 277 Maximum number of microseconds in one NAPI polling cycle. Polling
285 will exit when either netdev_budget_usecs have 278 will exit when either netdev_budget_usecs have elapsed during the
286 poll cycle or the number of packets processed 279 poll cycle or the number of packets processed reaches netdev_budget.
287 280
288 netdev_max_backlog 281 netdev_max_backlog
289 ------------------ 282 ------------------
290 283
291 Maximum number of packets, queued on the INPUT 284 Maximum number of packets, queued on the INPUT side, when the interface
292 receives packets faster than kernel can proces 285 receives packets faster than kernel can process them.
293 286
294 netdev_rss_key 287 netdev_rss_key
295 -------------- 288 --------------
296 289
297 RSS (Receive Side Scaling) enabled drivers use 290 RSS (Receive Side Scaling) enabled drivers use a 40 bytes host key that is
298 randomly generated. 291 randomly generated.
299 Some user space might need to gather its conte 292 Some user space might need to gather its content even if drivers do not
300 provide ethtool -x support yet. 293 provide ethtool -x support yet.
301 294
302 :: 295 ::
303 296
304 myhost:~# cat /proc/sys/net/core/netdev_rss_ 297 myhost:~# cat /proc/sys/net/core/netdev_rss_key
305 84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47 298 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)
306 299
307 File contains nul bytes if no driver ever call 300 File contains nul bytes if no driver ever called netdev_rss_key_fill() function.
308 301
309 Note: 302 Note:
310 /proc/sys/net/core/netdev_rss_key contains 5 303 /proc/sys/net/core/netdev_rss_key contains 52 bytes of key,
311 but most drivers only use 40 bytes of it. 304 but most drivers only use 40 bytes of it.
312 305
313 :: 306 ::
314 307
315 myhost:~# ethtool -x eth0 308 myhost:~# ethtool -x eth0
316 RX flow hash indirection table for eth0 with 309 RX flow hash indirection table for eth0 with 8 RX ring(s):
317 0: 0 1 2 3 4 5 310 0: 0 1 2 3 4 5 6 7
318 RSS hash key: 311 RSS hash key:
319 84:50:f4:00:a8:15:d1:a7:e9:7f:1d:60:35:c7:47 312 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
320 313
321 netdev_tstamp_prequeue 314 netdev_tstamp_prequeue
322 ---------------------- 315 ----------------------
323 316
324 If set to 0, RX packet timestamps can be sampl 317 If set to 0, RX packet timestamps can be sampled after RPS processing, when
325 the target CPU processes packets. It might giv 318 the target CPU processes packets. It might give some delay on timestamps, but
326 permit to distribute the load on several cpus. 319 permit to distribute the load on several cpus.
327 320
328 If set to 1 (default), timestamps are sampled 321 If set to 1 (default), timestamps are sampled as soon as possible, before
329 queueing. 322 queueing.
330 323
331 netdev_unregister_timeout_secs 324 netdev_unregister_timeout_secs
332 ------------------------------ 325 ------------------------------
333 326
334 Unregister network device timeout in seconds. 327 Unregister network device timeout in seconds.
335 This option controls the timeout (in seconds) 328 This option controls the timeout (in seconds) used to issue a warning while
336 waiting for a network device refcount to drop 329 waiting for a network device refcount to drop to 0 during device
337 unregistration. A lower value may be useful du 330 unregistration. A lower value may be useful during bisection to detect
338 a leaked reference faster. A larger value may 331 a leaked reference faster. A larger value may be useful to prevent false
339 warnings on slow/loaded systems. 332 warnings on slow/loaded systems.
340 Default value is 10, minimum 1, maximum 3600. 333 Default value is 10, minimum 1, maximum 3600.
341 334
342 skb_defer_max 335 skb_defer_max
343 ------------- 336 -------------
344 337
345 Max size (in skbs) of the per-cpu list of skbs 338 Max size (in skbs) of the per-cpu list of skbs being freed
346 by the cpu which allocated them. Used by TCP s 339 by the cpu which allocated them. Used by TCP stack so far.
347 340
348 Default: 64 341 Default: 64
349 342
350 optmem_max 343 optmem_max
351 ---------- 344 ----------
352 345
353 Maximum ancillary buffer size allowed per sock 346 Maximum ancillary buffer size allowed per socket. Ancillary data is a sequence
354 of struct cmsghdr structures with appended dat !! 347 of struct cmsghdr structures with appended data.
355 optmem_max as a limit for its internal structu <<
356 <<
357 Default : 128 KB <<
358 348
359 fb_tunnels_only_for_init_net 349 fb_tunnels_only_for_init_net
360 ---------------------------- 350 ----------------------------
361 351
362 Controls if fallback tunnels (like tunl0, gre0 352 Controls if fallback tunnels (like tunl0, gre0, gretap0, erspan0,
363 sit0, ip6tnl0, ip6gre0) are automatically crea 353 sit0, ip6tnl0, ip6gre0) are automatically created. There are 3 possibilities
364 (a) value = 0; respective fallback tunnels are 354 (a) value = 0; respective fallback tunnels are created when module is
365 loaded in every net namespaces (backward compa 355 loaded in every net namespaces (backward compatible behavior).
366 (b) value = 1; [kcmd value: initns] respective 356 (b) value = 1; [kcmd value: initns] respective fallback tunnels are
367 created only in init net namespace and every o 357 created only in init net namespace and every other net namespace will
368 not have them. 358 not have them.
369 (c) value = 2; [kcmd value: none] fallback tun 359 (c) value = 2; [kcmd value: none] fallback tunnels are not created
370 when a module is loaded in any of the net name 360 when a module is loaded in any of the net namespace. Setting value to
371 "2" is pointless after boot if these modules a 361 "2" is pointless after boot if these modules are built-in, so there is
372 a kernel command-line option that can change t 362 a kernel command-line option that can change this default. Please refer to
373 Documentation/admin-guide/kernel-parameters.tx 363 Documentation/admin-guide/kernel-parameters.txt for additional details.
374 364
375 Not creating fallback tunnels gives control to 365 Not creating fallback tunnels gives control to userspace to create
376 whatever is needed only and avoid creating dev 366 whatever is needed only and avoid creating devices which are redundant.
377 367
378 Default : 0 (for compatibility reasons) 368 Default : 0 (for compatibility reasons)
379 369
380 devconf_inherit_init_net 370 devconf_inherit_init_net
381 ------------------------ 371 ------------------------
382 372
383 Controls if a new network namespace should inh 373 Controls if a new network namespace should inherit all current
384 settings under /proc/sys/net/{ipv4,ipv6}/conf/ 374 settings under /proc/sys/net/{ipv4,ipv6}/conf/{all,default}/. By
385 default, we keep the current behavior: for IPv 375 default, we keep the current behavior: for IPv4 we inherit all current
386 settings from init_net and for IPv6 we reset a 376 settings from init_net and for IPv6 we reset all settings to default.
387 377
388 If set to 1, both IPv4 and IPv6 settings are f 378 If set to 1, both IPv4 and IPv6 settings are forced to inherit from
389 current ones in init_net. If set to 2, both IP 379 current ones in init_net. If set to 2, both IPv4 and IPv6 settings are
390 forced to reset to their default values. If se 380 forced to reset to their default values. If set to 3, both IPv4 and IPv6
391 settings are forced to inherit from current on 381 settings are forced to inherit from current ones in the netns where this
392 new netns has been created. 382 new netns has been created.
393 383
394 Default : 0 (for compatibility reasons) 384 Default : 0 (for compatibility reasons)
395 385
396 txrehash 386 txrehash
397 -------- 387 --------
398 388
399 Controls default hash rethink behaviour on soc !! 389 Controls default hash rethink behaviour on listening socket when SO_TXREHASH
400 to SOCK_TXREHASH_DEFAULT (i. e. not overridden !! 390 option is set to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt).
401 391
402 If set to 1 (default), hash rethink is perform 392 If set to 1 (default), hash rethink is performed on listening socket.
403 If set to 0, hash rethink is not performed. 393 If set to 0, hash rethink is not performed.
404 394
405 gro_normal_batch 395 gro_normal_batch
406 ---------------- 396 ----------------
407 397
408 Maximum number of the segments to batch up on 398 Maximum number of the segments to batch up on output of GRO. When a packet
409 exits GRO, either as a coalesced superframe or 399 exits GRO, either as a coalesced superframe or as an original packet which
410 GRO has decided not to coalesce, it is placed 400 GRO has decided not to coalesce, it is placed on a per-NAPI list. This
411 list is then passed to the stack when the numb 401 list is then passed to the stack when the number of segments reaches the
412 gro_normal_batch limit. 402 gro_normal_batch limit.
413 403
414 high_order_alloc_disable 404 high_order_alloc_disable
415 ------------------------ 405 ------------------------
416 406
417 By default the allocator for page frags tries 407 By default the allocator for page frags tries to use high order pages (order-3
418 on x86). While the default behavior gives good 408 on x86). While the default behavior gives good results in most cases, some users
419 might have hit a contention in page allocation 409 might have hit a contention in page allocations/freeing. This was especially
420 true on older kernels (< 5.14) when high-order 410 true on older kernels (< 5.14) when high-order pages were not stored on per-cpu
421 lists. This allows to opt-in for order-0 alloc 411 lists. This allows to opt-in for order-0 allocation instead but is now mostly of
422 historical importance. 412 historical importance.
423 413
424 Default: 0 414 Default: 0
425 415
426 2. /proc/sys/net/unix - Parameters for Unix do 416 2. /proc/sys/net/unix - Parameters for Unix domain sockets
427 ---------------------------------------------- 417 ----------------------------------------------------------
428 418
429 There is only one file in this directory. 419 There is only one file in this directory.
430 unix_dgram_qlen limits the max number of datag 420 unix_dgram_qlen limits the max number of datagrams queued in Unix domain
431 socket's buffer. It will not take effect unles 421 socket's buffer. It will not take effect unless PF_UNIX flag is specified.
432 422
433 423
434 3. /proc/sys/net/ipv4 - IPV4 settings 424 3. /proc/sys/net/ipv4 - IPV4 settings
435 ------------------------------------- 425 -------------------------------------
436 Please see: Documentation/networking/ip-sysctl 426 Please see: Documentation/networking/ip-sysctl.rst and
437 Documentation/admin-guide/sysctl/net.rst for d 427 Documentation/admin-guide/sysctl/net.rst for descriptions of these entries.
438 428
439 429
440 4. Appletalk 430 4. Appletalk
441 ------------ 431 ------------
442 432
443 The /proc/sys/net/appletalk directory holds 433 The /proc/sys/net/appletalk directory holds the Appletalk configuration data
444 when Appletalk is loaded. The configurable par 434 when Appletalk is loaded. The configurable parameters are:
445 435
446 aarp-expiry-time 436 aarp-expiry-time
447 ---------------- 437 ----------------
448 438
449 The amount of time we keep an ARP entry bef 439 The amount of time we keep an ARP entry before expiring it. Used to age out
450 old hosts. 440 old hosts.
451 441
452 aarp-resolve-time 442 aarp-resolve-time
453 ----------------- 443 -----------------
454 444
455 The amount of time we will spend trying to res 445 The amount of time we will spend trying to resolve an Appletalk address.
456 446
457 aarp-retransmit-limit 447 aarp-retransmit-limit
458 --------------------- 448 ---------------------
459 449
460 The number of times we will retransmit a query 450 The number of times we will retransmit a query before giving up.
461 451
462 aarp-tick-time 452 aarp-tick-time
463 -------------- 453 --------------
464 454
465 Controls the rate at which expires are checked 455 Controls the rate at which expires are checked.
466 456
467 The directory /proc/net/appletalk holds the 457 The directory /proc/net/appletalk holds the list of active Appletalk sockets
468 on a machine. 458 on a machine.
469 459
470 The fields indicate the DDP type, the local 460 The fields indicate the DDP type, the local address (in network:node format)
471 the remote address, the size of the transmi 461 the remote address, the size of the transmit pending queue, the size of the
472 received queue (bytes waiting for application 462 received queue (bytes waiting for applications to read) the state and the uid
473 owning the socket. 463 owning the socket.
474 464
475 /proc/net/atalk_iface lists all the interfa 465 /proc/net/atalk_iface lists all the interfaces configured for appletalk.It
476 shows the name of the interface, its Appleta 466 shows the name of the interface, its Appletalk address, the network range on
477 that address (or network number for phase 1 467 that address (or network number for phase 1 networks), and the status of the
478 interface. 468 interface.
479 469
480 /proc/net/atalk_route lists each known netw 470 /proc/net/atalk_route lists each known network route. It lists the target
481 (network) that the route leads to, the router 471 (network) that the route leads to, the router (may be directly connected), the
482 route flags, and the device the route is using 472 route flags, and the device the route is using.
483 473
484 5. TIPC 474 5. TIPC
485 ------- 475 -------
486 476
487 tipc_rmem 477 tipc_rmem
488 --------- 478 ---------
489 479
490 The TIPC protocol now has a tunable for the re 480 The TIPC protocol now has a tunable for the receive memory, similar to the
491 tcp_rmem - i.e. a vector of 3 INTEGERs: (min, 481 tcp_rmem - i.e. a vector of 3 INTEGERs: (min, default, max)
492 482
493 :: 483 ::
494 484
495 # cat /proc/sys/net/tipc/tipc_rmem 485 # cat /proc/sys/net/tipc/tipc_rmem
496 4252725 34021800 68043600 486 4252725 34021800 68043600
497 # 487 #
498 488
499 The max value is set to CONN_OVERLOAD_LIMIT, a 489 The max value is set to CONN_OVERLOAD_LIMIT, and the default and min values
500 are scaled (shifted) versions of that same val 490 are scaled (shifted) versions of that same value. Note that the min value
501 is not at this point in time used in any meani 491 is not at this point in time used in any meaningful way, but the triplet is
502 preserved in order to be consistent with thing 492 preserved in order to be consistent with things like tcp_rmem.
503 493
504 named_timeout 494 named_timeout
505 ------------- 495 -------------
506 496
507 TIPC name table updates are distributed asynch 497 TIPC name table updates are distributed asynchronously in a cluster, without
508 any form of transaction handling. This means t 498 any form of transaction handling. This means that different race scenarios are
509 possible. One such is that a name withdrawal s 499 possible. One such is that a name withdrawal sent out by one node and received
510 by another node may arrive after a second, ove 500 by another node may arrive after a second, overlapping name publication already
511 has been accepted from a third node, although 501 has been accepted from a third node, although the conflicting updates
512 originally may have been issued in the correct 502 originally may have been issued in the correct sequential order.
513 If named_timeout is nonzero, failed topology u 503 If named_timeout is nonzero, failed topology updates will be placed on a defer
514 queue until another event arrives that clears 504 queue until another event arrives that clears the error, or until the timeout
515 expires. Value is in milliseconds. 505 expires. Value is in milliseconds.
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