Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /proc/sys/net/ipv4/* Variables: |
2 | ||
3 | ip_forward - BOOLEAN | |
4 | 0 - disabled (default) | |
5 | not 0 - enabled | |
6 | ||
7 | Forward Packets between interfaces. | |
8 | ||
9 | This variable is special, its change resets all configuration | |
10 | parameters to their default state (RFC1122 for hosts, RFC1812 | |
11 | for routers) | |
12 | ||
13 | ip_default_ttl - INTEGER | |
14 | default 64 | |
15 | ||
16 | ip_no_pmtu_disc - BOOLEAN | |
17 | Disable Path MTU Discovery. | |
18 | default FALSE | |
19 | ||
20 | min_pmtu - INTEGER | |
21 | default 562 - minimum discovered Path MTU | |
22 | ||
23 | mtu_expires - INTEGER | |
24 | Time, in seconds, that cached PMTU information is kept. | |
25 | ||
26 | min_adv_mss - INTEGER | |
27 | The advertised MSS depends on the first hop route MTU, but will | |
28 | never be lower than this setting. | |
29 | ||
30 | IP Fragmentation: | |
31 | ||
32 | ipfrag_high_thresh - INTEGER | |
33 | Maximum memory used to reassemble IP fragments. When | |
34 | ipfrag_high_thresh bytes of memory is allocated for this purpose, | |
35 | the fragment handler will toss packets until ipfrag_low_thresh | |
36 | is reached. | |
37 | ||
38 | ipfrag_low_thresh - INTEGER | |
39 | See ipfrag_high_thresh | |
40 | ||
41 | ipfrag_time - INTEGER | |
42 | Time in seconds to keep an IP fragment in memory. | |
43 | ||
44 | ipfrag_secret_interval - INTEGER | |
45 | Regeneration interval (in seconds) of the hash secret (or lifetime | |
46 | for the hash secret) for IP fragments. | |
47 | Default: 600 | |
48 | ||
89cee8b1 HX |
49 | ipfrag_max_dist - INTEGER |
50 | ipfrag_max_dist is a non-negative integer value which defines the | |
51 | maximum "disorder" which is allowed among fragments which share a | |
52 | common IP source address. Note that reordering of packets is | |
53 | not unusual, but if a large number of fragments arrive from a source | |
54 | IP address while a particular fragment queue remains incomplete, it | |
55 | probably indicates that one or more fragments belonging to that queue | |
56 | have been lost. When ipfrag_max_dist is positive, an additional check | |
57 | is done on fragments before they are added to a reassembly queue - if | |
58 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
59 | address between additions to any IP fragment queue using that source | |
60 | address, it's presumed that one or more fragments in the queue are | |
61 | lost. The existing fragment queue will be dropped, and a new one | |
62 | started. An ipfrag_max_dist value of zero disables this check. | |
63 | ||
64 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
65 | result in unnecessarily dropping fragment queues when normal | |
66 | reordering of packets occurs, which could lead to poor application | |
67 | performance. Using a very large value, e.g. 50000, increases the | |
68 | likelihood of incorrectly reassembling IP fragments that originate | |
69 | from different IP datagrams, which could result in data corruption. | |
70 | Default: 64 | |
71 | ||
1da177e4 LT |
72 | INET peer storage: |
73 | ||
74 | inet_peer_threshold - INTEGER | |
75 | The approximate size of the storage. Starting from this threshold | |
76 | entries will be thrown aggressively. This threshold also determines | |
77 | entries' time-to-live and time intervals between garbage collection | |
78 | passes. More entries, less time-to-live, less GC interval. | |
79 | ||
80 | inet_peer_minttl - INTEGER | |
81 | Minimum time-to-live of entries. Should be enough to cover fragment | |
82 | time-to-live on the reassembling side. This minimum time-to-live is | |
83 | guaranteed if the pool size is less than inet_peer_threshold. | |
84 | Measured in jiffies(1). | |
85 | ||
86 | inet_peer_maxttl - INTEGER | |
87 | Maximum time-to-live of entries. Unused entries will expire after | |
88 | this period of time if there is no memory pressure on the pool (i.e. | |
89 | when the number of entries in the pool is very small). | |
90 | Measured in jiffies(1). | |
91 | ||
92 | inet_peer_gc_mintime - INTEGER | |
93 | Minimum interval between garbage collection passes. This interval is | |
94 | in effect under high memory pressure on the pool. | |
95 | Measured in jiffies(1). | |
96 | ||
97 | inet_peer_gc_maxtime - INTEGER | |
98 | Minimum interval between garbage collection passes. This interval is | |
99 | in effect under low (or absent) memory pressure on the pool. | |
100 | Measured in jiffies(1). | |
101 | ||
102 | TCP variables: | |
103 | ||
ef56e622 SH |
104 | somaxconn - INTEGER |
105 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
106 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
107 | for TCP sockets. | |
108 | ||
9772efb9 | 109 | tcp_abc - INTEGER |
b3a8a40d SH |
110 | Controls Appropriate Byte Count (ABC) defined in RFC3465. |
111 | ABC is a way of increasing congestion window (cwnd) more slowly | |
112 | in response to partial acknowledgments. | |
113 | Possible values are: | |
114 | 0 increase cwnd once per acknowledgment (no ABC) | |
115 | 1 increase cwnd once per acknowledgment of full sized segment | |
116 | 2 allow increase cwnd by two if acknowledgment is | |
117 | of two segments to compensate for delayed acknowledgments. | |
118 | Default: 0 (off) | |
9772efb9 | 119 | |
ef56e622 SH |
120 | tcp_abort_on_overflow - BOOLEAN |
121 | If listening service is too slow to accept new connections, | |
122 | reset them. Default state is FALSE. It means that if overflow | |
123 | occurred due to a burst, connection will recover. Enable this | |
124 | option _only_ if you are really sure that listening daemon | |
125 | cannot be tuned to accept connections faster. Enabling this | |
126 | option can harm clients of your server. | |
1da177e4 | 127 | |
ef56e622 SH |
128 | tcp_adv_win_scale - INTEGER |
129 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
130 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
131 | if it is <= 0. | |
132 | Default: 2 | |
1da177e4 | 133 | |
ef56e622 SH |
134 | tcp_allowed_congestion_control - STRING |
135 | Show/set the congestion control choices available to non-privileged | |
136 | processes. The list is a subset of those listed in | |
137 | tcp_available_congestion_control. | |
138 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 139 | |
ef56e622 SH |
140 | tcp_app_win - INTEGER |
141 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
142 | buffer. Value 0 is special, it means that nothing is reserved. | |
143 | Default: 31 | |
1da177e4 | 144 | |
ef56e622 SH |
145 | tcp_available_congestion_control - STRING |
146 | Shows the available congestion control choices that are registered. | |
147 | More congestion control algorithms may be available as modules, | |
148 | but not loaded. | |
1da177e4 | 149 | |
ef56e622 SH |
150 | tcp_congestion_control - STRING |
151 | Set the congestion control algorithm to be used for new | |
152 | connections. The algorithm "reno" is always available, but | |
153 | additional choices may be available based on kernel configuration. | |
154 | Default is set as part of kernel configuration. | |
1da177e4 | 155 | |
ef56e622 SH |
156 | tcp_dsack - BOOLEAN |
157 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 158 | |
ef56e622 SH |
159 | tcp_ecn - BOOLEAN |
160 | Enable Explicit Congestion Notification in TCP. | |
161 | ||
162 | tcp_fack - BOOLEAN | |
163 | Enable FACK congestion avoidance and fast retransmission. | |
164 | The value is not used, if tcp_sack is not enabled. | |
1da177e4 LT |
165 | |
166 | tcp_fin_timeout - INTEGER | |
167 | Time to hold socket in state FIN-WAIT-2, if it was closed | |
168 | by our side. Peer can be broken and never close its side, | |
169 | or even died unexpectedly. Default value is 60sec. | |
170 | Usual value used in 2.2 was 180 seconds, you may restore | |
171 | it, but remember that if your machine is even underloaded WEB server, | |
172 | you risk to overflow memory with kilotons of dead sockets, | |
173 | FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1, | |
174 | because they eat maximum 1.5K of memory, but they tend | |
175 | to live longer. Cf. tcp_max_orphans. | |
176 | ||
ef56e622 SH |
177 | tcp_frto - BOOLEAN |
178 | Enables F-RTO, an enhanced recovery algorithm for TCP retransmission | |
179 | timeouts. It is particularly beneficial in wireless environments | |
180 | where packet loss is typically due to random radio interference | |
181 | rather than intermediate router congestion. | |
1da177e4 | 182 | |
ef56e622 SH |
183 | tcp_keepalive_time - INTEGER |
184 | How often TCP sends out keepalive messages when keepalive is enabled. | |
185 | Default: 2hours. | |
1da177e4 | 186 | |
ef56e622 SH |
187 | tcp_keepalive_probes - INTEGER |
188 | How many keepalive probes TCP sends out, until it decides that the | |
189 | connection is broken. Default value: 9. | |
190 | ||
191 | tcp_keepalive_intvl - INTEGER | |
192 | How frequently the probes are send out. Multiplied by | |
193 | tcp_keepalive_probes it is time to kill not responding connection, | |
194 | after probes started. Default value: 75sec i.e. connection | |
195 | will be aborted after ~11 minutes of retries. | |
196 | ||
197 | tcp_low_latency - BOOLEAN | |
198 | If set, the TCP stack makes decisions that prefer lower | |
199 | latency as opposed to higher throughput. By default, this | |
200 | option is not set meaning that higher throughput is preferred. | |
201 | An example of an application where this default should be | |
202 | changed would be a Beowulf compute cluster. | |
203 | Default: 0 | |
1da177e4 LT |
204 | |
205 | tcp_max_orphans - INTEGER | |
206 | Maximal number of TCP sockets not attached to any user file handle, | |
207 | held by system. If this number is exceeded orphaned connections are | |
208 | reset immediately and warning is printed. This limit exists | |
209 | only to prevent simple DoS attacks, you _must_ not rely on this | |
210 | or lower the limit artificially, but rather increase it | |
211 | (probably, after increasing installed memory), | |
212 | if network conditions require more than default value, | |
213 | and tune network services to linger and kill such states | |
214 | more aggressively. Let me to remind again: each orphan eats | |
215 | up to ~64K of unswappable memory. | |
216 | ||
1da177e4 LT |
217 | tcp_max_syn_backlog - INTEGER |
218 | Maximal number of remembered connection requests, which are | |
219 | still did not receive an acknowledgment from connecting client. | |
220 | Default value is 1024 for systems with more than 128Mb of memory, | |
221 | and 128 for low memory machines. If server suffers of overload, | |
222 | try to increase this number. | |
223 | ||
ef56e622 SH |
224 | tcp_max_tw_buckets - INTEGER |
225 | Maximal number of timewait sockets held by system simultaneously. | |
226 | If this number is exceeded time-wait socket is immediately destroyed | |
227 | and warning is printed. This limit exists only to prevent | |
228 | simple DoS attacks, you _must_ not lower the limit artificially, | |
229 | but rather increase it (probably, after increasing installed memory), | |
230 | if network conditions require more than default value. | |
1da177e4 | 231 | |
ef56e622 SH |
232 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
233 | min: below this number of pages TCP is not bothered about its | |
234 | memory appetite. | |
1da177e4 | 235 | |
ef56e622 SH |
236 | pressure: when amount of memory allocated by TCP exceeds this number |
237 | of pages, TCP moderates its memory consumption and enters memory | |
238 | pressure mode, which is exited when memory consumption falls | |
239 | under "min". | |
1da177e4 | 240 | |
ef56e622 | 241 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 242 | |
ef56e622 SH |
243 | Defaults are calculated at boot time from amount of available |
244 | memory. | |
1da177e4 | 245 | |
ef56e622 SH |
246 | tcp_orphan_retries - INTEGER |
247 | How may times to retry before killing TCP connection, closed | |
248 | by our side. Default value 7 corresponds to ~50sec-16min | |
249 | depending on RTO. If you machine is loaded WEB server, | |
250 | you should think about lowering this value, such sockets | |
251 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
252 | |
253 | tcp_reordering - INTEGER | |
254 | Maximal reordering of packets in a TCP stream. | |
255 | Default: 3 | |
256 | ||
257 | tcp_retrans_collapse - BOOLEAN | |
258 | Bug-to-bug compatibility with some broken printers. | |
259 | On retransmit try to send bigger packets to work around bugs in | |
260 | certain TCP stacks. | |
261 | ||
ef56e622 SH |
262 | tcp_retries1 - INTEGER |
263 | How many times to retry before deciding that something is wrong | |
264 | and it is necessary to report this suspicion to network layer. | |
265 | Minimal RFC value is 3, it is default, which corresponds | |
266 | to ~3sec-8min depending on RTO. | |
1da177e4 | 267 | |
ef56e622 SH |
268 | tcp_retries2 - INTEGER |
269 | How may times to retry before killing alive TCP connection. | |
270 | RFC1122 says that the limit should be longer than 100 sec. | |
271 | It is too small number. Default value 15 corresponds to ~13-30min | |
272 | depending on RTO. | |
1da177e4 | 273 | |
ef56e622 SH |
274 | tcp_rfc1337 - BOOLEAN |
275 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
276 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
277 | assassination. | |
278 | Default: 0 | |
1da177e4 LT |
279 | |
280 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
281 | min: Minimal size of receive buffer used by TCP sockets. | |
282 | It is guaranteed to each TCP socket, even under moderate memory | |
283 | pressure. | |
284 | Default: 8K | |
285 | ||
286 | default: default size of receive buffer used by TCP sockets. | |
287 | This value overrides net.core.rmem_default used by other protocols. | |
288 | Default: 87380 bytes. This value results in window of 65535 with | |
289 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
290 | less for default tcp_app_win. See below about these variables. | |
291 | ||
292 | max: maximal size of receive buffer allowed for automatically | |
293 | selected receiver buffers for TCP socket. This value does not override | |
294 | net.core.rmem_max, "static" selection via SO_RCVBUF does not use this. | |
295 | Default: 87380*2 bytes. | |
296 | ||
ef56e622 SH |
297 | tcp_sack - BOOLEAN |
298 | Enable select acknowledgments (SACKS). | |
1da177e4 | 299 | |
ef56e622 SH |
300 | tcp_slow_start_after_idle - BOOLEAN |
301 | If set, provide RFC2861 behavior and time out the congestion | |
302 | window after an idle period. An idle period is defined at | |
303 | the current RTO. If unset, the congestion window will not | |
304 | be timed out after an idle period. | |
305 | Default: 1 | |
1da177e4 | 306 | |
ef56e622 SH |
307 | tcp_stdurg - BOOLEAN |
308 | Use the Host requirements interpretation of the TCP urg pointer field. | |
309 | Most hosts use the older BSD interpretation, so if you turn this on | |
310 | Linux might not communicate correctly with them. | |
311 | Default: FALSE | |
1da177e4 | 312 | |
ef56e622 SH |
313 | tcp_synack_retries - INTEGER |
314 | Number of times SYNACKs for a passive TCP connection attempt will | |
315 | be retransmitted. Should not be higher than 255. Default value | |
316 | is 5, which corresponds to ~180seconds. | |
1da177e4 | 317 | |
ef56e622 SH |
318 | tcp_syncookies - BOOLEAN |
319 | Only valid when the kernel was compiled with CONFIG_SYNCOOKIES | |
320 | Send out syncookies when the syn backlog queue of a socket | |
321 | overflows. This is to prevent against the common 'syn flood attack' | |
322 | Default: FALSE | |
1da177e4 | 323 | |
ef56e622 SH |
324 | Note, that syncookies is fallback facility. |
325 | It MUST NOT be used to help highly loaded servers to stand | |
326 | against legal connection rate. If you see synflood warnings | |
327 | in your logs, but investigation shows that they occur | |
328 | because of overload with legal connections, you should tune | |
329 | another parameters until this warning disappear. | |
330 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 331 | |
ef56e622 SH |
332 | syncookies seriously violate TCP protocol, do not allow |
333 | to use TCP extensions, can result in serious degradation | |
334 | of some services (f.e. SMTP relaying), visible not by you, | |
335 | but your clients and relays, contacting you. While you see | |
336 | synflood warnings in logs not being really flooded, your server | |
337 | is seriously misconfigured. | |
1da177e4 | 338 | |
ef56e622 SH |
339 | tcp_syn_retries - INTEGER |
340 | Number of times initial SYNs for an active TCP connection attempt | |
341 | will be retransmitted. Should not be higher than 255. Default value | |
342 | is 5, which corresponds to ~180seconds. | |
343 | ||
344 | tcp_timestamps - BOOLEAN | |
345 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 346 | |
1da177e4 | 347 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
348 | This allows control over what percentage of the congestion window |
349 | can be consumed by a single TSO frame. | |
350 | The setting of this parameter is a choice between burstiness and | |
351 | building larger TSO frames. | |
352 | Default: 3 | |
1da177e4 | 353 | |
ef56e622 SH |
354 | tcp_tw_recycle - BOOLEAN |
355 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
356 | It should not be changed without advice/request of technical | |
357 | experts. | |
1da177e4 | 358 | |
ef56e622 SH |
359 | tcp_tw_reuse - BOOLEAN |
360 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
361 | safe from protocol viewpoint. Default value is 0. | |
362 | It should not be changed without advice/request of technical | |
363 | experts. | |
ce7bc3bf | 364 | |
ef56e622 SH |
365 | tcp_window_scaling - BOOLEAN |
366 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 367 | |
ef56e622 SH |
368 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
369 | min: Amount of memory reserved for send buffers for TCP socket. | |
370 | Each TCP socket has rights to use it due to fact of its birth. | |
371 | Default: 4K | |
9d7bcfc6 | 372 | |
ef56e622 SH |
373 | default: Amount of memory allowed for send buffers for TCP socket |
374 | by default. This value overrides net.core.wmem_default used | |
375 | by other protocols, it is usually lower than net.core.wmem_default. | |
376 | Default: 16K | |
377 | ||
378 | max: Maximal amount of memory allowed for automatically selected | |
379 | send buffers for TCP socket. This value does not override | |
380 | net.core.wmem_max, "static" selection via SO_SNDBUF does not use this. | |
381 | Default: 128K | |
1da177e4 | 382 | |
15d99e02 RJ |
383 | tcp_workaround_signed_windows - BOOLEAN |
384 | If set, assume no receipt of a window scaling option means the | |
385 | remote TCP is broken and treats the window as a signed quantity. | |
386 | If unset, assume the remote TCP is not broken even if we do | |
387 | not receive a window scaling option from them. | |
388 | Default: 0 | |
389 | ||
8802f616 PM |
390 | CIPSOv4 Variables: |
391 | ||
392 | cipso_cache_enable - BOOLEAN | |
393 | If set, enable additions to and lookups from the CIPSO label mapping | |
394 | cache. If unset, additions are ignored and lookups always result in a | |
395 | miss. However, regardless of the setting the cache is still | |
396 | invalidated when required when means you can safely toggle this on and | |
397 | off and the cache will always be "safe". | |
398 | Default: 1 | |
399 | ||
400 | cipso_cache_bucket_size - INTEGER | |
401 | The CIPSO label cache consists of a fixed size hash table with each | |
402 | hash bucket containing a number of cache entries. This variable limits | |
403 | the number of entries in each hash bucket; the larger the value the | |
404 | more CIPSO label mappings that can be cached. When the number of | |
405 | entries in a given hash bucket reaches this limit adding new entries | |
406 | causes the oldest entry in the bucket to be removed to make room. | |
407 | Default: 10 | |
408 | ||
409 | cipso_rbm_optfmt - BOOLEAN | |
410 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
411 | the CIPSO draft specification (see Documentation/netlabel for details). | |
412 | This means that when set the CIPSO tag will be padded with empty | |
413 | categories in order to make the packet data 32-bit aligned. | |
414 | Default: 0 | |
415 | ||
416 | cipso_rbm_structvalid - BOOLEAN | |
417 | If set, do a very strict check of the CIPSO option when | |
418 | ip_options_compile() is called. If unset, relax the checks done during | |
419 | ip_options_compile(). Either way is "safe" as errors are caught else | |
420 | where in the CIPSO processing code but setting this to 0 (False) should | |
421 | result in less work (i.e. it should be faster) but could cause problems | |
422 | with other implementations that require strict checking. | |
423 | Default: 0 | |
424 | ||
1da177e4 LT |
425 | IP Variables: |
426 | ||
427 | ip_local_port_range - 2 INTEGERS | |
428 | Defines the local port range that is used by TCP and UDP to | |
429 | choose the local port. The first number is the first, the | |
430 | second the last local port number. Default value depends on | |
431 | amount of memory available on the system: | |
432 | > 128Mb 32768-61000 | |
433 | < 128Mb 1024-4999 or even less. | |
434 | This number defines number of active connections, which this | |
435 | system can issue simultaneously to systems not supporting | |
436 | TCP extensions (timestamps). With tcp_tw_recycle enabled | |
437 | (i.e. by default) range 1024-4999 is enough to issue up to | |
438 | 2000 connections per second to systems supporting timestamps. | |
439 | ||
440 | ip_nonlocal_bind - BOOLEAN | |
441 | If set, allows processes to bind() to non-local IP addresses, | |
442 | which can be quite useful - but may break some applications. | |
443 | Default: 0 | |
444 | ||
445 | ip_dynaddr - BOOLEAN | |
446 | If set non-zero, enables support for dynamic addresses. | |
447 | If set to a non-zero value larger than 1, a kernel log | |
448 | message will be printed when dynamic address rewriting | |
449 | occurs. | |
450 | Default: 0 | |
451 | ||
452 | icmp_echo_ignore_all - BOOLEAN | |
7ce31246 DM |
453 | If set non-zero, then the kernel will ignore all ICMP ECHO |
454 | requests sent to it. | |
455 | Default: 0 | |
456 | ||
1da177e4 | 457 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
458 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
459 | TIMESTAMP requests sent to it via broadcast/multicast. | |
460 | Default: 1 | |
1da177e4 LT |
461 | |
462 | icmp_ratelimit - INTEGER | |
463 | Limit the maximal rates for sending ICMP packets whose type matches | |
464 | icmp_ratemask (see below) to specific targets. | |
465 | 0 to disable any limiting, otherwise the maximal rate in jiffies(1) | |
466 | Default: 100 | |
467 | ||
468 | icmp_ratemask - INTEGER | |
469 | Mask made of ICMP types for which rates are being limited. | |
470 | Significant bits: IHGFEDCBA9876543210 | |
471 | Default mask: 0000001100000011000 (6168) | |
472 | ||
473 | Bit definitions (see include/linux/icmp.h): | |
474 | 0 Echo Reply | |
475 | 3 Destination Unreachable * | |
476 | 4 Source Quench * | |
477 | 5 Redirect | |
478 | 8 Echo Request | |
479 | B Time Exceeded * | |
480 | C Parameter Problem * | |
481 | D Timestamp Request | |
482 | E Timestamp Reply | |
483 | F Info Request | |
484 | G Info Reply | |
485 | H Address Mask Request | |
486 | I Address Mask Reply | |
487 | ||
488 | * These are rate limited by default (see default mask above) | |
489 | ||
490 | icmp_ignore_bogus_error_responses - BOOLEAN | |
491 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
492 | frames. Such violations are normally logged via a kernel warning. | |
493 | If this is set to TRUE, the kernel will not give such warnings, which | |
494 | will avoid log file clutter. | |
495 | Default: FALSE | |
496 | ||
95f7daf1 H |
497 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
498 | ||
499 | If zero, icmp error messages are sent with the primary address of | |
500 | the exiting interface. | |
501 | ||
502 | If non-zero, the message will be sent with the primary address of | |
503 | the interface that received the packet that caused the icmp error. | |
504 | This is the behaviour network many administrators will expect from | |
505 | a router. And it can make debugging complicated network layouts | |
506 | much easier. | |
507 | ||
508 | Note that if no primary address exists for the interface selected, | |
509 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 510 | has one will be used regardless of this setting. |
95f7daf1 H |
511 | |
512 | Default: 0 | |
513 | ||
1da177e4 LT |
514 | igmp_max_memberships - INTEGER |
515 | Change the maximum number of multicast groups we can subscribe to. | |
516 | Default: 20 | |
517 | ||
518 | conf/interface/* changes special settings per interface (where "interface" is | |
519 | the name of your network interface) | |
520 | conf/all/* is special, changes the settings for all interfaces | |
521 | ||
522 | ||
523 | log_martians - BOOLEAN | |
524 | Log packets with impossible addresses to kernel log. | |
525 | log_martians for the interface will be enabled if at least one of | |
526 | conf/{all,interface}/log_martians is set to TRUE, | |
527 | it will be disabled otherwise | |
528 | ||
529 | accept_redirects - BOOLEAN | |
530 | Accept ICMP redirect messages. | |
531 | accept_redirects for the interface will be enabled if: | |
532 | - both conf/{all,interface}/accept_redirects are TRUE in the case forwarding | |
533 | for the interface is enabled | |
534 | or | |
535 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the case | |
536 | forwarding for the interface is disabled | |
537 | accept_redirects for the interface will be disabled otherwise | |
538 | default TRUE (host) | |
539 | FALSE (router) | |
540 | ||
541 | forwarding - BOOLEAN | |
542 | Enable IP forwarding on this interface. | |
543 | ||
544 | mc_forwarding - BOOLEAN | |
545 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
546 | and a multicast routing daemon is required. | |
547 | conf/all/mc_forwarding must also be set to TRUE to enable multicast routing | |
548 | for the interface | |
549 | ||
550 | medium_id - INTEGER | |
551 | Integer value used to differentiate the devices by the medium they | |
552 | are attached to. Two devices can have different id values when | |
553 | the broadcast packets are received only on one of them. | |
554 | The default value 0 means that the device is the only interface | |
555 | to its medium, value of -1 means that medium is not known. | |
556 | ||
557 | Currently, it is used to change the proxy_arp behavior: | |
558 | the proxy_arp feature is enabled for packets forwarded between | |
559 | two devices attached to different media. | |
560 | ||
561 | proxy_arp - BOOLEAN | |
562 | Do proxy arp. | |
563 | proxy_arp for the interface will be enabled if at least one of | |
564 | conf/{all,interface}/proxy_arp is set to TRUE, | |
565 | it will be disabled otherwise | |
566 | ||
567 | shared_media - BOOLEAN | |
568 | Send(router) or accept(host) RFC1620 shared media redirects. | |
569 | Overrides ip_secure_redirects. | |
570 | shared_media for the interface will be enabled if at least one of | |
571 | conf/{all,interface}/shared_media is set to TRUE, | |
572 | it will be disabled otherwise | |
573 | default TRUE | |
574 | ||
575 | secure_redirects - BOOLEAN | |
576 | Accept ICMP redirect messages only for gateways, | |
577 | listed in default gateway list. | |
578 | secure_redirects for the interface will be enabled if at least one of | |
579 | conf/{all,interface}/secure_redirects is set to TRUE, | |
580 | it will be disabled otherwise | |
581 | default TRUE | |
582 | ||
583 | send_redirects - BOOLEAN | |
584 | Send redirects, if router. | |
585 | send_redirects for the interface will be enabled if at least one of | |
586 | conf/{all,interface}/send_redirects is set to TRUE, | |
587 | it will be disabled otherwise | |
588 | Default: TRUE | |
589 | ||
590 | bootp_relay - BOOLEAN | |
591 | Accept packets with source address 0.b.c.d destined | |
592 | not to this host as local ones. It is supposed, that | |
593 | BOOTP relay daemon will catch and forward such packets. | |
594 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
595 | for the interface | |
596 | default FALSE | |
597 | Not Implemented Yet. | |
598 | ||
599 | accept_source_route - BOOLEAN | |
600 | Accept packets with SRR option. | |
601 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
602 | with SRR option on the interface | |
603 | default TRUE (router) | |
604 | FALSE (host) | |
605 | ||
606 | rp_filter - BOOLEAN | |
607 | 1 - do source validation by reversed path, as specified in RFC1812 | |
608 | Recommended option for single homed hosts and stub network | |
609 | routers. Could cause troubles for complicated (not loop free) | |
610 | networks running a slow unreliable protocol (sort of RIP), | |
611 | or using static routes. | |
612 | ||
613 | 0 - No source validation. | |
614 | ||
615 | conf/all/rp_filter must also be set to TRUE to do source validation | |
616 | on the interface | |
617 | ||
618 | Default value is 0. Note that some distributions enable it | |
619 | in startup scripts. | |
620 | ||
621 | arp_filter - BOOLEAN | |
622 | 1 - Allows you to have multiple network interfaces on the same | |
623 | subnet, and have the ARPs for each interface be answered | |
624 | based on whether or not the kernel would route a packet from | |
625 | the ARP'd IP out that interface (therefore you must use source | |
626 | based routing for this to work). In other words it allows control | |
627 | of which cards (usually 1) will respond to an arp request. | |
628 | ||
629 | 0 - (default) The kernel can respond to arp requests with addresses | |
630 | from other interfaces. This may seem wrong but it usually makes | |
631 | sense, because it increases the chance of successful communication. | |
632 | IP addresses are owned by the complete host on Linux, not by | |
633 | particular interfaces. Only for more complex setups like load- | |
634 | balancing, does this behaviour cause problems. | |
635 | ||
636 | arp_filter for the interface will be enabled if at least one of | |
637 | conf/{all,interface}/arp_filter is set to TRUE, | |
638 | it will be disabled otherwise | |
639 | ||
640 | arp_announce - INTEGER | |
641 | Define different restriction levels for announcing the local | |
642 | source IP address from IP packets in ARP requests sent on | |
643 | interface: | |
644 | 0 - (default) Use any local address, configured on any interface | |
645 | 1 - Try to avoid local addresses that are not in the target's | |
646 | subnet for this interface. This mode is useful when target | |
647 | hosts reachable via this interface require the source IP | |
648 | address in ARP requests to be part of their logical network | |
649 | configured on the receiving interface. When we generate the | |
650 | request we will check all our subnets that include the | |
651 | target IP and will preserve the source address if it is from | |
652 | such subnet. If there is no such subnet we select source | |
653 | address according to the rules for level 2. | |
654 | 2 - Always use the best local address for this target. | |
655 | In this mode we ignore the source address in the IP packet | |
656 | and try to select local address that we prefer for talks with | |
657 | the target host. Such local address is selected by looking | |
658 | for primary IP addresses on all our subnets on the outgoing | |
659 | interface that include the target IP address. If no suitable | |
660 | local address is found we select the first local address | |
661 | we have on the outgoing interface or on all other interfaces, | |
662 | with the hope we will receive reply for our request and | |
663 | even sometimes no matter the source IP address we announce. | |
664 | ||
665 | The max value from conf/{all,interface}/arp_announce is used. | |
666 | ||
667 | Increasing the restriction level gives more chance for | |
668 | receiving answer from the resolved target while decreasing | |
669 | the level announces more valid sender's information. | |
670 | ||
671 | arp_ignore - INTEGER | |
672 | Define different modes for sending replies in response to | |
673 | received ARP requests that resolve local target IP addresses: | |
674 | 0 - (default): reply for any local target IP address, configured | |
675 | on any interface | |
676 | 1 - reply only if the target IP address is local address | |
677 | configured on the incoming interface | |
678 | 2 - reply only if the target IP address is local address | |
679 | configured on the incoming interface and both with the | |
680 | sender's IP address are part from same subnet on this interface | |
681 | 3 - do not reply for local addresses configured with scope host, | |
682 | only resolutions for global and link addresses are replied | |
683 | 4-7 - reserved | |
684 | 8 - do not reply for all local addresses | |
685 | ||
686 | The max value from conf/{all,interface}/arp_ignore is used | |
687 | when ARP request is received on the {interface} | |
688 | ||
c1b1bce8 NH |
689 | arp_accept - BOOLEAN |
690 | Define behavior when gratuitous arp replies are received: | |
691 | 0 - drop gratuitous arp frames | |
692 | 1 - accept gratuitous arp frames | |
693 | ||
1da177e4 LT |
694 | app_solicit - INTEGER |
695 | The maximum number of probes to send to the user space ARP daemon | |
696 | via netlink before dropping back to multicast probes (see | |
697 | mcast_solicit). Defaults to 0. | |
698 | ||
699 | disable_policy - BOOLEAN | |
700 | Disable IPSEC policy (SPD) for this interface | |
701 | ||
702 | disable_xfrm - BOOLEAN | |
703 | Disable IPSEC encryption on this interface, whatever the policy | |
704 | ||
705 | ||
706 | ||
707 | tag - INTEGER | |
708 | Allows you to write a number, which can be used as required. | |
709 | Default value is 0. | |
710 | ||
711 | (1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the | |
712 | Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact | |
713 | value on your system. | |
714 | ||
715 | Alexey Kuznetsov. | |
716 | kuznet@ms2.inr.ac.ru | |
717 | ||
718 | Updated by: | |
719 | Andi Kleen | |
720 | ak@muc.de | |
721 | Nicolas Delon | |
722 | delon.nicolas@wanadoo.fr | |
723 | ||
724 | ||
725 | ||
726 | ||
727 | /proc/sys/net/ipv6/* Variables: | |
728 | ||
729 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
730 | apply to IPv6 [XXX?]. | |
731 | ||
732 | bindv6only - BOOLEAN | |
733 | Default value for IPV6_V6ONLY socket option, | |
734 | which restricts use of the IPv6 socket to IPv6 communication | |
735 | only. | |
736 | TRUE: disable IPv4-mapped address feature | |
737 | FALSE: enable IPv4-mapped address feature | |
738 | ||
739 | Default: FALSE (as specified in RFC2553bis) | |
740 | ||
741 | IPv6 Fragmentation: | |
742 | ||
743 | ip6frag_high_thresh - INTEGER | |
744 | Maximum memory used to reassemble IPv6 fragments. When | |
745 | ip6frag_high_thresh bytes of memory is allocated for this purpose, | |
746 | the fragment handler will toss packets until ip6frag_low_thresh | |
747 | is reached. | |
748 | ||
749 | ip6frag_low_thresh - INTEGER | |
750 | See ip6frag_high_thresh | |
751 | ||
752 | ip6frag_time - INTEGER | |
753 | Time in seconds to keep an IPv6 fragment in memory. | |
754 | ||
755 | ip6frag_secret_interval - INTEGER | |
756 | Regeneration interval (in seconds) of the hash secret (or lifetime | |
757 | for the hash secret) for IPv6 fragments. | |
758 | Default: 600 | |
759 | ||
760 | conf/default/*: | |
761 | Change the interface-specific default settings. | |
762 | ||
763 | ||
764 | conf/all/*: | |
765 | Change all the interface-specific settings. | |
766 | ||
767 | [XXX: Other special features than forwarding?] | |
768 | ||
769 | conf/all/forwarding - BOOLEAN | |
770 | Enable global IPv6 forwarding between all interfaces. | |
771 | ||
772 | IPv4 and IPv6 work differently here; e.g. netfilter must be used | |
773 | to control which interfaces may forward packets and which not. | |
774 | ||
775 | This also sets all interfaces' Host/Router setting | |
776 | 'forwarding' to the specified value. See below for details. | |
777 | ||
778 | This referred to as global forwarding. | |
779 | ||
fbea49e1 YH |
780 | proxy_ndp - BOOLEAN |
781 | Do proxy ndp. | |
782 | ||
1da177e4 LT |
783 | conf/interface/*: |
784 | Change special settings per interface. | |
785 | ||
786 | The functional behaviour for certain settings is different | |
787 | depending on whether local forwarding is enabled or not. | |
788 | ||
789 | accept_ra - BOOLEAN | |
790 | Accept Router Advertisements; autoconfigure using them. | |
791 | ||
792 | Functional default: enabled if local forwarding is disabled. | |
793 | disabled if local forwarding is enabled. | |
794 | ||
65f5c7c1 YH |
795 | accept_ra_defrtr - BOOLEAN |
796 | Learn default router in Router Advertisement. | |
797 | ||
798 | Functional default: enabled if accept_ra is enabled. | |
799 | disabled if accept_ra is disabled. | |
800 | ||
c4fd30eb | 801 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 802 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
803 | |
804 | Functional default: enabled if accept_ra is enabled. | |
805 | disabled if accept_ra is disabled. | |
806 | ||
09c884d4 YH |
807 | accept_ra_rt_info_max_plen - INTEGER |
808 | Maximum prefix length of Route Information in RA. | |
809 | ||
810 | Route Information w/ prefix larger than or equal to this | |
811 | variable shall be ignored. | |
812 | ||
813 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
814 | -1 if accept_ra_rtr_pref is disabled. | |
815 | ||
930d6ff2 YH |
816 | accept_ra_rtr_pref - BOOLEAN |
817 | Accept Router Preference in RA. | |
818 | ||
819 | Functional default: enabled if accept_ra is enabled. | |
820 | disabled if accept_ra is disabled. | |
821 | ||
1da177e4 LT |
822 | accept_redirects - BOOLEAN |
823 | Accept Redirects. | |
824 | ||
825 | Functional default: enabled if local forwarding is disabled. | |
826 | disabled if local forwarding is enabled. | |
827 | ||
828 | autoconf - BOOLEAN | |
829 | Autoconfigure addresses using Prefix Information in Router | |
830 | Advertisements. | |
831 | ||
c4fd30eb YH |
832 | Functional default: enabled if accept_ra_pinfo is enabled. |
833 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
834 | |
835 | dad_transmits - INTEGER | |
836 | The amount of Duplicate Address Detection probes to send. | |
837 | Default: 1 | |
838 | ||
839 | forwarding - BOOLEAN | |
840 | Configure interface-specific Host/Router behaviour. | |
841 | ||
842 | Note: It is recommended to have the same setting on all | |
843 | interfaces; mixed router/host scenarios are rather uncommon. | |
844 | ||
845 | FALSE: | |
846 | ||
847 | By default, Host behaviour is assumed. This means: | |
848 | ||
849 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
850 | 2. Router Solicitations are being sent when necessary. | |
851 | 3. If accept_ra is TRUE (default), accept Router | |
852 | Advertisements (and do autoconfiguration). | |
853 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
854 | ||
855 | TRUE: | |
856 | ||
857 | If local forwarding is enabled, Router behaviour is assumed. | |
858 | This means exactly the reverse from the above: | |
859 | ||
860 | 1. IsRouter flag is set in Neighbour Advertisements. | |
861 | 2. Router Solicitations are not sent. | |
862 | 3. Router Advertisements are ignored. | |
863 | 4. Redirects are ignored. | |
864 | ||
865 | Default: FALSE if global forwarding is disabled (default), | |
866 | otherwise TRUE. | |
867 | ||
868 | hop_limit - INTEGER | |
869 | Default Hop Limit to set. | |
870 | Default: 64 | |
871 | ||
872 | mtu - INTEGER | |
873 | Default Maximum Transfer Unit | |
874 | Default: 1280 (IPv6 required minimum) | |
875 | ||
52e16356 YH |
876 | router_probe_interval - INTEGER |
877 | Minimum interval (in seconds) between Router Probing described | |
878 | in RFC4191. | |
879 | ||
880 | Default: 60 | |
881 | ||
1da177e4 LT |
882 | router_solicitation_delay - INTEGER |
883 | Number of seconds to wait after interface is brought up | |
884 | before sending Router Solicitations. | |
885 | Default: 1 | |
886 | ||
887 | router_solicitation_interval - INTEGER | |
888 | Number of seconds to wait between Router Solicitations. | |
889 | Default: 4 | |
890 | ||
891 | router_solicitations - INTEGER | |
892 | Number of Router Solicitations to send until assuming no | |
893 | routers are present. | |
894 | Default: 3 | |
895 | ||
896 | use_tempaddr - INTEGER | |
897 | Preference for Privacy Extensions (RFC3041). | |
898 | <= 0 : disable Privacy Extensions | |
899 | == 1 : enable Privacy Extensions, but prefer public | |
900 | addresses over temporary addresses. | |
901 | > 1 : enable Privacy Extensions and prefer temporary | |
902 | addresses over public addresses. | |
903 | Default: 0 (for most devices) | |
904 | -1 (for point-to-point devices and loopback devices) | |
905 | ||
906 | temp_valid_lft - INTEGER | |
907 | valid lifetime (in seconds) for temporary addresses. | |
908 | Default: 604800 (7 days) | |
909 | ||
910 | temp_prefered_lft - INTEGER | |
911 | Preferred lifetime (in seconds) for temporary addresses. | |
912 | Default: 86400 (1 day) | |
913 | ||
914 | max_desync_factor - INTEGER | |
915 | Maximum value for DESYNC_FACTOR, which is a random value | |
916 | that ensures that clients don't synchronize with each | |
917 | other and generate new addresses at exactly the same time. | |
918 | value is in seconds. | |
919 | Default: 600 | |
920 | ||
921 | regen_max_retry - INTEGER | |
922 | Number of attempts before give up attempting to generate | |
923 | valid temporary addresses. | |
924 | Default: 5 | |
925 | ||
926 | max_addresses - INTEGER | |
927 | Number of maximum addresses per interface. 0 disables limitation. | |
928 | It is recommended not set too large value (or 0) because it would | |
929 | be too easy way to crash kernel to allow to create too much of | |
930 | autoconfigured addresses. | |
931 | Default: 16 | |
932 | ||
933 | icmp/*: | |
934 | ratelimit - INTEGER | |
935 | Limit the maximal rates for sending ICMPv6 packets. | |
936 | 0 to disable any limiting, otherwise the maximal rate in jiffies(1) | |
937 | Default: 100 | |
938 | ||
939 | ||
940 | IPv6 Update by: | |
941 | Pekka Savola <pekkas@netcore.fi> | |
942 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
943 | ||
944 | ||
945 | /proc/sys/net/bridge/* Variables: | |
946 | ||
947 | bridge-nf-call-arptables - BOOLEAN | |
948 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
949 | 0 : disable this. | |
950 | Default: 1 | |
951 | ||
952 | bridge-nf-call-iptables - BOOLEAN | |
953 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
954 | 0 : disable this. | |
955 | Default: 1 | |
956 | ||
957 | bridge-nf-call-ip6tables - BOOLEAN | |
958 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
959 | 0 : disable this. | |
960 | Default: 1 | |
961 | ||
962 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
963 | 1 : pass bridged vlan-tagged ARP/IP traffic to arptables/iptables. | |
964 | 0 : disable this. | |
965 | Default: 1 | |
966 | ||
967 | ||
968 | UNDOCUMENTED: | |
969 | ||
970 | dev_weight FIXME | |
971 | discovery_slots FIXME | |
972 | discovery_timeout FIXME | |
973 | fast_poll_increase FIXME | |
974 | ip6_queue_maxlen FIXME | |
975 | lap_keepalive_time FIXME | |
976 | lo_cong FIXME | |
977 | max_baud_rate FIXME | |
978 | max_dgram_qlen FIXME | |
979 | max_noreply_time FIXME | |
980 | max_tx_data_size FIXME | |
981 | max_tx_window FIXME | |
982 | min_tx_turn_time FIXME | |
983 | mod_cong FIXME | |
984 | no_cong FIXME | |
985 | no_cong_thresh FIXME | |
986 | slot_timeout FIXME | |
987 | warn_noreply_time FIXME | |
988 |