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Commit | Line | Data |
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1da177e4 LT |
1 | /proc/sys/net/ipv4/* Variables: |
2 | ||
3 | ip_forward - BOOLEAN | |
4 | 0 - disabled (default) | |
e18f5feb | 5 | not 0 - enabled |
1da177e4 LT |
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 | ||
1080d709 NH |
30 | rt_cache_rebuild_count - INTEGER |
31 | The per net-namespace route cache emergency rebuild threshold. | |
32 | Any net-namespace having its route cache rebuilt due to | |
33 | a hash bucket chain being too long more than this many times | |
34 | will have its route caching disabled | |
35 | ||
1da177e4 LT |
36 | IP Fragmentation: |
37 | ||
38 | ipfrag_high_thresh - INTEGER | |
e18f5feb | 39 | Maximum memory used to reassemble IP fragments. When |
1da177e4 LT |
40 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
41 | the fragment handler will toss packets until ipfrag_low_thresh | |
42 | is reached. | |
e18f5feb | 43 | |
1da177e4 | 44 | ipfrag_low_thresh - INTEGER |
e18f5feb | 45 | See ipfrag_high_thresh |
1da177e4 LT |
46 | |
47 | ipfrag_time - INTEGER | |
e18f5feb | 48 | Time in seconds to keep an IP fragment in memory. |
1da177e4 LT |
49 | |
50 | ipfrag_secret_interval - INTEGER | |
e18f5feb | 51 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
52 | for the hash secret) for IP fragments. |
53 | Default: 600 | |
54 | ||
89cee8b1 | 55 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
56 | ipfrag_max_dist is a non-negative integer value which defines the |
57 | maximum "disorder" which is allowed among fragments which share a | |
58 | common IP source address. Note that reordering of packets is | |
59 | not unusual, but if a large number of fragments arrive from a source | |
60 | IP address while a particular fragment queue remains incomplete, it | |
61 | probably indicates that one or more fragments belonging to that queue | |
62 | have been lost. When ipfrag_max_dist is positive, an additional check | |
63 | is done on fragments before they are added to a reassembly queue - if | |
64 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
65 | address between additions to any IP fragment queue using that source | |
66 | address, it's presumed that one or more fragments in the queue are | |
67 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
68 | started. An ipfrag_max_dist value of zero disables this check. |
69 | ||
70 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
71 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
72 | reordering of packets occurs, which could lead to poor application |
73 | performance. Using a very large value, e.g. 50000, increases the | |
74 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
75 | from different IP datagrams, which could result in data corruption. |
76 | Default: 64 | |
77 | ||
1da177e4 LT |
78 | INET peer storage: |
79 | ||
80 | inet_peer_threshold - INTEGER | |
e18f5feb | 81 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
82 | entries will be thrown aggressively. This threshold also determines |
83 | entries' time-to-live and time intervals between garbage collection | |
84 | passes. More entries, less time-to-live, less GC interval. | |
85 | ||
86 | inet_peer_minttl - INTEGER | |
87 | Minimum time-to-live of entries. Should be enough to cover fragment | |
88 | time-to-live on the reassembling side. This minimum time-to-live is | |
89 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 90 | Measured in seconds. |
1da177e4 LT |
91 | |
92 | inet_peer_maxttl - INTEGER | |
93 | Maximum time-to-live of entries. Unused entries will expire after | |
94 | this period of time if there is no memory pressure on the pool (i.e. | |
95 | when the number of entries in the pool is very small). | |
77a538d5 | 96 | Measured in seconds. |
1da177e4 LT |
97 | |
98 | inet_peer_gc_mintime - INTEGER | |
99 | Minimum interval between garbage collection passes. This interval is | |
100 | in effect under high memory pressure on the pool. | |
77a538d5 | 101 | Measured in seconds. |
1da177e4 LT |
102 | |
103 | inet_peer_gc_maxtime - INTEGER | |
104 | Minimum interval between garbage collection passes. This interval is | |
105 | in effect under low (or absent) memory pressure on the pool. | |
77a538d5 | 106 | Measured in seconds. |
1da177e4 | 107 | |
e18f5feb | 108 | TCP variables: |
1da177e4 | 109 | |
ef56e622 SH |
110 | somaxconn - INTEGER |
111 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
112 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
113 | for TCP sockets. | |
114 | ||
9772efb9 | 115 | tcp_abc - INTEGER |
b3a8a40d SH |
116 | Controls Appropriate Byte Count (ABC) defined in RFC3465. |
117 | ABC is a way of increasing congestion window (cwnd) more slowly | |
118 | in response to partial acknowledgments. | |
119 | Possible values are: | |
120 | 0 increase cwnd once per acknowledgment (no ABC) | |
121 | 1 increase cwnd once per acknowledgment of full sized segment | |
122 | 2 allow increase cwnd by two if acknowledgment is | |
123 | of two segments to compensate for delayed acknowledgments. | |
124 | Default: 0 (off) | |
9772efb9 | 125 | |
ef56e622 SH |
126 | tcp_abort_on_overflow - BOOLEAN |
127 | If listening service is too slow to accept new connections, | |
128 | reset them. Default state is FALSE. It means that if overflow | |
129 | occurred due to a burst, connection will recover. Enable this | |
130 | option _only_ if you are really sure that listening daemon | |
131 | cannot be tuned to accept connections faster. Enabling this | |
132 | option can harm clients of your server. | |
1da177e4 | 133 | |
ef56e622 SH |
134 | tcp_adv_win_scale - INTEGER |
135 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
136 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
137 | if it is <= 0. | |
138 | Default: 2 | |
1da177e4 | 139 | |
ef56e622 SH |
140 | tcp_allowed_congestion_control - STRING |
141 | Show/set the congestion control choices available to non-privileged | |
142 | processes. The list is a subset of those listed in | |
143 | tcp_available_congestion_control. | |
144 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 145 | |
ef56e622 SH |
146 | tcp_app_win - INTEGER |
147 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
148 | buffer. Value 0 is special, it means that nothing is reserved. | |
149 | Default: 31 | |
1da177e4 | 150 | |
ef56e622 SH |
151 | tcp_available_congestion_control - STRING |
152 | Shows the available congestion control choices that are registered. | |
153 | More congestion control algorithms may be available as modules, | |
154 | but not loaded. | |
1da177e4 | 155 | |
71599cd1 | 156 | tcp_base_mss - INTEGER |
4edc2f34 SH |
157 | The initial value of search_low to be used by the packetization layer |
158 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
159 | this is the initial MSS used by the connection. | |
71599cd1 | 160 | |
ef56e622 SH |
161 | tcp_congestion_control - STRING |
162 | Set the congestion control algorithm to be used for new | |
163 | connections. The algorithm "reno" is always available, but | |
164 | additional choices may be available based on kernel configuration. | |
165 | Default is set as part of kernel configuration. | |
1da177e4 | 166 | |
ef56e622 SH |
167 | tcp_dsack - BOOLEAN |
168 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 169 | |
ef56e622 | 170 | tcp_ecn - BOOLEAN |
255cac91 IJ |
171 | Enable Explicit Congestion Notification (ECN) in TCP. ECN is only |
172 | used when both ends of the TCP flow support it. It is useful to | |
173 | avoid losses due to congestion (when the bottleneck router supports | |
174 | ECN). | |
175 | Possible values are: | |
176 | 0 disable ECN | |
177 | 1 ECN enabled | |
178 | 2 Only server-side ECN enabled. If the other end does | |
179 | not support ECN, behavior is like with ECN disabled. | |
180 | Default: 2 | |
ef56e622 SH |
181 | |
182 | tcp_fack - BOOLEAN | |
183 | Enable FACK congestion avoidance and fast retransmission. | |
184 | The value is not used, if tcp_sack is not enabled. | |
1da177e4 LT |
185 | |
186 | tcp_fin_timeout - INTEGER | |
187 | Time to hold socket in state FIN-WAIT-2, if it was closed | |
188 | by our side. Peer can be broken and never close its side, | |
189 | or even died unexpectedly. Default value is 60sec. | |
190 | Usual value used in 2.2 was 180 seconds, you may restore | |
191 | it, but remember that if your machine is even underloaded WEB server, | |
192 | you risk to overflow memory with kilotons of dead sockets, | |
193 | FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1, | |
194 | because they eat maximum 1.5K of memory, but they tend | |
195 | to live longer. Cf. tcp_max_orphans. | |
196 | ||
89808060 | 197 | tcp_frto - INTEGER |
cd99889c IJ |
198 | Enables Forward RTO-Recovery (F-RTO) defined in RFC4138. |
199 | F-RTO is an enhanced recovery algorithm for TCP retransmission | |
ef56e622 SH |
200 | timeouts. It is particularly beneficial in wireless environments |
201 | where packet loss is typically due to random radio interference | |
564262c1 | 202 | rather than intermediate router congestion. F-RTO is sender-side |
4edc2f34 SH |
203 | only modification. Therefore it does not require any support from |
204 | the peer. | |
205 | ||
cd99889c IJ |
206 | If set to 1, basic version is enabled. 2 enables SACK enhanced |
207 | F-RTO if flow uses SACK. The basic version can be used also when | |
564262c1 | 208 | SACK is in use though scenario(s) with it exists where F-RTO |
cd99889c IJ |
209 | interacts badly with the packet counting of the SACK enabled TCP |
210 | flow. | |
1da177e4 | 211 | |
89808060 IJ |
212 | tcp_frto_response - INTEGER |
213 | When F-RTO has detected that a TCP retransmission timeout was | |
214 | spurious (i.e, the timeout would have been avoided had TCP set a | |
215 | longer retransmission timeout), TCP has several options what to do | |
216 | next. Possible values are: | |
217 | 0 Rate halving based; a smooth and conservative response, | |
218 | results in halved cwnd and ssthresh after one RTT | |
219 | 1 Very conservative response; not recommended because even | |
220 | though being valid, it interacts poorly with the rest of | |
221 | Linux TCP, halves cwnd and ssthresh immediately | |
222 | 2 Aggressive response; undoes congestion control measures | |
223 | that are now known to be unnecessary (ignoring the | |
224 | possibility of a lost retransmission that would require | |
225 | TCP to be more cautious), cwnd and ssthresh are restored | |
226 | to the values prior timeout | |
227 | Default: 0 (rate halving based) | |
228 | ||
ef56e622 SH |
229 | tcp_keepalive_time - INTEGER |
230 | How often TCP sends out keepalive messages when keepalive is enabled. | |
231 | Default: 2hours. | |
1da177e4 | 232 | |
ef56e622 SH |
233 | tcp_keepalive_probes - INTEGER |
234 | How many keepalive probes TCP sends out, until it decides that the | |
235 | connection is broken. Default value: 9. | |
236 | ||
237 | tcp_keepalive_intvl - INTEGER | |
238 | How frequently the probes are send out. Multiplied by | |
239 | tcp_keepalive_probes it is time to kill not responding connection, | |
240 | after probes started. Default value: 75sec i.e. connection | |
241 | will be aborted after ~11 minutes of retries. | |
242 | ||
243 | tcp_low_latency - BOOLEAN | |
244 | If set, the TCP stack makes decisions that prefer lower | |
245 | latency as opposed to higher throughput. By default, this | |
246 | option is not set meaning that higher throughput is preferred. | |
247 | An example of an application where this default should be | |
248 | changed would be a Beowulf compute cluster. | |
249 | Default: 0 | |
1da177e4 LT |
250 | |
251 | tcp_max_orphans - INTEGER | |
252 | Maximal number of TCP sockets not attached to any user file handle, | |
253 | held by system. If this number is exceeded orphaned connections are | |
254 | reset immediately and warning is printed. This limit exists | |
255 | only to prevent simple DoS attacks, you _must_ not rely on this | |
256 | or lower the limit artificially, but rather increase it | |
257 | (probably, after increasing installed memory), | |
258 | if network conditions require more than default value, | |
259 | and tune network services to linger and kill such states | |
260 | more aggressively. Let me to remind again: each orphan eats | |
261 | up to ~64K of unswappable memory. | |
262 | ||
1da177e4 LT |
263 | tcp_max_syn_backlog - INTEGER |
264 | Maximal number of remembered connection requests, which are | |
265 | still did not receive an acknowledgment from connecting client. | |
266 | Default value is 1024 for systems with more than 128Mb of memory, | |
267 | and 128 for low memory machines. If server suffers of overload, | |
268 | try to increase this number. | |
269 | ||
ef56e622 SH |
270 | tcp_max_tw_buckets - INTEGER |
271 | Maximal number of timewait sockets held by system simultaneously. | |
272 | If this number is exceeded time-wait socket is immediately destroyed | |
273 | and warning is printed. This limit exists only to prevent | |
274 | simple DoS attacks, you _must_ not lower the limit artificially, | |
275 | but rather increase it (probably, after increasing installed memory), | |
276 | if network conditions require more than default value. | |
1da177e4 | 277 | |
ef56e622 SH |
278 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
279 | min: below this number of pages TCP is not bothered about its | |
280 | memory appetite. | |
1da177e4 | 281 | |
ef56e622 SH |
282 | pressure: when amount of memory allocated by TCP exceeds this number |
283 | of pages, TCP moderates its memory consumption and enters memory | |
284 | pressure mode, which is exited when memory consumption falls | |
285 | under "min". | |
1da177e4 | 286 | |
ef56e622 | 287 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 288 | |
ef56e622 SH |
289 | Defaults are calculated at boot time from amount of available |
290 | memory. | |
1da177e4 | 291 | |
71599cd1 | 292 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 293 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
294 | automatically size the buffer (no greater than tcp_rmem[2]) to |
295 | match the size required by the path for full throughput. Enabled by | |
296 | default. | |
297 | ||
298 | tcp_mtu_probing - INTEGER | |
299 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
300 | values: | |
301 | 0 - Disabled | |
302 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
303 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
304 | ||
305 | tcp_no_metrics_save - BOOLEAN | |
306 | By default, TCP saves various connection metrics in the route cache | |
307 | when the connection closes, so that connections established in the | |
308 | near future can use these to set initial conditions. Usually, this | |
309 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 310 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
311 | connections. |
312 | ||
ef56e622 SH |
313 | tcp_orphan_retries - INTEGER |
314 | How may times to retry before killing TCP connection, closed | |
315 | by our side. Default value 7 corresponds to ~50sec-16min | |
316 | depending on RTO. If you machine is loaded WEB server, | |
317 | you should think about lowering this value, such sockets | |
318 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
319 | |
320 | tcp_reordering - INTEGER | |
321 | Maximal reordering of packets in a TCP stream. | |
e18f5feb | 322 | Default: 3 |
1da177e4 LT |
323 | |
324 | tcp_retrans_collapse - BOOLEAN | |
325 | Bug-to-bug compatibility with some broken printers. | |
326 | On retransmit try to send bigger packets to work around bugs in | |
327 | certain TCP stacks. | |
328 | ||
ef56e622 SH |
329 | tcp_retries1 - INTEGER |
330 | How many times to retry before deciding that something is wrong | |
331 | and it is necessary to report this suspicion to network layer. | |
332 | Minimal RFC value is 3, it is default, which corresponds | |
333 | to ~3sec-8min depending on RTO. | |
1da177e4 | 334 | |
ef56e622 SH |
335 | tcp_retries2 - INTEGER |
336 | How may times to retry before killing alive TCP connection. | |
337 | RFC1122 says that the limit should be longer than 100 sec. | |
338 | It is too small number. Default value 15 corresponds to ~13-30min | |
339 | depending on RTO. | |
1da177e4 | 340 | |
ef56e622 SH |
341 | tcp_rfc1337 - BOOLEAN |
342 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
343 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
344 | assassination. | |
345 | Default: 0 | |
1da177e4 LT |
346 | |
347 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
348 | min: Minimal size of receive buffer used by TCP sockets. | |
349 | It is guaranteed to each TCP socket, even under moderate memory | |
350 | pressure. | |
351 | Default: 8K | |
352 | ||
53025f5e | 353 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
354 | This value overrides net.core.rmem_default used by other protocols. |
355 | Default: 87380 bytes. This value results in window of 65535 with | |
356 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
357 | less for default tcp_app_win. See below about these variables. | |
358 | ||
359 | max: maximal size of receive buffer allowed for automatically | |
360 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
361 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
362 | automatic tuning of that socket's receive buffer size, in which | |
363 | case this value is ignored. | |
364 | Default: between 87380B and 4MB, depending on RAM size. | |
1da177e4 | 365 | |
ef56e622 SH |
366 | tcp_sack - BOOLEAN |
367 | Enable select acknowledgments (SACKS). | |
1da177e4 | 368 | |
ef56e622 SH |
369 | tcp_slow_start_after_idle - BOOLEAN |
370 | If set, provide RFC2861 behavior and time out the congestion | |
371 | window after an idle period. An idle period is defined at | |
372 | the current RTO. If unset, the congestion window will not | |
373 | be timed out after an idle period. | |
374 | Default: 1 | |
1da177e4 | 375 | |
ef56e622 | 376 | tcp_stdurg - BOOLEAN |
4edc2f34 | 377 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
378 | Most hosts use the older BSD interpretation, so if you turn this on |
379 | Linux might not communicate correctly with them. | |
380 | Default: FALSE | |
1da177e4 | 381 | |
ef56e622 SH |
382 | tcp_synack_retries - INTEGER |
383 | Number of times SYNACKs for a passive TCP connection attempt will | |
384 | be retransmitted. Should not be higher than 255. Default value | |
385 | is 5, which corresponds to ~180seconds. | |
1da177e4 | 386 | |
ef56e622 SH |
387 | tcp_syncookies - BOOLEAN |
388 | Only valid when the kernel was compiled with CONFIG_SYNCOOKIES | |
389 | Send out syncookies when the syn backlog queue of a socket | |
4edc2f34 | 390 | overflows. This is to prevent against the common 'SYN flood attack' |
ef56e622 | 391 | Default: FALSE |
1da177e4 | 392 | |
ef56e622 SH |
393 | Note, that syncookies is fallback facility. |
394 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 395 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
396 | in your logs, but investigation shows that they occur |
397 | because of overload with legal connections, you should tune | |
398 | another parameters until this warning disappear. | |
399 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 400 | |
ef56e622 SH |
401 | syncookies seriously violate TCP protocol, do not allow |
402 | to use TCP extensions, can result in serious degradation | |
403 | of some services (f.e. SMTP relaying), visible not by you, | |
404 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 405 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 406 | is seriously misconfigured. |
1da177e4 | 407 | |
ef56e622 SH |
408 | tcp_syn_retries - INTEGER |
409 | Number of times initial SYNs for an active TCP connection attempt | |
410 | will be retransmitted. Should not be higher than 255. Default value | |
411 | is 5, which corresponds to ~180seconds. | |
412 | ||
413 | tcp_timestamps - BOOLEAN | |
414 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 415 | |
1da177e4 | 416 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
417 | This allows control over what percentage of the congestion window |
418 | can be consumed by a single TSO frame. | |
419 | The setting of this parameter is a choice between burstiness and | |
420 | building larger TSO frames. | |
421 | Default: 3 | |
1da177e4 | 422 | |
ef56e622 SH |
423 | tcp_tw_recycle - BOOLEAN |
424 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
425 | It should not be changed without advice/request of technical | |
426 | experts. | |
1da177e4 | 427 | |
ef56e622 SH |
428 | tcp_tw_reuse - BOOLEAN |
429 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
430 | safe from protocol viewpoint. Default value is 0. | |
431 | It should not be changed without advice/request of technical | |
432 | experts. | |
ce7bc3bf | 433 | |
ef56e622 SH |
434 | tcp_window_scaling - BOOLEAN |
435 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 436 | |
ef56e622 | 437 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 438 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 SH |
439 | Each TCP socket has rights to use it due to fact of its birth. |
440 | Default: 4K | |
9d7bcfc6 | 441 | |
53025f5e BF |
442 | default: initial size of send buffer used by TCP sockets. This |
443 | value overrides net.core.wmem_default used by other protocols. | |
444 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
445 | Default: 16K |
446 | ||
53025f5e BF |
447 | max: Maximal amount of memory allowed for automatically tuned |
448 | send buffers for TCP sockets. This value does not override | |
449 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
450 | automatic tuning of that socket's send buffer size, in which case | |
451 | this value is ignored. | |
452 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 453 | |
15d99e02 RJ |
454 | tcp_workaround_signed_windows - BOOLEAN |
455 | If set, assume no receipt of a window scaling option means the | |
456 | remote TCP is broken and treats the window as a signed quantity. | |
457 | If unset, assume the remote TCP is not broken even if we do | |
458 | not receive a window scaling option from them. | |
459 | Default: 0 | |
460 | ||
72d0b7a8 CL |
461 | tcp_dma_copybreak - INTEGER |
462 | Lower limit, in bytes, of the size of socket reads that will be | |
463 | offloaded to a DMA copy engine, if one is present in the system | |
464 | and CONFIG_NET_DMA is enabled. | |
465 | Default: 4096 | |
466 | ||
95766fff HA |
467 | UDP variables: |
468 | ||
469 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
470 | Number of pages allowed for queueing by all UDP sockets. | |
471 | ||
472 | min: Below this number of pages UDP is not bothered about its | |
473 | memory appetite. When amount of memory allocated by UDP exceeds | |
474 | this number, UDP starts to moderate memory usage. | |
475 | ||
476 | pressure: This value was introduced to follow format of tcp_mem. | |
477 | ||
478 | max: Number of pages allowed for queueing by all UDP sockets. | |
479 | ||
480 | Default is calculated at boot time from amount of available memory. | |
481 | ||
482 | udp_rmem_min - INTEGER | |
483 | Minimal size of receive buffer used by UDP sockets in moderation. | |
484 | Each UDP socket is able to use the size for receiving data, even if | |
485 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
486 | Default: 4096 | |
487 | ||
488 | udp_wmem_min - INTEGER | |
489 | Minimal size of send buffer used by UDP sockets in moderation. | |
490 | Each UDP socket is able to use the size for sending data, even if | |
491 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
492 | Default: 4096 | |
493 | ||
8802f616 PM |
494 | CIPSOv4 Variables: |
495 | ||
496 | cipso_cache_enable - BOOLEAN | |
497 | If set, enable additions to and lookups from the CIPSO label mapping | |
498 | cache. If unset, additions are ignored and lookups always result in a | |
499 | miss. However, regardless of the setting the cache is still | |
500 | invalidated when required when means you can safely toggle this on and | |
501 | off and the cache will always be "safe". | |
502 | Default: 1 | |
503 | ||
504 | cipso_cache_bucket_size - INTEGER | |
505 | The CIPSO label cache consists of a fixed size hash table with each | |
506 | hash bucket containing a number of cache entries. This variable limits | |
507 | the number of entries in each hash bucket; the larger the value the | |
508 | more CIPSO label mappings that can be cached. When the number of | |
509 | entries in a given hash bucket reaches this limit adding new entries | |
510 | causes the oldest entry in the bucket to be removed to make room. | |
511 | Default: 10 | |
512 | ||
513 | cipso_rbm_optfmt - BOOLEAN | |
514 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
515 | the CIPSO draft specification (see Documentation/netlabel for details). | |
516 | This means that when set the CIPSO tag will be padded with empty | |
517 | categories in order to make the packet data 32-bit aligned. | |
518 | Default: 0 | |
519 | ||
520 | cipso_rbm_structvalid - BOOLEAN | |
521 | If set, do a very strict check of the CIPSO option when | |
522 | ip_options_compile() is called. If unset, relax the checks done during | |
523 | ip_options_compile(). Either way is "safe" as errors are caught else | |
524 | where in the CIPSO processing code but setting this to 0 (False) should | |
525 | result in less work (i.e. it should be faster) but could cause problems | |
526 | with other implementations that require strict checking. | |
527 | Default: 0 | |
528 | ||
1da177e4 LT |
529 | IP Variables: |
530 | ||
531 | ip_local_port_range - 2 INTEGERS | |
532 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 533 | choose the local port. The first number is the first, the |
1da177e4 LT |
534 | second the last local port number. Default value depends on |
535 | amount of memory available on the system: | |
536 | > 128Mb 32768-61000 | |
537 | < 128Mb 1024-4999 or even less. | |
538 | This number defines number of active connections, which this | |
539 | system can issue simultaneously to systems not supporting | |
540 | TCP extensions (timestamps). With tcp_tw_recycle enabled | |
541 | (i.e. by default) range 1024-4999 is enough to issue up to | |
542 | 2000 connections per second to systems supporting timestamps. | |
543 | ||
544 | ip_nonlocal_bind - BOOLEAN | |
545 | If set, allows processes to bind() to non-local IP addresses, | |
546 | which can be quite useful - but may break some applications. | |
547 | Default: 0 | |
548 | ||
549 | ip_dynaddr - BOOLEAN | |
550 | If set non-zero, enables support for dynamic addresses. | |
551 | If set to a non-zero value larger than 1, a kernel log | |
552 | message will be printed when dynamic address rewriting | |
553 | occurs. | |
554 | Default: 0 | |
555 | ||
556 | icmp_echo_ignore_all - BOOLEAN | |
7ce31246 DM |
557 | If set non-zero, then the kernel will ignore all ICMP ECHO |
558 | requests sent to it. | |
559 | Default: 0 | |
560 | ||
1da177e4 | 561 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
562 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
563 | TIMESTAMP requests sent to it via broadcast/multicast. | |
564 | Default: 1 | |
1da177e4 LT |
565 | |
566 | icmp_ratelimit - INTEGER | |
567 | Limit the maximal rates for sending ICMP packets whose type matches | |
568 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
569 | 0 to disable any limiting, |
570 | otherwise the minimal space between responses in milliseconds. | |
571 | Default: 1000 | |
1da177e4 LT |
572 | |
573 | icmp_ratemask - INTEGER | |
574 | Mask made of ICMP types for which rates are being limited. | |
575 | Significant bits: IHGFEDCBA9876543210 | |
576 | Default mask: 0000001100000011000 (6168) | |
577 | ||
578 | Bit definitions (see include/linux/icmp.h): | |
579 | 0 Echo Reply | |
580 | 3 Destination Unreachable * | |
581 | 4 Source Quench * | |
582 | 5 Redirect | |
583 | 8 Echo Request | |
584 | B Time Exceeded * | |
585 | C Parameter Problem * | |
586 | D Timestamp Request | |
587 | E Timestamp Reply | |
588 | F Info Request | |
589 | G Info Reply | |
590 | H Address Mask Request | |
591 | I Address Mask Reply | |
592 | ||
593 | * These are rate limited by default (see default mask above) | |
594 | ||
595 | icmp_ignore_bogus_error_responses - BOOLEAN | |
596 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
597 | frames. Such violations are normally logged via a kernel warning. | |
598 | If this is set to TRUE, the kernel will not give such warnings, which | |
599 | will avoid log file clutter. | |
600 | Default: FALSE | |
601 | ||
95f7daf1 H |
602 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
603 | ||
604 | If zero, icmp error messages are sent with the primary address of | |
605 | the exiting interface. | |
e18f5feb | 606 | |
95f7daf1 H |
607 | If non-zero, the message will be sent with the primary address of |
608 | the interface that received the packet that caused the icmp error. | |
609 | This is the behaviour network many administrators will expect from | |
610 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 611 | much easier. |
95f7daf1 H |
612 | |
613 | Note that if no primary address exists for the interface selected, | |
614 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 615 | has one will be used regardless of this setting. |
95f7daf1 H |
616 | |
617 | Default: 0 | |
618 | ||
1da177e4 LT |
619 | igmp_max_memberships - INTEGER |
620 | Change the maximum number of multicast groups we can subscribe to. | |
621 | Default: 20 | |
622 | ||
e18f5feb | 623 | conf/interface/* changes special settings per interface (where "interface" is |
1da177e4 LT |
624 | the name of your network interface) |
625 | conf/all/* is special, changes the settings for all interfaces | |
626 | ||
627 | ||
628 | log_martians - BOOLEAN | |
629 | Log packets with impossible addresses to kernel log. | |
630 | log_martians for the interface will be enabled if at least one of | |
631 | conf/{all,interface}/log_martians is set to TRUE, | |
632 | it will be disabled otherwise | |
633 | ||
634 | accept_redirects - BOOLEAN | |
635 | Accept ICMP redirect messages. | |
636 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
637 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
638 | forwarding for the interface is enabled | |
1da177e4 | 639 | or |
e18f5feb JDB |
640 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
641 | case forwarding for the interface is disabled | |
1da177e4 LT |
642 | accept_redirects for the interface will be disabled otherwise |
643 | default TRUE (host) | |
644 | FALSE (router) | |
645 | ||
646 | forwarding - BOOLEAN | |
647 | Enable IP forwarding on this interface. | |
648 | ||
649 | mc_forwarding - BOOLEAN | |
650 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
651 | and a multicast routing daemon is required. | |
e18f5feb JDB |
652 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
653 | routing for the interface | |
1da177e4 LT |
654 | |
655 | medium_id - INTEGER | |
656 | Integer value used to differentiate the devices by the medium they | |
657 | are attached to. Two devices can have different id values when | |
658 | the broadcast packets are received only on one of them. | |
659 | The default value 0 means that the device is the only interface | |
660 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 661 | |
1da177e4 LT |
662 | Currently, it is used to change the proxy_arp behavior: |
663 | the proxy_arp feature is enabled for packets forwarded between | |
664 | two devices attached to different media. | |
665 | ||
666 | proxy_arp - BOOLEAN | |
667 | Do proxy arp. | |
668 | proxy_arp for the interface will be enabled if at least one of | |
669 | conf/{all,interface}/proxy_arp is set to TRUE, | |
670 | it will be disabled otherwise | |
671 | ||
672 | shared_media - BOOLEAN | |
673 | Send(router) or accept(host) RFC1620 shared media redirects. | |
674 | Overrides ip_secure_redirects. | |
675 | shared_media for the interface will be enabled if at least one of | |
676 | conf/{all,interface}/shared_media is set to TRUE, | |
677 | it will be disabled otherwise | |
678 | default TRUE | |
679 | ||
680 | secure_redirects - BOOLEAN | |
681 | Accept ICMP redirect messages only for gateways, | |
682 | listed in default gateway list. | |
683 | secure_redirects for the interface will be enabled if at least one of | |
684 | conf/{all,interface}/secure_redirects is set to TRUE, | |
685 | it will be disabled otherwise | |
686 | default TRUE | |
687 | ||
688 | send_redirects - BOOLEAN | |
689 | Send redirects, if router. | |
690 | send_redirects for the interface will be enabled if at least one of | |
691 | conf/{all,interface}/send_redirects is set to TRUE, | |
692 | it will be disabled otherwise | |
693 | Default: TRUE | |
694 | ||
695 | bootp_relay - BOOLEAN | |
696 | Accept packets with source address 0.b.c.d destined | |
697 | not to this host as local ones. It is supposed, that | |
698 | BOOTP relay daemon will catch and forward such packets. | |
699 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
700 | for the interface | |
701 | default FALSE | |
702 | Not Implemented Yet. | |
703 | ||
704 | accept_source_route - BOOLEAN | |
705 | Accept packets with SRR option. | |
706 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
707 | with SRR option on the interface | |
708 | default TRUE (router) | |
709 | FALSE (host) | |
710 | ||
c1cf8422 | 711 | rp_filter - INTEGER |
1da177e4 | 712 | 0 - No source validation. |
c1cf8422 SH |
713 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
714 | Each incoming packet is tested against the FIB and if the interface | |
715 | is not the best reverse path the packet check will fail. | |
716 | By default failed packets are discarded. | |
717 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
718 | Each incoming packet's source address is also tested against the FIB | |
719 | and if the source address is not reachable via any interface | |
720 | the packet check will fail. | |
721 | ||
e18f5feb | 722 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 723 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 724 | or other complicated routing, then loose mode is recommended. |
c1cf8422 SH |
725 | |
726 | conf/all/rp_filter must also be set to non-zero to do source validation | |
1da177e4 LT |
727 | on the interface |
728 | ||
729 | Default value is 0. Note that some distributions enable it | |
730 | in startup scripts. | |
731 | ||
732 | arp_filter - BOOLEAN | |
733 | 1 - Allows you to have multiple network interfaces on the same | |
734 | subnet, and have the ARPs for each interface be answered | |
735 | based on whether or not the kernel would route a packet from | |
736 | the ARP'd IP out that interface (therefore you must use source | |
737 | based routing for this to work). In other words it allows control | |
738 | of which cards (usually 1) will respond to an arp request. | |
739 | ||
740 | 0 - (default) The kernel can respond to arp requests with addresses | |
741 | from other interfaces. This may seem wrong but it usually makes | |
742 | sense, because it increases the chance of successful communication. | |
743 | IP addresses are owned by the complete host on Linux, not by | |
744 | particular interfaces. Only for more complex setups like load- | |
745 | balancing, does this behaviour cause problems. | |
746 | ||
747 | arp_filter for the interface will be enabled if at least one of | |
748 | conf/{all,interface}/arp_filter is set to TRUE, | |
749 | it will be disabled otherwise | |
750 | ||
751 | arp_announce - INTEGER | |
752 | Define different restriction levels for announcing the local | |
753 | source IP address from IP packets in ARP requests sent on | |
754 | interface: | |
755 | 0 - (default) Use any local address, configured on any interface | |
756 | 1 - Try to avoid local addresses that are not in the target's | |
757 | subnet for this interface. This mode is useful when target | |
758 | hosts reachable via this interface require the source IP | |
759 | address in ARP requests to be part of their logical network | |
760 | configured on the receiving interface. When we generate the | |
761 | request we will check all our subnets that include the | |
762 | target IP and will preserve the source address if it is from | |
763 | such subnet. If there is no such subnet we select source | |
764 | address according to the rules for level 2. | |
765 | 2 - Always use the best local address for this target. | |
766 | In this mode we ignore the source address in the IP packet | |
767 | and try to select local address that we prefer for talks with | |
768 | the target host. Such local address is selected by looking | |
769 | for primary IP addresses on all our subnets on the outgoing | |
770 | interface that include the target IP address. If no suitable | |
771 | local address is found we select the first local address | |
772 | we have on the outgoing interface or on all other interfaces, | |
773 | with the hope we will receive reply for our request and | |
774 | even sometimes no matter the source IP address we announce. | |
775 | ||
776 | The max value from conf/{all,interface}/arp_announce is used. | |
777 | ||
778 | Increasing the restriction level gives more chance for | |
779 | receiving answer from the resolved target while decreasing | |
780 | the level announces more valid sender's information. | |
781 | ||
782 | arp_ignore - INTEGER | |
783 | Define different modes for sending replies in response to | |
784 | received ARP requests that resolve local target IP addresses: | |
785 | 0 - (default): reply for any local target IP address, configured | |
786 | on any interface | |
787 | 1 - reply only if the target IP address is local address | |
788 | configured on the incoming interface | |
789 | 2 - reply only if the target IP address is local address | |
790 | configured on the incoming interface and both with the | |
791 | sender's IP address are part from same subnet on this interface | |
792 | 3 - do not reply for local addresses configured with scope host, | |
793 | only resolutions for global and link addresses are replied | |
794 | 4-7 - reserved | |
795 | 8 - do not reply for all local addresses | |
796 | ||
797 | The max value from conf/{all,interface}/arp_ignore is used | |
798 | when ARP request is received on the {interface} | |
799 | ||
eefef1cf SH |
800 | arp_notify - BOOLEAN |
801 | Define mode for notification of address and device changes. | |
802 | 0 - (default): do nothing | |
803 | 1 - Generate gratuitous arp replies when device is brought up | |
804 | or hardware address changes. | |
805 | ||
c1b1bce8 NH |
806 | arp_accept - BOOLEAN |
807 | Define behavior when gratuitous arp replies are received: | |
808 | 0 - drop gratuitous arp frames | |
809 | 1 - accept gratuitous arp frames | |
810 | ||
1da177e4 LT |
811 | app_solicit - INTEGER |
812 | The maximum number of probes to send to the user space ARP daemon | |
813 | via netlink before dropping back to multicast probes (see | |
814 | mcast_solicit). Defaults to 0. | |
815 | ||
816 | disable_policy - BOOLEAN | |
817 | Disable IPSEC policy (SPD) for this interface | |
818 | ||
819 | disable_xfrm - BOOLEAN | |
820 | Disable IPSEC encryption on this interface, whatever the policy | |
821 | ||
822 | ||
823 | ||
824 | tag - INTEGER | |
825 | Allows you to write a number, which can be used as required. | |
826 | Default value is 0. | |
827 | ||
1da177e4 LT |
828 | Alexey Kuznetsov. |
829 | kuznet@ms2.inr.ac.ru | |
830 | ||
831 | Updated by: | |
832 | Andi Kleen | |
833 | ak@muc.de | |
834 | Nicolas Delon | |
835 | delon.nicolas@wanadoo.fr | |
836 | ||
837 | ||
838 | ||
839 | ||
840 | /proc/sys/net/ipv6/* Variables: | |
841 | ||
842 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
843 | apply to IPv6 [XXX?]. | |
844 | ||
845 | bindv6only - BOOLEAN | |
846 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 847 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
848 | only. |
849 | TRUE: disable IPv4-mapped address feature | |
850 | FALSE: enable IPv4-mapped address feature | |
851 | ||
852 | Default: FALSE (as specified in RFC2553bis) | |
853 | ||
854 | IPv6 Fragmentation: | |
855 | ||
856 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 857 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
858 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
859 | the fragment handler will toss packets until ip6frag_low_thresh | |
860 | is reached. | |
e18f5feb | 861 | |
1da177e4 | 862 | ip6frag_low_thresh - INTEGER |
e18f5feb | 863 | See ip6frag_high_thresh |
1da177e4 LT |
864 | |
865 | ip6frag_time - INTEGER | |
866 | Time in seconds to keep an IPv6 fragment in memory. | |
867 | ||
868 | ip6frag_secret_interval - INTEGER | |
e18f5feb | 869 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
870 | for the hash secret) for IPv6 fragments. |
871 | Default: 600 | |
872 | ||
873 | conf/default/*: | |
874 | Change the interface-specific default settings. | |
875 | ||
876 | ||
877 | conf/all/*: | |
e18f5feb | 878 | Change all the interface-specific settings. |
1da177e4 LT |
879 | |
880 | [XXX: Other special features than forwarding?] | |
881 | ||
882 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 883 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 884 | |
e18f5feb | 885 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
886 | to control which interfaces may forward packets and which not. |
887 | ||
e18f5feb | 888 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
889 | 'forwarding' to the specified value. See below for details. |
890 | ||
891 | This referred to as global forwarding. | |
892 | ||
fbea49e1 YH |
893 | proxy_ndp - BOOLEAN |
894 | Do proxy ndp. | |
895 | ||
1da177e4 LT |
896 | conf/interface/*: |
897 | Change special settings per interface. | |
898 | ||
e18f5feb | 899 | The functional behaviour for certain settings is different |
1da177e4 LT |
900 | depending on whether local forwarding is enabled or not. |
901 | ||
902 | accept_ra - BOOLEAN | |
903 | Accept Router Advertisements; autoconfigure using them. | |
e18f5feb | 904 | |
1da177e4 LT |
905 | Functional default: enabled if local forwarding is disabled. |
906 | disabled if local forwarding is enabled. | |
907 | ||
65f5c7c1 YH |
908 | accept_ra_defrtr - BOOLEAN |
909 | Learn default router in Router Advertisement. | |
910 | ||
911 | Functional default: enabled if accept_ra is enabled. | |
912 | disabled if accept_ra is disabled. | |
913 | ||
c4fd30eb | 914 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 915 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
916 | |
917 | Functional default: enabled if accept_ra is enabled. | |
918 | disabled if accept_ra is disabled. | |
919 | ||
09c884d4 YH |
920 | accept_ra_rt_info_max_plen - INTEGER |
921 | Maximum prefix length of Route Information in RA. | |
922 | ||
923 | Route Information w/ prefix larger than or equal to this | |
924 | variable shall be ignored. | |
925 | ||
926 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
927 | -1 if accept_ra_rtr_pref is disabled. | |
928 | ||
930d6ff2 YH |
929 | accept_ra_rtr_pref - BOOLEAN |
930 | Accept Router Preference in RA. | |
931 | ||
932 | Functional default: enabled if accept_ra is enabled. | |
933 | disabled if accept_ra is disabled. | |
934 | ||
1da177e4 LT |
935 | accept_redirects - BOOLEAN |
936 | Accept Redirects. | |
937 | ||
938 | Functional default: enabled if local forwarding is disabled. | |
939 | disabled if local forwarding is enabled. | |
940 | ||
0bcbc926 YH |
941 | accept_source_route - INTEGER |
942 | Accept source routing (routing extension header). | |
943 | ||
bb4dbf9e | 944 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
945 | < 0: Do not accept routing header. |
946 | ||
947 | Default: 0 | |
948 | ||
1da177e4 | 949 | autoconf - BOOLEAN |
e18f5feb | 950 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
951 | Advertisements. |
952 | ||
c4fd30eb YH |
953 | Functional default: enabled if accept_ra_pinfo is enabled. |
954 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
955 | |
956 | dad_transmits - INTEGER | |
957 | The amount of Duplicate Address Detection probes to send. | |
958 | Default: 1 | |
e18f5feb | 959 | |
1da177e4 | 960 | forwarding - BOOLEAN |
e18f5feb | 961 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 962 | |
e18f5feb | 963 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
964 | interfaces; mixed router/host scenarios are rather uncommon. |
965 | ||
966 | FALSE: | |
967 | ||
968 | By default, Host behaviour is assumed. This means: | |
969 | ||
970 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
971 | 2. Router Solicitations are being sent when necessary. | |
e18f5feb | 972 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
973 | Advertisements (and do autoconfiguration). |
974 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
975 | ||
976 | TRUE: | |
977 | ||
e18f5feb | 978 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
979 | This means exactly the reverse from the above: |
980 | ||
981 | 1. IsRouter flag is set in Neighbour Advertisements. | |
982 | 2. Router Solicitations are not sent. | |
983 | 3. Router Advertisements are ignored. | |
984 | 4. Redirects are ignored. | |
985 | ||
986 | Default: FALSE if global forwarding is disabled (default), | |
987 | otherwise TRUE. | |
988 | ||
989 | hop_limit - INTEGER | |
990 | Default Hop Limit to set. | |
991 | Default: 64 | |
992 | ||
993 | mtu - INTEGER | |
994 | Default Maximum Transfer Unit | |
995 | Default: 1280 (IPv6 required minimum) | |
996 | ||
52e16356 YH |
997 | router_probe_interval - INTEGER |
998 | Minimum interval (in seconds) between Router Probing described | |
999 | in RFC4191. | |
1000 | ||
1001 | Default: 60 | |
1002 | ||
1da177e4 LT |
1003 | router_solicitation_delay - INTEGER |
1004 | Number of seconds to wait after interface is brought up | |
1005 | before sending Router Solicitations. | |
1006 | Default: 1 | |
1007 | ||
1008 | router_solicitation_interval - INTEGER | |
1009 | Number of seconds to wait between Router Solicitations. | |
1010 | Default: 4 | |
1011 | ||
1012 | router_solicitations - INTEGER | |
e18f5feb | 1013 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1014 | routers are present. |
1015 | Default: 3 | |
1016 | ||
1017 | use_tempaddr - INTEGER | |
1018 | Preference for Privacy Extensions (RFC3041). | |
1019 | <= 0 : disable Privacy Extensions | |
1020 | == 1 : enable Privacy Extensions, but prefer public | |
1021 | addresses over temporary addresses. | |
1022 | > 1 : enable Privacy Extensions and prefer temporary | |
1023 | addresses over public addresses. | |
1024 | Default: 0 (for most devices) | |
1025 | -1 (for point-to-point devices and loopback devices) | |
1026 | ||
1027 | temp_valid_lft - INTEGER | |
1028 | valid lifetime (in seconds) for temporary addresses. | |
1029 | Default: 604800 (7 days) | |
1030 | ||
1031 | temp_prefered_lft - INTEGER | |
1032 | Preferred lifetime (in seconds) for temporary addresses. | |
1033 | Default: 86400 (1 day) | |
1034 | ||
1035 | max_desync_factor - INTEGER | |
1036 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1037 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1038 | other and generate new addresses at exactly the same time. |
1039 | value is in seconds. | |
1040 | Default: 600 | |
e18f5feb | 1041 | |
1da177e4 LT |
1042 | regen_max_retry - INTEGER |
1043 | Number of attempts before give up attempting to generate | |
1044 | valid temporary addresses. | |
1045 | Default: 5 | |
1046 | ||
1047 | max_addresses - INTEGER | |
1048 | Number of maximum addresses per interface. 0 disables limitation. | |
e18f5feb JDB |
1049 | It is recommended not set too large value (or 0) because it would |
1050 | be too easy way to crash kernel to allow to create too much of | |
1da177e4 LT |
1051 | autoconfigured addresses. |
1052 | Default: 16 | |
1053 | ||
778d80be | 1054 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1055 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1056 | will be dynamically set to TRUE if DAD fails for the link-local | |
1057 | address. | |
778d80be YH |
1058 | Default: FALSE (enable IPv6 operation) |
1059 | ||
56d417b1 BH |
1060 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1061 | it will dynamically create a link-local address on the given | |
1062 | interface and start Duplicate Address Detection, if necessary. | |
1063 | ||
1064 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1065 | it will dynamically delete all address on the given interface. | |
1066 | ||
1b34be74 YH |
1067 | accept_dad - INTEGER |
1068 | Whether to accept DAD (Duplicate Address Detection). | |
1069 | 0: Disable DAD | |
1070 | 1: Enable DAD (default) | |
1071 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1072 | link-local address has been found. | |
1073 | ||
1da177e4 LT |
1074 | icmp/*: |
1075 | ratelimit - INTEGER | |
1076 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1077 | 0 to disable any limiting, |
1078 | otherwise the minimal space between responses in milliseconds. | |
1079 | Default: 1000 | |
1da177e4 LT |
1080 | |
1081 | ||
1082 | IPv6 Update by: | |
1083 | Pekka Savola <pekkas@netcore.fi> | |
1084 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1085 | ||
1086 | ||
1087 | /proc/sys/net/bridge/* Variables: | |
1088 | ||
1089 | bridge-nf-call-arptables - BOOLEAN | |
1090 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1091 | 0 : disable this. | |
1092 | Default: 1 | |
1093 | ||
1094 | bridge-nf-call-iptables - BOOLEAN | |
1095 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1096 | 0 : disable this. | |
1097 | Default: 1 | |
1098 | ||
1099 | bridge-nf-call-ip6tables - BOOLEAN | |
1100 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1101 | 0 : disable this. | |
1102 | Default: 1 | |
1103 | ||
1104 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1105 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1106 | 0 : disable this. | |
1107 | Default: 1 | |
1108 | ||
1109 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1110 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 LT |
1111 | 0 : disable this. |
1112 | Default: 1 | |
1113 | ||
1114 | ||
32e8d494 VY |
1115 | proc/sys/net/sctp/* Variables: |
1116 | ||
1117 | addip_enable - BOOLEAN | |
1118 | Enable or disable extension of Dynamic Address Reconfiguration | |
1119 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1120 | the ability to dynamically add and remove new addresses for the SCTP | |
1121 | associations. | |
1122 | ||
1123 | 1: Enable extension. | |
1124 | ||
1125 | 0: Disable extension. | |
1126 | ||
1127 | Default: 0 | |
1128 | ||
1129 | addip_noauth_enable - BOOLEAN | |
1130 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1131 | authentication to protect the operations of adding or removing new | |
1132 | addresses. This requirement is mandated so that unauthorized hosts | |
1133 | would not be able to hijack associations. However, older | |
1134 | implementations may not have implemented this requirement while | |
1135 | allowing the ADD-IP extension. For reasons of interoperability, | |
1136 | we provide this variable to control the enforcement of the | |
1137 | authentication requirement. | |
1138 | ||
1139 | 1: Allow ADD-IP extension to be used without authentication. This | |
1140 | should only be set in a closed environment for interoperability | |
1141 | with older implementations. | |
1142 | ||
1143 | 0: Enforce the authentication requirement | |
1144 | ||
1145 | Default: 0 | |
1146 | ||
1147 | auth_enable - BOOLEAN | |
1148 | Enable or disable Authenticated Chunks extension. This extension | |
1149 | provides the ability to send and receive authenticated chunks and is | |
1150 | required for secure operation of Dynamic Address Reconfiguration | |
1151 | (ADD-IP) extension. | |
1152 | ||
1153 | 1: Enable this extension. | |
1154 | 0: Disable this extension. | |
1155 | ||
1156 | Default: 0 | |
1157 | ||
1158 | prsctp_enable - BOOLEAN | |
1159 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1160 | is used to notify peers that a given DATA should no longer be expected. | |
1161 | ||
1162 | 1: Enable extension | |
1163 | 0: Disable | |
1164 | ||
1165 | Default: 1 | |
1166 | ||
1167 | max_burst - INTEGER | |
1168 | The limit of the number of new packets that can be initially sent. It | |
1169 | controls how bursty the generated traffic can be. | |
1170 | ||
1171 | Default: 4 | |
1172 | ||
1173 | association_max_retrans - INTEGER | |
1174 | Set the maximum number for retransmissions that an association can | |
1175 | attempt deciding that the remote end is unreachable. If this value | |
1176 | is exceeded, the association is terminated. | |
1177 | ||
1178 | Default: 10 | |
1179 | ||
1180 | max_init_retransmits - INTEGER | |
1181 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1182 | that an association will attempt before declaring the destination | |
1183 | unreachable and terminating. | |
1184 | ||
1185 | Default: 8 | |
1186 | ||
1187 | path_max_retrans - INTEGER | |
1188 | The maximum number of retransmissions that will be attempted on a given | |
1189 | path. Once this threshold is exceeded, the path is considered | |
1190 | unreachable, and new traffic will use a different path when the | |
1191 | association is multihomed. | |
1192 | ||
1193 | Default: 5 | |
1194 | ||
1195 | rto_initial - INTEGER | |
1196 | The initial round trip timeout value in milliseconds that will be used | |
1197 | in calculating round trip times. This is the initial time interval | |
1198 | for retransmissions. | |
1199 | ||
1200 | Default: 3000 | |
1da177e4 | 1201 | |
32e8d494 VY |
1202 | rto_max - INTEGER |
1203 | The maximum value (in milliseconds) of the round trip timeout. This | |
1204 | is the largest time interval that can elapse between retransmissions. | |
1205 | ||
1206 | Default: 60000 | |
1207 | ||
1208 | rto_min - INTEGER | |
1209 | The minimum value (in milliseconds) of the round trip timeout. This | |
1210 | is the smallest time interval the can elapse between retransmissions. | |
1211 | ||
1212 | Default: 1000 | |
1213 | ||
1214 | hb_interval - INTEGER | |
1215 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1216 | are sent at the specified interval on idle paths to probe the state of | |
1217 | a given path between 2 associations. | |
1218 | ||
1219 | Default: 30000 | |
1220 | ||
1221 | sack_timeout - INTEGER | |
1222 | The amount of time (in milliseconds) that the implementation will wait | |
1223 | to send a SACK. | |
1224 | ||
1225 | Default: 200 | |
1226 | ||
1227 | valid_cookie_life - INTEGER | |
1228 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1229 | is used during association establishment. | |
1230 | ||
1231 | Default: 60000 | |
1232 | ||
1233 | cookie_preserve_enable - BOOLEAN | |
1234 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1235 | that is used during the establishment phase of SCTP association | |
1236 | ||
1237 | 1: Enable cookie lifetime extension. | |
1238 | 0: Disable | |
1239 | ||
1240 | Default: 1 | |
1241 | ||
1242 | rcvbuf_policy - INTEGER | |
1243 | Determines if the receive buffer is attributed to the socket or to | |
1244 | association. SCTP supports the capability to create multiple | |
1245 | associations on a single socket. When using this capability, it is | |
1246 | possible that a single stalled association that's buffering a lot | |
1247 | of data may block other associations from delivering their data by | |
1248 | consuming all of the receive buffer space. To work around this, | |
1249 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1250 | to each association instead of the socket. This prevents the described | |
1251 | blocking. | |
1252 | ||
1253 | 1: rcvbuf space is per association | |
1254 | 0: recbuf space is per socket | |
1255 | ||
1256 | Default: 0 | |
1257 | ||
1258 | sndbuf_policy - INTEGER | |
1259 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1260 | ||
1261 | 1: Send buffer is tracked per association | |
1262 | 0: Send buffer is tracked per socket. | |
1263 | ||
1264 | Default: 0 | |
1265 | ||
1266 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1267 | Number of pages allowed for queueing by all SCTP sockets. | |
1268 | ||
1269 | min: Below this number of pages SCTP is not bothered about its | |
1270 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1271 | this number, SCTP starts to moderate memory usage. | |
1272 | ||
1273 | pressure: This value was introduced to follow format of tcp_mem. | |
1274 | ||
1275 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1276 | ||
1277 | Default is calculated at boot time from amount of available memory. | |
1278 | ||
1279 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
1280 | See tcp_rmem for a description. | |
1281 | ||
1282 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
1283 | See tcp_wmem for a description. | |
1284 | ||
1da177e4 | 1285 | |
4edc2f34 | 1286 | /proc/sys/net/core/* |
705efc3b WT |
1287 | dev_weight - INTEGER |
1288 | The maximum number of packets that kernel can handle on a NAPI | |
1289 | interrupt, it's a Per-CPU variable. | |
1290 | ||
1291 | Default: 64 | |
4edc2f34 SH |
1292 | |
1293 | /proc/sys/net/unix/* | |
705efc3b WT |
1294 | max_dgram_qlen - INTEGER |
1295 | The maximum length of dgram socket receive queue | |
1296 | ||
1297 | Default: 10 | |
1298 | ||
1299 | ||
1300 | UNDOCUMENTED: | |
4edc2f34 SH |
1301 | |
1302 | /proc/sys/net/irda/* | |
1303 | fast_poll_increase FIXME | |
1304 | warn_noreply_time FIXME | |
1305 | discovery_slots FIXME | |
1306 | slot_timeout FIXME | |
1307 | max_baud_rate FIXME | |
1308 | discovery_timeout FIXME | |
1309 | lap_keepalive_time FIXME | |
1310 | max_noreply_time FIXME | |
1311 | max_tx_data_size FIXME | |
1312 | max_tx_window FIXME | |
1313 | min_tx_turn_time FIXME |