Commit | Line | Data |
---|---|---|
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 | |
cc6f02dd ED |
14 | Default value of TTL field (Time To Live) for outgoing (but not |
15 | forwarded) IP packets. Should be between 1 and 255 inclusive. | |
16 | Default: 64 (as recommended by RFC1700) | |
1da177e4 LT |
17 | |
18 | ip_no_pmtu_disc - BOOLEAN | |
19 | Disable Path MTU Discovery. | |
20 | default FALSE | |
21 | ||
22 | min_pmtu - INTEGER | |
20db93c3 | 23 | default 552 - minimum discovered Path MTU |
1da177e4 | 24 | |
cbaf087a BG |
25 | route/max_size - INTEGER |
26 | Maximum number of routes allowed in the kernel. Increase | |
27 | this when using large numbers of interfaces and/or routes. | |
28 | ||
29 | neigh/default/gc_thresh3 - INTEGER | |
30 | Maximum number of neighbor entries allowed. Increase this | |
31 | when using large numbers of interfaces and when communicating | |
32 | with large numbers of directly-connected peers. | |
33 | ||
8b5c171b ED |
34 | neigh/default/unres_qlen_bytes - INTEGER |
35 | The maximum number of bytes which may be used by packets | |
36 | queued for each unresolved address by other network layers. | |
37 | (added in linux 3.3) | |
38 | ||
39 | neigh/default/unres_qlen - INTEGER | |
40 | The maximum number of packets which may be queued for each | |
41 | unresolved address by other network layers. | |
42 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
43 | ||
1da177e4 LT |
44 | mtu_expires - INTEGER |
45 | Time, in seconds, that cached PMTU information is kept. | |
46 | ||
47 | min_adv_mss - INTEGER | |
48 | The advertised MSS depends on the first hop route MTU, but will | |
49 | never be lower than this setting. | |
50 | ||
51 | IP Fragmentation: | |
52 | ||
53 | ipfrag_high_thresh - INTEGER | |
e18f5feb | 54 | Maximum memory used to reassemble IP fragments. When |
1da177e4 LT |
55 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
56 | the fragment handler will toss packets until ipfrag_low_thresh | |
57 | is reached. | |
e18f5feb | 58 | |
1da177e4 | 59 | ipfrag_low_thresh - INTEGER |
e18f5feb | 60 | See ipfrag_high_thresh |
1da177e4 LT |
61 | |
62 | ipfrag_time - INTEGER | |
e18f5feb | 63 | Time in seconds to keep an IP fragment in memory. |
1da177e4 LT |
64 | |
65 | ipfrag_secret_interval - INTEGER | |
e18f5feb | 66 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
67 | for the hash secret) for IP fragments. |
68 | Default: 600 | |
69 | ||
89cee8b1 | 70 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
71 | ipfrag_max_dist is a non-negative integer value which defines the |
72 | maximum "disorder" which is allowed among fragments which share a | |
73 | common IP source address. Note that reordering of packets is | |
74 | not unusual, but if a large number of fragments arrive from a source | |
75 | IP address while a particular fragment queue remains incomplete, it | |
76 | probably indicates that one or more fragments belonging to that queue | |
77 | have been lost. When ipfrag_max_dist is positive, an additional check | |
78 | is done on fragments before they are added to a reassembly queue - if | |
79 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
80 | address between additions to any IP fragment queue using that source | |
81 | address, it's presumed that one or more fragments in the queue are | |
82 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
83 | started. An ipfrag_max_dist value of zero disables this check. |
84 | ||
85 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
86 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
87 | reordering of packets occurs, which could lead to poor application |
88 | performance. Using a very large value, e.g. 50000, increases the | |
89 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
90 | from different IP datagrams, which could result in data corruption. |
91 | Default: 64 | |
92 | ||
1da177e4 LT |
93 | INET peer storage: |
94 | ||
95 | inet_peer_threshold - INTEGER | |
e18f5feb | 96 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
97 | entries will be thrown aggressively. This threshold also determines |
98 | entries' time-to-live and time intervals between garbage collection | |
99 | passes. More entries, less time-to-live, less GC interval. | |
100 | ||
101 | inet_peer_minttl - INTEGER | |
102 | Minimum time-to-live of entries. Should be enough to cover fragment | |
103 | time-to-live on the reassembling side. This minimum time-to-live is | |
104 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 105 | Measured in seconds. |
1da177e4 LT |
106 | |
107 | inet_peer_maxttl - INTEGER | |
108 | Maximum time-to-live of entries. Unused entries will expire after | |
109 | this period of time if there is no memory pressure on the pool (i.e. | |
110 | when the number of entries in the pool is very small). | |
77a538d5 | 111 | Measured in seconds. |
1da177e4 | 112 | |
e18f5feb | 113 | TCP variables: |
1da177e4 | 114 | |
ef56e622 SH |
115 | somaxconn - INTEGER |
116 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
117 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
118 | for TCP sockets. | |
119 | ||
9772efb9 | 120 | tcp_abc - INTEGER |
b3a8a40d SH |
121 | Controls Appropriate Byte Count (ABC) defined in RFC3465. |
122 | ABC is a way of increasing congestion window (cwnd) more slowly | |
123 | in response to partial acknowledgments. | |
124 | Possible values are: | |
125 | 0 increase cwnd once per acknowledgment (no ABC) | |
126 | 1 increase cwnd once per acknowledgment of full sized segment | |
127 | 2 allow increase cwnd by two if acknowledgment is | |
128 | of two segments to compensate for delayed acknowledgments. | |
129 | Default: 0 (off) | |
9772efb9 | 130 | |
ef56e622 SH |
131 | tcp_abort_on_overflow - BOOLEAN |
132 | If listening service is too slow to accept new connections, | |
133 | reset them. Default state is FALSE. It means that if overflow | |
134 | occurred due to a burst, connection will recover. Enable this | |
135 | option _only_ if you are really sure that listening daemon | |
136 | cannot be tuned to accept connections faster. Enabling this | |
137 | option can harm clients of your server. | |
1da177e4 | 138 | |
ef56e622 SH |
139 | tcp_adv_win_scale - INTEGER |
140 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
141 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
142 | if it is <= 0. | |
0147fc05 | 143 | Possible values are [-31, 31], inclusive. |
b49960a0 | 144 | Default: 1 |
1da177e4 | 145 | |
ef56e622 SH |
146 | tcp_allowed_congestion_control - STRING |
147 | Show/set the congestion control choices available to non-privileged | |
148 | processes. The list is a subset of those listed in | |
149 | tcp_available_congestion_control. | |
150 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 151 | |
ef56e622 SH |
152 | tcp_app_win - INTEGER |
153 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
154 | buffer. Value 0 is special, it means that nothing is reserved. | |
155 | Default: 31 | |
1da177e4 | 156 | |
ef56e622 SH |
157 | tcp_available_congestion_control - STRING |
158 | Shows the available congestion control choices that are registered. | |
159 | More congestion control algorithms may be available as modules, | |
160 | but not loaded. | |
1da177e4 | 161 | |
71599cd1 | 162 | tcp_base_mss - INTEGER |
4edc2f34 SH |
163 | The initial value of search_low to be used by the packetization layer |
164 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
165 | this is the initial MSS used by the connection. | |
71599cd1 | 166 | |
ef56e622 SH |
167 | tcp_congestion_control - STRING |
168 | Set the congestion control algorithm to be used for new | |
169 | connections. The algorithm "reno" is always available, but | |
170 | additional choices may be available based on kernel configuration. | |
171 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
172 | For passive connections, the listener congestion control choice |
173 | is inherited. | |
174 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
1da177e4 | 175 | |
519855c5 WAS |
176 | tcp_cookie_size - INTEGER |
177 | Default size of TCP Cookie Transactions (TCPCT) option, that may be | |
178 | overridden on a per socket basis by the TCPCT socket option. | |
179 | Values greater than the maximum (16) are interpreted as the maximum. | |
180 | Values greater than zero and less than the minimum (8) are interpreted | |
181 | as the minimum. Odd values are interpreted as the next even value. | |
182 | Default: 0 (off). | |
183 | ||
ef56e622 SH |
184 | tcp_dsack - BOOLEAN |
185 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 186 | |
eed530b6 YC |
187 | tcp_early_retrans - INTEGER |
188 | Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold | |
189 | for triggering fast retransmit when the amount of outstanding data is | |
190 | small and when no previously unsent data can be transmitted (such | |
191 | that limited transmit could be used). | |
192 | Possible values: | |
193 | 0 disables ER | |
194 | 1 enables ER | |
195 | 2 enables ER but delays fast recovery and fast retransmit | |
196 | by a fourth of RTT. This mitigates connection falsely | |
197 | recovers when network has a small degree of reordering | |
198 | (less than 3 packets). | |
199 | Default: 2 | |
200 | ||
34a6ef38 | 201 | tcp_ecn - INTEGER |
255cac91 IJ |
202 | Enable Explicit Congestion Notification (ECN) in TCP. ECN is only |
203 | used when both ends of the TCP flow support it. It is useful to | |
204 | avoid losses due to congestion (when the bottleneck router supports | |
205 | ECN). | |
206 | Possible values are: | |
207 | 0 disable ECN | |
208 | 1 ECN enabled | |
209 | 2 Only server-side ECN enabled. If the other end does | |
210 | not support ECN, behavior is like with ECN disabled. | |
211 | Default: 2 | |
ef56e622 SH |
212 | |
213 | tcp_fack - BOOLEAN | |
214 | Enable FACK congestion avoidance and fast retransmission. | |
215 | The value is not used, if tcp_sack is not enabled. | |
1da177e4 LT |
216 | |
217 | tcp_fin_timeout - INTEGER | |
218 | Time to hold socket in state FIN-WAIT-2, if it was closed | |
219 | by our side. Peer can be broken and never close its side, | |
220 | or even died unexpectedly. Default value is 60sec. | |
221 | Usual value used in 2.2 was 180 seconds, you may restore | |
222 | it, but remember that if your machine is even underloaded WEB server, | |
223 | you risk to overflow memory with kilotons of dead sockets, | |
224 | FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1, | |
225 | because they eat maximum 1.5K of memory, but they tend | |
226 | to live longer. Cf. tcp_max_orphans. | |
227 | ||
89808060 | 228 | tcp_frto - INTEGER |
cd99889c IJ |
229 | Enables Forward RTO-Recovery (F-RTO) defined in RFC4138. |
230 | F-RTO is an enhanced recovery algorithm for TCP retransmission | |
ef56e622 SH |
231 | timeouts. It is particularly beneficial in wireless environments |
232 | where packet loss is typically due to random radio interference | |
564262c1 | 233 | rather than intermediate router congestion. F-RTO is sender-side |
4edc2f34 SH |
234 | only modification. Therefore it does not require any support from |
235 | the peer. | |
236 | ||
cd99889c IJ |
237 | If set to 1, basic version is enabled. 2 enables SACK enhanced |
238 | F-RTO if flow uses SACK. The basic version can be used also when | |
564262c1 | 239 | SACK is in use though scenario(s) with it exists where F-RTO |
cd99889c IJ |
240 | interacts badly with the packet counting of the SACK enabled TCP |
241 | flow. | |
1da177e4 | 242 | |
89808060 IJ |
243 | tcp_frto_response - INTEGER |
244 | When F-RTO has detected that a TCP retransmission timeout was | |
245 | spurious (i.e, the timeout would have been avoided had TCP set a | |
246 | longer retransmission timeout), TCP has several options what to do | |
247 | next. Possible values are: | |
248 | 0 Rate halving based; a smooth and conservative response, | |
249 | results in halved cwnd and ssthresh after one RTT | |
250 | 1 Very conservative response; not recommended because even | |
251 | though being valid, it interacts poorly with the rest of | |
252 | Linux TCP, halves cwnd and ssthresh immediately | |
253 | 2 Aggressive response; undoes congestion control measures | |
254 | that are now known to be unnecessary (ignoring the | |
255 | possibility of a lost retransmission that would require | |
256 | TCP to be more cautious), cwnd and ssthresh are restored | |
257 | to the values prior timeout | |
258 | Default: 0 (rate halving based) | |
259 | ||
ef56e622 SH |
260 | tcp_keepalive_time - INTEGER |
261 | How often TCP sends out keepalive messages when keepalive is enabled. | |
262 | Default: 2hours. | |
1da177e4 | 263 | |
ef56e622 SH |
264 | tcp_keepalive_probes - INTEGER |
265 | How many keepalive probes TCP sends out, until it decides that the | |
266 | connection is broken. Default value: 9. | |
267 | ||
268 | tcp_keepalive_intvl - INTEGER | |
269 | How frequently the probes are send out. Multiplied by | |
270 | tcp_keepalive_probes it is time to kill not responding connection, | |
271 | after probes started. Default value: 75sec i.e. connection | |
272 | will be aborted after ~11 minutes of retries. | |
273 | ||
274 | tcp_low_latency - BOOLEAN | |
275 | If set, the TCP stack makes decisions that prefer lower | |
276 | latency as opposed to higher throughput. By default, this | |
277 | option is not set meaning that higher throughput is preferred. | |
278 | An example of an application where this default should be | |
279 | changed would be a Beowulf compute cluster. | |
280 | Default: 0 | |
1da177e4 LT |
281 | |
282 | tcp_max_orphans - INTEGER | |
283 | Maximal number of TCP sockets not attached to any user file handle, | |
284 | held by system. If this number is exceeded orphaned connections are | |
285 | reset immediately and warning is printed. This limit exists | |
286 | only to prevent simple DoS attacks, you _must_ not rely on this | |
287 | or lower the limit artificially, but rather increase it | |
288 | (probably, after increasing installed memory), | |
289 | if network conditions require more than default value, | |
290 | and tune network services to linger and kill such states | |
291 | more aggressively. Let me to remind again: each orphan eats | |
292 | up to ~64K of unswappable memory. | |
293 | ||
81146ec1 IJ |
294 | tcp_max_ssthresh - INTEGER |
295 | Limited Slow-Start for TCP with large congestion windows (cwnd) defined in | |
296 | RFC3742. Limited slow-start is a mechanism to limit growth of the cwnd | |
297 | on the region where cwnd is larger than tcp_max_ssthresh. TCP increases cwnd | |
298 | by at most tcp_max_ssthresh segments, and by at least tcp_max_ssthresh/2 | |
299 | segments per RTT when the cwnd is above tcp_max_ssthresh. | |
300 | If TCP connection increased cwnd to thousands (or tens of thousands) segments, | |
301 | and thousands of packets were being dropped during slow-start, you can set | |
302 | tcp_max_ssthresh to improve performance for new TCP connection. | |
303 | Default: 0 (off) | |
304 | ||
1da177e4 | 305 | tcp_max_syn_backlog - INTEGER |
99b53bdd PP |
306 | Maximal number of remembered connection requests, which have not |
307 | received an acknowledgment from connecting client. | |
308 | The minimal value is 128 for low memory machines, and it will | |
309 | increase in proportion to the memory of machine. | |
310 | If server suffers from overload, try increasing this number. | |
1da177e4 | 311 | |
ef56e622 SH |
312 | tcp_max_tw_buckets - INTEGER |
313 | Maximal number of timewait sockets held by system simultaneously. | |
314 | If this number is exceeded time-wait socket is immediately destroyed | |
315 | and warning is printed. This limit exists only to prevent | |
316 | simple DoS attacks, you _must_ not lower the limit artificially, | |
317 | but rather increase it (probably, after increasing installed memory), | |
318 | if network conditions require more than default value. | |
1da177e4 | 319 | |
ef56e622 SH |
320 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
321 | min: below this number of pages TCP is not bothered about its | |
322 | memory appetite. | |
1da177e4 | 323 | |
ef56e622 SH |
324 | pressure: when amount of memory allocated by TCP exceeds this number |
325 | of pages, TCP moderates its memory consumption and enters memory | |
326 | pressure mode, which is exited when memory consumption falls | |
327 | under "min". | |
1da177e4 | 328 | |
ef56e622 | 329 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 330 | |
ef56e622 SH |
331 | Defaults are calculated at boot time from amount of available |
332 | memory. | |
1da177e4 | 333 | |
71599cd1 | 334 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 335 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
336 | automatically size the buffer (no greater than tcp_rmem[2]) to |
337 | match the size required by the path for full throughput. Enabled by | |
338 | default. | |
339 | ||
340 | tcp_mtu_probing - INTEGER | |
341 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
342 | values: | |
343 | 0 - Disabled | |
344 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
345 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
346 | ||
347 | tcp_no_metrics_save - BOOLEAN | |
348 | By default, TCP saves various connection metrics in the route cache | |
349 | when the connection closes, so that connections established in the | |
350 | near future can use these to set initial conditions. Usually, this | |
351 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 352 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
353 | connections. |
354 | ||
ef56e622 | 355 | tcp_orphan_retries - INTEGER |
5d789229 DL |
356 | This value influences the timeout of a locally closed TCP connection, |
357 | when RTO retransmissions remain unacknowledged. | |
358 | See tcp_retries2 for more details. | |
359 | ||
06b8fc5d | 360 | The default value is 8. |
5d789229 | 361 | If your machine is a loaded WEB server, |
ef56e622 SH |
362 | you should think about lowering this value, such sockets |
363 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
364 | |
365 | tcp_reordering - INTEGER | |
366 | Maximal reordering of packets in a TCP stream. | |
e18f5feb | 367 | Default: 3 |
1da177e4 LT |
368 | |
369 | tcp_retrans_collapse - BOOLEAN | |
370 | Bug-to-bug compatibility with some broken printers. | |
371 | On retransmit try to send bigger packets to work around bugs in | |
372 | certain TCP stacks. | |
373 | ||
ef56e622 | 374 | tcp_retries1 - INTEGER |
5d789229 DL |
375 | This value influences the time, after which TCP decides, that |
376 | something is wrong due to unacknowledged RTO retransmissions, | |
377 | and reports this suspicion to the network layer. | |
378 | See tcp_retries2 for more details. | |
379 | ||
380 | RFC 1122 recommends at least 3 retransmissions, which is the | |
381 | default. | |
1da177e4 | 382 | |
ef56e622 | 383 | tcp_retries2 - INTEGER |
5d789229 DL |
384 | This value influences the timeout of an alive TCP connection, |
385 | when RTO retransmissions remain unacknowledged. | |
386 | Given a value of N, a hypothetical TCP connection following | |
387 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
388 | retransmit N times before killing the connection at the (N+1)th RTO. | |
389 | ||
390 | The default value of 15 yields a hypothetical timeout of 924.6 | |
391 | seconds and is a lower bound for the effective timeout. | |
392 | TCP will effectively time out at the first RTO which exceeds the | |
393 | hypothetical timeout. | |
394 | ||
395 | RFC 1122 recommends at least 100 seconds for the timeout, | |
396 | which corresponds to a value of at least 8. | |
1da177e4 | 397 | |
ef56e622 SH |
398 | tcp_rfc1337 - BOOLEAN |
399 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
400 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
401 | assassination. | |
402 | Default: 0 | |
1da177e4 LT |
403 | |
404 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
405 | min: Minimal size of receive buffer used by TCP sockets. | |
406 | It is guaranteed to each TCP socket, even under moderate memory | |
407 | pressure. | |
6539fefd | 408 | Default: 1 page |
1da177e4 | 409 | |
53025f5e | 410 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
411 | This value overrides net.core.rmem_default used by other protocols. |
412 | Default: 87380 bytes. This value results in window of 65535 with | |
413 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
414 | less for default tcp_app_win. See below about these variables. | |
415 | ||
416 | max: maximal size of receive buffer allowed for automatically | |
417 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
418 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
419 | automatic tuning of that socket's receive buffer size, in which | |
420 | case this value is ignored. | |
b49960a0 | 421 | Default: between 87380B and 6MB, depending on RAM size. |
1da177e4 | 422 | |
ef56e622 SH |
423 | tcp_sack - BOOLEAN |
424 | Enable select acknowledgments (SACKS). | |
1da177e4 | 425 | |
ef56e622 SH |
426 | tcp_slow_start_after_idle - BOOLEAN |
427 | If set, provide RFC2861 behavior and time out the congestion | |
428 | window after an idle period. An idle period is defined at | |
429 | the current RTO. If unset, the congestion window will not | |
430 | be timed out after an idle period. | |
431 | Default: 1 | |
1da177e4 | 432 | |
ef56e622 | 433 | tcp_stdurg - BOOLEAN |
4edc2f34 | 434 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
435 | Most hosts use the older BSD interpretation, so if you turn this on |
436 | Linux might not communicate correctly with them. | |
437 | Default: FALSE | |
1da177e4 | 438 | |
ef56e622 SH |
439 | tcp_synack_retries - INTEGER |
440 | Number of times SYNACKs for a passive TCP connection attempt will | |
441 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
442 | is 5, which corresponds to 31seconds till the last retransmission |
443 | with the current initial RTO of 1second. With this the final timeout | |
444 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 445 | |
ef56e622 SH |
446 | tcp_syncookies - BOOLEAN |
447 | Only valid when the kernel was compiled with CONFIG_SYNCOOKIES | |
448 | Send out syncookies when the syn backlog queue of a socket | |
4edc2f34 | 449 | overflows. This is to prevent against the common 'SYN flood attack' |
ef56e622 | 450 | Default: FALSE |
1da177e4 | 451 | |
ef56e622 SH |
452 | Note, that syncookies is fallback facility. |
453 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 454 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
455 | in your logs, but investigation shows that they occur |
456 | because of overload with legal connections, you should tune | |
457 | another parameters until this warning disappear. | |
458 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 459 | |
ef56e622 SH |
460 | syncookies seriously violate TCP protocol, do not allow |
461 | to use TCP extensions, can result in serious degradation | |
462 | of some services (f.e. SMTP relaying), visible not by you, | |
463 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 464 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 465 | is seriously misconfigured. |
1da177e4 | 466 | |
cf60af03 YC |
467 | tcp_fastopen - INTEGER |
468 | Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data | |
469 | in the opening SYN packet. To use this feature, the client application | |
10467163 JC |
470 | must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than |
471 | connect() to perform a TCP handshake automatically. | |
472 | ||
473 | The values (bitmap) are | |
474 | 1: Enables sending data in the opening SYN on the client. | |
475 | 2: Enables TCP Fast Open on the server side, i.e., allowing data in | |
476 | a SYN packet to be accepted and passed to the application before | |
477 | 3-way hand shake finishes. | |
478 | 4: Send data in the opening SYN regardless of cookie availability and | |
479 | without a cookie option. | |
480 | 0x100: Accept SYN data w/o validating the cookie. | |
481 | 0x200: Accept data-in-SYN w/o any cookie option present. | |
482 | 0x400/0x800: Enable Fast Open on all listeners regardless of the | |
483 | TCP_FASTOPEN socket option. The two different flags designate two | |
484 | different ways of setting max_qlen without the TCP_FASTOPEN socket | |
485 | option. | |
cf60af03 YC |
486 | |
487 | Default: 0 | |
488 | ||
10467163 JC |
489 | Note that the client & server side Fast Open flags (1 and 2 |
490 | respectively) must be also enabled before the rest of flags can take | |
491 | effect. | |
492 | ||
493 | See include/net/tcp.h and the code for more details. | |
494 | ||
ef56e622 SH |
495 | tcp_syn_retries - INTEGER |
496 | Number of times initial SYNs for an active TCP connection attempt | |
497 | will be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
498 | is 6, which corresponds to 63seconds till the last restransmission |
499 | with the current initial RTO of 1second. With this the final timeout | |
500 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 SH |
501 | |
502 | tcp_timestamps - BOOLEAN | |
503 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 504 | |
1da177e4 | 505 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
506 | This allows control over what percentage of the congestion window |
507 | can be consumed by a single TSO frame. | |
508 | The setting of this parameter is a choice between burstiness and | |
509 | building larger TSO frames. | |
510 | Default: 3 | |
1da177e4 | 511 | |
ef56e622 SH |
512 | tcp_tw_recycle - BOOLEAN |
513 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
514 | It should not be changed without advice/request of technical | |
515 | experts. | |
1da177e4 | 516 | |
ef56e622 SH |
517 | tcp_tw_reuse - BOOLEAN |
518 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
519 | safe from protocol viewpoint. Default value is 0. | |
520 | It should not be changed without advice/request of technical | |
521 | experts. | |
ce7bc3bf | 522 | |
ef56e622 SH |
523 | tcp_window_scaling - BOOLEAN |
524 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 525 | |
ef56e622 | 526 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 527 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 528 | Each TCP socket has rights to use it due to fact of its birth. |
6539fefd | 529 | Default: 1 page |
9d7bcfc6 | 530 | |
53025f5e BF |
531 | default: initial size of send buffer used by TCP sockets. This |
532 | value overrides net.core.wmem_default used by other protocols. | |
533 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
534 | Default: 16K |
535 | ||
53025f5e BF |
536 | max: Maximal amount of memory allowed for automatically tuned |
537 | send buffers for TCP sockets. This value does not override | |
538 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
539 | automatic tuning of that socket's send buffer size, in which case | |
540 | this value is ignored. | |
541 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 542 | |
15d99e02 RJ |
543 | tcp_workaround_signed_windows - BOOLEAN |
544 | If set, assume no receipt of a window scaling option means the | |
545 | remote TCP is broken and treats the window as a signed quantity. | |
546 | If unset, assume the remote TCP is not broken even if we do | |
547 | not receive a window scaling option from them. | |
548 | Default: 0 | |
549 | ||
72d0b7a8 CL |
550 | tcp_dma_copybreak - INTEGER |
551 | Lower limit, in bytes, of the size of socket reads that will be | |
552 | offloaded to a DMA copy engine, if one is present in the system | |
553 | and CONFIG_NET_DMA is enabled. | |
554 | Default: 4096 | |
555 | ||
36e31b0a AP |
556 | tcp_thin_linear_timeouts - BOOLEAN |
557 | Enable dynamic triggering of linear timeouts for thin streams. | |
558 | If set, a check is performed upon retransmission by timeout to | |
559 | determine if the stream is thin (less than 4 packets in flight). | |
560 | As long as the stream is found to be thin, up to 6 linear | |
561 | timeouts may be performed before exponential backoff mode is | |
562 | initiated. This improves retransmission latency for | |
563 | non-aggressive thin streams, often found to be time-dependent. | |
564 | For more information on thin streams, see | |
565 | Documentation/networking/tcp-thin.txt | |
566 | Default: 0 | |
567 | ||
7e380175 AP |
568 | tcp_thin_dupack - BOOLEAN |
569 | Enable dynamic triggering of retransmissions after one dupACK | |
570 | for thin streams. If set, a check is performed upon reception | |
571 | of a dupACK to determine if the stream is thin (less than 4 | |
572 | packets in flight). As long as the stream is found to be thin, | |
573 | data is retransmitted on the first received dupACK. This | |
574 | improves retransmission latency for non-aggressive thin | |
575 | streams, often found to be time-dependent. | |
576 | For more information on thin streams, see | |
577 | Documentation/networking/tcp-thin.txt | |
578 | Default: 0 | |
579 | ||
46d3ceab ED |
580 | tcp_limit_output_bytes - INTEGER |
581 | Controls TCP Small Queue limit per tcp socket. | |
582 | TCP bulk sender tends to increase packets in flight until it | |
583 | gets losses notifications. With SNDBUF autotuning, this can | |
584 | result in a large amount of packets queued in qdisc/device | |
585 | on the local machine, hurting latency of other flows, for | |
586 | typical pfifo_fast qdiscs. | |
587 | tcp_limit_output_bytes limits the number of bytes on qdisc | |
588 | or device to reduce artificial RTT/cwnd and reduce bufferbloat. | |
589 | Note: For GSO/TSO enabled flows, we try to have at least two | |
590 | packets in flight. Reducing tcp_limit_output_bytes might also | |
591 | reduce the size of individual GSO packet (64KB being the max) | |
592 | Default: 131072 | |
593 | ||
282f23c6 ED |
594 | tcp_challenge_ack_limit - INTEGER |
595 | Limits number of Challenge ACK sent per second, as recommended | |
596 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
597 | Default: 100 | |
598 | ||
95766fff HA |
599 | UDP variables: |
600 | ||
601 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
602 | Number of pages allowed for queueing by all UDP sockets. | |
603 | ||
604 | min: Below this number of pages UDP is not bothered about its | |
605 | memory appetite. When amount of memory allocated by UDP exceeds | |
606 | this number, UDP starts to moderate memory usage. | |
607 | ||
608 | pressure: This value was introduced to follow format of tcp_mem. | |
609 | ||
610 | max: Number of pages allowed for queueing by all UDP sockets. | |
611 | ||
612 | Default is calculated at boot time from amount of available memory. | |
613 | ||
614 | udp_rmem_min - INTEGER | |
615 | Minimal size of receive buffer used by UDP sockets in moderation. | |
616 | Each UDP socket is able to use the size for receiving data, even if | |
617 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 618 | Default: 1 page |
95766fff HA |
619 | |
620 | udp_wmem_min - INTEGER | |
621 | Minimal size of send buffer used by UDP sockets in moderation. | |
622 | Each UDP socket is able to use the size for sending data, even if | |
623 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 624 | Default: 1 page |
95766fff | 625 | |
8802f616 PM |
626 | CIPSOv4 Variables: |
627 | ||
628 | cipso_cache_enable - BOOLEAN | |
629 | If set, enable additions to and lookups from the CIPSO label mapping | |
630 | cache. If unset, additions are ignored and lookups always result in a | |
631 | miss. However, regardless of the setting the cache is still | |
632 | invalidated when required when means you can safely toggle this on and | |
633 | off and the cache will always be "safe". | |
634 | Default: 1 | |
635 | ||
636 | cipso_cache_bucket_size - INTEGER | |
637 | The CIPSO label cache consists of a fixed size hash table with each | |
638 | hash bucket containing a number of cache entries. This variable limits | |
639 | the number of entries in each hash bucket; the larger the value the | |
640 | more CIPSO label mappings that can be cached. When the number of | |
641 | entries in a given hash bucket reaches this limit adding new entries | |
642 | causes the oldest entry in the bucket to be removed to make room. | |
643 | Default: 10 | |
644 | ||
645 | cipso_rbm_optfmt - BOOLEAN | |
646 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
647 | the CIPSO draft specification (see Documentation/netlabel for details). | |
648 | This means that when set the CIPSO tag will be padded with empty | |
649 | categories in order to make the packet data 32-bit aligned. | |
650 | Default: 0 | |
651 | ||
652 | cipso_rbm_structvalid - BOOLEAN | |
653 | If set, do a very strict check of the CIPSO option when | |
654 | ip_options_compile() is called. If unset, relax the checks done during | |
655 | ip_options_compile(). Either way is "safe" as errors are caught else | |
656 | where in the CIPSO processing code but setting this to 0 (False) should | |
657 | result in less work (i.e. it should be faster) but could cause problems | |
658 | with other implementations that require strict checking. | |
659 | Default: 0 | |
660 | ||
1da177e4 LT |
661 | IP Variables: |
662 | ||
663 | ip_local_port_range - 2 INTEGERS | |
664 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 665 | choose the local port. The first number is the first, the |
5d6bd861 FLVC |
666 | second the last local port number. The default values are |
667 | 32768 and 61000 respectively. | |
1da177e4 | 668 | |
e3826f1e AW |
669 | ip_local_reserved_ports - list of comma separated ranges |
670 | Specify the ports which are reserved for known third-party | |
671 | applications. These ports will not be used by automatic port | |
672 | assignments (e.g. when calling connect() or bind() with port | |
673 | number 0). Explicit port allocation behavior is unchanged. | |
674 | ||
675 | The format used for both input and output is a comma separated | |
676 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
677 | 10). Writing to the file will clear all previously reserved | |
678 | ports and update the current list with the one given in the | |
679 | input. | |
680 | ||
681 | Note that ip_local_port_range and ip_local_reserved_ports | |
682 | settings are independent and both are considered by the kernel | |
683 | when determining which ports are available for automatic port | |
684 | assignments. | |
685 | ||
686 | You can reserve ports which are not in the current | |
687 | ip_local_port_range, e.g.: | |
688 | ||
689 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
690 | 32000 61000 | |
691 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
692 | 8080,9148 | |
693 | ||
694 | although this is redundant. However such a setting is useful | |
695 | if later the port range is changed to a value that will | |
696 | include the reserved ports. | |
697 | ||
698 | Default: Empty | |
699 | ||
1da177e4 LT |
700 | ip_nonlocal_bind - BOOLEAN |
701 | If set, allows processes to bind() to non-local IP addresses, | |
702 | which can be quite useful - but may break some applications. | |
703 | Default: 0 | |
704 | ||
705 | ip_dynaddr - BOOLEAN | |
706 | If set non-zero, enables support for dynamic addresses. | |
707 | If set to a non-zero value larger than 1, a kernel log | |
708 | message will be printed when dynamic address rewriting | |
709 | occurs. | |
710 | Default: 0 | |
711 | ||
712 | icmp_echo_ignore_all - BOOLEAN | |
7ce31246 DM |
713 | If set non-zero, then the kernel will ignore all ICMP ECHO |
714 | requests sent to it. | |
715 | Default: 0 | |
716 | ||
1da177e4 | 717 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
718 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
719 | TIMESTAMP requests sent to it via broadcast/multicast. | |
720 | Default: 1 | |
1da177e4 LT |
721 | |
722 | icmp_ratelimit - INTEGER | |
723 | Limit the maximal rates for sending ICMP packets whose type matches | |
724 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
725 | 0 to disable any limiting, |
726 | otherwise the minimal space between responses in milliseconds. | |
727 | Default: 1000 | |
1da177e4 LT |
728 | |
729 | icmp_ratemask - INTEGER | |
730 | Mask made of ICMP types for which rates are being limited. | |
731 | Significant bits: IHGFEDCBA9876543210 | |
732 | Default mask: 0000001100000011000 (6168) | |
733 | ||
734 | Bit definitions (see include/linux/icmp.h): | |
735 | 0 Echo Reply | |
736 | 3 Destination Unreachable * | |
737 | 4 Source Quench * | |
738 | 5 Redirect | |
739 | 8 Echo Request | |
740 | B Time Exceeded * | |
741 | C Parameter Problem * | |
742 | D Timestamp Request | |
743 | E Timestamp Reply | |
744 | F Info Request | |
745 | G Info Reply | |
746 | H Address Mask Request | |
747 | I Address Mask Reply | |
748 | ||
749 | * These are rate limited by default (see default mask above) | |
750 | ||
751 | icmp_ignore_bogus_error_responses - BOOLEAN | |
752 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
753 | frames. Such violations are normally logged via a kernel warning. | |
754 | If this is set to TRUE, the kernel will not give such warnings, which | |
755 | will avoid log file clutter. | |
756 | Default: FALSE | |
757 | ||
95f7daf1 H |
758 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
759 | ||
760 | If zero, icmp error messages are sent with the primary address of | |
761 | the exiting interface. | |
e18f5feb | 762 | |
95f7daf1 H |
763 | If non-zero, the message will be sent with the primary address of |
764 | the interface that received the packet that caused the icmp error. | |
765 | This is the behaviour network many administrators will expect from | |
766 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 767 | much easier. |
95f7daf1 H |
768 | |
769 | Note that if no primary address exists for the interface selected, | |
770 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 771 | has one will be used regardless of this setting. |
95f7daf1 H |
772 | |
773 | Default: 0 | |
774 | ||
1da177e4 LT |
775 | igmp_max_memberships - INTEGER |
776 | Change the maximum number of multicast groups we can subscribe to. | |
777 | Default: 20 | |
778 | ||
d67ef35f JE |
779 | Theoretical maximum value is bounded by having to send a membership |
780 | report in a single datagram (i.e. the report can't span multiple | |
781 | datagrams, or risk confusing the switch and leaving groups you don't | |
782 | intend to). | |
1da177e4 | 783 | |
d67ef35f JE |
784 | The number of supported groups 'M' is bounded by the number of group |
785 | report entries you can fit into a single datagram of 65535 bytes. | |
786 | ||
787 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
788 | ||
789 | Group records are variable length, with a minimum of 12 bytes. | |
790 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
791 | ||
792 | (65536-24) / 12 = 5459 | |
793 | ||
794 | The value 5459 assumes no IP header options, so in practice | |
795 | this number may be lower. | |
796 | ||
797 | conf/interface/* changes special settings per interface (where | |
798 | "interface" is the name of your network interface) | |
799 | ||
800 | conf/all/* is special, changes the settings for all interfaces | |
1da177e4 LT |
801 | |
802 | log_martians - BOOLEAN | |
803 | Log packets with impossible addresses to kernel log. | |
804 | log_martians for the interface will be enabled if at least one of | |
805 | conf/{all,interface}/log_martians is set to TRUE, | |
806 | it will be disabled otherwise | |
807 | ||
808 | accept_redirects - BOOLEAN | |
809 | Accept ICMP redirect messages. | |
810 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
811 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
812 | forwarding for the interface is enabled | |
1da177e4 | 813 | or |
e18f5feb JDB |
814 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
815 | case forwarding for the interface is disabled | |
1da177e4 LT |
816 | accept_redirects for the interface will be disabled otherwise |
817 | default TRUE (host) | |
818 | FALSE (router) | |
819 | ||
820 | forwarding - BOOLEAN | |
821 | Enable IP forwarding on this interface. | |
822 | ||
823 | mc_forwarding - BOOLEAN | |
824 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
825 | and a multicast routing daemon is required. | |
e18f5feb JDB |
826 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
827 | routing for the interface | |
1da177e4 LT |
828 | |
829 | medium_id - INTEGER | |
830 | Integer value used to differentiate the devices by the medium they | |
831 | are attached to. Two devices can have different id values when | |
832 | the broadcast packets are received only on one of them. | |
833 | The default value 0 means that the device is the only interface | |
834 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 835 | |
1da177e4 LT |
836 | Currently, it is used to change the proxy_arp behavior: |
837 | the proxy_arp feature is enabled for packets forwarded between | |
838 | two devices attached to different media. | |
839 | ||
840 | proxy_arp - BOOLEAN | |
841 | Do proxy arp. | |
842 | proxy_arp for the interface will be enabled if at least one of | |
843 | conf/{all,interface}/proxy_arp is set to TRUE, | |
844 | it will be disabled otherwise | |
845 | ||
65324144 JDB |
846 | proxy_arp_pvlan - BOOLEAN |
847 | Private VLAN proxy arp. | |
848 | Basically allow proxy arp replies back to the same interface | |
849 | (from which the ARP request/solicitation was received). | |
850 | ||
851 | This is done to support (ethernet) switch features, like RFC | |
852 | 3069, where the individual ports are NOT allowed to | |
853 | communicate with each other, but they are allowed to talk to | |
854 | the upstream router. As described in RFC 3069, it is possible | |
855 | to allow these hosts to communicate through the upstream | |
856 | router by proxy_arp'ing. Don't need to be used together with | |
857 | proxy_arp. | |
858 | ||
859 | This technology is known by different names: | |
860 | In RFC 3069 it is called VLAN Aggregation. | |
861 | Cisco and Allied Telesyn call it Private VLAN. | |
862 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
863 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
864 | ||
1da177e4 LT |
865 | shared_media - BOOLEAN |
866 | Send(router) or accept(host) RFC1620 shared media redirects. | |
867 | Overrides ip_secure_redirects. | |
868 | shared_media for the interface will be enabled if at least one of | |
869 | conf/{all,interface}/shared_media is set to TRUE, | |
870 | it will be disabled otherwise | |
871 | default TRUE | |
872 | ||
873 | secure_redirects - BOOLEAN | |
874 | Accept ICMP redirect messages only for gateways, | |
875 | listed in default gateway list. | |
876 | secure_redirects for the interface will be enabled if at least one of | |
877 | conf/{all,interface}/secure_redirects is set to TRUE, | |
878 | it will be disabled otherwise | |
879 | default TRUE | |
880 | ||
881 | send_redirects - BOOLEAN | |
882 | Send redirects, if router. | |
883 | send_redirects for the interface will be enabled if at least one of | |
884 | conf/{all,interface}/send_redirects is set to TRUE, | |
885 | it will be disabled otherwise | |
886 | Default: TRUE | |
887 | ||
888 | bootp_relay - BOOLEAN | |
889 | Accept packets with source address 0.b.c.d destined | |
890 | not to this host as local ones. It is supposed, that | |
891 | BOOTP relay daemon will catch and forward such packets. | |
892 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
893 | for the interface | |
894 | default FALSE | |
895 | Not Implemented Yet. | |
896 | ||
897 | accept_source_route - BOOLEAN | |
898 | Accept packets with SRR option. | |
899 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
900 | with SRR option on the interface | |
901 | default TRUE (router) | |
902 | FALSE (host) | |
903 | ||
8153a10c | 904 | accept_local - BOOLEAN |
c801e3cc DM |
905 | Accept packets with local source addresses. In combination |
906 | with suitable routing, this can be used to direct packets | |
907 | between two local interfaces over the wire and have them | |
908 | accepted properly. | |
909 | ||
910 | rp_filter must be set to a non-zero value in order for | |
911 | accept_local to have an effect. | |
912 | ||
8153a10c PM |
913 | default FALSE |
914 | ||
d0daebc3 TG |
915 | route_localnet - BOOLEAN |
916 | Do not consider loopback addresses as martian source or destination | |
917 | while routing. This enables the use of 127/8 for local routing purposes. | |
918 | default FALSE | |
919 | ||
c1cf8422 | 920 | rp_filter - INTEGER |
1da177e4 | 921 | 0 - No source validation. |
c1cf8422 SH |
922 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
923 | Each incoming packet is tested against the FIB and if the interface | |
924 | is not the best reverse path the packet check will fail. | |
925 | By default failed packets are discarded. | |
926 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
927 | Each incoming packet's source address is also tested against the FIB | |
928 | and if the source address is not reachable via any interface | |
929 | the packet check will fail. | |
930 | ||
e18f5feb | 931 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 932 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 933 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 934 | |
1f5865e7 SW |
935 | The max value from conf/{all,interface}/rp_filter is used |
936 | when doing source validation on the {interface}. | |
1da177e4 LT |
937 | |
938 | Default value is 0. Note that some distributions enable it | |
939 | in startup scripts. | |
940 | ||
941 | arp_filter - BOOLEAN | |
942 | 1 - Allows you to have multiple network interfaces on the same | |
943 | subnet, and have the ARPs for each interface be answered | |
944 | based on whether or not the kernel would route a packet from | |
945 | the ARP'd IP out that interface (therefore you must use source | |
946 | based routing for this to work). In other words it allows control | |
947 | of which cards (usually 1) will respond to an arp request. | |
948 | ||
949 | 0 - (default) The kernel can respond to arp requests with addresses | |
950 | from other interfaces. This may seem wrong but it usually makes | |
951 | sense, because it increases the chance of successful communication. | |
952 | IP addresses are owned by the complete host on Linux, not by | |
953 | particular interfaces. Only for more complex setups like load- | |
954 | balancing, does this behaviour cause problems. | |
955 | ||
956 | arp_filter for the interface will be enabled if at least one of | |
957 | conf/{all,interface}/arp_filter is set to TRUE, | |
958 | it will be disabled otherwise | |
959 | ||
960 | arp_announce - INTEGER | |
961 | Define different restriction levels for announcing the local | |
962 | source IP address from IP packets in ARP requests sent on | |
963 | interface: | |
964 | 0 - (default) Use any local address, configured on any interface | |
965 | 1 - Try to avoid local addresses that are not in the target's | |
966 | subnet for this interface. This mode is useful when target | |
967 | hosts reachable via this interface require the source IP | |
968 | address in ARP requests to be part of their logical network | |
969 | configured on the receiving interface. When we generate the | |
970 | request we will check all our subnets that include the | |
971 | target IP and will preserve the source address if it is from | |
972 | such subnet. If there is no such subnet we select source | |
973 | address according to the rules for level 2. | |
974 | 2 - Always use the best local address for this target. | |
975 | In this mode we ignore the source address in the IP packet | |
976 | and try to select local address that we prefer for talks with | |
977 | the target host. Such local address is selected by looking | |
978 | for primary IP addresses on all our subnets on the outgoing | |
979 | interface that include the target IP address. If no suitable | |
980 | local address is found we select the first local address | |
981 | we have on the outgoing interface or on all other interfaces, | |
982 | with the hope we will receive reply for our request and | |
983 | even sometimes no matter the source IP address we announce. | |
984 | ||
985 | The max value from conf/{all,interface}/arp_announce is used. | |
986 | ||
987 | Increasing the restriction level gives more chance for | |
988 | receiving answer from the resolved target while decreasing | |
989 | the level announces more valid sender's information. | |
990 | ||
991 | arp_ignore - INTEGER | |
992 | Define different modes for sending replies in response to | |
993 | received ARP requests that resolve local target IP addresses: | |
994 | 0 - (default): reply for any local target IP address, configured | |
995 | on any interface | |
996 | 1 - reply only if the target IP address is local address | |
997 | configured on the incoming interface | |
998 | 2 - reply only if the target IP address is local address | |
999 | configured on the incoming interface and both with the | |
1000 | sender's IP address are part from same subnet on this interface | |
1001 | 3 - do not reply for local addresses configured with scope host, | |
1002 | only resolutions for global and link addresses are replied | |
1003 | 4-7 - reserved | |
1004 | 8 - do not reply for all local addresses | |
1005 | ||
1006 | The max value from conf/{all,interface}/arp_ignore is used | |
1007 | when ARP request is received on the {interface} | |
1008 | ||
eefef1cf SH |
1009 | arp_notify - BOOLEAN |
1010 | Define mode for notification of address and device changes. | |
1011 | 0 - (default): do nothing | |
3f8dc236 | 1012 | 1 - Generate gratuitous arp requests when device is brought up |
eefef1cf SH |
1013 | or hardware address changes. |
1014 | ||
c1b1bce8 | 1015 | arp_accept - BOOLEAN |
6d955180 OP |
1016 | Define behavior for gratuitous ARP frames who's IP is not |
1017 | already present in the ARP table: | |
1018 | 0 - don't create new entries in the ARP table | |
1019 | 1 - create new entries in the ARP table | |
1020 | ||
1021 | Both replies and requests type gratuitous arp will trigger the | |
1022 | ARP table to be updated, if this setting is on. | |
1023 | ||
1024 | If the ARP table already contains the IP address of the | |
1025 | gratuitous arp frame, the arp table will be updated regardless | |
1026 | if this setting is on or off. | |
1027 | ||
c1b1bce8 | 1028 | |
1da177e4 LT |
1029 | app_solicit - INTEGER |
1030 | The maximum number of probes to send to the user space ARP daemon | |
1031 | via netlink before dropping back to multicast probes (see | |
1032 | mcast_solicit). Defaults to 0. | |
1033 | ||
1034 | disable_policy - BOOLEAN | |
1035 | Disable IPSEC policy (SPD) for this interface | |
1036 | ||
1037 | disable_xfrm - BOOLEAN | |
1038 | Disable IPSEC encryption on this interface, whatever the policy | |
1039 | ||
1040 | ||
1041 | ||
1042 | tag - INTEGER | |
1043 | Allows you to write a number, which can be used as required. | |
1044 | Default value is 0. | |
1045 | ||
1da177e4 LT |
1046 | Alexey Kuznetsov. |
1047 | kuznet@ms2.inr.ac.ru | |
1048 | ||
1049 | Updated by: | |
1050 | Andi Kleen | |
1051 | ak@muc.de | |
1052 | Nicolas Delon | |
1053 | delon.nicolas@wanadoo.fr | |
1054 | ||
1055 | ||
1056 | ||
1057 | ||
1058 | /proc/sys/net/ipv6/* Variables: | |
1059 | ||
1060 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1061 | apply to IPv6 [XXX?]. | |
1062 | ||
1063 | bindv6only - BOOLEAN | |
1064 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1065 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
1066 | only. |
1067 | TRUE: disable IPv4-mapped address feature | |
1068 | FALSE: enable IPv4-mapped address feature | |
1069 | ||
d5c073ca | 1070 | Default: FALSE (as specified in RFC3493) |
1da177e4 LT |
1071 | |
1072 | IPv6 Fragmentation: | |
1073 | ||
1074 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1075 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1076 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1077 | the fragment handler will toss packets until ip6frag_low_thresh | |
1078 | is reached. | |
e18f5feb | 1079 | |
1da177e4 | 1080 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1081 | See ip6frag_high_thresh |
1da177e4 LT |
1082 | |
1083 | ip6frag_time - INTEGER | |
1084 | Time in seconds to keep an IPv6 fragment in memory. | |
1085 | ||
1086 | ip6frag_secret_interval - INTEGER | |
e18f5feb | 1087 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
1088 | for the hash secret) for IPv6 fragments. |
1089 | Default: 600 | |
1090 | ||
1091 | conf/default/*: | |
1092 | Change the interface-specific default settings. | |
1093 | ||
1094 | ||
1095 | conf/all/*: | |
e18f5feb | 1096 | Change all the interface-specific settings. |
1da177e4 LT |
1097 | |
1098 | [XXX: Other special features than forwarding?] | |
1099 | ||
1100 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 1101 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 1102 | |
e18f5feb | 1103 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
1104 | to control which interfaces may forward packets and which not. |
1105 | ||
e18f5feb | 1106 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
1107 | 'forwarding' to the specified value. See below for details. |
1108 | ||
1109 | This referred to as global forwarding. | |
1110 | ||
fbea49e1 YH |
1111 | proxy_ndp - BOOLEAN |
1112 | Do proxy ndp. | |
1113 | ||
1da177e4 LT |
1114 | conf/interface/*: |
1115 | Change special settings per interface. | |
1116 | ||
e18f5feb | 1117 | The functional behaviour for certain settings is different |
1da177e4 LT |
1118 | depending on whether local forwarding is enabled or not. |
1119 | ||
605b91c8 | 1120 | accept_ra - INTEGER |
1da177e4 | 1121 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 1122 | |
026359bc TA |
1123 | It also determines whether or not to transmit Router |
1124 | Solicitations. If and only if the functional setting is to | |
1125 | accept Router Advertisements, Router Solicitations will be | |
1126 | transmitted. | |
1127 | ||
ae8abfa0 TG |
1128 | Possible values are: |
1129 | 0 Do not accept Router Advertisements. | |
1130 | 1 Accept Router Advertisements if forwarding is disabled. | |
1131 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1132 | even if forwarding is enabled. | |
1133 | ||
1da177e4 LT |
1134 | Functional default: enabled if local forwarding is disabled. |
1135 | disabled if local forwarding is enabled. | |
1136 | ||
65f5c7c1 YH |
1137 | accept_ra_defrtr - BOOLEAN |
1138 | Learn default router in Router Advertisement. | |
1139 | ||
1140 | Functional default: enabled if accept_ra is enabled. | |
1141 | disabled if accept_ra is disabled. | |
1142 | ||
c4fd30eb | 1143 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 1144 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
1145 | |
1146 | Functional default: enabled if accept_ra is enabled. | |
1147 | disabled if accept_ra is disabled. | |
1148 | ||
09c884d4 YH |
1149 | accept_ra_rt_info_max_plen - INTEGER |
1150 | Maximum prefix length of Route Information in RA. | |
1151 | ||
1152 | Route Information w/ prefix larger than or equal to this | |
1153 | variable shall be ignored. | |
1154 | ||
1155 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1156 | -1 if accept_ra_rtr_pref is disabled. | |
1157 | ||
930d6ff2 YH |
1158 | accept_ra_rtr_pref - BOOLEAN |
1159 | Accept Router Preference in RA. | |
1160 | ||
1161 | Functional default: enabled if accept_ra is enabled. | |
1162 | disabled if accept_ra is disabled. | |
1163 | ||
1da177e4 LT |
1164 | accept_redirects - BOOLEAN |
1165 | Accept Redirects. | |
1166 | ||
1167 | Functional default: enabled if local forwarding is disabled. | |
1168 | disabled if local forwarding is enabled. | |
1169 | ||
0bcbc926 YH |
1170 | accept_source_route - INTEGER |
1171 | Accept source routing (routing extension header). | |
1172 | ||
bb4dbf9e | 1173 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
1174 | < 0: Do not accept routing header. |
1175 | ||
1176 | Default: 0 | |
1177 | ||
1da177e4 | 1178 | autoconf - BOOLEAN |
e18f5feb | 1179 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
1180 | Advertisements. |
1181 | ||
c4fd30eb YH |
1182 | Functional default: enabled if accept_ra_pinfo is enabled. |
1183 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
1184 | |
1185 | dad_transmits - INTEGER | |
1186 | The amount of Duplicate Address Detection probes to send. | |
1187 | Default: 1 | |
e18f5feb | 1188 | |
605b91c8 | 1189 | forwarding - INTEGER |
e18f5feb | 1190 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 1191 | |
e18f5feb | 1192 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
1193 | interfaces; mixed router/host scenarios are rather uncommon. |
1194 | ||
ae8abfa0 TG |
1195 | Possible values are: |
1196 | 0 Forwarding disabled | |
1197 | 1 Forwarding enabled | |
ae8abfa0 TG |
1198 | |
1199 | FALSE (0): | |
1da177e4 LT |
1200 | |
1201 | By default, Host behaviour is assumed. This means: | |
1202 | ||
1203 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
1204 | 2. If accept_ra is TRUE (default), transmit Router |
1205 | Solicitations. | |
e18f5feb | 1206 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
1207 | Advertisements (and do autoconfiguration). |
1208 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1209 | ||
ae8abfa0 | 1210 | TRUE (1): |
1da177e4 | 1211 | |
e18f5feb | 1212 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
1213 | This means exactly the reverse from the above: |
1214 | ||
1215 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 1216 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 1217 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
1218 | 4. Redirects are ignored. |
1219 | ||
ae8abfa0 TG |
1220 | Default: 0 (disabled) if global forwarding is disabled (default), |
1221 | otherwise 1 (enabled). | |
1da177e4 LT |
1222 | |
1223 | hop_limit - INTEGER | |
1224 | Default Hop Limit to set. | |
1225 | Default: 64 | |
1226 | ||
1227 | mtu - INTEGER | |
1228 | Default Maximum Transfer Unit | |
1229 | Default: 1280 (IPv6 required minimum) | |
1230 | ||
52e16356 YH |
1231 | router_probe_interval - INTEGER |
1232 | Minimum interval (in seconds) between Router Probing described | |
1233 | in RFC4191. | |
1234 | ||
1235 | Default: 60 | |
1236 | ||
1da177e4 LT |
1237 | router_solicitation_delay - INTEGER |
1238 | Number of seconds to wait after interface is brought up | |
1239 | before sending Router Solicitations. | |
1240 | Default: 1 | |
1241 | ||
1242 | router_solicitation_interval - INTEGER | |
1243 | Number of seconds to wait between Router Solicitations. | |
1244 | Default: 4 | |
1245 | ||
1246 | router_solicitations - INTEGER | |
e18f5feb | 1247 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1248 | routers are present. |
1249 | Default: 3 | |
1250 | ||
1251 | use_tempaddr - INTEGER | |
1252 | Preference for Privacy Extensions (RFC3041). | |
1253 | <= 0 : disable Privacy Extensions | |
1254 | == 1 : enable Privacy Extensions, but prefer public | |
1255 | addresses over temporary addresses. | |
1256 | > 1 : enable Privacy Extensions and prefer temporary | |
1257 | addresses over public addresses. | |
1258 | Default: 0 (for most devices) | |
1259 | -1 (for point-to-point devices and loopback devices) | |
1260 | ||
1261 | temp_valid_lft - INTEGER | |
1262 | valid lifetime (in seconds) for temporary addresses. | |
1263 | Default: 604800 (7 days) | |
1264 | ||
1265 | temp_prefered_lft - INTEGER | |
1266 | Preferred lifetime (in seconds) for temporary addresses. | |
1267 | Default: 86400 (1 day) | |
1268 | ||
1269 | max_desync_factor - INTEGER | |
1270 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1271 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1272 | other and generate new addresses at exactly the same time. |
1273 | value is in seconds. | |
1274 | Default: 600 | |
e18f5feb | 1275 | |
1da177e4 LT |
1276 | regen_max_retry - INTEGER |
1277 | Number of attempts before give up attempting to generate | |
1278 | valid temporary addresses. | |
1279 | Default: 5 | |
1280 | ||
1281 | max_addresses - INTEGER | |
e79dc484 BH |
1282 | Maximum number of autoconfigured addresses per interface. Setting |
1283 | to zero disables the limitation. It is not recommended to set this | |
1284 | value too large (or to zero) because it would be an easy way to | |
1285 | crash the kernel by allowing too many addresses to be created. | |
1da177e4 LT |
1286 | Default: 16 |
1287 | ||
778d80be | 1288 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1289 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1290 | will be dynamically set to TRUE if DAD fails for the link-local | |
1291 | address. | |
778d80be YH |
1292 | Default: FALSE (enable IPv6 operation) |
1293 | ||
56d417b1 BH |
1294 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1295 | it will dynamically create a link-local address on the given | |
1296 | interface and start Duplicate Address Detection, if necessary. | |
1297 | ||
1298 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1299 | it will dynamically delete all address on the given interface. | |
1300 | ||
1b34be74 YH |
1301 | accept_dad - INTEGER |
1302 | Whether to accept DAD (Duplicate Address Detection). | |
1303 | 0: Disable DAD | |
1304 | 1: Enable DAD (default) | |
1305 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1306 | link-local address has been found. | |
1307 | ||
f7734fdf OP |
1308 | force_tllao - BOOLEAN |
1309 | Enable sending the target link-layer address option even when | |
1310 | responding to a unicast neighbor solicitation. | |
1311 | Default: FALSE | |
1312 | ||
1313 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1314 | ||
1315 | "The option MUST be included for multicast solicitations in order to | |
1316 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1317 | does not have a cache entry to return a Neighbor Advertisements | |
1318 | message. When responding to unicast solicitations, the option can be | |
1319 | omitted since the sender of the solicitation has the correct link- | |
1320 | layer address; otherwise it would not have be able to send the unicast | |
1321 | solicitation in the first place. However, including the link-layer | |
1322 | address in this case adds little overhead and eliminates a potential | |
1323 | race condition where the sender deletes the cached link-layer address | |
1324 | prior to receiving a response to a previous solicitation." | |
1325 | ||
1da177e4 LT |
1326 | icmp/*: |
1327 | ratelimit - INTEGER | |
1328 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1329 | 0 to disable any limiting, |
1330 | otherwise the minimal space between responses in milliseconds. | |
1331 | Default: 1000 | |
1da177e4 LT |
1332 | |
1333 | ||
1334 | IPv6 Update by: | |
1335 | Pekka Savola <pekkas@netcore.fi> | |
1336 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1337 | ||
1338 | ||
1339 | /proc/sys/net/bridge/* Variables: | |
1340 | ||
1341 | bridge-nf-call-arptables - BOOLEAN | |
1342 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1343 | 0 : disable this. | |
1344 | Default: 1 | |
1345 | ||
1346 | bridge-nf-call-iptables - BOOLEAN | |
1347 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1348 | 0 : disable this. | |
1349 | Default: 1 | |
1350 | ||
1351 | bridge-nf-call-ip6tables - BOOLEAN | |
1352 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1353 | 0 : disable this. | |
1354 | Default: 1 | |
1355 | ||
1356 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1357 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1358 | 0 : disable this. | |
4981682c | 1359 | Default: 0 |
516299d2 MM |
1360 | |
1361 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1362 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 | 1363 | 0 : disable this. |
4981682c | 1364 | Default: 0 |
1da177e4 | 1365 | |
4981682c PNA |
1366 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1367 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1368 | interface on the bridge and set the netfilter input device to the vlan. | |
1369 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1370 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1371 | vlan interface is found, or this switch is off, the input device is | |
1372 | set to the bridge interface. | |
1373 | 0: disable bridge netfilter vlan interface lookup. | |
1374 | Default: 0 | |
1da177e4 | 1375 | |
32e8d494 VY |
1376 | proc/sys/net/sctp/* Variables: |
1377 | ||
1378 | addip_enable - BOOLEAN | |
1379 | Enable or disable extension of Dynamic Address Reconfiguration | |
1380 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1381 | the ability to dynamically add and remove new addresses for the SCTP | |
1382 | associations. | |
1383 | ||
1384 | 1: Enable extension. | |
1385 | ||
1386 | 0: Disable extension. | |
1387 | ||
1388 | Default: 0 | |
1389 | ||
1390 | addip_noauth_enable - BOOLEAN | |
1391 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1392 | authentication to protect the operations of adding or removing new | |
1393 | addresses. This requirement is mandated so that unauthorized hosts | |
1394 | would not be able to hijack associations. However, older | |
1395 | implementations may not have implemented this requirement while | |
1396 | allowing the ADD-IP extension. For reasons of interoperability, | |
1397 | we provide this variable to control the enforcement of the | |
1398 | authentication requirement. | |
1399 | ||
1400 | 1: Allow ADD-IP extension to be used without authentication. This | |
1401 | should only be set in a closed environment for interoperability | |
1402 | with older implementations. | |
1403 | ||
1404 | 0: Enforce the authentication requirement | |
1405 | ||
1406 | Default: 0 | |
1407 | ||
1408 | auth_enable - BOOLEAN | |
1409 | Enable or disable Authenticated Chunks extension. This extension | |
1410 | provides the ability to send and receive authenticated chunks and is | |
1411 | required for secure operation of Dynamic Address Reconfiguration | |
1412 | (ADD-IP) extension. | |
1413 | ||
1414 | 1: Enable this extension. | |
1415 | 0: Disable this extension. | |
1416 | ||
1417 | Default: 0 | |
1418 | ||
1419 | prsctp_enable - BOOLEAN | |
1420 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1421 | is used to notify peers that a given DATA should no longer be expected. | |
1422 | ||
1423 | 1: Enable extension | |
1424 | 0: Disable | |
1425 | ||
1426 | Default: 1 | |
1427 | ||
1428 | max_burst - INTEGER | |
1429 | The limit of the number of new packets that can be initially sent. It | |
1430 | controls how bursty the generated traffic can be. | |
1431 | ||
1432 | Default: 4 | |
1433 | ||
1434 | association_max_retrans - INTEGER | |
1435 | Set the maximum number for retransmissions that an association can | |
1436 | attempt deciding that the remote end is unreachable. If this value | |
1437 | is exceeded, the association is terminated. | |
1438 | ||
1439 | Default: 10 | |
1440 | ||
1441 | max_init_retransmits - INTEGER | |
1442 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1443 | that an association will attempt before declaring the destination | |
1444 | unreachable and terminating. | |
1445 | ||
1446 | Default: 8 | |
1447 | ||
1448 | path_max_retrans - INTEGER | |
1449 | The maximum number of retransmissions that will be attempted on a given | |
1450 | path. Once this threshold is exceeded, the path is considered | |
1451 | unreachable, and new traffic will use a different path when the | |
1452 | association is multihomed. | |
1453 | ||
1454 | Default: 5 | |
1455 | ||
5aa93bcf NH |
1456 | pf_retrans - INTEGER |
1457 | The number of retransmissions that will be attempted on a given path | |
1458 | before traffic is redirected to an alternate transport (should one | |
1459 | exist). Note this is distinct from path_max_retrans, as a path that | |
1460 | passes the pf_retrans threshold can still be used. Its only | |
1461 | deprioritized when a transmission path is selected by the stack. This | |
1462 | setting is primarily used to enable fast failover mechanisms without | |
1463 | having to reduce path_max_retrans to a very low value. See: | |
1464 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
1465 | for details. Note also that a value of pf_retrans > path_max_retrans | |
1466 | disables this feature | |
1467 | ||
1468 | Default: 0 | |
1469 | ||
32e8d494 VY |
1470 | rto_initial - INTEGER |
1471 | The initial round trip timeout value in milliseconds that will be used | |
1472 | in calculating round trip times. This is the initial time interval | |
1473 | for retransmissions. | |
1474 | ||
1475 | Default: 3000 | |
1da177e4 | 1476 | |
32e8d494 VY |
1477 | rto_max - INTEGER |
1478 | The maximum value (in milliseconds) of the round trip timeout. This | |
1479 | is the largest time interval that can elapse between retransmissions. | |
1480 | ||
1481 | Default: 60000 | |
1482 | ||
1483 | rto_min - INTEGER | |
1484 | The minimum value (in milliseconds) of the round trip timeout. This | |
1485 | is the smallest time interval the can elapse between retransmissions. | |
1486 | ||
1487 | Default: 1000 | |
1488 | ||
1489 | hb_interval - INTEGER | |
1490 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1491 | are sent at the specified interval on idle paths to probe the state of | |
1492 | a given path between 2 associations. | |
1493 | ||
1494 | Default: 30000 | |
1495 | ||
1496 | sack_timeout - INTEGER | |
1497 | The amount of time (in milliseconds) that the implementation will wait | |
1498 | to send a SACK. | |
1499 | ||
1500 | Default: 200 | |
1501 | ||
1502 | valid_cookie_life - INTEGER | |
1503 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1504 | is used during association establishment. | |
1505 | ||
1506 | Default: 60000 | |
1507 | ||
1508 | cookie_preserve_enable - BOOLEAN | |
1509 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1510 | that is used during the establishment phase of SCTP association | |
1511 | ||
1512 | 1: Enable cookie lifetime extension. | |
1513 | 0: Disable | |
1514 | ||
1515 | Default: 1 | |
1516 | ||
3c68198e NH |
1517 | cookie_hmac_alg - STRING |
1518 | Select the hmac algorithm used when generating the cookie value sent by | |
1519 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
1520 | Valid values are: | |
1521 | * md5 | |
1522 | * sha1 | |
1523 | * none | |
1524 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
1525 | configuarion of those algorithms at build time (CONFIG_CRYPTO_MD5 and | |
1526 | CONFIG_CRYPTO_SHA1). | |
1527 | ||
1528 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
1529 | available, else none. | |
1530 | ||
32e8d494 VY |
1531 | rcvbuf_policy - INTEGER |
1532 | Determines if the receive buffer is attributed to the socket or to | |
1533 | association. SCTP supports the capability to create multiple | |
1534 | associations on a single socket. When using this capability, it is | |
1535 | possible that a single stalled association that's buffering a lot | |
1536 | of data may block other associations from delivering their data by | |
1537 | consuming all of the receive buffer space. To work around this, | |
1538 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1539 | to each association instead of the socket. This prevents the described | |
1540 | blocking. | |
1541 | ||
1542 | 1: rcvbuf space is per association | |
1543 | 0: recbuf space is per socket | |
1544 | ||
1545 | Default: 0 | |
1546 | ||
1547 | sndbuf_policy - INTEGER | |
1548 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1549 | ||
1550 | 1: Send buffer is tracked per association | |
1551 | 0: Send buffer is tracked per socket. | |
1552 | ||
1553 | Default: 0 | |
1554 | ||
1555 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1556 | Number of pages allowed for queueing by all SCTP sockets. | |
1557 | ||
1558 | min: Below this number of pages SCTP is not bothered about its | |
1559 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1560 | this number, SCTP starts to moderate memory usage. | |
1561 | ||
1562 | pressure: This value was introduced to follow format of tcp_mem. | |
1563 | ||
1564 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1565 | ||
1566 | Default is calculated at boot time from amount of available memory. | |
1567 | ||
1568 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
1569 | Only the first value ("min") is used, "default" and "max" are |
1570 | ignored. | |
1571 | ||
1572 | min: Minimal size of receive buffer used by SCTP socket. | |
1573 | It is guaranteed to each SCTP socket (but not association) even | |
1574 | under moderate memory pressure. | |
1575 | ||
1576 | Default: 1 page | |
32e8d494 VY |
1577 | |
1578 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b | 1579 | Currently this tunable has no effect. |
32e8d494 | 1580 | |
72388433 BD |
1581 | addr_scope_policy - INTEGER |
1582 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
1583 | ||
1584 | 0 - Disable IPv4 address scoping | |
1585 | 1 - Enable IPv4 address scoping | |
1586 | 2 - Follow draft but allow IPv4 private addresses | |
1587 | 3 - Follow draft but allow IPv4 link local addresses | |
1588 | ||
1589 | Default: 1 | |
1590 | ||
1da177e4 | 1591 | |
4edc2f34 | 1592 | /proc/sys/net/core/* |
c60f6aa8 | 1593 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. |
705efc3b | 1594 | |
4edc2f34 SH |
1595 | |
1596 | /proc/sys/net/unix/* | |
705efc3b WT |
1597 | max_dgram_qlen - INTEGER |
1598 | The maximum length of dgram socket receive queue | |
1599 | ||
1600 | Default: 10 | |
1601 | ||
1602 | ||
1603 | UNDOCUMENTED: | |
4edc2f34 SH |
1604 | |
1605 | /proc/sys/net/irda/* | |
1606 | fast_poll_increase FIXME | |
1607 | warn_noreply_time FIXME | |
1608 | discovery_slots FIXME | |
1609 | slot_timeout FIXME | |
1610 | max_baud_rate FIXME | |
1611 | discovery_timeout FIXME | |
1612 | lap_keepalive_time FIXME | |
1613 | max_noreply_time FIXME | |
1614 | max_tx_data_size FIXME | |
1615 | max_tx_window FIXME | |
1616 | min_tx_turn_time FIXME |