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. | |
cc868028 | 33 | Default: 1024 |
cbaf087a | 34 | |
8b5c171b ED |
35 | neigh/default/unres_qlen_bytes - INTEGER |
36 | The maximum number of bytes which may be used by packets | |
37 | queued for each unresolved address by other network layers. | |
38 | (added in linux 3.3) | |
cc868028 SW |
39 | Seting negative value is meaningless and will retrun error. |
40 | Default: 65536 Bytes(64KB) | |
8b5c171b ED |
41 | |
42 | neigh/default/unres_qlen - INTEGER | |
43 | The maximum number of packets which may be queued for each | |
44 | unresolved address by other network layers. | |
45 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
cc868028 | 46 | Prior to linux 3.3, the default value is 3 which may cause |
5d248c49 | 47 | unexpected packet loss. The current default value is calculated |
cc868028 SW |
48 | according to default value of unres_qlen_bytes and true size of |
49 | packet. | |
50 | Default: 31 | |
8b5c171b | 51 | |
1da177e4 LT |
52 | mtu_expires - INTEGER |
53 | Time, in seconds, that cached PMTU information is kept. | |
54 | ||
55 | min_adv_mss - INTEGER | |
56 | The advertised MSS depends on the first hop route MTU, but will | |
57 | never be lower than this setting. | |
58 | ||
59 | IP Fragmentation: | |
60 | ||
61 | ipfrag_high_thresh - INTEGER | |
e18f5feb | 62 | Maximum memory used to reassemble IP fragments. When |
1da177e4 LT |
63 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
64 | the fragment handler will toss packets until ipfrag_low_thresh | |
65 | is reached. | |
e18f5feb | 66 | |
1da177e4 | 67 | ipfrag_low_thresh - INTEGER |
e18f5feb | 68 | See ipfrag_high_thresh |
1da177e4 LT |
69 | |
70 | ipfrag_time - INTEGER | |
e18f5feb | 71 | Time in seconds to keep an IP fragment in memory. |
1da177e4 LT |
72 | |
73 | ipfrag_secret_interval - INTEGER | |
e18f5feb | 74 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
75 | for the hash secret) for IP fragments. |
76 | Default: 600 | |
77 | ||
89cee8b1 | 78 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
79 | ipfrag_max_dist is a non-negative integer value which defines the |
80 | maximum "disorder" which is allowed among fragments which share a | |
81 | common IP source address. Note that reordering of packets is | |
82 | not unusual, but if a large number of fragments arrive from a source | |
83 | IP address while a particular fragment queue remains incomplete, it | |
84 | probably indicates that one or more fragments belonging to that queue | |
85 | have been lost. When ipfrag_max_dist is positive, an additional check | |
86 | is done on fragments before they are added to a reassembly queue - if | |
87 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
88 | address between additions to any IP fragment queue using that source | |
89 | address, it's presumed that one or more fragments in the queue are | |
90 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
91 | started. An ipfrag_max_dist value of zero disables this check. |
92 | ||
93 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
94 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
95 | reordering of packets occurs, which could lead to poor application |
96 | performance. Using a very large value, e.g. 50000, increases the | |
97 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
98 | from different IP datagrams, which could result in data corruption. |
99 | Default: 64 | |
100 | ||
1da177e4 LT |
101 | INET peer storage: |
102 | ||
103 | inet_peer_threshold - INTEGER | |
e18f5feb | 104 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
105 | entries will be thrown aggressively. This threshold also determines |
106 | entries' time-to-live and time intervals between garbage collection | |
107 | passes. More entries, less time-to-live, less GC interval. | |
108 | ||
109 | inet_peer_minttl - INTEGER | |
110 | Minimum time-to-live of entries. Should be enough to cover fragment | |
111 | time-to-live on the reassembling side. This minimum time-to-live is | |
112 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 113 | Measured in seconds. |
1da177e4 LT |
114 | |
115 | inet_peer_maxttl - INTEGER | |
116 | Maximum time-to-live of entries. Unused entries will expire after | |
117 | this period of time if there is no memory pressure on the pool (i.e. | |
118 | when the number of entries in the pool is very small). | |
77a538d5 | 119 | Measured in seconds. |
1da177e4 | 120 | |
e18f5feb | 121 | TCP variables: |
1da177e4 | 122 | |
ef56e622 SH |
123 | somaxconn - INTEGER |
124 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
125 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
126 | for TCP sockets. | |
127 | ||
9772efb9 | 128 | tcp_abc - INTEGER |
b3a8a40d SH |
129 | Controls Appropriate Byte Count (ABC) defined in RFC3465. |
130 | ABC is a way of increasing congestion window (cwnd) more slowly | |
131 | in response to partial acknowledgments. | |
132 | Possible values are: | |
133 | 0 increase cwnd once per acknowledgment (no ABC) | |
134 | 1 increase cwnd once per acknowledgment of full sized segment | |
135 | 2 allow increase cwnd by two if acknowledgment is | |
136 | of two segments to compensate for delayed acknowledgments. | |
137 | Default: 0 (off) | |
9772efb9 | 138 | |
ef56e622 SH |
139 | tcp_abort_on_overflow - BOOLEAN |
140 | If listening service is too slow to accept new connections, | |
141 | reset them. Default state is FALSE. It means that if overflow | |
142 | occurred due to a burst, connection will recover. Enable this | |
143 | option _only_ if you are really sure that listening daemon | |
144 | cannot be tuned to accept connections faster. Enabling this | |
145 | option can harm clients of your server. | |
1da177e4 | 146 | |
ef56e622 SH |
147 | tcp_adv_win_scale - INTEGER |
148 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
149 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
150 | if it is <= 0. | |
0147fc05 | 151 | Possible values are [-31, 31], inclusive. |
b49960a0 | 152 | Default: 1 |
1da177e4 | 153 | |
ef56e622 SH |
154 | tcp_allowed_congestion_control - STRING |
155 | Show/set the congestion control choices available to non-privileged | |
156 | processes. The list is a subset of those listed in | |
157 | tcp_available_congestion_control. | |
158 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 159 | |
ef56e622 SH |
160 | tcp_app_win - INTEGER |
161 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
162 | buffer. Value 0 is special, it means that nothing is reserved. | |
163 | Default: 31 | |
1da177e4 | 164 | |
ef56e622 SH |
165 | tcp_available_congestion_control - STRING |
166 | Shows the available congestion control choices that are registered. | |
167 | More congestion control algorithms may be available as modules, | |
168 | but not loaded. | |
1da177e4 | 169 | |
71599cd1 | 170 | tcp_base_mss - INTEGER |
4edc2f34 SH |
171 | The initial value of search_low to be used by the packetization layer |
172 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
173 | this is the initial MSS used by the connection. | |
71599cd1 | 174 | |
ef56e622 SH |
175 | tcp_congestion_control - STRING |
176 | Set the congestion control algorithm to be used for new | |
177 | connections. The algorithm "reno" is always available, but | |
178 | additional choices may be available based on kernel configuration. | |
179 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
180 | For passive connections, the listener congestion control choice |
181 | is inherited. | |
182 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
1da177e4 | 183 | |
519855c5 WAS |
184 | tcp_cookie_size - INTEGER |
185 | Default size of TCP Cookie Transactions (TCPCT) option, that may be | |
186 | overridden on a per socket basis by the TCPCT socket option. | |
187 | Values greater than the maximum (16) are interpreted as the maximum. | |
188 | Values greater than zero and less than the minimum (8) are interpreted | |
189 | as the minimum. Odd values are interpreted as the next even value. | |
190 | Default: 0 (off). | |
191 | ||
ef56e622 SH |
192 | tcp_dsack - BOOLEAN |
193 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 194 | |
eed530b6 YC |
195 | tcp_early_retrans - INTEGER |
196 | Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold | |
197 | for triggering fast retransmit when the amount of outstanding data is | |
198 | small and when no previously unsent data can be transmitted (such | |
199 | that limited transmit could be used). | |
200 | Possible values: | |
201 | 0 disables ER | |
202 | 1 enables ER | |
203 | 2 enables ER but delays fast recovery and fast retransmit | |
204 | by a fourth of RTT. This mitigates connection falsely | |
205 | recovers when network has a small degree of reordering | |
206 | (less than 3 packets). | |
207 | Default: 2 | |
208 | ||
34a6ef38 | 209 | tcp_ecn - INTEGER |
7e3a2dc5 RJ |
210 | Control use of Explicit Congestion Notification (ECN) by TCP. |
211 | ECN is used only when both ends of the TCP connection indicate | |
212 | support for it. This feature is useful in avoiding losses due | |
213 | to congestion by allowing supporting routers to signal | |
214 | congestion before having to drop packets. | |
255cac91 | 215 | Possible values are: |
7e3a2dc5 | 216 | 0 Disable ECN. Neither initiate nor accept ECN. |
3d55b323 VS |
217 | 1 Enable ECN when requested by incoming connections and |
218 | also request ECN on outgoing connection attempts. | |
219 | 2 Enable ECN when requested by incoming connections | |
7e3a2dc5 | 220 | but do not request ECN on outgoing connections. |
255cac91 | 221 | Default: 2 |
ef56e622 SH |
222 | |
223 | tcp_fack - BOOLEAN | |
224 | Enable FACK congestion avoidance and fast retransmission. | |
225 | The value is not used, if tcp_sack is not enabled. | |
1da177e4 LT |
226 | |
227 | tcp_fin_timeout - INTEGER | |
d825da2e RJ |
228 | The length of time an orphaned (no longer referenced by any |
229 | application) connection will remain in the FIN_WAIT_2 state | |
230 | before it is aborted at the local end. While a perfectly | |
231 | valid "receive only" state for an un-orphaned connection, an | |
232 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
233 | forever for the remote to close its end of the connection. | |
234 | Cf. tcp_max_orphans | |
235 | Default: 60 seconds | |
1da177e4 | 236 | |
89808060 | 237 | tcp_frto - INTEGER |
cd99889c IJ |
238 | Enables Forward RTO-Recovery (F-RTO) defined in RFC4138. |
239 | F-RTO is an enhanced recovery algorithm for TCP retransmission | |
ef56e622 SH |
240 | timeouts. It is particularly beneficial in wireless environments |
241 | where packet loss is typically due to random radio interference | |
564262c1 | 242 | rather than intermediate router congestion. F-RTO is sender-side |
4edc2f34 SH |
243 | only modification. Therefore it does not require any support from |
244 | the peer. | |
245 | ||
cd99889c IJ |
246 | If set to 1, basic version is enabled. 2 enables SACK enhanced |
247 | F-RTO if flow uses SACK. The basic version can be used also when | |
564262c1 | 248 | SACK is in use though scenario(s) with it exists where F-RTO |
cd99889c IJ |
249 | interacts badly with the packet counting of the SACK enabled TCP |
250 | flow. | |
1da177e4 | 251 | |
89808060 IJ |
252 | tcp_frto_response - INTEGER |
253 | When F-RTO has detected that a TCP retransmission timeout was | |
254 | spurious (i.e, the timeout would have been avoided had TCP set a | |
255 | longer retransmission timeout), TCP has several options what to do | |
256 | next. Possible values are: | |
257 | 0 Rate halving based; a smooth and conservative response, | |
258 | results in halved cwnd and ssthresh after one RTT | |
259 | 1 Very conservative response; not recommended because even | |
260 | though being valid, it interacts poorly with the rest of | |
261 | Linux TCP, halves cwnd and ssthresh immediately | |
262 | 2 Aggressive response; undoes congestion control measures | |
263 | that are now known to be unnecessary (ignoring the | |
264 | possibility of a lost retransmission that would require | |
265 | TCP to be more cautious), cwnd and ssthresh are restored | |
266 | to the values prior timeout | |
267 | Default: 0 (rate halving based) | |
268 | ||
ef56e622 SH |
269 | tcp_keepalive_time - INTEGER |
270 | How often TCP sends out keepalive messages when keepalive is enabled. | |
271 | Default: 2hours. | |
1da177e4 | 272 | |
ef56e622 SH |
273 | tcp_keepalive_probes - INTEGER |
274 | How many keepalive probes TCP sends out, until it decides that the | |
275 | connection is broken. Default value: 9. | |
276 | ||
277 | tcp_keepalive_intvl - INTEGER | |
278 | How frequently the probes are send out. Multiplied by | |
279 | tcp_keepalive_probes it is time to kill not responding connection, | |
280 | after probes started. Default value: 75sec i.e. connection | |
281 | will be aborted after ~11 minutes of retries. | |
282 | ||
283 | tcp_low_latency - BOOLEAN | |
284 | If set, the TCP stack makes decisions that prefer lower | |
285 | latency as opposed to higher throughput. By default, this | |
286 | option is not set meaning that higher throughput is preferred. | |
287 | An example of an application where this default should be | |
288 | changed would be a Beowulf compute cluster. | |
289 | Default: 0 | |
1da177e4 LT |
290 | |
291 | tcp_max_orphans - INTEGER | |
292 | Maximal number of TCP sockets not attached to any user file handle, | |
293 | held by system. If this number is exceeded orphaned connections are | |
294 | reset immediately and warning is printed. This limit exists | |
295 | only to prevent simple DoS attacks, you _must_ not rely on this | |
296 | or lower the limit artificially, but rather increase it | |
297 | (probably, after increasing installed memory), | |
298 | if network conditions require more than default value, | |
299 | and tune network services to linger and kill such states | |
300 | more aggressively. Let me to remind again: each orphan eats | |
301 | up to ~64K of unswappable memory. | |
302 | ||
81146ec1 IJ |
303 | tcp_max_ssthresh - INTEGER |
304 | Limited Slow-Start for TCP with large congestion windows (cwnd) defined in | |
305 | RFC3742. Limited slow-start is a mechanism to limit growth of the cwnd | |
306 | on the region where cwnd is larger than tcp_max_ssthresh. TCP increases cwnd | |
307 | by at most tcp_max_ssthresh segments, and by at least tcp_max_ssthresh/2 | |
308 | segments per RTT when the cwnd is above tcp_max_ssthresh. | |
309 | If TCP connection increased cwnd to thousands (or tens of thousands) segments, | |
310 | and thousands of packets were being dropped during slow-start, you can set | |
311 | tcp_max_ssthresh to improve performance for new TCP connection. | |
312 | Default: 0 (off) | |
313 | ||
1da177e4 | 314 | tcp_max_syn_backlog - INTEGER |
99b53bdd PP |
315 | Maximal number of remembered connection requests, which have not |
316 | received an acknowledgment from connecting client. | |
317 | The minimal value is 128 for low memory machines, and it will | |
318 | increase in proportion to the memory of machine. | |
319 | If server suffers from overload, try increasing this number. | |
1da177e4 | 320 | |
ef56e622 SH |
321 | tcp_max_tw_buckets - INTEGER |
322 | Maximal number of timewait sockets held by system simultaneously. | |
323 | If this number is exceeded time-wait socket is immediately destroyed | |
324 | and warning is printed. This limit exists only to prevent | |
325 | simple DoS attacks, you _must_ not lower the limit artificially, | |
326 | but rather increase it (probably, after increasing installed memory), | |
327 | if network conditions require more than default value. | |
1da177e4 | 328 | |
ef56e622 SH |
329 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
330 | min: below this number of pages TCP is not bothered about its | |
331 | memory appetite. | |
1da177e4 | 332 | |
ef56e622 SH |
333 | pressure: when amount of memory allocated by TCP exceeds this number |
334 | of pages, TCP moderates its memory consumption and enters memory | |
335 | pressure mode, which is exited when memory consumption falls | |
336 | under "min". | |
1da177e4 | 337 | |
ef56e622 | 338 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 339 | |
ef56e622 SH |
340 | Defaults are calculated at boot time from amount of available |
341 | memory. | |
1da177e4 | 342 | |
71599cd1 | 343 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 344 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
345 | automatically size the buffer (no greater than tcp_rmem[2]) to |
346 | match the size required by the path for full throughput. Enabled by | |
347 | default. | |
348 | ||
349 | tcp_mtu_probing - INTEGER | |
350 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
351 | values: | |
352 | 0 - Disabled | |
353 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
354 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
355 | ||
356 | tcp_no_metrics_save - BOOLEAN | |
357 | By default, TCP saves various connection metrics in the route cache | |
358 | when the connection closes, so that connections established in the | |
359 | near future can use these to set initial conditions. Usually, this | |
360 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 361 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
362 | connections. |
363 | ||
ef56e622 | 364 | tcp_orphan_retries - INTEGER |
5d789229 DL |
365 | This value influences the timeout of a locally closed TCP connection, |
366 | when RTO retransmissions remain unacknowledged. | |
367 | See tcp_retries2 for more details. | |
368 | ||
06b8fc5d | 369 | The default value is 8. |
5d789229 | 370 | If your machine is a loaded WEB server, |
ef56e622 SH |
371 | you should think about lowering this value, such sockets |
372 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
373 | |
374 | tcp_reordering - INTEGER | |
375 | Maximal reordering of packets in a TCP stream. | |
e18f5feb | 376 | Default: 3 |
1da177e4 LT |
377 | |
378 | tcp_retrans_collapse - BOOLEAN | |
379 | Bug-to-bug compatibility with some broken printers. | |
380 | On retransmit try to send bigger packets to work around bugs in | |
381 | certain TCP stacks. | |
382 | ||
ef56e622 | 383 | tcp_retries1 - INTEGER |
5d789229 DL |
384 | This value influences the time, after which TCP decides, that |
385 | something is wrong due to unacknowledged RTO retransmissions, | |
386 | and reports this suspicion to the network layer. | |
387 | See tcp_retries2 for more details. | |
388 | ||
389 | RFC 1122 recommends at least 3 retransmissions, which is the | |
390 | default. | |
1da177e4 | 391 | |
ef56e622 | 392 | tcp_retries2 - INTEGER |
5d789229 DL |
393 | This value influences the timeout of an alive TCP connection, |
394 | when RTO retransmissions remain unacknowledged. | |
395 | Given a value of N, a hypothetical TCP connection following | |
396 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
397 | retransmit N times before killing the connection at the (N+1)th RTO. | |
398 | ||
399 | The default value of 15 yields a hypothetical timeout of 924.6 | |
400 | seconds and is a lower bound for the effective timeout. | |
401 | TCP will effectively time out at the first RTO which exceeds the | |
402 | hypothetical timeout. | |
403 | ||
404 | RFC 1122 recommends at least 100 seconds for the timeout, | |
405 | which corresponds to a value of at least 8. | |
1da177e4 | 406 | |
ef56e622 SH |
407 | tcp_rfc1337 - BOOLEAN |
408 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
409 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
410 | assassination. | |
411 | Default: 0 | |
1da177e4 LT |
412 | |
413 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
414 | min: Minimal size of receive buffer used by TCP sockets. | |
415 | It is guaranteed to each TCP socket, even under moderate memory | |
416 | pressure. | |
6539fefd | 417 | Default: 1 page |
1da177e4 | 418 | |
53025f5e | 419 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
420 | This value overrides net.core.rmem_default used by other protocols. |
421 | Default: 87380 bytes. This value results in window of 65535 with | |
422 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
423 | less for default tcp_app_win. See below about these variables. | |
424 | ||
425 | max: maximal size of receive buffer allowed for automatically | |
426 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
427 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
428 | automatic tuning of that socket's receive buffer size, in which | |
429 | case this value is ignored. | |
b49960a0 | 430 | Default: between 87380B and 6MB, depending on RAM size. |
1da177e4 | 431 | |
ef56e622 SH |
432 | tcp_sack - BOOLEAN |
433 | Enable select acknowledgments (SACKS). | |
1da177e4 | 434 | |
ef56e622 SH |
435 | tcp_slow_start_after_idle - BOOLEAN |
436 | If set, provide RFC2861 behavior and time out the congestion | |
437 | window after an idle period. An idle period is defined at | |
438 | the current RTO. If unset, the congestion window will not | |
439 | be timed out after an idle period. | |
440 | Default: 1 | |
1da177e4 | 441 | |
ef56e622 | 442 | tcp_stdurg - BOOLEAN |
4edc2f34 | 443 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
444 | Most hosts use the older BSD interpretation, so if you turn this on |
445 | Linux might not communicate correctly with them. | |
446 | Default: FALSE | |
1da177e4 | 447 | |
ef56e622 SH |
448 | tcp_synack_retries - INTEGER |
449 | Number of times SYNACKs for a passive TCP connection attempt will | |
450 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
451 | is 5, which corresponds to 31seconds till the last retransmission |
452 | with the current initial RTO of 1second. With this the final timeout | |
453 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 454 | |
ef56e622 SH |
455 | tcp_syncookies - BOOLEAN |
456 | Only valid when the kernel was compiled with CONFIG_SYNCOOKIES | |
457 | Send out syncookies when the syn backlog queue of a socket | |
4edc2f34 | 458 | overflows. This is to prevent against the common 'SYN flood attack' |
ef56e622 | 459 | Default: FALSE |
1da177e4 | 460 | |
ef56e622 SH |
461 | Note, that syncookies is fallback facility. |
462 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 463 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
464 | in your logs, but investigation shows that they occur |
465 | because of overload with legal connections, you should tune | |
466 | another parameters until this warning disappear. | |
467 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 468 | |
ef56e622 SH |
469 | syncookies seriously violate TCP protocol, do not allow |
470 | to use TCP extensions, can result in serious degradation | |
471 | of some services (f.e. SMTP relaying), visible not by you, | |
472 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 473 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 474 | is seriously misconfigured. |
1da177e4 | 475 | |
cf60af03 YC |
476 | tcp_fastopen - INTEGER |
477 | Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data | |
478 | in the opening SYN packet. To use this feature, the client application | |
10467163 JC |
479 | must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than |
480 | connect() to perform a TCP handshake automatically. | |
481 | ||
482 | The values (bitmap) are | |
483 | 1: Enables sending data in the opening SYN on the client. | |
484 | 2: Enables TCP Fast Open on the server side, i.e., allowing data in | |
485 | a SYN packet to be accepted and passed to the application before | |
486 | 3-way hand shake finishes. | |
487 | 4: Send data in the opening SYN regardless of cookie availability and | |
488 | without a cookie option. | |
489 | 0x100: Accept SYN data w/o validating the cookie. | |
490 | 0x200: Accept data-in-SYN w/o any cookie option present. | |
491 | 0x400/0x800: Enable Fast Open on all listeners regardless of the | |
492 | TCP_FASTOPEN socket option. The two different flags designate two | |
493 | different ways of setting max_qlen without the TCP_FASTOPEN socket | |
494 | option. | |
cf60af03 YC |
495 | |
496 | Default: 0 | |
497 | ||
10467163 JC |
498 | Note that the client & server side Fast Open flags (1 and 2 |
499 | respectively) must be also enabled before the rest of flags can take | |
500 | effect. | |
501 | ||
502 | See include/net/tcp.h and the code for more details. | |
503 | ||
ef56e622 SH |
504 | tcp_syn_retries - INTEGER |
505 | Number of times initial SYNs for an active TCP connection attempt | |
506 | will be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
507 | is 6, which corresponds to 63seconds till the last restransmission |
508 | with the current initial RTO of 1second. With this the final timeout | |
509 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 SH |
510 | |
511 | tcp_timestamps - BOOLEAN | |
512 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 513 | |
1da177e4 | 514 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
515 | This allows control over what percentage of the congestion window |
516 | can be consumed by a single TSO frame. | |
517 | The setting of this parameter is a choice between burstiness and | |
518 | building larger TSO frames. | |
519 | Default: 3 | |
1da177e4 | 520 | |
ef56e622 SH |
521 | tcp_tw_recycle - BOOLEAN |
522 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
523 | It should not be changed without advice/request of technical | |
524 | experts. | |
1da177e4 | 525 | |
ef56e622 SH |
526 | tcp_tw_reuse - BOOLEAN |
527 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
528 | safe from protocol viewpoint. Default value is 0. | |
529 | It should not be changed without advice/request of technical | |
530 | experts. | |
ce7bc3bf | 531 | |
ef56e622 SH |
532 | tcp_window_scaling - BOOLEAN |
533 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 534 | |
ef56e622 | 535 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 536 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 537 | Each TCP socket has rights to use it due to fact of its birth. |
6539fefd | 538 | Default: 1 page |
9d7bcfc6 | 539 | |
53025f5e BF |
540 | default: initial size of send buffer used by TCP sockets. This |
541 | value overrides net.core.wmem_default used by other protocols. | |
542 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
543 | Default: 16K |
544 | ||
53025f5e BF |
545 | max: Maximal amount of memory allowed for automatically tuned |
546 | send buffers for TCP sockets. This value does not override | |
547 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
548 | automatic tuning of that socket's send buffer size, in which case | |
549 | this value is ignored. | |
550 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 551 | |
15d99e02 RJ |
552 | tcp_workaround_signed_windows - BOOLEAN |
553 | If set, assume no receipt of a window scaling option means the | |
554 | remote TCP is broken and treats the window as a signed quantity. | |
555 | If unset, assume the remote TCP is not broken even if we do | |
556 | not receive a window scaling option from them. | |
557 | Default: 0 | |
558 | ||
72d0b7a8 CL |
559 | tcp_dma_copybreak - INTEGER |
560 | Lower limit, in bytes, of the size of socket reads that will be | |
561 | offloaded to a DMA copy engine, if one is present in the system | |
562 | and CONFIG_NET_DMA is enabled. | |
563 | Default: 4096 | |
564 | ||
36e31b0a AP |
565 | tcp_thin_linear_timeouts - BOOLEAN |
566 | Enable dynamic triggering of linear timeouts for thin streams. | |
567 | If set, a check is performed upon retransmission by timeout to | |
568 | determine if the stream is thin (less than 4 packets in flight). | |
569 | As long as the stream is found to be thin, up to 6 linear | |
570 | timeouts may be performed before exponential backoff mode is | |
571 | initiated. This improves retransmission latency for | |
572 | non-aggressive thin streams, often found to be time-dependent. | |
573 | For more information on thin streams, see | |
574 | Documentation/networking/tcp-thin.txt | |
575 | Default: 0 | |
576 | ||
7e380175 AP |
577 | tcp_thin_dupack - BOOLEAN |
578 | Enable dynamic triggering of retransmissions after one dupACK | |
579 | for thin streams. If set, a check is performed upon reception | |
580 | of a dupACK to determine if the stream is thin (less than 4 | |
581 | packets in flight). As long as the stream is found to be thin, | |
582 | data is retransmitted on the first received dupACK. This | |
583 | improves retransmission latency for non-aggressive thin | |
584 | streams, often found to be time-dependent. | |
585 | For more information on thin streams, see | |
586 | Documentation/networking/tcp-thin.txt | |
587 | Default: 0 | |
588 | ||
46d3ceab ED |
589 | tcp_limit_output_bytes - INTEGER |
590 | Controls TCP Small Queue limit per tcp socket. | |
591 | TCP bulk sender tends to increase packets in flight until it | |
592 | gets losses notifications. With SNDBUF autotuning, this can | |
593 | result in a large amount of packets queued in qdisc/device | |
594 | on the local machine, hurting latency of other flows, for | |
595 | typical pfifo_fast qdiscs. | |
596 | tcp_limit_output_bytes limits the number of bytes on qdisc | |
597 | or device to reduce artificial RTT/cwnd and reduce bufferbloat. | |
598 | Note: For GSO/TSO enabled flows, we try to have at least two | |
599 | packets in flight. Reducing tcp_limit_output_bytes might also | |
600 | reduce the size of individual GSO packet (64KB being the max) | |
601 | Default: 131072 | |
602 | ||
282f23c6 ED |
603 | tcp_challenge_ack_limit - INTEGER |
604 | Limits number of Challenge ACK sent per second, as recommended | |
605 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
606 | Default: 100 | |
607 | ||
95766fff HA |
608 | UDP variables: |
609 | ||
610 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
611 | Number of pages allowed for queueing by all UDP sockets. | |
612 | ||
613 | min: Below this number of pages UDP is not bothered about its | |
614 | memory appetite. When amount of memory allocated by UDP exceeds | |
615 | this number, UDP starts to moderate memory usage. | |
616 | ||
617 | pressure: This value was introduced to follow format of tcp_mem. | |
618 | ||
619 | max: Number of pages allowed for queueing by all UDP sockets. | |
620 | ||
621 | Default is calculated at boot time from amount of available memory. | |
622 | ||
623 | udp_rmem_min - INTEGER | |
624 | Minimal size of receive buffer used by UDP sockets in moderation. | |
625 | Each UDP socket is able to use the size for receiving data, even if | |
626 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 627 | Default: 1 page |
95766fff HA |
628 | |
629 | udp_wmem_min - INTEGER | |
630 | Minimal size of send buffer used by UDP sockets in moderation. | |
631 | Each UDP socket is able to use the size for sending data, even if | |
632 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 633 | Default: 1 page |
95766fff | 634 | |
8802f616 PM |
635 | CIPSOv4 Variables: |
636 | ||
637 | cipso_cache_enable - BOOLEAN | |
638 | If set, enable additions to and lookups from the CIPSO label mapping | |
639 | cache. If unset, additions are ignored and lookups always result in a | |
640 | miss. However, regardless of the setting the cache is still | |
641 | invalidated when required when means you can safely toggle this on and | |
642 | off and the cache will always be "safe". | |
643 | Default: 1 | |
644 | ||
645 | cipso_cache_bucket_size - INTEGER | |
646 | The CIPSO label cache consists of a fixed size hash table with each | |
647 | hash bucket containing a number of cache entries. This variable limits | |
648 | the number of entries in each hash bucket; the larger the value the | |
649 | more CIPSO label mappings that can be cached. When the number of | |
650 | entries in a given hash bucket reaches this limit adding new entries | |
651 | causes the oldest entry in the bucket to be removed to make room. | |
652 | Default: 10 | |
653 | ||
654 | cipso_rbm_optfmt - BOOLEAN | |
655 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
656 | the CIPSO draft specification (see Documentation/netlabel for details). | |
657 | This means that when set the CIPSO tag will be padded with empty | |
658 | categories in order to make the packet data 32-bit aligned. | |
659 | Default: 0 | |
660 | ||
661 | cipso_rbm_structvalid - BOOLEAN | |
662 | If set, do a very strict check of the CIPSO option when | |
663 | ip_options_compile() is called. If unset, relax the checks done during | |
664 | ip_options_compile(). Either way is "safe" as errors are caught else | |
665 | where in the CIPSO processing code but setting this to 0 (False) should | |
666 | result in less work (i.e. it should be faster) but could cause problems | |
667 | with other implementations that require strict checking. | |
668 | Default: 0 | |
669 | ||
1da177e4 LT |
670 | IP Variables: |
671 | ||
672 | ip_local_port_range - 2 INTEGERS | |
673 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 674 | choose the local port. The first number is the first, the |
5d6bd861 FLVC |
675 | second the last local port number. The default values are |
676 | 32768 and 61000 respectively. | |
1da177e4 | 677 | |
e3826f1e AW |
678 | ip_local_reserved_ports - list of comma separated ranges |
679 | Specify the ports which are reserved for known third-party | |
680 | applications. These ports will not be used by automatic port | |
681 | assignments (e.g. when calling connect() or bind() with port | |
682 | number 0). Explicit port allocation behavior is unchanged. | |
683 | ||
684 | The format used for both input and output is a comma separated | |
685 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
686 | 10). Writing to the file will clear all previously reserved | |
687 | ports and update the current list with the one given in the | |
688 | input. | |
689 | ||
690 | Note that ip_local_port_range and ip_local_reserved_ports | |
691 | settings are independent and both are considered by the kernel | |
692 | when determining which ports are available for automatic port | |
693 | assignments. | |
694 | ||
695 | You can reserve ports which are not in the current | |
696 | ip_local_port_range, e.g.: | |
697 | ||
698 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
699 | 32000 61000 | |
700 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
701 | 8080,9148 | |
702 | ||
703 | although this is redundant. However such a setting is useful | |
704 | if later the port range is changed to a value that will | |
705 | include the reserved ports. | |
706 | ||
707 | Default: Empty | |
708 | ||
1da177e4 LT |
709 | ip_nonlocal_bind - BOOLEAN |
710 | If set, allows processes to bind() to non-local IP addresses, | |
711 | which can be quite useful - but may break some applications. | |
712 | Default: 0 | |
713 | ||
714 | ip_dynaddr - BOOLEAN | |
715 | If set non-zero, enables support for dynamic addresses. | |
716 | If set to a non-zero value larger than 1, a kernel log | |
717 | message will be printed when dynamic address rewriting | |
718 | occurs. | |
719 | Default: 0 | |
720 | ||
721 | icmp_echo_ignore_all - BOOLEAN | |
7ce31246 DM |
722 | If set non-zero, then the kernel will ignore all ICMP ECHO |
723 | requests sent to it. | |
724 | Default: 0 | |
725 | ||
1da177e4 | 726 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
727 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
728 | TIMESTAMP requests sent to it via broadcast/multicast. | |
729 | Default: 1 | |
1da177e4 LT |
730 | |
731 | icmp_ratelimit - INTEGER | |
732 | Limit the maximal rates for sending ICMP packets whose type matches | |
733 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
734 | 0 to disable any limiting, |
735 | otherwise the minimal space between responses in milliseconds. | |
736 | Default: 1000 | |
1da177e4 LT |
737 | |
738 | icmp_ratemask - INTEGER | |
739 | Mask made of ICMP types for which rates are being limited. | |
740 | Significant bits: IHGFEDCBA9876543210 | |
741 | Default mask: 0000001100000011000 (6168) | |
742 | ||
743 | Bit definitions (see include/linux/icmp.h): | |
744 | 0 Echo Reply | |
745 | 3 Destination Unreachable * | |
746 | 4 Source Quench * | |
747 | 5 Redirect | |
748 | 8 Echo Request | |
749 | B Time Exceeded * | |
750 | C Parameter Problem * | |
751 | D Timestamp Request | |
752 | E Timestamp Reply | |
753 | F Info Request | |
754 | G Info Reply | |
755 | H Address Mask Request | |
756 | I Address Mask Reply | |
757 | ||
758 | * These are rate limited by default (see default mask above) | |
759 | ||
760 | icmp_ignore_bogus_error_responses - BOOLEAN | |
761 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
762 | frames. Such violations are normally logged via a kernel warning. | |
763 | If this is set to TRUE, the kernel will not give such warnings, which | |
764 | will avoid log file clutter. | |
765 | Default: FALSE | |
766 | ||
95f7daf1 H |
767 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
768 | ||
769 | If zero, icmp error messages are sent with the primary address of | |
770 | the exiting interface. | |
e18f5feb | 771 | |
95f7daf1 H |
772 | If non-zero, the message will be sent with the primary address of |
773 | the interface that received the packet that caused the icmp error. | |
774 | This is the behaviour network many administrators will expect from | |
775 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 776 | much easier. |
95f7daf1 H |
777 | |
778 | Note that if no primary address exists for the interface selected, | |
779 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 780 | has one will be used regardless of this setting. |
95f7daf1 H |
781 | |
782 | Default: 0 | |
783 | ||
1da177e4 LT |
784 | igmp_max_memberships - INTEGER |
785 | Change the maximum number of multicast groups we can subscribe to. | |
786 | Default: 20 | |
787 | ||
d67ef35f JE |
788 | Theoretical maximum value is bounded by having to send a membership |
789 | report in a single datagram (i.e. the report can't span multiple | |
790 | datagrams, or risk confusing the switch and leaving groups you don't | |
791 | intend to). | |
1da177e4 | 792 | |
d67ef35f JE |
793 | The number of supported groups 'M' is bounded by the number of group |
794 | report entries you can fit into a single datagram of 65535 bytes. | |
795 | ||
796 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
797 | ||
798 | Group records are variable length, with a minimum of 12 bytes. | |
799 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
800 | ||
801 | (65536-24) / 12 = 5459 | |
802 | ||
803 | The value 5459 assumes no IP header options, so in practice | |
804 | this number may be lower. | |
805 | ||
806 | conf/interface/* changes special settings per interface (where | |
807 | "interface" is the name of your network interface) | |
808 | ||
809 | conf/all/* is special, changes the settings for all interfaces | |
1da177e4 LT |
810 | |
811 | log_martians - BOOLEAN | |
812 | Log packets with impossible addresses to kernel log. | |
813 | log_martians for the interface will be enabled if at least one of | |
814 | conf/{all,interface}/log_martians is set to TRUE, | |
815 | it will be disabled otherwise | |
816 | ||
817 | accept_redirects - BOOLEAN | |
818 | Accept ICMP redirect messages. | |
819 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
820 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
821 | forwarding for the interface is enabled | |
1da177e4 | 822 | or |
e18f5feb JDB |
823 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
824 | case forwarding for the interface is disabled | |
1da177e4 LT |
825 | accept_redirects for the interface will be disabled otherwise |
826 | default TRUE (host) | |
827 | FALSE (router) | |
828 | ||
829 | forwarding - BOOLEAN | |
830 | Enable IP forwarding on this interface. | |
831 | ||
832 | mc_forwarding - BOOLEAN | |
833 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
834 | and a multicast routing daemon is required. | |
e18f5feb JDB |
835 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
836 | routing for the interface | |
1da177e4 LT |
837 | |
838 | medium_id - INTEGER | |
839 | Integer value used to differentiate the devices by the medium they | |
840 | are attached to. Two devices can have different id values when | |
841 | the broadcast packets are received only on one of them. | |
842 | The default value 0 means that the device is the only interface | |
843 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 844 | |
1da177e4 LT |
845 | Currently, it is used to change the proxy_arp behavior: |
846 | the proxy_arp feature is enabled for packets forwarded between | |
847 | two devices attached to different media. | |
848 | ||
849 | proxy_arp - BOOLEAN | |
850 | Do proxy arp. | |
851 | proxy_arp for the interface will be enabled if at least one of | |
852 | conf/{all,interface}/proxy_arp is set to TRUE, | |
853 | it will be disabled otherwise | |
854 | ||
65324144 JDB |
855 | proxy_arp_pvlan - BOOLEAN |
856 | Private VLAN proxy arp. | |
857 | Basically allow proxy arp replies back to the same interface | |
858 | (from which the ARP request/solicitation was received). | |
859 | ||
860 | This is done to support (ethernet) switch features, like RFC | |
861 | 3069, where the individual ports are NOT allowed to | |
862 | communicate with each other, but they are allowed to talk to | |
863 | the upstream router. As described in RFC 3069, it is possible | |
864 | to allow these hosts to communicate through the upstream | |
865 | router by proxy_arp'ing. Don't need to be used together with | |
866 | proxy_arp. | |
867 | ||
868 | This technology is known by different names: | |
869 | In RFC 3069 it is called VLAN Aggregation. | |
870 | Cisco and Allied Telesyn call it Private VLAN. | |
871 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
872 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
873 | ||
1da177e4 LT |
874 | shared_media - BOOLEAN |
875 | Send(router) or accept(host) RFC1620 shared media redirects. | |
876 | Overrides ip_secure_redirects. | |
877 | shared_media for the interface will be enabled if at least one of | |
878 | conf/{all,interface}/shared_media is set to TRUE, | |
879 | it will be disabled otherwise | |
880 | default TRUE | |
881 | ||
882 | secure_redirects - BOOLEAN | |
883 | Accept ICMP redirect messages only for gateways, | |
884 | listed in default gateway list. | |
885 | secure_redirects for the interface will be enabled if at least one of | |
886 | conf/{all,interface}/secure_redirects is set to TRUE, | |
887 | it will be disabled otherwise | |
888 | default TRUE | |
889 | ||
890 | send_redirects - BOOLEAN | |
891 | Send redirects, if router. | |
892 | send_redirects for the interface will be enabled if at least one of | |
893 | conf/{all,interface}/send_redirects is set to TRUE, | |
894 | it will be disabled otherwise | |
895 | Default: TRUE | |
896 | ||
897 | bootp_relay - BOOLEAN | |
898 | Accept packets with source address 0.b.c.d destined | |
899 | not to this host as local ones. It is supposed, that | |
900 | BOOTP relay daemon will catch and forward such packets. | |
901 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
902 | for the interface | |
903 | default FALSE | |
904 | Not Implemented Yet. | |
905 | ||
906 | accept_source_route - BOOLEAN | |
907 | Accept packets with SRR option. | |
908 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
909 | with SRR option on the interface | |
910 | default TRUE (router) | |
911 | FALSE (host) | |
912 | ||
8153a10c | 913 | accept_local - BOOLEAN |
c801e3cc DM |
914 | Accept packets with local source addresses. In combination |
915 | with suitable routing, this can be used to direct packets | |
916 | between two local interfaces over the wire and have them | |
917 | accepted properly. | |
918 | ||
919 | rp_filter must be set to a non-zero value in order for | |
920 | accept_local to have an effect. | |
921 | ||
8153a10c PM |
922 | default FALSE |
923 | ||
d0daebc3 TG |
924 | route_localnet - BOOLEAN |
925 | Do not consider loopback addresses as martian source or destination | |
926 | while routing. This enables the use of 127/8 for local routing purposes. | |
927 | default FALSE | |
928 | ||
c1cf8422 | 929 | rp_filter - INTEGER |
1da177e4 | 930 | 0 - No source validation. |
c1cf8422 SH |
931 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
932 | Each incoming packet is tested against the FIB and if the interface | |
933 | is not the best reverse path the packet check will fail. | |
934 | By default failed packets are discarded. | |
935 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
936 | Each incoming packet's source address is also tested against the FIB | |
937 | and if the source address is not reachable via any interface | |
938 | the packet check will fail. | |
939 | ||
e18f5feb | 940 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 941 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 942 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 943 | |
1f5865e7 SW |
944 | The max value from conf/{all,interface}/rp_filter is used |
945 | when doing source validation on the {interface}. | |
1da177e4 LT |
946 | |
947 | Default value is 0. Note that some distributions enable it | |
948 | in startup scripts. | |
949 | ||
950 | arp_filter - BOOLEAN | |
951 | 1 - Allows you to have multiple network interfaces on the same | |
952 | subnet, and have the ARPs for each interface be answered | |
953 | based on whether or not the kernel would route a packet from | |
954 | the ARP'd IP out that interface (therefore you must use source | |
955 | based routing for this to work). In other words it allows control | |
956 | of which cards (usually 1) will respond to an arp request. | |
957 | ||
958 | 0 - (default) The kernel can respond to arp requests with addresses | |
959 | from other interfaces. This may seem wrong but it usually makes | |
960 | sense, because it increases the chance of successful communication. | |
961 | IP addresses are owned by the complete host on Linux, not by | |
962 | particular interfaces. Only for more complex setups like load- | |
963 | balancing, does this behaviour cause problems. | |
964 | ||
965 | arp_filter for the interface will be enabled if at least one of | |
966 | conf/{all,interface}/arp_filter is set to TRUE, | |
967 | it will be disabled otherwise | |
968 | ||
969 | arp_announce - INTEGER | |
970 | Define different restriction levels for announcing the local | |
971 | source IP address from IP packets in ARP requests sent on | |
972 | interface: | |
973 | 0 - (default) Use any local address, configured on any interface | |
974 | 1 - Try to avoid local addresses that are not in the target's | |
975 | subnet for this interface. This mode is useful when target | |
976 | hosts reachable via this interface require the source IP | |
977 | address in ARP requests to be part of their logical network | |
978 | configured on the receiving interface. When we generate the | |
979 | request we will check all our subnets that include the | |
980 | target IP and will preserve the source address if it is from | |
981 | such subnet. If there is no such subnet we select source | |
982 | address according to the rules for level 2. | |
983 | 2 - Always use the best local address for this target. | |
984 | In this mode we ignore the source address in the IP packet | |
985 | and try to select local address that we prefer for talks with | |
986 | the target host. Such local address is selected by looking | |
987 | for primary IP addresses on all our subnets on the outgoing | |
988 | interface that include the target IP address. If no suitable | |
989 | local address is found we select the first local address | |
990 | we have on the outgoing interface or on all other interfaces, | |
991 | with the hope we will receive reply for our request and | |
992 | even sometimes no matter the source IP address we announce. | |
993 | ||
994 | The max value from conf/{all,interface}/arp_announce is used. | |
995 | ||
996 | Increasing the restriction level gives more chance for | |
997 | receiving answer from the resolved target while decreasing | |
998 | the level announces more valid sender's information. | |
999 | ||
1000 | arp_ignore - INTEGER | |
1001 | Define different modes for sending replies in response to | |
1002 | received ARP requests that resolve local target IP addresses: | |
1003 | 0 - (default): reply for any local target IP address, configured | |
1004 | on any interface | |
1005 | 1 - reply only if the target IP address is local address | |
1006 | configured on the incoming interface | |
1007 | 2 - reply only if the target IP address is local address | |
1008 | configured on the incoming interface and both with the | |
1009 | sender's IP address are part from same subnet on this interface | |
1010 | 3 - do not reply for local addresses configured with scope host, | |
1011 | only resolutions for global and link addresses are replied | |
1012 | 4-7 - reserved | |
1013 | 8 - do not reply for all local addresses | |
1014 | ||
1015 | The max value from conf/{all,interface}/arp_ignore is used | |
1016 | when ARP request is received on the {interface} | |
1017 | ||
eefef1cf SH |
1018 | arp_notify - BOOLEAN |
1019 | Define mode for notification of address and device changes. | |
1020 | 0 - (default): do nothing | |
3f8dc236 | 1021 | 1 - Generate gratuitous arp requests when device is brought up |
eefef1cf SH |
1022 | or hardware address changes. |
1023 | ||
c1b1bce8 | 1024 | arp_accept - BOOLEAN |
6d955180 OP |
1025 | Define behavior for gratuitous ARP frames who's IP is not |
1026 | already present in the ARP table: | |
1027 | 0 - don't create new entries in the ARP table | |
1028 | 1 - create new entries in the ARP table | |
1029 | ||
1030 | Both replies and requests type gratuitous arp will trigger the | |
1031 | ARP table to be updated, if this setting is on. | |
1032 | ||
1033 | If the ARP table already contains the IP address of the | |
1034 | gratuitous arp frame, the arp table will be updated regardless | |
1035 | if this setting is on or off. | |
1036 | ||
c1b1bce8 | 1037 | |
1da177e4 LT |
1038 | app_solicit - INTEGER |
1039 | The maximum number of probes to send to the user space ARP daemon | |
1040 | via netlink before dropping back to multicast probes (see | |
1041 | mcast_solicit). Defaults to 0. | |
1042 | ||
1043 | disable_policy - BOOLEAN | |
1044 | Disable IPSEC policy (SPD) for this interface | |
1045 | ||
1046 | disable_xfrm - BOOLEAN | |
1047 | Disable IPSEC encryption on this interface, whatever the policy | |
1048 | ||
1049 | ||
1050 | ||
1051 | tag - INTEGER | |
1052 | Allows you to write a number, which can be used as required. | |
1053 | Default value is 0. | |
1054 | ||
1da177e4 LT |
1055 | Alexey Kuznetsov. |
1056 | kuznet@ms2.inr.ac.ru | |
1057 | ||
1058 | Updated by: | |
1059 | Andi Kleen | |
1060 | ak@muc.de | |
1061 | Nicolas Delon | |
1062 | delon.nicolas@wanadoo.fr | |
1063 | ||
1064 | ||
1065 | ||
1066 | ||
1067 | /proc/sys/net/ipv6/* Variables: | |
1068 | ||
1069 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1070 | apply to IPv6 [XXX?]. | |
1071 | ||
1072 | bindv6only - BOOLEAN | |
1073 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1074 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
1075 | only. |
1076 | TRUE: disable IPv4-mapped address feature | |
1077 | FALSE: enable IPv4-mapped address feature | |
1078 | ||
d5c073ca | 1079 | Default: FALSE (as specified in RFC3493) |
1da177e4 LT |
1080 | |
1081 | IPv6 Fragmentation: | |
1082 | ||
1083 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1084 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1085 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1086 | the fragment handler will toss packets until ip6frag_low_thresh | |
1087 | is reached. | |
e18f5feb | 1088 | |
1da177e4 | 1089 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1090 | See ip6frag_high_thresh |
1da177e4 LT |
1091 | |
1092 | ip6frag_time - INTEGER | |
1093 | Time in seconds to keep an IPv6 fragment in memory. | |
1094 | ||
1095 | ip6frag_secret_interval - INTEGER | |
e18f5feb | 1096 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
1097 | for the hash secret) for IPv6 fragments. |
1098 | Default: 600 | |
1099 | ||
1100 | conf/default/*: | |
1101 | Change the interface-specific default settings. | |
1102 | ||
1103 | ||
1104 | conf/all/*: | |
e18f5feb | 1105 | Change all the interface-specific settings. |
1da177e4 LT |
1106 | |
1107 | [XXX: Other special features than forwarding?] | |
1108 | ||
1109 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 1110 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 1111 | |
e18f5feb | 1112 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
1113 | to control which interfaces may forward packets and which not. |
1114 | ||
e18f5feb | 1115 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
1116 | 'forwarding' to the specified value. See below for details. |
1117 | ||
1118 | This referred to as global forwarding. | |
1119 | ||
fbea49e1 YH |
1120 | proxy_ndp - BOOLEAN |
1121 | Do proxy ndp. | |
1122 | ||
1da177e4 LT |
1123 | conf/interface/*: |
1124 | Change special settings per interface. | |
1125 | ||
e18f5feb | 1126 | The functional behaviour for certain settings is different |
1da177e4 LT |
1127 | depending on whether local forwarding is enabled or not. |
1128 | ||
605b91c8 | 1129 | accept_ra - INTEGER |
1da177e4 | 1130 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 1131 | |
026359bc TA |
1132 | It also determines whether or not to transmit Router |
1133 | Solicitations. If and only if the functional setting is to | |
1134 | accept Router Advertisements, Router Solicitations will be | |
1135 | transmitted. | |
1136 | ||
ae8abfa0 TG |
1137 | Possible values are: |
1138 | 0 Do not accept Router Advertisements. | |
1139 | 1 Accept Router Advertisements if forwarding is disabled. | |
1140 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1141 | even if forwarding is enabled. | |
1142 | ||
1da177e4 LT |
1143 | Functional default: enabled if local forwarding is disabled. |
1144 | disabled if local forwarding is enabled. | |
1145 | ||
65f5c7c1 YH |
1146 | accept_ra_defrtr - BOOLEAN |
1147 | Learn default router in Router Advertisement. | |
1148 | ||
1149 | Functional default: enabled if accept_ra is enabled. | |
1150 | disabled if accept_ra is disabled. | |
1151 | ||
c4fd30eb | 1152 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 1153 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
1154 | |
1155 | Functional default: enabled if accept_ra is enabled. | |
1156 | disabled if accept_ra is disabled. | |
1157 | ||
09c884d4 YH |
1158 | accept_ra_rt_info_max_plen - INTEGER |
1159 | Maximum prefix length of Route Information in RA. | |
1160 | ||
1161 | Route Information w/ prefix larger than or equal to this | |
1162 | variable shall be ignored. | |
1163 | ||
1164 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1165 | -1 if accept_ra_rtr_pref is disabled. | |
1166 | ||
930d6ff2 YH |
1167 | accept_ra_rtr_pref - BOOLEAN |
1168 | Accept Router Preference in RA. | |
1169 | ||
1170 | Functional default: enabled if accept_ra is enabled. | |
1171 | disabled if accept_ra is disabled. | |
1172 | ||
1da177e4 LT |
1173 | accept_redirects - BOOLEAN |
1174 | Accept Redirects. | |
1175 | ||
1176 | Functional default: enabled if local forwarding is disabled. | |
1177 | disabled if local forwarding is enabled. | |
1178 | ||
0bcbc926 YH |
1179 | accept_source_route - INTEGER |
1180 | Accept source routing (routing extension header). | |
1181 | ||
bb4dbf9e | 1182 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
1183 | < 0: Do not accept routing header. |
1184 | ||
1185 | Default: 0 | |
1186 | ||
1da177e4 | 1187 | autoconf - BOOLEAN |
e18f5feb | 1188 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
1189 | Advertisements. |
1190 | ||
c4fd30eb YH |
1191 | Functional default: enabled if accept_ra_pinfo is enabled. |
1192 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
1193 | |
1194 | dad_transmits - INTEGER | |
1195 | The amount of Duplicate Address Detection probes to send. | |
1196 | Default: 1 | |
e18f5feb | 1197 | |
605b91c8 | 1198 | forwarding - INTEGER |
e18f5feb | 1199 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 1200 | |
e18f5feb | 1201 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
1202 | interfaces; mixed router/host scenarios are rather uncommon. |
1203 | ||
ae8abfa0 TG |
1204 | Possible values are: |
1205 | 0 Forwarding disabled | |
1206 | 1 Forwarding enabled | |
ae8abfa0 TG |
1207 | |
1208 | FALSE (0): | |
1da177e4 LT |
1209 | |
1210 | By default, Host behaviour is assumed. This means: | |
1211 | ||
1212 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
1213 | 2. If accept_ra is TRUE (default), transmit Router |
1214 | Solicitations. | |
e18f5feb | 1215 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
1216 | Advertisements (and do autoconfiguration). |
1217 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1218 | ||
ae8abfa0 | 1219 | TRUE (1): |
1da177e4 | 1220 | |
e18f5feb | 1221 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
1222 | This means exactly the reverse from the above: |
1223 | ||
1224 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 1225 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 1226 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
1227 | 4. Redirects are ignored. |
1228 | ||
ae8abfa0 TG |
1229 | Default: 0 (disabled) if global forwarding is disabled (default), |
1230 | otherwise 1 (enabled). | |
1da177e4 LT |
1231 | |
1232 | hop_limit - INTEGER | |
1233 | Default Hop Limit to set. | |
1234 | Default: 64 | |
1235 | ||
1236 | mtu - INTEGER | |
1237 | Default Maximum Transfer Unit | |
1238 | Default: 1280 (IPv6 required minimum) | |
1239 | ||
52e16356 YH |
1240 | router_probe_interval - INTEGER |
1241 | Minimum interval (in seconds) between Router Probing described | |
1242 | in RFC4191. | |
1243 | ||
1244 | Default: 60 | |
1245 | ||
1da177e4 LT |
1246 | router_solicitation_delay - INTEGER |
1247 | Number of seconds to wait after interface is brought up | |
1248 | before sending Router Solicitations. | |
1249 | Default: 1 | |
1250 | ||
1251 | router_solicitation_interval - INTEGER | |
1252 | Number of seconds to wait between Router Solicitations. | |
1253 | Default: 4 | |
1254 | ||
1255 | router_solicitations - INTEGER | |
e18f5feb | 1256 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1257 | routers are present. |
1258 | Default: 3 | |
1259 | ||
1260 | use_tempaddr - INTEGER | |
1261 | Preference for Privacy Extensions (RFC3041). | |
1262 | <= 0 : disable Privacy Extensions | |
1263 | == 1 : enable Privacy Extensions, but prefer public | |
1264 | addresses over temporary addresses. | |
1265 | > 1 : enable Privacy Extensions and prefer temporary | |
1266 | addresses over public addresses. | |
1267 | Default: 0 (for most devices) | |
1268 | -1 (for point-to-point devices and loopback devices) | |
1269 | ||
1270 | temp_valid_lft - INTEGER | |
1271 | valid lifetime (in seconds) for temporary addresses. | |
1272 | Default: 604800 (7 days) | |
1273 | ||
1274 | temp_prefered_lft - INTEGER | |
1275 | Preferred lifetime (in seconds) for temporary addresses. | |
1276 | Default: 86400 (1 day) | |
1277 | ||
1278 | max_desync_factor - INTEGER | |
1279 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1280 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1281 | other and generate new addresses at exactly the same time. |
1282 | value is in seconds. | |
1283 | Default: 600 | |
e18f5feb | 1284 | |
1da177e4 LT |
1285 | regen_max_retry - INTEGER |
1286 | Number of attempts before give up attempting to generate | |
1287 | valid temporary addresses. | |
1288 | Default: 5 | |
1289 | ||
1290 | max_addresses - INTEGER | |
e79dc484 BH |
1291 | Maximum number of autoconfigured addresses per interface. Setting |
1292 | to zero disables the limitation. It is not recommended to set this | |
1293 | value too large (or to zero) because it would be an easy way to | |
1294 | crash the kernel by allowing too many addresses to be created. | |
1da177e4 LT |
1295 | Default: 16 |
1296 | ||
778d80be | 1297 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1298 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1299 | will be dynamically set to TRUE if DAD fails for the link-local | |
1300 | address. | |
778d80be YH |
1301 | Default: FALSE (enable IPv6 operation) |
1302 | ||
56d417b1 BH |
1303 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1304 | it will dynamically create a link-local address on the given | |
1305 | interface and start Duplicate Address Detection, if necessary. | |
1306 | ||
1307 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1308 | it will dynamically delete all address on the given interface. | |
1309 | ||
1b34be74 YH |
1310 | accept_dad - INTEGER |
1311 | Whether to accept DAD (Duplicate Address Detection). | |
1312 | 0: Disable DAD | |
1313 | 1: Enable DAD (default) | |
1314 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1315 | link-local address has been found. | |
1316 | ||
f7734fdf OP |
1317 | force_tllao - BOOLEAN |
1318 | Enable sending the target link-layer address option even when | |
1319 | responding to a unicast neighbor solicitation. | |
1320 | Default: FALSE | |
1321 | ||
1322 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1323 | ||
1324 | "The option MUST be included for multicast solicitations in order to | |
1325 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1326 | does not have a cache entry to return a Neighbor Advertisements | |
1327 | message. When responding to unicast solicitations, the option can be | |
1328 | omitted since the sender of the solicitation has the correct link- | |
1329 | layer address; otherwise it would not have be able to send the unicast | |
1330 | solicitation in the first place. However, including the link-layer | |
1331 | address in this case adds little overhead and eliminates a potential | |
1332 | race condition where the sender deletes the cached link-layer address | |
1333 | prior to receiving a response to a previous solicitation." | |
1334 | ||
1da177e4 LT |
1335 | icmp/*: |
1336 | ratelimit - INTEGER | |
1337 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1338 | 0 to disable any limiting, |
1339 | otherwise the minimal space between responses in milliseconds. | |
1340 | Default: 1000 | |
1da177e4 LT |
1341 | |
1342 | ||
1343 | IPv6 Update by: | |
1344 | Pekka Savola <pekkas@netcore.fi> | |
1345 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1346 | ||
1347 | ||
1348 | /proc/sys/net/bridge/* Variables: | |
1349 | ||
1350 | bridge-nf-call-arptables - BOOLEAN | |
1351 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1352 | 0 : disable this. | |
1353 | Default: 1 | |
1354 | ||
1355 | bridge-nf-call-iptables - BOOLEAN | |
1356 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1357 | 0 : disable this. | |
1358 | Default: 1 | |
1359 | ||
1360 | bridge-nf-call-ip6tables - BOOLEAN | |
1361 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1362 | 0 : disable this. | |
1363 | Default: 1 | |
1364 | ||
1365 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1366 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1367 | 0 : disable this. | |
4981682c | 1368 | Default: 0 |
516299d2 MM |
1369 | |
1370 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1371 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 | 1372 | 0 : disable this. |
4981682c | 1373 | Default: 0 |
1da177e4 | 1374 | |
4981682c PNA |
1375 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1376 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1377 | interface on the bridge and set the netfilter input device to the vlan. | |
1378 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1379 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1380 | vlan interface is found, or this switch is off, the input device is | |
1381 | set to the bridge interface. | |
1382 | 0: disable bridge netfilter vlan interface lookup. | |
1383 | Default: 0 | |
1da177e4 | 1384 | |
32e8d494 VY |
1385 | proc/sys/net/sctp/* Variables: |
1386 | ||
1387 | addip_enable - BOOLEAN | |
1388 | Enable or disable extension of Dynamic Address Reconfiguration | |
1389 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1390 | the ability to dynamically add and remove new addresses for the SCTP | |
1391 | associations. | |
1392 | ||
1393 | 1: Enable extension. | |
1394 | ||
1395 | 0: Disable extension. | |
1396 | ||
1397 | Default: 0 | |
1398 | ||
1399 | addip_noauth_enable - BOOLEAN | |
1400 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1401 | authentication to protect the operations of adding or removing new | |
1402 | addresses. This requirement is mandated so that unauthorized hosts | |
1403 | would not be able to hijack associations. However, older | |
1404 | implementations may not have implemented this requirement while | |
1405 | allowing the ADD-IP extension. For reasons of interoperability, | |
1406 | we provide this variable to control the enforcement of the | |
1407 | authentication requirement. | |
1408 | ||
1409 | 1: Allow ADD-IP extension to be used without authentication. This | |
1410 | should only be set in a closed environment for interoperability | |
1411 | with older implementations. | |
1412 | ||
1413 | 0: Enforce the authentication requirement | |
1414 | ||
1415 | Default: 0 | |
1416 | ||
1417 | auth_enable - BOOLEAN | |
1418 | Enable or disable Authenticated Chunks extension. This extension | |
1419 | provides the ability to send and receive authenticated chunks and is | |
1420 | required for secure operation of Dynamic Address Reconfiguration | |
1421 | (ADD-IP) extension. | |
1422 | ||
1423 | 1: Enable this extension. | |
1424 | 0: Disable this extension. | |
1425 | ||
1426 | Default: 0 | |
1427 | ||
1428 | prsctp_enable - BOOLEAN | |
1429 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1430 | is used to notify peers that a given DATA should no longer be expected. | |
1431 | ||
1432 | 1: Enable extension | |
1433 | 0: Disable | |
1434 | ||
1435 | Default: 1 | |
1436 | ||
1437 | max_burst - INTEGER | |
1438 | The limit of the number of new packets that can be initially sent. It | |
1439 | controls how bursty the generated traffic can be. | |
1440 | ||
1441 | Default: 4 | |
1442 | ||
1443 | association_max_retrans - INTEGER | |
1444 | Set the maximum number for retransmissions that an association can | |
1445 | attempt deciding that the remote end is unreachable. If this value | |
1446 | is exceeded, the association is terminated. | |
1447 | ||
1448 | Default: 10 | |
1449 | ||
1450 | max_init_retransmits - INTEGER | |
1451 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1452 | that an association will attempt before declaring the destination | |
1453 | unreachable and terminating. | |
1454 | ||
1455 | Default: 8 | |
1456 | ||
1457 | path_max_retrans - INTEGER | |
1458 | The maximum number of retransmissions that will be attempted on a given | |
1459 | path. Once this threshold is exceeded, the path is considered | |
1460 | unreachable, and new traffic will use a different path when the | |
1461 | association is multihomed. | |
1462 | ||
1463 | Default: 5 | |
1464 | ||
5aa93bcf NH |
1465 | pf_retrans - INTEGER |
1466 | The number of retransmissions that will be attempted on a given path | |
1467 | before traffic is redirected to an alternate transport (should one | |
1468 | exist). Note this is distinct from path_max_retrans, as a path that | |
1469 | passes the pf_retrans threshold can still be used. Its only | |
1470 | deprioritized when a transmission path is selected by the stack. This | |
1471 | setting is primarily used to enable fast failover mechanisms without | |
1472 | having to reduce path_max_retrans to a very low value. See: | |
1473 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
1474 | for details. Note also that a value of pf_retrans > path_max_retrans | |
1475 | disables this feature | |
1476 | ||
1477 | Default: 0 | |
1478 | ||
32e8d494 VY |
1479 | rto_initial - INTEGER |
1480 | The initial round trip timeout value in milliseconds that will be used | |
1481 | in calculating round trip times. This is the initial time interval | |
1482 | for retransmissions. | |
1483 | ||
1484 | Default: 3000 | |
1da177e4 | 1485 | |
32e8d494 VY |
1486 | rto_max - INTEGER |
1487 | The maximum value (in milliseconds) of the round trip timeout. This | |
1488 | is the largest time interval that can elapse between retransmissions. | |
1489 | ||
1490 | Default: 60000 | |
1491 | ||
1492 | rto_min - INTEGER | |
1493 | The minimum value (in milliseconds) of the round trip timeout. This | |
1494 | is the smallest time interval the can elapse between retransmissions. | |
1495 | ||
1496 | Default: 1000 | |
1497 | ||
1498 | hb_interval - INTEGER | |
1499 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1500 | are sent at the specified interval on idle paths to probe the state of | |
1501 | a given path between 2 associations. | |
1502 | ||
1503 | Default: 30000 | |
1504 | ||
1505 | sack_timeout - INTEGER | |
1506 | The amount of time (in milliseconds) that the implementation will wait | |
1507 | to send a SACK. | |
1508 | ||
1509 | Default: 200 | |
1510 | ||
1511 | valid_cookie_life - INTEGER | |
1512 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1513 | is used during association establishment. | |
1514 | ||
1515 | Default: 60000 | |
1516 | ||
1517 | cookie_preserve_enable - BOOLEAN | |
1518 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1519 | that is used during the establishment phase of SCTP association | |
1520 | ||
1521 | 1: Enable cookie lifetime extension. | |
1522 | 0: Disable | |
1523 | ||
1524 | Default: 1 | |
1525 | ||
3c68198e NH |
1526 | cookie_hmac_alg - STRING |
1527 | Select the hmac algorithm used when generating the cookie value sent by | |
1528 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
1529 | Valid values are: | |
1530 | * md5 | |
1531 | * sha1 | |
1532 | * none | |
1533 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
1534 | configuarion of those algorithms at build time (CONFIG_CRYPTO_MD5 and | |
1535 | CONFIG_CRYPTO_SHA1). | |
1536 | ||
1537 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
1538 | available, else none. | |
1539 | ||
32e8d494 VY |
1540 | rcvbuf_policy - INTEGER |
1541 | Determines if the receive buffer is attributed to the socket or to | |
1542 | association. SCTP supports the capability to create multiple | |
1543 | associations on a single socket. When using this capability, it is | |
1544 | possible that a single stalled association that's buffering a lot | |
1545 | of data may block other associations from delivering their data by | |
1546 | consuming all of the receive buffer space. To work around this, | |
1547 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1548 | to each association instead of the socket. This prevents the described | |
1549 | blocking. | |
1550 | ||
1551 | 1: rcvbuf space is per association | |
1552 | 0: recbuf space is per socket | |
1553 | ||
1554 | Default: 0 | |
1555 | ||
1556 | sndbuf_policy - INTEGER | |
1557 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1558 | ||
1559 | 1: Send buffer is tracked per association | |
1560 | 0: Send buffer is tracked per socket. | |
1561 | ||
1562 | Default: 0 | |
1563 | ||
1564 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1565 | Number of pages allowed for queueing by all SCTP sockets. | |
1566 | ||
1567 | min: Below this number of pages SCTP is not bothered about its | |
1568 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1569 | this number, SCTP starts to moderate memory usage. | |
1570 | ||
1571 | pressure: This value was introduced to follow format of tcp_mem. | |
1572 | ||
1573 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1574 | ||
1575 | Default is calculated at boot time from amount of available memory. | |
1576 | ||
1577 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
1578 | Only the first value ("min") is used, "default" and "max" are |
1579 | ignored. | |
1580 | ||
1581 | min: Minimal size of receive buffer used by SCTP socket. | |
1582 | It is guaranteed to each SCTP socket (but not association) even | |
1583 | under moderate memory pressure. | |
1584 | ||
1585 | Default: 1 page | |
32e8d494 VY |
1586 | |
1587 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b | 1588 | Currently this tunable has no effect. |
32e8d494 | 1589 | |
72388433 BD |
1590 | addr_scope_policy - INTEGER |
1591 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
1592 | ||
1593 | 0 - Disable IPv4 address scoping | |
1594 | 1 - Enable IPv4 address scoping | |
1595 | 2 - Follow draft but allow IPv4 private addresses | |
1596 | 3 - Follow draft but allow IPv4 link local addresses | |
1597 | ||
1598 | Default: 1 | |
1599 | ||
1da177e4 | 1600 | |
4edc2f34 | 1601 | /proc/sys/net/core/* |
c60f6aa8 | 1602 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. |
705efc3b | 1603 | |
4edc2f34 SH |
1604 | |
1605 | /proc/sys/net/unix/* | |
705efc3b WT |
1606 | max_dgram_qlen - INTEGER |
1607 | The maximum length of dgram socket receive queue | |
1608 | ||
1609 | Default: 10 | |
1610 | ||
1611 | ||
1612 | UNDOCUMENTED: | |
4edc2f34 SH |
1613 | |
1614 | /proc/sys/net/irda/* | |
1615 | fast_poll_increase FIXME | |
1616 | warn_noreply_time FIXME | |
1617 | discovery_slots FIXME | |
1618 | slot_timeout FIXME | |
1619 | max_baud_rate FIXME | |
1620 | discovery_timeout FIXME | |
1621 | lap_keepalive_time FIXME | |
1622 | max_noreply_time FIXME | |
1623 | max_tx_data_size FIXME | |
1624 | max_tx_window FIXME | |
1625 | min_tx_turn_time FIXME |