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Commit | Line | Data |
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1da177e4 LT |
1 | /proc/sys/net/ipv4/* Variables: |
2 | ||
3 | ip_forward - BOOLEAN | |
4 | 0 - disabled (default) | |
e18f5feb | 5 | not 0 - enabled |
1da177e4 LT |
6 | |
7 | Forward Packets between interfaces. | |
8 | ||
9 | This variable is special, its change resets all configuration | |
10 | parameters to their default state (RFC1122 for hosts, RFC1812 | |
11 | for routers) | |
12 | ||
13 | ip_default_ttl - INTEGER | |
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 | ||
2724680b YH |
29 | neigh/default/gc_thresh1 - INTEGER |
30 | Minimum number of entries to keep. Garbage collector will not | |
31 | purge entries if there are fewer than this number. | |
b66c66dc | 32 | Default: 128 |
2724680b | 33 | |
cbaf087a BG |
34 | neigh/default/gc_thresh3 - INTEGER |
35 | Maximum number of neighbor entries allowed. Increase this | |
36 | when using large numbers of interfaces and when communicating | |
37 | with large numbers of directly-connected peers. | |
cc868028 | 38 | Default: 1024 |
cbaf087a | 39 | |
8b5c171b ED |
40 | neigh/default/unres_qlen_bytes - INTEGER |
41 | The maximum number of bytes which may be used by packets | |
42 | queued for each unresolved address by other network layers. | |
43 | (added in linux 3.3) | |
3b09adcb | 44 | Setting negative value is meaningless and will return error. |
cc868028 | 45 | Default: 65536 Bytes(64KB) |
8b5c171b ED |
46 | |
47 | neigh/default/unres_qlen - INTEGER | |
48 | The maximum number of packets which may be queued for each | |
49 | unresolved address by other network layers. | |
50 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
cc868028 | 51 | Prior to linux 3.3, the default value is 3 which may cause |
5d248c49 | 52 | unexpected packet loss. The current default value is calculated |
cc868028 SW |
53 | according to default value of unres_qlen_bytes and true size of |
54 | packet. | |
55 | Default: 31 | |
8b5c171b | 56 | |
1da177e4 LT |
57 | mtu_expires - INTEGER |
58 | Time, in seconds, that cached PMTU information is kept. | |
59 | ||
60 | min_adv_mss - INTEGER | |
61 | The advertised MSS depends on the first hop route MTU, but will | |
62 | never be lower than this setting. | |
63 | ||
64 | IP Fragmentation: | |
65 | ||
66 | ipfrag_high_thresh - INTEGER | |
e18f5feb | 67 | Maximum memory used to reassemble IP fragments. When |
1da177e4 LT |
68 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
69 | the fragment handler will toss packets until ipfrag_low_thresh | |
70 | is reached. | |
e18f5feb | 71 | |
1da177e4 | 72 | ipfrag_low_thresh - INTEGER |
e18f5feb | 73 | See ipfrag_high_thresh |
1da177e4 LT |
74 | |
75 | ipfrag_time - INTEGER | |
e18f5feb | 76 | Time in seconds to keep an IP fragment in memory. |
1da177e4 LT |
77 | |
78 | ipfrag_secret_interval - INTEGER | |
e18f5feb | 79 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
80 | for the hash secret) for IP fragments. |
81 | Default: 600 | |
82 | ||
89cee8b1 | 83 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
84 | ipfrag_max_dist is a non-negative integer value which defines the |
85 | maximum "disorder" which is allowed among fragments which share a | |
86 | common IP source address. Note that reordering of packets is | |
87 | not unusual, but if a large number of fragments arrive from a source | |
88 | IP address while a particular fragment queue remains incomplete, it | |
89 | probably indicates that one or more fragments belonging to that queue | |
90 | have been lost. When ipfrag_max_dist is positive, an additional check | |
91 | is done on fragments before they are added to a reassembly queue - if | |
92 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
93 | address between additions to any IP fragment queue using that source | |
94 | address, it's presumed that one or more fragments in the queue are | |
95 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
96 | started. An ipfrag_max_dist value of zero disables this check. |
97 | ||
98 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
99 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
100 | reordering of packets occurs, which could lead to poor application |
101 | performance. Using a very large value, e.g. 50000, increases the | |
102 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
103 | from different IP datagrams, which could result in data corruption. |
104 | Default: 64 | |
105 | ||
1da177e4 LT |
106 | INET peer storage: |
107 | ||
108 | inet_peer_threshold - INTEGER | |
e18f5feb | 109 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
110 | entries will be thrown aggressively. This threshold also determines |
111 | entries' time-to-live and time intervals between garbage collection | |
112 | passes. More entries, less time-to-live, less GC interval. | |
113 | ||
114 | inet_peer_minttl - INTEGER | |
115 | Minimum time-to-live of entries. Should be enough to cover fragment | |
116 | time-to-live on the reassembling side. This minimum time-to-live is | |
117 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 118 | Measured in seconds. |
1da177e4 LT |
119 | |
120 | inet_peer_maxttl - INTEGER | |
121 | Maximum time-to-live of entries. Unused entries will expire after | |
122 | this period of time if there is no memory pressure on the pool (i.e. | |
123 | when the number of entries in the pool is very small). | |
77a538d5 | 124 | Measured in seconds. |
1da177e4 | 125 | |
e18f5feb | 126 | TCP variables: |
1da177e4 | 127 | |
ef56e622 SH |
128 | somaxconn - INTEGER |
129 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
130 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
131 | for TCP sockets. | |
132 | ||
ef56e622 SH |
133 | tcp_abort_on_overflow - BOOLEAN |
134 | If listening service is too slow to accept new connections, | |
135 | reset them. Default state is FALSE. It means that if overflow | |
136 | occurred due to a burst, connection will recover. Enable this | |
137 | option _only_ if you are really sure that listening daemon | |
138 | cannot be tuned to accept connections faster. Enabling this | |
139 | option can harm clients of your server. | |
1da177e4 | 140 | |
ef56e622 SH |
141 | tcp_adv_win_scale - INTEGER |
142 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
143 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
144 | if it is <= 0. | |
0147fc05 | 145 | Possible values are [-31, 31], inclusive. |
b49960a0 | 146 | Default: 1 |
1da177e4 | 147 | |
ef56e622 SH |
148 | tcp_allowed_congestion_control - STRING |
149 | Show/set the congestion control choices available to non-privileged | |
150 | processes. The list is a subset of those listed in | |
151 | tcp_available_congestion_control. | |
152 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 153 | |
ef56e622 SH |
154 | tcp_app_win - INTEGER |
155 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
156 | buffer. Value 0 is special, it means that nothing is reserved. | |
157 | Default: 31 | |
1da177e4 | 158 | |
ef56e622 SH |
159 | tcp_available_congestion_control - STRING |
160 | Shows the available congestion control choices that are registered. | |
161 | More congestion control algorithms may be available as modules, | |
162 | but not loaded. | |
1da177e4 | 163 | |
71599cd1 | 164 | tcp_base_mss - INTEGER |
4edc2f34 SH |
165 | The initial value of search_low to be used by the packetization layer |
166 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
167 | this is the initial MSS used by the connection. | |
71599cd1 | 168 | |
ef56e622 SH |
169 | tcp_congestion_control - STRING |
170 | Set the congestion control algorithm to be used for new | |
171 | connections. The algorithm "reno" is always available, but | |
172 | additional choices may be available based on kernel configuration. | |
173 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
174 | For passive connections, the listener congestion control choice |
175 | is inherited. | |
176 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
1da177e4 | 177 | |
ef56e622 SH |
178 | tcp_dsack - BOOLEAN |
179 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 180 | |
eed530b6 YC |
181 | tcp_early_retrans - INTEGER |
182 | Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold | |
183 | for triggering fast retransmit when the amount of outstanding data is | |
184 | small and when no previously unsent data can be transmitted (such | |
6ba8a3b1 | 185 | that limited transmit could be used). Also controls the use of |
3dd17ede | 186 | Tail loss probe (TLP) that converts RTOs occurring due to tail |
6ba8a3b1 | 187 | losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01). |
eed530b6 YC |
188 | Possible values: |
189 | 0 disables ER | |
190 | 1 enables ER | |
191 | 2 enables ER but delays fast recovery and fast retransmit | |
192 | by a fourth of RTT. This mitigates connection falsely | |
193 | recovers when network has a small degree of reordering | |
194 | (less than 3 packets). | |
6ba8a3b1 ND |
195 | 3 enables delayed ER and TLP. |
196 | 4 enables TLP only. | |
197 | Default: 3 | |
eed530b6 | 198 | |
34a6ef38 | 199 | tcp_ecn - INTEGER |
7e3a2dc5 RJ |
200 | Control use of Explicit Congestion Notification (ECN) by TCP. |
201 | ECN is used only when both ends of the TCP connection indicate | |
202 | support for it. This feature is useful in avoiding losses due | |
203 | to congestion by allowing supporting routers to signal | |
204 | congestion before having to drop packets. | |
255cac91 | 205 | Possible values are: |
7e3a2dc5 | 206 | 0 Disable ECN. Neither initiate nor accept ECN. |
3d55b323 VS |
207 | 1 Enable ECN when requested by incoming connections and |
208 | also request ECN on outgoing connection attempts. | |
209 | 2 Enable ECN when requested by incoming connections | |
7e3a2dc5 | 210 | but do not request ECN on outgoing connections. |
255cac91 | 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 | |
d825da2e RJ |
218 | The length of time an orphaned (no longer referenced by any |
219 | application) connection will remain in the FIN_WAIT_2 state | |
220 | before it is aborted at the local end. While a perfectly | |
221 | valid "receive only" state for an un-orphaned connection, an | |
222 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
223 | forever for the remote to close its end of the connection. | |
224 | Cf. tcp_max_orphans | |
225 | Default: 60 seconds | |
1da177e4 | 226 | |
89808060 | 227 | tcp_frto - INTEGER |
e33099f9 | 228 | Enables Forward RTO-Recovery (F-RTO) defined in RFC5682. |
cd99889c | 229 | F-RTO is an enhanced recovery algorithm for TCP retransmission |
e33099f9 YC |
230 | timeouts. It is particularly beneficial in networks where the |
231 | RTT fluctuates (e.g., wireless). F-RTO is sender-side only | |
232 | modification. It does not require any support from the peer. | |
233 | ||
234 | By default it's enabled with a non-zero value. 0 disables F-RTO. | |
1da177e4 | 235 | |
ef56e622 SH |
236 | tcp_keepalive_time - INTEGER |
237 | How often TCP sends out keepalive messages when keepalive is enabled. | |
238 | Default: 2hours. | |
1da177e4 | 239 | |
ef56e622 SH |
240 | tcp_keepalive_probes - INTEGER |
241 | How many keepalive probes TCP sends out, until it decides that the | |
242 | connection is broken. Default value: 9. | |
243 | ||
244 | tcp_keepalive_intvl - INTEGER | |
245 | How frequently the probes are send out. Multiplied by | |
246 | tcp_keepalive_probes it is time to kill not responding connection, | |
247 | after probes started. Default value: 75sec i.e. connection | |
248 | will be aborted after ~11 minutes of retries. | |
249 | ||
250 | tcp_low_latency - BOOLEAN | |
251 | If set, the TCP stack makes decisions that prefer lower | |
252 | latency as opposed to higher throughput. By default, this | |
253 | option is not set meaning that higher throughput is preferred. | |
254 | An example of an application where this default should be | |
255 | changed would be a Beowulf compute cluster. | |
256 | Default: 0 | |
1da177e4 LT |
257 | |
258 | tcp_max_orphans - INTEGER | |
259 | Maximal number of TCP sockets not attached to any user file handle, | |
260 | held by system. If this number is exceeded orphaned connections are | |
261 | reset immediately and warning is printed. This limit exists | |
262 | only to prevent simple DoS attacks, you _must_ not rely on this | |
263 | or lower the limit artificially, but rather increase it | |
264 | (probably, after increasing installed memory), | |
265 | if network conditions require more than default value, | |
266 | and tune network services to linger and kill such states | |
267 | more aggressively. Let me to remind again: each orphan eats | |
268 | up to ~64K of unswappable memory. | |
269 | ||
1da177e4 | 270 | tcp_max_syn_backlog - INTEGER |
99b53bdd PP |
271 | Maximal number of remembered connection requests, which have not |
272 | received an acknowledgment from connecting client. | |
273 | The minimal value is 128 for low memory machines, and it will | |
274 | increase in proportion to the memory of machine. | |
275 | If server suffers from overload, try increasing this number. | |
1da177e4 | 276 | |
ef56e622 SH |
277 | tcp_max_tw_buckets - INTEGER |
278 | Maximal number of timewait sockets held by system simultaneously. | |
279 | If this number is exceeded time-wait socket is immediately destroyed | |
280 | and warning is printed. This limit exists only to prevent | |
281 | simple DoS attacks, you _must_ not lower the limit artificially, | |
282 | but rather increase it (probably, after increasing installed memory), | |
283 | if network conditions require more than default value. | |
1da177e4 | 284 | |
ef56e622 SH |
285 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
286 | min: below this number of pages TCP is not bothered about its | |
287 | memory appetite. | |
1da177e4 | 288 | |
ef56e622 SH |
289 | pressure: when amount of memory allocated by TCP exceeds this number |
290 | of pages, TCP moderates its memory consumption and enters memory | |
291 | pressure mode, which is exited when memory consumption falls | |
292 | under "min". | |
1da177e4 | 293 | |
ef56e622 | 294 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 295 | |
ef56e622 SH |
296 | Defaults are calculated at boot time from amount of available |
297 | memory. | |
1da177e4 | 298 | |
71599cd1 | 299 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 300 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
301 | automatically size the buffer (no greater than tcp_rmem[2]) to |
302 | match the size required by the path for full throughput. Enabled by | |
303 | default. | |
304 | ||
305 | tcp_mtu_probing - INTEGER | |
306 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
307 | values: | |
308 | 0 - Disabled | |
309 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
310 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
311 | ||
312 | tcp_no_metrics_save - BOOLEAN | |
313 | By default, TCP saves various connection metrics in the route cache | |
314 | when the connection closes, so that connections established in the | |
315 | near future can use these to set initial conditions. Usually, this | |
316 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 317 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
318 | connections. |
319 | ||
ef56e622 | 320 | tcp_orphan_retries - INTEGER |
5d789229 DL |
321 | This value influences the timeout of a locally closed TCP connection, |
322 | when RTO retransmissions remain unacknowledged. | |
323 | See tcp_retries2 for more details. | |
324 | ||
06b8fc5d | 325 | The default value is 8. |
5d789229 | 326 | If your machine is a loaded WEB server, |
ef56e622 SH |
327 | you should think about lowering this value, such sockets |
328 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
329 | |
330 | tcp_reordering - INTEGER | |
331 | Maximal reordering of packets in a TCP stream. | |
e18f5feb | 332 | Default: 3 |
1da177e4 LT |
333 | |
334 | tcp_retrans_collapse - BOOLEAN | |
335 | Bug-to-bug compatibility with some broken printers. | |
336 | On retransmit try to send bigger packets to work around bugs in | |
337 | certain TCP stacks. | |
338 | ||
ef56e622 | 339 | tcp_retries1 - INTEGER |
5d789229 DL |
340 | This value influences the time, after which TCP decides, that |
341 | something is wrong due to unacknowledged RTO retransmissions, | |
342 | and reports this suspicion to the network layer. | |
343 | See tcp_retries2 for more details. | |
344 | ||
345 | RFC 1122 recommends at least 3 retransmissions, which is the | |
346 | default. | |
1da177e4 | 347 | |
ef56e622 | 348 | tcp_retries2 - INTEGER |
5d789229 DL |
349 | This value influences the timeout of an alive TCP connection, |
350 | when RTO retransmissions remain unacknowledged. | |
351 | Given a value of N, a hypothetical TCP connection following | |
352 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
353 | retransmit N times before killing the connection at the (N+1)th RTO. | |
354 | ||
355 | The default value of 15 yields a hypothetical timeout of 924.6 | |
356 | seconds and is a lower bound for the effective timeout. | |
357 | TCP will effectively time out at the first RTO which exceeds the | |
358 | hypothetical timeout. | |
359 | ||
360 | RFC 1122 recommends at least 100 seconds for the timeout, | |
361 | which corresponds to a value of at least 8. | |
1da177e4 | 362 | |
ef56e622 SH |
363 | tcp_rfc1337 - BOOLEAN |
364 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
365 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
366 | assassination. | |
367 | Default: 0 | |
1da177e4 LT |
368 | |
369 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
370 | min: Minimal size of receive buffer used by TCP sockets. | |
371 | It is guaranteed to each TCP socket, even under moderate memory | |
372 | pressure. | |
6539fefd | 373 | Default: 1 page |
1da177e4 | 374 | |
53025f5e | 375 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
376 | This value overrides net.core.rmem_default used by other protocols. |
377 | Default: 87380 bytes. This value results in window of 65535 with | |
378 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
379 | less for default tcp_app_win. See below about these variables. | |
380 | ||
381 | max: maximal size of receive buffer allowed for automatically | |
382 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
383 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
384 | automatic tuning of that socket's receive buffer size, in which | |
385 | case this value is ignored. | |
b49960a0 | 386 | Default: between 87380B and 6MB, depending on RAM size. |
1da177e4 | 387 | |
ef56e622 SH |
388 | tcp_sack - BOOLEAN |
389 | Enable select acknowledgments (SACKS). | |
1da177e4 | 390 | |
ef56e622 SH |
391 | tcp_slow_start_after_idle - BOOLEAN |
392 | If set, provide RFC2861 behavior and time out the congestion | |
393 | window after an idle period. An idle period is defined at | |
394 | the current RTO. If unset, the congestion window will not | |
395 | be timed out after an idle period. | |
396 | Default: 1 | |
1da177e4 | 397 | |
ef56e622 | 398 | tcp_stdurg - BOOLEAN |
4edc2f34 | 399 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
400 | Most hosts use the older BSD interpretation, so if you turn this on |
401 | Linux might not communicate correctly with them. | |
402 | Default: FALSE | |
1da177e4 | 403 | |
ef56e622 SH |
404 | tcp_synack_retries - INTEGER |
405 | Number of times SYNACKs for a passive TCP connection attempt will | |
406 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
407 | is 5, which corresponds to 31seconds till the last retransmission |
408 | with the current initial RTO of 1second. With this the final timeout | |
409 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 410 | |
ef56e622 | 411 | tcp_syncookies - BOOLEAN |
a3c910d2 | 412 | Only valid when the kernel was compiled with CONFIG_SYN_COOKIES |
ef56e622 | 413 | Send out syncookies when the syn backlog queue of a socket |
4edc2f34 | 414 | overflows. This is to prevent against the common 'SYN flood attack' |
a3c910d2 | 415 | Default: 1 |
1da177e4 | 416 | |
ef56e622 SH |
417 | Note, that syncookies is fallback facility. |
418 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 419 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
420 | in your logs, but investigation shows that they occur |
421 | because of overload with legal connections, you should tune | |
422 | another parameters until this warning disappear. | |
423 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 424 | |
ef56e622 SH |
425 | syncookies seriously violate TCP protocol, do not allow |
426 | to use TCP extensions, can result in serious degradation | |
427 | of some services (f.e. SMTP relaying), visible not by you, | |
428 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 429 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 430 | is seriously misconfigured. |
1da177e4 | 431 | |
5ad37d5d HFS |
432 | If you want to test which effects syncookies have to your |
433 | network connections you can set this knob to 2 to enable | |
434 | unconditionally generation of syncookies. | |
435 | ||
cf60af03 YC |
436 | tcp_fastopen - INTEGER |
437 | Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data | |
438 | in the opening SYN packet. To use this feature, the client application | |
10467163 JC |
439 | must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than |
440 | connect() to perform a TCP handshake automatically. | |
441 | ||
442 | The values (bitmap) are | |
0d41cca4 | 443 | 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN. |
10467163 JC |
444 | 2: Enables TCP Fast Open on the server side, i.e., allowing data in |
445 | a SYN packet to be accepted and passed to the application before | |
446 | 3-way hand shake finishes. | |
447 | 4: Send data in the opening SYN regardless of cookie availability and | |
448 | without a cookie option. | |
449 | 0x100: Accept SYN data w/o validating the cookie. | |
450 | 0x200: Accept data-in-SYN w/o any cookie option present. | |
451 | 0x400/0x800: Enable Fast Open on all listeners regardless of the | |
452 | TCP_FASTOPEN socket option. The two different flags designate two | |
453 | different ways of setting max_qlen without the TCP_FASTOPEN socket | |
454 | option. | |
cf60af03 | 455 | |
0d41cca4 | 456 | Default: 1 |
cf60af03 | 457 | |
10467163 JC |
458 | Note that the client & server side Fast Open flags (1 and 2 |
459 | respectively) must be also enabled before the rest of flags can take | |
460 | effect. | |
461 | ||
462 | See include/net/tcp.h and the code for more details. | |
463 | ||
ef56e622 SH |
464 | tcp_syn_retries - INTEGER |
465 | Number of times initial SYNs for an active TCP connection attempt | |
466 | will be retransmitted. Should not be higher than 255. Default value | |
3b09adcb | 467 | is 6, which corresponds to 63seconds till the last retransmission |
6c9ff979 AB |
468 | with the current initial RTO of 1second. With this the final timeout |
469 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 SH |
470 | |
471 | tcp_timestamps - BOOLEAN | |
472 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 473 | |
95bd09eb ED |
474 | tcp_min_tso_segs - INTEGER |
475 | Minimal number of segments per TSO frame. | |
476 | Since linux-3.12, TCP does an automatic sizing of TSO frames, | |
477 | depending on flow rate, instead of filling 64Kbytes packets. | |
478 | For specific usages, it's possible to force TCP to build big | |
479 | TSO frames. Note that TCP stack might split too big TSO packets | |
480 | if available window is too small. | |
481 | Default: 2 | |
482 | ||
1da177e4 | 483 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
484 | This allows control over what percentage of the congestion window |
485 | can be consumed by a single TSO frame. | |
486 | The setting of this parameter is a choice between burstiness and | |
487 | building larger TSO frames. | |
488 | Default: 3 | |
1da177e4 | 489 | |
ef56e622 SH |
490 | tcp_tw_recycle - BOOLEAN |
491 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
492 | It should not be changed without advice/request of technical | |
493 | experts. | |
1da177e4 | 494 | |
ef56e622 SH |
495 | tcp_tw_reuse - BOOLEAN |
496 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
497 | safe from protocol viewpoint. Default value is 0. | |
498 | It should not be changed without advice/request of technical | |
499 | experts. | |
ce7bc3bf | 500 | |
ef56e622 SH |
501 | tcp_window_scaling - BOOLEAN |
502 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 503 | |
ef56e622 | 504 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 505 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 506 | Each TCP socket has rights to use it due to fact of its birth. |
6539fefd | 507 | Default: 1 page |
9d7bcfc6 | 508 | |
53025f5e BF |
509 | default: initial size of send buffer used by TCP sockets. This |
510 | value overrides net.core.wmem_default used by other protocols. | |
511 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
512 | Default: 16K |
513 | ||
53025f5e BF |
514 | max: Maximal amount of memory allowed for automatically tuned |
515 | send buffers for TCP sockets. This value does not override | |
516 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
517 | automatic tuning of that socket's send buffer size, in which case | |
518 | this value is ignored. | |
519 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 520 | |
c9bee3b7 ED |
521 | tcp_notsent_lowat - UNSIGNED INTEGER |
522 | A TCP socket can control the amount of unsent bytes in its write queue, | |
523 | thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() | |
524 | reports POLLOUT events if the amount of unsent bytes is below a per | |
525 | socket value, and if the write queue is not full. sendmsg() will | |
526 | also not add new buffers if the limit is hit. | |
527 | ||
528 | This global variable controls the amount of unsent data for | |
529 | sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change | |
530 | to the global variable has immediate effect. | |
531 | ||
532 | Default: UINT_MAX (0xFFFFFFFF) | |
533 | ||
15d99e02 RJ |
534 | tcp_workaround_signed_windows - BOOLEAN |
535 | If set, assume no receipt of a window scaling option means the | |
536 | remote TCP is broken and treats the window as a signed quantity. | |
537 | If unset, assume the remote TCP is not broken even if we do | |
538 | not receive a window scaling option from them. | |
539 | Default: 0 | |
540 | ||
72d0b7a8 CL |
541 | tcp_dma_copybreak - INTEGER |
542 | Lower limit, in bytes, of the size of socket reads that will be | |
543 | offloaded to a DMA copy engine, if one is present in the system | |
544 | and CONFIG_NET_DMA is enabled. | |
545 | Default: 4096 | |
546 | ||
36e31b0a AP |
547 | tcp_thin_linear_timeouts - BOOLEAN |
548 | Enable dynamic triggering of linear timeouts for thin streams. | |
549 | If set, a check is performed upon retransmission by timeout to | |
550 | determine if the stream is thin (less than 4 packets in flight). | |
551 | As long as the stream is found to be thin, up to 6 linear | |
552 | timeouts may be performed before exponential backoff mode is | |
553 | initiated. This improves retransmission latency for | |
554 | non-aggressive thin streams, often found to be time-dependent. | |
555 | For more information on thin streams, see | |
556 | Documentation/networking/tcp-thin.txt | |
557 | Default: 0 | |
558 | ||
7e380175 AP |
559 | tcp_thin_dupack - BOOLEAN |
560 | Enable dynamic triggering of retransmissions after one dupACK | |
561 | for thin streams. If set, a check is performed upon reception | |
562 | of a dupACK to determine if the stream is thin (less than 4 | |
563 | packets in flight). As long as the stream is found to be thin, | |
564 | data is retransmitted on the first received dupACK. This | |
565 | improves retransmission latency for non-aggressive thin | |
566 | streams, often found to be time-dependent. | |
567 | For more information on thin streams, see | |
568 | Documentation/networking/tcp-thin.txt | |
569 | Default: 0 | |
570 | ||
46d3ceab ED |
571 | tcp_limit_output_bytes - INTEGER |
572 | Controls TCP Small Queue limit per tcp socket. | |
573 | TCP bulk sender tends to increase packets in flight until it | |
574 | gets losses notifications. With SNDBUF autotuning, this can | |
575 | result in a large amount of packets queued in qdisc/device | |
576 | on the local machine, hurting latency of other flows, for | |
577 | typical pfifo_fast qdiscs. | |
578 | tcp_limit_output_bytes limits the number of bytes on qdisc | |
579 | or device to reduce artificial RTT/cwnd and reduce bufferbloat. | |
46d3ceab ED |
580 | Default: 131072 |
581 | ||
282f23c6 ED |
582 | tcp_challenge_ack_limit - INTEGER |
583 | Limits number of Challenge ACK sent per second, as recommended | |
584 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
585 | Default: 100 | |
586 | ||
95766fff HA |
587 | UDP variables: |
588 | ||
589 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
590 | Number of pages allowed for queueing by all UDP sockets. | |
591 | ||
592 | min: Below this number of pages UDP is not bothered about its | |
593 | memory appetite. When amount of memory allocated by UDP exceeds | |
594 | this number, UDP starts to moderate memory usage. | |
595 | ||
596 | pressure: This value was introduced to follow format of tcp_mem. | |
597 | ||
598 | max: Number of pages allowed for queueing by all UDP sockets. | |
599 | ||
600 | Default is calculated at boot time from amount of available memory. | |
601 | ||
602 | udp_rmem_min - INTEGER | |
603 | Minimal size of receive buffer used by UDP sockets in moderation. | |
604 | Each UDP socket is able to use the size for receiving data, even if | |
605 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 606 | Default: 1 page |
95766fff HA |
607 | |
608 | udp_wmem_min - INTEGER | |
609 | Minimal size of send buffer used by UDP sockets in moderation. | |
610 | Each UDP socket is able to use the size for sending data, even if | |
611 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 612 | Default: 1 page |
95766fff | 613 | |
8802f616 PM |
614 | CIPSOv4 Variables: |
615 | ||
616 | cipso_cache_enable - BOOLEAN | |
617 | If set, enable additions to and lookups from the CIPSO label mapping | |
618 | cache. If unset, additions are ignored and lookups always result in a | |
619 | miss. However, regardless of the setting the cache is still | |
620 | invalidated when required when means you can safely toggle this on and | |
621 | off and the cache will always be "safe". | |
622 | Default: 1 | |
623 | ||
624 | cipso_cache_bucket_size - INTEGER | |
625 | The CIPSO label cache consists of a fixed size hash table with each | |
626 | hash bucket containing a number of cache entries. This variable limits | |
627 | the number of entries in each hash bucket; the larger the value the | |
628 | more CIPSO label mappings that can be cached. When the number of | |
629 | entries in a given hash bucket reaches this limit adding new entries | |
630 | causes the oldest entry in the bucket to be removed to make room. | |
631 | Default: 10 | |
632 | ||
633 | cipso_rbm_optfmt - BOOLEAN | |
634 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
635 | the CIPSO draft specification (see Documentation/netlabel for details). | |
636 | This means that when set the CIPSO tag will be padded with empty | |
637 | categories in order to make the packet data 32-bit aligned. | |
638 | Default: 0 | |
639 | ||
640 | cipso_rbm_structvalid - BOOLEAN | |
641 | If set, do a very strict check of the CIPSO option when | |
642 | ip_options_compile() is called. If unset, relax the checks done during | |
643 | ip_options_compile(). Either way is "safe" as errors are caught else | |
644 | where in the CIPSO processing code but setting this to 0 (False) should | |
645 | result in less work (i.e. it should be faster) but could cause problems | |
646 | with other implementations that require strict checking. | |
647 | Default: 0 | |
648 | ||
1da177e4 LT |
649 | IP Variables: |
650 | ||
651 | ip_local_port_range - 2 INTEGERS | |
652 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 653 | choose the local port. The first number is the first, the |
5d6bd861 FLVC |
654 | second the last local port number. The default values are |
655 | 32768 and 61000 respectively. | |
1da177e4 | 656 | |
e3826f1e AW |
657 | ip_local_reserved_ports - list of comma separated ranges |
658 | Specify the ports which are reserved for known third-party | |
659 | applications. These ports will not be used by automatic port | |
660 | assignments (e.g. when calling connect() or bind() with port | |
661 | number 0). Explicit port allocation behavior is unchanged. | |
662 | ||
663 | The format used for both input and output is a comma separated | |
664 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
665 | 10). Writing to the file will clear all previously reserved | |
666 | ports and update the current list with the one given in the | |
667 | input. | |
668 | ||
669 | Note that ip_local_port_range and ip_local_reserved_ports | |
670 | settings are independent and both are considered by the kernel | |
671 | when determining which ports are available for automatic port | |
672 | assignments. | |
673 | ||
674 | You can reserve ports which are not in the current | |
675 | ip_local_port_range, e.g.: | |
676 | ||
677 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
678 | 32000 61000 | |
679 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
680 | 8080,9148 | |
681 | ||
682 | although this is redundant. However such a setting is useful | |
683 | if later the port range is changed to a value that will | |
684 | include the reserved ports. | |
685 | ||
686 | Default: Empty | |
687 | ||
1da177e4 LT |
688 | ip_nonlocal_bind - BOOLEAN |
689 | If set, allows processes to bind() to non-local IP addresses, | |
690 | which can be quite useful - but may break some applications. | |
691 | Default: 0 | |
692 | ||
693 | ip_dynaddr - BOOLEAN | |
694 | If set non-zero, enables support for dynamic addresses. | |
695 | If set to a non-zero value larger than 1, a kernel log | |
696 | message will be printed when dynamic address rewriting | |
697 | occurs. | |
698 | Default: 0 | |
699 | ||
e3d73bce CW |
700 | ip_early_demux - BOOLEAN |
701 | Optimize input packet processing down to one demux for | |
702 | certain kinds of local sockets. Currently we only do this | |
703 | for established TCP sockets. | |
704 | ||
705 | It may add an additional cost for pure routing workloads that | |
706 | reduces overall throughput, in such case you should disable it. | |
707 | Default: 1 | |
708 | ||
1da177e4 | 709 | icmp_echo_ignore_all - BOOLEAN |
7ce31246 DM |
710 | If set non-zero, then the kernel will ignore all ICMP ECHO |
711 | requests sent to it. | |
712 | Default: 0 | |
713 | ||
1da177e4 | 714 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
715 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
716 | TIMESTAMP requests sent to it via broadcast/multicast. | |
717 | Default: 1 | |
1da177e4 LT |
718 | |
719 | icmp_ratelimit - INTEGER | |
720 | Limit the maximal rates for sending ICMP packets whose type matches | |
721 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
722 | 0 to disable any limiting, |
723 | otherwise the minimal space between responses in milliseconds. | |
724 | Default: 1000 | |
1da177e4 LT |
725 | |
726 | icmp_ratemask - INTEGER | |
727 | Mask made of ICMP types for which rates are being limited. | |
728 | Significant bits: IHGFEDCBA9876543210 | |
729 | Default mask: 0000001100000011000 (6168) | |
730 | ||
731 | Bit definitions (see include/linux/icmp.h): | |
732 | 0 Echo Reply | |
733 | 3 Destination Unreachable * | |
734 | 4 Source Quench * | |
735 | 5 Redirect | |
736 | 8 Echo Request | |
737 | B Time Exceeded * | |
738 | C Parameter Problem * | |
739 | D Timestamp Request | |
740 | E Timestamp Reply | |
741 | F Info Request | |
742 | G Info Reply | |
743 | H Address Mask Request | |
744 | I Address Mask Reply | |
745 | ||
746 | * These are rate limited by default (see default mask above) | |
747 | ||
748 | icmp_ignore_bogus_error_responses - BOOLEAN | |
749 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
750 | frames. Such violations are normally logged via a kernel warning. | |
751 | If this is set to TRUE, the kernel will not give such warnings, which | |
752 | will avoid log file clutter. | |
e8b265e8 | 753 | Default: 1 |
1da177e4 | 754 | |
95f7daf1 H |
755 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
756 | ||
757 | If zero, icmp error messages are sent with the primary address of | |
758 | the exiting interface. | |
e18f5feb | 759 | |
95f7daf1 H |
760 | If non-zero, the message will be sent with the primary address of |
761 | the interface that received the packet that caused the icmp error. | |
762 | This is the behaviour network many administrators will expect from | |
763 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 764 | much easier. |
95f7daf1 H |
765 | |
766 | Note that if no primary address exists for the interface selected, | |
767 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 768 | has one will be used regardless of this setting. |
95f7daf1 H |
769 | |
770 | Default: 0 | |
771 | ||
1da177e4 LT |
772 | igmp_max_memberships - INTEGER |
773 | Change the maximum number of multicast groups we can subscribe to. | |
774 | Default: 20 | |
775 | ||
d67ef35f JE |
776 | Theoretical maximum value is bounded by having to send a membership |
777 | report in a single datagram (i.e. the report can't span multiple | |
778 | datagrams, or risk confusing the switch and leaving groups you don't | |
779 | intend to). | |
1da177e4 | 780 | |
d67ef35f JE |
781 | The number of supported groups 'M' is bounded by the number of group |
782 | report entries you can fit into a single datagram of 65535 bytes. | |
783 | ||
784 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
785 | ||
786 | Group records are variable length, with a minimum of 12 bytes. | |
787 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
788 | ||
789 | (65536-24) / 12 = 5459 | |
790 | ||
791 | The value 5459 assumes no IP header options, so in practice | |
792 | this number may be lower. | |
793 | ||
794 | conf/interface/* changes special settings per interface (where | |
795 | "interface" is the name of your network interface) | |
796 | ||
797 | conf/all/* is special, changes the settings for all interfaces | |
1da177e4 LT |
798 | |
799 | log_martians - BOOLEAN | |
800 | Log packets with impossible addresses to kernel log. | |
801 | log_martians for the interface will be enabled if at least one of | |
802 | conf/{all,interface}/log_martians is set to TRUE, | |
803 | it will be disabled otherwise | |
804 | ||
805 | accept_redirects - BOOLEAN | |
806 | Accept ICMP redirect messages. | |
807 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
808 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
809 | forwarding for the interface is enabled | |
1da177e4 | 810 | or |
e18f5feb JDB |
811 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
812 | case forwarding for the interface is disabled | |
1da177e4 LT |
813 | accept_redirects for the interface will be disabled otherwise |
814 | default TRUE (host) | |
815 | FALSE (router) | |
816 | ||
817 | forwarding - BOOLEAN | |
818 | Enable IP forwarding on this interface. | |
819 | ||
820 | mc_forwarding - BOOLEAN | |
821 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
822 | and a multicast routing daemon is required. | |
e18f5feb JDB |
823 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
824 | routing for the interface | |
1da177e4 LT |
825 | |
826 | medium_id - INTEGER | |
827 | Integer value used to differentiate the devices by the medium they | |
828 | are attached to. Two devices can have different id values when | |
829 | the broadcast packets are received only on one of them. | |
830 | The default value 0 means that the device is the only interface | |
831 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 832 | |
1da177e4 LT |
833 | Currently, it is used to change the proxy_arp behavior: |
834 | the proxy_arp feature is enabled for packets forwarded between | |
835 | two devices attached to different media. | |
836 | ||
837 | proxy_arp - BOOLEAN | |
838 | Do proxy arp. | |
839 | proxy_arp for the interface will be enabled if at least one of | |
840 | conf/{all,interface}/proxy_arp is set to TRUE, | |
841 | it will be disabled otherwise | |
842 | ||
65324144 JDB |
843 | proxy_arp_pvlan - BOOLEAN |
844 | Private VLAN proxy arp. | |
845 | Basically allow proxy arp replies back to the same interface | |
846 | (from which the ARP request/solicitation was received). | |
847 | ||
848 | This is done to support (ethernet) switch features, like RFC | |
849 | 3069, where the individual ports are NOT allowed to | |
850 | communicate with each other, but they are allowed to talk to | |
851 | the upstream router. As described in RFC 3069, it is possible | |
852 | to allow these hosts to communicate through the upstream | |
853 | router by proxy_arp'ing. Don't need to be used together with | |
854 | proxy_arp. | |
855 | ||
856 | This technology is known by different names: | |
857 | In RFC 3069 it is called VLAN Aggregation. | |
858 | Cisco and Allied Telesyn call it Private VLAN. | |
859 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
860 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
861 | ||
1da177e4 LT |
862 | shared_media - BOOLEAN |
863 | Send(router) or accept(host) RFC1620 shared media redirects. | |
864 | Overrides ip_secure_redirects. | |
865 | shared_media for the interface will be enabled if at least one of | |
866 | conf/{all,interface}/shared_media is set to TRUE, | |
867 | it will be disabled otherwise | |
868 | default TRUE | |
869 | ||
870 | secure_redirects - BOOLEAN | |
871 | Accept ICMP redirect messages only for gateways, | |
872 | listed in default gateway list. | |
873 | secure_redirects for the interface will be enabled if at least one of | |
874 | conf/{all,interface}/secure_redirects is set to TRUE, | |
875 | it will be disabled otherwise | |
876 | default TRUE | |
877 | ||
878 | send_redirects - BOOLEAN | |
879 | Send redirects, if router. | |
880 | send_redirects for the interface will be enabled if at least one of | |
881 | conf/{all,interface}/send_redirects is set to TRUE, | |
882 | it will be disabled otherwise | |
883 | Default: TRUE | |
884 | ||
885 | bootp_relay - BOOLEAN | |
886 | Accept packets with source address 0.b.c.d destined | |
887 | not to this host as local ones. It is supposed, that | |
888 | BOOTP relay daemon will catch and forward such packets. | |
889 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
890 | for the interface | |
891 | default FALSE | |
892 | Not Implemented Yet. | |
893 | ||
894 | accept_source_route - BOOLEAN | |
895 | Accept packets with SRR option. | |
896 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
897 | with SRR option on the interface | |
898 | default TRUE (router) | |
899 | FALSE (host) | |
900 | ||
8153a10c | 901 | accept_local - BOOLEAN |
c801e3cc DM |
902 | Accept packets with local source addresses. In combination |
903 | with suitable routing, this can be used to direct packets | |
904 | between two local interfaces over the wire and have them | |
905 | accepted properly. | |
906 | ||
907 | rp_filter must be set to a non-zero value in order for | |
908 | accept_local to have an effect. | |
909 | ||
8153a10c PM |
910 | default FALSE |
911 | ||
d0daebc3 TG |
912 | route_localnet - BOOLEAN |
913 | Do not consider loopback addresses as martian source or destination | |
914 | while routing. This enables the use of 127/8 for local routing purposes. | |
915 | default FALSE | |
916 | ||
c1cf8422 | 917 | rp_filter - INTEGER |
1da177e4 | 918 | 0 - No source validation. |
c1cf8422 SH |
919 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
920 | Each incoming packet is tested against the FIB and if the interface | |
921 | is not the best reverse path the packet check will fail. | |
922 | By default failed packets are discarded. | |
923 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
924 | Each incoming packet's source address is also tested against the FIB | |
925 | and if the source address is not reachable via any interface | |
926 | the packet check will fail. | |
927 | ||
e18f5feb | 928 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 929 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 930 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 931 | |
1f5865e7 SW |
932 | The max value from conf/{all,interface}/rp_filter is used |
933 | when doing source validation on the {interface}. | |
1da177e4 LT |
934 | |
935 | Default value is 0. Note that some distributions enable it | |
936 | in startup scripts. | |
937 | ||
938 | arp_filter - BOOLEAN | |
939 | 1 - Allows you to have multiple network interfaces on the same | |
940 | subnet, and have the ARPs for each interface be answered | |
941 | based on whether or not the kernel would route a packet from | |
942 | the ARP'd IP out that interface (therefore you must use source | |
943 | based routing for this to work). In other words it allows control | |
944 | of which cards (usually 1) will respond to an arp request. | |
945 | ||
946 | 0 - (default) The kernel can respond to arp requests with addresses | |
947 | from other interfaces. This may seem wrong but it usually makes | |
948 | sense, because it increases the chance of successful communication. | |
949 | IP addresses are owned by the complete host on Linux, not by | |
950 | particular interfaces. Only for more complex setups like load- | |
951 | balancing, does this behaviour cause problems. | |
952 | ||
953 | arp_filter for the interface will be enabled if at least one of | |
954 | conf/{all,interface}/arp_filter is set to TRUE, | |
955 | it will be disabled otherwise | |
956 | ||
957 | arp_announce - INTEGER | |
958 | Define different restriction levels for announcing the local | |
959 | source IP address from IP packets in ARP requests sent on | |
960 | interface: | |
961 | 0 - (default) Use any local address, configured on any interface | |
962 | 1 - Try to avoid local addresses that are not in the target's | |
963 | subnet for this interface. This mode is useful when target | |
964 | hosts reachable via this interface require the source IP | |
965 | address in ARP requests to be part of their logical network | |
966 | configured on the receiving interface. When we generate the | |
967 | request we will check all our subnets that include the | |
968 | target IP and will preserve the source address if it is from | |
969 | such subnet. If there is no such subnet we select source | |
970 | address according to the rules for level 2. | |
971 | 2 - Always use the best local address for this target. | |
972 | In this mode we ignore the source address in the IP packet | |
973 | and try to select local address that we prefer for talks with | |
974 | the target host. Such local address is selected by looking | |
975 | for primary IP addresses on all our subnets on the outgoing | |
976 | interface that include the target IP address. If no suitable | |
977 | local address is found we select the first local address | |
978 | we have on the outgoing interface or on all other interfaces, | |
979 | with the hope we will receive reply for our request and | |
980 | even sometimes no matter the source IP address we announce. | |
981 | ||
982 | The max value from conf/{all,interface}/arp_announce is used. | |
983 | ||
984 | Increasing the restriction level gives more chance for | |
985 | receiving answer from the resolved target while decreasing | |
986 | the level announces more valid sender's information. | |
987 | ||
988 | arp_ignore - INTEGER | |
989 | Define different modes for sending replies in response to | |
990 | received ARP requests that resolve local target IP addresses: | |
991 | 0 - (default): reply for any local target IP address, configured | |
992 | on any interface | |
993 | 1 - reply only if the target IP address is local address | |
994 | configured on the incoming interface | |
995 | 2 - reply only if the target IP address is local address | |
996 | configured on the incoming interface and both with the | |
997 | sender's IP address are part from same subnet on this interface | |
998 | 3 - do not reply for local addresses configured with scope host, | |
999 | only resolutions for global and link addresses are replied | |
1000 | 4-7 - reserved | |
1001 | 8 - do not reply for all local addresses | |
1002 | ||
1003 | The max value from conf/{all,interface}/arp_ignore is used | |
1004 | when ARP request is received on the {interface} | |
1005 | ||
eefef1cf SH |
1006 | arp_notify - BOOLEAN |
1007 | Define mode for notification of address and device changes. | |
1008 | 0 - (default): do nothing | |
3f8dc236 | 1009 | 1 - Generate gratuitous arp requests when device is brought up |
eefef1cf SH |
1010 | or hardware address changes. |
1011 | ||
c1b1bce8 | 1012 | arp_accept - BOOLEAN |
6d955180 OP |
1013 | Define behavior for gratuitous ARP frames who's IP is not |
1014 | already present in the ARP table: | |
1015 | 0 - don't create new entries in the ARP table | |
1016 | 1 - create new entries in the ARP table | |
1017 | ||
1018 | Both replies and requests type gratuitous arp will trigger the | |
1019 | ARP table to be updated, if this setting is on. | |
1020 | ||
1021 | If the ARP table already contains the IP address of the | |
1022 | gratuitous arp frame, the arp table will be updated regardless | |
1023 | if this setting is on or off. | |
1024 | ||
c1b1bce8 | 1025 | |
1da177e4 LT |
1026 | app_solicit - INTEGER |
1027 | The maximum number of probes to send to the user space ARP daemon | |
1028 | via netlink before dropping back to multicast probes (see | |
1029 | mcast_solicit). Defaults to 0. | |
1030 | ||
1031 | disable_policy - BOOLEAN | |
1032 | Disable IPSEC policy (SPD) for this interface | |
1033 | ||
1034 | disable_xfrm - BOOLEAN | |
1035 | Disable IPSEC encryption on this interface, whatever the policy | |
1036 | ||
fc4eba58 HFS |
1037 | igmpv2_unsolicited_report_interval - INTEGER |
1038 | The interval in milliseconds in which the next unsolicited | |
1039 | IGMPv1 or IGMPv2 report retransmit will take place. | |
1040 | Default: 10000 (10 seconds) | |
1da177e4 | 1041 | |
fc4eba58 HFS |
1042 | igmpv3_unsolicited_report_interval - INTEGER |
1043 | The interval in milliseconds in which the next unsolicited | |
1044 | IGMPv3 report retransmit will take place. | |
1045 | Default: 1000 (1 seconds) | |
1da177e4 LT |
1046 | |
1047 | tag - INTEGER | |
1048 | Allows you to write a number, which can be used as required. | |
1049 | Default value is 0. | |
1050 | ||
1da177e4 LT |
1051 | Alexey Kuznetsov. |
1052 | kuznet@ms2.inr.ac.ru | |
1053 | ||
1054 | Updated by: | |
1055 | Andi Kleen | |
1056 | ak@muc.de | |
1057 | Nicolas Delon | |
1058 | delon.nicolas@wanadoo.fr | |
1059 | ||
1060 | ||
1061 | ||
1062 | ||
1063 | /proc/sys/net/ipv6/* Variables: | |
1064 | ||
1065 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1066 | apply to IPv6 [XXX?]. | |
1067 | ||
1068 | bindv6only - BOOLEAN | |
1069 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1070 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
1071 | only. |
1072 | TRUE: disable IPv4-mapped address feature | |
1073 | FALSE: enable IPv4-mapped address feature | |
1074 | ||
d5c073ca | 1075 | Default: FALSE (as specified in RFC3493) |
1da177e4 LT |
1076 | |
1077 | IPv6 Fragmentation: | |
1078 | ||
1079 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1080 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1081 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1082 | the fragment handler will toss packets until ip6frag_low_thresh | |
1083 | is reached. | |
e18f5feb | 1084 | |
1da177e4 | 1085 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1086 | See ip6frag_high_thresh |
1da177e4 LT |
1087 | |
1088 | ip6frag_time - INTEGER | |
1089 | Time in seconds to keep an IPv6 fragment in memory. | |
1090 | ||
1091 | ip6frag_secret_interval - INTEGER | |
e18f5feb | 1092 | Regeneration interval (in seconds) of the hash secret (or lifetime |
1da177e4 LT |
1093 | for the hash secret) for IPv6 fragments. |
1094 | Default: 600 | |
1095 | ||
1096 | conf/default/*: | |
1097 | Change the interface-specific default settings. | |
1098 | ||
1099 | ||
1100 | conf/all/*: | |
e18f5feb | 1101 | Change all the interface-specific settings. |
1da177e4 LT |
1102 | |
1103 | [XXX: Other special features than forwarding?] | |
1104 | ||
1105 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 1106 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 1107 | |
e18f5feb | 1108 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
1109 | to control which interfaces may forward packets and which not. |
1110 | ||
e18f5feb | 1111 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
1112 | 'forwarding' to the specified value. See below for details. |
1113 | ||
1114 | This referred to as global forwarding. | |
1115 | ||
fbea49e1 YH |
1116 | proxy_ndp - BOOLEAN |
1117 | Do proxy ndp. | |
1118 | ||
1da177e4 LT |
1119 | conf/interface/*: |
1120 | Change special settings per interface. | |
1121 | ||
e18f5feb | 1122 | The functional behaviour for certain settings is different |
1da177e4 LT |
1123 | depending on whether local forwarding is enabled or not. |
1124 | ||
605b91c8 | 1125 | accept_ra - INTEGER |
1da177e4 | 1126 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 1127 | |
026359bc TA |
1128 | It also determines whether or not to transmit Router |
1129 | Solicitations. If and only if the functional setting is to | |
1130 | accept Router Advertisements, Router Solicitations will be | |
1131 | transmitted. | |
1132 | ||
ae8abfa0 TG |
1133 | Possible values are: |
1134 | 0 Do not accept Router Advertisements. | |
1135 | 1 Accept Router Advertisements if forwarding is disabled. | |
1136 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1137 | even if forwarding is enabled. | |
1138 | ||
1da177e4 LT |
1139 | Functional default: enabled if local forwarding is disabled. |
1140 | disabled if local forwarding is enabled. | |
1141 | ||
65f5c7c1 YH |
1142 | accept_ra_defrtr - BOOLEAN |
1143 | Learn default router in Router Advertisement. | |
1144 | ||
1145 | Functional default: enabled if accept_ra is enabled. | |
1146 | disabled if accept_ra is disabled. | |
1147 | ||
c4fd30eb | 1148 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 1149 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
1150 | |
1151 | Functional default: enabled if accept_ra is enabled. | |
1152 | disabled if accept_ra is disabled. | |
1153 | ||
09c884d4 YH |
1154 | accept_ra_rt_info_max_plen - INTEGER |
1155 | Maximum prefix length of Route Information in RA. | |
1156 | ||
1157 | Route Information w/ prefix larger than or equal to this | |
1158 | variable shall be ignored. | |
1159 | ||
1160 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1161 | -1 if accept_ra_rtr_pref is disabled. | |
1162 | ||
930d6ff2 YH |
1163 | accept_ra_rtr_pref - BOOLEAN |
1164 | Accept Router Preference in RA. | |
1165 | ||
1166 | Functional default: enabled if accept_ra is enabled. | |
1167 | disabled if accept_ra is disabled. | |
1168 | ||
1da177e4 LT |
1169 | accept_redirects - BOOLEAN |
1170 | Accept Redirects. | |
1171 | ||
1172 | Functional default: enabled if local forwarding is disabled. | |
1173 | disabled if local forwarding is enabled. | |
1174 | ||
0bcbc926 YH |
1175 | accept_source_route - INTEGER |
1176 | Accept source routing (routing extension header). | |
1177 | ||
bb4dbf9e | 1178 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
1179 | < 0: Do not accept routing header. |
1180 | ||
1181 | Default: 0 | |
1182 | ||
1da177e4 | 1183 | autoconf - BOOLEAN |
e18f5feb | 1184 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
1185 | Advertisements. |
1186 | ||
c4fd30eb YH |
1187 | Functional default: enabled if accept_ra_pinfo is enabled. |
1188 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
1189 | |
1190 | dad_transmits - INTEGER | |
1191 | The amount of Duplicate Address Detection probes to send. | |
1192 | Default: 1 | |
e18f5feb | 1193 | |
605b91c8 | 1194 | forwarding - INTEGER |
e18f5feb | 1195 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 1196 | |
e18f5feb | 1197 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
1198 | interfaces; mixed router/host scenarios are rather uncommon. |
1199 | ||
ae8abfa0 TG |
1200 | Possible values are: |
1201 | 0 Forwarding disabled | |
1202 | 1 Forwarding enabled | |
ae8abfa0 TG |
1203 | |
1204 | FALSE (0): | |
1da177e4 LT |
1205 | |
1206 | By default, Host behaviour is assumed. This means: | |
1207 | ||
1208 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
1209 | 2. If accept_ra is TRUE (default), transmit Router |
1210 | Solicitations. | |
e18f5feb | 1211 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
1212 | Advertisements (and do autoconfiguration). |
1213 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1214 | ||
ae8abfa0 | 1215 | TRUE (1): |
1da177e4 | 1216 | |
e18f5feb | 1217 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
1218 | This means exactly the reverse from the above: |
1219 | ||
1220 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 1221 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 1222 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
1223 | 4. Redirects are ignored. |
1224 | ||
ae8abfa0 TG |
1225 | Default: 0 (disabled) if global forwarding is disabled (default), |
1226 | otherwise 1 (enabled). | |
1da177e4 LT |
1227 | |
1228 | hop_limit - INTEGER | |
1229 | Default Hop Limit to set. | |
1230 | Default: 64 | |
1231 | ||
1232 | mtu - INTEGER | |
1233 | Default Maximum Transfer Unit | |
1234 | Default: 1280 (IPv6 required minimum) | |
1235 | ||
52e16356 YH |
1236 | router_probe_interval - INTEGER |
1237 | Minimum interval (in seconds) between Router Probing described | |
1238 | in RFC4191. | |
1239 | ||
1240 | Default: 60 | |
1241 | ||
1da177e4 LT |
1242 | router_solicitation_delay - INTEGER |
1243 | Number of seconds to wait after interface is brought up | |
1244 | before sending Router Solicitations. | |
1245 | Default: 1 | |
1246 | ||
1247 | router_solicitation_interval - INTEGER | |
1248 | Number of seconds to wait between Router Solicitations. | |
1249 | Default: 4 | |
1250 | ||
1251 | router_solicitations - INTEGER | |
e18f5feb | 1252 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1253 | routers are present. |
1254 | Default: 3 | |
1255 | ||
1256 | use_tempaddr - INTEGER | |
1257 | Preference for Privacy Extensions (RFC3041). | |
1258 | <= 0 : disable Privacy Extensions | |
1259 | == 1 : enable Privacy Extensions, but prefer public | |
1260 | addresses over temporary addresses. | |
1261 | > 1 : enable Privacy Extensions and prefer temporary | |
1262 | addresses over public addresses. | |
1263 | Default: 0 (for most devices) | |
1264 | -1 (for point-to-point devices and loopback devices) | |
1265 | ||
1266 | temp_valid_lft - INTEGER | |
1267 | valid lifetime (in seconds) for temporary addresses. | |
1268 | Default: 604800 (7 days) | |
1269 | ||
1270 | temp_prefered_lft - INTEGER | |
1271 | Preferred lifetime (in seconds) for temporary addresses. | |
1272 | Default: 86400 (1 day) | |
1273 | ||
1274 | max_desync_factor - INTEGER | |
1275 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1276 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1277 | other and generate new addresses at exactly the same time. |
1278 | value is in seconds. | |
1279 | Default: 600 | |
e18f5feb | 1280 | |
1da177e4 LT |
1281 | regen_max_retry - INTEGER |
1282 | Number of attempts before give up attempting to generate | |
1283 | valid temporary addresses. | |
1284 | Default: 5 | |
1285 | ||
1286 | max_addresses - INTEGER | |
e79dc484 BH |
1287 | Maximum number of autoconfigured addresses per interface. Setting |
1288 | to zero disables the limitation. It is not recommended to set this | |
1289 | value too large (or to zero) because it would be an easy way to | |
1290 | crash the kernel by allowing too many addresses to be created. | |
1da177e4 LT |
1291 | Default: 16 |
1292 | ||
778d80be | 1293 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1294 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1295 | will be dynamically set to TRUE if DAD fails for the link-local | |
1296 | address. | |
778d80be YH |
1297 | Default: FALSE (enable IPv6 operation) |
1298 | ||
56d417b1 BH |
1299 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1300 | it will dynamically create a link-local address on the given | |
1301 | interface and start Duplicate Address Detection, if necessary. | |
1302 | ||
1303 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1304 | it will dynamically delete all address on the given interface. | |
1305 | ||
1b34be74 YH |
1306 | accept_dad - INTEGER |
1307 | Whether to accept DAD (Duplicate Address Detection). | |
1308 | 0: Disable DAD | |
1309 | 1: Enable DAD (default) | |
1310 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1311 | link-local address has been found. | |
1312 | ||
f7734fdf OP |
1313 | force_tllao - BOOLEAN |
1314 | Enable sending the target link-layer address option even when | |
1315 | responding to a unicast neighbor solicitation. | |
1316 | Default: FALSE | |
1317 | ||
1318 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1319 | ||
1320 | "The option MUST be included for multicast solicitations in order to | |
1321 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1322 | does not have a cache entry to return a Neighbor Advertisements | |
1323 | message. When responding to unicast solicitations, the option can be | |
1324 | omitted since the sender of the solicitation has the correct link- | |
1325 | layer address; otherwise it would not have be able to send the unicast | |
1326 | solicitation in the first place. However, including the link-layer | |
1327 | address in this case adds little overhead and eliminates a potential | |
1328 | race condition where the sender deletes the cached link-layer address | |
1329 | prior to receiving a response to a previous solicitation." | |
1330 | ||
db2b620a HFS |
1331 | ndisc_notify - BOOLEAN |
1332 | Define mode for notification of address and device changes. | |
1333 | 0 - (default): do nothing | |
1334 | 1 - Generate unsolicited neighbour advertisements when device is brought | |
1335 | up or hardware address changes. | |
1336 | ||
fc4eba58 HFS |
1337 | mldv1_unsolicited_report_interval - INTEGER |
1338 | The interval in milliseconds in which the next unsolicited | |
1339 | MLDv1 report retransmit will take place. | |
1340 | Default: 10000 (10 seconds) | |
1341 | ||
1342 | mldv2_unsolicited_report_interval - INTEGER | |
1343 | The interval in milliseconds in which the next unsolicited | |
1344 | MLDv2 report retransmit will take place. | |
1345 | Default: 1000 (1 second) | |
1346 | ||
f2127810 DB |
1347 | force_mld_version - INTEGER |
1348 | 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed | |
1349 | 1 - Enforce to use MLD version 1 | |
1350 | 2 - Enforce to use MLD version 2 | |
1351 | ||
b800c3b9 HFS |
1352 | suppress_frag_ndisc - INTEGER |
1353 | Control RFC 6980 (Security Implications of IPv6 Fragmentation | |
1354 | with IPv6 Neighbor Discovery) behavior: | |
1355 | 1 - (default) discard fragmented neighbor discovery packets | |
1356 | 0 - allow fragmented neighbor discovery packets | |
1357 | ||
1da177e4 LT |
1358 | icmp/*: |
1359 | ratelimit - INTEGER | |
1360 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1361 | 0 to disable any limiting, |
1362 | otherwise the minimal space between responses in milliseconds. | |
1363 | Default: 1000 | |
1da177e4 LT |
1364 | |
1365 | ||
1366 | IPv6 Update by: | |
1367 | Pekka Savola <pekkas@netcore.fi> | |
1368 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1369 | ||
1370 | ||
1371 | /proc/sys/net/bridge/* Variables: | |
1372 | ||
1373 | bridge-nf-call-arptables - BOOLEAN | |
1374 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1375 | 0 : disable this. | |
1376 | Default: 1 | |
1377 | ||
1378 | bridge-nf-call-iptables - BOOLEAN | |
1379 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1380 | 0 : disable this. | |
1381 | Default: 1 | |
1382 | ||
1383 | bridge-nf-call-ip6tables - BOOLEAN | |
1384 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1385 | 0 : disable this. | |
1386 | Default: 1 | |
1387 | ||
1388 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1389 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1390 | 0 : disable this. | |
4981682c | 1391 | Default: 0 |
516299d2 MM |
1392 | |
1393 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1394 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 | 1395 | 0 : disable this. |
4981682c | 1396 | Default: 0 |
1da177e4 | 1397 | |
4981682c PNA |
1398 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1399 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1400 | interface on the bridge and set the netfilter input device to the vlan. | |
1401 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1402 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1403 | vlan interface is found, or this switch is off, the input device is | |
1404 | set to the bridge interface. | |
1405 | 0: disable bridge netfilter vlan interface lookup. | |
1406 | Default: 0 | |
1da177e4 | 1407 | |
32e8d494 VY |
1408 | proc/sys/net/sctp/* Variables: |
1409 | ||
1410 | addip_enable - BOOLEAN | |
1411 | Enable or disable extension of Dynamic Address Reconfiguration | |
1412 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1413 | the ability to dynamically add and remove new addresses for the SCTP | |
1414 | associations. | |
1415 | ||
1416 | 1: Enable extension. | |
1417 | ||
1418 | 0: Disable extension. | |
1419 | ||
1420 | Default: 0 | |
1421 | ||
1422 | addip_noauth_enable - BOOLEAN | |
1423 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1424 | authentication to protect the operations of adding or removing new | |
1425 | addresses. This requirement is mandated so that unauthorized hosts | |
1426 | would not be able to hijack associations. However, older | |
1427 | implementations may not have implemented this requirement while | |
1428 | allowing the ADD-IP extension. For reasons of interoperability, | |
1429 | we provide this variable to control the enforcement of the | |
1430 | authentication requirement. | |
1431 | ||
1432 | 1: Allow ADD-IP extension to be used without authentication. This | |
1433 | should only be set in a closed environment for interoperability | |
1434 | with older implementations. | |
1435 | ||
1436 | 0: Enforce the authentication requirement | |
1437 | ||
1438 | Default: 0 | |
1439 | ||
1440 | auth_enable - BOOLEAN | |
1441 | Enable or disable Authenticated Chunks extension. This extension | |
1442 | provides the ability to send and receive authenticated chunks and is | |
1443 | required for secure operation of Dynamic Address Reconfiguration | |
1444 | (ADD-IP) extension. | |
1445 | ||
1446 | 1: Enable this extension. | |
1447 | 0: Disable this extension. | |
1448 | ||
1449 | Default: 0 | |
1450 | ||
1451 | prsctp_enable - BOOLEAN | |
1452 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1453 | is used to notify peers that a given DATA should no longer be expected. | |
1454 | ||
1455 | 1: Enable extension | |
1456 | 0: Disable | |
1457 | ||
1458 | Default: 1 | |
1459 | ||
1460 | max_burst - INTEGER | |
1461 | The limit of the number of new packets that can be initially sent. It | |
1462 | controls how bursty the generated traffic can be. | |
1463 | ||
1464 | Default: 4 | |
1465 | ||
1466 | association_max_retrans - INTEGER | |
1467 | Set the maximum number for retransmissions that an association can | |
1468 | attempt deciding that the remote end is unreachable. If this value | |
1469 | is exceeded, the association is terminated. | |
1470 | ||
1471 | Default: 10 | |
1472 | ||
1473 | max_init_retransmits - INTEGER | |
1474 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1475 | that an association will attempt before declaring the destination | |
1476 | unreachable and terminating. | |
1477 | ||
1478 | Default: 8 | |
1479 | ||
1480 | path_max_retrans - INTEGER | |
1481 | The maximum number of retransmissions that will be attempted on a given | |
1482 | path. Once this threshold is exceeded, the path is considered | |
1483 | unreachable, and new traffic will use a different path when the | |
1484 | association is multihomed. | |
1485 | ||
1486 | Default: 5 | |
1487 | ||
5aa93bcf NH |
1488 | pf_retrans - INTEGER |
1489 | The number of retransmissions that will be attempted on a given path | |
1490 | before traffic is redirected to an alternate transport (should one | |
1491 | exist). Note this is distinct from path_max_retrans, as a path that | |
1492 | passes the pf_retrans threshold can still be used. Its only | |
1493 | deprioritized when a transmission path is selected by the stack. This | |
1494 | setting is primarily used to enable fast failover mechanisms without | |
1495 | having to reduce path_max_retrans to a very low value. See: | |
1496 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
1497 | for details. Note also that a value of pf_retrans > path_max_retrans | |
1498 | disables this feature | |
1499 | ||
1500 | Default: 0 | |
1501 | ||
32e8d494 VY |
1502 | rto_initial - INTEGER |
1503 | The initial round trip timeout value in milliseconds that will be used | |
1504 | in calculating round trip times. This is the initial time interval | |
1505 | for retransmissions. | |
1506 | ||
1507 | Default: 3000 | |
1da177e4 | 1508 | |
32e8d494 VY |
1509 | rto_max - INTEGER |
1510 | The maximum value (in milliseconds) of the round trip timeout. This | |
1511 | is the largest time interval that can elapse between retransmissions. | |
1512 | ||
1513 | Default: 60000 | |
1514 | ||
1515 | rto_min - INTEGER | |
1516 | The minimum value (in milliseconds) of the round trip timeout. This | |
1517 | is the smallest time interval the can elapse between retransmissions. | |
1518 | ||
1519 | Default: 1000 | |
1520 | ||
1521 | hb_interval - INTEGER | |
1522 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1523 | are sent at the specified interval on idle paths to probe the state of | |
1524 | a given path between 2 associations. | |
1525 | ||
1526 | Default: 30000 | |
1527 | ||
1528 | sack_timeout - INTEGER | |
1529 | The amount of time (in milliseconds) that the implementation will wait | |
1530 | to send a SACK. | |
1531 | ||
1532 | Default: 200 | |
1533 | ||
1534 | valid_cookie_life - INTEGER | |
1535 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1536 | is used during association establishment. | |
1537 | ||
1538 | Default: 60000 | |
1539 | ||
1540 | cookie_preserve_enable - BOOLEAN | |
1541 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1542 | that is used during the establishment phase of SCTP association | |
1543 | ||
1544 | 1: Enable cookie lifetime extension. | |
1545 | 0: Disable | |
1546 | ||
1547 | Default: 1 | |
1548 | ||
3c68198e NH |
1549 | cookie_hmac_alg - STRING |
1550 | Select the hmac algorithm used when generating the cookie value sent by | |
1551 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
1552 | Valid values are: | |
1553 | * md5 | |
1554 | * sha1 | |
1555 | * none | |
1556 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
3b09adcb | 1557 | configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and |
3c68198e NH |
1558 | CONFIG_CRYPTO_SHA1). |
1559 | ||
1560 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
1561 | available, else none. | |
1562 | ||
32e8d494 VY |
1563 | rcvbuf_policy - INTEGER |
1564 | Determines if the receive buffer is attributed to the socket or to | |
1565 | association. SCTP supports the capability to create multiple | |
1566 | associations on a single socket. When using this capability, it is | |
1567 | possible that a single stalled association that's buffering a lot | |
1568 | of data may block other associations from delivering their data by | |
1569 | consuming all of the receive buffer space. To work around this, | |
1570 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1571 | to each association instead of the socket. This prevents the described | |
1572 | blocking. | |
1573 | ||
1574 | 1: rcvbuf space is per association | |
3b09adcb | 1575 | 0: rcvbuf space is per socket |
32e8d494 VY |
1576 | |
1577 | Default: 0 | |
1578 | ||
1579 | sndbuf_policy - INTEGER | |
1580 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1581 | ||
1582 | 1: Send buffer is tracked per association | |
1583 | 0: Send buffer is tracked per socket. | |
1584 | ||
1585 | Default: 0 | |
1586 | ||
1587 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1588 | Number of pages allowed for queueing by all SCTP sockets. | |
1589 | ||
1590 | min: Below this number of pages SCTP is not bothered about its | |
1591 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1592 | this number, SCTP starts to moderate memory usage. | |
1593 | ||
1594 | pressure: This value was introduced to follow format of tcp_mem. | |
1595 | ||
1596 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1597 | ||
1598 | Default is calculated at boot time from amount of available memory. | |
1599 | ||
1600 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
1601 | Only the first value ("min") is used, "default" and "max" are |
1602 | ignored. | |
1603 | ||
1604 | min: Minimal size of receive buffer used by SCTP socket. | |
1605 | It is guaranteed to each SCTP socket (but not association) even | |
1606 | under moderate memory pressure. | |
1607 | ||
1608 | Default: 1 page | |
32e8d494 VY |
1609 | |
1610 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b | 1611 | Currently this tunable has no effect. |
32e8d494 | 1612 | |
72388433 BD |
1613 | addr_scope_policy - INTEGER |
1614 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
1615 | ||
1616 | 0 - Disable IPv4 address scoping | |
1617 | 1 - Enable IPv4 address scoping | |
1618 | 2 - Follow draft but allow IPv4 private addresses | |
1619 | 3 - Follow draft but allow IPv4 link local addresses | |
1620 | ||
1621 | Default: 1 | |
1622 | ||
1da177e4 | 1623 | |
4edc2f34 | 1624 | /proc/sys/net/core/* |
c60f6aa8 | 1625 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. |
705efc3b | 1626 | |
4edc2f34 SH |
1627 | |
1628 | /proc/sys/net/unix/* | |
705efc3b WT |
1629 | max_dgram_qlen - INTEGER |
1630 | The maximum length of dgram socket receive queue | |
1631 | ||
1632 | Default: 10 | |
1633 | ||
1634 | ||
1635 | UNDOCUMENTED: | |
4edc2f34 SH |
1636 | |
1637 | /proc/sys/net/irda/* | |
1638 | fast_poll_increase FIXME | |
1639 | warn_noreply_time FIXME | |
1640 | discovery_slots FIXME | |
1641 | slot_timeout FIXME | |
1642 | max_baud_rate FIXME | |
1643 | discovery_timeout FIXME | |
1644 | lap_keepalive_time FIXME | |
1645 | max_noreply_time FIXME | |
1646 | max_tx_data_size FIXME | |
1647 | max_tx_window FIXME | |
1648 | min_tx_turn_time FIXME |