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 | 17 | |
cd174e67 HFS |
18 | ip_no_pmtu_disc - INTEGER |
19 | Disable Path MTU Discovery. If enabled in mode 1 and a | |
188b04d5 HFS |
20 | fragmentation-required ICMP is received, the PMTU to this |
21 | destination will be set to min_pmtu (see below). You will need | |
22 | to raise min_pmtu to the smallest interface MTU on your system | |
23 | manually if you want to avoid locally generated fragments. | |
cd174e67 HFS |
24 | |
25 | In mode 2 incoming Path MTU Discovery messages will be | |
26 | discarded. Outgoing frames are handled the same as in mode 1, | |
27 | implicitly setting IP_PMTUDISC_DONT on every created socket. | |
28 | ||
8ed1dc44 HFS |
29 | Mode 3 is a hardend pmtu discover mode. The kernel will only |
30 | accept fragmentation-needed errors if the underlying protocol | |
31 | can verify them besides a plain socket lookup. Current | |
32 | protocols for which pmtu events will be honored are TCP, SCTP | |
33 | and DCCP as they verify e.g. the sequence number or the | |
34 | association. This mode should not be enabled globally but is | |
35 | only intended to secure e.g. name servers in namespaces where | |
36 | TCP path mtu must still work but path MTU information of other | |
37 | protocols should be discarded. If enabled globally this mode | |
38 | could break other protocols. | |
39 | ||
40 | Possible values: 0-3 | |
188b04d5 | 41 | Default: FALSE |
1da177e4 LT |
42 | |
43 | min_pmtu - INTEGER | |
20db93c3 | 44 | default 552 - minimum discovered Path MTU |
1da177e4 | 45 | |
f87c10a8 HFS |
46 | ip_forward_use_pmtu - BOOLEAN |
47 | By default we don't trust protocol path MTUs while forwarding | |
48 | because they could be easily forged and can lead to unwanted | |
49 | fragmentation by the router. | |
50 | You only need to enable this if you have user-space software | |
51 | which tries to discover path mtus by itself and depends on the | |
52 | kernel honoring this information. This is normally not the | |
53 | case. | |
54 | Default: 0 (disabled) | |
55 | Possible values: | |
56 | 0 - disabled | |
57 | 1 - enabled | |
58 | ||
cbaf087a BG |
59 | route/max_size - INTEGER |
60 | Maximum number of routes allowed in the kernel. Increase | |
61 | this when using large numbers of interfaces and/or routes. | |
62 | ||
2724680b YH |
63 | neigh/default/gc_thresh1 - INTEGER |
64 | Minimum number of entries to keep. Garbage collector will not | |
65 | purge entries if there are fewer than this number. | |
b66c66dc | 66 | Default: 128 |
2724680b | 67 | |
a3d12146 | 68 | neigh/default/gc_thresh2 - INTEGER |
69 | Threshold when garbage collector becomes more aggressive about | |
70 | purging entries. Entries older than 5 seconds will be cleared | |
71 | when over this number. | |
72 | Default: 512 | |
73 | ||
cbaf087a BG |
74 | neigh/default/gc_thresh3 - INTEGER |
75 | Maximum number of neighbor entries allowed. Increase this | |
76 | when using large numbers of interfaces and when communicating | |
77 | with large numbers of directly-connected peers. | |
cc868028 | 78 | Default: 1024 |
cbaf087a | 79 | |
8b5c171b ED |
80 | neigh/default/unres_qlen_bytes - INTEGER |
81 | The maximum number of bytes which may be used by packets | |
82 | queued for each unresolved address by other network layers. | |
83 | (added in linux 3.3) | |
3b09adcb | 84 | Setting negative value is meaningless and will return error. |
cc868028 | 85 | Default: 65536 Bytes(64KB) |
8b5c171b ED |
86 | |
87 | neigh/default/unres_qlen - INTEGER | |
88 | The maximum number of packets which may be queued for each | |
89 | unresolved address by other network layers. | |
90 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
cc868028 | 91 | Prior to linux 3.3, the default value is 3 which may cause |
5d248c49 | 92 | unexpected packet loss. The current default value is calculated |
cc868028 SW |
93 | according to default value of unres_qlen_bytes and true size of |
94 | packet. | |
95 | Default: 31 | |
8b5c171b | 96 | |
1da177e4 LT |
97 | mtu_expires - INTEGER |
98 | Time, in seconds, that cached PMTU information is kept. | |
99 | ||
100 | min_adv_mss - INTEGER | |
101 | The advertised MSS depends on the first hop route MTU, but will | |
102 | never be lower than this setting. | |
103 | ||
104 | IP Fragmentation: | |
105 | ||
106 | ipfrag_high_thresh - INTEGER | |
e18f5feb | 107 | Maximum memory used to reassemble IP fragments. When |
1da177e4 LT |
108 | ipfrag_high_thresh bytes of memory is allocated for this purpose, |
109 | the fragment handler will toss packets until ipfrag_low_thresh | |
1bab4c75 NA |
110 | is reached. This also serves as a maximum limit to namespaces |
111 | different from the initial one. | |
e18f5feb | 112 | |
1da177e4 | 113 | ipfrag_low_thresh - INTEGER |
b13d3cbf FW |
114 | Maximum memory used to reassemble IP fragments before the kernel |
115 | begins to remove incomplete fragment queues to free up resources. | |
116 | The kernel still accepts new fragments for defragmentation. | |
1da177e4 LT |
117 | |
118 | ipfrag_time - INTEGER | |
e18f5feb | 119 | Time in seconds to keep an IP fragment in memory. |
1da177e4 | 120 | |
89cee8b1 | 121 | ipfrag_max_dist - INTEGER |
e18f5feb JDB |
122 | ipfrag_max_dist is a non-negative integer value which defines the |
123 | maximum "disorder" which is allowed among fragments which share a | |
124 | common IP source address. Note that reordering of packets is | |
125 | not unusual, but if a large number of fragments arrive from a source | |
126 | IP address while a particular fragment queue remains incomplete, it | |
127 | probably indicates that one or more fragments belonging to that queue | |
128 | have been lost. When ipfrag_max_dist is positive, an additional check | |
129 | is done on fragments before they are added to a reassembly queue - if | |
130 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
131 | address between additions to any IP fragment queue using that source | |
132 | address, it's presumed that one or more fragments in the queue are | |
133 | lost. The existing fragment queue will be dropped, and a new one | |
89cee8b1 HX |
134 | started. An ipfrag_max_dist value of zero disables this check. |
135 | ||
136 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
137 | result in unnecessarily dropping fragment queues when normal | |
e18f5feb JDB |
138 | reordering of packets occurs, which could lead to poor application |
139 | performance. Using a very large value, e.g. 50000, increases the | |
140 | likelihood of incorrectly reassembling IP fragments that originate | |
89cee8b1 HX |
141 | from different IP datagrams, which could result in data corruption. |
142 | Default: 64 | |
143 | ||
1da177e4 LT |
144 | INET peer storage: |
145 | ||
146 | inet_peer_threshold - INTEGER | |
e18f5feb | 147 | The approximate size of the storage. Starting from this threshold |
1da177e4 LT |
148 | entries will be thrown aggressively. This threshold also determines |
149 | entries' time-to-live and time intervals between garbage collection | |
150 | passes. More entries, less time-to-live, less GC interval. | |
151 | ||
152 | inet_peer_minttl - INTEGER | |
153 | Minimum time-to-live of entries. Should be enough to cover fragment | |
154 | time-to-live on the reassembling side. This minimum time-to-live is | |
155 | guaranteed if the pool size is less than inet_peer_threshold. | |
77a538d5 | 156 | Measured in seconds. |
1da177e4 LT |
157 | |
158 | inet_peer_maxttl - INTEGER | |
159 | Maximum time-to-live of entries. Unused entries will expire after | |
160 | this period of time if there is no memory pressure on the pool (i.e. | |
161 | when the number of entries in the pool is very small). | |
77a538d5 | 162 | Measured in seconds. |
1da177e4 | 163 | |
e18f5feb | 164 | TCP variables: |
1da177e4 | 165 | |
ef56e622 SH |
166 | somaxconn - INTEGER |
167 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
168 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
169 | for TCP sockets. | |
170 | ||
ef56e622 SH |
171 | tcp_abort_on_overflow - BOOLEAN |
172 | If listening service is too slow to accept new connections, | |
173 | reset them. Default state is FALSE. It means that if overflow | |
174 | occurred due to a burst, connection will recover. Enable this | |
175 | option _only_ if you are really sure that listening daemon | |
176 | cannot be tuned to accept connections faster. Enabling this | |
177 | option can harm clients of your server. | |
1da177e4 | 178 | |
ef56e622 SH |
179 | tcp_adv_win_scale - INTEGER |
180 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
181 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
182 | if it is <= 0. | |
0147fc05 | 183 | Possible values are [-31, 31], inclusive. |
b49960a0 | 184 | Default: 1 |
1da177e4 | 185 | |
ef56e622 SH |
186 | tcp_allowed_congestion_control - STRING |
187 | Show/set the congestion control choices available to non-privileged | |
188 | processes. The list is a subset of those listed in | |
189 | tcp_available_congestion_control. | |
190 | Default is "reno" and the default setting (tcp_congestion_control). | |
1da177e4 | 191 | |
ef56e622 SH |
192 | tcp_app_win - INTEGER |
193 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
194 | buffer. Value 0 is special, it means that nothing is reserved. | |
195 | Default: 31 | |
1da177e4 | 196 | |
f54b3111 ED |
197 | tcp_autocorking - BOOLEAN |
198 | Enable TCP auto corking : | |
199 | When applications do consecutive small write()/sendmsg() system calls, | |
200 | we try to coalesce these small writes as much as possible, to lower | |
201 | total amount of sent packets. This is done if at least one prior | |
202 | packet for the flow is waiting in Qdisc queues or device transmit | |
203 | queue. Applications can still use TCP_CORK for optimal behavior | |
204 | when they know how/when to uncork their sockets. | |
205 | Default : 1 | |
206 | ||
ef56e622 SH |
207 | tcp_available_congestion_control - STRING |
208 | Shows the available congestion control choices that are registered. | |
209 | More congestion control algorithms may be available as modules, | |
210 | but not loaded. | |
1da177e4 | 211 | |
71599cd1 | 212 | tcp_base_mss - INTEGER |
4edc2f34 SH |
213 | The initial value of search_low to be used by the packetization layer |
214 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
215 | this is the initial MSS used by the connection. | |
71599cd1 | 216 | |
ef56e622 SH |
217 | tcp_congestion_control - STRING |
218 | Set the congestion control algorithm to be used for new | |
219 | connections. The algorithm "reno" is always available, but | |
220 | additional choices may be available based on kernel configuration. | |
221 | Default is set as part of kernel configuration. | |
d8a6e65f ED |
222 | For passive connections, the listener congestion control choice |
223 | is inherited. | |
224 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
1da177e4 | 225 | |
ef56e622 SH |
226 | tcp_dsack - BOOLEAN |
227 | Allows TCP to send "duplicate" SACKs. | |
1da177e4 | 228 | |
eed530b6 YC |
229 | tcp_early_retrans - INTEGER |
230 | Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold | |
231 | for triggering fast retransmit when the amount of outstanding data is | |
232 | small and when no previously unsent data can be transmitted (such | |
6ba8a3b1 | 233 | that limited transmit could be used). Also controls the use of |
3dd17ede | 234 | Tail loss probe (TLP) that converts RTOs occurring due to tail |
6ba8a3b1 | 235 | losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01). |
eed530b6 YC |
236 | Possible values: |
237 | 0 disables ER | |
238 | 1 enables ER | |
239 | 2 enables ER but delays fast recovery and fast retransmit | |
240 | by a fourth of RTT. This mitigates connection falsely | |
241 | recovers when network has a small degree of reordering | |
242 | (less than 3 packets). | |
6ba8a3b1 ND |
243 | 3 enables delayed ER and TLP. |
244 | 4 enables TLP only. | |
245 | Default: 3 | |
eed530b6 | 246 | |
34a6ef38 | 247 | tcp_ecn - INTEGER |
7e3a2dc5 RJ |
248 | Control use of Explicit Congestion Notification (ECN) by TCP. |
249 | ECN is used only when both ends of the TCP connection indicate | |
250 | support for it. This feature is useful in avoiding losses due | |
251 | to congestion by allowing supporting routers to signal | |
252 | congestion before having to drop packets. | |
255cac91 | 253 | Possible values are: |
7e3a2dc5 | 254 | 0 Disable ECN. Neither initiate nor accept ECN. |
3d55b323 VS |
255 | 1 Enable ECN when requested by incoming connections and |
256 | also request ECN on outgoing connection attempts. | |
257 | 2 Enable ECN when requested by incoming connections | |
7e3a2dc5 | 258 | but do not request ECN on outgoing connections. |
255cac91 | 259 | Default: 2 |
ef56e622 SH |
260 | |
261 | tcp_fack - BOOLEAN | |
262 | Enable FACK congestion avoidance and fast retransmission. | |
263 | The value is not used, if tcp_sack is not enabled. | |
1da177e4 LT |
264 | |
265 | tcp_fin_timeout - INTEGER | |
d825da2e RJ |
266 | The length of time an orphaned (no longer referenced by any |
267 | application) connection will remain in the FIN_WAIT_2 state | |
268 | before it is aborted at the local end. While a perfectly | |
269 | valid "receive only" state for an un-orphaned connection, an | |
270 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
271 | forever for the remote to close its end of the connection. | |
272 | Cf. tcp_max_orphans | |
273 | Default: 60 seconds | |
1da177e4 | 274 | |
89808060 | 275 | tcp_frto - INTEGER |
e33099f9 | 276 | Enables Forward RTO-Recovery (F-RTO) defined in RFC5682. |
cd99889c | 277 | F-RTO is an enhanced recovery algorithm for TCP retransmission |
e33099f9 YC |
278 | timeouts. It is particularly beneficial in networks where the |
279 | RTT fluctuates (e.g., wireless). F-RTO is sender-side only | |
280 | modification. It does not require any support from the peer. | |
281 | ||
282 | By default it's enabled with a non-zero value. 0 disables F-RTO. | |
1da177e4 | 283 | |
ef56e622 SH |
284 | tcp_keepalive_time - INTEGER |
285 | How often TCP sends out keepalive messages when keepalive is enabled. | |
286 | Default: 2hours. | |
1da177e4 | 287 | |
ef56e622 SH |
288 | tcp_keepalive_probes - INTEGER |
289 | How many keepalive probes TCP sends out, until it decides that the | |
290 | connection is broken. Default value: 9. | |
291 | ||
292 | tcp_keepalive_intvl - INTEGER | |
293 | How frequently the probes are send out. Multiplied by | |
294 | tcp_keepalive_probes it is time to kill not responding connection, | |
295 | after probes started. Default value: 75sec i.e. connection | |
296 | will be aborted after ~11 minutes of retries. | |
297 | ||
298 | tcp_low_latency - BOOLEAN | |
299 | If set, the TCP stack makes decisions that prefer lower | |
300 | latency as opposed to higher throughput. By default, this | |
301 | option is not set meaning that higher throughput is preferred. | |
302 | An example of an application where this default should be | |
303 | changed would be a Beowulf compute cluster. | |
304 | Default: 0 | |
1da177e4 LT |
305 | |
306 | tcp_max_orphans - INTEGER | |
307 | Maximal number of TCP sockets not attached to any user file handle, | |
308 | held by system. If this number is exceeded orphaned connections are | |
309 | reset immediately and warning is printed. This limit exists | |
310 | only to prevent simple DoS attacks, you _must_ not rely on this | |
311 | or lower the limit artificially, but rather increase it | |
312 | (probably, after increasing installed memory), | |
313 | if network conditions require more than default value, | |
314 | and tune network services to linger and kill such states | |
315 | more aggressively. Let me to remind again: each orphan eats | |
316 | up to ~64K of unswappable memory. | |
317 | ||
1da177e4 | 318 | tcp_max_syn_backlog - INTEGER |
99b53bdd PP |
319 | Maximal number of remembered connection requests, which have not |
320 | received an acknowledgment from connecting client. | |
321 | The minimal value is 128 for low memory machines, and it will | |
322 | increase in proportion to the memory of machine. | |
323 | If server suffers from overload, try increasing this number. | |
1da177e4 | 324 | |
ef56e622 SH |
325 | tcp_max_tw_buckets - INTEGER |
326 | Maximal number of timewait sockets held by system simultaneously. | |
327 | If this number is exceeded time-wait socket is immediately destroyed | |
328 | and warning is printed. This limit exists only to prevent | |
329 | simple DoS attacks, you _must_ not lower the limit artificially, | |
330 | but rather increase it (probably, after increasing installed memory), | |
331 | if network conditions require more than default value. | |
1da177e4 | 332 | |
ef56e622 SH |
333 | tcp_mem - vector of 3 INTEGERs: min, pressure, max |
334 | min: below this number of pages TCP is not bothered about its | |
335 | memory appetite. | |
1da177e4 | 336 | |
ef56e622 SH |
337 | pressure: when amount of memory allocated by TCP exceeds this number |
338 | of pages, TCP moderates its memory consumption and enters memory | |
339 | pressure mode, which is exited when memory consumption falls | |
340 | under "min". | |
1da177e4 | 341 | |
ef56e622 | 342 | max: number of pages allowed for queueing by all TCP sockets. |
1da177e4 | 343 | |
ef56e622 SH |
344 | Defaults are calculated at boot time from amount of available |
345 | memory. | |
1da177e4 | 346 | |
71599cd1 | 347 | tcp_moderate_rcvbuf - BOOLEAN |
4edc2f34 | 348 | If set, TCP performs receive buffer auto-tuning, attempting to |
71599cd1 JH |
349 | automatically size the buffer (no greater than tcp_rmem[2]) to |
350 | match the size required by the path for full throughput. Enabled by | |
351 | default. | |
352 | ||
353 | tcp_mtu_probing - INTEGER | |
354 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
355 | values: | |
356 | 0 - Disabled | |
357 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
358 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
359 | ||
360 | tcp_no_metrics_save - BOOLEAN | |
361 | By default, TCP saves various connection metrics in the route cache | |
362 | when the connection closes, so that connections established in the | |
363 | near future can use these to set initial conditions. Usually, this | |
364 | increases overall performance, but may sometimes cause performance | |
0f035b8e | 365 | degradation. If set, TCP will not cache metrics on closing |
71599cd1 JH |
366 | connections. |
367 | ||
ef56e622 | 368 | tcp_orphan_retries - INTEGER |
5d789229 DL |
369 | This value influences the timeout of a locally closed TCP connection, |
370 | when RTO retransmissions remain unacknowledged. | |
371 | See tcp_retries2 for more details. | |
372 | ||
06b8fc5d | 373 | The default value is 8. |
5d789229 | 374 | If your machine is a loaded WEB server, |
ef56e622 SH |
375 | you should think about lowering this value, such sockets |
376 | may consume significant resources. Cf. tcp_max_orphans. | |
1da177e4 LT |
377 | |
378 | tcp_reordering - INTEGER | |
379 | Maximal reordering of packets in a TCP stream. | |
e18f5feb | 380 | Default: 3 |
1da177e4 LT |
381 | |
382 | tcp_retrans_collapse - BOOLEAN | |
383 | Bug-to-bug compatibility with some broken printers. | |
384 | On retransmit try to send bigger packets to work around bugs in | |
385 | certain TCP stacks. | |
386 | ||
ef56e622 | 387 | tcp_retries1 - INTEGER |
5d789229 DL |
388 | This value influences the time, after which TCP decides, that |
389 | something is wrong due to unacknowledged RTO retransmissions, | |
390 | and reports this suspicion to the network layer. | |
391 | See tcp_retries2 for more details. | |
392 | ||
393 | RFC 1122 recommends at least 3 retransmissions, which is the | |
394 | default. | |
1da177e4 | 395 | |
ef56e622 | 396 | tcp_retries2 - INTEGER |
5d789229 DL |
397 | This value influences the timeout of an alive TCP connection, |
398 | when RTO retransmissions remain unacknowledged. | |
399 | Given a value of N, a hypothetical TCP connection following | |
400 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
401 | retransmit N times before killing the connection at the (N+1)th RTO. | |
402 | ||
403 | The default value of 15 yields a hypothetical timeout of 924.6 | |
404 | seconds and is a lower bound for the effective timeout. | |
405 | TCP will effectively time out at the first RTO which exceeds the | |
406 | hypothetical timeout. | |
407 | ||
408 | RFC 1122 recommends at least 100 seconds for the timeout, | |
409 | which corresponds to a value of at least 8. | |
1da177e4 | 410 | |
ef56e622 SH |
411 | tcp_rfc1337 - BOOLEAN |
412 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
413 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
414 | assassination. | |
415 | Default: 0 | |
1da177e4 LT |
416 | |
417 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
418 | min: Minimal size of receive buffer used by TCP sockets. | |
419 | It is guaranteed to each TCP socket, even under moderate memory | |
420 | pressure. | |
6539fefd | 421 | Default: 1 page |
1da177e4 | 422 | |
53025f5e | 423 | default: initial size of receive buffer used by TCP sockets. |
1da177e4 LT |
424 | This value overrides net.core.rmem_default used by other protocols. |
425 | Default: 87380 bytes. This value results in window of 65535 with | |
426 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
427 | less for default tcp_app_win. See below about these variables. | |
428 | ||
429 | max: maximal size of receive buffer allowed for automatically | |
430 | selected receiver buffers for TCP socket. This value does not override | |
53025f5e BF |
431 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables |
432 | automatic tuning of that socket's receive buffer size, in which | |
433 | case this value is ignored. | |
b49960a0 | 434 | Default: between 87380B and 6MB, depending on RAM size. |
1da177e4 | 435 | |
ef56e622 SH |
436 | tcp_sack - BOOLEAN |
437 | Enable select acknowledgments (SACKS). | |
1da177e4 | 438 | |
ef56e622 SH |
439 | tcp_slow_start_after_idle - BOOLEAN |
440 | If set, provide RFC2861 behavior and time out the congestion | |
441 | window after an idle period. An idle period is defined at | |
442 | the current RTO. If unset, the congestion window will not | |
443 | be timed out after an idle period. | |
444 | Default: 1 | |
1da177e4 | 445 | |
ef56e622 | 446 | tcp_stdurg - BOOLEAN |
4edc2f34 | 447 | Use the Host requirements interpretation of the TCP urgent pointer field. |
ef56e622 SH |
448 | Most hosts use the older BSD interpretation, so if you turn this on |
449 | Linux might not communicate correctly with them. | |
450 | Default: FALSE | |
1da177e4 | 451 | |
ef56e622 SH |
452 | tcp_synack_retries - INTEGER |
453 | Number of times SYNACKs for a passive TCP connection attempt will | |
454 | be retransmitted. Should not be higher than 255. Default value | |
6c9ff979 AB |
455 | is 5, which corresponds to 31seconds till the last retransmission |
456 | with the current initial RTO of 1second. With this the final timeout | |
457 | for a passive TCP connection will happen after 63seconds. | |
1da177e4 | 458 | |
ef56e622 | 459 | tcp_syncookies - BOOLEAN |
a3c910d2 | 460 | Only valid when the kernel was compiled with CONFIG_SYN_COOKIES |
ef56e622 | 461 | Send out syncookies when the syn backlog queue of a socket |
4edc2f34 | 462 | overflows. This is to prevent against the common 'SYN flood attack' |
a3c910d2 | 463 | Default: 1 |
1da177e4 | 464 | |
ef56e622 SH |
465 | Note, that syncookies is fallback facility. |
466 | It MUST NOT be used to help highly loaded servers to stand | |
4edc2f34 | 467 | against legal connection rate. If you see SYN flood warnings |
ef56e622 SH |
468 | in your logs, but investigation shows that they occur |
469 | because of overload with legal connections, you should tune | |
470 | another parameters until this warning disappear. | |
471 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
1da177e4 | 472 | |
ef56e622 SH |
473 | syncookies seriously violate TCP protocol, do not allow |
474 | to use TCP extensions, can result in serious degradation | |
475 | of some services (f.e. SMTP relaying), visible not by you, | |
476 | but your clients and relays, contacting you. While you see | |
4edc2f34 | 477 | SYN flood warnings in logs not being really flooded, your server |
ef56e622 | 478 | is seriously misconfigured. |
1da177e4 | 479 | |
5ad37d5d HFS |
480 | If you want to test which effects syncookies have to your |
481 | network connections you can set this knob to 2 to enable | |
482 | unconditionally generation of syncookies. | |
483 | ||
cf60af03 YC |
484 | tcp_fastopen - INTEGER |
485 | Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data | |
486 | in the opening SYN packet. To use this feature, the client application | |
10467163 JC |
487 | must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than |
488 | connect() to perform a TCP handshake automatically. | |
489 | ||
490 | The values (bitmap) are | |
0d41cca4 | 491 | 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN. |
10467163 JC |
492 | 2: Enables TCP Fast Open on the server side, i.e., allowing data in |
493 | a SYN packet to be accepted and passed to the application before | |
494 | 3-way hand shake finishes. | |
495 | 4: Send data in the opening SYN regardless of cookie availability and | |
496 | without a cookie option. | |
497 | 0x100: Accept SYN data w/o validating the cookie. | |
498 | 0x200: Accept data-in-SYN w/o any cookie option present. | |
499 | 0x400/0x800: Enable Fast Open on all listeners regardless of the | |
500 | TCP_FASTOPEN socket option. The two different flags designate two | |
501 | different ways of setting max_qlen without the TCP_FASTOPEN socket | |
502 | option. | |
cf60af03 | 503 | |
0d41cca4 | 504 | Default: 1 |
cf60af03 | 505 | |
10467163 JC |
506 | Note that the client & server side Fast Open flags (1 and 2 |
507 | respectively) must be also enabled before the rest of flags can take | |
508 | effect. | |
509 | ||
510 | See include/net/tcp.h and the code for more details. | |
511 | ||
ef56e622 SH |
512 | tcp_syn_retries - INTEGER |
513 | Number of times initial SYNs for an active TCP connection attempt | |
514 | will be retransmitted. Should not be higher than 255. Default value | |
3b09adcb | 515 | is 6, which corresponds to 63seconds till the last retransmission |
6c9ff979 AB |
516 | with the current initial RTO of 1second. With this the final timeout |
517 | for an active TCP connection attempt will happen after 127seconds. | |
ef56e622 SH |
518 | |
519 | tcp_timestamps - BOOLEAN | |
520 | Enable timestamps as defined in RFC1323. | |
1da177e4 | 521 | |
95bd09eb ED |
522 | tcp_min_tso_segs - INTEGER |
523 | Minimal number of segments per TSO frame. | |
524 | Since linux-3.12, TCP does an automatic sizing of TSO frames, | |
525 | depending on flow rate, instead of filling 64Kbytes packets. | |
526 | For specific usages, it's possible to force TCP to build big | |
527 | TSO frames. Note that TCP stack might split too big TSO packets | |
528 | if available window is too small. | |
529 | Default: 2 | |
530 | ||
1da177e4 | 531 | tcp_tso_win_divisor - INTEGER |
ef56e622 SH |
532 | This allows control over what percentage of the congestion window |
533 | can be consumed by a single TSO frame. | |
534 | The setting of this parameter is a choice between burstiness and | |
535 | building larger TSO frames. | |
536 | Default: 3 | |
1da177e4 | 537 | |
ef56e622 SH |
538 | tcp_tw_recycle - BOOLEAN |
539 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
540 | It should not be changed without advice/request of technical | |
541 | experts. | |
1da177e4 | 542 | |
ef56e622 SH |
543 | tcp_tw_reuse - BOOLEAN |
544 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
545 | safe from protocol viewpoint. Default value is 0. | |
546 | It should not be changed without advice/request of technical | |
547 | experts. | |
ce7bc3bf | 548 | |
ef56e622 SH |
549 | tcp_window_scaling - BOOLEAN |
550 | Enable window scaling as defined in RFC1323. | |
3ff825b2 | 551 | |
ef56e622 | 552 | tcp_wmem - vector of 3 INTEGERs: min, default, max |
53025f5e | 553 | min: Amount of memory reserved for send buffers for TCP sockets. |
ef56e622 | 554 | Each TCP socket has rights to use it due to fact of its birth. |
6539fefd | 555 | Default: 1 page |
9d7bcfc6 | 556 | |
53025f5e BF |
557 | default: initial size of send buffer used by TCP sockets. This |
558 | value overrides net.core.wmem_default used by other protocols. | |
559 | It is usually lower than net.core.wmem_default. | |
ef56e622 SH |
560 | Default: 16K |
561 | ||
53025f5e BF |
562 | max: Maximal amount of memory allowed for automatically tuned |
563 | send buffers for TCP sockets. This value does not override | |
564 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
565 | automatic tuning of that socket's send buffer size, in which case | |
566 | this value is ignored. | |
567 | Default: between 64K and 4MB, depending on RAM size. | |
1da177e4 | 568 | |
c9bee3b7 ED |
569 | tcp_notsent_lowat - UNSIGNED INTEGER |
570 | A TCP socket can control the amount of unsent bytes in its write queue, | |
571 | thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() | |
572 | reports POLLOUT events if the amount of unsent bytes is below a per | |
573 | socket value, and if the write queue is not full. sendmsg() will | |
574 | also not add new buffers if the limit is hit. | |
575 | ||
576 | This global variable controls the amount of unsent data for | |
577 | sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change | |
578 | to the global variable has immediate effect. | |
579 | ||
580 | Default: UINT_MAX (0xFFFFFFFF) | |
581 | ||
15d99e02 RJ |
582 | tcp_workaround_signed_windows - BOOLEAN |
583 | If set, assume no receipt of a window scaling option means the | |
584 | remote TCP is broken and treats the window as a signed quantity. | |
585 | If unset, assume the remote TCP is not broken even if we do | |
586 | not receive a window scaling option from them. | |
587 | Default: 0 | |
588 | ||
72d0b7a8 CL |
589 | tcp_dma_copybreak - INTEGER |
590 | Lower limit, in bytes, of the size of socket reads that will be | |
591 | offloaded to a DMA copy engine, if one is present in the system | |
592 | and CONFIG_NET_DMA is enabled. | |
593 | Default: 4096 | |
594 | ||
36e31b0a AP |
595 | tcp_thin_linear_timeouts - BOOLEAN |
596 | Enable dynamic triggering of linear timeouts for thin streams. | |
597 | If set, a check is performed upon retransmission by timeout to | |
598 | determine if the stream is thin (less than 4 packets in flight). | |
599 | As long as the stream is found to be thin, up to 6 linear | |
600 | timeouts may be performed before exponential backoff mode is | |
601 | initiated. This improves retransmission latency for | |
602 | non-aggressive thin streams, often found to be time-dependent. | |
603 | For more information on thin streams, see | |
604 | Documentation/networking/tcp-thin.txt | |
605 | Default: 0 | |
606 | ||
7e380175 AP |
607 | tcp_thin_dupack - BOOLEAN |
608 | Enable dynamic triggering of retransmissions after one dupACK | |
609 | for thin streams. If set, a check is performed upon reception | |
610 | of a dupACK to determine if the stream is thin (less than 4 | |
611 | packets in flight). As long as the stream is found to be thin, | |
612 | data is retransmitted on the first received dupACK. This | |
613 | improves retransmission latency for non-aggressive thin | |
614 | streams, often found to be time-dependent. | |
615 | For more information on thin streams, see | |
616 | Documentation/networking/tcp-thin.txt | |
617 | Default: 0 | |
618 | ||
46d3ceab ED |
619 | tcp_limit_output_bytes - INTEGER |
620 | Controls TCP Small Queue limit per tcp socket. | |
621 | TCP bulk sender tends to increase packets in flight until it | |
622 | gets losses notifications. With SNDBUF autotuning, this can | |
623 | result in a large amount of packets queued in qdisc/device | |
624 | on the local machine, hurting latency of other flows, for | |
625 | typical pfifo_fast qdiscs. | |
626 | tcp_limit_output_bytes limits the number of bytes on qdisc | |
627 | or device to reduce artificial RTT/cwnd and reduce bufferbloat. | |
46d3ceab ED |
628 | Default: 131072 |
629 | ||
282f23c6 ED |
630 | tcp_challenge_ack_limit - INTEGER |
631 | Limits number of Challenge ACK sent per second, as recommended | |
632 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
633 | Default: 100 | |
634 | ||
95766fff HA |
635 | UDP variables: |
636 | ||
637 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
638 | Number of pages allowed for queueing by all UDP sockets. | |
639 | ||
640 | min: Below this number of pages UDP is not bothered about its | |
641 | memory appetite. When amount of memory allocated by UDP exceeds | |
642 | this number, UDP starts to moderate memory usage. | |
643 | ||
644 | pressure: This value was introduced to follow format of tcp_mem. | |
645 | ||
646 | max: Number of pages allowed for queueing by all UDP sockets. | |
647 | ||
648 | Default is calculated at boot time from amount of available memory. | |
649 | ||
650 | udp_rmem_min - INTEGER | |
651 | Minimal size of receive buffer used by UDP sockets in moderation. | |
652 | Each UDP socket is able to use the size for receiving data, even if | |
653 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 654 | Default: 1 page |
95766fff HA |
655 | |
656 | udp_wmem_min - INTEGER | |
657 | Minimal size of send buffer used by UDP sockets in moderation. | |
658 | Each UDP socket is able to use the size for sending data, even if | |
659 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
6539fefd | 660 | Default: 1 page |
95766fff | 661 | |
8802f616 PM |
662 | CIPSOv4 Variables: |
663 | ||
664 | cipso_cache_enable - BOOLEAN | |
665 | If set, enable additions to and lookups from the CIPSO label mapping | |
666 | cache. If unset, additions are ignored and lookups always result in a | |
667 | miss. However, regardless of the setting the cache is still | |
668 | invalidated when required when means you can safely toggle this on and | |
669 | off and the cache will always be "safe". | |
670 | Default: 1 | |
671 | ||
672 | cipso_cache_bucket_size - INTEGER | |
673 | The CIPSO label cache consists of a fixed size hash table with each | |
674 | hash bucket containing a number of cache entries. This variable limits | |
675 | the number of entries in each hash bucket; the larger the value the | |
676 | more CIPSO label mappings that can be cached. When the number of | |
677 | entries in a given hash bucket reaches this limit adding new entries | |
678 | causes the oldest entry in the bucket to be removed to make room. | |
679 | Default: 10 | |
680 | ||
681 | cipso_rbm_optfmt - BOOLEAN | |
682 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
683 | the CIPSO draft specification (see Documentation/netlabel for details). | |
684 | This means that when set the CIPSO tag will be padded with empty | |
685 | categories in order to make the packet data 32-bit aligned. | |
686 | Default: 0 | |
687 | ||
688 | cipso_rbm_structvalid - BOOLEAN | |
689 | If set, do a very strict check of the CIPSO option when | |
690 | ip_options_compile() is called. If unset, relax the checks done during | |
691 | ip_options_compile(). Either way is "safe" as errors are caught else | |
692 | where in the CIPSO processing code but setting this to 0 (False) should | |
693 | result in less work (i.e. it should be faster) but could cause problems | |
694 | with other implementations that require strict checking. | |
695 | Default: 0 | |
696 | ||
1da177e4 LT |
697 | IP Variables: |
698 | ||
699 | ip_local_port_range - 2 INTEGERS | |
700 | Defines the local port range that is used by TCP and UDP to | |
e18f5feb | 701 | choose the local port. The first number is the first, the |
5d6bd861 FLVC |
702 | second the last local port number. The default values are |
703 | 32768 and 61000 respectively. | |
1da177e4 | 704 | |
e3826f1e AW |
705 | ip_local_reserved_ports - list of comma separated ranges |
706 | Specify the ports which are reserved for known third-party | |
707 | applications. These ports will not be used by automatic port | |
708 | assignments (e.g. when calling connect() or bind() with port | |
709 | number 0). Explicit port allocation behavior is unchanged. | |
710 | ||
711 | The format used for both input and output is a comma separated | |
712 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
713 | 10). Writing to the file will clear all previously reserved | |
714 | ports and update the current list with the one given in the | |
715 | input. | |
716 | ||
717 | Note that ip_local_port_range and ip_local_reserved_ports | |
718 | settings are independent and both are considered by the kernel | |
719 | when determining which ports are available for automatic port | |
720 | assignments. | |
721 | ||
722 | You can reserve ports which are not in the current | |
723 | ip_local_port_range, e.g.: | |
724 | ||
725 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
726 | 32000 61000 | |
727 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
728 | 8080,9148 | |
729 | ||
730 | although this is redundant. However such a setting is useful | |
731 | if later the port range is changed to a value that will | |
732 | include the reserved ports. | |
733 | ||
734 | Default: Empty | |
735 | ||
1da177e4 LT |
736 | ip_nonlocal_bind - BOOLEAN |
737 | If set, allows processes to bind() to non-local IP addresses, | |
738 | which can be quite useful - but may break some applications. | |
739 | Default: 0 | |
740 | ||
741 | ip_dynaddr - BOOLEAN | |
742 | If set non-zero, enables support for dynamic addresses. | |
743 | If set to a non-zero value larger than 1, a kernel log | |
744 | message will be printed when dynamic address rewriting | |
745 | occurs. | |
746 | Default: 0 | |
747 | ||
e3d73bce CW |
748 | ip_early_demux - BOOLEAN |
749 | Optimize input packet processing down to one demux for | |
750 | certain kinds of local sockets. Currently we only do this | |
751 | for established TCP sockets. | |
752 | ||
753 | It may add an additional cost for pure routing workloads that | |
754 | reduces overall throughput, in such case you should disable it. | |
755 | Default: 1 | |
756 | ||
1da177e4 | 757 | icmp_echo_ignore_all - BOOLEAN |
7ce31246 DM |
758 | If set non-zero, then the kernel will ignore all ICMP ECHO |
759 | requests sent to it. | |
760 | Default: 0 | |
761 | ||
1da177e4 | 762 | icmp_echo_ignore_broadcasts - BOOLEAN |
7ce31246 DM |
763 | If set non-zero, then the kernel will ignore all ICMP ECHO and |
764 | TIMESTAMP requests sent to it via broadcast/multicast. | |
765 | Default: 1 | |
1da177e4 LT |
766 | |
767 | icmp_ratelimit - INTEGER | |
768 | Limit the maximal rates for sending ICMP packets whose type matches | |
769 | icmp_ratemask (see below) to specific targets. | |
6dbf4bca SH |
770 | 0 to disable any limiting, |
771 | otherwise the minimal space between responses in milliseconds. | |
772 | Default: 1000 | |
1da177e4 LT |
773 | |
774 | icmp_ratemask - INTEGER | |
775 | Mask made of ICMP types for which rates are being limited. | |
776 | Significant bits: IHGFEDCBA9876543210 | |
777 | Default mask: 0000001100000011000 (6168) | |
778 | ||
779 | Bit definitions (see include/linux/icmp.h): | |
780 | 0 Echo Reply | |
781 | 3 Destination Unreachable * | |
782 | 4 Source Quench * | |
783 | 5 Redirect | |
784 | 8 Echo Request | |
785 | B Time Exceeded * | |
786 | C Parameter Problem * | |
787 | D Timestamp Request | |
788 | E Timestamp Reply | |
789 | F Info Request | |
790 | G Info Reply | |
791 | H Address Mask Request | |
792 | I Address Mask Reply | |
793 | ||
794 | * These are rate limited by default (see default mask above) | |
795 | ||
796 | icmp_ignore_bogus_error_responses - BOOLEAN | |
797 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
798 | frames. Such violations are normally logged via a kernel warning. | |
799 | If this is set to TRUE, the kernel will not give such warnings, which | |
800 | will avoid log file clutter. | |
e8b265e8 | 801 | Default: 1 |
1da177e4 | 802 | |
95f7daf1 H |
803 | icmp_errors_use_inbound_ifaddr - BOOLEAN |
804 | ||
805 | If zero, icmp error messages are sent with the primary address of | |
806 | the exiting interface. | |
e18f5feb | 807 | |
95f7daf1 H |
808 | If non-zero, the message will be sent with the primary address of |
809 | the interface that received the packet that caused the icmp error. | |
810 | This is the behaviour network many administrators will expect from | |
811 | a router. And it can make debugging complicated network layouts | |
e18f5feb | 812 | much easier. |
95f7daf1 H |
813 | |
814 | Note that if no primary address exists for the interface selected, | |
815 | then the primary address of the first non-loopback interface that | |
d6bc8ac9 | 816 | has one will be used regardless of this setting. |
95f7daf1 H |
817 | |
818 | Default: 0 | |
819 | ||
1da177e4 LT |
820 | igmp_max_memberships - INTEGER |
821 | Change the maximum number of multicast groups we can subscribe to. | |
822 | Default: 20 | |
823 | ||
d67ef35f JE |
824 | Theoretical maximum value is bounded by having to send a membership |
825 | report in a single datagram (i.e. the report can't span multiple | |
826 | datagrams, or risk confusing the switch and leaving groups you don't | |
827 | intend to). | |
1da177e4 | 828 | |
d67ef35f JE |
829 | The number of supported groups 'M' is bounded by the number of group |
830 | report entries you can fit into a single datagram of 65535 bytes. | |
831 | ||
832 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
833 | ||
834 | Group records are variable length, with a minimum of 12 bytes. | |
835 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
836 | ||
837 | (65536-24) / 12 = 5459 | |
838 | ||
839 | The value 5459 assumes no IP header options, so in practice | |
840 | this number may be lower. | |
841 | ||
842 | conf/interface/* changes special settings per interface (where | |
843 | "interface" is the name of your network interface) | |
844 | ||
845 | conf/all/* is special, changes the settings for all interfaces | |
1da177e4 | 846 | |
a9fe8e29 HFS |
847 | igmp_qrv - INTEGER |
848 | Controls the IGMP query robustness variable (see RFC2236 8.1). | |
849 | Default: 2 (as specified by RFC2236 8.1) | |
850 | Minimum: 1 (as specified by RFC6636 4.5) | |
851 | ||
1da177e4 LT |
852 | log_martians - BOOLEAN |
853 | Log packets with impossible addresses to kernel log. | |
854 | log_martians for the interface will be enabled if at least one of | |
855 | conf/{all,interface}/log_martians is set to TRUE, | |
856 | it will be disabled otherwise | |
857 | ||
858 | accept_redirects - BOOLEAN | |
859 | Accept ICMP redirect messages. | |
860 | accept_redirects for the interface will be enabled if: | |
e18f5feb JDB |
861 | - both conf/{all,interface}/accept_redirects are TRUE in the case |
862 | forwarding for the interface is enabled | |
1da177e4 | 863 | or |
e18f5feb JDB |
864 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the |
865 | case forwarding for the interface is disabled | |
1da177e4 LT |
866 | accept_redirects for the interface will be disabled otherwise |
867 | default TRUE (host) | |
868 | FALSE (router) | |
869 | ||
870 | forwarding - BOOLEAN | |
871 | Enable IP forwarding on this interface. | |
872 | ||
873 | mc_forwarding - BOOLEAN | |
874 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
875 | and a multicast routing daemon is required. | |
e18f5feb JDB |
876 | conf/all/mc_forwarding must also be set to TRUE to enable multicast |
877 | routing for the interface | |
1da177e4 LT |
878 | |
879 | medium_id - INTEGER | |
880 | Integer value used to differentiate the devices by the medium they | |
881 | are attached to. Two devices can have different id values when | |
882 | the broadcast packets are received only on one of them. | |
883 | The default value 0 means that the device is the only interface | |
884 | to its medium, value of -1 means that medium is not known. | |
e18f5feb | 885 | |
1da177e4 LT |
886 | Currently, it is used to change the proxy_arp behavior: |
887 | the proxy_arp feature is enabled for packets forwarded between | |
888 | two devices attached to different media. | |
889 | ||
890 | proxy_arp - BOOLEAN | |
891 | Do proxy arp. | |
892 | proxy_arp for the interface will be enabled if at least one of | |
893 | conf/{all,interface}/proxy_arp is set to TRUE, | |
894 | it will be disabled otherwise | |
895 | ||
65324144 JDB |
896 | proxy_arp_pvlan - BOOLEAN |
897 | Private VLAN proxy arp. | |
898 | Basically allow proxy arp replies back to the same interface | |
899 | (from which the ARP request/solicitation was received). | |
900 | ||
901 | This is done to support (ethernet) switch features, like RFC | |
902 | 3069, where the individual ports are NOT allowed to | |
903 | communicate with each other, but they are allowed to talk to | |
904 | the upstream router. As described in RFC 3069, it is possible | |
905 | to allow these hosts to communicate through the upstream | |
906 | router by proxy_arp'ing. Don't need to be used together with | |
907 | proxy_arp. | |
908 | ||
909 | This technology is known by different names: | |
910 | In RFC 3069 it is called VLAN Aggregation. | |
911 | Cisco and Allied Telesyn call it Private VLAN. | |
912 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
913 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
914 | ||
1da177e4 LT |
915 | shared_media - BOOLEAN |
916 | Send(router) or accept(host) RFC1620 shared media redirects. | |
917 | Overrides ip_secure_redirects. | |
918 | shared_media for the interface will be enabled if at least one of | |
919 | conf/{all,interface}/shared_media is set to TRUE, | |
920 | it will be disabled otherwise | |
921 | default TRUE | |
922 | ||
923 | secure_redirects - BOOLEAN | |
924 | Accept ICMP redirect messages only for gateways, | |
925 | listed in default gateway list. | |
926 | secure_redirects for the interface will be enabled if at least one of | |
927 | conf/{all,interface}/secure_redirects is set to TRUE, | |
928 | it will be disabled otherwise | |
929 | default TRUE | |
930 | ||
931 | send_redirects - BOOLEAN | |
932 | Send redirects, if router. | |
933 | send_redirects for the interface will be enabled if at least one of | |
934 | conf/{all,interface}/send_redirects is set to TRUE, | |
935 | it will be disabled otherwise | |
936 | Default: TRUE | |
937 | ||
938 | bootp_relay - BOOLEAN | |
939 | Accept packets with source address 0.b.c.d destined | |
940 | not to this host as local ones. It is supposed, that | |
941 | BOOTP relay daemon will catch and forward such packets. | |
942 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
943 | for the interface | |
944 | default FALSE | |
945 | Not Implemented Yet. | |
946 | ||
947 | accept_source_route - BOOLEAN | |
948 | Accept packets with SRR option. | |
949 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
950 | with SRR option on the interface | |
951 | default TRUE (router) | |
952 | FALSE (host) | |
953 | ||
8153a10c | 954 | accept_local - BOOLEAN |
72b126a4 SB |
955 | Accept packets with local source addresses. In combination with |
956 | suitable routing, this can be used to direct packets between two | |
957 | local interfaces over the wire and have them accepted properly. | |
8153a10c PM |
958 | default FALSE |
959 | ||
d0daebc3 TG |
960 | route_localnet - BOOLEAN |
961 | Do not consider loopback addresses as martian source or destination | |
962 | while routing. This enables the use of 127/8 for local routing purposes. | |
963 | default FALSE | |
964 | ||
c1cf8422 | 965 | rp_filter - INTEGER |
1da177e4 | 966 | 0 - No source validation. |
c1cf8422 SH |
967 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path |
968 | Each incoming packet is tested against the FIB and if the interface | |
969 | is not the best reverse path the packet check will fail. | |
970 | By default failed packets are discarded. | |
971 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
972 | Each incoming packet's source address is also tested against the FIB | |
973 | and if the source address is not reachable via any interface | |
974 | the packet check will fail. | |
975 | ||
e18f5feb | 976 | Current recommended practice in RFC3704 is to enable strict mode |
bf869c30 | 977 | to prevent IP spoofing from DDos attacks. If using asymmetric routing |
e18f5feb | 978 | or other complicated routing, then loose mode is recommended. |
c1cf8422 | 979 | |
1f5865e7 SW |
980 | The max value from conf/{all,interface}/rp_filter is used |
981 | when doing source validation on the {interface}. | |
1da177e4 LT |
982 | |
983 | Default value is 0. Note that some distributions enable it | |
984 | in startup scripts. | |
985 | ||
986 | arp_filter - BOOLEAN | |
987 | 1 - Allows you to have multiple network interfaces on the same | |
988 | subnet, and have the ARPs for each interface be answered | |
989 | based on whether or not the kernel would route a packet from | |
990 | the ARP'd IP out that interface (therefore you must use source | |
991 | based routing for this to work). In other words it allows control | |
992 | of which cards (usually 1) will respond to an arp request. | |
993 | ||
994 | 0 - (default) The kernel can respond to arp requests with addresses | |
995 | from other interfaces. This may seem wrong but it usually makes | |
996 | sense, because it increases the chance of successful communication. | |
997 | IP addresses are owned by the complete host on Linux, not by | |
998 | particular interfaces. Only for more complex setups like load- | |
999 | balancing, does this behaviour cause problems. | |
1000 | ||
1001 | arp_filter for the interface will be enabled if at least one of | |
1002 | conf/{all,interface}/arp_filter is set to TRUE, | |
1003 | it will be disabled otherwise | |
1004 | ||
1005 | arp_announce - INTEGER | |
1006 | Define different restriction levels for announcing the local | |
1007 | source IP address from IP packets in ARP requests sent on | |
1008 | interface: | |
1009 | 0 - (default) Use any local address, configured on any interface | |
1010 | 1 - Try to avoid local addresses that are not in the target's | |
1011 | subnet for this interface. This mode is useful when target | |
1012 | hosts reachable via this interface require the source IP | |
1013 | address in ARP requests to be part of their logical network | |
1014 | configured on the receiving interface. When we generate the | |
1015 | request we will check all our subnets that include the | |
1016 | target IP and will preserve the source address if it is from | |
1017 | such subnet. If there is no such subnet we select source | |
1018 | address according to the rules for level 2. | |
1019 | 2 - Always use the best local address for this target. | |
1020 | In this mode we ignore the source address in the IP packet | |
1021 | and try to select local address that we prefer for talks with | |
1022 | the target host. Such local address is selected by looking | |
1023 | for primary IP addresses on all our subnets on the outgoing | |
1024 | interface that include the target IP address. If no suitable | |
1025 | local address is found we select the first local address | |
1026 | we have on the outgoing interface or on all other interfaces, | |
1027 | with the hope we will receive reply for our request and | |
1028 | even sometimes no matter the source IP address we announce. | |
1029 | ||
1030 | The max value from conf/{all,interface}/arp_announce is used. | |
1031 | ||
1032 | Increasing the restriction level gives more chance for | |
1033 | receiving answer from the resolved target while decreasing | |
1034 | the level announces more valid sender's information. | |
1035 | ||
1036 | arp_ignore - INTEGER | |
1037 | Define different modes for sending replies in response to | |
1038 | received ARP requests that resolve local target IP addresses: | |
1039 | 0 - (default): reply for any local target IP address, configured | |
1040 | on any interface | |
1041 | 1 - reply only if the target IP address is local address | |
1042 | configured on the incoming interface | |
1043 | 2 - reply only if the target IP address is local address | |
1044 | configured on the incoming interface and both with the | |
1045 | sender's IP address are part from same subnet on this interface | |
1046 | 3 - do not reply for local addresses configured with scope host, | |
1047 | only resolutions for global and link addresses are replied | |
1048 | 4-7 - reserved | |
1049 | 8 - do not reply for all local addresses | |
1050 | ||
1051 | The max value from conf/{all,interface}/arp_ignore is used | |
1052 | when ARP request is received on the {interface} | |
1053 | ||
eefef1cf SH |
1054 | arp_notify - BOOLEAN |
1055 | Define mode for notification of address and device changes. | |
1056 | 0 - (default): do nothing | |
3f8dc236 | 1057 | 1 - Generate gratuitous arp requests when device is brought up |
eefef1cf SH |
1058 | or hardware address changes. |
1059 | ||
c1b1bce8 | 1060 | arp_accept - BOOLEAN |
6d955180 OP |
1061 | Define behavior for gratuitous ARP frames who's IP is not |
1062 | already present in the ARP table: | |
1063 | 0 - don't create new entries in the ARP table | |
1064 | 1 - create new entries in the ARP table | |
1065 | ||
1066 | Both replies and requests type gratuitous arp will trigger the | |
1067 | ARP table to be updated, if this setting is on. | |
1068 | ||
1069 | If the ARP table already contains the IP address of the | |
1070 | gratuitous arp frame, the arp table will be updated regardless | |
1071 | if this setting is on or off. | |
1072 | ||
c1b1bce8 | 1073 | |
1da177e4 LT |
1074 | app_solicit - INTEGER |
1075 | The maximum number of probes to send to the user space ARP daemon | |
1076 | via netlink before dropping back to multicast probes (see | |
1077 | mcast_solicit). Defaults to 0. | |
1078 | ||
1079 | disable_policy - BOOLEAN | |
1080 | Disable IPSEC policy (SPD) for this interface | |
1081 | ||
1082 | disable_xfrm - BOOLEAN | |
1083 | Disable IPSEC encryption on this interface, whatever the policy | |
1084 | ||
fc4eba58 HFS |
1085 | igmpv2_unsolicited_report_interval - INTEGER |
1086 | The interval in milliseconds in which the next unsolicited | |
1087 | IGMPv1 or IGMPv2 report retransmit will take place. | |
1088 | Default: 10000 (10 seconds) | |
1da177e4 | 1089 | |
fc4eba58 HFS |
1090 | igmpv3_unsolicited_report_interval - INTEGER |
1091 | The interval in milliseconds in which the next unsolicited | |
1092 | IGMPv3 report retransmit will take place. | |
1093 | Default: 1000 (1 seconds) | |
1da177e4 | 1094 | |
d922e1cb MS |
1095 | promote_secondaries - BOOLEAN |
1096 | When a primary IP address is removed from this interface | |
1097 | promote a corresponding secondary IP address instead of | |
1098 | removing all the corresponding secondary IP addresses. | |
1099 | ||
1100 | ||
1da177e4 LT |
1101 | tag - INTEGER |
1102 | Allows you to write a number, which can be used as required. | |
1103 | Default value is 0. | |
1104 | ||
1da177e4 LT |
1105 | Alexey Kuznetsov. |
1106 | kuznet@ms2.inr.ac.ru | |
1107 | ||
1108 | Updated by: | |
1109 | Andi Kleen | |
1110 | ak@muc.de | |
1111 | Nicolas Delon | |
1112 | delon.nicolas@wanadoo.fr | |
1113 | ||
1114 | ||
1115 | ||
1116 | ||
1117 | /proc/sys/net/ipv6/* Variables: | |
1118 | ||
1119 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1120 | apply to IPv6 [XXX?]. | |
1121 | ||
1122 | bindv6only - BOOLEAN | |
1123 | Default value for IPV6_V6ONLY socket option, | |
e18f5feb | 1124 | which restricts use of the IPv6 socket to IPv6 communication |
1da177e4 LT |
1125 | only. |
1126 | TRUE: disable IPv4-mapped address feature | |
1127 | FALSE: enable IPv4-mapped address feature | |
1128 | ||
d5c073ca | 1129 | Default: FALSE (as specified in RFC3493) |
1da177e4 | 1130 | |
6444f72b FF |
1131 | flowlabel_consistency - BOOLEAN |
1132 | Protect the consistency (and unicity) of flow label. | |
1133 | You have to disable it to use IPV6_FL_F_REFLECT flag on the | |
1134 | flow label manager. | |
1135 | TRUE: enabled | |
1136 | FALSE: disabled | |
1137 | Default: TRUE | |
1138 | ||
cb1ce2ef TH |
1139 | auto_flowlabels - BOOLEAN |
1140 | Automatically generate flow labels based based on a flow hash | |
1141 | of the packet. This allows intermediate devices, such as routers, | |
1142 | to idenfify packet flows for mechanisms like Equal Cost Multipath | |
1143 | Routing (see RFC 6438). | |
1144 | TRUE: enabled | |
1145 | FALSE: disabled | |
1146 | Default: false | |
1147 | ||
509aba3b FLB |
1148 | anycast_src_echo_reply - BOOLEAN |
1149 | Controls the use of anycast addresses as source addresses for ICMPv6 | |
1150 | echo reply | |
1151 | TRUE: enabled | |
1152 | FALSE: disabled | |
1153 | Default: FALSE | |
1154 | ||
2f711939 HFS |
1155 | mld_qrv - INTEGER |
1156 | Controls the MLD query robustness variable (see RFC3810 9.1). | |
1157 | Default: 2 (as specified by RFC3810 9.1) | |
1158 | Minimum: 1 (as specified by RFC6636 4.5) | |
1159 | ||
1da177e4 LT |
1160 | IPv6 Fragmentation: |
1161 | ||
1162 | ip6frag_high_thresh - INTEGER | |
e18f5feb | 1163 | Maximum memory used to reassemble IPv6 fragments. When |
1da177e4 LT |
1164 | ip6frag_high_thresh bytes of memory is allocated for this purpose, |
1165 | the fragment handler will toss packets until ip6frag_low_thresh | |
1166 | is reached. | |
e18f5feb | 1167 | |
1da177e4 | 1168 | ip6frag_low_thresh - INTEGER |
e18f5feb | 1169 | See ip6frag_high_thresh |
1da177e4 LT |
1170 | |
1171 | ip6frag_time - INTEGER | |
1172 | Time in seconds to keep an IPv6 fragment in memory. | |
1173 | ||
1da177e4 LT |
1174 | conf/default/*: |
1175 | Change the interface-specific default settings. | |
1176 | ||
1177 | ||
1178 | conf/all/*: | |
e18f5feb | 1179 | Change all the interface-specific settings. |
1da177e4 LT |
1180 | |
1181 | [XXX: Other special features than forwarding?] | |
1182 | ||
1183 | conf/all/forwarding - BOOLEAN | |
e18f5feb | 1184 | Enable global IPv6 forwarding between all interfaces. |
1da177e4 | 1185 | |
e18f5feb | 1186 | IPv4 and IPv6 work differently here; e.g. netfilter must be used |
1da177e4 LT |
1187 | to control which interfaces may forward packets and which not. |
1188 | ||
e18f5feb | 1189 | This also sets all interfaces' Host/Router setting |
1da177e4 LT |
1190 | 'forwarding' to the specified value. See below for details. |
1191 | ||
1192 | This referred to as global forwarding. | |
1193 | ||
fbea49e1 YH |
1194 | proxy_ndp - BOOLEAN |
1195 | Do proxy ndp. | |
1196 | ||
1da177e4 LT |
1197 | conf/interface/*: |
1198 | Change special settings per interface. | |
1199 | ||
e18f5feb | 1200 | The functional behaviour for certain settings is different |
1da177e4 LT |
1201 | depending on whether local forwarding is enabled or not. |
1202 | ||
605b91c8 | 1203 | accept_ra - INTEGER |
1da177e4 | 1204 | Accept Router Advertisements; autoconfigure using them. |
e18f5feb | 1205 | |
026359bc TA |
1206 | It also determines whether or not to transmit Router |
1207 | Solicitations. If and only if the functional setting is to | |
1208 | accept Router Advertisements, Router Solicitations will be | |
1209 | transmitted. | |
1210 | ||
ae8abfa0 TG |
1211 | Possible values are: |
1212 | 0 Do not accept Router Advertisements. | |
1213 | 1 Accept Router Advertisements if forwarding is disabled. | |
1214 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1215 | even if forwarding is enabled. | |
1216 | ||
1da177e4 LT |
1217 | Functional default: enabled if local forwarding is disabled. |
1218 | disabled if local forwarding is enabled. | |
1219 | ||
65f5c7c1 YH |
1220 | accept_ra_defrtr - BOOLEAN |
1221 | Learn default router in Router Advertisement. | |
1222 | ||
1223 | Functional default: enabled if accept_ra is enabled. | |
1224 | disabled if accept_ra is disabled. | |
1225 | ||
d9333196 BG |
1226 | accept_ra_from_local - BOOLEAN |
1227 | Accept RA with source-address that is found on local machine | |
1228 | if the RA is otherwise proper and able to be accepted. | |
1229 | Default is to NOT accept these as it may be an un-intended | |
1230 | network loop. | |
1231 | ||
1232 | Functional default: | |
1233 | enabled if accept_ra_from_local is enabled | |
1234 | on a specific interface. | |
1235 | disabled if accept_ra_from_local is disabled | |
1236 | on a specific interface. | |
1237 | ||
c4fd30eb | 1238 | accept_ra_pinfo - BOOLEAN |
2fe0ae78 | 1239 | Learn Prefix Information in Router Advertisement. |
c4fd30eb YH |
1240 | |
1241 | Functional default: enabled if accept_ra is enabled. | |
1242 | disabled if accept_ra is disabled. | |
1243 | ||
09c884d4 YH |
1244 | accept_ra_rt_info_max_plen - INTEGER |
1245 | Maximum prefix length of Route Information in RA. | |
1246 | ||
1247 | Route Information w/ prefix larger than or equal to this | |
1248 | variable shall be ignored. | |
1249 | ||
1250 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1251 | -1 if accept_ra_rtr_pref is disabled. | |
1252 | ||
930d6ff2 YH |
1253 | accept_ra_rtr_pref - BOOLEAN |
1254 | Accept Router Preference in RA. | |
1255 | ||
1256 | Functional default: enabled if accept_ra is enabled. | |
1257 | disabled if accept_ra is disabled. | |
1258 | ||
1da177e4 LT |
1259 | accept_redirects - BOOLEAN |
1260 | Accept Redirects. | |
1261 | ||
1262 | Functional default: enabled if local forwarding is disabled. | |
1263 | disabled if local forwarding is enabled. | |
1264 | ||
0bcbc926 YH |
1265 | accept_source_route - INTEGER |
1266 | Accept source routing (routing extension header). | |
1267 | ||
bb4dbf9e | 1268 | >= 0: Accept only routing header type 2. |
0bcbc926 YH |
1269 | < 0: Do not accept routing header. |
1270 | ||
1271 | Default: 0 | |
1272 | ||
1da177e4 | 1273 | autoconf - BOOLEAN |
e18f5feb | 1274 | Autoconfigure addresses using Prefix Information in Router |
1da177e4 LT |
1275 | Advertisements. |
1276 | ||
c4fd30eb YH |
1277 | Functional default: enabled if accept_ra_pinfo is enabled. |
1278 | disabled if accept_ra_pinfo is disabled. | |
1da177e4 LT |
1279 | |
1280 | dad_transmits - INTEGER | |
1281 | The amount of Duplicate Address Detection probes to send. | |
1282 | Default: 1 | |
e18f5feb | 1283 | |
605b91c8 | 1284 | forwarding - INTEGER |
e18f5feb | 1285 | Configure interface-specific Host/Router behaviour. |
1da177e4 | 1286 | |
e18f5feb | 1287 | Note: It is recommended to have the same setting on all |
1da177e4 LT |
1288 | interfaces; mixed router/host scenarios are rather uncommon. |
1289 | ||
ae8abfa0 TG |
1290 | Possible values are: |
1291 | 0 Forwarding disabled | |
1292 | 1 Forwarding enabled | |
ae8abfa0 TG |
1293 | |
1294 | FALSE (0): | |
1da177e4 LT |
1295 | |
1296 | By default, Host behaviour is assumed. This means: | |
1297 | ||
1298 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
026359bc TA |
1299 | 2. If accept_ra is TRUE (default), transmit Router |
1300 | Solicitations. | |
e18f5feb | 1301 | 3. If accept_ra is TRUE (default), accept Router |
1da177e4 LT |
1302 | Advertisements (and do autoconfiguration). |
1303 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1304 | ||
ae8abfa0 | 1305 | TRUE (1): |
1da177e4 | 1306 | |
e18f5feb | 1307 | If local forwarding is enabled, Router behaviour is assumed. |
1da177e4 LT |
1308 | This means exactly the reverse from the above: |
1309 | ||
1310 | 1. IsRouter flag is set in Neighbour Advertisements. | |
026359bc | 1311 | 2. Router Solicitations are not sent unless accept_ra is 2. |
ae8abfa0 | 1312 | 3. Router Advertisements are ignored unless accept_ra is 2. |
1da177e4 LT |
1313 | 4. Redirects are ignored. |
1314 | ||
ae8abfa0 TG |
1315 | Default: 0 (disabled) if global forwarding is disabled (default), |
1316 | otherwise 1 (enabled). | |
1da177e4 LT |
1317 | |
1318 | hop_limit - INTEGER | |
1319 | Default Hop Limit to set. | |
1320 | Default: 64 | |
1321 | ||
1322 | mtu - INTEGER | |
1323 | Default Maximum Transfer Unit | |
1324 | Default: 1280 (IPv6 required minimum) | |
1325 | ||
52e16356 YH |
1326 | router_probe_interval - INTEGER |
1327 | Minimum interval (in seconds) between Router Probing described | |
1328 | in RFC4191. | |
1329 | ||
1330 | Default: 60 | |
1331 | ||
1da177e4 LT |
1332 | router_solicitation_delay - INTEGER |
1333 | Number of seconds to wait after interface is brought up | |
1334 | before sending Router Solicitations. | |
1335 | Default: 1 | |
1336 | ||
1337 | router_solicitation_interval - INTEGER | |
1338 | Number of seconds to wait between Router Solicitations. | |
1339 | Default: 4 | |
1340 | ||
1341 | router_solicitations - INTEGER | |
e18f5feb | 1342 | Number of Router Solicitations to send until assuming no |
1da177e4 LT |
1343 | routers are present. |
1344 | Default: 3 | |
1345 | ||
1346 | use_tempaddr - INTEGER | |
1347 | Preference for Privacy Extensions (RFC3041). | |
1348 | <= 0 : disable Privacy Extensions | |
1349 | == 1 : enable Privacy Extensions, but prefer public | |
1350 | addresses over temporary addresses. | |
1351 | > 1 : enable Privacy Extensions and prefer temporary | |
1352 | addresses over public addresses. | |
1353 | Default: 0 (for most devices) | |
1354 | -1 (for point-to-point devices and loopback devices) | |
1355 | ||
1356 | temp_valid_lft - INTEGER | |
1357 | valid lifetime (in seconds) for temporary addresses. | |
1358 | Default: 604800 (7 days) | |
1359 | ||
1360 | temp_prefered_lft - INTEGER | |
1361 | Preferred lifetime (in seconds) for temporary addresses. | |
1362 | Default: 86400 (1 day) | |
1363 | ||
1364 | max_desync_factor - INTEGER | |
1365 | Maximum value for DESYNC_FACTOR, which is a random value | |
e18f5feb | 1366 | that ensures that clients don't synchronize with each |
1da177e4 LT |
1367 | other and generate new addresses at exactly the same time. |
1368 | value is in seconds. | |
1369 | Default: 600 | |
e18f5feb | 1370 | |
1da177e4 LT |
1371 | regen_max_retry - INTEGER |
1372 | Number of attempts before give up attempting to generate | |
1373 | valid temporary addresses. | |
1374 | Default: 5 | |
1375 | ||
1376 | max_addresses - INTEGER | |
e79dc484 BH |
1377 | Maximum number of autoconfigured addresses per interface. Setting |
1378 | to zero disables the limitation. It is not recommended to set this | |
1379 | value too large (or to zero) because it would be an easy way to | |
1380 | crash the kernel by allowing too many addresses to be created. | |
1da177e4 LT |
1381 | Default: 16 |
1382 | ||
778d80be | 1383 | disable_ipv6 - BOOLEAN |
9bdd8d40 BH |
1384 | Disable IPv6 operation. If accept_dad is set to 2, this value |
1385 | will be dynamically set to TRUE if DAD fails for the link-local | |
1386 | address. | |
778d80be YH |
1387 | Default: FALSE (enable IPv6 operation) |
1388 | ||
56d417b1 BH |
1389 | When this value is changed from 1 to 0 (IPv6 is being enabled), |
1390 | it will dynamically create a link-local address on the given | |
1391 | interface and start Duplicate Address Detection, if necessary. | |
1392 | ||
1393 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1394 | it will dynamically delete all address on the given interface. | |
1395 | ||
1b34be74 YH |
1396 | accept_dad - INTEGER |
1397 | Whether to accept DAD (Duplicate Address Detection). | |
1398 | 0: Disable DAD | |
1399 | 1: Enable DAD (default) | |
1400 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1401 | link-local address has been found. | |
1402 | ||
f7734fdf OP |
1403 | force_tllao - BOOLEAN |
1404 | Enable sending the target link-layer address option even when | |
1405 | responding to a unicast neighbor solicitation. | |
1406 | Default: FALSE | |
1407 | ||
1408 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1409 | ||
1410 | "The option MUST be included for multicast solicitations in order to | |
1411 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1412 | does not have a cache entry to return a Neighbor Advertisements | |
1413 | message. When responding to unicast solicitations, the option can be | |
1414 | omitted since the sender of the solicitation has the correct link- | |
1415 | layer address; otherwise it would not have be able to send the unicast | |
1416 | solicitation in the first place. However, including the link-layer | |
1417 | address in this case adds little overhead and eliminates a potential | |
1418 | race condition where the sender deletes the cached link-layer address | |
1419 | prior to receiving a response to a previous solicitation." | |
1420 | ||
db2b620a HFS |
1421 | ndisc_notify - BOOLEAN |
1422 | Define mode for notification of address and device changes. | |
1423 | 0 - (default): do nothing | |
1424 | 1 - Generate unsolicited neighbour advertisements when device is brought | |
1425 | up or hardware address changes. | |
1426 | ||
fc4eba58 HFS |
1427 | mldv1_unsolicited_report_interval - INTEGER |
1428 | The interval in milliseconds in which the next unsolicited | |
1429 | MLDv1 report retransmit will take place. | |
1430 | Default: 10000 (10 seconds) | |
1431 | ||
1432 | mldv2_unsolicited_report_interval - INTEGER | |
1433 | The interval in milliseconds in which the next unsolicited | |
1434 | MLDv2 report retransmit will take place. | |
1435 | Default: 1000 (1 second) | |
1436 | ||
f2127810 DB |
1437 | force_mld_version - INTEGER |
1438 | 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed | |
1439 | 1 - Enforce to use MLD version 1 | |
1440 | 2 - Enforce to use MLD version 2 | |
1441 | ||
b800c3b9 HFS |
1442 | suppress_frag_ndisc - INTEGER |
1443 | Control RFC 6980 (Security Implications of IPv6 Fragmentation | |
1444 | with IPv6 Neighbor Discovery) behavior: | |
1445 | 1 - (default) discard fragmented neighbor discovery packets | |
1446 | 0 - allow fragmented neighbor discovery packets | |
1447 | ||
1da177e4 LT |
1448 | icmp/*: |
1449 | ratelimit - INTEGER | |
1450 | Limit the maximal rates for sending ICMPv6 packets. | |
6dbf4bca SH |
1451 | 0 to disable any limiting, |
1452 | otherwise the minimal space between responses in milliseconds. | |
1453 | Default: 1000 | |
1da177e4 LT |
1454 | |
1455 | ||
1456 | IPv6 Update by: | |
1457 | Pekka Savola <pekkas@netcore.fi> | |
1458 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1459 | ||
1460 | ||
1461 | /proc/sys/net/bridge/* Variables: | |
1462 | ||
1463 | bridge-nf-call-arptables - BOOLEAN | |
1464 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1465 | 0 : disable this. | |
1466 | Default: 1 | |
1467 | ||
1468 | bridge-nf-call-iptables - BOOLEAN | |
1469 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1470 | 0 : disable this. | |
1471 | Default: 1 | |
1472 | ||
1473 | bridge-nf-call-ip6tables - BOOLEAN | |
1474 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1475 | 0 : disable this. | |
1476 | Default: 1 | |
1477 | ||
1478 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
516299d2 MM |
1479 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. |
1480 | 0 : disable this. | |
4981682c | 1481 | Default: 0 |
516299d2 MM |
1482 | |
1483 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1484 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1da177e4 | 1485 | 0 : disable this. |
4981682c | 1486 | Default: 0 |
1da177e4 | 1487 | |
4981682c PNA |
1488 | bridge-nf-pass-vlan-input-dev - BOOLEAN |
1489 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1490 | interface on the bridge and set the netfilter input device to the vlan. | |
1491 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1492 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1493 | vlan interface is found, or this switch is off, the input device is | |
1494 | set to the bridge interface. | |
1495 | 0: disable bridge netfilter vlan interface lookup. | |
1496 | Default: 0 | |
1da177e4 | 1497 | |
32e8d494 VY |
1498 | proc/sys/net/sctp/* Variables: |
1499 | ||
1500 | addip_enable - BOOLEAN | |
1501 | Enable or disable extension of Dynamic Address Reconfiguration | |
1502 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1503 | the ability to dynamically add and remove new addresses for the SCTP | |
1504 | associations. | |
1505 | ||
1506 | 1: Enable extension. | |
1507 | ||
1508 | 0: Disable extension. | |
1509 | ||
1510 | Default: 0 | |
1511 | ||
1512 | addip_noauth_enable - BOOLEAN | |
1513 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1514 | authentication to protect the operations of adding or removing new | |
1515 | addresses. This requirement is mandated so that unauthorized hosts | |
1516 | would not be able to hijack associations. However, older | |
1517 | implementations may not have implemented this requirement while | |
1518 | allowing the ADD-IP extension. For reasons of interoperability, | |
1519 | we provide this variable to control the enforcement of the | |
1520 | authentication requirement. | |
1521 | ||
1522 | 1: Allow ADD-IP extension to be used without authentication. This | |
1523 | should only be set in a closed environment for interoperability | |
1524 | with older implementations. | |
1525 | ||
1526 | 0: Enforce the authentication requirement | |
1527 | ||
1528 | Default: 0 | |
1529 | ||
1530 | auth_enable - BOOLEAN | |
1531 | Enable or disable Authenticated Chunks extension. This extension | |
1532 | provides the ability to send and receive authenticated chunks and is | |
1533 | required for secure operation of Dynamic Address Reconfiguration | |
1534 | (ADD-IP) extension. | |
1535 | ||
1536 | 1: Enable this extension. | |
1537 | 0: Disable this extension. | |
1538 | ||
1539 | Default: 0 | |
1540 | ||
1541 | prsctp_enable - BOOLEAN | |
1542 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1543 | is used to notify peers that a given DATA should no longer be expected. | |
1544 | ||
1545 | 1: Enable extension | |
1546 | 0: Disable | |
1547 | ||
1548 | Default: 1 | |
1549 | ||
1550 | max_burst - INTEGER | |
1551 | The limit of the number of new packets that can be initially sent. It | |
1552 | controls how bursty the generated traffic can be. | |
1553 | ||
1554 | Default: 4 | |
1555 | ||
1556 | association_max_retrans - INTEGER | |
1557 | Set the maximum number for retransmissions that an association can | |
1558 | attempt deciding that the remote end is unreachable. If this value | |
1559 | is exceeded, the association is terminated. | |
1560 | ||
1561 | Default: 10 | |
1562 | ||
1563 | max_init_retransmits - INTEGER | |
1564 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1565 | that an association will attempt before declaring the destination | |
1566 | unreachable and terminating. | |
1567 | ||
1568 | Default: 8 | |
1569 | ||
1570 | path_max_retrans - INTEGER | |
1571 | The maximum number of retransmissions that will be attempted on a given | |
1572 | path. Once this threshold is exceeded, the path is considered | |
1573 | unreachable, and new traffic will use a different path when the | |
1574 | association is multihomed. | |
1575 | ||
1576 | Default: 5 | |
1577 | ||
5aa93bcf NH |
1578 | pf_retrans - INTEGER |
1579 | The number of retransmissions that will be attempted on a given path | |
1580 | before traffic is redirected to an alternate transport (should one | |
1581 | exist). Note this is distinct from path_max_retrans, as a path that | |
1582 | passes the pf_retrans threshold can still be used. Its only | |
1583 | deprioritized when a transmission path is selected by the stack. This | |
1584 | setting is primarily used to enable fast failover mechanisms without | |
1585 | having to reduce path_max_retrans to a very low value. See: | |
1586 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
1587 | for details. Note also that a value of pf_retrans > path_max_retrans | |
1588 | disables this feature | |
1589 | ||
1590 | Default: 0 | |
1591 | ||
32e8d494 VY |
1592 | rto_initial - INTEGER |
1593 | The initial round trip timeout value in milliseconds that will be used | |
1594 | in calculating round trip times. This is the initial time interval | |
1595 | for retransmissions. | |
1596 | ||
1597 | Default: 3000 | |
1da177e4 | 1598 | |
32e8d494 VY |
1599 | rto_max - INTEGER |
1600 | The maximum value (in milliseconds) of the round trip timeout. This | |
1601 | is the largest time interval that can elapse between retransmissions. | |
1602 | ||
1603 | Default: 60000 | |
1604 | ||
1605 | rto_min - INTEGER | |
1606 | The minimum value (in milliseconds) of the round trip timeout. This | |
1607 | is the smallest time interval the can elapse between retransmissions. | |
1608 | ||
1609 | Default: 1000 | |
1610 | ||
1611 | hb_interval - INTEGER | |
1612 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1613 | are sent at the specified interval on idle paths to probe the state of | |
1614 | a given path between 2 associations. | |
1615 | ||
1616 | Default: 30000 | |
1617 | ||
1618 | sack_timeout - INTEGER | |
1619 | The amount of time (in milliseconds) that the implementation will wait | |
1620 | to send a SACK. | |
1621 | ||
1622 | Default: 200 | |
1623 | ||
1624 | valid_cookie_life - INTEGER | |
1625 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1626 | is used during association establishment. | |
1627 | ||
1628 | Default: 60000 | |
1629 | ||
1630 | cookie_preserve_enable - BOOLEAN | |
1631 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1632 | that is used during the establishment phase of SCTP association | |
1633 | ||
1634 | 1: Enable cookie lifetime extension. | |
1635 | 0: Disable | |
1636 | ||
1637 | Default: 1 | |
1638 | ||
3c68198e NH |
1639 | cookie_hmac_alg - STRING |
1640 | Select the hmac algorithm used when generating the cookie value sent by | |
1641 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
1642 | Valid values are: | |
1643 | * md5 | |
1644 | * sha1 | |
1645 | * none | |
1646 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
3b09adcb | 1647 | configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and |
3c68198e NH |
1648 | CONFIG_CRYPTO_SHA1). |
1649 | ||
1650 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
1651 | available, else none. | |
1652 | ||
32e8d494 VY |
1653 | rcvbuf_policy - INTEGER |
1654 | Determines if the receive buffer is attributed to the socket or to | |
1655 | association. SCTP supports the capability to create multiple | |
1656 | associations on a single socket. When using this capability, it is | |
1657 | possible that a single stalled association that's buffering a lot | |
1658 | of data may block other associations from delivering their data by | |
1659 | consuming all of the receive buffer space. To work around this, | |
1660 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1661 | to each association instead of the socket. This prevents the described | |
1662 | blocking. | |
1663 | ||
1664 | 1: rcvbuf space is per association | |
3b09adcb | 1665 | 0: rcvbuf space is per socket |
32e8d494 VY |
1666 | |
1667 | Default: 0 | |
1668 | ||
1669 | sndbuf_policy - INTEGER | |
1670 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1671 | ||
1672 | 1: Send buffer is tracked per association | |
1673 | 0: Send buffer is tracked per socket. | |
1674 | ||
1675 | Default: 0 | |
1676 | ||
1677 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1678 | Number of pages allowed for queueing by all SCTP sockets. | |
1679 | ||
1680 | min: Below this number of pages SCTP is not bothered about its | |
1681 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1682 | this number, SCTP starts to moderate memory usage. | |
1683 | ||
1684 | pressure: This value was introduced to follow format of tcp_mem. | |
1685 | ||
1686 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1687 | ||
1688 | Default is calculated at boot time from amount of available memory. | |
1689 | ||
1690 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b MM |
1691 | Only the first value ("min") is used, "default" and "max" are |
1692 | ignored. | |
1693 | ||
1694 | min: Minimal size of receive buffer used by SCTP socket. | |
1695 | It is guaranteed to each SCTP socket (but not association) even | |
1696 | under moderate memory pressure. | |
1697 | ||
1698 | Default: 1 page | |
32e8d494 VY |
1699 | |
1700 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
a6e1204b | 1701 | Currently this tunable has no effect. |
32e8d494 | 1702 | |
72388433 BD |
1703 | addr_scope_policy - INTEGER |
1704 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
1705 | ||
1706 | 0 - Disable IPv4 address scoping | |
1707 | 1 - Enable IPv4 address scoping | |
1708 | 2 - Follow draft but allow IPv4 private addresses | |
1709 | 3 - Follow draft but allow IPv4 link local addresses | |
1710 | ||
1711 | Default: 1 | |
1712 | ||
1da177e4 | 1713 | |
4edc2f34 | 1714 | /proc/sys/net/core/* |
c60f6aa8 | 1715 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. |
705efc3b | 1716 | |
4edc2f34 SH |
1717 | |
1718 | /proc/sys/net/unix/* | |
705efc3b WT |
1719 | max_dgram_qlen - INTEGER |
1720 | The maximum length of dgram socket receive queue | |
1721 | ||
1722 | Default: 10 | |
1723 | ||
1724 | ||
1725 | UNDOCUMENTED: | |
4edc2f34 SH |
1726 | |
1727 | /proc/sys/net/irda/* | |
1728 | fast_poll_increase FIXME | |
1729 | warn_noreply_time FIXME | |
1730 | discovery_slots FIXME | |
1731 | slot_timeout FIXME | |
1732 | max_baud_rate FIXME | |
1733 | discovery_timeout FIXME | |
1734 | lap_keepalive_time FIXME | |
1735 | max_noreply_time FIXME | |
1736 | max_tx_data_size FIXME | |
1737 | max_tx_window FIXME | |
1738 | min_tx_turn_time FIXME |