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Commit | Line | Data |
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1 | /proc/sys/net/ipv4/* Variables: | |
2 | ||
3 | ip_forward - BOOLEAN | |
4 | 0 - disabled (default) | |
5 | not 0 - enabled | |
6 | ||
7 | Forward Packets between interfaces. | |
8 | ||
9 | This variable is special, its change resets all configuration | |
10 | parameters to their default state (RFC1122 for hosts, RFC1812 | |
11 | for routers) | |
12 | ||
13 | ip_default_ttl - INTEGER | |
14 | Default 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) | |
17 | ||
18 | ip_no_pmtu_disc - INTEGER | |
19 | Disable Path MTU Discovery. If enabled in mode 1 and a | |
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. | |
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 | ||
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 | |
41 | Default: FALSE | |
42 | ||
43 | min_pmtu - INTEGER | |
44 | default 552 - minimum discovered Path MTU | |
45 | ||
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 | ||
59 | fwmark_reflect - BOOLEAN | |
60 | Controls the fwmark of kernel-generated IPv4 reply packets that are not | |
61 | associated with a socket for example, TCP RSTs or ICMP echo replies). | |
62 | If unset, these packets have a fwmark of zero. If set, they have the | |
63 | fwmark of the packet they are replying to. | |
64 | Default: 0 | |
65 | ||
66 | fib_multipath_use_neigh - BOOLEAN | |
67 | Use status of existing neighbor entry when determining nexthop for | |
68 | multipath routes. If disabled, neighbor information is not used and | |
69 | packets could be directed to a failed nexthop. Only valid for kernels | |
70 | built with CONFIG_IP_ROUTE_MULTIPATH enabled. | |
71 | Default: 0 (disabled) | |
72 | Possible values: | |
73 | 0 - disabled | |
74 | 1 - enabled | |
75 | ||
76 | route/max_size - INTEGER | |
77 | Maximum number of routes allowed in the kernel. Increase | |
78 | this when using large numbers of interfaces and/or routes. | |
79 | From linux kernel 3.6 onwards, this is deprecated for ipv4 | |
80 | as route cache is no longer used. | |
81 | ||
82 | neigh/default/gc_thresh1 - INTEGER | |
83 | Minimum number of entries to keep. Garbage collector will not | |
84 | purge entries if there are fewer than this number. | |
85 | Default: 128 | |
86 | ||
87 | neigh/default/gc_thresh2 - INTEGER | |
88 | Threshold when garbage collector becomes more aggressive about | |
89 | purging entries. Entries older than 5 seconds will be cleared | |
90 | when over this number. | |
91 | Default: 512 | |
92 | ||
93 | neigh/default/gc_thresh3 - INTEGER | |
94 | Maximum number of neighbor entries allowed. Increase this | |
95 | when using large numbers of interfaces and when communicating | |
96 | with large numbers of directly-connected peers. | |
97 | Default: 1024 | |
98 | ||
99 | neigh/default/unres_qlen_bytes - INTEGER | |
100 | The maximum number of bytes which may be used by packets | |
101 | queued for each unresolved address by other network layers. | |
102 | (added in linux 3.3) | |
103 | Setting negative value is meaningless and will return error. | |
104 | Default: 65536 Bytes(64KB) | |
105 | ||
106 | neigh/default/unres_qlen - INTEGER | |
107 | The maximum number of packets which may be queued for each | |
108 | unresolved address by other network layers. | |
109 | (deprecated in linux 3.3) : use unres_qlen_bytes instead. | |
110 | Prior to linux 3.3, the default value is 3 which may cause | |
111 | unexpected packet loss. The current default value is calculated | |
112 | according to default value of unres_qlen_bytes and true size of | |
113 | packet. | |
114 | Default: 31 | |
115 | ||
116 | mtu_expires - INTEGER | |
117 | Time, in seconds, that cached PMTU information is kept. | |
118 | ||
119 | min_adv_mss - INTEGER | |
120 | The advertised MSS depends on the first hop route MTU, but will | |
121 | never be lower than this setting. | |
122 | ||
123 | IP Fragmentation: | |
124 | ||
125 | ipfrag_high_thresh - INTEGER | |
126 | Maximum memory used to reassemble IP fragments. When | |
127 | ipfrag_high_thresh bytes of memory is allocated for this purpose, | |
128 | the fragment handler will toss packets until ipfrag_low_thresh | |
129 | is reached. This also serves as a maximum limit to namespaces | |
130 | different from the initial one. | |
131 | ||
132 | ipfrag_low_thresh - INTEGER | |
133 | Maximum memory used to reassemble IP fragments before the kernel | |
134 | begins to remove incomplete fragment queues to free up resources. | |
135 | The kernel still accepts new fragments for defragmentation. | |
136 | ||
137 | ipfrag_time - INTEGER | |
138 | Time in seconds to keep an IP fragment in memory. | |
139 | ||
140 | ipfrag_max_dist - INTEGER | |
141 | ipfrag_max_dist is a non-negative integer value which defines the | |
142 | maximum "disorder" which is allowed among fragments which share a | |
143 | common IP source address. Note that reordering of packets is | |
144 | not unusual, but if a large number of fragments arrive from a source | |
145 | IP address while a particular fragment queue remains incomplete, it | |
146 | probably indicates that one or more fragments belonging to that queue | |
147 | have been lost. When ipfrag_max_dist is positive, an additional check | |
148 | is done on fragments before they are added to a reassembly queue - if | |
149 | ipfrag_max_dist (or more) fragments have arrived from a particular IP | |
150 | address between additions to any IP fragment queue using that source | |
151 | address, it's presumed that one or more fragments in the queue are | |
152 | lost. The existing fragment queue will be dropped, and a new one | |
153 | started. An ipfrag_max_dist value of zero disables this check. | |
154 | ||
155 | Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can | |
156 | result in unnecessarily dropping fragment queues when normal | |
157 | reordering of packets occurs, which could lead to poor application | |
158 | performance. Using a very large value, e.g. 50000, increases the | |
159 | likelihood of incorrectly reassembling IP fragments that originate | |
160 | from different IP datagrams, which could result in data corruption. | |
161 | Default: 64 | |
162 | ||
163 | INET peer storage: | |
164 | ||
165 | inet_peer_threshold - INTEGER | |
166 | The approximate size of the storage. Starting from this threshold | |
167 | entries will be thrown aggressively. This threshold also determines | |
168 | entries' time-to-live and time intervals between garbage collection | |
169 | passes. More entries, less time-to-live, less GC interval. | |
170 | ||
171 | inet_peer_minttl - INTEGER | |
172 | Minimum time-to-live of entries. Should be enough to cover fragment | |
173 | time-to-live on the reassembling side. This minimum time-to-live is | |
174 | guaranteed if the pool size is less than inet_peer_threshold. | |
175 | Measured in seconds. | |
176 | ||
177 | inet_peer_maxttl - INTEGER | |
178 | Maximum time-to-live of entries. Unused entries will expire after | |
179 | this period of time if there is no memory pressure on the pool (i.e. | |
180 | when the number of entries in the pool is very small). | |
181 | Measured in seconds. | |
182 | ||
183 | TCP variables: | |
184 | ||
185 | somaxconn - INTEGER | |
186 | Limit of socket listen() backlog, known in userspace as SOMAXCONN. | |
187 | Defaults to 128. See also tcp_max_syn_backlog for additional tuning | |
188 | for TCP sockets. | |
189 | ||
190 | tcp_abort_on_overflow - BOOLEAN | |
191 | If listening service is too slow to accept new connections, | |
192 | reset them. Default state is FALSE. It means that if overflow | |
193 | occurred due to a burst, connection will recover. Enable this | |
194 | option _only_ if you are really sure that listening daemon | |
195 | cannot be tuned to accept connections faster. Enabling this | |
196 | option can harm clients of your server. | |
197 | ||
198 | tcp_adv_win_scale - INTEGER | |
199 | Count buffering overhead as bytes/2^tcp_adv_win_scale | |
200 | (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), | |
201 | if it is <= 0. | |
202 | Possible values are [-31, 31], inclusive. | |
203 | Default: 1 | |
204 | ||
205 | tcp_allowed_congestion_control - STRING | |
206 | Show/set the congestion control choices available to non-privileged | |
207 | processes. The list is a subset of those listed in | |
208 | tcp_available_congestion_control. | |
209 | Default is "reno" and the default setting (tcp_congestion_control). | |
210 | ||
211 | tcp_app_win - INTEGER | |
212 | Reserve max(window/2^tcp_app_win, mss) of window for application | |
213 | buffer. Value 0 is special, it means that nothing is reserved. | |
214 | Default: 31 | |
215 | ||
216 | tcp_autocorking - BOOLEAN | |
217 | Enable TCP auto corking : | |
218 | When applications do consecutive small write()/sendmsg() system calls, | |
219 | we try to coalesce these small writes as much as possible, to lower | |
220 | total amount of sent packets. This is done if at least one prior | |
221 | packet for the flow is waiting in Qdisc queues or device transmit | |
222 | queue. Applications can still use TCP_CORK for optimal behavior | |
223 | when they know how/when to uncork their sockets. | |
224 | Default : 1 | |
225 | ||
226 | tcp_available_congestion_control - STRING | |
227 | Shows the available congestion control choices that are registered. | |
228 | More congestion control algorithms may be available as modules, | |
229 | but not loaded. | |
230 | ||
231 | tcp_base_mss - INTEGER | |
232 | The initial value of search_low to be used by the packetization layer | |
233 | Path MTU discovery (MTU probing). If MTU probing is enabled, | |
234 | this is the initial MSS used by the connection. | |
235 | ||
236 | tcp_congestion_control - STRING | |
237 | Set the congestion control algorithm to be used for new | |
238 | connections. The algorithm "reno" is always available, but | |
239 | additional choices may be available based on kernel configuration. | |
240 | Default is set as part of kernel configuration. | |
241 | For passive connections, the listener congestion control choice | |
242 | is inherited. | |
243 | [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ] | |
244 | ||
245 | tcp_dsack - BOOLEAN | |
246 | Allows TCP to send "duplicate" SACKs. | |
247 | ||
248 | tcp_early_retrans - INTEGER | |
249 | Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold | |
250 | for triggering fast retransmit when the amount of outstanding data is | |
251 | small and when no previously unsent data can be transmitted (such | |
252 | that limited transmit could be used). Also controls the use of | |
253 | Tail loss probe (TLP) that converts RTOs occurring due to tail | |
254 | losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01). | |
255 | Possible values: | |
256 | 0 disables ER | |
257 | 1 enables ER | |
258 | 2 enables ER but delays fast recovery and fast retransmit | |
259 | by a fourth of RTT. This mitigates connection falsely | |
260 | recovers when network has a small degree of reordering | |
261 | (less than 3 packets). | |
262 | 3 enables delayed ER and TLP. | |
263 | 4 enables TLP only. | |
264 | Default: 3 | |
265 | ||
266 | tcp_ecn - INTEGER | |
267 | Control use of Explicit Congestion Notification (ECN) by TCP. | |
268 | ECN is used only when both ends of the TCP connection indicate | |
269 | support for it. This feature is useful in avoiding losses due | |
270 | to congestion by allowing supporting routers to signal | |
271 | congestion before having to drop packets. | |
272 | Possible values are: | |
273 | 0 Disable ECN. Neither initiate nor accept ECN. | |
274 | 1 Enable ECN when requested by incoming connections and | |
275 | also request ECN on outgoing connection attempts. | |
276 | 2 Enable ECN when requested by incoming connections | |
277 | but do not request ECN on outgoing connections. | |
278 | Default: 2 | |
279 | ||
280 | tcp_ecn_fallback - BOOLEAN | |
281 | If the kernel detects that ECN connection misbehaves, enable fall | |
282 | back to non-ECN. Currently, this knob implements the fallback | |
283 | from RFC3168, section 6.1.1.1., but we reserve that in future, | |
284 | additional detection mechanisms could be implemented under this | |
285 | knob. The value is not used, if tcp_ecn or per route (or congestion | |
286 | control) ECN settings are disabled. | |
287 | Default: 1 (fallback enabled) | |
288 | ||
289 | tcp_fack - BOOLEAN | |
290 | Enable FACK congestion avoidance and fast retransmission. | |
291 | The value is not used, if tcp_sack is not enabled. | |
292 | ||
293 | tcp_fin_timeout - INTEGER | |
294 | The length of time an orphaned (no longer referenced by any | |
295 | application) connection will remain in the FIN_WAIT_2 state | |
296 | before it is aborted at the local end. While a perfectly | |
297 | valid "receive only" state for an un-orphaned connection, an | |
298 | orphaned connection in FIN_WAIT_2 state could otherwise wait | |
299 | forever for the remote to close its end of the connection. | |
300 | Cf. tcp_max_orphans | |
301 | Default: 60 seconds | |
302 | ||
303 | tcp_frto - INTEGER | |
304 | Enables Forward RTO-Recovery (F-RTO) defined in RFC5682. | |
305 | F-RTO is an enhanced recovery algorithm for TCP retransmission | |
306 | timeouts. It is particularly beneficial in networks where the | |
307 | RTT fluctuates (e.g., wireless). F-RTO is sender-side only | |
308 | modification. It does not require any support from the peer. | |
309 | ||
310 | By default it's enabled with a non-zero value. 0 disables F-RTO. | |
311 | ||
312 | tcp_invalid_ratelimit - INTEGER | |
313 | Limit the maximal rate for sending duplicate acknowledgments | |
314 | in response to incoming TCP packets that are for an existing | |
315 | connection but that are invalid due to any of these reasons: | |
316 | ||
317 | (a) out-of-window sequence number, | |
318 | (b) out-of-window acknowledgment number, or | |
319 | (c) PAWS (Protection Against Wrapped Sequence numbers) check failure | |
320 | ||
321 | This can help mitigate simple "ack loop" DoS attacks, wherein | |
322 | a buggy or malicious middlebox or man-in-the-middle can | |
323 | rewrite TCP header fields in manner that causes each endpoint | |
324 | to think that the other is sending invalid TCP segments, thus | |
325 | causing each side to send an unterminating stream of duplicate | |
326 | acknowledgments for invalid segments. | |
327 | ||
328 | Using 0 disables rate-limiting of dupacks in response to | |
329 | invalid segments; otherwise this value specifies the minimal | |
330 | space between sending such dupacks, in milliseconds. | |
331 | ||
332 | Default: 500 (milliseconds). | |
333 | ||
334 | tcp_keepalive_time - INTEGER | |
335 | How often TCP sends out keepalive messages when keepalive is enabled. | |
336 | Default: 2hours. | |
337 | ||
338 | tcp_keepalive_probes - INTEGER | |
339 | How many keepalive probes TCP sends out, until it decides that the | |
340 | connection is broken. Default value: 9. | |
341 | ||
342 | tcp_keepalive_intvl - INTEGER | |
343 | How frequently the probes are send out. Multiplied by | |
344 | tcp_keepalive_probes it is time to kill not responding connection, | |
345 | after probes started. Default value: 75sec i.e. connection | |
346 | will be aborted after ~11 minutes of retries. | |
347 | ||
348 | tcp_l3mdev_accept - BOOLEAN | |
349 | Enables child sockets to inherit the L3 master device index. | |
350 | Enabling this option allows a "global" listen socket to work | |
351 | across L3 master domains (e.g., VRFs) with connected sockets | |
352 | derived from the listen socket to be bound to the L3 domain in | |
353 | which the packets originated. Only valid when the kernel was | |
354 | compiled with CONFIG_NET_L3_MASTER_DEV. | |
355 | ||
356 | tcp_low_latency - BOOLEAN | |
357 | If set, the TCP stack makes decisions that prefer lower | |
358 | latency as opposed to higher throughput. By default, this | |
359 | option is not set meaning that higher throughput is preferred. | |
360 | An example of an application where this default should be | |
361 | changed would be a Beowulf compute cluster. | |
362 | Default: 0 | |
363 | ||
364 | tcp_max_orphans - INTEGER | |
365 | Maximal number of TCP sockets not attached to any user file handle, | |
366 | held by system. If this number is exceeded orphaned connections are | |
367 | reset immediately and warning is printed. This limit exists | |
368 | only to prevent simple DoS attacks, you _must_ not rely on this | |
369 | or lower the limit artificially, but rather increase it | |
370 | (probably, after increasing installed memory), | |
371 | if network conditions require more than default value, | |
372 | and tune network services to linger and kill such states | |
373 | more aggressively. Let me to remind again: each orphan eats | |
374 | up to ~64K of unswappable memory. | |
375 | ||
376 | tcp_max_syn_backlog - INTEGER | |
377 | Maximal number of remembered connection requests, which have not | |
378 | received an acknowledgment from connecting client. | |
379 | The minimal value is 128 for low memory machines, and it will | |
380 | increase in proportion to the memory of machine. | |
381 | If server suffers from overload, try increasing this number. | |
382 | ||
383 | tcp_max_tw_buckets - INTEGER | |
384 | Maximal number of timewait sockets held by system simultaneously. | |
385 | If this number is exceeded time-wait socket is immediately destroyed | |
386 | and warning is printed. This limit exists only to prevent | |
387 | simple DoS attacks, you _must_ not lower the limit artificially, | |
388 | but rather increase it (probably, after increasing installed memory), | |
389 | if network conditions require more than default value. | |
390 | ||
391 | tcp_mem - vector of 3 INTEGERs: min, pressure, max | |
392 | min: below this number of pages TCP is not bothered about its | |
393 | memory appetite. | |
394 | ||
395 | pressure: when amount of memory allocated by TCP exceeds this number | |
396 | of pages, TCP moderates its memory consumption and enters memory | |
397 | pressure mode, which is exited when memory consumption falls | |
398 | under "min". | |
399 | ||
400 | max: number of pages allowed for queueing by all TCP sockets. | |
401 | ||
402 | Defaults are calculated at boot time from amount of available | |
403 | memory. | |
404 | ||
405 | tcp_min_rtt_wlen - INTEGER | |
406 | The window length of the windowed min filter to track the minimum RTT. | |
407 | A shorter window lets a flow more quickly pick up new (higher) | |
408 | minimum RTT when it is moved to a longer path (e.g., due to traffic | |
409 | engineering). A longer window makes the filter more resistant to RTT | |
410 | inflations such as transient congestion. The unit is seconds. | |
411 | Default: 300 | |
412 | ||
413 | tcp_moderate_rcvbuf - BOOLEAN | |
414 | If set, TCP performs receive buffer auto-tuning, attempting to | |
415 | automatically size the buffer (no greater than tcp_rmem[2]) to | |
416 | match the size required by the path for full throughput. Enabled by | |
417 | default. | |
418 | ||
419 | tcp_mtu_probing - INTEGER | |
420 | Controls TCP Packetization-Layer Path MTU Discovery. Takes three | |
421 | values: | |
422 | 0 - Disabled | |
423 | 1 - Disabled by default, enabled when an ICMP black hole detected | |
424 | 2 - Always enabled, use initial MSS of tcp_base_mss. | |
425 | ||
426 | tcp_probe_interval - INTEGER | |
427 | Controls how often to start TCP Packetization-Layer Path MTU | |
428 | Discovery reprobe. The default is reprobing every 10 minutes as | |
429 | per RFC4821. | |
430 | ||
431 | tcp_probe_threshold - INTEGER | |
432 | Controls when TCP Packetization-Layer Path MTU Discovery probing | |
433 | will stop in respect to the width of search range in bytes. Default | |
434 | is 8 bytes. | |
435 | ||
436 | tcp_no_metrics_save - BOOLEAN | |
437 | By default, TCP saves various connection metrics in the route cache | |
438 | when the connection closes, so that connections established in the | |
439 | near future can use these to set initial conditions. Usually, this | |
440 | increases overall performance, but may sometimes cause performance | |
441 | degradation. If set, TCP will not cache metrics on closing | |
442 | connections. | |
443 | ||
444 | tcp_orphan_retries - INTEGER | |
445 | This value influences the timeout of a locally closed TCP connection, | |
446 | when RTO retransmissions remain unacknowledged. | |
447 | See tcp_retries2 for more details. | |
448 | ||
449 | The default value is 8. | |
450 | If your machine is a loaded WEB server, | |
451 | you should think about lowering this value, such sockets | |
452 | may consume significant resources. Cf. tcp_max_orphans. | |
453 | ||
454 | tcp_recovery - INTEGER | |
455 | This value is a bitmap to enable various experimental loss recovery | |
456 | features. | |
457 | ||
458 | RACK: 0x1 enables the RACK loss detection for fast detection of lost | |
459 | retransmissions and tail drops. | |
460 | ||
461 | Default: 0x1 | |
462 | ||
463 | tcp_reordering - INTEGER | |
464 | Initial reordering level of packets in a TCP stream. | |
465 | TCP stack can then dynamically adjust flow reordering level | |
466 | between this initial value and tcp_max_reordering | |
467 | Default: 3 | |
468 | ||
469 | tcp_max_reordering - INTEGER | |
470 | Maximal reordering level of packets in a TCP stream. | |
471 | 300 is a fairly conservative value, but you might increase it | |
472 | if paths are using per packet load balancing (like bonding rr mode) | |
473 | Default: 300 | |
474 | ||
475 | tcp_retrans_collapse - BOOLEAN | |
476 | Bug-to-bug compatibility with some broken printers. | |
477 | On retransmit try to send bigger packets to work around bugs in | |
478 | certain TCP stacks. | |
479 | ||
480 | tcp_retries1 - INTEGER | |
481 | This value influences the time, after which TCP decides, that | |
482 | something is wrong due to unacknowledged RTO retransmissions, | |
483 | and reports this suspicion to the network layer. | |
484 | See tcp_retries2 for more details. | |
485 | ||
486 | RFC 1122 recommends at least 3 retransmissions, which is the | |
487 | default. | |
488 | ||
489 | tcp_retries2 - INTEGER | |
490 | This value influences the timeout of an alive TCP connection, | |
491 | when RTO retransmissions remain unacknowledged. | |
492 | Given a value of N, a hypothetical TCP connection following | |
493 | exponential backoff with an initial RTO of TCP_RTO_MIN would | |
494 | retransmit N times before killing the connection at the (N+1)th RTO. | |
495 | ||
496 | The default value of 15 yields a hypothetical timeout of 924.6 | |
497 | seconds and is a lower bound for the effective timeout. | |
498 | TCP will effectively time out at the first RTO which exceeds the | |
499 | hypothetical timeout. | |
500 | ||
501 | RFC 1122 recommends at least 100 seconds for the timeout, | |
502 | which corresponds to a value of at least 8. | |
503 | ||
504 | tcp_rfc1337 - BOOLEAN | |
505 | If set, the TCP stack behaves conforming to RFC1337. If unset, | |
506 | we are not conforming to RFC, but prevent TCP TIME_WAIT | |
507 | assassination. | |
508 | Default: 0 | |
509 | ||
510 | tcp_rmem - vector of 3 INTEGERs: min, default, max | |
511 | min: Minimal size of receive buffer used by TCP sockets. | |
512 | It is guaranteed to each TCP socket, even under moderate memory | |
513 | pressure. | |
514 | Default: 1 page | |
515 | ||
516 | default: initial size of receive buffer used by TCP sockets. | |
517 | This value overrides net.core.rmem_default used by other protocols. | |
518 | Default: 87380 bytes. This value results in window of 65535 with | |
519 | default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit | |
520 | less for default tcp_app_win. See below about these variables. | |
521 | ||
522 | max: maximal size of receive buffer allowed for automatically | |
523 | selected receiver buffers for TCP socket. This value does not override | |
524 | net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables | |
525 | automatic tuning of that socket's receive buffer size, in which | |
526 | case this value is ignored. | |
527 | Default: between 87380B and 6MB, depending on RAM size. | |
528 | ||
529 | tcp_sack - BOOLEAN | |
530 | Enable select acknowledgments (SACKS). | |
531 | ||
532 | tcp_slow_start_after_idle - BOOLEAN | |
533 | If set, provide RFC2861 behavior and time out the congestion | |
534 | window after an idle period. An idle period is defined at | |
535 | the current RTO. If unset, the congestion window will not | |
536 | be timed out after an idle period. | |
537 | Default: 1 | |
538 | ||
539 | tcp_stdurg - BOOLEAN | |
540 | Use the Host requirements interpretation of the TCP urgent pointer field. | |
541 | Most hosts use the older BSD interpretation, so if you turn this on | |
542 | Linux might not communicate correctly with them. | |
543 | Default: FALSE | |
544 | ||
545 | tcp_synack_retries - INTEGER | |
546 | Number of times SYNACKs for a passive TCP connection attempt will | |
547 | be retransmitted. Should not be higher than 255. Default value | |
548 | is 5, which corresponds to 31seconds till the last retransmission | |
549 | with the current initial RTO of 1second. With this the final timeout | |
550 | for a passive TCP connection will happen after 63seconds. | |
551 | ||
552 | tcp_syncookies - BOOLEAN | |
553 | Only valid when the kernel was compiled with CONFIG_SYN_COOKIES | |
554 | Send out syncookies when the syn backlog queue of a socket | |
555 | overflows. This is to prevent against the common 'SYN flood attack' | |
556 | Default: 1 | |
557 | ||
558 | Note, that syncookies is fallback facility. | |
559 | It MUST NOT be used to help highly loaded servers to stand | |
560 | against legal connection rate. If you see SYN flood warnings | |
561 | in your logs, but investigation shows that they occur | |
562 | because of overload with legal connections, you should tune | |
563 | another parameters until this warning disappear. | |
564 | See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow. | |
565 | ||
566 | syncookies seriously violate TCP protocol, do not allow | |
567 | to use TCP extensions, can result in serious degradation | |
568 | of some services (f.e. SMTP relaying), visible not by you, | |
569 | but your clients and relays, contacting you. While you see | |
570 | SYN flood warnings in logs not being really flooded, your server | |
571 | is seriously misconfigured. | |
572 | ||
573 | If you want to test which effects syncookies have to your | |
574 | network connections you can set this knob to 2 to enable | |
575 | unconditionally generation of syncookies. | |
576 | ||
577 | tcp_fastopen - INTEGER | |
578 | Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data | |
579 | in the opening SYN packet. To use this feature, the client application | |
580 | must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than | |
581 | connect() to perform a TCP handshake automatically. | |
582 | ||
583 | The values (bitmap) are | |
584 | 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN. | |
585 | 2: Enables TCP Fast Open on the server side, i.e., allowing data in | |
586 | a SYN packet to be accepted and passed to the application before | |
587 | 3-way hand shake finishes. | |
588 | 4: Send data in the opening SYN regardless of cookie availability and | |
589 | without a cookie option. | |
590 | 0x100: Accept SYN data w/o validating the cookie. | |
591 | 0x200: Accept data-in-SYN w/o any cookie option present. | |
592 | 0x400/0x800: Enable Fast Open on all listeners regardless of the | |
593 | TCP_FASTOPEN socket option. The two different flags designate two | |
594 | different ways of setting max_qlen without the TCP_FASTOPEN socket | |
595 | option. | |
596 | ||
597 | Default: 1 | |
598 | ||
599 | Note that the client & server side Fast Open flags (1 and 2 | |
600 | respectively) must be also enabled before the rest of flags can take | |
601 | effect. | |
602 | ||
603 | See include/net/tcp.h and the code for more details. | |
604 | ||
605 | tcp_syn_retries - INTEGER | |
606 | Number of times initial SYNs for an active TCP connection attempt | |
607 | will be retransmitted. Should not be higher than 127. Default value | |
608 | is 6, which corresponds to 63seconds till the last retransmission | |
609 | with the current initial RTO of 1second. With this the final timeout | |
610 | for an active TCP connection attempt will happen after 127seconds. | |
611 | ||
612 | tcp_timestamps - BOOLEAN | |
613 | Enable timestamps as defined in RFC1323. | |
614 | ||
615 | tcp_min_tso_segs - INTEGER | |
616 | Minimal number of segments per TSO frame. | |
617 | Since linux-3.12, TCP does an automatic sizing of TSO frames, | |
618 | depending on flow rate, instead of filling 64Kbytes packets. | |
619 | For specific usages, it's possible to force TCP to build big | |
620 | TSO frames. Note that TCP stack might split too big TSO packets | |
621 | if available window is too small. | |
622 | Default: 2 | |
623 | ||
624 | tcp_pacing_ss_ratio - INTEGER | |
625 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
626 | to current rate. (current_rate = cwnd * mss / srtt) | |
627 | If TCP is in slow start, tcp_pacing_ss_ratio is applied | |
628 | to let TCP probe for bigger speeds, assuming cwnd can be | |
629 | doubled every other RTT. | |
630 | Default: 200 | |
631 | ||
632 | tcp_pacing_ca_ratio - INTEGER | |
633 | sk->sk_pacing_rate is set by TCP stack using a ratio applied | |
634 | to current rate. (current_rate = cwnd * mss / srtt) | |
635 | If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio | |
636 | is applied to conservatively probe for bigger throughput. | |
637 | Default: 120 | |
638 | ||
639 | tcp_tso_win_divisor - INTEGER | |
640 | This allows control over what percentage of the congestion window | |
641 | can be consumed by a single TSO frame. | |
642 | The setting of this parameter is a choice between burstiness and | |
643 | building larger TSO frames. | |
644 | Default: 3 | |
645 | ||
646 | tcp_tw_recycle - BOOLEAN | |
647 | Enable fast recycling TIME-WAIT sockets. Default value is 0. | |
648 | It should not be changed without advice/request of technical | |
649 | experts. | |
650 | ||
651 | tcp_tw_reuse - BOOLEAN | |
652 | Allow to reuse TIME-WAIT sockets for new connections when it is | |
653 | safe from protocol viewpoint. Default value is 0. | |
654 | It should not be changed without advice/request of technical | |
655 | experts. | |
656 | ||
657 | tcp_window_scaling - BOOLEAN | |
658 | Enable window scaling as defined in RFC1323. | |
659 | ||
660 | tcp_wmem - vector of 3 INTEGERs: min, default, max | |
661 | min: Amount of memory reserved for send buffers for TCP sockets. | |
662 | Each TCP socket has rights to use it due to fact of its birth. | |
663 | Default: 1 page | |
664 | ||
665 | default: initial size of send buffer used by TCP sockets. This | |
666 | value overrides net.core.wmem_default used by other protocols. | |
667 | It is usually lower than net.core.wmem_default. | |
668 | Default: 16K | |
669 | ||
670 | max: Maximal amount of memory allowed for automatically tuned | |
671 | send buffers for TCP sockets. This value does not override | |
672 | net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables | |
673 | automatic tuning of that socket's send buffer size, in which case | |
674 | this value is ignored. | |
675 | Default: between 64K and 4MB, depending on RAM size. | |
676 | ||
677 | tcp_notsent_lowat - UNSIGNED INTEGER | |
678 | A TCP socket can control the amount of unsent bytes in its write queue, | |
679 | thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll() | |
680 | reports POLLOUT events if the amount of unsent bytes is below a per | |
681 | socket value, and if the write queue is not full. sendmsg() will | |
682 | also not add new buffers if the limit is hit. | |
683 | ||
684 | This global variable controls the amount of unsent data for | |
685 | sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change | |
686 | to the global variable has immediate effect. | |
687 | ||
688 | Default: UINT_MAX (0xFFFFFFFF) | |
689 | ||
690 | tcp_workaround_signed_windows - BOOLEAN | |
691 | If set, assume no receipt of a window scaling option means the | |
692 | remote TCP is broken and treats the window as a signed quantity. | |
693 | If unset, assume the remote TCP is not broken even if we do | |
694 | not receive a window scaling option from them. | |
695 | Default: 0 | |
696 | ||
697 | tcp_thin_linear_timeouts - BOOLEAN | |
698 | Enable dynamic triggering of linear timeouts for thin streams. | |
699 | If set, a check is performed upon retransmission by timeout to | |
700 | determine if the stream is thin (less than 4 packets in flight). | |
701 | As long as the stream is found to be thin, up to 6 linear | |
702 | timeouts may be performed before exponential backoff mode is | |
703 | initiated. This improves retransmission latency for | |
704 | non-aggressive thin streams, often found to be time-dependent. | |
705 | For more information on thin streams, see | |
706 | Documentation/networking/tcp-thin.txt | |
707 | Default: 0 | |
708 | ||
709 | tcp_thin_dupack - BOOLEAN | |
710 | Enable dynamic triggering of retransmissions after one dupACK | |
711 | for thin streams. If set, a check is performed upon reception | |
712 | of a dupACK to determine if the stream is thin (less than 4 | |
713 | packets in flight). As long as the stream is found to be thin, | |
714 | data is retransmitted on the first received dupACK. This | |
715 | improves retransmission latency for non-aggressive thin | |
716 | streams, often found to be time-dependent. | |
717 | For more information on thin streams, see | |
718 | Documentation/networking/tcp-thin.txt | |
719 | Default: 0 | |
720 | ||
721 | tcp_limit_output_bytes - INTEGER | |
722 | Controls TCP Small Queue limit per tcp socket. | |
723 | TCP bulk sender tends to increase packets in flight until it | |
724 | gets losses notifications. With SNDBUF autotuning, this can | |
725 | result in a large amount of packets queued in qdisc/device | |
726 | on the local machine, hurting latency of other flows, for | |
727 | typical pfifo_fast qdiscs. | |
728 | tcp_limit_output_bytes limits the number of bytes on qdisc | |
729 | or device to reduce artificial RTT/cwnd and reduce bufferbloat. | |
730 | Default: 262144 | |
731 | ||
732 | tcp_challenge_ack_limit - INTEGER | |
733 | Limits number of Challenge ACK sent per second, as recommended | |
734 | in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) | |
735 | Default: 100 | |
736 | ||
737 | UDP variables: | |
738 | ||
739 | udp_mem - vector of 3 INTEGERs: min, pressure, max | |
740 | Number of pages allowed for queueing by all UDP sockets. | |
741 | ||
742 | min: Below this number of pages UDP is not bothered about its | |
743 | memory appetite. When amount of memory allocated by UDP exceeds | |
744 | this number, UDP starts to moderate memory usage. | |
745 | ||
746 | pressure: This value was introduced to follow format of tcp_mem. | |
747 | ||
748 | max: Number of pages allowed for queueing by all UDP sockets. | |
749 | ||
750 | Default is calculated at boot time from amount of available memory. | |
751 | ||
752 | udp_rmem_min - INTEGER | |
753 | Minimal size of receive buffer used by UDP sockets in moderation. | |
754 | Each UDP socket is able to use the size for receiving data, even if | |
755 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
756 | Default: 1 page | |
757 | ||
758 | udp_wmem_min - INTEGER | |
759 | Minimal size of send buffer used by UDP sockets in moderation. | |
760 | Each UDP socket is able to use the size for sending data, even if | |
761 | total pages of UDP sockets exceed udp_mem pressure. The unit is byte. | |
762 | Default: 1 page | |
763 | ||
764 | CIPSOv4 Variables: | |
765 | ||
766 | cipso_cache_enable - BOOLEAN | |
767 | If set, enable additions to and lookups from the CIPSO label mapping | |
768 | cache. If unset, additions are ignored and lookups always result in a | |
769 | miss. However, regardless of the setting the cache is still | |
770 | invalidated when required when means you can safely toggle this on and | |
771 | off and the cache will always be "safe". | |
772 | Default: 1 | |
773 | ||
774 | cipso_cache_bucket_size - INTEGER | |
775 | The CIPSO label cache consists of a fixed size hash table with each | |
776 | hash bucket containing a number of cache entries. This variable limits | |
777 | the number of entries in each hash bucket; the larger the value the | |
778 | more CIPSO label mappings that can be cached. When the number of | |
779 | entries in a given hash bucket reaches this limit adding new entries | |
780 | causes the oldest entry in the bucket to be removed to make room. | |
781 | Default: 10 | |
782 | ||
783 | cipso_rbm_optfmt - BOOLEAN | |
784 | Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of | |
785 | the CIPSO draft specification (see Documentation/netlabel for details). | |
786 | This means that when set the CIPSO tag will be padded with empty | |
787 | categories in order to make the packet data 32-bit aligned. | |
788 | Default: 0 | |
789 | ||
790 | cipso_rbm_structvalid - BOOLEAN | |
791 | If set, do a very strict check of the CIPSO option when | |
792 | ip_options_compile() is called. If unset, relax the checks done during | |
793 | ip_options_compile(). Either way is "safe" as errors are caught else | |
794 | where in the CIPSO processing code but setting this to 0 (False) should | |
795 | result in less work (i.e. it should be faster) but could cause problems | |
796 | with other implementations that require strict checking. | |
797 | Default: 0 | |
798 | ||
799 | IP Variables: | |
800 | ||
801 | ip_local_port_range - 2 INTEGERS | |
802 | Defines the local port range that is used by TCP and UDP to | |
803 | choose the local port. The first number is the first, the | |
804 | second the last local port number. | |
805 | If possible, it is better these numbers have different parity. | |
806 | (one even and one odd values) | |
807 | The default values are 32768 and 60999 respectively. | |
808 | ||
809 | ip_local_reserved_ports - list of comma separated ranges | |
810 | Specify the ports which are reserved for known third-party | |
811 | applications. These ports will not be used by automatic port | |
812 | assignments (e.g. when calling connect() or bind() with port | |
813 | number 0). Explicit port allocation behavior is unchanged. | |
814 | ||
815 | The format used for both input and output is a comma separated | |
816 | list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and | |
817 | 10). Writing to the file will clear all previously reserved | |
818 | ports and update the current list with the one given in the | |
819 | input. | |
820 | ||
821 | Note that ip_local_port_range and ip_local_reserved_ports | |
822 | settings are independent and both are considered by the kernel | |
823 | when determining which ports are available for automatic port | |
824 | assignments. | |
825 | ||
826 | You can reserve ports which are not in the current | |
827 | ip_local_port_range, e.g.: | |
828 | ||
829 | $ cat /proc/sys/net/ipv4/ip_local_port_range | |
830 | 32000 60999 | |
831 | $ cat /proc/sys/net/ipv4/ip_local_reserved_ports | |
832 | 8080,9148 | |
833 | ||
834 | although this is redundant. However such a setting is useful | |
835 | if later the port range is changed to a value that will | |
836 | include the reserved ports. | |
837 | ||
838 | Default: Empty | |
839 | ||
840 | ip_nonlocal_bind - BOOLEAN | |
841 | If set, allows processes to bind() to non-local IP addresses, | |
842 | which can be quite useful - but may break some applications. | |
843 | Default: 0 | |
844 | ||
845 | ip_dynaddr - BOOLEAN | |
846 | If set non-zero, enables support for dynamic addresses. | |
847 | If set to a non-zero value larger than 1, a kernel log | |
848 | message will be printed when dynamic address rewriting | |
849 | occurs. | |
850 | Default: 0 | |
851 | ||
852 | ip_early_demux - BOOLEAN | |
853 | Optimize input packet processing down to one demux for | |
854 | certain kinds of local sockets. Currently we only do this | |
855 | for established TCP sockets. | |
856 | ||
857 | It may add an additional cost for pure routing workloads that | |
858 | reduces overall throughput, in such case you should disable it. | |
859 | Default: 1 | |
860 | ||
861 | icmp_echo_ignore_all - BOOLEAN | |
862 | If set non-zero, then the kernel will ignore all ICMP ECHO | |
863 | requests sent to it. | |
864 | Default: 0 | |
865 | ||
866 | icmp_echo_ignore_broadcasts - BOOLEAN | |
867 | If set non-zero, then the kernel will ignore all ICMP ECHO and | |
868 | TIMESTAMP requests sent to it via broadcast/multicast. | |
869 | Default: 1 | |
870 | ||
871 | icmp_ratelimit - INTEGER | |
872 | Limit the maximal rates for sending ICMP packets whose type matches | |
873 | icmp_ratemask (see below) to specific targets. | |
874 | 0 to disable any limiting, | |
875 | otherwise the minimal space between responses in milliseconds. | |
876 | Note that another sysctl, icmp_msgs_per_sec limits the number | |
877 | of ICMP packets sent on all targets. | |
878 | Default: 1000 | |
879 | ||
880 | icmp_msgs_per_sec - INTEGER | |
881 | Limit maximal number of ICMP packets sent per second from this host. | |
882 | Only messages whose type matches icmp_ratemask (see below) are | |
883 | controlled by this limit. | |
884 | Default: 1000 | |
885 | ||
886 | icmp_msgs_burst - INTEGER | |
887 | icmp_msgs_per_sec controls number of ICMP packets sent per second, | |
888 | while icmp_msgs_burst controls the burst size of these packets. | |
889 | Default: 50 | |
890 | ||
891 | icmp_ratemask - INTEGER | |
892 | Mask made of ICMP types for which rates are being limited. | |
893 | Significant bits: IHGFEDCBA9876543210 | |
894 | Default mask: 0000001100000011000 (6168) | |
895 | ||
896 | Bit definitions (see include/linux/icmp.h): | |
897 | 0 Echo Reply | |
898 | 3 Destination Unreachable * | |
899 | 4 Source Quench * | |
900 | 5 Redirect | |
901 | 8 Echo Request | |
902 | B Time Exceeded * | |
903 | C Parameter Problem * | |
904 | D Timestamp Request | |
905 | E Timestamp Reply | |
906 | F Info Request | |
907 | G Info Reply | |
908 | H Address Mask Request | |
909 | I Address Mask Reply | |
910 | ||
911 | * These are rate limited by default (see default mask above) | |
912 | ||
913 | icmp_ignore_bogus_error_responses - BOOLEAN | |
914 | Some routers violate RFC1122 by sending bogus responses to broadcast | |
915 | frames. Such violations are normally logged via a kernel warning. | |
916 | If this is set to TRUE, the kernel will not give such warnings, which | |
917 | will avoid log file clutter. | |
918 | Default: 1 | |
919 | ||
920 | icmp_errors_use_inbound_ifaddr - BOOLEAN | |
921 | ||
922 | If zero, icmp error messages are sent with the primary address of | |
923 | the exiting interface. | |
924 | ||
925 | If non-zero, the message will be sent with the primary address of | |
926 | the interface that received the packet that caused the icmp error. | |
927 | This is the behaviour network many administrators will expect from | |
928 | a router. And it can make debugging complicated network layouts | |
929 | much easier. | |
930 | ||
931 | Note that if no primary address exists for the interface selected, | |
932 | then the primary address of the first non-loopback interface that | |
933 | has one will be used regardless of this setting. | |
934 | ||
935 | Default: 0 | |
936 | ||
937 | igmp_max_memberships - INTEGER | |
938 | Change the maximum number of multicast groups we can subscribe to. | |
939 | Default: 20 | |
940 | ||
941 | Theoretical maximum value is bounded by having to send a membership | |
942 | report in a single datagram (i.e. the report can't span multiple | |
943 | datagrams, or risk confusing the switch and leaving groups you don't | |
944 | intend to). | |
945 | ||
946 | The number of supported groups 'M' is bounded by the number of group | |
947 | report entries you can fit into a single datagram of 65535 bytes. | |
948 | ||
949 | M = 65536-sizeof (ip header)/(sizeof(Group record)) | |
950 | ||
951 | Group records are variable length, with a minimum of 12 bytes. | |
952 | So net.ipv4.igmp_max_memberships should not be set higher than: | |
953 | ||
954 | (65536-24) / 12 = 5459 | |
955 | ||
956 | The value 5459 assumes no IP header options, so in practice | |
957 | this number may be lower. | |
958 | ||
959 | igmp_max_msf - INTEGER | |
960 | Maximum number of addresses allowed in the source filter list for a | |
961 | multicast group. | |
962 | Default: 10 | |
963 | ||
964 | igmp_qrv - INTEGER | |
965 | Controls the IGMP query robustness variable (see RFC2236 8.1). | |
966 | Default: 2 (as specified by RFC2236 8.1) | |
967 | Minimum: 1 (as specified by RFC6636 4.5) | |
968 | ||
969 | conf/interface/* changes special settings per interface (where | |
970 | "interface" is the name of your network interface) | |
971 | ||
972 | conf/all/* is special, changes the settings for all interfaces | |
973 | ||
974 | log_martians - BOOLEAN | |
975 | Log packets with impossible addresses to kernel log. | |
976 | log_martians for the interface will be enabled if at least one of | |
977 | conf/{all,interface}/log_martians is set to TRUE, | |
978 | it will be disabled otherwise | |
979 | ||
980 | accept_redirects - BOOLEAN | |
981 | Accept ICMP redirect messages. | |
982 | accept_redirects for the interface will be enabled if: | |
983 | - both conf/{all,interface}/accept_redirects are TRUE in the case | |
984 | forwarding for the interface is enabled | |
985 | or | |
986 | - at least one of conf/{all,interface}/accept_redirects is TRUE in the | |
987 | case forwarding for the interface is disabled | |
988 | accept_redirects for the interface will be disabled otherwise | |
989 | default TRUE (host) | |
990 | FALSE (router) | |
991 | ||
992 | forwarding - BOOLEAN | |
993 | Enable IP forwarding on this interface. | |
994 | ||
995 | mc_forwarding - BOOLEAN | |
996 | Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE | |
997 | and a multicast routing daemon is required. | |
998 | conf/all/mc_forwarding must also be set to TRUE to enable multicast | |
999 | routing for the interface | |
1000 | ||
1001 | medium_id - INTEGER | |
1002 | Integer value used to differentiate the devices by the medium they | |
1003 | are attached to. Two devices can have different id values when | |
1004 | the broadcast packets are received only on one of them. | |
1005 | The default value 0 means that the device is the only interface | |
1006 | to its medium, value of -1 means that medium is not known. | |
1007 | ||
1008 | Currently, it is used to change the proxy_arp behavior: | |
1009 | the proxy_arp feature is enabled for packets forwarded between | |
1010 | two devices attached to different media. | |
1011 | ||
1012 | proxy_arp - BOOLEAN | |
1013 | Do proxy arp. | |
1014 | proxy_arp for the interface will be enabled if at least one of | |
1015 | conf/{all,interface}/proxy_arp is set to TRUE, | |
1016 | it will be disabled otherwise | |
1017 | ||
1018 | proxy_arp_pvlan - BOOLEAN | |
1019 | Private VLAN proxy arp. | |
1020 | Basically allow proxy arp replies back to the same interface | |
1021 | (from which the ARP request/solicitation was received). | |
1022 | ||
1023 | This is done to support (ethernet) switch features, like RFC | |
1024 | 3069, where the individual ports are NOT allowed to | |
1025 | communicate with each other, but they are allowed to talk to | |
1026 | the upstream router. As described in RFC 3069, it is possible | |
1027 | to allow these hosts to communicate through the upstream | |
1028 | router by proxy_arp'ing. Don't need to be used together with | |
1029 | proxy_arp. | |
1030 | ||
1031 | This technology is known by different names: | |
1032 | In RFC 3069 it is called VLAN Aggregation. | |
1033 | Cisco and Allied Telesyn call it Private VLAN. | |
1034 | Hewlett-Packard call it Source-Port filtering or port-isolation. | |
1035 | Ericsson call it MAC-Forced Forwarding (RFC Draft). | |
1036 | ||
1037 | shared_media - BOOLEAN | |
1038 | Send(router) or accept(host) RFC1620 shared media redirects. | |
1039 | Overrides secure_redirects. | |
1040 | shared_media for the interface will be enabled if at least one of | |
1041 | conf/{all,interface}/shared_media is set to TRUE, | |
1042 | it will be disabled otherwise | |
1043 | default TRUE | |
1044 | ||
1045 | secure_redirects - BOOLEAN | |
1046 | Accept ICMP redirect messages only to gateways listed in the | |
1047 | interface's current gateway list. Even if disabled, RFC1122 redirect | |
1048 | rules still apply. | |
1049 | Overridden by shared_media. | |
1050 | secure_redirects for the interface will be enabled if at least one of | |
1051 | conf/{all,interface}/secure_redirects is set to TRUE, | |
1052 | it will be disabled otherwise | |
1053 | default TRUE | |
1054 | ||
1055 | send_redirects - BOOLEAN | |
1056 | Send redirects, if router. | |
1057 | send_redirects for the interface will be enabled if at least one of | |
1058 | conf/{all,interface}/send_redirects is set to TRUE, | |
1059 | it will be disabled otherwise | |
1060 | Default: TRUE | |
1061 | ||
1062 | bootp_relay - BOOLEAN | |
1063 | Accept packets with source address 0.b.c.d destined | |
1064 | not to this host as local ones. It is supposed, that | |
1065 | BOOTP relay daemon will catch and forward such packets. | |
1066 | conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay | |
1067 | for the interface | |
1068 | default FALSE | |
1069 | Not Implemented Yet. | |
1070 | ||
1071 | accept_source_route - BOOLEAN | |
1072 | Accept packets with SRR option. | |
1073 | conf/all/accept_source_route must also be set to TRUE to accept packets | |
1074 | with SRR option on the interface | |
1075 | default TRUE (router) | |
1076 | FALSE (host) | |
1077 | ||
1078 | accept_local - BOOLEAN | |
1079 | Accept packets with local source addresses. In combination with | |
1080 | suitable routing, this can be used to direct packets between two | |
1081 | local interfaces over the wire and have them accepted properly. | |
1082 | default FALSE | |
1083 | ||
1084 | route_localnet - BOOLEAN | |
1085 | Do not consider loopback addresses as martian source or destination | |
1086 | while routing. This enables the use of 127/8 for local routing purposes. | |
1087 | default FALSE | |
1088 | ||
1089 | rp_filter - INTEGER | |
1090 | 0 - No source validation. | |
1091 | 1 - Strict mode as defined in RFC3704 Strict Reverse Path | |
1092 | Each incoming packet is tested against the FIB and if the interface | |
1093 | is not the best reverse path the packet check will fail. | |
1094 | By default failed packets are discarded. | |
1095 | 2 - Loose mode as defined in RFC3704 Loose Reverse Path | |
1096 | Each incoming packet's source address is also tested against the FIB | |
1097 | and if the source address is not reachable via any interface | |
1098 | the packet check will fail. | |
1099 | ||
1100 | Current recommended practice in RFC3704 is to enable strict mode | |
1101 | to prevent IP spoofing from DDos attacks. If using asymmetric routing | |
1102 | or other complicated routing, then loose mode is recommended. | |
1103 | ||
1104 | The max value from conf/{all,interface}/rp_filter is used | |
1105 | when doing source validation on the {interface}. | |
1106 | ||
1107 | Default value is 0. Note that some distributions enable it | |
1108 | in startup scripts. | |
1109 | ||
1110 | arp_filter - BOOLEAN | |
1111 | 1 - Allows you to have multiple network interfaces on the same | |
1112 | subnet, and have the ARPs for each interface be answered | |
1113 | based on whether or not the kernel would route a packet from | |
1114 | the ARP'd IP out that interface (therefore you must use source | |
1115 | based routing for this to work). In other words it allows control | |
1116 | of which cards (usually 1) will respond to an arp request. | |
1117 | ||
1118 | 0 - (default) The kernel can respond to arp requests with addresses | |
1119 | from other interfaces. This may seem wrong but it usually makes | |
1120 | sense, because it increases the chance of successful communication. | |
1121 | IP addresses are owned by the complete host on Linux, not by | |
1122 | particular interfaces. Only for more complex setups like load- | |
1123 | balancing, does this behaviour cause problems. | |
1124 | ||
1125 | arp_filter for the interface will be enabled if at least one of | |
1126 | conf/{all,interface}/arp_filter is set to TRUE, | |
1127 | it will be disabled otherwise | |
1128 | ||
1129 | arp_announce - INTEGER | |
1130 | Define different restriction levels for announcing the local | |
1131 | source IP address from IP packets in ARP requests sent on | |
1132 | interface: | |
1133 | 0 - (default) Use any local address, configured on any interface | |
1134 | 1 - Try to avoid local addresses that are not in the target's | |
1135 | subnet for this interface. This mode is useful when target | |
1136 | hosts reachable via this interface require the source IP | |
1137 | address in ARP requests to be part of their logical network | |
1138 | configured on the receiving interface. When we generate the | |
1139 | request we will check all our subnets that include the | |
1140 | target IP and will preserve the source address if it is from | |
1141 | such subnet. If there is no such subnet we select source | |
1142 | address according to the rules for level 2. | |
1143 | 2 - Always use the best local address for this target. | |
1144 | In this mode we ignore the source address in the IP packet | |
1145 | and try to select local address that we prefer for talks with | |
1146 | the target host. Such local address is selected by looking | |
1147 | for primary IP addresses on all our subnets on the outgoing | |
1148 | interface that include the target IP address. If no suitable | |
1149 | local address is found we select the first local address | |
1150 | we have on the outgoing interface or on all other interfaces, | |
1151 | with the hope we will receive reply for our request and | |
1152 | even sometimes no matter the source IP address we announce. | |
1153 | ||
1154 | The max value from conf/{all,interface}/arp_announce is used. | |
1155 | ||
1156 | Increasing the restriction level gives more chance for | |
1157 | receiving answer from the resolved target while decreasing | |
1158 | the level announces more valid sender's information. | |
1159 | ||
1160 | arp_ignore - INTEGER | |
1161 | Define different modes for sending replies in response to | |
1162 | received ARP requests that resolve local target IP addresses: | |
1163 | 0 - (default): reply for any local target IP address, configured | |
1164 | on any interface | |
1165 | 1 - reply only if the target IP address is local address | |
1166 | configured on the incoming interface | |
1167 | 2 - reply only if the target IP address is local address | |
1168 | configured on the incoming interface and both with the | |
1169 | sender's IP address are part from same subnet on this interface | |
1170 | 3 - do not reply for local addresses configured with scope host, | |
1171 | only resolutions for global and link addresses are replied | |
1172 | 4-7 - reserved | |
1173 | 8 - do not reply for all local addresses | |
1174 | ||
1175 | The max value from conf/{all,interface}/arp_ignore is used | |
1176 | when ARP request is received on the {interface} | |
1177 | ||
1178 | arp_notify - BOOLEAN | |
1179 | Define mode for notification of address and device changes. | |
1180 | 0 - (default): do nothing | |
1181 | 1 - Generate gratuitous arp requests when device is brought up | |
1182 | or hardware address changes. | |
1183 | ||
1184 | arp_accept - BOOLEAN | |
1185 | Define behavior for gratuitous ARP frames who's IP is not | |
1186 | already present in the ARP table: | |
1187 | 0 - don't create new entries in the ARP table | |
1188 | 1 - create new entries in the ARP table | |
1189 | ||
1190 | Both replies and requests type gratuitous arp will trigger the | |
1191 | ARP table to be updated, if this setting is on. | |
1192 | ||
1193 | If the ARP table already contains the IP address of the | |
1194 | gratuitous arp frame, the arp table will be updated regardless | |
1195 | if this setting is on or off. | |
1196 | ||
1197 | mcast_solicit - INTEGER | |
1198 | The maximum number of multicast probes in INCOMPLETE state, | |
1199 | when the associated hardware address is unknown. Defaults | |
1200 | to 3. | |
1201 | ||
1202 | ucast_solicit - INTEGER | |
1203 | The maximum number of unicast probes in PROBE state, when | |
1204 | the hardware address is being reconfirmed. Defaults to 3. | |
1205 | ||
1206 | app_solicit - INTEGER | |
1207 | The maximum number of probes to send to the user space ARP daemon | |
1208 | via netlink before dropping back to multicast probes (see | |
1209 | mcast_resolicit). Defaults to 0. | |
1210 | ||
1211 | mcast_resolicit - INTEGER | |
1212 | The maximum number of multicast probes after unicast and | |
1213 | app probes in PROBE state. Defaults to 0. | |
1214 | ||
1215 | disable_policy - BOOLEAN | |
1216 | Disable IPSEC policy (SPD) for this interface | |
1217 | ||
1218 | disable_xfrm - BOOLEAN | |
1219 | Disable IPSEC encryption on this interface, whatever the policy | |
1220 | ||
1221 | igmpv2_unsolicited_report_interval - INTEGER | |
1222 | The interval in milliseconds in which the next unsolicited | |
1223 | IGMPv1 or IGMPv2 report retransmit will take place. | |
1224 | Default: 10000 (10 seconds) | |
1225 | ||
1226 | igmpv3_unsolicited_report_interval - INTEGER | |
1227 | The interval in milliseconds in which the next unsolicited | |
1228 | IGMPv3 report retransmit will take place. | |
1229 | Default: 1000 (1 seconds) | |
1230 | ||
1231 | promote_secondaries - BOOLEAN | |
1232 | When a primary IP address is removed from this interface | |
1233 | promote a corresponding secondary IP address instead of | |
1234 | removing all the corresponding secondary IP addresses. | |
1235 | ||
1236 | drop_unicast_in_l2_multicast - BOOLEAN | |
1237 | Drop any unicast IP packets that are received in link-layer | |
1238 | multicast (or broadcast) frames. | |
1239 | This behavior (for multicast) is actually a SHOULD in RFC | |
1240 | 1122, but is disabled by default for compatibility reasons. | |
1241 | Default: off (0) | |
1242 | ||
1243 | drop_gratuitous_arp - BOOLEAN | |
1244 | Drop all gratuitous ARP frames, for example if there's a known | |
1245 | good ARP proxy on the network and such frames need not be used | |
1246 | (or in the case of 802.11, must not be used to prevent attacks.) | |
1247 | Default: off (0) | |
1248 | ||
1249 | ||
1250 | tag - INTEGER | |
1251 | Allows you to write a number, which can be used as required. | |
1252 | Default value is 0. | |
1253 | ||
1254 | xfrm4_gc_thresh - INTEGER | |
1255 | The threshold at which we will start garbage collecting for IPv4 | |
1256 | destination cache entries. At twice this value the system will | |
1257 | refuse new allocations. The value must be set below the flowcache | |
1258 | limit (4096 * number of online cpus) to take effect. | |
1259 | ||
1260 | igmp_link_local_mcast_reports - BOOLEAN | |
1261 | Enable IGMP reports for link local multicast groups in the | |
1262 | 224.0.0.X range. | |
1263 | Default TRUE | |
1264 | ||
1265 | Alexey Kuznetsov. | |
1266 | kuznet@ms2.inr.ac.ru | |
1267 | ||
1268 | Updated by: | |
1269 | Andi Kleen | |
1270 | ak@muc.de | |
1271 | Nicolas Delon | |
1272 | delon.nicolas@wanadoo.fr | |
1273 | ||
1274 | ||
1275 | ||
1276 | ||
1277 | /proc/sys/net/ipv6/* Variables: | |
1278 | ||
1279 | IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also | |
1280 | apply to IPv6 [XXX?]. | |
1281 | ||
1282 | bindv6only - BOOLEAN | |
1283 | Default value for IPV6_V6ONLY socket option, | |
1284 | which restricts use of the IPv6 socket to IPv6 communication | |
1285 | only. | |
1286 | TRUE: disable IPv4-mapped address feature | |
1287 | FALSE: enable IPv4-mapped address feature | |
1288 | ||
1289 | Default: FALSE (as specified in RFC3493) | |
1290 | ||
1291 | flowlabel_consistency - BOOLEAN | |
1292 | Protect the consistency (and unicity) of flow label. | |
1293 | You have to disable it to use IPV6_FL_F_REFLECT flag on the | |
1294 | flow label manager. | |
1295 | TRUE: enabled | |
1296 | FALSE: disabled | |
1297 | Default: TRUE | |
1298 | ||
1299 | auto_flowlabels - INTEGER | |
1300 | Automatically generate flow labels based on a flow hash of the | |
1301 | packet. This allows intermediate devices, such as routers, to | |
1302 | identify packet flows for mechanisms like Equal Cost Multipath | |
1303 | Routing (see RFC 6438). | |
1304 | 0: automatic flow labels are completely disabled | |
1305 | 1: automatic flow labels are enabled by default, they can be | |
1306 | disabled on a per socket basis using the IPV6_AUTOFLOWLABEL | |
1307 | socket option | |
1308 | 2: automatic flow labels are allowed, they may be enabled on a | |
1309 | per socket basis using the IPV6_AUTOFLOWLABEL socket option | |
1310 | 3: automatic flow labels are enabled and enforced, they cannot | |
1311 | be disabled by the socket option | |
1312 | Default: 1 | |
1313 | ||
1314 | flowlabel_state_ranges - BOOLEAN | |
1315 | Split the flow label number space into two ranges. 0-0x7FFFF is | |
1316 | reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF | |
1317 | is reserved for stateless flow labels as described in RFC6437. | |
1318 | TRUE: enabled | |
1319 | FALSE: disabled | |
1320 | Default: true | |
1321 | ||
1322 | anycast_src_echo_reply - BOOLEAN | |
1323 | Controls the use of anycast addresses as source addresses for ICMPv6 | |
1324 | echo reply | |
1325 | TRUE: enabled | |
1326 | FALSE: disabled | |
1327 | Default: FALSE | |
1328 | ||
1329 | idgen_delay - INTEGER | |
1330 | Controls the delay in seconds after which time to retry | |
1331 | privacy stable address generation if a DAD conflict is | |
1332 | detected. | |
1333 | Default: 1 (as specified in RFC7217) | |
1334 | ||
1335 | idgen_retries - INTEGER | |
1336 | Controls the number of retries to generate a stable privacy | |
1337 | address if a DAD conflict is detected. | |
1338 | Default: 3 (as specified in RFC7217) | |
1339 | ||
1340 | mld_qrv - INTEGER | |
1341 | Controls the MLD query robustness variable (see RFC3810 9.1). | |
1342 | Default: 2 (as specified by RFC3810 9.1) | |
1343 | Minimum: 1 (as specified by RFC6636 4.5) | |
1344 | ||
1345 | IPv6 Fragmentation: | |
1346 | ||
1347 | ip6frag_high_thresh - INTEGER | |
1348 | Maximum memory used to reassemble IPv6 fragments. When | |
1349 | ip6frag_high_thresh bytes of memory is allocated for this purpose, | |
1350 | the fragment handler will toss packets until ip6frag_low_thresh | |
1351 | is reached. | |
1352 | ||
1353 | ip6frag_low_thresh - INTEGER | |
1354 | See ip6frag_high_thresh | |
1355 | ||
1356 | ip6frag_time - INTEGER | |
1357 | Time in seconds to keep an IPv6 fragment in memory. | |
1358 | ||
1359 | conf/default/*: | |
1360 | Change the interface-specific default settings. | |
1361 | ||
1362 | ||
1363 | conf/all/*: | |
1364 | Change all the interface-specific settings. | |
1365 | ||
1366 | [XXX: Other special features than forwarding?] | |
1367 | ||
1368 | conf/all/forwarding - BOOLEAN | |
1369 | Enable global IPv6 forwarding between all interfaces. | |
1370 | ||
1371 | IPv4 and IPv6 work differently here; e.g. netfilter must be used | |
1372 | to control which interfaces may forward packets and which not. | |
1373 | ||
1374 | This also sets all interfaces' Host/Router setting | |
1375 | 'forwarding' to the specified value. See below for details. | |
1376 | ||
1377 | This referred to as global forwarding. | |
1378 | ||
1379 | proxy_ndp - BOOLEAN | |
1380 | Do proxy ndp. | |
1381 | ||
1382 | fwmark_reflect - BOOLEAN | |
1383 | Controls the fwmark of kernel-generated IPv6 reply packets that are not | |
1384 | associated with a socket for example, TCP RSTs or ICMPv6 echo replies). | |
1385 | If unset, these packets have a fwmark of zero. If set, they have the | |
1386 | fwmark of the packet they are replying to. | |
1387 | Default: 0 | |
1388 | ||
1389 | conf/interface/*: | |
1390 | Change special settings per interface. | |
1391 | ||
1392 | The functional behaviour for certain settings is different | |
1393 | depending on whether local forwarding is enabled or not. | |
1394 | ||
1395 | accept_ra - INTEGER | |
1396 | Accept Router Advertisements; autoconfigure using them. | |
1397 | ||
1398 | It also determines whether or not to transmit Router | |
1399 | Solicitations. If and only if the functional setting is to | |
1400 | accept Router Advertisements, Router Solicitations will be | |
1401 | transmitted. | |
1402 | ||
1403 | Possible values are: | |
1404 | 0 Do not accept Router Advertisements. | |
1405 | 1 Accept Router Advertisements if forwarding is disabled. | |
1406 | 2 Overrule forwarding behaviour. Accept Router Advertisements | |
1407 | even if forwarding is enabled. | |
1408 | ||
1409 | Functional default: enabled if local forwarding is disabled. | |
1410 | disabled if local forwarding is enabled. | |
1411 | ||
1412 | accept_ra_defrtr - BOOLEAN | |
1413 | Learn default router in Router Advertisement. | |
1414 | ||
1415 | Functional default: enabled if accept_ra is enabled. | |
1416 | disabled if accept_ra is disabled. | |
1417 | ||
1418 | accept_ra_from_local - BOOLEAN | |
1419 | Accept RA with source-address that is found on local machine | |
1420 | if the RA is otherwise proper and able to be accepted. | |
1421 | Default is to NOT accept these as it may be an un-intended | |
1422 | network loop. | |
1423 | ||
1424 | Functional default: | |
1425 | enabled if accept_ra_from_local is enabled | |
1426 | on a specific interface. | |
1427 | disabled if accept_ra_from_local is disabled | |
1428 | on a specific interface. | |
1429 | ||
1430 | accept_ra_min_hop_limit - INTEGER | |
1431 | Minimum hop limit Information in Router Advertisement. | |
1432 | ||
1433 | Hop limit Information in Router Advertisement less than this | |
1434 | variable shall be ignored. | |
1435 | ||
1436 | Default: 1 | |
1437 | ||
1438 | accept_ra_pinfo - BOOLEAN | |
1439 | Learn Prefix Information in Router Advertisement. | |
1440 | ||
1441 | Functional default: enabled if accept_ra is enabled. | |
1442 | disabled if accept_ra is disabled. | |
1443 | ||
1444 | accept_ra_rt_info_max_plen - INTEGER | |
1445 | Maximum prefix length of Route Information in RA. | |
1446 | ||
1447 | Route Information w/ prefix larger than or equal to this | |
1448 | variable shall be ignored. | |
1449 | ||
1450 | Functional default: 0 if accept_ra_rtr_pref is enabled. | |
1451 | -1 if accept_ra_rtr_pref is disabled. | |
1452 | ||
1453 | accept_ra_rtr_pref - BOOLEAN | |
1454 | Accept Router Preference in RA. | |
1455 | ||
1456 | Functional default: enabled if accept_ra is enabled. | |
1457 | disabled if accept_ra is disabled. | |
1458 | ||
1459 | accept_ra_mtu - BOOLEAN | |
1460 | Apply the MTU value specified in RA option 5 (RFC4861). If | |
1461 | disabled, the MTU specified in the RA will be ignored. | |
1462 | ||
1463 | Functional default: enabled if accept_ra is enabled. | |
1464 | disabled if accept_ra is disabled. | |
1465 | ||
1466 | accept_redirects - BOOLEAN | |
1467 | Accept Redirects. | |
1468 | ||
1469 | Functional default: enabled if local forwarding is disabled. | |
1470 | disabled if local forwarding is enabled. | |
1471 | ||
1472 | accept_source_route - INTEGER | |
1473 | Accept source routing (routing extension header). | |
1474 | ||
1475 | >= 0: Accept only routing header type 2. | |
1476 | < 0: Do not accept routing header. | |
1477 | ||
1478 | Default: 0 | |
1479 | ||
1480 | autoconf - BOOLEAN | |
1481 | Autoconfigure addresses using Prefix Information in Router | |
1482 | Advertisements. | |
1483 | ||
1484 | Functional default: enabled if accept_ra_pinfo is enabled. | |
1485 | disabled if accept_ra_pinfo is disabled. | |
1486 | ||
1487 | dad_transmits - INTEGER | |
1488 | The amount of Duplicate Address Detection probes to send. | |
1489 | Default: 1 | |
1490 | ||
1491 | forwarding - INTEGER | |
1492 | Configure interface-specific Host/Router behaviour. | |
1493 | ||
1494 | Note: It is recommended to have the same setting on all | |
1495 | interfaces; mixed router/host scenarios are rather uncommon. | |
1496 | ||
1497 | Possible values are: | |
1498 | 0 Forwarding disabled | |
1499 | 1 Forwarding enabled | |
1500 | ||
1501 | FALSE (0): | |
1502 | ||
1503 | By default, Host behaviour is assumed. This means: | |
1504 | ||
1505 | 1. IsRouter flag is not set in Neighbour Advertisements. | |
1506 | 2. If accept_ra is TRUE (default), transmit Router | |
1507 | Solicitations. | |
1508 | 3. If accept_ra is TRUE (default), accept Router | |
1509 | Advertisements (and do autoconfiguration). | |
1510 | 4. If accept_redirects is TRUE (default), accept Redirects. | |
1511 | ||
1512 | TRUE (1): | |
1513 | ||
1514 | If local forwarding is enabled, Router behaviour is assumed. | |
1515 | This means exactly the reverse from the above: | |
1516 | ||
1517 | 1. IsRouter flag is set in Neighbour Advertisements. | |
1518 | 2. Router Solicitations are not sent unless accept_ra is 2. | |
1519 | 3. Router Advertisements are ignored unless accept_ra is 2. | |
1520 | 4. Redirects are ignored. | |
1521 | ||
1522 | Default: 0 (disabled) if global forwarding is disabled (default), | |
1523 | otherwise 1 (enabled). | |
1524 | ||
1525 | hop_limit - INTEGER | |
1526 | Default Hop Limit to set. | |
1527 | Default: 64 | |
1528 | ||
1529 | mtu - INTEGER | |
1530 | Default Maximum Transfer Unit | |
1531 | Default: 1280 (IPv6 required minimum) | |
1532 | ||
1533 | ip_nonlocal_bind - BOOLEAN | |
1534 | If set, allows processes to bind() to non-local IPv6 addresses, | |
1535 | which can be quite useful - but may break some applications. | |
1536 | Default: 0 | |
1537 | ||
1538 | router_probe_interval - INTEGER | |
1539 | Minimum interval (in seconds) between Router Probing described | |
1540 | in RFC4191. | |
1541 | ||
1542 | Default: 60 | |
1543 | ||
1544 | router_solicitation_delay - INTEGER | |
1545 | Number of seconds to wait after interface is brought up | |
1546 | before sending Router Solicitations. | |
1547 | Default: 1 | |
1548 | ||
1549 | router_solicitation_interval - INTEGER | |
1550 | Number of seconds to wait between Router Solicitations. | |
1551 | Default: 4 | |
1552 | ||
1553 | router_solicitations - INTEGER | |
1554 | Number of Router Solicitations to send until assuming no | |
1555 | routers are present. | |
1556 | Default: 3 | |
1557 | ||
1558 | use_oif_addrs_only - BOOLEAN | |
1559 | When enabled, the candidate source addresses for destinations | |
1560 | routed via this interface are restricted to the set of addresses | |
1561 | configured on this interface (vis. RFC 6724, section 4). | |
1562 | ||
1563 | Default: false | |
1564 | ||
1565 | use_tempaddr - INTEGER | |
1566 | Preference for Privacy Extensions (RFC3041). | |
1567 | <= 0 : disable Privacy Extensions | |
1568 | == 1 : enable Privacy Extensions, but prefer public | |
1569 | addresses over temporary addresses. | |
1570 | > 1 : enable Privacy Extensions and prefer temporary | |
1571 | addresses over public addresses. | |
1572 | Default: 0 (for most devices) | |
1573 | -1 (for point-to-point devices and loopback devices) | |
1574 | ||
1575 | temp_valid_lft - INTEGER | |
1576 | valid lifetime (in seconds) for temporary addresses. | |
1577 | Default: 604800 (7 days) | |
1578 | ||
1579 | temp_prefered_lft - INTEGER | |
1580 | Preferred lifetime (in seconds) for temporary addresses. | |
1581 | Default: 86400 (1 day) | |
1582 | ||
1583 | keep_addr_on_down - INTEGER | |
1584 | Keep all IPv6 addresses on an interface down event. If set static | |
1585 | global addresses with no expiration time are not flushed. | |
1586 | >0 : enabled | |
1587 | 0 : system default | |
1588 | <0 : disabled | |
1589 | ||
1590 | Default: 0 (addresses are removed) | |
1591 | ||
1592 | max_desync_factor - INTEGER | |
1593 | Maximum value for DESYNC_FACTOR, which is a random value | |
1594 | that ensures that clients don't synchronize with each | |
1595 | other and generate new addresses at exactly the same time. | |
1596 | value is in seconds. | |
1597 | Default: 600 | |
1598 | ||
1599 | regen_max_retry - INTEGER | |
1600 | Number of attempts before give up attempting to generate | |
1601 | valid temporary addresses. | |
1602 | Default: 5 | |
1603 | ||
1604 | max_addresses - INTEGER | |
1605 | Maximum number of autoconfigured addresses per interface. Setting | |
1606 | to zero disables the limitation. It is not recommended to set this | |
1607 | value too large (or to zero) because it would be an easy way to | |
1608 | crash the kernel by allowing too many addresses to be created. | |
1609 | Default: 16 | |
1610 | ||
1611 | disable_ipv6 - BOOLEAN | |
1612 | Disable IPv6 operation. If accept_dad is set to 2, this value | |
1613 | will be dynamically set to TRUE if DAD fails for the link-local | |
1614 | address. | |
1615 | Default: FALSE (enable IPv6 operation) | |
1616 | ||
1617 | When this value is changed from 1 to 0 (IPv6 is being enabled), | |
1618 | it will dynamically create a link-local address on the given | |
1619 | interface and start Duplicate Address Detection, if necessary. | |
1620 | ||
1621 | When this value is changed from 0 to 1 (IPv6 is being disabled), | |
1622 | it will dynamically delete all address on the given interface. | |
1623 | ||
1624 | accept_dad - INTEGER | |
1625 | Whether to accept DAD (Duplicate Address Detection). | |
1626 | 0: Disable DAD | |
1627 | 1: Enable DAD (default) | |
1628 | 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate | |
1629 | link-local address has been found. | |
1630 | ||
1631 | force_tllao - BOOLEAN | |
1632 | Enable sending the target link-layer address option even when | |
1633 | responding to a unicast neighbor solicitation. | |
1634 | Default: FALSE | |
1635 | ||
1636 | Quoting from RFC 2461, section 4.4, Target link-layer address: | |
1637 | ||
1638 | "The option MUST be included for multicast solicitations in order to | |
1639 | avoid infinite Neighbor Solicitation "recursion" when the peer node | |
1640 | does not have a cache entry to return a Neighbor Advertisements | |
1641 | message. When responding to unicast solicitations, the option can be | |
1642 | omitted since the sender of the solicitation has the correct link- | |
1643 | layer address; otherwise it would not have be able to send the unicast | |
1644 | solicitation in the first place. However, including the link-layer | |
1645 | address in this case adds little overhead and eliminates a potential | |
1646 | race condition where the sender deletes the cached link-layer address | |
1647 | prior to receiving a response to a previous solicitation." | |
1648 | ||
1649 | ndisc_notify - BOOLEAN | |
1650 | Define mode for notification of address and device changes. | |
1651 | 0 - (default): do nothing | |
1652 | 1 - Generate unsolicited neighbour advertisements when device is brought | |
1653 | up or hardware address changes. | |
1654 | ||
1655 | mldv1_unsolicited_report_interval - INTEGER | |
1656 | The interval in milliseconds in which the next unsolicited | |
1657 | MLDv1 report retransmit will take place. | |
1658 | Default: 10000 (10 seconds) | |
1659 | ||
1660 | mldv2_unsolicited_report_interval - INTEGER | |
1661 | The interval in milliseconds in which the next unsolicited | |
1662 | MLDv2 report retransmit will take place. | |
1663 | Default: 1000 (1 second) | |
1664 | ||
1665 | force_mld_version - INTEGER | |
1666 | 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed | |
1667 | 1 - Enforce to use MLD version 1 | |
1668 | 2 - Enforce to use MLD version 2 | |
1669 | ||
1670 | suppress_frag_ndisc - INTEGER | |
1671 | Control RFC 6980 (Security Implications of IPv6 Fragmentation | |
1672 | with IPv6 Neighbor Discovery) behavior: | |
1673 | 1 - (default) discard fragmented neighbor discovery packets | |
1674 | 0 - allow fragmented neighbor discovery packets | |
1675 | ||
1676 | optimistic_dad - BOOLEAN | |
1677 | Whether to perform Optimistic Duplicate Address Detection (RFC 4429). | |
1678 | 0: disabled (default) | |
1679 | 1: enabled | |
1680 | ||
1681 | use_optimistic - BOOLEAN | |
1682 | If enabled, do not classify optimistic addresses as deprecated during | |
1683 | source address selection. Preferred addresses will still be chosen | |
1684 | before optimistic addresses, subject to other ranking in the source | |
1685 | address selection algorithm. | |
1686 | 0: disabled (default) | |
1687 | 1: enabled | |
1688 | ||
1689 | stable_secret - IPv6 address | |
1690 | This IPv6 address will be used as a secret to generate IPv6 | |
1691 | addresses for link-local addresses and autoconfigured | |
1692 | ones. All addresses generated after setting this secret will | |
1693 | be stable privacy ones by default. This can be changed via the | |
1694 | addrgenmode ip-link. conf/default/stable_secret is used as the | |
1695 | secret for the namespace, the interface specific ones can | |
1696 | overwrite that. Writes to conf/all/stable_secret are refused. | |
1697 | ||
1698 | It is recommended to generate this secret during installation | |
1699 | of a system and keep it stable after that. | |
1700 | ||
1701 | By default the stable secret is unset. | |
1702 | ||
1703 | drop_unicast_in_l2_multicast - BOOLEAN | |
1704 | Drop any unicast IPv6 packets that are received in link-layer | |
1705 | multicast (or broadcast) frames. | |
1706 | ||
1707 | By default this is turned off. | |
1708 | ||
1709 | drop_unsolicited_na - BOOLEAN | |
1710 | Drop all unsolicited neighbor advertisements, for example if there's | |
1711 | a known good NA proxy on the network and such frames need not be used | |
1712 | (or in the case of 802.11, must not be used to prevent attacks.) | |
1713 | ||
1714 | By default this is turned off. | |
1715 | ||
1716 | icmp/*: | |
1717 | ratelimit - INTEGER | |
1718 | Limit the maximal rates for sending ICMPv6 packets. | |
1719 | 0 to disable any limiting, | |
1720 | otherwise the minimal space between responses in milliseconds. | |
1721 | Default: 1000 | |
1722 | ||
1723 | xfrm6_gc_thresh - INTEGER | |
1724 | The threshold at which we will start garbage collecting for IPv6 | |
1725 | destination cache entries. At twice this value the system will | |
1726 | refuse new allocations. The value must be set below the flowcache | |
1727 | limit (4096 * number of online cpus) to take effect. | |
1728 | ||
1729 | ||
1730 | IPv6 Update by: | |
1731 | Pekka Savola <pekkas@netcore.fi> | |
1732 | YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> | |
1733 | ||
1734 | ||
1735 | /proc/sys/net/bridge/* Variables: | |
1736 | ||
1737 | bridge-nf-call-arptables - BOOLEAN | |
1738 | 1 : pass bridged ARP traffic to arptables' FORWARD chain. | |
1739 | 0 : disable this. | |
1740 | Default: 1 | |
1741 | ||
1742 | bridge-nf-call-iptables - BOOLEAN | |
1743 | 1 : pass bridged IPv4 traffic to iptables' chains. | |
1744 | 0 : disable this. | |
1745 | Default: 1 | |
1746 | ||
1747 | bridge-nf-call-ip6tables - BOOLEAN | |
1748 | 1 : pass bridged IPv6 traffic to ip6tables' chains. | |
1749 | 0 : disable this. | |
1750 | Default: 1 | |
1751 | ||
1752 | bridge-nf-filter-vlan-tagged - BOOLEAN | |
1753 | 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables. | |
1754 | 0 : disable this. | |
1755 | Default: 0 | |
1756 | ||
1757 | bridge-nf-filter-pppoe-tagged - BOOLEAN | |
1758 | 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. | |
1759 | 0 : disable this. | |
1760 | Default: 0 | |
1761 | ||
1762 | bridge-nf-pass-vlan-input-dev - BOOLEAN | |
1763 | 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan | |
1764 | interface on the bridge and set the netfilter input device to the vlan. | |
1765 | This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT | |
1766 | target work with vlan-on-top-of-bridge interfaces. When no matching | |
1767 | vlan interface is found, or this switch is off, the input device is | |
1768 | set to the bridge interface. | |
1769 | 0: disable bridge netfilter vlan interface lookup. | |
1770 | Default: 0 | |
1771 | ||
1772 | proc/sys/net/sctp/* Variables: | |
1773 | ||
1774 | addip_enable - BOOLEAN | |
1775 | Enable or disable extension of Dynamic Address Reconfiguration | |
1776 | (ADD-IP) functionality specified in RFC5061. This extension provides | |
1777 | the ability to dynamically add and remove new addresses for the SCTP | |
1778 | associations. | |
1779 | ||
1780 | 1: Enable extension. | |
1781 | ||
1782 | 0: Disable extension. | |
1783 | ||
1784 | Default: 0 | |
1785 | ||
1786 | pf_enable - INTEGER | |
1787 | Enable or disable pf (pf is short for potentially failed) state. A value | |
1788 | of pf_retrans > path_max_retrans also disables pf state. That is, one of | |
1789 | both pf_enable and pf_retrans > path_max_retrans can disable pf state. | |
1790 | Since pf_retrans and path_max_retrans can be changed by userspace | |
1791 | application, sometimes user expects to disable pf state by the value of | |
1792 | pf_retrans > path_max_retrans, but occasionally the value of pf_retrans | |
1793 | or path_max_retrans is changed by the user application, this pf state is | |
1794 | enabled. As such, it is necessary to add this to dynamically enable | |
1795 | and disable pf state. See: | |
1796 | https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for | |
1797 | details. | |
1798 | ||
1799 | 1: Enable pf. | |
1800 | ||
1801 | 0: Disable pf. | |
1802 | ||
1803 | Default: 1 | |
1804 | ||
1805 | addip_noauth_enable - BOOLEAN | |
1806 | Dynamic Address Reconfiguration (ADD-IP) requires the use of | |
1807 | authentication to protect the operations of adding or removing new | |
1808 | addresses. This requirement is mandated so that unauthorized hosts | |
1809 | would not be able to hijack associations. However, older | |
1810 | implementations may not have implemented this requirement while | |
1811 | allowing the ADD-IP extension. For reasons of interoperability, | |
1812 | we provide this variable to control the enforcement of the | |
1813 | authentication requirement. | |
1814 | ||
1815 | 1: Allow ADD-IP extension to be used without authentication. This | |
1816 | should only be set in a closed environment for interoperability | |
1817 | with older implementations. | |
1818 | ||
1819 | 0: Enforce the authentication requirement | |
1820 | ||
1821 | Default: 0 | |
1822 | ||
1823 | auth_enable - BOOLEAN | |
1824 | Enable or disable Authenticated Chunks extension. This extension | |
1825 | provides the ability to send and receive authenticated chunks and is | |
1826 | required for secure operation of Dynamic Address Reconfiguration | |
1827 | (ADD-IP) extension. | |
1828 | ||
1829 | 1: Enable this extension. | |
1830 | 0: Disable this extension. | |
1831 | ||
1832 | Default: 0 | |
1833 | ||
1834 | prsctp_enable - BOOLEAN | |
1835 | Enable or disable the Partial Reliability extension (RFC3758) which | |
1836 | is used to notify peers that a given DATA should no longer be expected. | |
1837 | ||
1838 | 1: Enable extension | |
1839 | 0: Disable | |
1840 | ||
1841 | Default: 1 | |
1842 | ||
1843 | max_burst - INTEGER | |
1844 | The limit of the number of new packets that can be initially sent. It | |
1845 | controls how bursty the generated traffic can be. | |
1846 | ||
1847 | Default: 4 | |
1848 | ||
1849 | association_max_retrans - INTEGER | |
1850 | Set the maximum number for retransmissions that an association can | |
1851 | attempt deciding that the remote end is unreachable. If this value | |
1852 | is exceeded, the association is terminated. | |
1853 | ||
1854 | Default: 10 | |
1855 | ||
1856 | max_init_retransmits - INTEGER | |
1857 | The maximum number of retransmissions of INIT and COOKIE-ECHO chunks | |
1858 | that an association will attempt before declaring the destination | |
1859 | unreachable and terminating. | |
1860 | ||
1861 | Default: 8 | |
1862 | ||
1863 | path_max_retrans - INTEGER | |
1864 | The maximum number of retransmissions that will be attempted on a given | |
1865 | path. Once this threshold is exceeded, the path is considered | |
1866 | unreachable, and new traffic will use a different path when the | |
1867 | association is multihomed. | |
1868 | ||
1869 | Default: 5 | |
1870 | ||
1871 | pf_retrans - INTEGER | |
1872 | The number of retransmissions that will be attempted on a given path | |
1873 | before traffic is redirected to an alternate transport (should one | |
1874 | exist). Note this is distinct from path_max_retrans, as a path that | |
1875 | passes the pf_retrans threshold can still be used. Its only | |
1876 | deprioritized when a transmission path is selected by the stack. This | |
1877 | setting is primarily used to enable fast failover mechanisms without | |
1878 | having to reduce path_max_retrans to a very low value. See: | |
1879 | http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt | |
1880 | for details. Note also that a value of pf_retrans > path_max_retrans | |
1881 | disables this feature. Since both pf_retrans and path_max_retrans can | |
1882 | be changed by userspace application, a variable pf_enable is used to | |
1883 | disable pf state. | |
1884 | ||
1885 | Default: 0 | |
1886 | ||
1887 | rto_initial - INTEGER | |
1888 | The initial round trip timeout value in milliseconds that will be used | |
1889 | in calculating round trip times. This is the initial time interval | |
1890 | for retransmissions. | |
1891 | ||
1892 | Default: 3000 | |
1893 | ||
1894 | rto_max - INTEGER | |
1895 | The maximum value (in milliseconds) of the round trip timeout. This | |
1896 | is the largest time interval that can elapse between retransmissions. | |
1897 | ||
1898 | Default: 60000 | |
1899 | ||
1900 | rto_min - INTEGER | |
1901 | The minimum value (in milliseconds) of the round trip timeout. This | |
1902 | is the smallest time interval the can elapse between retransmissions. | |
1903 | ||
1904 | Default: 1000 | |
1905 | ||
1906 | hb_interval - INTEGER | |
1907 | The interval (in milliseconds) between HEARTBEAT chunks. These chunks | |
1908 | are sent at the specified interval on idle paths to probe the state of | |
1909 | a given path between 2 associations. | |
1910 | ||
1911 | Default: 30000 | |
1912 | ||
1913 | sack_timeout - INTEGER | |
1914 | The amount of time (in milliseconds) that the implementation will wait | |
1915 | to send a SACK. | |
1916 | ||
1917 | Default: 200 | |
1918 | ||
1919 | valid_cookie_life - INTEGER | |
1920 | The default lifetime of the SCTP cookie (in milliseconds). The cookie | |
1921 | is used during association establishment. | |
1922 | ||
1923 | Default: 60000 | |
1924 | ||
1925 | cookie_preserve_enable - BOOLEAN | |
1926 | Enable or disable the ability to extend the lifetime of the SCTP cookie | |
1927 | that is used during the establishment phase of SCTP association | |
1928 | ||
1929 | 1: Enable cookie lifetime extension. | |
1930 | 0: Disable | |
1931 | ||
1932 | Default: 1 | |
1933 | ||
1934 | cookie_hmac_alg - STRING | |
1935 | Select the hmac algorithm used when generating the cookie value sent by | |
1936 | a listening sctp socket to a connecting client in the INIT-ACK chunk. | |
1937 | Valid values are: | |
1938 | * md5 | |
1939 | * sha1 | |
1940 | * none | |
1941 | Ability to assign md5 or sha1 as the selected alg is predicated on the | |
1942 | configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and | |
1943 | CONFIG_CRYPTO_SHA1). | |
1944 | ||
1945 | Default: Dependent on configuration. MD5 if available, else SHA1 if | |
1946 | available, else none. | |
1947 | ||
1948 | rcvbuf_policy - INTEGER | |
1949 | Determines if the receive buffer is attributed to the socket or to | |
1950 | association. SCTP supports the capability to create multiple | |
1951 | associations on a single socket. When using this capability, it is | |
1952 | possible that a single stalled association that's buffering a lot | |
1953 | of data may block other associations from delivering their data by | |
1954 | consuming all of the receive buffer space. To work around this, | |
1955 | the rcvbuf_policy could be set to attribute the receiver buffer space | |
1956 | to each association instead of the socket. This prevents the described | |
1957 | blocking. | |
1958 | ||
1959 | 1: rcvbuf space is per association | |
1960 | 0: rcvbuf space is per socket | |
1961 | ||
1962 | Default: 0 | |
1963 | ||
1964 | sndbuf_policy - INTEGER | |
1965 | Similar to rcvbuf_policy above, this applies to send buffer space. | |
1966 | ||
1967 | 1: Send buffer is tracked per association | |
1968 | 0: Send buffer is tracked per socket. | |
1969 | ||
1970 | Default: 0 | |
1971 | ||
1972 | sctp_mem - vector of 3 INTEGERs: min, pressure, max | |
1973 | Number of pages allowed for queueing by all SCTP sockets. | |
1974 | ||
1975 | min: Below this number of pages SCTP is not bothered about its | |
1976 | memory appetite. When amount of memory allocated by SCTP exceeds | |
1977 | this number, SCTP starts to moderate memory usage. | |
1978 | ||
1979 | pressure: This value was introduced to follow format of tcp_mem. | |
1980 | ||
1981 | max: Number of pages allowed for queueing by all SCTP sockets. | |
1982 | ||
1983 | Default is calculated at boot time from amount of available memory. | |
1984 | ||
1985 | sctp_rmem - vector of 3 INTEGERs: min, default, max | |
1986 | Only the first value ("min") is used, "default" and "max" are | |
1987 | ignored. | |
1988 | ||
1989 | min: Minimal size of receive buffer used by SCTP socket. | |
1990 | It is guaranteed to each SCTP socket (but not association) even | |
1991 | under moderate memory pressure. | |
1992 | ||
1993 | Default: 1 page | |
1994 | ||
1995 | sctp_wmem - vector of 3 INTEGERs: min, default, max | |
1996 | Currently this tunable has no effect. | |
1997 | ||
1998 | addr_scope_policy - INTEGER | |
1999 | Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 | |
2000 | ||
2001 | 0 - Disable IPv4 address scoping | |
2002 | 1 - Enable IPv4 address scoping | |
2003 | 2 - Follow draft but allow IPv4 private addresses | |
2004 | 3 - Follow draft but allow IPv4 link local addresses | |
2005 | ||
2006 | Default: 1 | |
2007 | ||
2008 | ||
2009 | /proc/sys/net/core/* | |
2010 | Please see: Documentation/sysctl/net.txt for descriptions of these entries. | |
2011 | ||
2012 | ||
2013 | /proc/sys/net/unix/* | |
2014 | max_dgram_qlen - INTEGER | |
2015 | The maximum length of dgram socket receive queue | |
2016 | ||
2017 | Default: 10 | |
2018 | ||
2019 | ||
2020 | UNDOCUMENTED: | |
2021 | ||
2022 | /proc/sys/net/irda/* | |
2023 | fast_poll_increase FIXME | |
2024 | warn_noreply_time FIXME | |
2025 | discovery_slots FIXME | |
2026 | slot_timeout FIXME | |
2027 | max_baud_rate FIXME | |
2028 | discovery_timeout FIXME | |
2029 | lap_keepalive_time FIXME | |
2030 | max_noreply_time FIXME | |
2031 | max_tx_data_size FIXME | |
2032 | max_tx_window FIXME | |
2033 | min_tx_turn_time FIXME |