| blob | 10742902146fc1da3ae1c84a94929b42a79e29d0 |
1 /proc/sys/net/ipv4/* Variables:
3 ip_forward - BOOLEAN
4 0 - disabled (default)
5 not 0 - enabled
7 Forward Packets between interfaces.
9 This variable is special, its change resets all configuration
10 parameters to their default state (RFC1122 for hosts, RFC1812
11 for routers)
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)
18 ip_no_pmtu_disc - BOOLEAN
19 Disable Path MTU Discovery.
20 default FALSE
22 min_pmtu - INTEGER
23 default 552 - minimum discovered Path MTU
25 route/max_size - INTEGER
26 Maximum number of routes allowed in the kernel. Increase
27 this when using large numbers of interfaces and/or routes.
29 neigh/default/gc_thresh1 - INTEGER
30 Minimum number of entries to keep. Garbage collector will not
31 purge entries if there are fewer than this number.
32 Default: 128
34 neigh/default/gc_thresh3 - INTEGER
35 Maximum number of neighbor entries allowed. Increase this
36 when using large numbers of interfaces and when communicating
37 with large numbers of directly-connected peers.
38 Default: 1024
40 neigh/default/unres_qlen_bytes - INTEGER
41 The maximum number of bytes which may be used by packets
42 queued for each unresolved address by other network layers.
43 (added in linux 3.3)
44 Setting negative value is meaningless and will return error.
45 Default: 65536 Bytes(64KB)
47 neigh/default/unres_qlen - INTEGER
48 The maximum number of packets which may be queued for each
49 unresolved address by other network layers.
50 (deprecated in linux 3.3) : use unres_qlen_bytes instead.
51 Prior to linux 3.3, the default value is 3 which may cause
52 unexpected packet loss. The current default value is calculated
53 according to default value of unres_qlen_bytes and true size of
54 packet.
55 Default: 31
57 mtu_expires - INTEGER
58 Time, in seconds, that cached PMTU information is kept.
60 min_adv_mss - INTEGER
61 The advertised MSS depends on the first hop route MTU, but will
62 never be lower than this setting.
64 IP Fragmentation:
66 ipfrag_high_thresh - INTEGER
67 Maximum memory used to reassemble IP fragments. When
68 ipfrag_high_thresh bytes of memory is allocated for this purpose,
69 the fragment handler will toss packets until ipfrag_low_thresh
70 is reached.
72 ipfrag_low_thresh - INTEGER
73 See ipfrag_high_thresh
75 ipfrag_time - INTEGER
76 Time in seconds to keep an IP fragment in memory.
78 ipfrag_secret_interval - INTEGER
79 Regeneration interval (in seconds) of the hash secret (or lifetime
80 for the hash secret) for IP fragments.
81 Default: 600
83 ipfrag_max_dist - INTEGER
84 ipfrag_max_dist is a non-negative integer value which defines the
85 maximum "disorder" which is allowed among fragments which share a
86 common IP source address. Note that reordering of packets is
87 not unusual, but if a large number of fragments arrive from a source
88 IP address while a particular fragment queue remains incomplete, it
89 probably indicates that one or more fragments belonging to that queue
90 have been lost. When ipfrag_max_dist is positive, an additional check
91 is done on fragments before they are added to a reassembly queue - if
92 ipfrag_max_dist (or more) fragments have arrived from a particular IP
93 address between additions to any IP fragment queue using that source
94 address, it's presumed that one or more fragments in the queue are
95 lost. The existing fragment queue will be dropped, and a new one
96 started. An ipfrag_max_dist value of zero disables this check.
98 Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
99 result in unnecessarily dropping fragment queues when normal
100 reordering of packets occurs, which could lead to poor application
101 performance. Using a very large value, e.g. 50000, increases the
102 likelihood of incorrectly reassembling IP fragments that originate
103 from different IP datagrams, which could result in data corruption.
104 Default: 64
106 INET peer storage:
108 inet_peer_threshold - INTEGER
109 The approximate size of the storage. Starting from this threshold
110 entries will be thrown aggressively. This threshold also determines
111 entries' time-to-live and time intervals between garbage collection
112 passes. More entries, less time-to-live, less GC interval.
114 inet_peer_minttl - INTEGER
115 Minimum time-to-live of entries. Should be enough to cover fragment
116 time-to-live on the reassembling side. This minimum time-to-live is
117 guaranteed if the pool size is less than inet_peer_threshold.
118 Measured in seconds.
120 inet_peer_maxttl - INTEGER
121 Maximum time-to-live of entries. Unused entries will expire after
122 this period of time if there is no memory pressure on the pool (i.e.
123 when the number of entries in the pool is very small).
124 Measured in seconds.
126 TCP variables:
128 somaxconn - INTEGER
129 Limit of socket listen() backlog, known in userspace as SOMAXCONN.
130 Defaults to 128. See also tcp_max_syn_backlog for additional tuning
131 for TCP sockets.
133 tcp_abort_on_overflow - BOOLEAN
134 If listening service is too slow to accept new connections,
135 reset them. Default state is FALSE. It means that if overflow
136 occurred due to a burst, connection will recover. Enable this
137 option _only_ if you are really sure that listening daemon
138 cannot be tuned to accept connections faster. Enabling this
139 option can harm clients of your server.
141 tcp_adv_win_scale - INTEGER
142 Count buffering overhead as bytes/2^tcp_adv_win_scale
143 (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
144 if it is <= 0.
145 Possible values are [-31, 31], inclusive.
146 Default: 1
148 tcp_allowed_congestion_control - STRING
149 Show/set the congestion control choices available to non-privileged
150 processes. The list is a subset of those listed in
151 tcp_available_congestion_control.
152 Default is "reno" and the default setting (tcp_congestion_control).
154 tcp_app_win - INTEGER
155 Reserve max(window/2^tcp_app_win, mss) of window for application
156 buffer. Value 0 is special, it means that nothing is reserved.
157 Default: 31
159 tcp_available_congestion_control - STRING
160 Shows the available congestion control choices that are registered.
161 More congestion control algorithms may be available as modules,
162 but not loaded.
164 tcp_base_mss - INTEGER
165 The initial value of search_low to be used by the packetization layer
166 Path MTU discovery (MTU probing). If MTU probing is enabled,
167 this is the initial MSS used by the connection.
169 tcp_congestion_control - STRING
170 Set the congestion control algorithm to be used for new
171 connections. The algorithm "reno" is always available, but
172 additional choices may be available based on kernel configuration.
173 Default is set as part of kernel configuration.
174 For passive connections, the listener congestion control choice
175 is inherited.
176 [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
178 tcp_dsack - BOOLEAN
179 Allows TCP to send "duplicate" SACKs.
181 tcp_early_retrans - INTEGER
182 Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold
183 for triggering fast retransmit when the amount of outstanding data is
184 small and when no previously unsent data can be transmitted (such
185 that limited transmit could be used). Also controls the use of
186 Tail loss probe (TLP) that converts RTOs occurring due to tail
187 losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01).
188 Possible values:
189 0 disables ER
190 1 enables ER
191 2 enables ER but delays fast recovery and fast retransmit
192 by a fourth of RTT. This mitigates connection falsely
193 recovers when network has a small degree of reordering
194 (less than 3 packets).
195 3 enables delayed ER and TLP.
196 4 enables TLP only.
197 Default: 3
199 tcp_ecn - INTEGER
200 Control use of Explicit Congestion Notification (ECN) by TCP.
201 ECN is used only when both ends of the TCP connection indicate
202 support for it. This feature is useful in avoiding losses due
203 to congestion by allowing supporting routers to signal
204 congestion before having to drop packets.
205 Possible values are:
206 0 Disable ECN. Neither initiate nor accept ECN.
207 1 Enable ECN when requested by incoming connections and
208 also request ECN on outgoing connection attempts.
209 2 Enable ECN when requested by incoming connections
210 but do not request ECN on outgoing connections.
211 Default: 2
213 tcp_fack - BOOLEAN
214 Enable FACK congestion avoidance and fast retransmission.
215 The value is not used, if tcp_sack is not enabled.
217 tcp_fin_timeout - INTEGER
218 The length of time an orphaned (no longer referenced by any
219 application) connection will remain in the FIN_WAIT_2 state
220 before it is aborted at the local end. While a perfectly
221 valid "receive only" state for an un-orphaned connection, an
222 orphaned connection in FIN_WAIT_2 state could otherwise wait
223 forever for the remote to close its end of the connection.
224 Cf. tcp_max_orphans
225 Default: 60 seconds
227 tcp_frto - INTEGER
228 Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
229 F-RTO is an enhanced recovery algorithm for TCP retransmission
230 timeouts. It is particularly beneficial in networks where the
231 RTT fluctuates (e.g., wireless). F-RTO is sender-side only
232 modification. It does not require any support from the peer.
234 By default it's enabled with a non-zero value. 0 disables F-RTO.
236 tcp_keepalive_time - INTEGER
237 How often TCP sends out keepalive messages when keepalive is enabled.
238 Default: 2hours.
240 tcp_keepalive_probes - INTEGER
241 How many keepalive probes TCP sends out, until it decides that the
242 connection is broken. Default value: 9.
244 tcp_keepalive_intvl - INTEGER
245 How frequently the probes are send out. Multiplied by
246 tcp_keepalive_probes it is time to kill not responding connection,
247 after probes started. Default value: 75sec i.e. connection
248 will be aborted after ~11 minutes of retries.
250 tcp_low_latency - BOOLEAN
251 If set, the TCP stack makes decisions that prefer lower
252 latency as opposed to higher throughput. By default, this
253 option is not set meaning that higher throughput is preferred.
254 An example of an application where this default should be
255 changed would be a Beowulf compute cluster.
256 Default: 0
258 tcp_max_orphans - INTEGER
259 Maximal number of TCP sockets not attached to any user file handle,
260 held by system. If this number is exceeded orphaned connections are
261 reset immediately and warning is printed. This limit exists
262 only to prevent simple DoS attacks, you _must_ not rely on this
263 or lower the limit artificially, but rather increase it
264 (probably, after increasing installed memory),
265 if network conditions require more than default value,
266 and tune network services to linger and kill such states
267 more aggressively. Let me to remind again: each orphan eats
268 up to ~64K of unswappable memory.
270 tcp_max_ssthresh - INTEGER
271 Limited Slow-Start for TCP with large congestion windows (cwnd) defined in
272 RFC3742. Limited slow-start is a mechanism to limit growth of the cwnd
273 on the region where cwnd is larger than tcp_max_ssthresh. TCP increases cwnd
274 by at most tcp_max_ssthresh segments, and by at least tcp_max_ssthresh/2
275 segments per RTT when the cwnd is above tcp_max_ssthresh.
276 If TCP connection increased cwnd to thousands (or tens of thousands) segments,
277 and thousands of packets were being dropped during slow-start, you can set
278 tcp_max_ssthresh to improve performance for new TCP connection.
279 Default: 0 (off)
281 tcp_max_syn_backlog - INTEGER
282 Maximal number of remembered connection requests, which have not
283 received an acknowledgment from connecting client.
284 The minimal value is 128 for low memory machines, and it will
285 increase in proportion to the memory of machine.
286 If server suffers from overload, try increasing this number.
288 tcp_max_tw_buckets - INTEGER
289 Maximal number of timewait sockets held by system simultaneously.
290 If this number is exceeded time-wait socket is immediately destroyed
291 and warning is printed. This limit exists only to prevent
292 simple DoS attacks, you _must_ not lower the limit artificially,
293 but rather increase it (probably, after increasing installed memory),
294 if network conditions require more than default value.
296 tcp_mem - vector of 3 INTEGERs: min, pressure, max
297 min: below this number of pages TCP is not bothered about its
298 memory appetite.
300 pressure: when amount of memory allocated by TCP exceeds this number
301 of pages, TCP moderates its memory consumption and enters memory
302 pressure mode, which is exited when memory consumption falls
303 under "min".
305 max: number of pages allowed for queueing by all TCP sockets.
307 Defaults are calculated at boot time from amount of available
308 memory.
310 tcp_moderate_rcvbuf - BOOLEAN
311 If set, TCP performs receive buffer auto-tuning, attempting to
312 automatically size the buffer (no greater than tcp_rmem[2]) to
313 match the size required by the path for full throughput. Enabled by
314 default.
316 tcp_mtu_probing - INTEGER
317 Controls TCP Packetization-Layer Path MTU Discovery. Takes three
318 values:
319 0 - Disabled
320 1 - Disabled by default, enabled when an ICMP black hole detected
321 2 - Always enabled, use initial MSS of tcp_base_mss.
323 tcp_no_metrics_save - BOOLEAN
324 By default, TCP saves various connection metrics in the route cache
325 when the connection closes, so that connections established in the
326 near future can use these to set initial conditions. Usually, this
327 increases overall performance, but may sometimes cause performance
328 degradation. If set, TCP will not cache metrics on closing
329 connections.
331 tcp_orphan_retries - INTEGER
332 This value influences the timeout of a locally closed TCP connection,
333 when RTO retransmissions remain unacknowledged.
334 See tcp_retries2 for more details.
336 The default value is 8.
337 If your machine is a loaded WEB server,
338 you should think about lowering this value, such sockets
339 may consume significant resources. Cf. tcp_max_orphans.
341 tcp_reordering - INTEGER
342 Maximal reordering of packets in a TCP stream.
343 Default: 3
345 tcp_retrans_collapse - BOOLEAN
346 Bug-to-bug compatibility with some broken printers.
347 On retransmit try to send bigger packets to work around bugs in
348 certain TCP stacks.
350 tcp_retries1 - INTEGER
351 This value influences the time, after which TCP decides, that
352 something is wrong due to unacknowledged RTO retransmissions,
353 and reports this suspicion to the network layer.
354 See tcp_retries2 for more details.
356 RFC 1122 recommends at least 3 retransmissions, which is the
357 default.
359 tcp_retries2 - INTEGER
360 This value influences the timeout of an alive TCP connection,
361 when RTO retransmissions remain unacknowledged.
362 Given a value of N, a hypothetical TCP connection following
363 exponential backoff with an initial RTO of TCP_RTO_MIN would
364 retransmit N times before killing the connection at the (N+1)th RTO.
366 The default value of 15 yields a hypothetical timeout of 924.6
367 seconds and is a lower bound for the effective timeout.
368 TCP will effectively time out at the first RTO which exceeds the
369 hypothetical timeout.
371 RFC 1122 recommends at least 100 seconds for the timeout,
372 which corresponds to a value of at least 8.
374 tcp_rfc1337 - BOOLEAN
375 If set, the TCP stack behaves conforming to RFC1337. If unset,
376 we are not conforming to RFC, but prevent TCP TIME_WAIT
377 assassination.
378 Default: 0
380 tcp_rmem - vector of 3 INTEGERs: min, default, max
381 min: Minimal size of receive buffer used by TCP sockets.
382 It is guaranteed to each TCP socket, even under moderate memory
383 pressure.
384 Default: 1 page
386 default: initial size of receive buffer used by TCP sockets.
387 This value overrides net.core.rmem_default used by other protocols.
388 Default: 87380 bytes. This value results in window of 65535 with
389 default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
390 less for default tcp_app_win. See below about these variables.
392 max: maximal size of receive buffer allowed for automatically
393 selected receiver buffers for TCP socket. This value does not override
394 net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
395 automatic tuning of that socket's receive buffer size, in which
396 case this value is ignored.
397 Default: between 87380B and 6MB, depending on RAM size.
399 tcp_sack - BOOLEAN
400 Enable select acknowledgments (SACKS).
402 tcp_slow_start_after_idle - BOOLEAN
403 If set, provide RFC2861 behavior and time out the congestion
404 window after an idle period. An idle period is defined at
405 the current RTO. If unset, the congestion window will not
406 be timed out after an idle period.
407 Default: 1
409 tcp_stdurg - BOOLEAN
410 Use the Host requirements interpretation of the TCP urgent pointer field.
411 Most hosts use the older BSD interpretation, so if you turn this on
412 Linux might not communicate correctly with them.
413 Default: FALSE
415 tcp_synack_retries - INTEGER
416 Number of times SYNACKs for a passive TCP connection attempt will
417 be retransmitted. Should not be higher than 255. Default value
418 is 5, which corresponds to 31seconds till the last retransmission
419 with the current initial RTO of 1second. With this the final timeout
420 for a passive TCP connection will happen after 63seconds.
422 tcp_syncookies - BOOLEAN
423 Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
424 Send out syncookies when the syn backlog queue of a socket
425 overflows. This is to prevent against the common 'SYN flood attack'
426 Default: 1
428 Note, that syncookies is fallback facility.
429 It MUST NOT be used to help highly loaded servers to stand
430 against legal connection rate. If you see SYN flood warnings
431 in your logs, but investigation shows that they occur
432 because of overload with legal connections, you should tune
433 another parameters until this warning disappear.
434 See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
436 syncookies seriously violate TCP protocol, do not allow
437 to use TCP extensions, can result in serious degradation
438 of some services (f.e. SMTP relaying), visible not by you,
439 but your clients and relays, contacting you. While you see
440 SYN flood warnings in logs not being really flooded, your server
441 is seriously misconfigured.
443 tcp_fastopen - INTEGER
444 Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
445 in the opening SYN packet. To use this feature, the client application
446 must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than
447 connect() to perform a TCP handshake automatically.
449 The values (bitmap) are
450 1: Enables sending data in the opening SYN on the client.
451 2: Enables TCP Fast Open on the server side, i.e., allowing data in
452 a SYN packet to be accepted and passed to the application before
453 3-way hand shake finishes.
454 4: Send data in the opening SYN regardless of cookie availability and
455 without a cookie option.
456 0x100: Accept SYN data w/o validating the cookie.
457 0x200: Accept data-in-SYN w/o any cookie option present.
458 0x400/0x800: Enable Fast Open on all listeners regardless of the
459 TCP_FASTOPEN socket option. The two different flags designate two
460 different ways of setting max_qlen without the TCP_FASTOPEN socket
461 option.
463 Default: 0
465 Note that the client & server side Fast Open flags (1 and 2
466 respectively) must be also enabled before the rest of flags can take
467 effect.
469 See include/net/tcp.h and the code for more details.
471 tcp_syn_retries - INTEGER
472 Number of times initial SYNs for an active TCP connection attempt
473 will be retransmitted. Should not be higher than 255. Default value
474 is 6, which corresponds to 63seconds till the last retransmission
475 with the current initial RTO of 1second. With this the final timeout
476 for an active TCP connection attempt will happen after 127seconds.
478 tcp_timestamps - BOOLEAN
479 Enable timestamps as defined in RFC1323.
481 tcp_tso_win_divisor - INTEGER
482 This allows control over what percentage of the congestion window
483 can be consumed by a single TSO frame.
484 The setting of this parameter is a choice between burstiness and
485 building larger TSO frames.
486 Default: 3
488 tcp_tw_recycle - BOOLEAN
489 Enable fast recycling TIME-WAIT sockets. Default value is 0.
490 It should not be changed without advice/request of technical
491 experts.
493 tcp_tw_reuse - BOOLEAN
494 Allow to reuse TIME-WAIT sockets for new connections when it is
495 safe from protocol viewpoint. Default value is 0.
496 It should not be changed without advice/request of technical
497 experts.
499 tcp_window_scaling - BOOLEAN
500 Enable window scaling as defined in RFC1323.
502 tcp_wmem - vector of 3 INTEGERs: min, default, max
503 min: Amount of memory reserved for send buffers for TCP sockets.
504 Each TCP socket has rights to use it due to fact of its birth.
505 Default: 1 page
507 default: initial size of send buffer used by TCP sockets. This
508 value overrides net.core.wmem_default used by other protocols.
509 It is usually lower than net.core.wmem_default.
510 Default: 16K
512 max: Maximal amount of memory allowed for automatically tuned
513 send buffers for TCP sockets. This value does not override
514 net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables
515 automatic tuning of that socket's send buffer size, in which case
516 this value is ignored.
517 Default: between 64K and 4MB, depending on RAM size.
519 tcp_workaround_signed_windows - BOOLEAN
520 If set, assume no receipt of a window scaling option means the
521 remote TCP is broken and treats the window as a signed quantity.
522 If unset, assume the remote TCP is not broken even if we do
523 not receive a window scaling option from them.
524 Default: 0
526 tcp_dma_copybreak - INTEGER
527 Lower limit, in bytes, of the size of socket reads that will be
528 offloaded to a DMA copy engine, if one is present in the system
529 and CONFIG_NET_DMA is enabled.
530 Default: 4096
532 tcp_thin_linear_timeouts - BOOLEAN
533 Enable dynamic triggering of linear timeouts for thin streams.
534 If set, a check is performed upon retransmission by timeout to
535 determine if the stream is thin (less than 4 packets in flight).
536 As long as the stream is found to be thin, up to 6 linear
537 timeouts may be performed before exponential backoff mode is
538 initiated. This improves retransmission latency for
539 non-aggressive thin streams, often found to be time-dependent.
540 For more information on thin streams, see
541 Documentation/networking/tcp-thin.txt
542 Default: 0
544 tcp_thin_dupack - BOOLEAN
545 Enable dynamic triggering of retransmissions after one dupACK
546 for thin streams. If set, a check is performed upon reception
547 of a dupACK to determine if the stream is thin (less than 4
548 packets in flight). As long as the stream is found to be thin,
549 data is retransmitted on the first received dupACK. This
550 improves retransmission latency for non-aggressive thin
551 streams, often found to be time-dependent.
552 For more information on thin streams, see
553 Documentation/networking/tcp-thin.txt
554 Default: 0
556 tcp_limit_output_bytes - INTEGER
557 Controls TCP Small Queue limit per tcp socket.
558 TCP bulk sender tends to increase packets in flight until it
559 gets losses notifications. With SNDBUF autotuning, this can
560 result in a large amount of packets queued in qdisc/device
561 on the local machine, hurting latency of other flows, for
562 typical pfifo_fast qdiscs.
563 tcp_limit_output_bytes limits the number of bytes on qdisc
564 or device to reduce artificial RTT/cwnd and reduce bufferbloat.
565 Note: For GSO/TSO enabled flows, we try to have at least two
566 packets in flight. Reducing tcp_limit_output_bytes might also
567 reduce the size of individual GSO packet (64KB being the max)
568 Default: 131072
570 tcp_challenge_ack_limit - INTEGER
571 Limits number of Challenge ACK sent per second, as recommended
572 in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
573 Default: 100
575 UDP variables:
577 udp_mem - vector of 3 INTEGERs: min, pressure, max
578 Number of pages allowed for queueing by all UDP sockets.
580 min: Below this number of pages UDP is not bothered about its
581 memory appetite. When amount of memory allocated by UDP exceeds
582 this number, UDP starts to moderate memory usage.
584 pressure: This value was introduced to follow format of tcp_mem.
586 max: Number of pages allowed for queueing by all UDP sockets.
588 Default is calculated at boot time from amount of available memory.
590 udp_rmem_min - INTEGER
591 Minimal size of receive buffer used by UDP sockets in moderation.
592 Each UDP socket is able to use the size for receiving data, even if
593 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
594 Default: 1 page
596 udp_wmem_min - INTEGER
597 Minimal size of send buffer used by UDP sockets in moderation.
598 Each UDP socket is able to use the size for sending data, even if
599 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
600 Default: 1 page
602 CIPSOv4 Variables:
604 cipso_cache_enable - BOOLEAN
605 If set, enable additions to and lookups from the CIPSO label mapping
606 cache. If unset, additions are ignored and lookups always result in a
607 miss. However, regardless of the setting the cache is still
608 invalidated when required when means you can safely toggle this on and
609 off and the cache will always be "safe".
610 Default: 1
612 cipso_cache_bucket_size - INTEGER
613 The CIPSO label cache consists of a fixed size hash table with each
614 hash bucket containing a number of cache entries. This variable limits
615 the number of entries in each hash bucket; the larger the value the
616 more CIPSO label mappings that can be cached. When the number of
617 entries in a given hash bucket reaches this limit adding new entries
618 causes the oldest entry in the bucket to be removed to make room.
619 Default: 10
621 cipso_rbm_optfmt - BOOLEAN
622 Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
623 the CIPSO draft specification (see Documentation/netlabel for details).
624 This means that when set the CIPSO tag will be padded with empty
625 categories in order to make the packet data 32-bit aligned.
626 Default: 0
628 cipso_rbm_structvalid - BOOLEAN
629 If set, do a very strict check of the CIPSO option when
630 ip_options_compile() is called. If unset, relax the checks done during
631 ip_options_compile(). Either way is "safe" as errors are caught else
632 where in the CIPSO processing code but setting this to 0 (False) should
633 result in less work (i.e. it should be faster) but could cause problems
634 with other implementations that require strict checking.
635 Default: 0
637 IP Variables:
639 ip_local_port_range - 2 INTEGERS
640 Defines the local port range that is used by TCP and UDP to
641 choose the local port. The first number is the first, the
642 second the last local port number. The default values are
643 32768 and 61000 respectively.
645 ip_local_reserved_ports - list of comma separated ranges
646 Specify the ports which are reserved for known third-party
647 applications. These ports will not be used by automatic port
648 assignments (e.g. when calling connect() or bind() with port
649 number 0). Explicit port allocation behavior is unchanged.
651 The format used for both input and output is a comma separated
652 list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
653 10). Writing to the file will clear all previously reserved
654 ports and update the current list with the one given in the
655 input.
657 Note that ip_local_port_range and ip_local_reserved_ports
658 settings are independent and both are considered by the kernel
659 when determining which ports are available for automatic port
660 assignments.
662 You can reserve ports which are not in the current
663 ip_local_port_range, e.g.:
665 $ cat /proc/sys/net/ipv4/ip_local_port_range
666 32000 61000
667 $ cat /proc/sys/net/ipv4/ip_local_reserved_ports
668 8080,9148
670 although this is redundant. However such a setting is useful
671 if later the port range is changed to a value that will
672 include the reserved ports.
674 Default: Empty
676 ip_nonlocal_bind - BOOLEAN
677 If set, allows processes to bind() to non-local IP addresses,
678 which can be quite useful - but may break some applications.
679 Default: 0
681 ip_dynaddr - BOOLEAN
682 If set non-zero, enables support for dynamic addresses.
683 If set to a non-zero value larger than 1, a kernel log
684 message will be printed when dynamic address rewriting
685 occurs.
686 Default: 0
688 ip_early_demux - BOOLEAN
689 Optimize input packet processing down to one demux for
690 certain kinds of local sockets. Currently we only do this
691 for established TCP sockets.
693 It may add an additional cost for pure routing workloads that
694 reduces overall throughput, in such case you should disable it.
695 Default: 1
697 icmp_echo_ignore_all - BOOLEAN
698 If set non-zero, then the kernel will ignore all ICMP ECHO
699 requests sent to it.
700 Default: 0
702 icmp_echo_ignore_broadcasts - BOOLEAN
703 If set non-zero, then the kernel will ignore all ICMP ECHO and
704 TIMESTAMP requests sent to it via broadcast/multicast.
705 Default: 1
707 icmp_ratelimit - INTEGER
708 Limit the maximal rates for sending ICMP packets whose type matches
709 icmp_ratemask (see below) to specific targets.
710 0 to disable any limiting,
711 otherwise the minimal space between responses in milliseconds.
712 Default: 1000
714 icmp_ratemask - INTEGER
715 Mask made of ICMP types for which rates are being limited.
716 Significant bits: IHGFEDCBA9876543210
717 Default mask: 0000001100000011000 (6168)
719 Bit definitions (see include/linux/icmp.h):
720 0 Echo Reply
721 3 Destination Unreachable *
722 4 Source Quench *
723 5 Redirect
724 8 Echo Request
725 B Time Exceeded *
726 C Parameter Problem *
727 D Timestamp Request
728 E Timestamp Reply
729 F Info Request
730 G Info Reply
731 H Address Mask Request
732 I Address Mask Reply
734 * These are rate limited by default (see default mask above)
736 icmp_ignore_bogus_error_responses - BOOLEAN
737 Some routers violate RFC1122 by sending bogus responses to broadcast
738 frames. Such violations are normally logged via a kernel warning.
739 If this is set to TRUE, the kernel will not give such warnings, which
740 will avoid log file clutter.
741 Default: 1
743 icmp_errors_use_inbound_ifaddr - BOOLEAN
745 If zero, icmp error messages are sent with the primary address of
746 the exiting interface.
748 If non-zero, the message will be sent with the primary address of
749 the interface that received the packet that caused the icmp error.
750 This is the behaviour network many administrators will expect from
751 a router. And it can make debugging complicated network layouts
752 much easier.
754 Note that if no primary address exists for the interface selected,
755 then the primary address of the first non-loopback interface that
756 has one will be used regardless of this setting.
758 Default: 0
760 igmp_max_memberships - INTEGER
761 Change the maximum number of multicast groups we can subscribe to.
762 Default: 20
764 Theoretical maximum value is bounded by having to send a membership
765 report in a single datagram (i.e. the report can't span multiple
766 datagrams, or risk confusing the switch and leaving groups you don't
767 intend to).
769 The number of supported groups 'M' is bounded by the number of group
770 report entries you can fit into a single datagram of 65535 bytes.
772 M = 65536-sizeof (ip header)/(sizeof(Group record))
774 Group records are variable length, with a minimum of 12 bytes.
775 So net.ipv4.igmp_max_memberships should not be set higher than:
777 (65536-24) / 12 = 5459
779 The value 5459 assumes no IP header options, so in practice
780 this number may be lower.
782 conf/interface/* changes special settings per interface (where
783 "interface" is the name of your network interface)
785 conf/all/* is special, changes the settings for all interfaces
787 log_martians - BOOLEAN
788 Log packets with impossible addresses to kernel log.
789 log_martians for the interface will be enabled if at least one of
790 conf/{all,interface}/log_martians is set to TRUE,
791 it will be disabled otherwise
793 accept_redirects - BOOLEAN
794 Accept ICMP redirect messages.
795 accept_redirects for the interface will be enabled if:
796 - both conf/{all,interface}/accept_redirects are TRUE in the case
797 forwarding for the interface is enabled
798 or
799 - at least one of conf/{all,interface}/accept_redirects is TRUE in the
800 case forwarding for the interface is disabled
801 accept_redirects for the interface will be disabled otherwise
802 default TRUE (host)
803 FALSE (router)
805 forwarding - BOOLEAN
806 Enable IP forwarding on this interface.
808 mc_forwarding - BOOLEAN
809 Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
810 and a multicast routing daemon is required.
811 conf/all/mc_forwarding must also be set to TRUE to enable multicast
812 routing for the interface
814 medium_id - INTEGER
815 Integer value used to differentiate the devices by the medium they
816 are attached to. Two devices can have different id values when
817 the broadcast packets are received only on one of them.
818 The default value 0 means that the device is the only interface
819 to its medium, value of -1 means that medium is not known.
821 Currently, it is used to change the proxy_arp behavior:
822 the proxy_arp feature is enabled for packets forwarded between
823 two devices attached to different media.
825 proxy_arp - BOOLEAN
826 Do proxy arp.
827 proxy_arp for the interface will be enabled if at least one of
828 conf/{all,interface}/proxy_arp is set to TRUE,
829 it will be disabled otherwise
831 proxy_arp_pvlan - BOOLEAN
832 Private VLAN proxy arp.
833 Basically allow proxy arp replies back to the same interface
834 (from which the ARP request/solicitation was received).
836 This is done to support (ethernet) switch features, like RFC
837 3069, where the individual ports are NOT allowed to
838 communicate with each other, but they are allowed to talk to
839 the upstream router. As described in RFC 3069, it is possible
840 to allow these hosts to communicate through the upstream
841 router by proxy_arp'ing. Don't need to be used together with
842 proxy_arp.
844 This technology is known by different names:
845 In RFC 3069 it is called VLAN Aggregation.
846 Cisco and Allied Telesyn call it Private VLAN.
847 Hewlett-Packard call it Source-Port filtering or port-isolation.
848 Ericsson call it MAC-Forced Forwarding (RFC Draft).
850 shared_media - BOOLEAN
851 Send(router) or accept(host) RFC1620 shared media redirects.
852 Overrides ip_secure_redirects.
853 shared_media for the interface will be enabled if at least one of
854 conf/{all,interface}/shared_media is set to TRUE,
855 it will be disabled otherwise
856 default TRUE
858 secure_redirects - BOOLEAN
859 Accept ICMP redirect messages only for gateways,
860 listed in default gateway list.
861 secure_redirects for the interface will be enabled if at least one of
862 conf/{all,interface}/secure_redirects is set to TRUE,
863 it will be disabled otherwise
864 default TRUE
866 send_redirects - BOOLEAN
867 Send redirects, if router.
868 send_redirects for the interface will be enabled if at least one of
869 conf/{all,interface}/send_redirects is set to TRUE,
870 it will be disabled otherwise
871 Default: TRUE
873 bootp_relay - BOOLEAN
874 Accept packets with source address 0.b.c.d destined
875 not to this host as local ones. It is supposed, that
876 BOOTP relay daemon will catch and forward such packets.
877 conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
878 for the interface
879 default FALSE
880 Not Implemented Yet.
882 accept_source_route - BOOLEAN
883 Accept packets with SRR option.
884 conf/all/accept_source_route must also be set to TRUE to accept packets
885 with SRR option on the interface
886 default TRUE (router)
887 FALSE (host)
889 accept_local - BOOLEAN
890 Accept packets with local source addresses. In combination
891 with suitable routing, this can be used to direct packets
892 between two local interfaces over the wire and have them
893 accepted properly.
895 rp_filter must be set to a non-zero value in order for
896 accept_local to have an effect.
898 default FALSE
900 route_localnet - BOOLEAN
901 Do not consider loopback addresses as martian source or destination
902 while routing. This enables the use of 127/8 for local routing purposes.
903 default FALSE
905 rp_filter - INTEGER
906 0 - No source validation.
907 1 - Strict mode as defined in RFC3704 Strict Reverse Path
908 Each incoming packet is tested against the FIB and if the interface
909 is not the best reverse path the packet check will fail.
910 By default failed packets are discarded.
911 2 - Loose mode as defined in RFC3704 Loose Reverse Path
912 Each incoming packet's source address is also tested against the FIB
913 and if the source address is not reachable via any interface
914 the packet check will fail.
916 Current recommended practice in RFC3704 is to enable strict mode
917 to prevent IP spoofing from DDos attacks. If using asymmetric routing
918 or other complicated routing, then loose mode is recommended.
920 The max value from conf/{all,interface}/rp_filter is used
921 when doing source validation on the {interface}.
923 Default value is 0. Note that some distributions enable it
924 in startup scripts.
926 arp_filter - BOOLEAN
927 1 - Allows you to have multiple network interfaces on the same
928 subnet, and have the ARPs for each interface be answered
929 based on whether or not the kernel would route a packet from
930 the ARP'd IP out that interface (therefore you must use source
931 based routing for this to work). In other words it allows control
932 of which cards (usually 1) will respond to an arp request.
934 0 - (default) The kernel can respond to arp requests with addresses
935 from other interfaces. This may seem wrong but it usually makes
936 sense, because it increases the chance of successful communication.
937 IP addresses are owned by the complete host on Linux, not by
938 particular interfaces. Only for more complex setups like load-
939 balancing, does this behaviour cause problems.
941 arp_filter for the interface will be enabled if at least one of
942 conf/{all,interface}/arp_filter is set to TRUE,
943 it will be disabled otherwise
945 arp_announce - INTEGER
946 Define different restriction levels for announcing the local
947 source IP address from IP packets in ARP requests sent on
948 interface:
949 0 - (default) Use any local address, configured on any interface
950 1 - Try to avoid local addresses that are not in the target's
951 subnet for this interface. This mode is useful when target
952 hosts reachable via this interface require the source IP
953 address in ARP requests to be part of their logical network
954 configured on the receiving interface. When we generate the
955 request we will check all our subnets that include the
956 target IP and will preserve the source address if it is from
957 such subnet. If there is no such subnet we select source
958 address according to the rules for level 2.
959 2 - Always use the best local address for this target.
960 In this mode we ignore the source address in the IP packet
961 and try to select local address that we prefer for talks with
962 the target host. Such local address is selected by looking
963 for primary IP addresses on all our subnets on the outgoing
964 interface that include the target IP address. If no suitable
965 local address is found we select the first local address
966 we have on the outgoing interface or on all other interfaces,
967 with the hope we will receive reply for our request and
968 even sometimes no matter the source IP address we announce.
970 The max value from conf/{all,interface}/arp_announce is used.
972 Increasing the restriction level gives more chance for
973 receiving answer from the resolved target while decreasing
974 the level announces more valid sender's information.
976 arp_ignore - INTEGER
977 Define different modes for sending replies in response to
978 received ARP requests that resolve local target IP addresses:
979 0 - (default): reply for any local target IP address, configured
980 on any interface
981 1 - reply only if the target IP address is local address
982 configured on the incoming interface
983 2 - reply only if the target IP address is local address
984 configured on the incoming interface and both with the
985 sender's IP address are part from same subnet on this interface
986 3 - do not reply for local addresses configured with scope host,
987 only resolutions for global and link addresses are replied
988 4-7 - reserved
989 8 - do not reply for all local addresses
991 The max value from conf/{all,interface}/arp_ignore is used
992 when ARP request is received on the {interface}
994 arp_notify - BOOLEAN
995 Define mode for notification of address and device changes.
996 0 - (default): do nothing
997 1 - Generate gratuitous arp requests when device is brought up
998 or hardware address changes.
1000 arp_accept - BOOLEAN
1001 Define behavior for gratuitous ARP frames who's IP is not
1002 already present in the ARP table:
1003 0 - don't create new entries in the ARP table
1004 1 - create new entries in the ARP table
1006 Both replies and requests type gratuitous arp will trigger the
1007 ARP table to be updated, if this setting is on.
1009 If the ARP table already contains the IP address of the
1010 gratuitous arp frame, the arp table will be updated regardless
1011 if this setting is on or off.
1014 app_solicit - INTEGER
1015 The maximum number of probes to send to the user space ARP daemon
1016 via netlink before dropping back to multicast probes (see
1017 mcast_solicit). Defaults to 0.
1019 disable_policy - BOOLEAN
1020 Disable IPSEC policy (SPD) for this interface
1022 disable_xfrm - BOOLEAN
1023 Disable IPSEC encryption on this interface, whatever the policy
1027 tag - INTEGER
1028 Allows you to write a number, which can be used as required.
1029 Default value is 0.
1031 Alexey Kuznetsov.
1032 kuznet@ms2.inr.ac.ru
1034 Updated by:
1035 Andi Kleen
1036 ak@muc.de
1037 Nicolas Delon
1038 delon.nicolas@wanadoo.fr
1043 /proc/sys/net/ipv6/* Variables:
1045 IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
1046 apply to IPv6 [XXX?].
1048 bindv6only - BOOLEAN
1049 Default value for IPV6_V6ONLY socket option,
1050 which restricts use of the IPv6 socket to IPv6 communication
1051 only.
1052 TRUE: disable IPv4-mapped address feature
1053 FALSE: enable IPv4-mapped address feature
1055 Default: FALSE (as specified in RFC3493)
1057 IPv6 Fragmentation:
1059 ip6frag_high_thresh - INTEGER
1060 Maximum memory used to reassemble IPv6 fragments. When
1061 ip6frag_high_thresh bytes of memory is allocated for this purpose,
1062 the fragment handler will toss packets until ip6frag_low_thresh
1063 is reached.
1065 ip6frag_low_thresh - INTEGER
1066 See ip6frag_high_thresh
1068 ip6frag_time - INTEGER
1069 Time in seconds to keep an IPv6 fragment in memory.
1071 ip6frag_secret_interval - INTEGER
1072 Regeneration interval (in seconds) of the hash secret (or lifetime
1073 for the hash secret) for IPv6 fragments.
1074 Default: 600
1076 conf/default/*:
1077 Change the interface-specific default settings.
1080 conf/all/*:
1081 Change all the interface-specific settings.
1083 [XXX: Other special features than forwarding?]
1085 conf/all/forwarding - BOOLEAN
1086 Enable global IPv6 forwarding between all interfaces.
1088 IPv4 and IPv6 work differently here; e.g. netfilter must be used
1089 to control which interfaces may forward packets and which not.
1091 This also sets all interfaces' Host/Router setting
1092 'forwarding' to the specified value. See below for details.
1094 This referred to as global forwarding.
1096 proxy_ndp - BOOLEAN
1097 Do proxy ndp.
1099 conf/interface/*:
1100 Change special settings per interface.
1102 The functional behaviour for certain settings is different
1103 depending on whether local forwarding is enabled or not.
1105 accept_ra - INTEGER
1106 Accept Router Advertisements; autoconfigure using them.
1108 It also determines whether or not to transmit Router
1109 Solicitations. If and only if the functional setting is to
1110 accept Router Advertisements, Router Solicitations will be
1111 transmitted.
1113 Possible values are:
1114 0 Do not accept Router Advertisements.
1115 1 Accept Router Advertisements if forwarding is disabled.
1116 2 Overrule forwarding behaviour. Accept Router Advertisements
1117 even if forwarding is enabled.
1119 Functional default: enabled if local forwarding is disabled.
1120 disabled if local forwarding is enabled.
1122 accept_ra_defrtr - BOOLEAN
1123 Learn default router in Router Advertisement.
1125 Functional default: enabled if accept_ra is enabled.
1126 disabled if accept_ra is disabled.
1128 accept_ra_pinfo - BOOLEAN
1129 Learn Prefix Information in Router Advertisement.
1131 Functional default: enabled if accept_ra is enabled.
1132 disabled if accept_ra is disabled.
1134 accept_ra_rt_info_max_plen - INTEGER
1135 Maximum prefix length of Route Information in RA.
1137 Route Information w/ prefix larger than or equal to this
1138 variable shall be ignored.
1140 Functional default: 0 if accept_ra_rtr_pref is enabled.
1141 -1 if accept_ra_rtr_pref is disabled.
1143 accept_ra_rtr_pref - BOOLEAN
1144 Accept Router Preference in RA.
1146 Functional default: enabled if accept_ra is enabled.
1147 disabled if accept_ra is disabled.
1149 accept_redirects - BOOLEAN
1150 Accept Redirects.
1152 Functional default: enabled if local forwarding is disabled.
1153 disabled if local forwarding is enabled.
1155 accept_source_route - INTEGER
1156 Accept source routing (routing extension header).
1158 >= 0: Accept only routing header type 2.
1159 < 0: Do not accept routing header.
1161 Default: 0
1163 autoconf - BOOLEAN
1164 Autoconfigure addresses using Prefix Information in Router
1165 Advertisements.
1167 Functional default: enabled if accept_ra_pinfo is enabled.
1168 disabled if accept_ra_pinfo is disabled.
1170 dad_transmits - INTEGER
1171 The amount of Duplicate Address Detection probes to send.
1172 Default: 1
1174 forwarding - INTEGER
1175 Configure interface-specific Host/Router behaviour.
1177 Note: It is recommended to have the same setting on all
1178 interfaces; mixed router/host scenarios are rather uncommon.
1180 Possible values are:
1181 0 Forwarding disabled
1182 1 Forwarding enabled
1184 FALSE (0):
1186 By default, Host behaviour is assumed. This means:
1188 1. IsRouter flag is not set in Neighbour Advertisements.
1189 2. If accept_ra is TRUE (default), transmit Router
1190 Solicitations.
1191 3. If accept_ra is TRUE (default), accept Router
1192 Advertisements (and do autoconfiguration).
1193 4. If accept_redirects is TRUE (default), accept Redirects.
1195 TRUE (1):
1197 If local forwarding is enabled, Router behaviour is assumed.
1198 This means exactly the reverse from the above:
1200 1. IsRouter flag is set in Neighbour Advertisements.
1201 2. Router Solicitations are not sent unless accept_ra is 2.
1202 3. Router Advertisements are ignored unless accept_ra is 2.
1203 4. Redirects are ignored.
1205 Default: 0 (disabled) if global forwarding is disabled (default),
1206 otherwise 1 (enabled).
1208 hop_limit - INTEGER
1209 Default Hop Limit to set.
1210 Default: 64
1212 mtu - INTEGER
1213 Default Maximum Transfer Unit
1214 Default: 1280 (IPv6 required minimum)
1216 router_probe_interval - INTEGER
1217 Minimum interval (in seconds) between Router Probing described
1218 in RFC4191.
1220 Default: 60
1222 router_solicitation_delay - INTEGER
1223 Number of seconds to wait after interface is brought up
1224 before sending Router Solicitations.
1225 Default: 1
1227 router_solicitation_interval - INTEGER
1228 Number of seconds to wait between Router Solicitations.
1229 Default: 4
1231 router_solicitations - INTEGER
1232 Number of Router Solicitations to send until assuming no
1233 routers are present.
1234 Default: 3
1236 use_tempaddr - INTEGER
1237 Preference for Privacy Extensions (RFC3041).
1238 <= 0 : disable Privacy Extensions
1239 == 1 : enable Privacy Extensions, but prefer public
1240 addresses over temporary addresses.
1241 > 1 : enable Privacy Extensions and prefer temporary
1242 addresses over public addresses.
1243 Default: 0 (for most devices)
1244 -1 (for point-to-point devices and loopback devices)
1246 temp_valid_lft - INTEGER
1247 valid lifetime (in seconds) for temporary addresses.
1248 Default: 604800 (7 days)
1250 temp_prefered_lft - INTEGER
1251 Preferred lifetime (in seconds) for temporary addresses.
1252 Default: 86400 (1 day)
1254 max_desync_factor - INTEGER
1255 Maximum value for DESYNC_FACTOR, which is a random value
1256 that ensures that clients don't synchronize with each
1257 other and generate new addresses at exactly the same time.
1258 value is in seconds.
1259 Default: 600
1261 regen_max_retry - INTEGER
1262 Number of attempts before give up attempting to generate
1263 valid temporary addresses.
1264 Default: 5
1266 max_addresses - INTEGER
1267 Maximum number of autoconfigured addresses per interface. Setting
1268 to zero disables the limitation. It is not recommended to set this
1269 value too large (or to zero) because it would be an easy way to
1270 crash the kernel by allowing too many addresses to be created.
1271 Default: 16
1273 disable_ipv6 - BOOLEAN
1274 Disable IPv6 operation. If accept_dad is set to 2, this value
1275 will be dynamically set to TRUE if DAD fails for the link-local
1276 address.
1277 Default: FALSE (enable IPv6 operation)
1279 When this value is changed from 1 to 0 (IPv6 is being enabled),
1280 it will dynamically create a link-local address on the given
1281 interface and start Duplicate Address Detection, if necessary.
1283 When this value is changed from 0 to 1 (IPv6 is being disabled),
1284 it will dynamically delete all address on the given interface.
1286 accept_dad - INTEGER
1287 Whether to accept DAD (Duplicate Address Detection).
1288 0: Disable DAD
1289 1: Enable DAD (default)
1290 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
1291 link-local address has been found.
1293 force_tllao - BOOLEAN
1294 Enable sending the target link-layer address option even when
1295 responding to a unicast neighbor solicitation.
1296 Default: FALSE
1298 Quoting from RFC 2461, section 4.4, Target link-layer address:
1300 "The option MUST be included for multicast solicitations in order to
1301 avoid infinite Neighbor Solicitation "recursion" when the peer node
1302 does not have a cache entry to return a Neighbor Advertisements
1303 message. When responding to unicast solicitations, the option can be
1304 omitted since the sender of the solicitation has the correct link-
1305 layer address; otherwise it would not have be able to send the unicast
1306 solicitation in the first place. However, including the link-layer
1307 address in this case adds little overhead and eliminates a potential
1308 race condition where the sender deletes the cached link-layer address
1309 prior to receiving a response to a previous solicitation."
1311 ndisc_notify - BOOLEAN
1312 Define mode for notification of address and device changes.
1313 0 - (default): do nothing
1314 1 - Generate unsolicited neighbour advertisements when device is brought
1315 up or hardware address changes.
1317 icmp/*:
1318 ratelimit - INTEGER
1319 Limit the maximal rates for sending ICMPv6 packets.
1320 0 to disable any limiting,
1321 otherwise the minimal space between responses in milliseconds.
1322 Default: 1000
1325 IPv6 Update by:
1326 Pekka Savola <pekkas@netcore.fi>
1327 YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
1330 /proc/sys/net/bridge/* Variables:
1332 bridge-nf-call-arptables - BOOLEAN
1333 1 : pass bridged ARP traffic to arptables' FORWARD chain.
1334 0 : disable this.
1335 Default: 1
1337 bridge-nf-call-iptables - BOOLEAN
1338 1 : pass bridged IPv4 traffic to iptables' chains.
1339 0 : disable this.
1340 Default: 1
1342 bridge-nf-call-ip6tables - BOOLEAN
1343 1 : pass bridged IPv6 traffic to ip6tables' chains.
1344 0 : disable this.
1345 Default: 1
1347 bridge-nf-filter-vlan-tagged - BOOLEAN
1348 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
1349 0 : disable this.
1350 Default: 0
1352 bridge-nf-filter-pppoe-tagged - BOOLEAN
1353 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
1354 0 : disable this.
1355 Default: 0
1357 bridge-nf-pass-vlan-input-dev - BOOLEAN
1358 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
1359 interface on the bridge and set the netfilter input device to the vlan.
1360 This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT
1361 target work with vlan-on-top-of-bridge interfaces. When no matching
1362 vlan interface is found, or this switch is off, the input device is
1363 set to the bridge interface.
1364 0: disable bridge netfilter vlan interface lookup.
1365 Default: 0
1367 proc/sys/net/sctp/* Variables:
1369 addip_enable - BOOLEAN
1370 Enable or disable extension of Dynamic Address Reconfiguration
1371 (ADD-IP) functionality specified in RFC5061. This extension provides
1372 the ability to dynamically add and remove new addresses for the SCTP
1373 associations.
1375 1: Enable extension.
1377 0: Disable extension.
1379 Default: 0
1381 addip_noauth_enable - BOOLEAN
1382 Dynamic Address Reconfiguration (ADD-IP) requires the use of
1383 authentication to protect the operations of adding or removing new
1384 addresses. This requirement is mandated so that unauthorized hosts
1385 would not be able to hijack associations. However, older
1386 implementations may not have implemented this requirement while
1387 allowing the ADD-IP extension. For reasons of interoperability,
1388 we provide this variable to control the enforcement of the
1389 authentication requirement.
1391 1: Allow ADD-IP extension to be used without authentication. This
1392 should only be set in a closed environment for interoperability
1393 with older implementations.
1395 0: Enforce the authentication requirement
1397 Default: 0
1399 auth_enable - BOOLEAN
1400 Enable or disable Authenticated Chunks extension. This extension
1401 provides the ability to send and receive authenticated chunks and is
1402 required for secure operation of Dynamic Address Reconfiguration
1403 (ADD-IP) extension.
1405 1: Enable this extension.
1406 0: Disable this extension.
1408 Default: 0
1410 prsctp_enable - BOOLEAN
1411 Enable or disable the Partial Reliability extension (RFC3758) which
1412 is used to notify peers that a given DATA should no longer be expected.
1414 1: Enable extension
1415 0: Disable
1417 Default: 1
1419 max_burst - INTEGER
1420 The limit of the number of new packets that can be initially sent. It
1421 controls how bursty the generated traffic can be.
1423 Default: 4
1425 association_max_retrans - INTEGER
1426 Set the maximum number for retransmissions that an association can
1427 attempt deciding that the remote end is unreachable. If this value
1428 is exceeded, the association is terminated.
1430 Default: 10
1432 max_init_retransmits - INTEGER
1433 The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
1434 that an association will attempt before declaring the destination
1435 unreachable and terminating.
1437 Default: 8
1439 path_max_retrans - INTEGER
1440 The maximum number of retransmissions that will be attempted on a given
1441 path. Once this threshold is exceeded, the path is considered
1442 unreachable, and new traffic will use a different path when the
1443 association is multihomed.
1445 Default: 5
1447 pf_retrans - INTEGER
1448 The number of retransmissions that will be attempted on a given path
1449 before traffic is redirected to an alternate transport (should one
1450 exist). Note this is distinct from path_max_retrans, as a path that
1451 passes the pf_retrans threshold can still be used. Its only
1452 deprioritized when a transmission path is selected by the stack. This
1453 setting is primarily used to enable fast failover mechanisms without
1454 having to reduce path_max_retrans to a very low value. See:
1455 http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
1456 for details. Note also that a value of pf_retrans > path_max_retrans
1457 disables this feature
1459 Default: 0
1461 rto_initial - INTEGER
1462 The initial round trip timeout value in milliseconds that will be used
1463 in calculating round trip times. This is the initial time interval
1464 for retransmissions.
1466 Default: 3000
1468 rto_max - INTEGER
1469 The maximum value (in milliseconds) of the round trip timeout. This
1470 is the largest time interval that can elapse between retransmissions.
1472 Default: 60000
1474 rto_min - INTEGER
1475 The minimum value (in milliseconds) of the round trip timeout. This
1476 is the smallest time interval the can elapse between retransmissions.
1478 Default: 1000
1480 hb_interval - INTEGER
1481 The interval (in milliseconds) between HEARTBEAT chunks. These chunks
1482 are sent at the specified interval on idle paths to probe the state of
1483 a given path between 2 associations.
1485 Default: 30000
1487 sack_timeout - INTEGER
1488 The amount of time (in milliseconds) that the implementation will wait
1489 to send a SACK.
1491 Default: 200
1493 valid_cookie_life - INTEGER
1494 The default lifetime of the SCTP cookie (in milliseconds). The cookie
1495 is used during association establishment.
1497 Default: 60000
1499 cookie_preserve_enable - BOOLEAN
1500 Enable or disable the ability to extend the lifetime of the SCTP cookie
1501 that is used during the establishment phase of SCTP association
1503 1: Enable cookie lifetime extension.
1504 0: Disable
1506 Default: 1
1508 cookie_hmac_alg - STRING
1509 Select the hmac algorithm used when generating the cookie value sent by
1510 a listening sctp socket to a connecting client in the INIT-ACK chunk.
1511 Valid values are:
1512 * md5
1513 * sha1
1514 * none
1515 Ability to assign md5 or sha1 as the selected alg is predicated on the
1516 configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
1517 CONFIG_CRYPTO_SHA1).
1519 Default: Dependent on configuration. MD5 if available, else SHA1 if
1520 available, else none.
1522 rcvbuf_policy - INTEGER
1523 Determines if the receive buffer is attributed to the socket or to
1524 association. SCTP supports the capability to create multiple
1525 associations on a single socket. When using this capability, it is
1526 possible that a single stalled association that's buffering a lot
1527 of data may block other associations from delivering their data by
1528 consuming all of the receive buffer space. To work around this,
1529 the rcvbuf_policy could be set to attribute the receiver buffer space
1530 to each association instead of the socket. This prevents the described
1531 blocking.
1533 1: rcvbuf space is per association
1534 0: rcvbuf space is per socket
1536 Default: 0
1538 sndbuf_policy - INTEGER
1539 Similar to rcvbuf_policy above, this applies to send buffer space.
1541 1: Send buffer is tracked per association
1542 0: Send buffer is tracked per socket.
1544 Default: 0
1546 sctp_mem - vector of 3 INTEGERs: min, pressure, max
1547 Number of pages allowed for queueing by all SCTP sockets.
1549 min: Below this number of pages SCTP is not bothered about its
1550 memory appetite. When amount of memory allocated by SCTP exceeds
1551 this number, SCTP starts to moderate memory usage.
1553 pressure: This value was introduced to follow format of tcp_mem.
1555 max: Number of pages allowed for queueing by all SCTP sockets.
1557 Default is calculated at boot time from amount of available memory.
1559 sctp_rmem - vector of 3 INTEGERs: min, default, max
1560 Only the first value ("min") is used, "default" and "max" are
1561 ignored.
1563 min: Minimal size of receive buffer used by SCTP socket.
1564 It is guaranteed to each SCTP socket (but not association) even
1565 under moderate memory pressure.
1567 Default: 1 page
1569 sctp_wmem - vector of 3 INTEGERs: min, default, max
1570 Currently this tunable has no effect.
1572 addr_scope_policy - INTEGER
1573 Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
1575 0 - Disable IPv4 address scoping
1576 1 - Enable IPv4 address scoping
1577 2 - Follow draft but allow IPv4 private addresses
1578 3 - Follow draft but allow IPv4 link local addresses
1580 Default: 1
1583 /proc/sys/net/core/*
1584 Please see: Documentation/sysctl/net.txt for descriptions of these entries.
1587 /proc/sys/net/unix/*
1588 max_dgram_qlen - INTEGER
1589 The maximum length of dgram socket receive queue
1591 Default: 10
1594 UNDOCUMENTED:
1596 /proc/sys/net/irda/*
1597 fast_poll_increase FIXME
1598 warn_noreply_time FIXME
1599 discovery_slots FIXME
1600 slot_timeout FIXME
1601 max_baud_rate FIXME
1602 discovery_timeout FIXME
1603 lap_keepalive_time FIXME
1604 max_noreply_time FIXME
1605 max_tx_data_size FIXME
1606 max_tx_window FIXME
1607 min_tx_turn_time FIXME