1 /proc/sys/net/ipv4/* Variables:
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
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 - 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.
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.
33 default 552 - minimum discovered Path MTU
35 route/max_size - INTEGER
36 Maximum number of routes allowed in the kernel. Increase
37 this when using large numbers of interfaces and/or routes.
39 neigh/default/gc_thresh1 - INTEGER
40 Minimum number of entries to keep. Garbage collector will not
41 purge entries if there are fewer than this number.
44 neigh/default/gc_thresh3 - INTEGER
45 Maximum number of neighbor entries allowed. Increase this
46 when using large numbers of interfaces and when communicating
47 with large numbers of directly-connected peers.
50 neigh/default/unres_qlen_bytes - INTEGER
51 The maximum number of bytes which may be used by packets
52 queued for each unresolved address by other network layers.
54 Setting negative value is meaningless and will return error.
55 Default: 65536 Bytes(64KB)
57 neigh/default/unres_qlen - INTEGER
58 The maximum number of packets which may be queued for each
59 unresolved address by other network layers.
60 (deprecated in linux 3.3) : use unres_qlen_bytes instead.
61 Prior to linux 3.3, the default value is 3 which may cause
62 unexpected packet loss. The current default value is calculated
63 according to default value of unres_qlen_bytes and true size of
68 Time, in seconds, that cached PMTU information is kept.
71 The advertised MSS depends on the first hop route MTU, but will
72 never be lower than this setting.
76 ipfrag_high_thresh - INTEGER
77 Maximum memory used to reassemble IP fragments. When
78 ipfrag_high_thresh bytes of memory is allocated for this purpose,
79 the fragment handler will toss packets until ipfrag_low_thresh
82 ipfrag_low_thresh - INTEGER
83 See ipfrag_high_thresh
86 Time in seconds to keep an IP fragment in memory.
88 ipfrag_secret_interval - INTEGER
89 Regeneration interval (in seconds) of the hash secret (or lifetime
90 for the hash secret) for IP fragments.
93 ipfrag_max_dist - INTEGER
94 ipfrag_max_dist is a non-negative integer value which defines the
95 maximum "disorder" which is allowed among fragments which share a
96 common IP source address. Note that reordering of packets is
97 not unusual, but if a large number of fragments arrive from a source
98 IP address while a particular fragment queue remains incomplete, it
99 probably indicates that one or more fragments belonging to that queue
100 have been lost. When ipfrag_max_dist is positive, an additional check
101 is done on fragments before they are added to a reassembly queue - if
102 ipfrag_max_dist (or more) fragments have arrived from a particular IP
103 address between additions to any IP fragment queue using that source
104 address, it's presumed that one or more fragments in the queue are
105 lost. The existing fragment queue will be dropped, and a new one
106 started. An ipfrag_max_dist value of zero disables this check.
108 Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
109 result in unnecessarily dropping fragment queues when normal
110 reordering of packets occurs, which could lead to poor application
111 performance. Using a very large value, e.g. 50000, increases the
112 likelihood of incorrectly reassembling IP fragments that originate
113 from different IP datagrams, which could result in data corruption.
118 inet_peer_threshold - INTEGER
119 The approximate size of the storage. Starting from this threshold
120 entries will be thrown aggressively. This threshold also determines
121 entries' time-to-live and time intervals between garbage collection
122 passes. More entries, less time-to-live, less GC interval.
124 inet_peer_minttl - INTEGER
125 Minimum time-to-live of entries. Should be enough to cover fragment
126 time-to-live on the reassembling side. This minimum time-to-live is
127 guaranteed if the pool size is less than inet_peer_threshold.
130 inet_peer_maxttl - INTEGER
131 Maximum time-to-live of entries. Unused entries will expire after
132 this period of time if there is no memory pressure on the pool (i.e.
133 when the number of entries in the pool is very small).
139 Limit of socket listen() backlog, known in userspace as SOMAXCONN.
140 Defaults to 128. See also tcp_max_syn_backlog for additional tuning
143 tcp_abort_on_overflow - BOOLEAN
144 If listening service is too slow to accept new connections,
145 reset them. Default state is FALSE. It means that if overflow
146 occurred due to a burst, connection will recover. Enable this
147 option _only_ if you are really sure that listening daemon
148 cannot be tuned to accept connections faster. Enabling this
149 option can harm clients of your server.
151 tcp_adv_win_scale - INTEGER
152 Count buffering overhead as bytes/2^tcp_adv_win_scale
153 (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
155 Possible values are [-31, 31], inclusive.
158 tcp_allowed_congestion_control - STRING
159 Show/set the congestion control choices available to non-privileged
160 processes. The list is a subset of those listed in
161 tcp_available_congestion_control.
162 Default is "reno" and the default setting (tcp_congestion_control).
164 tcp_app_win - INTEGER
165 Reserve max(window/2^tcp_app_win, mss) of window for application
166 buffer. Value 0 is special, it means that nothing is reserved.
169 tcp_autocorking - BOOLEAN
170 Enable TCP auto corking :
171 When applications do consecutive small write()/sendmsg() system calls,
172 we try to coalesce these small writes as much as possible, to lower
173 total amount of sent packets. This is done if at least one prior
174 packet for the flow is waiting in Qdisc queues or device transmit
175 queue. Applications can still use TCP_CORK for optimal behavior
176 when they know how/when to uncork their sockets.
179 tcp_available_congestion_control - STRING
180 Shows the available congestion control choices that are registered.
181 More congestion control algorithms may be available as modules,
184 tcp_base_mss - INTEGER
185 The initial value of search_low to be used by the packetization layer
186 Path MTU discovery (MTU probing). If MTU probing is enabled,
187 this is the initial MSS used by the connection.
189 tcp_congestion_control - STRING
190 Set the congestion control algorithm to be used for new
191 connections. The algorithm "reno" is always available, but
192 additional choices may be available based on kernel configuration.
193 Default is set as part of kernel configuration.
194 For passive connections, the listener congestion control choice
196 [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
199 Allows TCP to send "duplicate" SACKs.
201 tcp_early_retrans - INTEGER
202 Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold
203 for triggering fast retransmit when the amount of outstanding data is
204 small and when no previously unsent data can be transmitted (such
205 that limited transmit could be used). Also controls the use of
206 Tail loss probe (TLP) that converts RTOs occurring due to tail
207 losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01).
211 2 enables ER but delays fast recovery and fast retransmit
212 by a fourth of RTT. This mitigates connection falsely
213 recovers when network has a small degree of reordering
214 (less than 3 packets).
215 3 enables delayed ER and TLP.
220 Control use of Explicit Congestion Notification (ECN) by TCP.
221 ECN is used only when both ends of the TCP connection indicate
222 support for it. This feature is useful in avoiding losses due
223 to congestion by allowing supporting routers to signal
224 congestion before having to drop packets.
226 0 Disable ECN. Neither initiate nor accept ECN.
227 1 Enable ECN when requested by incoming connections and
228 also request ECN on outgoing connection attempts.
229 2 Enable ECN when requested by incoming connections
230 but do not request ECN on outgoing connections.
234 Enable FACK congestion avoidance and fast retransmission.
235 The value is not used, if tcp_sack is not enabled.
237 tcp_fin_timeout - INTEGER
238 The length of time an orphaned (no longer referenced by any
239 application) connection will remain in the FIN_WAIT_2 state
240 before it is aborted at the local end. While a perfectly
241 valid "receive only" state for an un-orphaned connection, an
242 orphaned connection in FIN_WAIT_2 state could otherwise wait
243 forever for the remote to close its end of the connection.
248 Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
249 F-RTO is an enhanced recovery algorithm for TCP retransmission
250 timeouts. It is particularly beneficial in networks where the
251 RTT fluctuates (e.g., wireless). F-RTO is sender-side only
252 modification. It does not require any support from the peer.
254 By default it's enabled with a non-zero value. 0 disables F-RTO.
256 tcp_keepalive_time - INTEGER
257 How often TCP sends out keepalive messages when keepalive is enabled.
260 tcp_keepalive_probes - INTEGER
261 How many keepalive probes TCP sends out, until it decides that the
262 connection is broken. Default value: 9.
264 tcp_keepalive_intvl - INTEGER
265 How frequently the probes are send out. Multiplied by
266 tcp_keepalive_probes it is time to kill not responding connection,
267 after probes started. Default value: 75sec i.e. connection
268 will be aborted after ~11 minutes of retries.
270 tcp_low_latency - BOOLEAN
271 If set, the TCP stack makes decisions that prefer lower
272 latency as opposed to higher throughput. By default, this
273 option is not set meaning that higher throughput is preferred.
274 An example of an application where this default should be
275 changed would be a Beowulf compute cluster.
278 tcp_max_orphans - INTEGER
279 Maximal number of TCP sockets not attached to any user file handle,
280 held by system. If this number is exceeded orphaned connections are
281 reset immediately and warning is printed. This limit exists
282 only to prevent simple DoS attacks, you _must_ not rely on this
283 or lower the limit artificially, but rather increase it
284 (probably, after increasing installed memory),
285 if network conditions require more than default value,
286 and tune network services to linger and kill such states
287 more aggressively. Let me to remind again: each orphan eats
288 up to ~64K of unswappable memory.
290 tcp_max_syn_backlog - INTEGER
291 Maximal number of remembered connection requests, which have not
292 received an acknowledgment from connecting client.
293 The minimal value is 128 for low memory machines, and it will
294 increase in proportion to the memory of machine.
295 If server suffers from overload, try increasing this number.
297 tcp_max_tw_buckets - INTEGER
298 Maximal number of timewait sockets held by system simultaneously.
299 If this number is exceeded time-wait socket is immediately destroyed
300 and warning is printed. This limit exists only to prevent
301 simple DoS attacks, you _must_ not lower the limit artificially,
302 but rather increase it (probably, after increasing installed memory),
303 if network conditions require more than default value.
305 tcp_mem - vector of 3 INTEGERs: min, pressure, max
306 min: below this number of pages TCP is not bothered about its
309 pressure: when amount of memory allocated by TCP exceeds this number
310 of pages, TCP moderates its memory consumption and enters memory
311 pressure mode, which is exited when memory consumption falls
314 max: number of pages allowed for queueing by all TCP sockets.
316 Defaults are calculated at boot time from amount of available
319 tcp_moderate_rcvbuf - BOOLEAN
320 If set, TCP performs receive buffer auto-tuning, attempting to
321 automatically size the buffer (no greater than tcp_rmem[2]) to
322 match the size required by the path for full throughput. Enabled by
325 tcp_mtu_probing - INTEGER
326 Controls TCP Packetization-Layer Path MTU Discovery. Takes three
329 1 - Disabled by default, enabled when an ICMP black hole detected
330 2 - Always enabled, use initial MSS of tcp_base_mss.
332 tcp_no_metrics_save - BOOLEAN
333 By default, TCP saves various connection metrics in the route cache
334 when the connection closes, so that connections established in the
335 near future can use these to set initial conditions. Usually, this
336 increases overall performance, but may sometimes cause performance
337 degradation. If set, TCP will not cache metrics on closing
340 tcp_orphan_retries - INTEGER
341 This value influences the timeout of a locally closed TCP connection,
342 when RTO retransmissions remain unacknowledged.
343 See tcp_retries2 for more details.
345 The default value is 8.
346 If your machine is a loaded WEB server,
347 you should think about lowering this value, such sockets
348 may consume significant resources. Cf. tcp_max_orphans.
350 tcp_reordering - INTEGER
351 Maximal reordering of packets in a TCP stream.
354 tcp_retrans_collapse - BOOLEAN
355 Bug-to-bug compatibility with some broken printers.
356 On retransmit try to send bigger packets to work around bugs in
359 tcp_retries1 - INTEGER
360 This value influences the time, after which TCP decides, that
361 something is wrong due to unacknowledged RTO retransmissions,
362 and reports this suspicion to the network layer.
363 See tcp_retries2 for more details.
365 RFC 1122 recommends at least 3 retransmissions, which is the
368 tcp_retries2 - INTEGER
369 This value influences the timeout of an alive TCP connection,
370 when RTO retransmissions remain unacknowledged.
371 Given a value of N, a hypothetical TCP connection following
372 exponential backoff with an initial RTO of TCP_RTO_MIN would
373 retransmit N times before killing the connection at the (N+1)th RTO.
375 The default value of 15 yields a hypothetical timeout of 924.6
376 seconds and is a lower bound for the effective timeout.
377 TCP will effectively time out at the first RTO which exceeds the
378 hypothetical timeout.
380 RFC 1122 recommends at least 100 seconds for the timeout,
381 which corresponds to a value of at least 8.
383 tcp_rfc1337 - BOOLEAN
384 If set, the TCP stack behaves conforming to RFC1337. If unset,
385 we are not conforming to RFC, but prevent TCP TIME_WAIT
389 tcp_rmem - vector of 3 INTEGERs: min, default, max
390 min: Minimal size of receive buffer used by TCP sockets.
391 It is guaranteed to each TCP socket, even under moderate memory
395 default: initial size of receive buffer used by TCP sockets.
396 This value overrides net.core.rmem_default used by other protocols.
397 Default: 87380 bytes. This value results in window of 65535 with
398 default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
399 less for default tcp_app_win. See below about these variables.
401 max: maximal size of receive buffer allowed for automatically
402 selected receiver buffers for TCP socket. This value does not override
403 net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
404 automatic tuning of that socket's receive buffer size, in which
405 case this value is ignored.
406 Default: between 87380B and 6MB, depending on RAM size.
409 Enable select acknowledgments (SACKS).
411 tcp_slow_start_after_idle - BOOLEAN
412 If set, provide RFC2861 behavior and time out the congestion
413 window after an idle period. An idle period is defined at
414 the current RTO. If unset, the congestion window will not
415 be timed out after an idle period.
419 Use the Host requirements interpretation of the TCP urgent pointer field.
420 Most hosts use the older BSD interpretation, so if you turn this on
421 Linux might not communicate correctly with them.
424 tcp_synack_retries - INTEGER
425 Number of times SYNACKs for a passive TCP connection attempt will
426 be retransmitted. Should not be higher than 255. Default value
427 is 5, which corresponds to 31seconds till the last retransmission
428 with the current initial RTO of 1second. With this the final timeout
429 for a passive TCP connection will happen after 63seconds.
431 tcp_syncookies - BOOLEAN
432 Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
433 Send out syncookies when the syn backlog queue of a socket
434 overflows. This is to prevent against the common 'SYN flood attack'
437 Note, that syncookies is fallback facility.
438 It MUST NOT be used to help highly loaded servers to stand
439 against legal connection rate. If you see SYN flood warnings
440 in your logs, but investigation shows that they occur
441 because of overload with legal connections, you should tune
442 another parameters until this warning disappear.
443 See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
445 syncookies seriously violate TCP protocol, do not allow
446 to use TCP extensions, can result in serious degradation
447 of some services (f.e. SMTP relaying), visible not by you,
448 but your clients and relays, contacting you. While you see
449 SYN flood warnings in logs not being really flooded, your server
450 is seriously misconfigured.
452 If you want to test which effects syncookies have to your
453 network connections you can set this knob to 2 to enable
454 unconditionally generation of syncookies.
456 tcp_fastopen - INTEGER
457 Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
458 in the opening SYN packet. To use this feature, the client application
459 must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than
460 connect() to perform a TCP handshake automatically.
462 The values (bitmap) are
463 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN.
464 2: Enables TCP Fast Open on the server side, i.e., allowing data in
465 a SYN packet to be accepted and passed to the application before
466 3-way hand shake finishes.
467 4: Send data in the opening SYN regardless of cookie availability and
468 without a cookie option.
469 0x100: Accept SYN data w/o validating the cookie.
470 0x200: Accept data-in-SYN w/o any cookie option present.
471 0x400/0x800: Enable Fast Open on all listeners regardless of the
472 TCP_FASTOPEN socket option. The two different flags designate two
473 different ways of setting max_qlen without the TCP_FASTOPEN socket
478 Note that the client & server side Fast Open flags (1 and 2
479 respectively) must be also enabled before the rest of flags can take
482 See include/net/tcp.h and the code for more details.
484 tcp_syn_retries - INTEGER
485 Number of times initial SYNs for an active TCP connection attempt
486 will be retransmitted. Should not be higher than 255. Default value
487 is 6, which corresponds to 63seconds till the last retransmission
488 with the current initial RTO of 1second. With this the final timeout
489 for an active TCP connection attempt will happen after 127seconds.
491 tcp_timestamps - BOOLEAN
492 Enable timestamps as defined in RFC1323.
494 tcp_min_tso_segs - INTEGER
495 Minimal number of segments per TSO frame.
496 Since linux-3.12, TCP does an automatic sizing of TSO frames,
497 depending on flow rate, instead of filling 64Kbytes packets.
498 For specific usages, it's possible to force TCP to build big
499 TSO frames. Note that TCP stack might split too big TSO packets
500 if available window is too small.
503 tcp_tso_win_divisor - INTEGER
504 This allows control over what percentage of the congestion window
505 can be consumed by a single TSO frame.
506 The setting of this parameter is a choice between burstiness and
507 building larger TSO frames.
510 tcp_tw_recycle - BOOLEAN
511 Enable fast recycling TIME-WAIT sockets. Default value is 0.
512 It should not be changed without advice/request of technical
515 tcp_tw_reuse - BOOLEAN
516 Allow to reuse TIME-WAIT sockets for new connections when it is
517 safe from protocol viewpoint. Default value is 0.
518 It should not be changed without advice/request of technical
521 tcp_window_scaling - BOOLEAN
522 Enable window scaling as defined in RFC1323.
524 tcp_wmem - vector of 3 INTEGERs: min, default, max
525 min: Amount of memory reserved for send buffers for TCP sockets.
526 Each TCP socket has rights to use it due to fact of its birth.
529 default: initial size of send buffer used by TCP sockets. This
530 value overrides net.core.wmem_default used by other protocols.
531 It is usually lower than net.core.wmem_default.
534 max: Maximal amount of memory allowed for automatically tuned
535 send buffers for TCP sockets. This value does not override
536 net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables
537 automatic tuning of that socket's send buffer size, in which case
538 this value is ignored.
539 Default: between 64K and 4MB, depending on RAM size.
541 tcp_notsent_lowat - UNSIGNED INTEGER
542 A TCP socket can control the amount of unsent bytes in its write queue,
543 thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll()
544 reports POLLOUT events if the amount of unsent bytes is below a per
545 socket value, and if the write queue is not full. sendmsg() will
546 also not add new buffers if the limit is hit.
548 This global variable controls the amount of unsent data for
549 sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change
550 to the global variable has immediate effect.
552 Default: UINT_MAX (0xFFFFFFFF)
554 tcp_workaround_signed_windows - BOOLEAN
555 If set, assume no receipt of a window scaling option means the
556 remote TCP is broken and treats the window as a signed quantity.
557 If unset, assume the remote TCP is not broken even if we do
558 not receive a window scaling option from them.
561 tcp_dma_copybreak - INTEGER
562 Lower limit, in bytes, of the size of socket reads that will be
563 offloaded to a DMA copy engine, if one is present in the system
564 and CONFIG_NET_DMA is enabled.
567 tcp_thin_linear_timeouts - BOOLEAN
568 Enable dynamic triggering of linear timeouts for thin streams.
569 If set, a check is performed upon retransmission by timeout to
570 determine if the stream is thin (less than 4 packets in flight).
571 As long as the stream is found to be thin, up to 6 linear
572 timeouts may be performed before exponential backoff mode is
573 initiated. This improves retransmission latency for
574 non-aggressive thin streams, often found to be time-dependent.
575 For more information on thin streams, see
576 Documentation/networking/tcp-thin.txt
579 tcp_thin_dupack - BOOLEAN
580 Enable dynamic triggering of retransmissions after one dupACK
581 for thin streams. If set, a check is performed upon reception
582 of a dupACK to determine if the stream is thin (less than 4
583 packets in flight). As long as the stream is found to be thin,
584 data is retransmitted on the first received dupACK. This
585 improves retransmission latency for non-aggressive thin
586 streams, often found to be time-dependent.
587 For more information on thin streams, see
588 Documentation/networking/tcp-thin.txt
591 tcp_limit_output_bytes - INTEGER
592 Controls TCP Small Queue limit per tcp socket.
593 TCP bulk sender tends to increase packets in flight until it
594 gets losses notifications. With SNDBUF autotuning, this can
595 result in a large amount of packets queued in qdisc/device
596 on the local machine, hurting latency of other flows, for
597 typical pfifo_fast qdiscs.
598 tcp_limit_output_bytes limits the number of bytes on qdisc
599 or device to reduce artificial RTT/cwnd and reduce bufferbloat.
602 tcp_challenge_ack_limit - INTEGER
603 Limits number of Challenge ACK sent per second, as recommended
604 in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
609 udp_mem - vector of 3 INTEGERs: min, pressure, max
610 Number of pages allowed for queueing by all UDP sockets.
612 min: Below this number of pages UDP is not bothered about its
613 memory appetite. When amount of memory allocated by UDP exceeds
614 this number, UDP starts to moderate memory usage.
616 pressure: This value was introduced to follow format of tcp_mem.
618 max: Number of pages allowed for queueing by all UDP sockets.
620 Default is calculated at boot time from amount of available memory.
622 udp_rmem_min - INTEGER
623 Minimal size of receive buffer used by UDP sockets in moderation.
624 Each UDP socket is able to use the size for receiving data, even if
625 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
628 udp_wmem_min - INTEGER
629 Minimal size of send buffer used by UDP sockets in moderation.
630 Each UDP socket is able to use the size for sending data, even if
631 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
636 cipso_cache_enable - BOOLEAN
637 If set, enable additions to and lookups from the CIPSO label mapping
638 cache. If unset, additions are ignored and lookups always result in a
639 miss. However, regardless of the setting the cache is still
640 invalidated when required when means you can safely toggle this on and
641 off and the cache will always be "safe".
644 cipso_cache_bucket_size - INTEGER
645 The CIPSO label cache consists of a fixed size hash table with each
646 hash bucket containing a number of cache entries. This variable limits
647 the number of entries in each hash bucket; the larger the value the
648 more CIPSO label mappings that can be cached. When the number of
649 entries in a given hash bucket reaches this limit adding new entries
650 causes the oldest entry in the bucket to be removed to make room.
653 cipso_rbm_optfmt - BOOLEAN
654 Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
655 the CIPSO draft specification (see Documentation/netlabel for details).
656 This means that when set the CIPSO tag will be padded with empty
657 categories in order to make the packet data 32-bit aligned.
660 cipso_rbm_structvalid - BOOLEAN
661 If set, do a very strict check of the CIPSO option when
662 ip_options_compile() is called. If unset, relax the checks done during
663 ip_options_compile(). Either way is "safe" as errors are caught else
664 where in the CIPSO processing code but setting this to 0 (False) should
665 result in less work (i.e. it should be faster) but could cause problems
666 with other implementations that require strict checking.
671 ip_local_port_range - 2 INTEGERS
672 Defines the local port range that is used by TCP and UDP to
673 choose the local port. The first number is the first, the
674 second the last local port number. The default values are
675 32768 and 61000 respectively.
677 ip_local_reserved_ports - list of comma separated ranges
678 Specify the ports which are reserved for known third-party
679 applications. These ports will not be used by automatic port
680 assignments (e.g. when calling connect() or bind() with port
681 number 0). Explicit port allocation behavior is unchanged.
683 The format used for both input and output is a comma separated
684 list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
685 10). Writing to the file will clear all previously reserved
686 ports and update the current list with the one given in the
689 Note that ip_local_port_range and ip_local_reserved_ports
690 settings are independent and both are considered by the kernel
691 when determining which ports are available for automatic port
694 You can reserve ports which are not in the current
695 ip_local_port_range, e.g.:
697 $ cat /proc/sys/net/ipv4/ip_local_port_range
699 $ cat /proc/sys/net/ipv4/ip_local_reserved_ports
702 although this is redundant. However such a setting is useful
703 if later the port range is changed to a value that will
704 include the reserved ports.
708 ip_nonlocal_bind - BOOLEAN
709 If set, allows processes to bind() to non-local IP addresses,
710 which can be quite useful - but may break some applications.
714 If set non-zero, enables support for dynamic addresses.
715 If set to a non-zero value larger than 1, a kernel log
716 message will be printed when dynamic address rewriting
720 ip_early_demux - BOOLEAN
721 Optimize input packet processing down to one demux for
722 certain kinds of local sockets. Currently we only do this
723 for established TCP sockets.
725 It may add an additional cost for pure routing workloads that
726 reduces overall throughput, in such case you should disable it.
729 icmp_echo_ignore_all - BOOLEAN
730 If set non-zero, then the kernel will ignore all ICMP ECHO
734 icmp_echo_ignore_broadcasts - BOOLEAN
735 If set non-zero, then the kernel will ignore all ICMP ECHO and
736 TIMESTAMP requests sent to it via broadcast/multicast.
739 icmp_ratelimit - INTEGER
740 Limit the maximal rates for sending ICMP packets whose type matches
741 icmp_ratemask (see below) to specific targets.
742 0 to disable any limiting,
743 otherwise the minimal space between responses in milliseconds.
746 icmp_ratemask - INTEGER
747 Mask made of ICMP types for which rates are being limited.
748 Significant bits: IHGFEDCBA9876543210
749 Default mask: 0000001100000011000 (6168)
751 Bit definitions (see include/linux/icmp.h):
753 3 Destination Unreachable *
758 C Parameter Problem *
763 H Address Mask Request
766 * These are rate limited by default (see default mask above)
768 icmp_ignore_bogus_error_responses - BOOLEAN
769 Some routers violate RFC1122 by sending bogus responses to broadcast
770 frames. Such violations are normally logged via a kernel warning.
771 If this is set to TRUE, the kernel will not give such warnings, which
772 will avoid log file clutter.
775 icmp_errors_use_inbound_ifaddr - BOOLEAN
777 If zero, icmp error messages are sent with the primary address of
778 the exiting interface.
780 If non-zero, the message will be sent with the primary address of
781 the interface that received the packet that caused the icmp error.
782 This is the behaviour network many administrators will expect from
783 a router. And it can make debugging complicated network layouts
786 Note that if no primary address exists for the interface selected,
787 then the primary address of the first non-loopback interface that
788 has one will be used regardless of this setting.
792 igmp_max_memberships - INTEGER
793 Change the maximum number of multicast groups we can subscribe to.
796 Theoretical maximum value is bounded by having to send a membership
797 report in a single datagram (i.e. the report can't span multiple
798 datagrams, or risk confusing the switch and leaving groups you don't
801 The number of supported groups 'M' is bounded by the number of group
802 report entries you can fit into a single datagram of 65535 bytes.
804 M = 65536-sizeof (ip header)/(sizeof(Group record))
806 Group records are variable length, with a minimum of 12 bytes.
807 So net.ipv4.igmp_max_memberships should not be set higher than:
809 (65536-24) / 12 = 5459
811 The value 5459 assumes no IP header options, so in practice
812 this number may be lower.
814 conf/interface/* changes special settings per interface (where
815 "interface" is the name of your network interface)
817 conf/all/* is special, changes the settings for all interfaces
819 log_martians - BOOLEAN
820 Log packets with impossible addresses to kernel log.
821 log_martians for the interface will be enabled if at least one of
822 conf/{all,interface}/log_martians is set to TRUE,
823 it will be disabled otherwise
825 accept_redirects - BOOLEAN
826 Accept ICMP redirect messages.
827 accept_redirects for the interface will be enabled if:
828 - both conf/{all,interface}/accept_redirects are TRUE in the case
829 forwarding for the interface is enabled
831 - at least one of conf/{all,interface}/accept_redirects is TRUE in the
832 case forwarding for the interface is disabled
833 accept_redirects for the interface will be disabled otherwise
838 Enable IP forwarding on this interface.
840 mc_forwarding - BOOLEAN
841 Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
842 and a multicast routing daemon is required.
843 conf/all/mc_forwarding must also be set to TRUE to enable multicast
844 routing for the interface
847 Integer value used to differentiate the devices by the medium they
848 are attached to. Two devices can have different id values when
849 the broadcast packets are received only on one of them.
850 The default value 0 means that the device is the only interface
851 to its medium, value of -1 means that medium is not known.
853 Currently, it is used to change the proxy_arp behavior:
854 the proxy_arp feature is enabled for packets forwarded between
855 two devices attached to different media.
859 proxy_arp for the interface will be enabled if at least one of
860 conf/{all,interface}/proxy_arp is set to TRUE,
861 it will be disabled otherwise
863 proxy_arp_pvlan - BOOLEAN
864 Private VLAN proxy arp.
865 Basically allow proxy arp replies back to the same interface
866 (from which the ARP request/solicitation was received).
868 This is done to support (ethernet) switch features, like RFC
869 3069, where the individual ports are NOT allowed to
870 communicate with each other, but they are allowed to talk to
871 the upstream router. As described in RFC 3069, it is possible
872 to allow these hosts to communicate through the upstream
873 router by proxy_arp'ing. Don't need to be used together with
876 This technology is known by different names:
877 In RFC 3069 it is called VLAN Aggregation.
878 Cisco and Allied Telesyn call it Private VLAN.
879 Hewlett-Packard call it Source-Port filtering or port-isolation.
880 Ericsson call it MAC-Forced Forwarding (RFC Draft).
882 shared_media - BOOLEAN
883 Send(router) or accept(host) RFC1620 shared media redirects.
884 Overrides ip_secure_redirects.
885 shared_media for the interface will be enabled if at least one of
886 conf/{all,interface}/shared_media is set to TRUE,
887 it will be disabled otherwise
890 secure_redirects - BOOLEAN
891 Accept ICMP redirect messages only for gateways,
892 listed in default gateway list.
893 secure_redirects for the interface will be enabled if at least one of
894 conf/{all,interface}/secure_redirects is set to TRUE,
895 it will be disabled otherwise
898 send_redirects - BOOLEAN
899 Send redirects, if router.
900 send_redirects for the interface will be enabled if at least one of
901 conf/{all,interface}/send_redirects is set to TRUE,
902 it will be disabled otherwise
905 bootp_relay - BOOLEAN
906 Accept packets with source address 0.b.c.d destined
907 not to this host as local ones. It is supposed, that
908 BOOTP relay daemon will catch and forward such packets.
909 conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
914 accept_source_route - BOOLEAN
915 Accept packets with SRR option.
916 conf/all/accept_source_route must also be set to TRUE to accept packets
917 with SRR option on the interface
918 default TRUE (router)
921 accept_local - BOOLEAN
922 Accept packets with local source addresses. In combination
923 with suitable routing, this can be used to direct packets
924 between two local interfaces over the wire and have them
927 rp_filter must be set to a non-zero value in order for
928 accept_local to have an effect.
932 route_localnet - BOOLEAN
933 Do not consider loopback addresses as martian source or destination
934 while routing. This enables the use of 127/8 for local routing purposes.
938 0 - No source validation.
939 1 - Strict mode as defined in RFC3704 Strict Reverse Path
940 Each incoming packet is tested against the FIB and if the interface
941 is not the best reverse path the packet check will fail.
942 By default failed packets are discarded.
943 2 - Loose mode as defined in RFC3704 Loose Reverse Path
944 Each incoming packet's source address is also tested against the FIB
945 and if the source address is not reachable via any interface
946 the packet check will fail.
948 Current recommended practice in RFC3704 is to enable strict mode
949 to prevent IP spoofing from DDos attacks. If using asymmetric routing
950 or other complicated routing, then loose mode is recommended.
952 The max value from conf/{all,interface}/rp_filter is used
953 when doing source validation on the {interface}.
955 Default value is 0. Note that some distributions enable it
959 1 - Allows you to have multiple network interfaces on the same
960 subnet, and have the ARPs for each interface be answered
961 based on whether or not the kernel would route a packet from
962 the ARP'd IP out that interface (therefore you must use source
963 based routing for this to work). In other words it allows control
964 of which cards (usually 1) will respond to an arp request.
966 0 - (default) The kernel can respond to arp requests with addresses
967 from other interfaces. This may seem wrong but it usually makes
968 sense, because it increases the chance of successful communication.
969 IP addresses are owned by the complete host on Linux, not by
970 particular interfaces. Only for more complex setups like load-
971 balancing, does this behaviour cause problems.
973 arp_filter for the interface will be enabled if at least one of
974 conf/{all,interface}/arp_filter is set to TRUE,
975 it will be disabled otherwise
977 arp_announce - INTEGER
978 Define different restriction levels for announcing the local
979 source IP address from IP packets in ARP requests sent on
981 0 - (default) Use any local address, configured on any interface
982 1 - Try to avoid local addresses that are not in the target's
983 subnet for this interface. This mode is useful when target
984 hosts reachable via this interface require the source IP
985 address in ARP requests to be part of their logical network
986 configured on the receiving interface. When we generate the
987 request we will check all our subnets that include the
988 target IP and will preserve the source address if it is from
989 such subnet. If there is no such subnet we select source
990 address according to the rules for level 2.
991 2 - Always use the best local address for this target.
992 In this mode we ignore the source address in the IP packet
993 and try to select local address that we prefer for talks with
994 the target host. Such local address is selected by looking
995 for primary IP addresses on all our subnets on the outgoing
996 interface that include the target IP address. If no suitable
997 local address is found we select the first local address
998 we have on the outgoing interface or on all other interfaces,
999 with the hope we will receive reply for our request and
1000 even sometimes no matter the source IP address we announce.
1002 The max value from conf/{all,interface}/arp_announce is used.
1004 Increasing the restriction level gives more chance for
1005 receiving answer from the resolved target while decreasing
1006 the level announces more valid sender's information.
1008 arp_ignore - INTEGER
1009 Define different modes for sending replies in response to
1010 received ARP requests that resolve local target IP addresses:
1011 0 - (default): reply for any local target IP address, configured
1013 1 - reply only if the target IP address is local address
1014 configured on the incoming interface
1015 2 - reply only if the target IP address is local address
1016 configured on the incoming interface and both with the
1017 sender's IP address are part from same subnet on this interface
1018 3 - do not reply for local addresses configured with scope host,
1019 only resolutions for global and link addresses are replied
1021 8 - do not reply for all local addresses
1023 The max value from conf/{all,interface}/arp_ignore is used
1024 when ARP request is received on the {interface}
1026 arp_notify - BOOLEAN
1027 Define mode for notification of address and device changes.
1028 0 - (default): do nothing
1029 1 - Generate gratuitous arp requests when device is brought up
1030 or hardware address changes.
1032 arp_accept - BOOLEAN
1033 Define behavior for gratuitous ARP frames who's IP is not
1034 already present in the ARP table:
1035 0 - don't create new entries in the ARP table
1036 1 - create new entries in the ARP table
1038 Both replies and requests type gratuitous arp will trigger the
1039 ARP table to be updated, if this setting is on.
1041 If the ARP table already contains the IP address of the
1042 gratuitous arp frame, the arp table will be updated regardless
1043 if this setting is on or off.
1046 app_solicit - INTEGER
1047 The maximum number of probes to send to the user space ARP daemon
1048 via netlink before dropping back to multicast probes (see
1049 mcast_solicit). Defaults to 0.
1051 disable_policy - BOOLEAN
1052 Disable IPSEC policy (SPD) for this interface
1054 disable_xfrm - BOOLEAN
1055 Disable IPSEC encryption on this interface, whatever the policy
1057 igmpv2_unsolicited_report_interval - INTEGER
1058 The interval in milliseconds in which the next unsolicited
1059 IGMPv1 or IGMPv2 report retransmit will take place.
1060 Default: 10000 (10 seconds)
1062 igmpv3_unsolicited_report_interval - INTEGER
1063 The interval in milliseconds in which the next unsolicited
1064 IGMPv3 report retransmit will take place.
1065 Default: 1000 (1 seconds)
1068 Allows you to write a number, which can be used as required.
1072 kuznet@ms2.inr.ac.ru
1078 delon.nicolas@wanadoo.fr
1083 /proc/sys/net/ipv6/* Variables:
1085 IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
1086 apply to IPv6 [XXX?].
1088 bindv6only - BOOLEAN
1089 Default value for IPV6_V6ONLY socket option,
1090 which restricts use of the IPv6 socket to IPv6 communication
1092 TRUE: disable IPv4-mapped address feature
1093 FALSE: enable IPv4-mapped address feature
1095 Default: FALSE (as specified in RFC3493)
1099 ip6frag_high_thresh - INTEGER
1100 Maximum memory used to reassemble IPv6 fragments. When
1101 ip6frag_high_thresh bytes of memory is allocated for this purpose,
1102 the fragment handler will toss packets until ip6frag_low_thresh
1105 ip6frag_low_thresh - INTEGER
1106 See ip6frag_high_thresh
1108 ip6frag_time - INTEGER
1109 Time in seconds to keep an IPv6 fragment in memory.
1111 ip6frag_secret_interval - INTEGER
1112 Regeneration interval (in seconds) of the hash secret (or lifetime
1113 for the hash secret) for IPv6 fragments.
1117 Change the interface-specific default settings.
1121 Change all the interface-specific settings.
1123 [XXX: Other special features than forwarding?]
1125 conf/all/forwarding - BOOLEAN
1126 Enable global IPv6 forwarding between all interfaces.
1128 IPv4 and IPv6 work differently here; e.g. netfilter must be used
1129 to control which interfaces may forward packets and which not.
1131 This also sets all interfaces' Host/Router setting
1132 'forwarding' to the specified value. See below for details.
1134 This referred to as global forwarding.
1140 Change special settings per interface.
1142 The functional behaviour for certain settings is different
1143 depending on whether local forwarding is enabled or not.
1146 Accept Router Advertisements; autoconfigure using them.
1148 It also determines whether or not to transmit Router
1149 Solicitations. If and only if the functional setting is to
1150 accept Router Advertisements, Router Solicitations will be
1153 Possible values are:
1154 0 Do not accept Router Advertisements.
1155 1 Accept Router Advertisements if forwarding is disabled.
1156 2 Overrule forwarding behaviour. Accept Router Advertisements
1157 even if forwarding is enabled.
1159 Functional default: enabled if local forwarding is disabled.
1160 disabled if local forwarding is enabled.
1162 accept_ra_defrtr - BOOLEAN
1163 Learn default router in Router Advertisement.
1165 Functional default: enabled if accept_ra is enabled.
1166 disabled if accept_ra is disabled.
1168 accept_ra_pinfo - BOOLEAN
1169 Learn Prefix Information in Router Advertisement.
1171 Functional default: enabled if accept_ra is enabled.
1172 disabled if accept_ra is disabled.
1174 accept_ra_rt_info_max_plen - INTEGER
1175 Maximum prefix length of Route Information in RA.
1177 Route Information w/ prefix larger than or equal to this
1178 variable shall be ignored.
1180 Functional default: 0 if accept_ra_rtr_pref is enabled.
1181 -1 if accept_ra_rtr_pref is disabled.
1183 accept_ra_rtr_pref - BOOLEAN
1184 Accept Router Preference in RA.
1186 Functional default: enabled if accept_ra is enabled.
1187 disabled if accept_ra is disabled.
1189 accept_redirects - BOOLEAN
1192 Functional default: enabled if local forwarding is disabled.
1193 disabled if local forwarding is enabled.
1195 accept_source_route - INTEGER
1196 Accept source routing (routing extension header).
1198 >= 0: Accept only routing header type 2.
1199 < 0: Do not accept routing header.
1204 Autoconfigure addresses using Prefix Information in Router
1207 Functional default: enabled if accept_ra_pinfo is enabled.
1208 disabled if accept_ra_pinfo is disabled.
1210 dad_transmits - INTEGER
1211 The amount of Duplicate Address Detection probes to send.
1214 forwarding - INTEGER
1215 Configure interface-specific Host/Router behaviour.
1217 Note: It is recommended to have the same setting on all
1218 interfaces; mixed router/host scenarios are rather uncommon.
1220 Possible values are:
1221 0 Forwarding disabled
1222 1 Forwarding enabled
1226 By default, Host behaviour is assumed. This means:
1228 1. IsRouter flag is not set in Neighbour Advertisements.
1229 2. If accept_ra is TRUE (default), transmit Router
1231 3. If accept_ra is TRUE (default), accept Router
1232 Advertisements (and do autoconfiguration).
1233 4. If accept_redirects is TRUE (default), accept Redirects.
1237 If local forwarding is enabled, Router behaviour is assumed.
1238 This means exactly the reverse from the above:
1240 1. IsRouter flag is set in Neighbour Advertisements.
1241 2. Router Solicitations are not sent unless accept_ra is 2.
1242 3. Router Advertisements are ignored unless accept_ra is 2.
1243 4. Redirects are ignored.
1245 Default: 0 (disabled) if global forwarding is disabled (default),
1246 otherwise 1 (enabled).
1249 Default Hop Limit to set.
1253 Default Maximum Transfer Unit
1254 Default: 1280 (IPv6 required minimum)
1256 router_probe_interval - INTEGER
1257 Minimum interval (in seconds) between Router Probing described
1262 router_solicitation_delay - INTEGER
1263 Number of seconds to wait after interface is brought up
1264 before sending Router Solicitations.
1267 router_solicitation_interval - INTEGER
1268 Number of seconds to wait between Router Solicitations.
1271 router_solicitations - INTEGER
1272 Number of Router Solicitations to send until assuming no
1273 routers are present.
1276 use_tempaddr - INTEGER
1277 Preference for Privacy Extensions (RFC3041).
1278 <= 0 : disable Privacy Extensions
1279 == 1 : enable Privacy Extensions, but prefer public
1280 addresses over temporary addresses.
1281 > 1 : enable Privacy Extensions and prefer temporary
1282 addresses over public addresses.
1283 Default: 0 (for most devices)
1284 -1 (for point-to-point devices and loopback devices)
1286 temp_valid_lft - INTEGER
1287 valid lifetime (in seconds) for temporary addresses.
1288 Default: 604800 (7 days)
1290 temp_prefered_lft - INTEGER
1291 Preferred lifetime (in seconds) for temporary addresses.
1292 Default: 86400 (1 day)
1294 max_desync_factor - INTEGER
1295 Maximum value for DESYNC_FACTOR, which is a random value
1296 that ensures that clients don't synchronize with each
1297 other and generate new addresses at exactly the same time.
1298 value is in seconds.
1301 regen_max_retry - INTEGER
1302 Number of attempts before give up attempting to generate
1303 valid temporary addresses.
1306 max_addresses - INTEGER
1307 Maximum number of autoconfigured addresses per interface. Setting
1308 to zero disables the limitation. It is not recommended to set this
1309 value too large (or to zero) because it would be an easy way to
1310 crash the kernel by allowing too many addresses to be created.
1313 disable_ipv6 - BOOLEAN
1314 Disable IPv6 operation. If accept_dad is set to 2, this value
1315 will be dynamically set to TRUE if DAD fails for the link-local
1317 Default: FALSE (enable IPv6 operation)
1319 When this value is changed from 1 to 0 (IPv6 is being enabled),
1320 it will dynamically create a link-local address on the given
1321 interface and start Duplicate Address Detection, if necessary.
1323 When this value is changed from 0 to 1 (IPv6 is being disabled),
1324 it will dynamically delete all address on the given interface.
1326 accept_dad - INTEGER
1327 Whether to accept DAD (Duplicate Address Detection).
1329 1: Enable DAD (default)
1330 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
1331 link-local address has been found.
1333 force_tllao - BOOLEAN
1334 Enable sending the target link-layer address option even when
1335 responding to a unicast neighbor solicitation.
1338 Quoting from RFC 2461, section 4.4, Target link-layer address:
1340 "The option MUST be included for multicast solicitations in order to
1341 avoid infinite Neighbor Solicitation "recursion" when the peer node
1342 does not have a cache entry to return a Neighbor Advertisements
1343 message. When responding to unicast solicitations, the option can be
1344 omitted since the sender of the solicitation has the correct link-
1345 layer address; otherwise it would not have be able to send the unicast
1346 solicitation in the first place. However, including the link-layer
1347 address in this case adds little overhead and eliminates a potential
1348 race condition where the sender deletes the cached link-layer address
1349 prior to receiving a response to a previous solicitation."
1351 ndisc_notify - BOOLEAN
1352 Define mode for notification of address and device changes.
1353 0 - (default): do nothing
1354 1 - Generate unsolicited neighbour advertisements when device is brought
1355 up or hardware address changes.
1357 mldv1_unsolicited_report_interval - INTEGER
1358 The interval in milliseconds in which the next unsolicited
1359 MLDv1 report retransmit will take place.
1360 Default: 10000 (10 seconds)
1362 mldv2_unsolicited_report_interval - INTEGER
1363 The interval in milliseconds in which the next unsolicited
1364 MLDv2 report retransmit will take place.
1365 Default: 1000 (1 second)
1367 force_mld_version - INTEGER
1368 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed
1369 1 - Enforce to use MLD version 1
1370 2 - Enforce to use MLD version 2
1372 suppress_frag_ndisc - INTEGER
1373 Control RFC 6980 (Security Implications of IPv6 Fragmentation
1374 with IPv6 Neighbor Discovery) behavior:
1375 1 - (default) discard fragmented neighbor discovery packets
1376 0 - allow fragmented neighbor discovery packets
1380 Limit the maximal rates for sending ICMPv6 packets.
1381 0 to disable any limiting,
1382 otherwise the minimal space between responses in milliseconds.
1387 Pekka Savola <pekkas@netcore.fi>
1388 YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
1391 /proc/sys/net/bridge/* Variables:
1393 bridge-nf-call-arptables - BOOLEAN
1394 1 : pass bridged ARP traffic to arptables' FORWARD chain.
1398 bridge-nf-call-iptables - BOOLEAN
1399 1 : pass bridged IPv4 traffic to iptables' chains.
1403 bridge-nf-call-ip6tables - BOOLEAN
1404 1 : pass bridged IPv6 traffic to ip6tables' chains.
1408 bridge-nf-filter-vlan-tagged - BOOLEAN
1409 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
1413 bridge-nf-filter-pppoe-tagged - BOOLEAN
1414 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
1418 bridge-nf-pass-vlan-input-dev - BOOLEAN
1419 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
1420 interface on the bridge and set the netfilter input device to the vlan.
1421 This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT
1422 target work with vlan-on-top-of-bridge interfaces. When no matching
1423 vlan interface is found, or this switch is off, the input device is
1424 set to the bridge interface.
1425 0: disable bridge netfilter vlan interface lookup.
1428 proc/sys/net/sctp/* Variables:
1430 addip_enable - BOOLEAN
1431 Enable or disable extension of Dynamic Address Reconfiguration
1432 (ADD-IP) functionality specified in RFC5061. This extension provides
1433 the ability to dynamically add and remove new addresses for the SCTP
1436 1: Enable extension.
1438 0: Disable extension.
1442 addip_noauth_enable - BOOLEAN
1443 Dynamic Address Reconfiguration (ADD-IP) requires the use of
1444 authentication to protect the operations of adding or removing new
1445 addresses. This requirement is mandated so that unauthorized hosts
1446 would not be able to hijack associations. However, older
1447 implementations may not have implemented this requirement while
1448 allowing the ADD-IP extension. For reasons of interoperability,
1449 we provide this variable to control the enforcement of the
1450 authentication requirement.
1452 1: Allow ADD-IP extension to be used without authentication. This
1453 should only be set in a closed environment for interoperability
1454 with older implementations.
1456 0: Enforce the authentication requirement
1460 auth_enable - BOOLEAN
1461 Enable or disable Authenticated Chunks extension. This extension
1462 provides the ability to send and receive authenticated chunks and is
1463 required for secure operation of Dynamic Address Reconfiguration
1466 1: Enable this extension.
1467 0: Disable this extension.
1471 prsctp_enable - BOOLEAN
1472 Enable or disable the Partial Reliability extension (RFC3758) which
1473 is used to notify peers that a given DATA should no longer be expected.
1481 The limit of the number of new packets that can be initially sent. It
1482 controls how bursty the generated traffic can be.
1486 association_max_retrans - INTEGER
1487 Set the maximum number for retransmissions that an association can
1488 attempt deciding that the remote end is unreachable. If this value
1489 is exceeded, the association is terminated.
1493 max_init_retransmits - INTEGER
1494 The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
1495 that an association will attempt before declaring the destination
1496 unreachable and terminating.
1500 path_max_retrans - INTEGER
1501 The maximum number of retransmissions that will be attempted on a given
1502 path. Once this threshold is exceeded, the path is considered
1503 unreachable, and new traffic will use a different path when the
1504 association is multihomed.
1508 pf_retrans - INTEGER
1509 The number of retransmissions that will be attempted on a given path
1510 before traffic is redirected to an alternate transport (should one
1511 exist). Note this is distinct from path_max_retrans, as a path that
1512 passes the pf_retrans threshold can still be used. Its only
1513 deprioritized when a transmission path is selected by the stack. This
1514 setting is primarily used to enable fast failover mechanisms without
1515 having to reduce path_max_retrans to a very low value. See:
1516 http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
1517 for details. Note also that a value of pf_retrans > path_max_retrans
1518 disables this feature
1522 rto_initial - INTEGER
1523 The initial round trip timeout value in milliseconds that will be used
1524 in calculating round trip times. This is the initial time interval
1525 for retransmissions.
1530 The maximum value (in milliseconds) of the round trip timeout. This
1531 is the largest time interval that can elapse between retransmissions.
1536 The minimum value (in milliseconds) of the round trip timeout. This
1537 is the smallest time interval the can elapse between retransmissions.
1541 hb_interval - INTEGER
1542 The interval (in milliseconds) between HEARTBEAT chunks. These chunks
1543 are sent at the specified interval on idle paths to probe the state of
1544 a given path between 2 associations.
1548 sack_timeout - INTEGER
1549 The amount of time (in milliseconds) that the implementation will wait
1554 valid_cookie_life - INTEGER
1555 The default lifetime of the SCTP cookie (in milliseconds). The cookie
1556 is used during association establishment.
1560 cookie_preserve_enable - BOOLEAN
1561 Enable or disable the ability to extend the lifetime of the SCTP cookie
1562 that is used during the establishment phase of SCTP association
1564 1: Enable cookie lifetime extension.
1569 cookie_hmac_alg - STRING
1570 Select the hmac algorithm used when generating the cookie value sent by
1571 a listening sctp socket to a connecting client in the INIT-ACK chunk.
1576 Ability to assign md5 or sha1 as the selected alg is predicated on the
1577 configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
1578 CONFIG_CRYPTO_SHA1).
1580 Default: Dependent on configuration. MD5 if available, else SHA1 if
1581 available, else none.
1583 rcvbuf_policy - INTEGER
1584 Determines if the receive buffer is attributed to the socket or to
1585 association. SCTP supports the capability to create multiple
1586 associations on a single socket. When using this capability, it is
1587 possible that a single stalled association that's buffering a lot
1588 of data may block other associations from delivering their data by
1589 consuming all of the receive buffer space. To work around this,
1590 the rcvbuf_policy could be set to attribute the receiver buffer space
1591 to each association instead of the socket. This prevents the described
1594 1: rcvbuf space is per association
1595 0: rcvbuf space is per socket
1599 sndbuf_policy - INTEGER
1600 Similar to rcvbuf_policy above, this applies to send buffer space.
1602 1: Send buffer is tracked per association
1603 0: Send buffer is tracked per socket.
1607 sctp_mem - vector of 3 INTEGERs: min, pressure, max
1608 Number of pages allowed for queueing by all SCTP sockets.
1610 min: Below this number of pages SCTP is not bothered about its
1611 memory appetite. When amount of memory allocated by SCTP exceeds
1612 this number, SCTP starts to moderate memory usage.
1614 pressure: This value was introduced to follow format of tcp_mem.
1616 max: Number of pages allowed for queueing by all SCTP sockets.
1618 Default is calculated at boot time from amount of available memory.
1620 sctp_rmem - vector of 3 INTEGERs: min, default, max
1621 Only the first value ("min") is used, "default" and "max" are
1624 min: Minimal size of receive buffer used by SCTP socket.
1625 It is guaranteed to each SCTP socket (but not association) even
1626 under moderate memory pressure.
1630 sctp_wmem - vector of 3 INTEGERs: min, default, max
1631 Currently this tunable has no effect.
1633 addr_scope_policy - INTEGER
1634 Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
1636 0 - Disable IPv4 address scoping
1637 1 - Enable IPv4 address scoping
1638 2 - Follow draft but allow IPv4 private addresses
1639 3 - Follow draft but allow IPv4 link local addresses
1644 /proc/sys/net/core/*
1645 Please see: Documentation/sysctl/net.txt for descriptions of these entries.
1648 /proc/sys/net/unix/*
1649 max_dgram_qlen - INTEGER
1650 The maximum length of dgram socket receive queue
1657 /proc/sys/net/irda/*
1658 fast_poll_increase FIXME
1659 warn_noreply_time FIXME
1660 discovery_slots FIXME
1663 discovery_timeout FIXME
1664 lap_keepalive_time FIXME
1665 max_noreply_time FIXME
1666 max_tx_data_size FIXME
1668 min_tx_turn_time FIXME