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.
29 Mode 3 is a hardened pmtu discover mode. The kernel will only
30 accept fragmentation-needed errors if the underlying protocol
31 can verify them besides a plain socket lookup. Current
32 protocols for which pmtu events will be honored are TCP, SCTP
33 and DCCP as they verify e.g. the sequence number or the
34 association. This mode should not be enabled globally but is
35 only intended to secure e.g. name servers in namespaces where
36 TCP path mtu must still work but path MTU information of other
37 protocols should be discarded. If enabled globally this mode
38 could break other protocols.
44 default 552 - minimum discovered Path MTU
46 ip_forward_use_pmtu - BOOLEAN
47 By default we don't trust protocol path MTUs while forwarding
48 because they could be easily forged and can lead to unwanted
49 fragmentation by the router.
50 You only need to enable this if you have user-space software
51 which tries to discover path mtus by itself and depends on the
52 kernel honoring this information. This is normally not the
59 fwmark_reflect - BOOLEAN
60 Controls the fwmark of kernel-generated IPv4 reply packets that are not
61 associated with a socket for example, TCP RSTs or ICMP echo replies).
62 If unset, these packets have a fwmark of zero. If set, they have the
63 fwmark of the packet they are replying to.
66 fib_multipath_use_neigh - BOOLEAN
67 Use status of existing neighbor entry when determining nexthop for
68 multipath routes. If disabled, neighbor information is not used and
69 packets could be directed to a failed nexthop. Only valid for kernels
70 built with CONFIG_IP_ROUTE_MULTIPATH enabled.
76 fib_multipath_hash_policy - INTEGER
77 Controls which hash policy to use for multipath routes. Only valid
78 for kernels built with CONFIG_IP_ROUTE_MULTIPATH enabled.
84 ip_forward_update_priority - INTEGER
85 Whether to update SKB priority from "TOS" field in IPv4 header after it
86 is forwarded. The new SKB priority is mapped from TOS field value
87 according to an rt_tos2priority table (see e.g. man tc-prio).
88 Default: 1 (Update priority.)
90 0 - Do not update priority.
93 route/max_size - INTEGER
94 Maximum number of routes allowed in the kernel. Increase
95 this when using large numbers of interfaces and/or routes.
96 From linux kernel 3.6 onwards, this is deprecated for ipv4
97 as route cache is no longer used.
99 neigh/default/gc_thresh1 - INTEGER
100 Minimum number of entries to keep. Garbage collector will not
101 purge entries if there are fewer than this number.
104 neigh/default/gc_thresh2 - INTEGER
105 Threshold when garbage collector becomes more aggressive about
106 purging entries. Entries older than 5 seconds will be cleared
107 when over this number.
110 neigh/default/gc_thresh3 - INTEGER
111 Maximum number of neighbor entries allowed. Increase this
112 when using large numbers of interfaces and when communicating
113 with large numbers of directly-connected peers.
116 neigh/default/unres_qlen_bytes - INTEGER
117 The maximum number of bytes which may be used by packets
118 queued for each unresolved address by other network layers.
120 Setting negative value is meaningless and will return error.
121 Default: SK_WMEM_MAX, (same as net.core.wmem_default).
122 Exact value depends on architecture and kernel options,
123 but should be enough to allow queuing 256 packets
126 neigh/default/unres_qlen - INTEGER
127 The maximum number of packets which may be queued for each
128 unresolved address by other network layers.
129 (deprecated in linux 3.3) : use unres_qlen_bytes instead.
130 Prior to linux 3.3, the default value is 3 which may cause
131 unexpected packet loss. The current default value is calculated
132 according to default value of unres_qlen_bytes and true size of
136 mtu_expires - INTEGER
137 Time, in seconds, that cached PMTU information is kept.
139 min_adv_mss - INTEGER
140 The advertised MSS depends on the first hop route MTU, but will
141 never be lower than this setting.
145 ipfrag_high_thresh - LONG INTEGER
146 Maximum memory used to reassemble IP fragments.
148 ipfrag_low_thresh - LONG INTEGER
149 (Obsolete since linux-4.17)
150 Maximum memory used to reassemble IP fragments before the kernel
151 begins to remove incomplete fragment queues to free up resources.
152 The kernel still accepts new fragments for defragmentation.
154 ipfrag_time - INTEGER
155 Time in seconds to keep an IP fragment in memory.
157 ipfrag_max_dist - INTEGER
158 ipfrag_max_dist is a non-negative integer value which defines the
159 maximum "disorder" which is allowed among fragments which share a
160 common IP source address. Note that reordering of packets is
161 not unusual, but if a large number of fragments arrive from a source
162 IP address while a particular fragment queue remains incomplete, it
163 probably indicates that one or more fragments belonging to that queue
164 have been lost. When ipfrag_max_dist is positive, an additional check
165 is done on fragments before they are added to a reassembly queue - if
166 ipfrag_max_dist (or more) fragments have arrived from a particular IP
167 address between additions to any IP fragment queue using that source
168 address, it's presumed that one or more fragments in the queue are
169 lost. The existing fragment queue will be dropped, and a new one
170 started. An ipfrag_max_dist value of zero disables this check.
172 Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
173 result in unnecessarily dropping fragment queues when normal
174 reordering of packets occurs, which could lead to poor application
175 performance. Using a very large value, e.g. 50000, increases the
176 likelihood of incorrectly reassembling IP fragments that originate
177 from different IP datagrams, which could result in data corruption.
182 inet_peer_threshold - INTEGER
183 The approximate size of the storage. Starting from this threshold
184 entries will be thrown aggressively. This threshold also determines
185 entries' time-to-live and time intervals between garbage collection
186 passes. More entries, less time-to-live, less GC interval.
188 inet_peer_minttl - INTEGER
189 Minimum time-to-live of entries. Should be enough to cover fragment
190 time-to-live on the reassembling side. This minimum time-to-live is
191 guaranteed if the pool size is less than inet_peer_threshold.
194 inet_peer_maxttl - INTEGER
195 Maximum time-to-live of entries. Unused entries will expire after
196 this period of time if there is no memory pressure on the pool (i.e.
197 when the number of entries in the pool is very small).
203 Limit of socket listen() backlog, known in userspace as SOMAXCONN.
204 Defaults to 128. See also tcp_max_syn_backlog for additional tuning
207 tcp_abort_on_overflow - BOOLEAN
208 If listening service is too slow to accept new connections,
209 reset them. Default state is FALSE. It means that if overflow
210 occurred due to a burst, connection will recover. Enable this
211 option _only_ if you are really sure that listening daemon
212 cannot be tuned to accept connections faster. Enabling this
213 option can harm clients of your server.
215 tcp_adv_win_scale - INTEGER
216 Count buffering overhead as bytes/2^tcp_adv_win_scale
217 (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
219 Possible values are [-31, 31], inclusive.
222 tcp_allowed_congestion_control - STRING
223 Show/set the congestion control choices available to non-privileged
224 processes. The list is a subset of those listed in
225 tcp_available_congestion_control.
226 Default is "reno" and the default setting (tcp_congestion_control).
228 tcp_app_win - INTEGER
229 Reserve max(window/2^tcp_app_win, mss) of window for application
230 buffer. Value 0 is special, it means that nothing is reserved.
233 tcp_autocorking - BOOLEAN
234 Enable TCP auto corking :
235 When applications do consecutive small write()/sendmsg() system calls,
236 we try to coalesce these small writes as much as possible, to lower
237 total amount of sent packets. This is done if at least one prior
238 packet for the flow is waiting in Qdisc queues or device transmit
239 queue. Applications can still use TCP_CORK for optimal behavior
240 when they know how/when to uncork their sockets.
243 tcp_available_congestion_control - STRING
244 Shows the available congestion control choices that are registered.
245 More congestion control algorithms may be available as modules,
248 tcp_base_mss - INTEGER
249 The initial value of search_low to be used by the packetization layer
250 Path MTU discovery (MTU probing). If MTU probing is enabled,
251 this is the initial MSS used by the connection.
253 tcp_congestion_control - STRING
254 Set the congestion control algorithm to be used for new
255 connections. The algorithm "reno" is always available, but
256 additional choices may be available based on kernel configuration.
257 Default is set as part of kernel configuration.
258 For passive connections, the listener congestion control choice
260 [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
263 Allows TCP to send "duplicate" SACKs.
265 tcp_early_retrans - INTEGER
266 Tail loss probe (TLP) converts RTOs occurring due to tail
267 losses into fast recovery (draft-ietf-tcpm-rack). Note that
268 TLP requires RACK to function properly (see tcp_recovery below)
275 Control use of Explicit Congestion Notification (ECN) by TCP.
276 ECN is used only when both ends of the TCP connection indicate
277 support for it. This feature is useful in avoiding losses due
278 to congestion by allowing supporting routers to signal
279 congestion before having to drop packets.
281 0 Disable ECN. Neither initiate nor accept ECN.
282 1 Enable ECN when requested by incoming connections and
283 also request ECN on outgoing connection attempts.
284 2 Enable ECN when requested by incoming connections
285 but do not request ECN on outgoing connections.
288 tcp_ecn_fallback - BOOLEAN
289 If the kernel detects that ECN connection misbehaves, enable fall
290 back to non-ECN. Currently, this knob implements the fallback
291 from RFC3168, section 6.1.1.1., but we reserve that in future,
292 additional detection mechanisms could be implemented under this
293 knob. The value is not used, if tcp_ecn or per route (or congestion
294 control) ECN settings are disabled.
295 Default: 1 (fallback enabled)
298 This is a legacy option, it has no effect anymore.
300 tcp_fin_timeout - INTEGER
301 The length of time an orphaned (no longer referenced by any
302 application) connection will remain in the FIN_WAIT_2 state
303 before it is aborted at the local end. While a perfectly
304 valid "receive only" state for an un-orphaned connection, an
305 orphaned connection in FIN_WAIT_2 state could otherwise wait
306 forever for the remote to close its end of the connection.
311 Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
312 F-RTO is an enhanced recovery algorithm for TCP retransmission
313 timeouts. It is particularly beneficial in networks where the
314 RTT fluctuates (e.g., wireless). F-RTO is sender-side only
315 modification. It does not require any support from the peer.
317 By default it's enabled with a non-zero value. 0 disables F-RTO.
319 tcp_fwmark_accept - BOOLEAN
320 If set, incoming connections to listening sockets that do not have a
321 socket mark will set the mark of the accepting socket to the fwmark of
322 the incoming SYN packet. This will cause all packets on that connection
323 (starting from the first SYNACK) to be sent with that fwmark. The
324 listening socket's mark is unchanged. Listening sockets that already
325 have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are
330 tcp_invalid_ratelimit - INTEGER
331 Limit the maximal rate for sending duplicate acknowledgments
332 in response to incoming TCP packets that are for an existing
333 connection but that are invalid due to any of these reasons:
335 (a) out-of-window sequence number,
336 (b) out-of-window acknowledgment number, or
337 (c) PAWS (Protection Against Wrapped Sequence numbers) check failure
339 This can help mitigate simple "ack loop" DoS attacks, wherein
340 a buggy or malicious middlebox or man-in-the-middle can
341 rewrite TCP header fields in manner that causes each endpoint
342 to think that the other is sending invalid TCP segments, thus
343 causing each side to send an unterminating stream of duplicate
344 acknowledgments for invalid segments.
346 Using 0 disables rate-limiting of dupacks in response to
347 invalid segments; otherwise this value specifies the minimal
348 space between sending such dupacks, in milliseconds.
350 Default: 500 (milliseconds).
352 tcp_keepalive_time - INTEGER
353 How often TCP sends out keepalive messages when keepalive is enabled.
356 tcp_keepalive_probes - INTEGER
357 How many keepalive probes TCP sends out, until it decides that the
358 connection is broken. Default value: 9.
360 tcp_keepalive_intvl - INTEGER
361 How frequently the probes are send out. Multiplied by
362 tcp_keepalive_probes it is time to kill not responding connection,
363 after probes started. Default value: 75sec i.e. connection
364 will be aborted after ~11 minutes of retries.
366 tcp_l3mdev_accept - BOOLEAN
367 Enables child sockets to inherit the L3 master device index.
368 Enabling this option allows a "global" listen socket to work
369 across L3 master domains (e.g., VRFs) with connected sockets
370 derived from the listen socket to be bound to the L3 domain in
371 which the packets originated. Only valid when the kernel was
372 compiled with CONFIG_NET_L3_MASTER_DEV.
374 tcp_low_latency - BOOLEAN
375 This is a legacy option, it has no effect anymore.
377 tcp_max_orphans - INTEGER
378 Maximal number of TCP sockets not attached to any user file handle,
379 held by system. If this number is exceeded orphaned connections are
380 reset immediately and warning is printed. This limit exists
381 only to prevent simple DoS attacks, you _must_ not rely on this
382 or lower the limit artificially, but rather increase it
383 (probably, after increasing installed memory),
384 if network conditions require more than default value,
385 and tune network services to linger and kill such states
386 more aggressively. Let me to remind again: each orphan eats
387 up to ~64K of unswappable memory.
389 tcp_max_syn_backlog - INTEGER
390 Maximal number of remembered connection requests, which have not
391 received an acknowledgment from connecting client.
392 The minimal value is 128 for low memory machines, and it will
393 increase in proportion to the memory of machine.
394 If server suffers from overload, try increasing this number.
396 tcp_max_tw_buckets - INTEGER
397 Maximal number of timewait sockets held by system simultaneously.
398 If this number is exceeded time-wait socket is immediately destroyed
399 and warning is printed. This limit exists only to prevent
400 simple DoS attacks, you _must_ not lower the limit artificially,
401 but rather increase it (probably, after increasing installed memory),
402 if network conditions require more than default value.
404 tcp_mem - vector of 3 INTEGERs: min, pressure, max
405 min: below this number of pages TCP is not bothered about its
408 pressure: when amount of memory allocated by TCP exceeds this number
409 of pages, TCP moderates its memory consumption and enters memory
410 pressure mode, which is exited when memory consumption falls
413 max: number of pages allowed for queueing by all TCP sockets.
415 Defaults are calculated at boot time from amount of available
418 tcp_min_rtt_wlen - INTEGER
419 The window length of the windowed min filter to track the minimum RTT.
420 A shorter window lets a flow more quickly pick up new (higher)
421 minimum RTT when it is moved to a longer path (e.g., due to traffic
422 engineering). A longer window makes the filter more resistant to RTT
423 inflations such as transient congestion. The unit is seconds.
426 tcp_moderate_rcvbuf - BOOLEAN
427 If set, TCP performs receive buffer auto-tuning, attempting to
428 automatically size the buffer (no greater than tcp_rmem[2]) to
429 match the size required by the path for full throughput. Enabled by
432 tcp_mtu_probing - INTEGER
433 Controls TCP Packetization-Layer Path MTU Discovery. Takes three
436 1 - Disabled by default, enabled when an ICMP black hole detected
437 2 - Always enabled, use initial MSS of tcp_base_mss.
439 tcp_probe_interval - UNSIGNED INTEGER
440 Controls how often to start TCP Packetization-Layer Path MTU
441 Discovery reprobe. The default is reprobing every 10 minutes as
444 tcp_probe_threshold - INTEGER
445 Controls when TCP Packetization-Layer Path MTU Discovery probing
446 will stop in respect to the width of search range in bytes. Default
449 tcp_no_metrics_save - BOOLEAN
450 By default, TCP saves various connection metrics in the route cache
451 when the connection closes, so that connections established in the
452 near future can use these to set initial conditions. Usually, this
453 increases overall performance, but may sometimes cause performance
454 degradation. If set, TCP will not cache metrics on closing
457 tcp_orphan_retries - INTEGER
458 This value influences the timeout of a locally closed TCP connection,
459 when RTO retransmissions remain unacknowledged.
460 See tcp_retries2 for more details.
462 The default value is 8.
463 If your machine is a loaded WEB server,
464 you should think about lowering this value, such sockets
465 may consume significant resources. Cf. tcp_max_orphans.
467 tcp_recovery - INTEGER
468 This value is a bitmap to enable various experimental loss recovery
471 RACK: 0x1 enables the RACK loss detection for fast detection of lost
472 retransmissions and tail drops. It also subsumes and disables
473 RFC6675 recovery for SACK connections.
474 RACK: 0x2 makes RACK's reordering window static (min_rtt/4).
475 RACK: 0x4 disables RACK's DUPACK threshold heuristic
479 tcp_reordering - INTEGER
480 Initial reordering level of packets in a TCP stream.
481 TCP stack can then dynamically adjust flow reordering level
482 between this initial value and tcp_max_reordering
485 tcp_max_reordering - INTEGER
486 Maximal reordering level of packets in a TCP stream.
487 300 is a fairly conservative value, but you might increase it
488 if paths are using per packet load balancing (like bonding rr mode)
491 tcp_retrans_collapse - BOOLEAN
492 Bug-to-bug compatibility with some broken printers.
493 On retransmit try to send bigger packets to work around bugs in
496 tcp_retries1 - INTEGER
497 This value influences the time, after which TCP decides, that
498 something is wrong due to unacknowledged RTO retransmissions,
499 and reports this suspicion to the network layer.
500 See tcp_retries2 for more details.
502 RFC 1122 recommends at least 3 retransmissions, which is the
505 tcp_retries2 - INTEGER
506 This value influences the timeout of an alive TCP connection,
507 when RTO retransmissions remain unacknowledged.
508 Given a value of N, a hypothetical TCP connection following
509 exponential backoff with an initial RTO of TCP_RTO_MIN would
510 retransmit N times before killing the connection at the (N+1)th RTO.
512 The default value of 15 yields a hypothetical timeout of 924.6
513 seconds and is a lower bound for the effective timeout.
514 TCP will effectively time out at the first RTO which exceeds the
515 hypothetical timeout.
517 RFC 1122 recommends at least 100 seconds for the timeout,
518 which corresponds to a value of at least 8.
520 tcp_rfc1337 - BOOLEAN
521 If set, the TCP stack behaves conforming to RFC1337. If unset,
522 we are not conforming to RFC, but prevent TCP TIME_WAIT
526 tcp_rmem - vector of 3 INTEGERs: min, default, max
527 min: Minimal size of receive buffer used by TCP sockets.
528 It is guaranteed to each TCP socket, even under moderate memory
532 default: initial size of receive buffer used by TCP sockets.
533 This value overrides net.core.rmem_default used by other protocols.
534 Default: 87380 bytes. This value results in window of 65535 with
535 default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
536 less for default tcp_app_win. See below about these variables.
538 max: maximal size of receive buffer allowed for automatically
539 selected receiver buffers for TCP socket. This value does not override
540 net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
541 automatic tuning of that socket's receive buffer size, in which
542 case this value is ignored.
543 Default: between 87380B and 6MB, depending on RAM size.
546 Enable select acknowledgments (SACKS).
548 tcp_comp_sack_delay_ns - LONG INTEGER
549 TCP tries to reduce number of SACK sent, using a timer
550 based on 5% of SRTT, capped by this sysctl, in nano seconds.
551 The default is 1ms, based on TSO autosizing period.
553 Default : 1,000,000 ns (1 ms)
555 tcp_comp_sack_nr - INTEGER
556 Max numer of SACK that can be compressed.
557 Using 0 disables SACK compression.
561 tcp_slow_start_after_idle - BOOLEAN
562 If set, provide RFC2861 behavior and time out the congestion
563 window after an idle period. An idle period is defined at
564 the current RTO. If unset, the congestion window will not
565 be timed out after an idle period.
569 Use the Host requirements interpretation of the TCP urgent pointer field.
570 Most hosts use the older BSD interpretation, so if you turn this on
571 Linux might not communicate correctly with them.
574 tcp_synack_retries - INTEGER
575 Number of times SYNACKs for a passive TCP connection attempt will
576 be retransmitted. Should not be higher than 255. Default value
577 is 5, which corresponds to 31seconds till the last retransmission
578 with the current initial RTO of 1second. With this the final timeout
579 for a passive TCP connection will happen after 63seconds.
581 tcp_syncookies - BOOLEAN
582 Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
583 Send out syncookies when the syn backlog queue of a socket
584 overflows. This is to prevent against the common 'SYN flood attack'
587 Note, that syncookies is fallback facility.
588 It MUST NOT be used to help highly loaded servers to stand
589 against legal connection rate. If you see SYN flood warnings
590 in your logs, but investigation shows that they occur
591 because of overload with legal connections, you should tune
592 another parameters until this warning disappear.
593 See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
595 syncookies seriously violate TCP protocol, do not allow
596 to use TCP extensions, can result in serious degradation
597 of some services (f.e. SMTP relaying), visible not by you,
598 but your clients and relays, contacting you. While you see
599 SYN flood warnings in logs not being really flooded, your server
600 is seriously misconfigured.
602 If you want to test which effects syncookies have to your
603 network connections you can set this knob to 2 to enable
604 unconditionally generation of syncookies.
606 tcp_fastopen - INTEGER
607 Enable TCP Fast Open (RFC7413) to send and accept data in the opening
610 The client support is enabled by flag 0x1 (on by default). The client
611 then must use sendmsg() or sendto() with the MSG_FASTOPEN flag,
612 rather than connect() to send data in SYN.
614 The server support is enabled by flag 0x2 (off by default). Then
615 either enable for all listeners with another flag (0x400) or
616 enable individual listeners via TCP_FASTOPEN socket option with
617 the option value being the length of the syn-data backlog.
619 The values (bitmap) are
620 0x1: (client) enables sending data in the opening SYN on the client.
621 0x2: (server) enables the server support, i.e., allowing data in
622 a SYN packet to be accepted and passed to the
623 application before 3-way handshake finishes.
624 0x4: (client) send data in the opening SYN regardless of cookie
625 availability and without a cookie option.
626 0x200: (server) accept data-in-SYN w/o any cookie option present.
627 0x400: (server) enable all listeners to support Fast Open by
628 default without explicit TCP_FASTOPEN socket option.
632 Note that that additional client or server features are only
633 effective if the basic support (0x1 and 0x2) are enabled respectively.
635 tcp_fastopen_blackhole_timeout_sec - INTEGER
636 Initial time period in second to disable Fastopen on active TCP sockets
637 when a TFO firewall blackhole issue happens.
638 This time period will grow exponentially when more blackhole issues
639 get detected right after Fastopen is re-enabled and will reset to
640 initial value when the blackhole issue goes away.
641 0 to disable the blackhole detection.
642 By default, it is set to 1hr.
644 tcp_syn_retries - INTEGER
645 Number of times initial SYNs for an active TCP connection attempt
646 will be retransmitted. Should not be higher than 127. Default value
647 is 6, which corresponds to 63seconds till the last retransmission
648 with the current initial RTO of 1second. With this the final timeout
649 for an active TCP connection attempt will happen after 127seconds.
651 tcp_timestamps - INTEGER
652 Enable timestamps as defined in RFC1323.
654 1: Enable timestamps as defined in RFC1323 and use random offset for
655 each connection rather than only using the current time.
656 2: Like 1, but without random offsets.
659 tcp_min_tso_segs - INTEGER
660 Minimal number of segments per TSO frame.
661 Since linux-3.12, TCP does an automatic sizing of TSO frames,
662 depending on flow rate, instead of filling 64Kbytes packets.
663 For specific usages, it's possible to force TCP to build big
664 TSO frames. Note that TCP stack might split too big TSO packets
665 if available window is too small.
668 tcp_pacing_ss_ratio - INTEGER
669 sk->sk_pacing_rate is set by TCP stack using a ratio applied
670 to current rate. (current_rate = cwnd * mss / srtt)
671 If TCP is in slow start, tcp_pacing_ss_ratio is applied
672 to let TCP probe for bigger speeds, assuming cwnd can be
673 doubled every other RTT.
676 tcp_pacing_ca_ratio - INTEGER
677 sk->sk_pacing_rate is set by TCP stack using a ratio applied
678 to current rate. (current_rate = cwnd * mss / srtt)
679 If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio
680 is applied to conservatively probe for bigger throughput.
683 tcp_tso_win_divisor - INTEGER
684 This allows control over what percentage of the congestion window
685 can be consumed by a single TSO frame.
686 The setting of this parameter is a choice between burstiness and
687 building larger TSO frames.
690 tcp_tw_reuse - INTEGER
691 Enable reuse of TIME-WAIT sockets for new connections when it is
692 safe from protocol viewpoint.
695 2 - enable for loopback traffic only
696 It should not be changed without advice/request of technical
700 tcp_window_scaling - BOOLEAN
701 Enable window scaling as defined in RFC1323.
703 tcp_wmem - vector of 3 INTEGERs: min, default, max
704 min: Amount of memory reserved for send buffers for TCP sockets.
705 Each TCP socket has rights to use it due to fact of its birth.
708 default: initial size of send buffer used by TCP sockets. This
709 value overrides net.core.wmem_default used by other protocols.
710 It is usually lower than net.core.wmem_default.
713 max: Maximal amount of memory allowed for automatically tuned
714 send buffers for TCP sockets. This value does not override
715 net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables
716 automatic tuning of that socket's send buffer size, in which case
717 this value is ignored.
718 Default: between 64K and 4MB, depending on RAM size.
720 tcp_notsent_lowat - UNSIGNED INTEGER
721 A TCP socket can control the amount of unsent bytes in its write queue,
722 thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll()
723 reports POLLOUT events if the amount of unsent bytes is below a per
724 socket value, and if the write queue is not full. sendmsg() will
725 also not add new buffers if the limit is hit.
727 This global variable controls the amount of unsent data for
728 sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change
729 to the global variable has immediate effect.
731 Default: UINT_MAX (0xFFFFFFFF)
733 tcp_workaround_signed_windows - BOOLEAN
734 If set, assume no receipt of a window scaling option means the
735 remote TCP is broken and treats the window as a signed quantity.
736 If unset, assume the remote TCP is not broken even if we do
737 not receive a window scaling option from them.
740 tcp_thin_linear_timeouts - BOOLEAN
741 Enable dynamic triggering of linear timeouts for thin streams.
742 If set, a check is performed upon retransmission by timeout to
743 determine if the stream is thin (less than 4 packets in flight).
744 As long as the stream is found to be thin, up to 6 linear
745 timeouts may be performed before exponential backoff mode is
746 initiated. This improves retransmission latency for
747 non-aggressive thin streams, often found to be time-dependent.
748 For more information on thin streams, see
749 Documentation/networking/tcp-thin.txt
752 tcp_limit_output_bytes - INTEGER
753 Controls TCP Small Queue limit per tcp socket.
754 TCP bulk sender tends to increase packets in flight until it
755 gets losses notifications. With SNDBUF autotuning, this can
756 result in a large amount of packets queued on the local machine
757 (e.g.: qdiscs, CPU backlog, or device) hurting latency of other
758 flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes
759 limits the number of bytes on qdisc or device to reduce artificial
760 RTT/cwnd and reduce bufferbloat.
763 tcp_challenge_ack_limit - INTEGER
764 Limits number of Challenge ACK sent per second, as recommended
765 in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
770 udp_l3mdev_accept - BOOLEAN
771 Enabling this option allows a "global" bound socket to work
772 across L3 master domains (e.g., VRFs) with packets capable of
773 being received regardless of the L3 domain in which they
774 originated. Only valid when the kernel was compiled with
775 CONFIG_NET_L3_MASTER_DEV.
777 udp_mem - vector of 3 INTEGERs: min, pressure, max
778 Number of pages allowed for queueing by all UDP sockets.
780 min: Below this number of pages UDP is not bothered about its
781 memory appetite. When amount of memory allocated by UDP exceeds
782 this number, UDP starts to moderate memory usage.
784 pressure: This value was introduced to follow format of tcp_mem.
786 max: Number of pages allowed for queueing by all UDP sockets.
788 Default is calculated at boot time from amount of available memory.
790 udp_rmem_min - INTEGER
791 Minimal size of receive buffer used by UDP sockets in moderation.
792 Each UDP socket is able to use the size for receiving data, even if
793 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
796 udp_wmem_min - INTEGER
797 Minimal size of send buffer used by UDP sockets in moderation.
798 Each UDP socket is able to use the size for sending data, even if
799 total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
804 cipso_cache_enable - BOOLEAN
805 If set, enable additions to and lookups from the CIPSO label mapping
806 cache. If unset, additions are ignored and lookups always result in a
807 miss. However, regardless of the setting the cache is still
808 invalidated when required when means you can safely toggle this on and
809 off and the cache will always be "safe".
812 cipso_cache_bucket_size - INTEGER
813 The CIPSO label cache consists of a fixed size hash table with each
814 hash bucket containing a number of cache entries. This variable limits
815 the number of entries in each hash bucket; the larger the value the
816 more CIPSO label mappings that can be cached. When the number of
817 entries in a given hash bucket reaches this limit adding new entries
818 causes the oldest entry in the bucket to be removed to make room.
821 cipso_rbm_optfmt - BOOLEAN
822 Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
823 the CIPSO draft specification (see Documentation/netlabel for details).
824 This means that when set the CIPSO tag will be padded with empty
825 categories in order to make the packet data 32-bit aligned.
828 cipso_rbm_structvalid - BOOLEAN
829 If set, do a very strict check of the CIPSO option when
830 ip_options_compile() is called. If unset, relax the checks done during
831 ip_options_compile(). Either way is "safe" as errors are caught else
832 where in the CIPSO processing code but setting this to 0 (False) should
833 result in less work (i.e. it should be faster) but could cause problems
834 with other implementations that require strict checking.
839 ip_local_port_range - 2 INTEGERS
840 Defines the local port range that is used by TCP and UDP to
841 choose the local port. The first number is the first, the
842 second the last local port number.
843 If possible, it is better these numbers have different parity.
844 (one even and one odd values)
845 The default values are 32768 and 60999 respectively.
847 ip_local_reserved_ports - list of comma separated ranges
848 Specify the ports which are reserved for known third-party
849 applications. These ports will not be used by automatic port
850 assignments (e.g. when calling connect() or bind() with port
851 number 0). Explicit port allocation behavior is unchanged.
853 The format used for both input and output is a comma separated
854 list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
855 10). Writing to the file will clear all previously reserved
856 ports and update the current list with the one given in the
859 Note that ip_local_port_range and ip_local_reserved_ports
860 settings are independent and both are considered by the kernel
861 when determining which ports are available for automatic port
864 You can reserve ports which are not in the current
865 ip_local_port_range, e.g.:
867 $ cat /proc/sys/net/ipv4/ip_local_port_range
869 $ cat /proc/sys/net/ipv4/ip_local_reserved_ports
872 although this is redundant. However such a setting is useful
873 if later the port range is changed to a value that will
874 include the reserved ports.
878 ip_unprivileged_port_start - INTEGER
879 This is a per-namespace sysctl. It defines the first
880 unprivileged port in the network namespace. Privileged ports
881 require root or CAP_NET_BIND_SERVICE in order to bind to them.
882 To disable all privileged ports, set this to 0. It may not
883 overlap with the ip_local_reserved_ports range.
887 ip_nonlocal_bind - BOOLEAN
888 If set, allows processes to bind() to non-local IP addresses,
889 which can be quite useful - but may break some applications.
893 If set non-zero, enables support for dynamic addresses.
894 If set to a non-zero value larger than 1, a kernel log
895 message will be printed when dynamic address rewriting
899 ip_early_demux - BOOLEAN
900 Optimize input packet processing down to one demux for
901 certain kinds of local sockets. Currently we only do this
902 for established TCP and connected UDP sockets.
904 It may add an additional cost for pure routing workloads that
905 reduces overall throughput, in such case you should disable it.
908 tcp_early_demux - BOOLEAN
909 Enable early demux for established TCP sockets.
912 udp_early_demux - BOOLEAN
913 Enable early demux for connected UDP sockets. Disable this if
914 your system could experience more unconnected load.
917 icmp_echo_ignore_all - BOOLEAN
918 If set non-zero, then the kernel will ignore all ICMP ECHO
922 icmp_echo_ignore_broadcasts - BOOLEAN
923 If set non-zero, then the kernel will ignore all ICMP ECHO and
924 TIMESTAMP requests sent to it via broadcast/multicast.
927 icmp_ratelimit - INTEGER
928 Limit the maximal rates for sending ICMP packets whose type matches
929 icmp_ratemask (see below) to specific targets.
930 0 to disable any limiting,
931 otherwise the minimal space between responses in milliseconds.
932 Note that another sysctl, icmp_msgs_per_sec limits the number
933 of ICMP packets sent on all targets.
936 icmp_msgs_per_sec - INTEGER
937 Limit maximal number of ICMP packets sent per second from this host.
938 Only messages whose type matches icmp_ratemask (see below) are
939 controlled by this limit.
942 icmp_msgs_burst - INTEGER
943 icmp_msgs_per_sec controls number of ICMP packets sent per second,
944 while icmp_msgs_burst controls the burst size of these packets.
947 icmp_ratemask - INTEGER
948 Mask made of ICMP types for which rates are being limited.
949 Significant bits: IHGFEDCBA9876543210
950 Default mask: 0000001100000011000 (6168)
952 Bit definitions (see include/linux/icmp.h):
954 3 Destination Unreachable *
959 C Parameter Problem *
964 H Address Mask Request
967 * These are rate limited by default (see default mask above)
969 icmp_ignore_bogus_error_responses - BOOLEAN
970 Some routers violate RFC1122 by sending bogus responses to broadcast
971 frames. Such violations are normally logged via a kernel warning.
972 If this is set to TRUE, the kernel will not give such warnings, which
973 will avoid log file clutter.
976 icmp_errors_use_inbound_ifaddr - BOOLEAN
978 If zero, icmp error messages are sent with the primary address of
979 the exiting interface.
981 If non-zero, the message will be sent with the primary address of
982 the interface that received the packet that caused the icmp error.
983 This is the behaviour network many administrators will expect from
984 a router. And it can make debugging complicated network layouts
987 Note that if no primary address exists for the interface selected,
988 then the primary address of the first non-loopback interface that
989 has one will be used regardless of this setting.
993 igmp_max_memberships - INTEGER
994 Change the maximum number of multicast groups we can subscribe to.
997 Theoretical maximum value is bounded by having to send a membership
998 report in a single datagram (i.e. the report can't span multiple
999 datagrams, or risk confusing the switch and leaving groups you don't
1002 The number of supported groups 'M' is bounded by the number of group
1003 report entries you can fit into a single datagram of 65535 bytes.
1005 M = 65536-sizeof (ip header)/(sizeof(Group record))
1007 Group records are variable length, with a minimum of 12 bytes.
1008 So net.ipv4.igmp_max_memberships should not be set higher than:
1010 (65536-24) / 12 = 5459
1012 The value 5459 assumes no IP header options, so in practice
1013 this number may be lower.
1015 igmp_max_msf - INTEGER
1016 Maximum number of addresses allowed in the source filter list for a
1021 Controls the IGMP query robustness variable (see RFC2236 8.1).
1022 Default: 2 (as specified by RFC2236 8.1)
1023 Minimum: 1 (as specified by RFC6636 4.5)
1025 force_igmp_version - INTEGER
1026 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback
1027 allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier
1028 Present timer expires.
1029 1 - Enforce to use IGMP version 1. Will also reply IGMPv1 report if
1030 receive IGMPv2/v3 query.
1031 2 - Enforce to use IGMP version 2. Will fallback to IGMPv1 if receive
1032 IGMPv1 query message. Will reply report if receive IGMPv3 query.
1033 3 - Enforce to use IGMP version 3. The same react with default 0.
1035 Note: this is not the same with force_mld_version because IGMPv3 RFC3376
1036 Security Considerations does not have clear description that we could
1037 ignore other version messages completely as MLDv2 RFC3810. So make
1038 this value as default 0 is recommended.
1040 conf/interface/* changes special settings per interface (where
1041 "interface" is the name of your network interface)
1043 conf/all/* is special, changes the settings for all interfaces
1045 log_martians - BOOLEAN
1046 Log packets with impossible addresses to kernel log.
1047 log_martians for the interface will be enabled if at least one of
1048 conf/{all,interface}/log_martians is set to TRUE,
1049 it will be disabled otherwise
1051 accept_redirects - BOOLEAN
1052 Accept ICMP redirect messages.
1053 accept_redirects for the interface will be enabled if:
1054 - both conf/{all,interface}/accept_redirects are TRUE in the case
1055 forwarding for the interface is enabled
1057 - at least one of conf/{all,interface}/accept_redirects is TRUE in the
1058 case forwarding for the interface is disabled
1059 accept_redirects for the interface will be disabled otherwise
1063 forwarding - BOOLEAN
1064 Enable IP forwarding on this interface. This controls whether packets
1065 received _on_ this interface can be forwarded.
1067 mc_forwarding - BOOLEAN
1068 Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
1069 and a multicast routing daemon is required.
1070 conf/all/mc_forwarding must also be set to TRUE to enable multicast
1071 routing for the interface
1074 Integer value used to differentiate the devices by the medium they
1075 are attached to. Two devices can have different id values when
1076 the broadcast packets are received only on one of them.
1077 The default value 0 means that the device is the only interface
1078 to its medium, value of -1 means that medium is not known.
1080 Currently, it is used to change the proxy_arp behavior:
1081 the proxy_arp feature is enabled for packets forwarded between
1082 two devices attached to different media.
1086 proxy_arp for the interface will be enabled if at least one of
1087 conf/{all,interface}/proxy_arp is set to TRUE,
1088 it will be disabled otherwise
1090 proxy_arp_pvlan - BOOLEAN
1091 Private VLAN proxy arp.
1092 Basically allow proxy arp replies back to the same interface
1093 (from which the ARP request/solicitation was received).
1095 This is done to support (ethernet) switch features, like RFC
1096 3069, where the individual ports are NOT allowed to
1097 communicate with each other, but they are allowed to talk to
1098 the upstream router. As described in RFC 3069, it is possible
1099 to allow these hosts to communicate through the upstream
1100 router by proxy_arp'ing. Don't need to be used together with
1103 This technology is known by different names:
1104 In RFC 3069 it is called VLAN Aggregation.
1105 Cisco and Allied Telesyn call it Private VLAN.
1106 Hewlett-Packard call it Source-Port filtering or port-isolation.
1107 Ericsson call it MAC-Forced Forwarding (RFC Draft).
1109 shared_media - BOOLEAN
1110 Send(router) or accept(host) RFC1620 shared media redirects.
1111 Overrides secure_redirects.
1112 shared_media for the interface will be enabled if at least one of
1113 conf/{all,interface}/shared_media is set to TRUE,
1114 it will be disabled otherwise
1117 secure_redirects - BOOLEAN
1118 Accept ICMP redirect messages only to gateways listed in the
1119 interface's current gateway list. Even if disabled, RFC1122 redirect
1121 Overridden by shared_media.
1122 secure_redirects for the interface will be enabled if at least one of
1123 conf/{all,interface}/secure_redirects is set to TRUE,
1124 it will be disabled otherwise
1127 send_redirects - BOOLEAN
1128 Send redirects, if router.
1129 send_redirects for the interface will be enabled if at least one of
1130 conf/{all,interface}/send_redirects is set to TRUE,
1131 it will be disabled otherwise
1134 bootp_relay - BOOLEAN
1135 Accept packets with source address 0.b.c.d destined
1136 not to this host as local ones. It is supposed, that
1137 BOOTP relay daemon will catch and forward such packets.
1138 conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
1141 Not Implemented Yet.
1143 accept_source_route - BOOLEAN
1144 Accept packets with SRR option.
1145 conf/all/accept_source_route must also be set to TRUE to accept packets
1146 with SRR option on the interface
1147 default TRUE (router)
1150 accept_local - BOOLEAN
1151 Accept packets with local source addresses. In combination with
1152 suitable routing, this can be used to direct packets between two
1153 local interfaces over the wire and have them accepted properly.
1156 route_localnet - BOOLEAN
1157 Do not consider loopback addresses as martian source or destination
1158 while routing. This enables the use of 127/8 for local routing purposes.
1162 0 - No source validation.
1163 1 - Strict mode as defined in RFC3704 Strict Reverse Path
1164 Each incoming packet is tested against the FIB and if the interface
1165 is not the best reverse path the packet check will fail.
1166 By default failed packets are discarded.
1167 2 - Loose mode as defined in RFC3704 Loose Reverse Path
1168 Each incoming packet's source address is also tested against the FIB
1169 and if the source address is not reachable via any interface
1170 the packet check will fail.
1172 Current recommended practice in RFC3704 is to enable strict mode
1173 to prevent IP spoofing from DDos attacks. If using asymmetric routing
1174 or other complicated routing, then loose mode is recommended.
1176 The max value from conf/{all,interface}/rp_filter is used
1177 when doing source validation on the {interface}.
1179 Default value is 0. Note that some distributions enable it
1182 arp_filter - BOOLEAN
1183 1 - Allows you to have multiple network interfaces on the same
1184 subnet, and have the ARPs for each interface be answered
1185 based on whether or not the kernel would route a packet from
1186 the ARP'd IP out that interface (therefore you must use source
1187 based routing for this to work). In other words it allows control
1188 of which cards (usually 1) will respond to an arp request.
1190 0 - (default) The kernel can respond to arp requests with addresses
1191 from other interfaces. This may seem wrong but it usually makes
1192 sense, because it increases the chance of successful communication.
1193 IP addresses are owned by the complete host on Linux, not by
1194 particular interfaces. Only for more complex setups like load-
1195 balancing, does this behaviour cause problems.
1197 arp_filter for the interface will be enabled if at least one of
1198 conf/{all,interface}/arp_filter is set to TRUE,
1199 it will be disabled otherwise
1201 arp_announce - INTEGER
1202 Define different restriction levels for announcing the local
1203 source IP address from IP packets in ARP requests sent on
1205 0 - (default) Use any local address, configured on any interface
1206 1 - Try to avoid local addresses that are not in the target's
1207 subnet for this interface. This mode is useful when target
1208 hosts reachable via this interface require the source IP
1209 address in ARP requests to be part of their logical network
1210 configured on the receiving interface. When we generate the
1211 request we will check all our subnets that include the
1212 target IP and will preserve the source address if it is from
1213 such subnet. If there is no such subnet we select source
1214 address according to the rules for level 2.
1215 2 - Always use the best local address for this target.
1216 In this mode we ignore the source address in the IP packet
1217 and try to select local address that we prefer for talks with
1218 the target host. Such local address is selected by looking
1219 for primary IP addresses on all our subnets on the outgoing
1220 interface that include the target IP address. If no suitable
1221 local address is found we select the first local address
1222 we have on the outgoing interface or on all other interfaces,
1223 with the hope we will receive reply for our request and
1224 even sometimes no matter the source IP address we announce.
1226 The max value from conf/{all,interface}/arp_announce is used.
1228 Increasing the restriction level gives more chance for
1229 receiving answer from the resolved target while decreasing
1230 the level announces more valid sender's information.
1232 arp_ignore - INTEGER
1233 Define different modes for sending replies in response to
1234 received ARP requests that resolve local target IP addresses:
1235 0 - (default): reply for any local target IP address, configured
1237 1 - reply only if the target IP address is local address
1238 configured on the incoming interface
1239 2 - reply only if the target IP address is local address
1240 configured on the incoming interface and both with the
1241 sender's IP address are part from same subnet on this interface
1242 3 - do not reply for local addresses configured with scope host,
1243 only resolutions for global and link addresses are replied
1245 8 - do not reply for all local addresses
1247 The max value from conf/{all,interface}/arp_ignore is used
1248 when ARP request is received on the {interface}
1250 arp_notify - BOOLEAN
1251 Define mode for notification of address and device changes.
1252 0 - (default): do nothing
1253 1 - Generate gratuitous arp requests when device is brought up
1254 or hardware address changes.
1256 arp_accept - BOOLEAN
1257 Define behavior for gratuitous ARP frames who's IP is not
1258 already present in the ARP table:
1259 0 - don't create new entries in the ARP table
1260 1 - create new entries in the ARP table
1262 Both replies and requests type gratuitous arp will trigger the
1263 ARP table to be updated, if this setting is on.
1265 If the ARP table already contains the IP address of the
1266 gratuitous arp frame, the arp table will be updated regardless
1267 if this setting is on or off.
1269 mcast_solicit - INTEGER
1270 The maximum number of multicast probes in INCOMPLETE state,
1271 when the associated hardware address is unknown. Defaults
1274 ucast_solicit - INTEGER
1275 The maximum number of unicast probes in PROBE state, when
1276 the hardware address is being reconfirmed. Defaults to 3.
1278 app_solicit - INTEGER
1279 The maximum number of probes to send to the user space ARP daemon
1280 via netlink before dropping back to multicast probes (see
1281 mcast_resolicit). Defaults to 0.
1283 mcast_resolicit - INTEGER
1284 The maximum number of multicast probes after unicast and
1285 app probes in PROBE state. Defaults to 0.
1287 disable_policy - BOOLEAN
1288 Disable IPSEC policy (SPD) for this interface
1290 disable_xfrm - BOOLEAN
1291 Disable IPSEC encryption on this interface, whatever the policy
1293 igmpv2_unsolicited_report_interval - INTEGER
1294 The interval in milliseconds in which the next unsolicited
1295 IGMPv1 or IGMPv2 report retransmit will take place.
1296 Default: 10000 (10 seconds)
1298 igmpv3_unsolicited_report_interval - INTEGER
1299 The interval in milliseconds in which the next unsolicited
1300 IGMPv3 report retransmit will take place.
1301 Default: 1000 (1 seconds)
1303 promote_secondaries - BOOLEAN
1304 When a primary IP address is removed from this interface
1305 promote a corresponding secondary IP address instead of
1306 removing all the corresponding secondary IP addresses.
1308 drop_unicast_in_l2_multicast - BOOLEAN
1309 Drop any unicast IP packets that are received in link-layer
1310 multicast (or broadcast) frames.
1311 This behavior (for multicast) is actually a SHOULD in RFC
1312 1122, but is disabled by default for compatibility reasons.
1315 drop_gratuitous_arp - BOOLEAN
1316 Drop all gratuitous ARP frames, for example if there's a known
1317 good ARP proxy on the network and such frames need not be used
1318 (or in the case of 802.11, must not be used to prevent attacks.)
1323 Allows you to write a number, which can be used as required.
1326 xfrm4_gc_thresh - INTEGER
1327 The threshold at which we will start garbage collecting for IPv4
1328 destination cache entries. At twice this value the system will
1329 refuse new allocations.
1331 igmp_link_local_mcast_reports - BOOLEAN
1332 Enable IGMP reports for link local multicast groups in the
1337 kuznet@ms2.inr.ac.ru
1343 delon.nicolas@wanadoo.fr
1348 /proc/sys/net/ipv6/* Variables:
1350 IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
1351 apply to IPv6 [XXX?].
1353 bindv6only - BOOLEAN
1354 Default value for IPV6_V6ONLY socket option,
1355 which restricts use of the IPv6 socket to IPv6 communication
1357 TRUE: disable IPv4-mapped address feature
1358 FALSE: enable IPv4-mapped address feature
1360 Default: FALSE (as specified in RFC3493)
1362 flowlabel_consistency - BOOLEAN
1363 Protect the consistency (and unicity) of flow label.
1364 You have to disable it to use IPV6_FL_F_REFLECT flag on the
1370 auto_flowlabels - INTEGER
1371 Automatically generate flow labels based on a flow hash of the
1372 packet. This allows intermediate devices, such as routers, to
1373 identify packet flows for mechanisms like Equal Cost Multipath
1374 Routing (see RFC 6438).
1375 0: automatic flow labels are completely disabled
1376 1: automatic flow labels are enabled by default, they can be
1377 disabled on a per socket basis using the IPV6_AUTOFLOWLABEL
1379 2: automatic flow labels are allowed, they may be enabled on a
1380 per socket basis using the IPV6_AUTOFLOWLABEL socket option
1381 3: automatic flow labels are enabled and enforced, they cannot
1382 be disabled by the socket option
1385 flowlabel_state_ranges - BOOLEAN
1386 Split the flow label number space into two ranges. 0-0x7FFFF is
1387 reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF
1388 is reserved for stateless flow labels as described in RFC6437.
1393 flowlabel_reflect - BOOLEAN
1394 Automatically reflect the flow label. Needed for Path MTU
1395 Discovery to work with Equal Cost Multipath Routing in anycast
1396 environments. See RFC 7690 and:
1397 https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01
1402 fib_multipath_hash_policy - INTEGER
1403 Controls which hash policy to use for multipath routes.
1404 Default: 0 (Layer 3)
1406 0 - Layer 3 (source and destination addresses plus flow label)
1407 1 - Layer 4 (standard 5-tuple)
1409 anycast_src_echo_reply - BOOLEAN
1410 Controls the use of anycast addresses as source addresses for ICMPv6
1416 idgen_delay - INTEGER
1417 Controls the delay in seconds after which time to retry
1418 privacy stable address generation if a DAD conflict is
1420 Default: 1 (as specified in RFC7217)
1422 idgen_retries - INTEGER
1423 Controls the number of retries to generate a stable privacy
1424 address if a DAD conflict is detected.
1425 Default: 3 (as specified in RFC7217)
1428 Controls the MLD query robustness variable (see RFC3810 9.1).
1429 Default: 2 (as specified by RFC3810 9.1)
1430 Minimum: 1 (as specified by RFC6636 4.5)
1432 max_dst_opts_number - INTEGER
1433 Maximum number of non-padding TLVs allowed in a Destination
1434 options extension header. If this value is less than zero
1435 then unknown options are disallowed and the number of known
1436 TLVs allowed is the absolute value of this number.
1439 max_hbh_opts_number - INTEGER
1440 Maximum number of non-padding TLVs allowed in a Hop-by-Hop
1441 options extension header. If this value is less than zero
1442 then unknown options are disallowed and the number of known
1443 TLVs allowed is the absolute value of this number.
1446 max_dst_opts_length - INTEGER
1447 Maximum length allowed for a Destination options extension
1449 Default: INT_MAX (unlimited)
1451 max_hbh_length - INTEGER
1452 Maximum length allowed for a Hop-by-Hop options extension
1454 Default: INT_MAX (unlimited)
1456 skip_notify_on_dev_down - BOOLEAN
1457 Controls whether an RTM_DELROUTE message is generated for routes
1458 removed when a device is taken down or deleted. IPv4 does not
1459 generate this message; IPv6 does by default. Setting this sysctl
1460 to true skips the message, making IPv4 and IPv6 on par in relying
1461 on userspace caches to track link events and evict routes.
1462 Default: false (generate message)
1466 ip6frag_high_thresh - INTEGER
1467 Maximum memory used to reassemble IPv6 fragments. When
1468 ip6frag_high_thresh bytes of memory is allocated for this purpose,
1469 the fragment handler will toss packets until ip6frag_low_thresh
1472 ip6frag_low_thresh - INTEGER
1473 See ip6frag_high_thresh
1475 ip6frag_time - INTEGER
1476 Time in seconds to keep an IPv6 fragment in memory.
1478 IPv6 Segment Routing:
1480 seg6_flowlabel - INTEGER
1481 Controls the behaviour of computing the flowlabel of outer
1482 IPv6 header in case of SR T.encaps
1484 -1 set flowlabel to zero.
1485 0 copy flowlabel from Inner packet in case of Inner IPv6
1486 (Set flowlabel to 0 in case IPv4/L2)
1487 1 Compute the flowlabel using seg6_make_flowlabel()
1492 Change the interface-specific default settings.
1496 Change all the interface-specific settings.
1498 [XXX: Other special features than forwarding?]
1500 conf/all/forwarding - BOOLEAN
1501 Enable global IPv6 forwarding between all interfaces.
1503 IPv4 and IPv6 work differently here; e.g. netfilter must be used
1504 to control which interfaces may forward packets and which not.
1506 This also sets all interfaces' Host/Router setting
1507 'forwarding' to the specified value. See below for details.
1509 This referred to as global forwarding.
1514 fwmark_reflect - BOOLEAN
1515 Controls the fwmark of kernel-generated IPv6 reply packets that are not
1516 associated with a socket for example, TCP RSTs or ICMPv6 echo replies).
1517 If unset, these packets have a fwmark of zero. If set, they have the
1518 fwmark of the packet they are replying to.
1522 Change special settings per interface.
1524 The functional behaviour for certain settings is different
1525 depending on whether local forwarding is enabled or not.
1528 Accept Router Advertisements; autoconfigure using them.
1530 It also determines whether or not to transmit Router
1531 Solicitations. If and only if the functional setting is to
1532 accept Router Advertisements, Router Solicitations will be
1535 Possible values are:
1536 0 Do not accept Router Advertisements.
1537 1 Accept Router Advertisements if forwarding is disabled.
1538 2 Overrule forwarding behaviour. Accept Router Advertisements
1539 even if forwarding is enabled.
1541 Functional default: enabled if local forwarding is disabled.
1542 disabled if local forwarding is enabled.
1544 accept_ra_defrtr - BOOLEAN
1545 Learn default router in Router Advertisement.
1547 Functional default: enabled if accept_ra is enabled.
1548 disabled if accept_ra is disabled.
1550 accept_ra_from_local - BOOLEAN
1551 Accept RA with source-address that is found on local machine
1552 if the RA is otherwise proper and able to be accepted.
1553 Default is to NOT accept these as it may be an un-intended
1557 enabled if accept_ra_from_local is enabled
1558 on a specific interface.
1559 disabled if accept_ra_from_local is disabled
1560 on a specific interface.
1562 accept_ra_min_hop_limit - INTEGER
1563 Minimum hop limit Information in Router Advertisement.
1565 Hop limit Information in Router Advertisement less than this
1566 variable shall be ignored.
1570 accept_ra_pinfo - BOOLEAN
1571 Learn Prefix Information in Router Advertisement.
1573 Functional default: enabled if accept_ra is enabled.
1574 disabled if accept_ra is disabled.
1576 accept_ra_rt_info_min_plen - INTEGER
1577 Minimum prefix length of Route Information in RA.
1579 Route Information w/ prefix smaller than this variable shall
1582 Functional default: 0 if accept_ra_rtr_pref is enabled.
1583 -1 if accept_ra_rtr_pref is disabled.
1585 accept_ra_rt_info_max_plen - INTEGER
1586 Maximum prefix length of Route Information in RA.
1588 Route Information w/ prefix larger than this variable shall
1591 Functional default: 0 if accept_ra_rtr_pref is enabled.
1592 -1 if accept_ra_rtr_pref is disabled.
1594 accept_ra_rtr_pref - BOOLEAN
1595 Accept Router Preference in RA.
1597 Functional default: enabled if accept_ra is enabled.
1598 disabled if accept_ra is disabled.
1600 accept_ra_mtu - BOOLEAN
1601 Apply the MTU value specified in RA option 5 (RFC4861). If
1602 disabled, the MTU specified in the RA will be ignored.
1604 Functional default: enabled if accept_ra is enabled.
1605 disabled if accept_ra is disabled.
1607 accept_redirects - BOOLEAN
1610 Functional default: enabled if local forwarding is disabled.
1611 disabled if local forwarding is enabled.
1613 accept_source_route - INTEGER
1614 Accept source routing (routing extension header).
1616 >= 0: Accept only routing header type 2.
1617 < 0: Do not accept routing header.
1622 Autoconfigure addresses using Prefix Information in Router
1625 Functional default: enabled if accept_ra_pinfo is enabled.
1626 disabled if accept_ra_pinfo is disabled.
1628 dad_transmits - INTEGER
1629 The amount of Duplicate Address Detection probes to send.
1632 forwarding - INTEGER
1633 Configure interface-specific Host/Router behaviour.
1635 Note: It is recommended to have the same setting on all
1636 interfaces; mixed router/host scenarios are rather uncommon.
1638 Possible values are:
1639 0 Forwarding disabled
1640 1 Forwarding enabled
1644 By default, Host behaviour is assumed. This means:
1646 1. IsRouter flag is not set in Neighbour Advertisements.
1647 2. If accept_ra is TRUE (default), transmit Router
1649 3. If accept_ra is TRUE (default), accept Router
1650 Advertisements (and do autoconfiguration).
1651 4. If accept_redirects is TRUE (default), accept Redirects.
1655 If local forwarding is enabled, Router behaviour is assumed.
1656 This means exactly the reverse from the above:
1658 1. IsRouter flag is set in Neighbour Advertisements.
1659 2. Router Solicitations are not sent unless accept_ra is 2.
1660 3. Router Advertisements are ignored unless accept_ra is 2.
1661 4. Redirects are ignored.
1663 Default: 0 (disabled) if global forwarding is disabled (default),
1664 otherwise 1 (enabled).
1667 Default Hop Limit to set.
1671 Default Maximum Transfer Unit
1672 Default: 1280 (IPv6 required minimum)
1674 ip_nonlocal_bind - BOOLEAN
1675 If set, allows processes to bind() to non-local IPv6 addresses,
1676 which can be quite useful - but may break some applications.
1679 router_probe_interval - INTEGER
1680 Minimum interval (in seconds) between Router Probing described
1685 router_solicitation_delay - INTEGER
1686 Number of seconds to wait after interface is brought up
1687 before sending Router Solicitations.
1690 router_solicitation_interval - INTEGER
1691 Number of seconds to wait between Router Solicitations.
1694 router_solicitations - INTEGER
1695 Number of Router Solicitations to send until assuming no
1696 routers are present.
1699 use_oif_addrs_only - BOOLEAN
1700 When enabled, the candidate source addresses for destinations
1701 routed via this interface are restricted to the set of addresses
1702 configured on this interface (vis. RFC 6724, section 4).
1706 use_tempaddr - INTEGER
1707 Preference for Privacy Extensions (RFC3041).
1708 <= 0 : disable Privacy Extensions
1709 == 1 : enable Privacy Extensions, but prefer public
1710 addresses over temporary addresses.
1711 > 1 : enable Privacy Extensions and prefer temporary
1712 addresses over public addresses.
1713 Default: 0 (for most devices)
1714 -1 (for point-to-point devices and loopback devices)
1716 temp_valid_lft - INTEGER
1717 valid lifetime (in seconds) for temporary addresses.
1718 Default: 604800 (7 days)
1720 temp_prefered_lft - INTEGER
1721 Preferred lifetime (in seconds) for temporary addresses.
1722 Default: 86400 (1 day)
1724 keep_addr_on_down - INTEGER
1725 Keep all IPv6 addresses on an interface down event. If set static
1726 global addresses with no expiration time are not flushed.
1731 Default: 0 (addresses are removed)
1733 max_desync_factor - INTEGER
1734 Maximum value for DESYNC_FACTOR, which is a random value
1735 that ensures that clients don't synchronize with each
1736 other and generate new addresses at exactly the same time.
1737 value is in seconds.
1740 regen_max_retry - INTEGER
1741 Number of attempts before give up attempting to generate
1742 valid temporary addresses.
1745 max_addresses - INTEGER
1746 Maximum number of autoconfigured addresses per interface. Setting
1747 to zero disables the limitation. It is not recommended to set this
1748 value too large (or to zero) because it would be an easy way to
1749 crash the kernel by allowing too many addresses to be created.
1752 disable_ipv6 - BOOLEAN
1753 Disable IPv6 operation. If accept_dad is set to 2, this value
1754 will be dynamically set to TRUE if DAD fails for the link-local
1756 Default: FALSE (enable IPv6 operation)
1758 When this value is changed from 1 to 0 (IPv6 is being enabled),
1759 it will dynamically create a link-local address on the given
1760 interface and start Duplicate Address Detection, if necessary.
1762 When this value is changed from 0 to 1 (IPv6 is being disabled),
1763 it will dynamically delete all addresses and routes on the given
1764 interface. From now on it will not possible to add addresses/routes
1765 to the selected interface.
1767 accept_dad - INTEGER
1768 Whether to accept DAD (Duplicate Address Detection).
1770 1: Enable DAD (default)
1771 2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
1772 link-local address has been found.
1774 DAD operation and mode on a given interface will be selected according
1775 to the maximum value of conf/{all,interface}/accept_dad.
1777 force_tllao - BOOLEAN
1778 Enable sending the target link-layer address option even when
1779 responding to a unicast neighbor solicitation.
1782 Quoting from RFC 2461, section 4.4, Target link-layer address:
1784 "The option MUST be included for multicast solicitations in order to
1785 avoid infinite Neighbor Solicitation "recursion" when the peer node
1786 does not have a cache entry to return a Neighbor Advertisements
1787 message. When responding to unicast solicitations, the option can be
1788 omitted since the sender of the solicitation has the correct link-
1789 layer address; otherwise it would not have be able to send the unicast
1790 solicitation in the first place. However, including the link-layer
1791 address in this case adds little overhead and eliminates a potential
1792 race condition where the sender deletes the cached link-layer address
1793 prior to receiving a response to a previous solicitation."
1795 ndisc_notify - BOOLEAN
1796 Define mode for notification of address and device changes.
1797 0 - (default): do nothing
1798 1 - Generate unsolicited neighbour advertisements when device is brought
1799 up or hardware address changes.
1801 ndisc_tclass - INTEGER
1802 The IPv6 Traffic Class to use by default when sending IPv6 Neighbor
1803 Discovery (Router Solicitation, Router Advertisement, Neighbor
1804 Solicitation, Neighbor Advertisement, Redirect) messages.
1805 These 8 bits can be interpreted as 6 high order bits holding the DSCP
1806 value and 2 low order bits representing ECN (which you probably want
1810 mldv1_unsolicited_report_interval - INTEGER
1811 The interval in milliseconds in which the next unsolicited
1812 MLDv1 report retransmit will take place.
1813 Default: 10000 (10 seconds)
1815 mldv2_unsolicited_report_interval - INTEGER
1816 The interval in milliseconds in which the next unsolicited
1817 MLDv2 report retransmit will take place.
1818 Default: 1000 (1 second)
1820 force_mld_version - INTEGER
1821 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed
1822 1 - Enforce to use MLD version 1
1823 2 - Enforce to use MLD version 2
1825 suppress_frag_ndisc - INTEGER
1826 Control RFC 6980 (Security Implications of IPv6 Fragmentation
1827 with IPv6 Neighbor Discovery) behavior:
1828 1 - (default) discard fragmented neighbor discovery packets
1829 0 - allow fragmented neighbor discovery packets
1831 optimistic_dad - BOOLEAN
1832 Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
1833 0: disabled (default)
1836 Optimistic Duplicate Address Detection for the interface will be enabled
1837 if at least one of conf/{all,interface}/optimistic_dad is set to 1,
1838 it will be disabled otherwise.
1840 use_optimistic - BOOLEAN
1841 If enabled, do not classify optimistic addresses as deprecated during
1842 source address selection. Preferred addresses will still be chosen
1843 before optimistic addresses, subject to other ranking in the source
1844 address selection algorithm.
1845 0: disabled (default)
1848 This will be enabled if at least one of
1849 conf/{all,interface}/use_optimistic is set to 1, disabled otherwise.
1851 stable_secret - IPv6 address
1852 This IPv6 address will be used as a secret to generate IPv6
1853 addresses for link-local addresses and autoconfigured
1854 ones. All addresses generated after setting this secret will
1855 be stable privacy ones by default. This can be changed via the
1856 addrgenmode ip-link. conf/default/stable_secret is used as the
1857 secret for the namespace, the interface specific ones can
1858 overwrite that. Writes to conf/all/stable_secret are refused.
1860 It is recommended to generate this secret during installation
1861 of a system and keep it stable after that.
1863 By default the stable secret is unset.
1865 addr_gen_mode - INTEGER
1866 Defines how link-local and autoconf addresses are generated.
1868 0: generate address based on EUI64 (default)
1869 1: do no generate a link-local address, use EUI64 for addresses generated
1871 2: generate stable privacy addresses, using the secret from
1872 stable_secret (RFC7217)
1873 3: generate stable privacy addresses, using a random secret if unset
1875 drop_unicast_in_l2_multicast - BOOLEAN
1876 Drop any unicast IPv6 packets that are received in link-layer
1877 multicast (or broadcast) frames.
1879 By default this is turned off.
1881 drop_unsolicited_na - BOOLEAN
1882 Drop all unsolicited neighbor advertisements, for example if there's
1883 a known good NA proxy on the network and such frames need not be used
1884 (or in the case of 802.11, must not be used to prevent attacks.)
1886 By default this is turned off.
1888 enhanced_dad - BOOLEAN
1889 Include a nonce option in the IPv6 neighbor solicitation messages used for
1890 duplicate address detection per RFC7527. A received DAD NS will only signal
1891 a duplicate address if the nonce is different. This avoids any false
1892 detection of duplicates due to loopback of the NS messages that we send.
1893 The nonce option will be sent on an interface unless both of
1894 conf/{all,interface}/enhanced_dad are set to FALSE.
1899 Limit the maximal rates for sending ICMPv6 packets.
1900 0 to disable any limiting,
1901 otherwise the minimal space between responses in milliseconds.
1904 echo_ignore_all - BOOLEAN
1905 If set non-zero, then the kernel will ignore all ICMP ECHO
1906 requests sent to it over the IPv6 protocol.
1909 xfrm6_gc_thresh - INTEGER
1910 The threshold at which we will start garbage collecting for IPv6
1911 destination cache entries. At twice this value the system will
1912 refuse new allocations.
1916 Pekka Savola <pekkas@netcore.fi>
1917 YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
1920 /proc/sys/net/bridge/* Variables:
1922 bridge-nf-call-arptables - BOOLEAN
1923 1 : pass bridged ARP traffic to arptables' FORWARD chain.
1927 bridge-nf-call-iptables - BOOLEAN
1928 1 : pass bridged IPv4 traffic to iptables' chains.
1932 bridge-nf-call-ip6tables - BOOLEAN
1933 1 : pass bridged IPv6 traffic to ip6tables' chains.
1937 bridge-nf-filter-vlan-tagged - BOOLEAN
1938 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
1942 bridge-nf-filter-pppoe-tagged - BOOLEAN
1943 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
1947 bridge-nf-pass-vlan-input-dev - BOOLEAN
1948 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
1949 interface on the bridge and set the netfilter input device to the vlan.
1950 This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT
1951 target work with vlan-on-top-of-bridge interfaces. When no matching
1952 vlan interface is found, or this switch is off, the input device is
1953 set to the bridge interface.
1954 0: disable bridge netfilter vlan interface lookup.
1957 proc/sys/net/sctp/* Variables:
1959 addip_enable - BOOLEAN
1960 Enable or disable extension of Dynamic Address Reconfiguration
1961 (ADD-IP) functionality specified in RFC5061. This extension provides
1962 the ability to dynamically add and remove new addresses for the SCTP
1965 1: Enable extension.
1967 0: Disable extension.
1972 Enable or disable pf (pf is short for potentially failed) state. A value
1973 of pf_retrans > path_max_retrans also disables pf state. That is, one of
1974 both pf_enable and pf_retrans > path_max_retrans can disable pf state.
1975 Since pf_retrans and path_max_retrans can be changed by userspace
1976 application, sometimes user expects to disable pf state by the value of
1977 pf_retrans > path_max_retrans, but occasionally the value of pf_retrans
1978 or path_max_retrans is changed by the user application, this pf state is
1979 enabled. As such, it is necessary to add this to dynamically enable
1980 and disable pf state. See:
1981 https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for
1990 addip_noauth_enable - BOOLEAN
1991 Dynamic Address Reconfiguration (ADD-IP) requires the use of
1992 authentication to protect the operations of adding or removing new
1993 addresses. This requirement is mandated so that unauthorized hosts
1994 would not be able to hijack associations. However, older
1995 implementations may not have implemented this requirement while
1996 allowing the ADD-IP extension. For reasons of interoperability,
1997 we provide this variable to control the enforcement of the
1998 authentication requirement.
2000 1: Allow ADD-IP extension to be used without authentication. This
2001 should only be set in a closed environment for interoperability
2002 with older implementations.
2004 0: Enforce the authentication requirement
2008 auth_enable - BOOLEAN
2009 Enable or disable Authenticated Chunks extension. This extension
2010 provides the ability to send and receive authenticated chunks and is
2011 required for secure operation of Dynamic Address Reconfiguration
2014 1: Enable this extension.
2015 0: Disable this extension.
2019 prsctp_enable - BOOLEAN
2020 Enable or disable the Partial Reliability extension (RFC3758) which
2021 is used to notify peers that a given DATA should no longer be expected.
2029 The limit of the number of new packets that can be initially sent. It
2030 controls how bursty the generated traffic can be.
2034 association_max_retrans - INTEGER
2035 Set the maximum number for retransmissions that an association can
2036 attempt deciding that the remote end is unreachable. If this value
2037 is exceeded, the association is terminated.
2041 max_init_retransmits - INTEGER
2042 The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
2043 that an association will attempt before declaring the destination
2044 unreachable and terminating.
2048 path_max_retrans - INTEGER
2049 The maximum number of retransmissions that will be attempted on a given
2050 path. Once this threshold is exceeded, the path is considered
2051 unreachable, and new traffic will use a different path when the
2052 association is multihomed.
2056 pf_retrans - INTEGER
2057 The number of retransmissions that will be attempted on a given path
2058 before traffic is redirected to an alternate transport (should one
2059 exist). Note this is distinct from path_max_retrans, as a path that
2060 passes the pf_retrans threshold can still be used. Its only
2061 deprioritized when a transmission path is selected by the stack. This
2062 setting is primarily used to enable fast failover mechanisms without
2063 having to reduce path_max_retrans to a very low value. See:
2064 http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
2065 for details. Note also that a value of pf_retrans > path_max_retrans
2066 disables this feature. Since both pf_retrans and path_max_retrans can
2067 be changed by userspace application, a variable pf_enable is used to
2072 rto_initial - INTEGER
2073 The initial round trip timeout value in milliseconds that will be used
2074 in calculating round trip times. This is the initial time interval
2075 for retransmissions.
2080 The maximum value (in milliseconds) of the round trip timeout. This
2081 is the largest time interval that can elapse between retransmissions.
2086 The minimum value (in milliseconds) of the round trip timeout. This
2087 is the smallest time interval the can elapse between retransmissions.
2091 hb_interval - INTEGER
2092 The interval (in milliseconds) between HEARTBEAT chunks. These chunks
2093 are sent at the specified interval on idle paths to probe the state of
2094 a given path between 2 associations.
2098 sack_timeout - INTEGER
2099 The amount of time (in milliseconds) that the implementation will wait
2104 valid_cookie_life - INTEGER
2105 The default lifetime of the SCTP cookie (in milliseconds). The cookie
2106 is used during association establishment.
2110 cookie_preserve_enable - BOOLEAN
2111 Enable or disable the ability to extend the lifetime of the SCTP cookie
2112 that is used during the establishment phase of SCTP association
2114 1: Enable cookie lifetime extension.
2119 cookie_hmac_alg - STRING
2120 Select the hmac algorithm used when generating the cookie value sent by
2121 a listening sctp socket to a connecting client in the INIT-ACK chunk.
2126 Ability to assign md5 or sha1 as the selected alg is predicated on the
2127 configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
2128 CONFIG_CRYPTO_SHA1).
2130 Default: Dependent on configuration. MD5 if available, else SHA1 if
2131 available, else none.
2133 rcvbuf_policy - INTEGER
2134 Determines if the receive buffer is attributed to the socket or to
2135 association. SCTP supports the capability to create multiple
2136 associations on a single socket. When using this capability, it is
2137 possible that a single stalled association that's buffering a lot
2138 of data may block other associations from delivering their data by
2139 consuming all of the receive buffer space. To work around this,
2140 the rcvbuf_policy could be set to attribute the receiver buffer space
2141 to each association instead of the socket. This prevents the described
2144 1: rcvbuf space is per association
2145 0: rcvbuf space is per socket
2149 sndbuf_policy - INTEGER
2150 Similar to rcvbuf_policy above, this applies to send buffer space.
2152 1: Send buffer is tracked per association
2153 0: Send buffer is tracked per socket.
2157 sctp_mem - vector of 3 INTEGERs: min, pressure, max
2158 Number of pages allowed for queueing by all SCTP sockets.
2160 min: Below this number of pages SCTP is not bothered about its
2161 memory appetite. When amount of memory allocated by SCTP exceeds
2162 this number, SCTP starts to moderate memory usage.
2164 pressure: This value was introduced to follow format of tcp_mem.
2166 max: Number of pages allowed for queueing by all SCTP sockets.
2168 Default is calculated at boot time from amount of available memory.
2170 sctp_rmem - vector of 3 INTEGERs: min, default, max
2171 Only the first value ("min") is used, "default" and "max" are
2174 min: Minimal size of receive buffer used by SCTP socket.
2175 It is guaranteed to each SCTP socket (but not association) even
2176 under moderate memory pressure.
2180 sctp_wmem - vector of 3 INTEGERs: min, default, max
2181 Currently this tunable has no effect.
2183 addr_scope_policy - INTEGER
2184 Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
2186 0 - Disable IPv4 address scoping
2187 1 - Enable IPv4 address scoping
2188 2 - Follow draft but allow IPv4 private addresses
2189 3 - Follow draft but allow IPv4 link local addresses
2194 /proc/sys/net/core/*
2195 Please see: Documentation/sysctl/net.txt for descriptions of these entries.
2198 /proc/sys/net/unix/*
2199 max_dgram_qlen - INTEGER
2200 The maximum length of dgram socket receive queue