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Based on kernel version 4.3. Page generated on 2015-11-02 12:50 EST.

1	/proc/sys/net/ipv4/* Variables:
2	
3	ip_forward - BOOLEAN
4		0 - disabled (default)
5		not 0 - enabled
6	
7		Forward Packets between interfaces.
8	
9		This variable is special, its change resets all configuration
10		parameters to their default state (RFC1122 for hosts, RFC1812
11		for routers)
12	
13	ip_default_ttl - INTEGER
14		Default value of TTL field (Time To Live) for outgoing (but not
15		forwarded) IP packets. Should be between 1 and 255 inclusive.
16		Default: 64 (as recommended by RFC1700)
17	
18	ip_no_pmtu_disc - INTEGER
19		Disable Path MTU Discovery. If enabled in mode 1 and a
20		fragmentation-required ICMP is received, the PMTU to this
21		destination will be set to min_pmtu (see below). You will need
22		to raise min_pmtu to the smallest interface MTU on your system
23		manually if you want to avoid locally generated fragments.
24	
25		In mode 2 incoming Path MTU Discovery messages will be
26		discarded. Outgoing frames are handled the same as in mode 1,
27		implicitly setting IP_PMTUDISC_DONT on every created socket.
28	
29		Mode 3 is a hardend pmtu discover mode. The kernel will only
30		accept fragmentation-needed errors if the underlying protocol
31		can verify them besides a plain socket lookup. Current
32		protocols for which pmtu events will be honored are TCP, SCTP
33		and DCCP as they verify e.g. the sequence number or the
34		association. This mode should not be enabled globally but is
35		only intended to secure e.g. name servers in namespaces where
36		TCP path mtu must still work but path MTU information of other
37		protocols should be discarded. If enabled globally this mode
38		could break other protocols.
39	
40		Possible values: 0-3
41		Default: FALSE
42	
43	min_pmtu - INTEGER
44		default 552 - minimum discovered Path MTU
45	
46	ip_forward_use_pmtu - BOOLEAN
47		By default we don't trust protocol path MTUs while forwarding
48		because they could be easily forged and can lead to unwanted
49		fragmentation by the router.
50		You only need to enable this if you have user-space software
51		which tries to discover path mtus by itself and depends on the
52		kernel honoring this information. This is normally not the
53		case.
54		Default: 0 (disabled)
55		Possible values:
56		0 - disabled
57		1 - enabled
58	
59	fwmark_reflect - BOOLEAN
60		Controls the fwmark of kernel-generated IPv4 reply packets that are not
61		associated with a socket for example, TCP RSTs or ICMP echo replies).
62		If unset, these packets have a fwmark of zero. If set, they have the
63		fwmark of the packet they are replying to.
64		Default: 0
65	
66	route/max_size - INTEGER
67		Maximum number of routes allowed in the kernel.  Increase
68		this when using large numbers of interfaces and/or routes.
69		From linux kernel 3.6 onwards, this is deprecated for ipv4
70		as route cache is no longer used.
71	
72	neigh/default/gc_thresh1 - INTEGER
73		Minimum number of entries to keep.  Garbage collector will not
74		purge entries if there are fewer than this number.
75		Default: 128
76	
77	neigh/default/gc_thresh2 - INTEGER
78		Threshold when garbage collector becomes more aggressive about
79		purging entries. Entries older than 5 seconds will be cleared
80		when over this number.
81		Default: 512
82	
83	neigh/default/gc_thresh3 - INTEGER
84		Maximum number of neighbor entries allowed.  Increase this
85		when using large numbers of interfaces and when communicating
86		with large numbers of directly-connected peers.
87		Default: 1024
88	
89	neigh/default/unres_qlen_bytes - INTEGER
90		The maximum number of bytes which may be used by packets
91		queued for each	unresolved address by other network layers.
92		(added in linux 3.3)
93		Setting negative value is meaningless and will return error.
94		Default: 65536 Bytes(64KB)
95	
96	neigh/default/unres_qlen - INTEGER
97		The maximum number of packets which may be queued for each
98		unresolved address by other network layers.
99		(deprecated in linux 3.3) : use unres_qlen_bytes instead.
100		Prior to linux 3.3, the default value is 3 which may cause
101		unexpected packet loss. The current default value is calculated
102		according to default value of unres_qlen_bytes and true size of
103		packet.
104		Default: 31
105	
106	mtu_expires - INTEGER
107		Time, in seconds, that cached PMTU information is kept.
108	
109	min_adv_mss - INTEGER
110		The advertised MSS depends on the first hop route MTU, but will
111		never be lower than this setting.
112	
113	IP Fragmentation:
114	
115	ipfrag_high_thresh - INTEGER
116		Maximum memory used to reassemble IP fragments. When
117		ipfrag_high_thresh bytes of memory is allocated for this purpose,
118		the fragment handler will toss packets until ipfrag_low_thresh
119		is reached. This also serves as a maximum limit to namespaces
120		different from the initial one.
121	
122	ipfrag_low_thresh - INTEGER
123		Maximum memory used to reassemble IP fragments before the kernel
124		begins to remove incomplete fragment queues to free up resources.
125		The kernel still accepts new fragments for defragmentation.
126	
127	ipfrag_time - INTEGER
128		Time in seconds to keep an IP fragment in memory.
129	
130	ipfrag_max_dist - INTEGER
131		ipfrag_max_dist is a non-negative integer value which defines the
132		maximum "disorder" which is allowed among fragments which share a
133		common IP source address. Note that reordering of packets is
134		not unusual, but if a large number of fragments arrive from a source
135		IP address while a particular fragment queue remains incomplete, it
136		probably indicates that one or more fragments belonging to that queue
137		have been lost. When ipfrag_max_dist is positive, an additional check
138		is done on fragments before they are added to a reassembly queue - if
139		ipfrag_max_dist (or more) fragments have arrived from a particular IP
140		address between additions to any IP fragment queue using that source
141		address, it's presumed that one or more fragments in the queue are
142		lost. The existing fragment queue will be dropped, and a new one
143		started. An ipfrag_max_dist value of zero disables this check.
144	
145		Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
146		result in unnecessarily dropping fragment queues when normal
147		reordering of packets occurs, which could lead to poor application
148		performance. Using a very large value, e.g. 50000, increases the
149		likelihood of incorrectly reassembling IP fragments that originate
150		from different IP datagrams, which could result in data corruption.
151		Default: 64
152	
153	INET peer storage:
154	
155	inet_peer_threshold - INTEGER
156		The approximate size of the storage.  Starting from this threshold
157		entries will be thrown aggressively.  This threshold also determines
158		entries' time-to-live and time intervals between garbage collection
159		passes.  More entries, less time-to-live, less GC interval.
160	
161	inet_peer_minttl - INTEGER
162		Minimum time-to-live of entries.  Should be enough to cover fragment
163		time-to-live on the reassembling side.  This minimum time-to-live  is
164		guaranteed if the pool size is less than inet_peer_threshold.
165		Measured in seconds.
166	
167	inet_peer_maxttl - INTEGER
168		Maximum time-to-live of entries.  Unused entries will expire after
169		this period of time if there is no memory pressure on the pool (i.e.
170		when the number of entries in the pool is very small).
171		Measured in seconds.
172	
173	TCP variables:
174	
175	somaxconn - INTEGER
176		Limit of socket listen() backlog, known in userspace as SOMAXCONN.
177		Defaults to 128.  See also tcp_max_syn_backlog for additional tuning
178		for TCP sockets.
179	
180	tcp_abort_on_overflow - BOOLEAN
181		If listening service is too slow to accept new connections,
182		reset them. Default state is FALSE. It means that if overflow
183		occurred due to a burst, connection will recover. Enable this
184		option _only_ if you are really sure that listening daemon
185		cannot be tuned to accept connections faster. Enabling this
186		option can harm clients of your server.
187	
188	tcp_adv_win_scale - INTEGER
189		Count buffering overhead as bytes/2^tcp_adv_win_scale
190		(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
191		if it is <= 0.
192		Possible values are [-31, 31], inclusive.
193		Default: 1
194	
195	tcp_allowed_congestion_control - STRING
196		Show/set the congestion control choices available to non-privileged
197		processes. The list is a subset of those listed in
198		tcp_available_congestion_control.
199		Default is "reno" and the default setting (tcp_congestion_control).
200	
201	tcp_app_win - INTEGER
202		Reserve max(window/2^tcp_app_win, mss) of window for application
203		buffer. Value 0 is special, it means that nothing is reserved.
204		Default: 31
205	
206	tcp_autocorking - BOOLEAN
207		Enable TCP auto corking :
208		When applications do consecutive small write()/sendmsg() system calls,
209		we try to coalesce these small writes as much as possible, to lower
210		total amount of sent packets. This is done if at least one prior
211		packet for the flow is waiting in Qdisc queues or device transmit
212		queue. Applications can still use TCP_CORK for optimal behavior
213		when they know how/when to uncork their sockets.
214		Default : 1
215	
216	tcp_available_congestion_control - STRING
217		Shows the available congestion control choices that are registered.
218		More congestion control algorithms may be available as modules,
219		but not loaded.
220	
221	tcp_base_mss - INTEGER
222		The initial value of search_low to be used by the packetization layer
223		Path MTU discovery (MTU probing).  If MTU probing is enabled,
224		this is the initial MSS used by the connection.
225	
226	tcp_congestion_control - STRING
227		Set the congestion control algorithm to be used for new
228		connections. The algorithm "reno" is always available, but
229		additional choices may be available based on kernel configuration.
230		Default is set as part of kernel configuration.
231		For passive connections, the listener congestion control choice
232		is inherited.
233		[see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
234	
235	tcp_dsack - BOOLEAN
236		Allows TCP to send "duplicate" SACKs.
237	
238	tcp_early_retrans - INTEGER
239		Enable Early Retransmit (ER), per RFC 5827. ER lowers the threshold
240		for triggering fast retransmit when the amount of outstanding data is
241		small and when no previously unsent data can be transmitted (such
242		that limited transmit could be used). Also controls the use of
243		Tail loss probe (TLP) that converts RTOs occurring due to tail
244		losses into fast recovery (draft-dukkipati-tcpm-tcp-loss-probe-01).
245		Possible values:
246			0 disables ER
247			1 enables ER
248			2 enables ER but delays fast recovery and fast retransmit
249			  by a fourth of RTT. This mitigates connection falsely
250			  recovers when network has a small degree of reordering
251			  (less than 3 packets).
252			3 enables delayed ER and TLP.
253			4 enables TLP only.
254		Default: 3
255	
256	tcp_ecn - INTEGER
257		Control use of Explicit Congestion Notification (ECN) by TCP.
258		ECN is used only when both ends of the TCP connection indicate
259		support for it.  This feature is useful in avoiding losses due
260		to congestion by allowing supporting routers to signal
261		congestion before having to drop packets.
262		Possible values are:
263			0 Disable ECN.  Neither initiate nor accept ECN.
264			1 Enable ECN when requested by incoming connections and
265			  also request ECN on outgoing connection attempts.
266			2 Enable ECN when requested by incoming connections
267			  but do not request ECN on outgoing connections.
268		Default: 2
269	
270	tcp_ecn_fallback - BOOLEAN
271		If the kernel detects that ECN connection misbehaves, enable fall
272		back to non-ECN. Currently, this knob implements the fallback
273		from RFC3168, section 6.1.1.1., but we reserve that in future,
274		additional detection mechanisms could be implemented under this
275		knob. The value	is not used, if tcp_ecn or per route (or congestion
276		control) ECN settings are disabled.
277		Default: 1 (fallback enabled)
278	
279	tcp_fack - BOOLEAN
280		Enable FACK congestion avoidance and fast retransmission.
281		The value is not used, if tcp_sack is not enabled.
282	
283	tcp_fin_timeout - INTEGER
284		The length of time an orphaned (no longer referenced by any
285		application) connection will remain in the FIN_WAIT_2 state
286		before it is aborted at the local end.  While a perfectly
287		valid "receive only" state for an un-orphaned connection, an
288		orphaned connection in FIN_WAIT_2 state could otherwise wait
289		forever for the remote to close its end of the connection.
290		Cf. tcp_max_orphans
291		Default: 60 seconds
292	
293	tcp_frto - INTEGER
294		Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
295		F-RTO is an enhanced recovery algorithm for TCP retransmission
296		timeouts.  It is particularly beneficial in networks where the
297		RTT fluctuates (e.g., wireless). F-RTO is sender-side only
298		modification. It does not require any support from the peer.
299	
300		By default it's enabled with a non-zero value. 0 disables F-RTO.
301	
302	tcp_invalid_ratelimit - INTEGER
303		Limit the maximal rate for sending duplicate acknowledgments
304		in response to incoming TCP packets that are for an existing
305		connection but that are invalid due to any of these reasons:
306	
307		  (a) out-of-window sequence number,
308		  (b) out-of-window acknowledgment number, or
309		  (c) PAWS (Protection Against Wrapped Sequence numbers) check failure
310	
311		This can help mitigate simple "ack loop" DoS attacks, wherein
312		a buggy or malicious middlebox or man-in-the-middle can
313		rewrite TCP header fields in manner that causes each endpoint
314		to think that the other is sending invalid TCP segments, thus
315		causing each side to send an unterminating stream of duplicate
316		acknowledgments for invalid segments.
317	
318		Using 0 disables rate-limiting of dupacks in response to
319		invalid segments; otherwise this value specifies the minimal
320		space between sending such dupacks, in milliseconds.
321	
322		Default: 500 (milliseconds).
323	
324	tcp_keepalive_time - INTEGER
325		How often TCP sends out keepalive messages when keepalive is enabled.
326		Default: 2hours.
327	
328	tcp_keepalive_probes - INTEGER
329		How many keepalive probes TCP sends out, until it decides that the
330		connection is broken. Default value: 9.
331	
332	tcp_keepalive_intvl - INTEGER
333		How frequently the probes are send out. Multiplied by
334		tcp_keepalive_probes it is time to kill not responding connection,
335		after probes started. Default value: 75sec i.e. connection
336		will be aborted after ~11 minutes of retries.
337	
338	tcp_low_latency - BOOLEAN
339		If set, the TCP stack makes decisions that prefer lower
340		latency as opposed to higher throughput.  By default, this
341		option is not set meaning that higher throughput is preferred.
342		An example of an application where this default should be
343		changed would be a Beowulf compute cluster.
344		Default: 0
345	
346	tcp_max_orphans - INTEGER
347		Maximal number of TCP sockets not attached to any user file handle,
348		held by system.	If this number is exceeded orphaned connections are
349		reset immediately and warning is printed. This limit exists
350		only to prevent simple DoS attacks, you _must_ not rely on this
351		or lower the limit artificially, but rather increase it
352		(probably, after increasing installed memory),
353		if network conditions require more than default value,
354		and tune network services to linger and kill such states
355		more aggressively. Let me to remind again: each orphan eats
356		up to ~64K of unswappable memory.
357	
358	tcp_max_syn_backlog - INTEGER
359		Maximal number of remembered connection requests, which have not
360		received an acknowledgment from connecting client.
361		The minimal value is 128 for low memory machines, and it will
362		increase in proportion to the memory of machine.
363		If server suffers from overload, try increasing this number.
364	
365	tcp_max_tw_buckets - INTEGER
366		Maximal number of timewait sockets held by system simultaneously.
367		If this number is exceeded time-wait socket is immediately destroyed
368		and warning is printed. This limit exists only to prevent
369		simple DoS attacks, you _must_ not lower the limit artificially,
370		but rather increase it (probably, after increasing installed memory),
371		if network conditions require more than default value.
372	
373	tcp_mem - vector of 3 INTEGERs: min, pressure, max
374		min: below this number of pages TCP is not bothered about its
375		memory appetite.
376	
377		pressure: when amount of memory allocated by TCP exceeds this number
378		of pages, TCP moderates its memory consumption and enters memory
379		pressure mode, which is exited when memory consumption falls
380		under "min".
381	
382		max: number of pages allowed for queueing by all TCP sockets.
383	
384		Defaults are calculated at boot time from amount of available
385		memory.
386	
387	tcp_moderate_rcvbuf - BOOLEAN
388		If set, TCP performs receive buffer auto-tuning, attempting to
389		automatically size the buffer (no greater than tcp_rmem[2]) to
390		match the size required by the path for full throughput.  Enabled by
391		default.
392	
393	tcp_mtu_probing - INTEGER
394		Controls TCP Packetization-Layer Path MTU Discovery.  Takes three
395		values:
396		  0 - Disabled
397		  1 - Disabled by default, enabled when an ICMP black hole detected
398		  2 - Always enabled, use initial MSS of tcp_base_mss.
399	
400	tcp_probe_interval - INTEGER
401		Controls how often to start TCP Packetization-Layer Path MTU
402		Discovery reprobe. The default is reprobing every 10 minutes as
403		per RFC4821.
404	
405	tcp_probe_threshold - INTEGER
406		Controls when TCP Packetization-Layer Path MTU Discovery probing
407		will stop in respect to the width of search range in bytes. Default
408		is 8 bytes.
409	
410	tcp_no_metrics_save - BOOLEAN
411		By default, TCP saves various connection metrics in the route cache
412		when the connection closes, so that connections established in the
413		near future can use these to set initial conditions.  Usually, this
414		increases overall performance, but may sometimes cause performance
415		degradation.  If set, TCP will not cache metrics on closing
416		connections.
417	
418	tcp_orphan_retries - INTEGER
419		This value influences the timeout of a locally closed TCP connection,
420		when RTO retransmissions remain unacknowledged.
421		See tcp_retries2 for more details.
422	
423		The default value is 8.
424		If your machine is a loaded WEB server,
425		you should think about lowering this value, such sockets
426		may consume significant resources. Cf. tcp_max_orphans.
427	
428	tcp_reordering - INTEGER
429		Initial reordering level of packets in a TCP stream.
430		TCP stack can then dynamically adjust flow reordering level
431		between this initial value and tcp_max_reordering
432		Default: 3
433	
434	tcp_max_reordering - INTEGER
435		Maximal reordering level of packets in a TCP stream.
436		300 is a fairly conservative value, but you might increase it
437		if paths are using per packet load balancing (like bonding rr mode)
438		Default: 300
439	
440	tcp_retrans_collapse - BOOLEAN
441		Bug-to-bug compatibility with some broken printers.
442		On retransmit try to send bigger packets to work around bugs in
443		certain TCP stacks.
444	
445	tcp_retries1 - INTEGER
446		This value influences the time, after which TCP decides, that
447		something is wrong due to unacknowledged RTO retransmissions,
448		and reports this suspicion to the network layer.
449		See tcp_retries2 for more details.
450	
451		RFC 1122 recommends at least 3 retransmissions, which is the
452		default.
453	
454	tcp_retries2 - INTEGER
455		This value influences the timeout of an alive TCP connection,
456		when RTO retransmissions remain unacknowledged.
457		Given a value of N, a hypothetical TCP connection following
458		exponential backoff with an initial RTO of TCP_RTO_MIN would
459		retransmit N times before killing the connection at the (N+1)th RTO.
460	
461		The default value of 15 yields a hypothetical timeout of 924.6
462		seconds and is a lower bound for the effective timeout.
463		TCP will effectively time out at the first RTO which exceeds the
464		hypothetical timeout.
465	
466		RFC 1122 recommends at least 100 seconds for the timeout,
467		which corresponds to a value of at least 8.
468	
469	tcp_rfc1337 - BOOLEAN
470		If set, the TCP stack behaves conforming to RFC1337. If unset,
471		we are not conforming to RFC, but prevent TCP TIME_WAIT
472		assassination.
473		Default: 0
474	
475	tcp_rmem - vector of 3 INTEGERs: min, default, max
476		min: Minimal size of receive buffer used by TCP sockets.
477		It is guaranteed to each TCP socket, even under moderate memory
478		pressure.
479		Default: 1 page
480	
481		default: initial size of receive buffer used by TCP sockets.
482		This value overrides net.core.rmem_default used by other protocols.
483		Default: 87380 bytes. This value results in window of 65535 with
484		default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
485		less for default tcp_app_win. See below about these variables.
486	
487		max: maximal size of receive buffer allowed for automatically
488		selected receiver buffers for TCP socket. This value does not override
489		net.core.rmem_max.  Calling setsockopt() with SO_RCVBUF disables
490		automatic tuning of that socket's receive buffer size, in which
491		case this value is ignored.
492		Default: between 87380B and 6MB, depending on RAM size.
493	
494	tcp_sack - BOOLEAN
495		Enable select acknowledgments (SACKS).
496	
497	tcp_slow_start_after_idle - BOOLEAN
498		If set, provide RFC2861 behavior and time out the congestion
499		window after an idle period.  An idle period is defined at
500		the current RTO.  If unset, the congestion window will not
501		be timed out after an idle period.
502		Default: 1
503	
504	tcp_stdurg - BOOLEAN
505		Use the Host requirements interpretation of the TCP urgent pointer field.
506		Most hosts use the older BSD interpretation, so if you turn this on
507		Linux might not communicate correctly with them.
508		Default: FALSE
509	
510	tcp_synack_retries - INTEGER
511		Number of times SYNACKs for a passive TCP connection attempt will
512		be retransmitted. Should not be higher than 255. Default value
513		is 5, which corresponds to 31seconds till the last retransmission
514		with the current initial RTO of 1second. With this the final timeout
515		for a passive TCP connection will happen after 63seconds.
516	
517	tcp_syncookies - BOOLEAN
518		Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
519		Send out syncookies when the syn backlog queue of a socket
520		overflows. This is to prevent against the common 'SYN flood attack'
521		Default: 1
522	
523		Note, that syncookies is fallback facility.
524		It MUST NOT be used to help highly loaded servers to stand
525		against legal connection rate. If you see SYN flood warnings
526		in your logs, but investigation	shows that they occur
527		because of overload with legal connections, you should tune
528		another parameters until this warning disappear.
529		See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
530	
531		syncookies seriously violate TCP protocol, do not allow
532		to use TCP extensions, can result in serious degradation
533		of some services (f.e. SMTP relaying), visible not by you,
534		but your clients and relays, contacting you. While you see
535		SYN flood warnings in logs not being really flooded, your server
536		is seriously misconfigured.
537	
538		If you want to test which effects syncookies have to your
539		network connections you can set this knob to 2 to enable
540		unconditionally generation of syncookies.
541	
542	tcp_fastopen - INTEGER
543		Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
544		in the opening SYN packet. To use this feature, the client application
545		must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than
546		connect() to perform a TCP handshake automatically.
547	
548		The values (bitmap) are
549		1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN.
550		2: Enables TCP Fast Open on the server side, i.e., allowing data in
551		   a SYN packet to be accepted and passed to the application before
552		   3-way hand shake finishes.
553		4: Send data in the opening SYN regardless of cookie availability and
554		   without a cookie option.
555		0x100: Accept SYN data w/o validating the cookie.
556		0x200: Accept data-in-SYN w/o any cookie option present.
557		0x400/0x800: Enable Fast Open on all listeners regardless of the
558		   TCP_FASTOPEN socket option. The two different flags designate two
559		   different ways of setting max_qlen without the TCP_FASTOPEN socket
560		   option.
561	
562		Default: 1
563	
564		Note that the client & server side Fast Open flags (1 and 2
565		respectively) must be also enabled before the rest of flags can take
566		effect.
567	
568		See include/net/tcp.h and the code for more details.
569	
570	tcp_syn_retries - INTEGER
571		Number of times initial SYNs for an active TCP connection attempt
572		will be retransmitted. Should not be higher than 255. Default value
573		is 6, which corresponds to 63seconds till the last retransmission
574		with the current initial RTO of 1second. With this the final timeout
575		for an active TCP connection attempt will happen after 127seconds.
576	
577	tcp_timestamps - BOOLEAN
578		Enable timestamps as defined in RFC1323.
579	
580	tcp_min_tso_segs - INTEGER
581		Minimal number of segments per TSO frame.
582		Since linux-3.12, TCP does an automatic sizing of TSO frames,
583		depending on flow rate, instead of filling 64Kbytes packets.
584		For specific usages, it's possible to force TCP to build big
585		TSO frames. Note that TCP stack might split too big TSO packets
586		if available window is too small.
587		Default: 2
588	
589	tcp_pacing_ss_ratio - INTEGER
590		sk->sk_pacing_rate is set by TCP stack using a ratio applied
591		to current rate. (current_rate = cwnd * mss / srtt)
592		If TCP is in slow start, tcp_pacing_ss_ratio is applied
593		to let TCP probe for bigger speeds, assuming cwnd can be
594		doubled every other RTT.
595		Default: 200
596	
597	tcp_pacing_ca_ratio - INTEGER
598		sk->sk_pacing_rate is set by TCP stack using a ratio applied
599		to current rate. (current_rate = cwnd * mss / srtt)
600		If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio
601		is applied to conservatively probe for bigger throughput.
602		Default: 120
603	
604	tcp_tso_win_divisor - INTEGER
605		This allows control over what percentage of the congestion window
606		can be consumed by a single TSO frame.
607		The setting of this parameter is a choice between burstiness and
608		building larger TSO frames.
609		Default: 3
610	
611	tcp_tw_recycle - BOOLEAN
612		Enable fast recycling TIME-WAIT sockets. Default value is 0.
613		It should not be changed without advice/request of technical
614		experts.
615	
616	tcp_tw_reuse - BOOLEAN
617		Allow to reuse TIME-WAIT sockets for new connections when it is
618		safe from protocol viewpoint. Default value is 0.
619		It should not be changed without advice/request of technical
620		experts.
621	
622	tcp_window_scaling - BOOLEAN
623		Enable window scaling as defined in RFC1323.
624	
625	tcp_wmem - vector of 3 INTEGERs: min, default, max
626		min: Amount of memory reserved for send buffers for TCP sockets.
627		Each TCP socket has rights to use it due to fact of its birth.
628		Default: 1 page
629	
630		default: initial size of send buffer used by TCP sockets.  This
631		value overrides net.core.wmem_default used by other protocols.
632		It is usually lower than net.core.wmem_default.
633		Default: 16K
634	
635		max: Maximal amount of memory allowed for automatically tuned
636		send buffers for TCP sockets. This value does not override
637		net.core.wmem_max.  Calling setsockopt() with SO_SNDBUF disables
638		automatic tuning of that socket's send buffer size, in which case
639		this value is ignored.
640		Default: between 64K and 4MB, depending on RAM size.
641	
642	tcp_notsent_lowat - UNSIGNED INTEGER
643		A TCP socket can control the amount of unsent bytes in its write queue,
644		thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll()
645		reports POLLOUT events if the amount of unsent bytes is below a per
646		socket value, and if the write queue is not full. sendmsg() will
647		also not add new buffers if the limit is hit.
648	
649		This global variable controls the amount of unsent data for
650		sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change
651		to the global variable has immediate effect.
652	
653		Default: UINT_MAX (0xFFFFFFFF)
654	
655	tcp_workaround_signed_windows - BOOLEAN
656		If set, assume no receipt of a window scaling option means the
657		remote TCP is broken and treats the window as a signed quantity.
658		If unset, assume the remote TCP is not broken even if we do
659		not receive a window scaling option from them.
660		Default: 0
661	
662	tcp_thin_linear_timeouts - BOOLEAN
663		Enable dynamic triggering of linear timeouts for thin streams.
664		If set, a check is performed upon retransmission by timeout to
665		determine if the stream is thin (less than 4 packets in flight).
666		As long as the stream is found to be thin, up to 6 linear
667		timeouts may be performed before exponential backoff mode is
668		initiated. This improves retransmission latency for
669		non-aggressive thin streams, often found to be time-dependent.
670		For more information on thin streams, see
671		Documentation/networking/tcp-thin.txt
672		Default: 0
673	
674	tcp_thin_dupack - BOOLEAN
675		Enable dynamic triggering of retransmissions after one dupACK
676		for thin streams. If set, a check is performed upon reception
677		of a dupACK to determine if the stream is thin (less than 4
678		packets in flight). As long as the stream is found to be thin,
679		data is retransmitted on the first received dupACK. This
680		improves retransmission latency for non-aggressive thin
681		streams, often found to be time-dependent.
682		For more information on thin streams, see
683		Documentation/networking/tcp-thin.txt
684		Default: 0
685	
686	tcp_limit_output_bytes - INTEGER
687		Controls TCP Small Queue limit per tcp socket.
688		TCP bulk sender tends to increase packets in flight until it
689		gets losses notifications. With SNDBUF autotuning, this can
690		result in a large amount of packets queued in qdisc/device
691		on the local machine, hurting latency of other flows, for
692		typical pfifo_fast qdiscs.
693		tcp_limit_output_bytes limits the number of bytes on qdisc
694		or device to reduce artificial RTT/cwnd and reduce bufferbloat.
695		Default: 131072
696	
697	tcp_challenge_ack_limit - INTEGER
698		Limits number of Challenge ACK sent per second, as recommended
699		in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
700		Default: 100
701	
702	UDP variables:
703	
704	udp_mem - vector of 3 INTEGERs: min, pressure, max
705		Number of pages allowed for queueing by all UDP sockets.
706	
707		min: Below this number of pages UDP is not bothered about its
708		memory appetite. When amount of memory allocated by UDP exceeds
709		this number, UDP starts to moderate memory usage.
710	
711		pressure: This value was introduced to follow format of tcp_mem.
712	
713		max: Number of pages allowed for queueing by all UDP sockets.
714	
715		Default is calculated at boot time from amount of available memory.
716	
717	udp_rmem_min - INTEGER
718		Minimal size of receive buffer used by UDP sockets in moderation.
719		Each UDP socket is able to use the size for receiving data, even if
720		total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
721		Default: 1 page
722	
723	udp_wmem_min - INTEGER
724		Minimal size of send buffer used by UDP sockets in moderation.
725		Each UDP socket is able to use the size for sending data, even if
726		total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
727		Default: 1 page
728	
729	CIPSOv4 Variables:
730	
731	cipso_cache_enable - BOOLEAN
732		If set, enable additions to and lookups from the CIPSO label mapping
733		cache.  If unset, additions are ignored and lookups always result in a
734		miss.  However, regardless of the setting the cache is still
735		invalidated when required when means you can safely toggle this on and
736		off and the cache will always be "safe".
737		Default: 1
738	
739	cipso_cache_bucket_size - INTEGER
740		The CIPSO label cache consists of a fixed size hash table with each
741		hash bucket containing a number of cache entries.  This variable limits
742		the number of entries in each hash bucket; the larger the value the
743		more CIPSO label mappings that can be cached.  When the number of
744		entries in a given hash bucket reaches this limit adding new entries
745		causes the oldest entry in the bucket to be removed to make room.
746		Default: 10
747	
748	cipso_rbm_optfmt - BOOLEAN
749		Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
750		the CIPSO draft specification (see Documentation/netlabel for details).
751		This means that when set the CIPSO tag will be padded with empty
752		categories in order to make the packet data 32-bit aligned.
753		Default: 0
754	
755	cipso_rbm_structvalid - BOOLEAN
756		If set, do a very strict check of the CIPSO option when
757		ip_options_compile() is called.  If unset, relax the checks done during
758		ip_options_compile().  Either way is "safe" as errors are caught else
759		where in the CIPSO processing code but setting this to 0 (False) should
760		result in less work (i.e. it should be faster) but could cause problems
761		with other implementations that require strict checking.
762		Default: 0
763	
764	IP Variables:
765	
766	ip_local_port_range - 2 INTEGERS
767		Defines the local port range that is used by TCP and UDP to
768		choose the local port. The first number is the first, the
769		second the last local port number.
770		If possible, it is better these numbers have different parity.
771		(one even and one odd values)
772		The default values are 32768 and 60999 respectively.
773	
774	ip_local_reserved_ports - list of comma separated ranges
775		Specify the ports which are reserved for known third-party
776		applications. These ports will not be used by automatic port
777		assignments (e.g. when calling connect() or bind() with port
778		number 0). Explicit port allocation behavior is unchanged.
779	
780		The format used for both input and output is a comma separated
781		list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
782		10). Writing to the file will clear all previously reserved
783		ports and update the current list with the one given in the
784		input.
785	
786		Note that ip_local_port_range and ip_local_reserved_ports
787		settings are independent and both are considered by the kernel
788		when determining which ports are available for automatic port
789		assignments.
790	
791		You can reserve ports which are not in the current
792		ip_local_port_range, e.g.:
793	
794		$ cat /proc/sys/net/ipv4/ip_local_port_range
795		32000	60999
796		$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
797		8080,9148
798	
799		although this is redundant. However such a setting is useful
800		if later the port range is changed to a value that will
801		include the reserved ports.
802	
803		Default: Empty
804	
805	ip_nonlocal_bind - BOOLEAN
806		If set, allows processes to bind() to non-local IP addresses,
807		which can be quite useful - but may break some applications.
808		Default: 0
809	
810	ip_dynaddr - BOOLEAN
811		If set non-zero, enables support for dynamic addresses.
812		If set to a non-zero value larger than 1, a kernel log
813		message will be printed when dynamic address rewriting
814		occurs.
815		Default: 0
816	
817	ip_early_demux - BOOLEAN
818		Optimize input packet processing down to one demux for
819		certain kinds of local sockets.  Currently we only do this
820		for established TCP sockets.
821	
822		It may add an additional cost for pure routing workloads that
823		reduces overall throughput, in such case you should disable it.
824		Default: 1
825	
826	icmp_echo_ignore_all - BOOLEAN
827		If set non-zero, then the kernel will ignore all ICMP ECHO
828		requests sent to it.
829		Default: 0
830	
831	icmp_echo_ignore_broadcasts - BOOLEAN
832		If set non-zero, then the kernel will ignore all ICMP ECHO and
833		TIMESTAMP requests sent to it via broadcast/multicast.
834		Default: 1
835	
836	icmp_ratelimit - INTEGER
837		Limit the maximal rates for sending ICMP packets whose type matches
838		icmp_ratemask (see below) to specific targets.
839		0 to disable any limiting,
840		otherwise the minimal space between responses in milliseconds.
841		Note that another sysctl, icmp_msgs_per_sec limits the number
842		of ICMP packets	sent on all targets.
843		Default: 1000
844	
845	icmp_msgs_per_sec - INTEGER
846		Limit maximal number of ICMP packets sent per second from this host.
847		Only messages whose type matches icmp_ratemask (see below) are
848		controlled by this limit.
849		Default: 1000
850	
851	icmp_msgs_burst - INTEGER
852		icmp_msgs_per_sec controls number of ICMP packets sent per second,
853		while icmp_msgs_burst controls the burst size of these packets.
854		Default: 50
855	
856	icmp_ratemask - INTEGER
857		Mask made of ICMP types for which rates are being limited.
858		Significant bits: IHGFEDCBA9876543210
859		Default mask:     0000001100000011000 (6168)
860	
861		Bit definitions (see include/linux/icmp.h):
862			0 Echo Reply
863			3 Destination Unreachable *
864			4 Source Quench *
865			5 Redirect
866			8 Echo Request
867			B Time Exceeded *
868			C Parameter Problem *
869			D Timestamp Request
870			E Timestamp Reply
871			F Info Request
872			G Info Reply
873			H Address Mask Request
874			I Address Mask Reply
875	
876		* These are rate limited by default (see default mask above)
877	
878	icmp_ignore_bogus_error_responses - BOOLEAN
879		Some routers violate RFC1122 by sending bogus responses to broadcast
880		frames.  Such violations are normally logged via a kernel warning.
881		If this is set to TRUE, the kernel will not give such warnings, which
882		will avoid log file clutter.
883		Default: 1
884	
885	icmp_errors_use_inbound_ifaddr - BOOLEAN
886	
887		If zero, icmp error messages are sent with the primary address of
888		the exiting interface.
889	
890		If non-zero, the message will be sent with the primary address of
891		the interface that received the packet that caused the icmp error.
892		This is the behaviour network many administrators will expect from
893		a router. And it can make debugging complicated network layouts
894		much easier.
895	
896		Note that if no primary address exists for the interface selected,
897		then the primary address of the first non-loopback interface that
898		has one will be used regardless of this setting.
899	
900		Default: 0
901	
902	igmp_max_memberships - INTEGER
903		Change the maximum number of multicast groups we can subscribe to.
904		Default: 20
905	
906		Theoretical maximum value is bounded by having to send a membership
907		report in a single datagram (i.e. the report can't span multiple
908		datagrams, or risk confusing the switch and leaving groups you don't
909		intend to).
910	
911		The number of supported groups 'M' is bounded by the number of group
912		report entries you can fit into a single datagram of 65535 bytes.
913	
914		M = 65536-sizeof (ip header)/(sizeof(Group record))
915	
916		Group records are variable length, with a minimum of 12 bytes.
917		So net.ipv4.igmp_max_memberships should not be set higher than:
918	
919		(65536-24) / 12 = 5459
920	
921		The value 5459 assumes no IP header options, so in practice
922		this number may be lower.
923	
924		conf/interface/*  changes special settings per interface (where
925		"interface" is the name of your network interface)
926	
927		conf/all/*	  is special, changes the settings for all interfaces
928	
929	igmp_qrv - INTEGER
930		 Controls the IGMP query robustness variable (see RFC2236 8.1).
931		 Default: 2 (as specified by RFC2236 8.1)
932		 Minimum: 1 (as specified by RFC6636 4.5)
933	
934	log_martians - BOOLEAN
935		Log packets with impossible addresses to kernel log.
936		log_martians for the interface will be enabled if at least one of
937		conf/{all,interface}/log_martians is set to TRUE,
938		it will be disabled otherwise
939	
940	accept_redirects - BOOLEAN
941		Accept ICMP redirect messages.
942		accept_redirects for the interface will be enabled if:
943		- both conf/{all,interface}/accept_redirects are TRUE in the case
944		  forwarding for the interface is enabled
945		or
946		- at least one of conf/{all,interface}/accept_redirects is TRUE in the
947		  case forwarding for the interface is disabled
948		accept_redirects for the interface will be disabled otherwise
949		default TRUE (host)
950			FALSE (router)
951	
952	forwarding - BOOLEAN
953		Enable IP forwarding on this interface.
954	
955	mc_forwarding - BOOLEAN
956		Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
957		and a multicast routing daemon is required.
958		conf/all/mc_forwarding must also be set to TRUE to enable multicast
959		routing	for the interface
960	
961	medium_id - INTEGER
962		Integer value used to differentiate the devices by the medium they
963		are attached to. Two devices can have different id values when
964		the broadcast packets are received only on one of them.
965		The default value 0 means that the device is the only interface
966		to its medium, value of -1 means that medium is not known.
967	
968		Currently, it is used to change the proxy_arp behavior:
969		the proxy_arp feature is enabled for packets forwarded between
970		two devices attached to different media.
971	
972	proxy_arp - BOOLEAN
973		Do proxy arp.
974		proxy_arp for the interface will be enabled if at least one of
975		conf/{all,interface}/proxy_arp is set to TRUE,
976		it will be disabled otherwise
977	
978	proxy_arp_pvlan - BOOLEAN
979		Private VLAN proxy arp.
980		Basically allow proxy arp replies back to the same interface
981		(from which the ARP request/solicitation was received).
982	
983		This is done to support (ethernet) switch features, like RFC
984		3069, where the individual ports are NOT allowed to
985		communicate with each other, but they are allowed to talk to
986		the upstream router.  As described in RFC 3069, it is possible
987		to allow these hosts to communicate through the upstream
988		router by proxy_arp'ing. Don't need to be used together with
989		proxy_arp.
990	
991		This technology is known by different names:
992		  In RFC 3069 it is called VLAN Aggregation.
993		  Cisco and Allied Telesyn call it Private VLAN.
994		  Hewlett-Packard call it Source-Port filtering or port-isolation.
995		  Ericsson call it MAC-Forced Forwarding (RFC Draft).
996	
997	shared_media - BOOLEAN
998		Send(router) or accept(host) RFC1620 shared media redirects.
999		Overrides ip_secure_redirects.
1000		shared_media for the interface will be enabled if at least one of
1001		conf/{all,interface}/shared_media is set to TRUE,
1002		it will be disabled otherwise
1003		default TRUE
1004	
1005	secure_redirects - BOOLEAN
1006		Accept ICMP redirect messages only for gateways,
1007		listed in default gateway list.
1008		secure_redirects for the interface will be enabled if at least one of
1009		conf/{all,interface}/secure_redirects is set to TRUE,
1010		it will be disabled otherwise
1011		default TRUE
1012	
1013	send_redirects - BOOLEAN
1014		Send redirects, if router.
1015		send_redirects for the interface will be enabled if at least one of
1016		conf/{all,interface}/send_redirects is set to TRUE,
1017		it will be disabled otherwise
1018		Default: TRUE
1019	
1020	bootp_relay - BOOLEAN
1021		Accept packets with source address 0.b.c.d destined
1022		not to this host as local ones. It is supposed, that
1023		BOOTP relay daemon will catch and forward such packets.
1024		conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
1025		for the interface
1026		default FALSE
1027		Not Implemented Yet.
1028	
1029	accept_source_route - BOOLEAN
1030		Accept packets with SRR option.
1031		conf/all/accept_source_route must also be set to TRUE to accept packets
1032		with SRR option on the interface
1033		default TRUE (router)
1034			FALSE (host)
1035	
1036	accept_local - BOOLEAN
1037		Accept packets with local source addresses. In combination with
1038		suitable routing, this can be used to direct packets between two
1039		local interfaces over the wire and have them accepted properly.
1040		default FALSE
1041	
1042	route_localnet - BOOLEAN
1043		Do not consider loopback addresses as martian source or destination
1044		while routing. This enables the use of 127/8 for local routing purposes.
1045		default FALSE
1046	
1047	rp_filter - INTEGER
1048		0 - No source validation.
1049		1 - Strict mode as defined in RFC3704 Strict Reverse Path
1050		    Each incoming packet is tested against the FIB and if the interface
1051		    is not the best reverse path the packet check will fail.
1052		    By default failed packets are discarded.
1053		2 - Loose mode as defined in RFC3704 Loose Reverse Path
1054		    Each incoming packet's source address is also tested against the FIB
1055		    and if the source address is not reachable via any interface
1056		    the packet check will fail.
1057	
1058		Current recommended practice in RFC3704 is to enable strict mode
1059		to prevent IP spoofing from DDos attacks. If using asymmetric routing
1060		or other complicated routing, then loose mode is recommended.
1061	
1062		The max value from conf/{all,interface}/rp_filter is used
1063		when doing source validation on the {interface}.
1064	
1065		Default value is 0. Note that some distributions enable it
1066		in startup scripts.
1067	
1068	arp_filter - BOOLEAN
1069		1 - Allows you to have multiple network interfaces on the same
1070		subnet, and have the ARPs for each interface be answered
1071		based on whether or not the kernel would route a packet from
1072		the ARP'd IP out that interface (therefore you must use source
1073		based routing for this to work). In other words it allows control
1074		of which cards (usually 1) will respond to an arp request.
1075	
1076		0 - (default) The kernel can respond to arp requests with addresses
1077		from other interfaces. This may seem wrong but it usually makes
1078		sense, because it increases the chance of successful communication.
1079		IP addresses are owned by the complete host on Linux, not by
1080		particular interfaces. Only for more complex setups like load-
1081		balancing, does this behaviour cause problems.
1082	
1083		arp_filter for the interface will be enabled if at least one of
1084		conf/{all,interface}/arp_filter is set to TRUE,
1085		it will be disabled otherwise
1086	
1087	arp_announce - INTEGER
1088		Define different restriction levels for announcing the local
1089		source IP address from IP packets in ARP requests sent on
1090		interface:
1091		0 - (default) Use any local address, configured on any interface
1092		1 - Try to avoid local addresses that are not in the target's
1093		subnet for this interface. This mode is useful when target
1094		hosts reachable via this interface require the source IP
1095		address in ARP requests to be part of their logical network
1096		configured on the receiving interface. When we generate the
1097		request we will check all our subnets that include the
1098		target IP and will preserve the source address if it is from
1099		such subnet. If there is no such subnet we select source
1100		address according to the rules for level 2.
1101		2 - Always use the best local address for this target.
1102		In this mode we ignore the source address in the IP packet
1103		and try to select local address that we prefer for talks with
1104		the target host. Such local address is selected by looking
1105		for primary IP addresses on all our subnets on the outgoing
1106		interface that include the target IP address. If no suitable
1107		local address is found we select the first local address
1108		we have on the outgoing interface or on all other interfaces,
1109		with the hope we will receive reply for our request and
1110		even sometimes no matter the source IP address we announce.
1111	
1112		The max value from conf/{all,interface}/arp_announce is used.
1113	
1114		Increasing the restriction level gives more chance for
1115		receiving answer from the resolved target while decreasing
1116		the level announces more valid sender's information.
1117	
1118	arp_ignore - INTEGER
1119		Define different modes for sending replies in response to
1120		received ARP requests that resolve local target IP addresses:
1121		0 - (default): reply for any local target IP address, configured
1122		on any interface
1123		1 - reply only if the target IP address is local address
1124		configured on the incoming interface
1125		2 - reply only if the target IP address is local address
1126		configured on the incoming interface and both with the
1127		sender's IP address are part from same subnet on this interface
1128		3 - do not reply for local addresses configured with scope host,
1129		only resolutions for global and link addresses are replied
1130		4-7 - reserved
1131		8 - do not reply for all local addresses
1132	
1133		The max value from conf/{all,interface}/arp_ignore is used
1134		when ARP request is received on the {interface}
1135	
1136	arp_notify - BOOLEAN
1137		Define mode for notification of address and device changes.
1138		0 - (default): do nothing
1139		1 - Generate gratuitous arp requests when device is brought up
1140		    or hardware address changes.
1141	
1142	arp_accept - BOOLEAN
1143		Define behavior for gratuitous ARP frames who's IP is not
1144		already present in the ARP table:
1145		0 - don't create new entries in the ARP table
1146		1 - create new entries in the ARP table
1147	
1148		Both replies and requests type gratuitous arp will trigger the
1149		ARP table to be updated, if this setting is on.
1150	
1151		If the ARP table already contains the IP address of the
1152		gratuitous arp frame, the arp table will be updated regardless
1153		if this setting is on or off.
1154	
1155	mcast_solicit - INTEGER
1156		The maximum number of multicast probes in INCOMPLETE state,
1157		when the associated hardware address is unknown.  Defaults
1158		to 3.
1159	
1160	ucast_solicit - INTEGER
1161		The maximum number of unicast probes in PROBE state, when
1162		the hardware address is being reconfirmed.  Defaults to 3.
1163	
1164	app_solicit - INTEGER
1165		The maximum number of probes to send to the user space ARP daemon
1166		via netlink before dropping back to multicast probes (see
1167		mcast_resolicit).  Defaults to 0.
1168	
1169	mcast_resolicit - INTEGER
1170		The maximum number of multicast probes after unicast and
1171		app probes in PROBE state.  Defaults to 0.
1172	
1173	disable_policy - BOOLEAN
1174		Disable IPSEC policy (SPD) for this interface
1175	
1176	disable_xfrm - BOOLEAN
1177		Disable IPSEC encryption on this interface, whatever the policy
1178	
1179	igmpv2_unsolicited_report_interval - INTEGER
1180		The interval in milliseconds in which the next unsolicited
1181		IGMPv1 or IGMPv2 report retransmit will take place.
1182		Default: 10000 (10 seconds)
1183	
1184	igmpv3_unsolicited_report_interval - INTEGER
1185		The interval in milliseconds in which the next unsolicited
1186		IGMPv3 report retransmit will take place.
1187		Default: 1000 (1 seconds)
1188	
1189	promote_secondaries - BOOLEAN
1190		When a primary IP address is removed from this interface
1191		promote a corresponding secondary IP address instead of
1192		removing all the corresponding secondary IP addresses.
1193	
1194	
1195	tag - INTEGER
1196		Allows you to write a number, which can be used as required.
1197		Default value is 0.
1198	
1199	xfrm4_gc_thresh - INTEGER
1200		The threshold at which we will start garbage collecting for IPv4
1201		destination cache entries.  At twice this value the system will
1202		refuse new allocations.
1203	
1204	igmp_link_local_mcast_reports - BOOLEAN
1205		Enable IGMP reports for link local multicast groups in the
1206		224.0.0.X range.
1207		Default TRUE
1208	
1209	Alexey Kuznetsov.
1210	kuznet@ms2.inr.ac.ru
1211	
1212	Updated by:
1213	Andi Kleen
1214	ak@muc.de
1215	Nicolas Delon
1216	delon.nicolas@wanadoo.fr
1217	
1218	
1219	
1220	
1221	/proc/sys/net/ipv6/* Variables:
1222	
1223	IPv6 has no global variables such as tcp_*.  tcp_* settings under ipv4/ also
1224	apply to IPv6 [XXX?].
1225	
1226	bindv6only - BOOLEAN
1227		Default value for IPV6_V6ONLY socket option,
1228		which restricts use of the IPv6 socket to IPv6 communication
1229		only.
1230			TRUE: disable IPv4-mapped address feature
1231			FALSE: enable IPv4-mapped address feature
1232	
1233		Default: FALSE (as specified in RFC3493)
1234	
1235	flowlabel_consistency - BOOLEAN
1236		Protect the consistency (and unicity) of flow label.
1237		You have to disable it to use IPV6_FL_F_REFLECT flag on the
1238		flow label manager.
1239		TRUE: enabled
1240		FALSE: disabled
1241		Default: TRUE
1242	
1243	auto_flowlabels - INTEGER
1244		Automatically generate flow labels based on a flow hash of the
1245		packet. This allows intermediate devices, such as routers, to
1246		identify packet flows for mechanisms like Equal Cost Multipath
1247		Routing (see RFC 6438).
1248		0: automatic flow labels are completely disabled
1249		1: automatic flow labels are enabled by default, they can be
1250		   disabled on a per socket basis using the IPV6_AUTOFLOWLABEL
1251		   socket option
1252		2: automatic flow labels are allowed, they may be enabled on a
1253		   per socket basis using the IPV6_AUTOFLOWLABEL socket option
1254		3: automatic flow labels are enabled and enforced, they cannot
1255		   be disabled by the socket option
1256		Default: 1
1257	
1258	flowlabel_state_ranges - BOOLEAN
1259		Split the flow label number space into two ranges. 0-0x7FFFF is
1260		reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF
1261		is reserved for stateless flow labels as described in RFC6437.
1262		TRUE: enabled
1263		FALSE: disabled
1264		Default: true
1265	
1266	anycast_src_echo_reply - BOOLEAN
1267		Controls the use of anycast addresses as source addresses for ICMPv6
1268		echo reply
1269		TRUE:  enabled
1270		FALSE: disabled
1271		Default: FALSE
1272	
1273	idgen_delay - INTEGER
1274		Controls the delay in seconds after which time to retry
1275		privacy stable address generation if a DAD conflict is
1276		detected.
1277		Default: 1 (as specified in RFC7217)
1278	
1279	idgen_retries - INTEGER
1280		Controls the number of retries to generate a stable privacy
1281		address if a DAD conflict is detected.
1282		Default: 3 (as specified in RFC7217)
1283	
1284	mld_qrv - INTEGER
1285		Controls the MLD query robustness variable (see RFC3810 9.1).
1286		Default: 2 (as specified by RFC3810 9.1)
1287		Minimum: 1 (as specified by RFC6636 4.5)
1288	
1289	IPv6 Fragmentation:
1290	
1291	ip6frag_high_thresh - INTEGER
1292		Maximum memory used to reassemble IPv6 fragments. When
1293		ip6frag_high_thresh bytes of memory is allocated for this purpose,
1294		the fragment handler will toss packets until ip6frag_low_thresh
1295		is reached.
1296	
1297	ip6frag_low_thresh - INTEGER
1298		See ip6frag_high_thresh
1299	
1300	ip6frag_time - INTEGER
1301		Time in seconds to keep an IPv6 fragment in memory.
1302	
1303	conf/default/*:
1304		Change the interface-specific default settings.
1305	
1306	
1307	conf/all/*:
1308		Change all the interface-specific settings.
1309	
1310		[XXX:  Other special features than forwarding?]
1311	
1312	conf/all/forwarding - BOOLEAN
1313		Enable global IPv6 forwarding between all interfaces.
1314	
1315		IPv4 and IPv6 work differently here; e.g. netfilter must be used
1316		to control which interfaces may forward packets and which not.
1317	
1318		This also sets all interfaces' Host/Router setting
1319		'forwarding' to the specified value.  See below for details.
1320	
1321		This referred to as global forwarding.
1322	
1323	proxy_ndp - BOOLEAN
1324		Do proxy ndp.
1325	
1326	fwmark_reflect - BOOLEAN
1327		Controls the fwmark of kernel-generated IPv6 reply packets that are not
1328		associated with a socket for example, TCP RSTs or ICMPv6 echo replies).
1329		If unset, these packets have a fwmark of zero. If set, they have the
1330		fwmark of the packet they are replying to.
1331		Default: 0
1332	
1333	conf/interface/*:
1334		Change special settings per interface.
1335	
1336		The functional behaviour for certain settings is different
1337		depending on whether local forwarding is enabled or not.
1338	
1339	accept_ra - INTEGER
1340		Accept Router Advertisements; autoconfigure using them.
1341	
1342		It also determines whether or not to transmit Router
1343		Solicitations. If and only if the functional setting is to
1344		accept Router Advertisements, Router Solicitations will be
1345		transmitted.
1346	
1347		Possible values are:
1348			0 Do not accept Router Advertisements.
1349			1 Accept Router Advertisements if forwarding is disabled.
1350			2 Overrule forwarding behaviour. Accept Router Advertisements
1351			  even if forwarding is enabled.
1352	
1353		Functional default: enabled if local forwarding is disabled.
1354				    disabled if local forwarding is enabled.
1355	
1356	accept_ra_defrtr - BOOLEAN
1357		Learn default router in Router Advertisement.
1358	
1359		Functional default: enabled if accept_ra is enabled.
1360				    disabled if accept_ra is disabled.
1361	
1362	accept_ra_from_local - BOOLEAN
1363		Accept RA with source-address that is found on local machine
1364	        if the RA is otherwise proper and able to be accepted.
1365	        Default is to NOT accept these as it may be an un-intended
1366	        network loop.
1367	
1368		Functional default:
1369	           enabled if accept_ra_from_local is enabled
1370	               on a specific interface.
1371		   disabled if accept_ra_from_local is disabled
1372	               on a specific interface.
1373	
1374	accept_ra_min_hop_limit - INTEGER
1375		Minimum hop limit Information in Router Advertisement.
1376	
1377		Hop limit Information in Router Advertisement less than this
1378		variable shall be ignored.
1379	
1380		Default: 1
1381	
1382	accept_ra_pinfo - BOOLEAN
1383		Learn Prefix Information in Router Advertisement.
1384	
1385		Functional default: enabled if accept_ra is enabled.
1386				    disabled if accept_ra is disabled.
1387	
1388	accept_ra_rt_info_max_plen - INTEGER
1389		Maximum prefix length of Route Information in RA.
1390	
1391		Route Information w/ prefix larger than or equal to this
1392		variable shall be ignored.
1393	
1394		Functional default: 0 if accept_ra_rtr_pref is enabled.
1395				    -1 if accept_ra_rtr_pref is disabled.
1396	
1397	accept_ra_rtr_pref - BOOLEAN
1398		Accept Router Preference in RA.
1399	
1400		Functional default: enabled if accept_ra is enabled.
1401				    disabled if accept_ra is disabled.
1402	
1403	accept_ra_mtu - BOOLEAN
1404		Apply the MTU value specified in RA option 5 (RFC4861). If
1405		disabled, the MTU specified in the RA will be ignored.
1406	
1407		Functional default: enabled if accept_ra is enabled.
1408				    disabled if accept_ra is disabled.
1409	
1410	accept_redirects - BOOLEAN
1411		Accept Redirects.
1412	
1413		Functional default: enabled if local forwarding is disabled.
1414				    disabled if local forwarding is enabled.
1415	
1416	accept_source_route - INTEGER
1417		Accept source routing (routing extension header).
1418	
1419		>= 0: Accept only routing header type 2.
1420		< 0: Do not accept routing header.
1421	
1422		Default: 0
1423	
1424	autoconf - BOOLEAN
1425		Autoconfigure addresses using Prefix Information in Router
1426		Advertisements.
1427	
1428		Functional default: enabled if accept_ra_pinfo is enabled.
1429				    disabled if accept_ra_pinfo is disabled.
1430	
1431	dad_transmits - INTEGER
1432		The amount of Duplicate Address Detection probes to send.
1433		Default: 1
1434	
1435	forwarding - INTEGER
1436		Configure interface-specific Host/Router behaviour.
1437	
1438		Note: It is recommended to have the same setting on all
1439		interfaces; mixed router/host scenarios are rather uncommon.
1440	
1441		Possible values are:
1442			0 Forwarding disabled
1443			1 Forwarding enabled
1444	
1445		FALSE (0):
1446	
1447		By default, Host behaviour is assumed.  This means:
1448	
1449		1. IsRouter flag is not set in Neighbour Advertisements.
1450		2. If accept_ra is TRUE (default), transmit Router
1451		   Solicitations.
1452		3. If accept_ra is TRUE (default), accept Router
1453		   Advertisements (and do autoconfiguration).
1454		4. If accept_redirects is TRUE (default), accept Redirects.
1455	
1456		TRUE (1):
1457	
1458		If local forwarding is enabled, Router behaviour is assumed.
1459		This means exactly the reverse from the above:
1460	
1461		1. IsRouter flag is set in Neighbour Advertisements.
1462		2. Router Solicitations are not sent unless accept_ra is 2.
1463		3. Router Advertisements are ignored unless accept_ra is 2.
1464		4. Redirects are ignored.
1465	
1466		Default: 0 (disabled) if global forwarding is disabled (default),
1467			 otherwise 1 (enabled).
1468	
1469	hop_limit - INTEGER
1470		Default Hop Limit to set.
1471		Default: 64
1472	
1473	mtu - INTEGER
1474		Default Maximum Transfer Unit
1475		Default: 1280 (IPv6 required minimum)
1476	
1477	ip_nonlocal_bind - BOOLEAN
1478		If set, allows processes to bind() to non-local IPv6 addresses,
1479		which can be quite useful - but may break some applications.
1480		Default: 0
1481	
1482	router_probe_interval - INTEGER
1483		Minimum interval (in seconds) between Router Probing described
1484		in RFC4191.
1485	
1486		Default: 60
1487	
1488	router_solicitation_delay - INTEGER
1489		Number of seconds to wait after interface is brought up
1490		before sending Router Solicitations.
1491		Default: 1
1492	
1493	router_solicitation_interval - INTEGER
1494		Number of seconds to wait between Router Solicitations.
1495		Default: 4
1496	
1497	router_solicitations - INTEGER
1498		Number of Router Solicitations to send until assuming no
1499		routers are present.
1500		Default: 3
1501	
1502	use_oif_addrs_only - BOOLEAN
1503		When enabled, the candidate source addresses for destinations
1504		routed via this interface are restricted to the set of addresses
1505		configured on this interface (vis. RFC 6724, section 4).
1506	
1507		Default: false
1508	
1509	use_tempaddr - INTEGER
1510		Preference for Privacy Extensions (RFC3041).
1511		  <= 0 : disable Privacy Extensions
1512		  == 1 : enable Privacy Extensions, but prefer public
1513		         addresses over temporary addresses.
1514		  >  1 : enable Privacy Extensions and prefer temporary
1515		         addresses over public addresses.
1516		Default:  0 (for most devices)
1517			 -1 (for point-to-point devices and loopback devices)
1518	
1519	temp_valid_lft - INTEGER
1520		valid lifetime (in seconds) for temporary addresses.
1521		Default: 604800 (7 days)
1522	
1523	temp_prefered_lft - INTEGER
1524		Preferred lifetime (in seconds) for temporary addresses.
1525		Default: 86400 (1 day)
1526	
1527	max_desync_factor - INTEGER
1528		Maximum value for DESYNC_FACTOR, which is a random value
1529		that ensures that clients don't synchronize with each
1530		other and generate new addresses at exactly the same time.
1531		value is in seconds.
1532		Default: 600
1533	
1534	regen_max_retry - INTEGER
1535		Number of attempts before give up attempting to generate
1536		valid temporary addresses.
1537		Default: 5
1538	
1539	max_addresses - INTEGER
1540		Maximum number of autoconfigured addresses per interface.  Setting
1541		to zero disables the limitation.  It is not recommended to set this
1542		value too large (or to zero) because it would be an easy way to
1543		crash the kernel by allowing too many addresses to be created.
1544		Default: 16
1545	
1546	disable_ipv6 - BOOLEAN
1547		Disable IPv6 operation.  If accept_dad is set to 2, this value
1548		will be dynamically set to TRUE if DAD fails for the link-local
1549		address.
1550		Default: FALSE (enable IPv6 operation)
1551	
1552		When this value is changed from 1 to 0 (IPv6 is being enabled),
1553		it will dynamically create a link-local address on the given
1554		interface and start Duplicate Address Detection, if necessary.
1555	
1556		When this value is changed from 0 to 1 (IPv6 is being disabled),
1557		it will dynamically delete all address on the given interface.
1558	
1559	accept_dad - INTEGER
1560		Whether to accept DAD (Duplicate Address Detection).
1561		0: Disable DAD
1562		1: Enable DAD (default)
1563		2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
1564		   link-local address has been found.
1565	
1566	force_tllao - BOOLEAN
1567		Enable sending the target link-layer address option even when
1568		responding to a unicast neighbor solicitation.
1569		Default: FALSE
1570	
1571		Quoting from RFC 2461, section 4.4, Target link-layer address:
1572	
1573		"The option MUST be included for multicast solicitations in order to
1574		avoid infinite Neighbor Solicitation "recursion" when the peer node
1575		does not have a cache entry to return a Neighbor Advertisements
1576		message.  When responding to unicast solicitations, the option can be
1577		omitted since the sender of the solicitation has the correct link-
1578		layer address; otherwise it would not have be able to send the unicast
1579		solicitation in the first place. However, including the link-layer
1580		address in this case adds little overhead and eliminates a potential
1581		race condition where the sender deletes the cached link-layer address
1582		prior to receiving a response to a previous solicitation."
1583	
1584	ndisc_notify - BOOLEAN
1585		Define mode for notification of address and device changes.
1586		0 - (default): do nothing
1587		1 - Generate unsolicited neighbour advertisements when device is brought
1588		    up or hardware address changes.
1589	
1590	mldv1_unsolicited_report_interval - INTEGER
1591		The interval in milliseconds in which the next unsolicited
1592		MLDv1 report retransmit will take place.
1593		Default: 10000 (10 seconds)
1594	
1595	mldv2_unsolicited_report_interval - INTEGER
1596		The interval in milliseconds in which the next unsolicited
1597		MLDv2 report retransmit will take place.
1598		Default: 1000 (1 second)
1599	
1600	force_mld_version - INTEGER
1601		0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed
1602		1 - Enforce to use MLD version 1
1603		2 - Enforce to use MLD version 2
1604	
1605	suppress_frag_ndisc - INTEGER
1606		Control RFC 6980 (Security Implications of IPv6 Fragmentation
1607		with IPv6 Neighbor Discovery) behavior:
1608		1 - (default) discard fragmented neighbor discovery packets
1609		0 - allow fragmented neighbor discovery packets
1610	
1611	optimistic_dad - BOOLEAN
1612		Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
1613			0: disabled (default)
1614			1: enabled
1615	
1616	use_optimistic - BOOLEAN
1617		If enabled, do not classify optimistic addresses as deprecated during
1618		source address selection.  Preferred addresses will still be chosen
1619		before optimistic addresses, subject to other ranking in the source
1620		address selection algorithm.
1621			0: disabled (default)
1622			1: enabled
1623	
1624	stable_secret - IPv6 address
1625		This IPv6 address will be used as a secret to generate IPv6
1626		addresses for link-local addresses and autoconfigured
1627		ones. All addresses generated after setting this secret will
1628		be stable privacy ones by default. This can be changed via the
1629		addrgenmode ip-link. conf/default/stable_secret is used as the
1630		secret for the namespace, the interface specific ones can
1631		overwrite that. Writes to conf/all/stable_secret are refused.
1632	
1633		It is recommended to generate this secret during installation
1634		of a system and keep it stable after that.
1635	
1636		By default the stable secret is unset.
1637	
1638	icmp/*:
1639	ratelimit - INTEGER
1640		Limit the maximal rates for sending ICMPv6 packets.
1641		0 to disable any limiting,
1642		otherwise the minimal space between responses in milliseconds.
1643		Default: 1000
1644	
1645	xfrm6_gc_thresh - INTEGER
1646		The threshold at which we will start garbage collecting for IPv6
1647		destination cache entries.  At twice this value the system will
1648		refuse new allocations.
1649	
1650	
1651	IPv6 Update by:
1652	Pekka Savola <pekkas@netcore.fi>
1653	YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
1654	
1655	
1656	/proc/sys/net/bridge/* Variables:
1657	
1658	bridge-nf-call-arptables - BOOLEAN
1659		1 : pass bridged ARP traffic to arptables' FORWARD chain.
1660		0 : disable this.
1661		Default: 1
1662	
1663	bridge-nf-call-iptables - BOOLEAN
1664		1 : pass bridged IPv4 traffic to iptables' chains.
1665		0 : disable this.
1666		Default: 1
1667	
1668	bridge-nf-call-ip6tables - BOOLEAN
1669		1 : pass bridged IPv6 traffic to ip6tables' chains.
1670		0 : disable this.
1671		Default: 1
1672	
1673	bridge-nf-filter-vlan-tagged - BOOLEAN
1674		1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
1675		0 : disable this.
1676		Default: 0
1677	
1678	bridge-nf-filter-pppoe-tagged - BOOLEAN
1679		1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
1680		0 : disable this.
1681		Default: 0
1682	
1683	bridge-nf-pass-vlan-input-dev - BOOLEAN
1684		1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
1685		interface on the bridge and set the netfilter input device to the vlan.
1686		This allows use of e.g. "iptables -i br0.1" and makes the REDIRECT
1687		target work with vlan-on-top-of-bridge interfaces.  When no matching
1688		vlan interface is found, or this switch is off, the input device is
1689		set to the bridge interface.
1690		0: disable bridge netfilter vlan interface lookup.
1691		Default: 0
1692	
1693	proc/sys/net/sctp/* Variables:
1694	
1695	addip_enable - BOOLEAN
1696		Enable or disable extension of  Dynamic Address Reconfiguration
1697		(ADD-IP) functionality specified in RFC5061.  This extension provides
1698		the ability to dynamically add and remove new addresses for the SCTP
1699		associations.
1700	
1701		1: Enable extension.
1702	
1703		0: Disable extension.
1704	
1705		Default: 0
1706	
1707	addip_noauth_enable - BOOLEAN
1708		Dynamic Address Reconfiguration (ADD-IP) requires the use of
1709		authentication to protect the operations of adding or removing new
1710		addresses.  This requirement is mandated so that unauthorized hosts
1711		would not be able to hijack associations.  However, older
1712		implementations may not have implemented this requirement while
1713		allowing the ADD-IP extension.  For reasons of interoperability,
1714		we provide this variable to control the enforcement of the
1715		authentication requirement.
1716	
1717		1: Allow ADD-IP extension to be used without authentication.  This
1718		   should only be set in a closed environment for interoperability
1719		   with older implementations.
1720	
1721		0: Enforce the authentication requirement
1722	
1723		Default: 0
1724	
1725	auth_enable - BOOLEAN
1726		Enable or disable Authenticated Chunks extension.  This extension
1727		provides the ability to send and receive authenticated chunks and is
1728		required for secure operation of Dynamic Address Reconfiguration
1729		(ADD-IP) extension.
1730	
1731		1: Enable this extension.
1732		0: Disable this extension.
1733	
1734		Default: 0
1735	
1736	prsctp_enable - BOOLEAN
1737		Enable or disable the Partial Reliability extension (RFC3758) which
1738		is used to notify peers that a given DATA should no longer be expected.
1739	
1740		1: Enable extension
1741		0: Disable
1742	
1743		Default: 1
1744	
1745	max_burst - INTEGER
1746		The limit of the number of new packets that can be initially sent.  It
1747		controls how bursty the generated traffic can be.
1748	
1749		Default: 4
1750	
1751	association_max_retrans - INTEGER
1752		Set the maximum number for retransmissions that an association can
1753		attempt deciding that the remote end is unreachable.  If this value
1754		is exceeded, the association is terminated.
1755	
1756		Default: 10
1757	
1758	max_init_retransmits - INTEGER
1759		The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
1760		that an association will attempt before declaring the destination
1761		unreachable and terminating.
1762	
1763		Default: 8
1764	
1765	path_max_retrans - INTEGER
1766		The maximum number of retransmissions that will be attempted on a given
1767		path.  Once this threshold is exceeded, the path is considered
1768		unreachable, and new traffic will use a different path when the
1769		association is multihomed.
1770	
1771		Default: 5
1772	
1773	pf_retrans - INTEGER
1774		The number of retransmissions that will be attempted on a given path
1775		before traffic is redirected to an alternate transport (should one
1776		exist).  Note this is distinct from path_max_retrans, as a path that
1777		passes the pf_retrans threshold can still be used.  Its only
1778		deprioritized when a transmission path is selected by the stack.  This
1779		setting is primarily used to enable fast failover mechanisms without
1780		having to reduce path_max_retrans to a very low value.  See:
1781		http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
1782		for details.  Note also that a value of pf_retrans > path_max_retrans
1783		disables this feature
1784	
1785		Default: 0
1786	
1787	rto_initial - INTEGER
1788		The initial round trip timeout value in milliseconds that will be used
1789		in calculating round trip times.  This is the initial time interval
1790		for retransmissions.
1791	
1792		Default: 3000
1793	
1794	rto_max - INTEGER
1795		The maximum value (in milliseconds) of the round trip timeout.  This
1796		is the largest time interval that can elapse between retransmissions.
1797	
1798		Default: 60000
1799	
1800	rto_min - INTEGER
1801		The minimum value (in milliseconds) of the round trip timeout.  This
1802		is the smallest time interval the can elapse between retransmissions.
1803	
1804		Default: 1000
1805	
1806	hb_interval - INTEGER
1807		The interval (in milliseconds) between HEARTBEAT chunks.  These chunks
1808		are sent at the specified interval on idle paths to probe the state of
1809		a given path between 2 associations.
1810	
1811		Default: 30000
1812	
1813	sack_timeout - INTEGER
1814		The amount of time (in milliseconds) that the implementation will wait
1815		to send a SACK.
1816	
1817		Default: 200
1818	
1819	valid_cookie_life - INTEGER
1820		The default lifetime of the SCTP cookie (in milliseconds).  The cookie
1821		is used during association establishment.
1822	
1823		Default: 60000
1824	
1825	cookie_preserve_enable - BOOLEAN
1826		Enable or disable the ability to extend the lifetime of the SCTP cookie
1827		that is used during the establishment phase of SCTP association
1828	
1829		1: Enable cookie lifetime extension.
1830		0: Disable
1831	
1832		Default: 1
1833	
1834	cookie_hmac_alg - STRING
1835		Select the hmac algorithm used when generating the cookie value sent by
1836		a listening sctp socket to a connecting client in the INIT-ACK chunk.
1837		Valid values are:
1838		* md5
1839		* sha1
1840		* none
1841		Ability to assign md5 or sha1 as the selected alg is predicated on the
1842		configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
1843		CONFIG_CRYPTO_SHA1).
1844	
1845		Default: Dependent on configuration.  MD5 if available, else SHA1 if
1846		available, else none.
1847	
1848	rcvbuf_policy - INTEGER
1849		Determines if the receive buffer is attributed to the socket or to
1850		association.   SCTP supports the capability to create multiple
1851		associations on a single socket.  When using this capability, it is
1852		possible that a single stalled association that's buffering a lot
1853		of data may block other associations from delivering their data by
1854		consuming all of the receive buffer space.  To work around this,
1855		the rcvbuf_policy could be set to attribute the receiver buffer space
1856		to each association instead of the socket.  This prevents the described
1857		blocking.
1858	
1859		1: rcvbuf space is per association
1860		0: rcvbuf space is per socket
1861	
1862		Default: 0
1863	
1864	sndbuf_policy - INTEGER
1865		Similar to rcvbuf_policy above, this applies to send buffer space.
1866	
1867		1: Send buffer is tracked per association
1868		0: Send buffer is tracked per socket.
1869	
1870		Default: 0
1871	
1872	sctp_mem - vector of 3 INTEGERs: min, pressure, max
1873		Number of pages allowed for queueing by all SCTP sockets.
1874	
1875		min: Below this number of pages SCTP is not bothered about its
1876		memory appetite. When amount of memory allocated by SCTP exceeds
1877		this number, SCTP starts to moderate memory usage.
1878	
1879		pressure: This value was introduced to follow format of tcp_mem.
1880	
1881		max: Number of pages allowed for queueing by all SCTP sockets.
1882	
1883		Default is calculated at boot time from amount of available memory.
1884	
1885	sctp_rmem - vector of 3 INTEGERs: min, default, max
1886		Only the first value ("min") is used, "default" and "max" are
1887		ignored.
1888	
1889		min: Minimal size of receive buffer used by SCTP socket.
1890		It is guaranteed to each SCTP socket (but not association) even
1891		under moderate memory pressure.
1892	
1893		Default: 1 page
1894	
1895	sctp_wmem  - vector of 3 INTEGERs: min, default, max
1896		Currently this tunable has no effect.
1897	
1898	addr_scope_policy - INTEGER
1899		Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
1900	
1901		0   - Disable IPv4 address scoping
1902		1   - Enable IPv4 address scoping
1903		2   - Follow draft but allow IPv4 private addresses
1904		3   - Follow draft but allow IPv4 link local addresses
1905	
1906		Default: 1
1907	
1908	
1909	/proc/sys/net/core/*
1910		Please see: Documentation/sysctl/net.txt for descriptions of these entries.
1911	
1912	
1913	/proc/sys/net/unix/*
1914	max_dgram_qlen - INTEGER
1915		The maximum length of dgram socket receive queue
1916	
1917		Default: 10
1918	
1919	
1920	UNDOCUMENTED:
1921	
1922	/proc/sys/net/irda/*
1923		fast_poll_increase FIXME
1924		warn_noreply_time FIXME
1925		discovery_slots FIXME
1926		slot_timeout FIXME
1927		max_baud_rate FIXME
1928		discovery_timeout FIXME
1929		lap_keepalive_time FIXME
1930		max_noreply_time FIXME
1931		max_tx_data_size FIXME
1932		max_tx_window FIXME
1933		min_tx_turn_time FIXME
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