sctp: Add documentation for sctp sysctl variable

	Default: 1

proc/sys/net/sctp/* Variables:

addip_enable - BOOLEAN

	Enable or disable extension of  Dynamic Address Reconfiguration

	(ADD-IP) functionality specified in RFC5061.  This extension provides

	the ability to dynamically add and remove new addresses for the SCTP

	associations.

	1: Enable extension.

	0: Disable extension.

	Default: 0

addip_noauth_enable - BOOLEAN

	Dynamic Address Reconfiguration (ADD-IP) requires the use of

	authentication to protect the operations of adding or removing new

	addresses.  This requirement is mandated so that unauthorized hosts

	would not be able to hijack associations.  However, older

	implementations may not have implemented this requirement while

	allowing the ADD-IP extension.  For reasons of interoperability,

	we provide this variable to control the enforcement of the

	authentication requirement.

	1: Allow ADD-IP extension to be used without authentication.  This

	   should only be set in a closed environment for interoperability

	   with older implementations.

	0: Enforce the authentication requirement

	Default: 0

auth_enable - BOOLEAN

	Enable or disable Authenticated Chunks extension.  This extension

	provides the ability to send and receive authenticated chunks and is

	required for secure operation of Dynamic Address Reconfiguration

	(ADD-IP) extension.

	1: Enable this extension.

	0: Disable this extension.

	Default: 0

prsctp_enable - BOOLEAN

	Enable or disable the Partial Reliability extension (RFC3758) which

	is used to notify peers that a given DATA should no longer be expected.

	1: Enable extension

	0: Disable

	Default: 1

max_burst - INTEGER

	The limit of the number of new packets that can be initially sent.  It

	controls how bursty the generated traffic can be.

	Default: 4

association_max_retrans - INTEGER

	Set the maximum number for retransmissions that an association can

	attempt deciding that the remote end is unreachable.  If this value

	is exceeded, the association is terminated.

	Default: 10

max_init_retransmits - INTEGER

	The maximum number of retransmissions of INIT and COOKIE-ECHO chunks

	that an association will attempt before declaring the destination

	unreachable and terminating.

	Default: 8

path_max_retrans - INTEGER

	The maximum number of retransmissions that will be attempted on a given

	path.  Once this threshold is exceeded, the path is considered

	unreachable, and new traffic will use a different path when the

	association is multihomed.

	Default: 5

rto_initial - INTEGER

	The initial round trip timeout value in milliseconds that will be used

	in calculating round trip times.  This is the initial time interval

	for retransmissions.

	Default: 3000

rto_max - INTEGER

	The maximum value (in milliseconds) of the round trip timeout.  This

	is the largest time interval that can elapse between retransmissions.

	Default: 60000

rto_min - INTEGER

	The minimum value (in milliseconds) of the round trip timeout.  This

	is the smallest time interval the can elapse between retransmissions.

	Default: 1000

hb_interval - INTEGER

	The interval (in milliseconds) between HEARTBEAT chunks.  These chunks

	are sent at the specified interval on idle paths to probe the state of

	a given path between 2 associations.

	Default: 30000

sack_timeout - INTEGER

	The amount of time (in milliseconds) that the implementation will wait

	to send a SACK.

	Default: 200

valid_cookie_life - INTEGER

	The default lifetime of the SCTP cookie (in milliseconds).  The cookie

	is used during association establishment.

	Default: 60000

cookie_preserve_enable - BOOLEAN

	Enable or disable the ability to extend the lifetime of the SCTP cookie

	that is used during the establishment phase of SCTP association

	1: Enable cookie lifetime extension.

	0: Disable

	Default: 1

rcvbuf_policy - INTEGER

	Determines if the receive buffer is attributed to the socket or to

	association.   SCTP supports the capability to create multiple

	associations on a single socket.  When using this capability, it is

	possible that a single stalled association that's buffering a lot

	of data may block other associations from delivering their data by

	consuming all of the receive buffer space.  To work around this,

	the rcvbuf_policy could be set to attribute the receiver buffer space

	to each association instead of the socket.  This prevents the described

	blocking.

	1: rcvbuf space is per association

	0: recbuf space is per socket

	Default: 0

sndbuf_policy - INTEGER

	Similar to rcvbuf_policy above, this applies to send buffer space.

	1: Send buffer is tracked per association

	0: Send buffer is tracked per socket.

	Default: 0

sctp_mem - vector of 3 INTEGERs: min, pressure, max

	Number of pages allowed for queueing by all SCTP sockets.

	min: Below this number of pages SCTP is not bothered about its

	memory appetite. When amount of memory allocated by SCTP exceeds

	this number, SCTP starts to moderate memory usage.

	pressure: This value was introduced to follow format of tcp_mem.

	max: Number of pages allowed for queueing by all SCTP sockets.

	Default is calculated at boot time from amount of available memory.

sctp_rmem - vector of 3 INTEGERs: min, default, max

	See tcp_rmem for a description.

sctp_wmem  - vector of 3 INTEGERs: min, default, max

	See tcp_wmem for a description.

UNDOCUMENTED:

dev_weight FIXME