Merge branch 'documentation-add-description-for-a-couple-of-sctp-sysctl-options'

Xin Long says:

====================
Documentation: add description for a couple of sctp sysctl options

These are a couple of sysctl options I recently added, but missed adding
documents for them. Especially for net.sctp.intl_enable, it's hard for
users to setup stream interleaving, as it also needs to call some socket
options.

This patchset is to add documents for them.
====================

Link: https://lore.kernel.org/r/cover.1654787716.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

Documentation/networking/ip-sysctl.rst

@@ -2925,6 +2925,43 @@ plpmtud_probe_interval - INTEGER
 
 	Default: 0
 
+reconf_enable - BOOLEAN
+        Enable or disable extension of Stream Reconfiguration functionality
+        specified in RFC6525. This extension provides the ability to "reset"
+        a stream, and it includes the Parameters of "Outgoing/Incoming SSN
+        Reset", "SSN/TSN Reset" and "Add Outgoing/Incoming Streams".
+
+	- 1: Enable extension.
+	- 0: Disable extension.
+
+	Default: 0
+
+intl_enable - BOOLEAN
+        Enable or disable extension of User Message Interleaving functionality
+        specified in RFC8260. This extension allows the interleaving of user
+        messages sent on different streams. With this feature enabled, I-DATA
+        chunk will replace DATA chunk to carry user messages if also supported
+        by the peer. Note that to use this feature, one needs to set this option
+        to 1 and also needs to set socket options SCTP_FRAGMENT_INTERLEAVE to 2
+        and SCTP_INTERLEAVING_SUPPORTED to 1.
+
+	- 1: Enable extension.
+	- 0: Disable extension.
+
+	Default: 0
+
+ecn_enable - BOOLEAN
+        Control use of Explicit Congestion Notification (ECN) by SCTP.
+        Like in TCP, ECN is used only when both ends of the SCTP connection
+        indicate support for it. This feature is useful in avoiding losses
+        due to congestion by allowing supporting routers to signal congestion
+        before having to drop packets.
+
+        1: Enable ecn.
+        0: Disable ecn.
+
+        Default: 1
+
 
 ``/proc/sys/net/core/*``
 ========================