netdev - [PATCH net-next v4 7/7] ipv6: Document enforce_ext_hdr

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Message-ID: <20260121214925.112604-8-tom@herbertland.com>
Date: Wed, 21 Jan 2026 13:49:25 -0800
From: Tom Herbert <tom@...bertland.com>
To: davem@...emloft.net,
	kuba@...nel.org,
	netdev@...r.kernel.org,
	justin.iurman@...ege.be
Cc: Tom Herbert <tom@...bertland.com>
Subject: [PATCH net-next v4 7/7] ipv6: Document enforce_ext_hdr_order sysctl

Document the enforce_ext_hdr_order sysctl that controls whether
Extension Header order is enforced on receive.

Signed-off-by: Tom Herbert <tom@...bertland.com>
---
 Documentation/networking/ip-sysctl.rst | 29 ++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 5051fe653c96..f8fa9f67b2ed 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2581,6 +2581,35 @@ ioam6_id_wide - LONG INTEGER
 
         Default: 0xFFFFFFFFFFFFFF
 
+enforce_ext_hdr_order - BOOLEAN
+	Enforce recommended Extension Header ordering in RFC8200.
+	If the sysctl is set to 1 then the ordering the ordering is
+	enforced in received packets and each Extension Header
+	may be present at most once per packet. If the sysctl is
+	set to 0 then ordering is not enforced and Extension Headers
+	may be present in any order and have any number of
+	occurences per packet (except for Hop-by-Hop Options). Also,
+	if the sysctl is set then Destination Options before the
+	Routing header are disllowed.
+
+	The Extension Header order is:
+
+	    IPv6 header
+	    Hop-by-Hop Options header
+	    Routing header
+	    Fragment header
+	    Authentication header
+	    Encapsulating Security Payload header
+	    Destination Options header
+	    Upper-Layer header
+
+	Possible values:
+
+	- 0 (disabled)
+	- 1 (enabled)
+
+	Default: 1 (enabled)
+
 IPv6 Fragmentation:
 
 ip6frag_high_thresh - INTEGER
-- 
2.43.0