netdev - [PATCH net-next v6 07/10] ipv6: Document enforce_ext_hdr

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Message-ID: <20260203004853.94438-8-tom@herbertland.com>
Date: Mon,  2 Feb 2026 16:48:50 -0800
From: Tom Herbert <tom@...bertland.com>
To: davem@...emloft.net,
	kuba@...nel.org,
	netdev@...r.kernel.org,
	justin.iurman@...ege.be,
	willemdebruijn.kernel@...il.com
Cc: Tom Herbert <tom@...bertland.com>
Subject: [PATCH net-next v6 07/10] 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 | 34 ++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 5051fe653c96..a0ad32240dc9 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2485,8 +2485,8 @@ max_dst_opts_number - INTEGER
         Default: 2
 
 max_hbh_opts_number - INTEGER
-	Maximum number of non-padding TLVs allowed in a Hop-by-Hop
-	options extension header. If this value is zero then receive
+        Maximum number of non-padding TLVs allowed in a Hop-by-Hop
+        options extension header. If this value is zero then receive
         Hop-by-Hop Options processing is disabled in which case packets
         with the Hop-by-Hop Options extension header are dropped.
         If this value is less than zero then unknown options are disallowed
@@ -2581,6 +2581,36 @@ 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 is enforced in
+	received packets and each Extension Header may be present
+	at most once per packet (except for Destination Options that
+	may occur twice). 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 occurrences per packet (except
+	for Hop-by-Hop Options that must always be the first Extension
+	Header and occur at most once in a packet)).
+
+	The Extension Header order is:
+
+	    IPv6 header
+	    Hop-by-Hop Options header
+	    Destination Options before the Routing 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