netdev - Re: [PATCH net-next v5 5/7] ipv6: Document defaults for max_{dst|hbh}_opts

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Message-ID: <6ad1412d-544b-44d0-b55a-f39a2693ebcd@gmail.com>
Date: Tue, 27 Jan 2026 18:57:34 +0100
From: Justin Iurman <justin.iurman@...il.com>
To: Tom Herbert <tom@...bertland.com>, davem@...emloft.net, kuba@...nel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 5/7] ipv6: Document defaults for
 max_{dst|hbh}_opts_number sysctls

On 1/26/26 20:48, Tom Herbert wrote:
> In the descriptions of max_dst_opts_number and max_hbh_opts_number
> sysctls add text about how a zero setting means that a packet with
> any Destination or Hop-by-Hop options is dropped.
> 
> Report the defaults for max_dst_opts_number and max_hbh_opts_number
> are 2 which means up to two options may be accepted.
> 
> Signed-off-by: Tom Herbert <tom@...bertland.com>
> ---
>   Documentation/networking/ip-sysctl.rst | 24 +++++++++++++++---------
>   1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index bc9a01606daf..4f568b0e39d2 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -2475,19 +2475,25 @@ mld_qrv - INTEGER
>   
>   max_dst_opts_number - INTEGER
>   	Maximum number of non-padding TLVs allowed in a Destination
> -	options extension header. If this value is less than zero
> -	then unknown options are disallowed and the number of known
> -	TLVs allowed is the absolute value of this number.
> +	options extension header. If this value is zero then receive
> +	Destination Options processing is disabled in which case packets
> +	with the Destination Options extension header are dropped. If
> +	this value is less than zero then unknown options are disallowed
> +	and the number of known TLVs allowed is the absolute value of
> +	this number.
>   
> -	Default: 8
> +        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 less than zero
> -	then unknown options are disallowed and the number of known
> -	TLVs allowed is the absolute value of this number.
> -
> -	Default: 8
> +	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
> +	and the number of known TLVs allowed is the absolute value of this
> +	number.
> +
> +        Default: 2
>   
>   max_dst_opts_length - INTEGER
>   	Maximum length allowed for a Destination options extension

Reviewed-by: Justin Iurman <justin.iurman@...il.com>