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Message-ID: <92d32852-17f0-099c-a2b5-12a29da14133@kernel.org>
Date: Mon, 14 Aug 2023 10:16:46 -0600
From: David Ahern <dsahern@...nel.org>
To: Andrea Mayer <andrea.mayer@...roma2.it>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-kselftest@...r.kernel.org
Cc: Stefano Salsano <stefano.salsano@...roma2.it>,
Paolo Lungaroni <paolo.lungaroni@...roma2.it>,
Ahmed Abdelsalam <ahabdels.dev@...il.com>,
Hangbin Liu <liuhangbin@...il.com>
Subject: Re: [net-next v2 1/2] seg6: add NEXT-C-SID support for SRv6 End.X
behavior
On 8/12/23 12:09 PM, Andrea Mayer wrote:
> The NEXT-C-SID mechanism described in [1] offers the possibility of
> encoding several SRv6 segments within a single 128 bit SID address. Such
> a SID address is called a Compressed SID (C-SID) container. In this way,
> the length of the SID List can be drastically reduced.
>
> A SID instantiated with the NEXT-C-SID flavor considers an IPv6 address
> logically structured in three main blocks: i) Locator-Block; ii)
> Locator-Node Function; iii) Argument.
>
> C-SID container
> +------------------------------------------------------------------+
> | Locator-Block |Loc-Node| Argument |
> | |Function| |
> +------------------------------------------------------------------+
> <--------- B -----------> <- NF -> <------------- A --------------->
>
> (i) The Locator-Block can be any IPv6 prefix available to the provider;
>
> (ii) The Locator-Node Function represents the node and the function to
> be triggered when a packet is received on the node;
>
> (iii) The Argument carries the remaining C-SIDs in the current C-SID
> container.
>
> This patch leverages the NEXT-C-SID mechanism previously introduced in the
> Linux SRv6 subsystem [2] to support SID compression capabilities in the
> SRv6 End.X behavior [3].
> An SRv6 End.X behavior with NEXT-C-SID flavor works as an End.X behavior
> but it is capable of processing the compressed SID List encoded in C-SID
> containers.
>
> An SRv6 End.X behavior with NEXT-C-SID flavor can be configured to support
> user-provided Locator-Block and Locator-Node Function lengths. In this
> implementation, such lengths must be evenly divisible by 8 (i.e. must be
> byte-aligned), otherwise the kernel informs the user about invalid
> values with a meaningful error code and message through netlink_ext_ack.
>
> If Locator-Block and/or Locator-Node Function lengths are not provided
> by the user during configuration of an SRv6 End.X behavior instance with
> NEXT-C-SID flavor, the kernel will choose their default values i.e.,
> 32-bit Locator-Block and 16-bit Locator-Node Function.
>
> [1] - https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression
> [2] - https://lore.kernel.org/all/20220912171619.16943-1-andrea.mayer@uniroma2.it/
> [3] - https://datatracker.ietf.org/doc/html/rfc8986#name-endx-l3-cross-connect
>
> Signed-off-by: Andrea Mayer <andrea.mayer@...roma2.it>
> ---
> net/ipv6/seg6_local.c | 108 ++++++++++++++++++++++++++++++++++--------
> 1 file changed, 88 insertions(+), 20 deletions(-)
>
Reviewed-by: David Ahern <dsahern@...nel.org>
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