Re: [net-next v2 2/3] seg6: add NEXT-C-SID support for SRv6 End behavior

[David Ahern <dsahern@kernel.org>]

On 9/12/22 11:16 AM, 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.
> 
> The NEXT-C-SID mechanism relies on the "flavors" framework defined in
> [2]. The flavors represent additional operations that can modify or
> extend a subset of the existing behaviors.
> 
> This patch introduces the support for flavors in SRv6 End behavior
> implementing the NEXT-C-SID one. An SRv6 End behavior with NEXT-C-SID
> flavor works as an End behavior but it is capable of processing the
> compressed SID List encoded in C-SID containers.
> 
> An SRv6 End 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 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://datatracker.ietf.org/doc/html/rfc8986
> 
> Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
> ---
>  include/uapi/linux/seg6_local.h |  24 +++
>  net/ipv6/seg6_local.c           | 335 +++++++++++++++++++++++++++++++-
>  2 files changed, 356 insertions(+), 3 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>