Re: [PATCH ipsec-next v2] udpencap: Remove Obsolete UDP_ENCAP_ESPINUDP_NON_IKE Support

[Steffen Klassert <steffen.klassert@secunet.com>]

On Thu, Apr 04, 2024 at 10:51:31AM +0200, Antony Antony wrote:
> The UDP_ENCAP_ESPINUDP_NON_IKE mode, introduced into the Linux kernel
> in 2004 [2], has remained inactive and obsolete for an extended period.
> 
> This mode was originally defined in an early version of an IETF draft
> [1] from 2001. By the time it was integrated into the kernel in 2004 [2],
> it had already been replaced by UDP_ENCAP_ESPINUDP [3] in later
> versions of draft-ietf-ipsec-udp-encaps, particularly in version 06.
> 
> Over time, UDP_ENCAP_ESPINUDP_NON_IKE has lost its relevance, with no
> known use cases.
> 
> With this commit, we remove support for UDP_ENCAP_ESPINUDP_NON_IKE,
> simplifying the codebase and eliminating unnecessary complexity.
> Actually, we remove the functionality and wrap  UDP_ENCAP_ESPINUDP_NON_IKE
> defination in "#ifndef __KERNEL__". If it is used again in kernel code
> your build will fail.
> 
> References:
> [1] https://datatracker.ietf.org/doc/html/draft-ietf-ipsec-udp-encaps-00.txt
> 
> [2] Commit that added UDP_ENCAP_ESPINUDP_NON_IKE to the Linux historic
>     repository.
> 
>     Author: Andreas Gruenbacher <agruen@suse.de>
>     Date: Fri Apr 9 01:47:47 2004 -0700
> 
>    [IPSEC]: Support draft-ietf-ipsec-udp-encaps-00/01, some ipec impls need it.
> 
> [3] Commit that added UDP_ENCAP_ESPINUDP to the Linux historic
>     repository.
> 
>     Author: Derek Atkins <derek@ihtfp.com>
>     Date: Wed Apr 2 13:21:02 2003 -0800
> 
>     [IPSEC]: Implement UDP Encapsulation framework.
> 
> Signed-off-by: Antony Antony <antony.antony@secunet.com>
> ---
> v1 -> v2
> - removed defination wrapped in #ifndef __KERNEL__ It would falsly
>   let userspace appliction build and break when running.
> RFC -> v1
> - keep removed defination wrapped in #ifndef __KERNEL__
> ---
>  include/uapi/linux/udp.h |  1 -
>  net/ipv4/esp4.c          | 12 ------------
>  net/ipv4/udp.c           |  2 --
>  net/ipv4/xfrm4_input.c   | 13 -------------
>  net/ipv6/esp6.c          | 12 ------------
>  net/ipv6/xfrm6_input.c   | 13 -------------
>  6 files changed, 53 deletions(-)
> 
> diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
> index 4828794efcf8..1516f53698e0 100644
> --- a/include/uapi/linux/udp.h
> +++ b/include/uapi/linux/udp.h
> @@ -36,7 +36,6 @@ struct udphdr {
>  #define UDP_GRO		104	/* This socket can receive UDP GRO packets */
> 
>  /* UDP encapsulation types */
> -#define UDP_ENCAP_ESPINUDP_NON_IKE	1 /* draft-ietf-ipsec-nat-t-ike-00/01 */

Please don't remove that, it is part of the ABI.
Typically this is left in and marked as: /* unused */