netdev - Re: [PATCH v2 ipsec-next] xfrm: Add possibility to set the default to block if we have no policy

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Date:   Wed, 1 Sep 2021 18:14:02 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Antony Antony <antony.antony@...unet.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Christian Langrock <christian.langrock@...unet.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 ipsec-next] xfrm: Add possibility to set the default
 to block if we have no policy

Hi,

On Sun, Jul 18, 2021 at 09:11:06AM +0200, Antony Antony wrote:
> From: Steffen Klassert <steffen.klassert@...unet.com>
> 
> As the default we assume the traffic to pass, if we have no
> matching IPsec policy. With this patch, we have a possibility to
> change this default from allow to block. It can be configured
> via netlink. Each direction (input/output/forward) can be
> configured separately. With the default to block configuered,
> we need allow policies for all packet flows we accept.
> We do not use default policy lookup for the loopback device.
> 
> v1->v2
>  - fix compiling when XFRM is disabled
>  - Reported-by: kernel test robot <lkp@...el.com>
> 
> Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> Co-developed-by: Christian Langrock <christian.langrock@...unet.com>
> Signed-off-by: Christian Langrock <christian.langrock@...unet.com>
> Co-developed-by: Antony Antony <antony.antony@...unet.com>
> Signed-off-by: Antony Antony <antony.antony@...unet.com>
[...]

The following part of this patch is ABI break:

> diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
> index ffc6a5391bb7..6e8095106192 100644
> --- a/include/uapi/linux/xfrm.h
> +++ b/include/uapi/linux/xfrm.h
> @@ -213,6 +213,11 @@ enum {
>  	XFRM_MSG_GETSPDINFO,
>  #define XFRM_MSG_GETSPDINFO XFRM_MSG_GETSPDINFO
> 
> +	XFRM_MSG_SETDEFAULT,
> +#define XFRM_MSG_SETDEFAULT XFRM_MSG_SETDEFAULT
> +	XFRM_MSG_GETDEFAULT,
> +#define XFRM_MSG_GETDEFAULT XFRM_MSG_GETDEFAULT
> +
>  	XFRM_MSG_MAPPING,
>  #define XFRM_MSG_MAPPING XFRM_MSG_MAPPING
>  	__XFRM_MSG_MAX

After this change, strace no longer builds with the following diagnostics:

../../../src/xlat/nl_xfrm_types.h:162:1: error: static assertion failed: "XFRM_MSG_MAPPING != 0x26"
  162 | static_assert((XFRM_MSG_MAPPING) == (0x26), "XFRM_MSG_MAPPING != 0x26");


-- 
ldv