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, 11 Aug 2021 18:14:08 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     antony.antony@...unet.com,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     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

Le 18/07/2021 à 09:11, Antony Antony a écrit :
> From: Steffen Klassert <steffen.klassert@...unet.com>
Sorry for my late reply, I was off.

> 
> 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.
> 

[snip]

> diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
> index e946366e8ba5..88c647302977 100644
> --- a/include/net/netns/xfrm.h
> +++ b/include/net/netns/xfrm.h
> @@ -65,6 +65,13 @@ struct netns_xfrm {
>  	u32			sysctl_aevent_rseqth;
>  	int			sysctl_larval_drop;
>  	u32			sysctl_acq_expires;
> +
> +	u8			policy_default;
> +#define XFRM_POL_DEFAULT_IN	1
> +#define XFRM_POL_DEFAULT_OUT	2
> +#define XFRM_POL_DEFAULT_FWD	4
> +#define XFRM_POL_DEFAULT_MASK	7
> +

[snip]

> 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
> @@ -508,6 +513,11 @@ struct xfrm_user_offload {
>  #define XFRM_OFFLOAD_IPV6	1
>  #define XFRM_OFFLOAD_INBOUND	2
> 
> +struct xfrm_userpolicy_default {
> +	__u8				dirmask;
> +	__u8				action;
> +};
> +
Should XFRM_POL_DEFAULT_* be moved in the uapi?
How can a user knows what value is expected in dirmask?

Same question for action. We should avoid magic values. 0 means drop or accept?
Maybe renaming this field to 'drop' is enough.


Regards,
Nicolas