netdev - Re: [PATCH net-next v4 2/2] net/sched: cls_flower: add support for matching tunnel control flags

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Date: Wed, 5 Jun 2024 07:37:13 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Davide Caratti <dcaratti@...hat.com>, i.maximets@....org
Cc: davem@...emloft.net, edumazet@...gle.com, jhs@...atatu.com,
 jiri@...nulli.us, kuba@...nel.org, lucien.xin@...il.com,
 marcelo.leitner@...il.com, netdev@...r.kernel.org, pabeni@...hat.com,
 xiyou.wangcong@...il.com, echaudro@...hat.com,
 Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v4 2/2] net/sched: cls_flower: add support for
 matching tunnel control flags

Hi Davide and Ilva,

On 5/30/24 5:08 PM, Davide Caratti wrote:
> extend cls_flower to match TUNNEL_FLAGS_PRESENT bits in tunnel metadata.
> 
> Suggested-by: Ilya Maximets <i.maximets@....org>
> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>
> ---
>   include/uapi/linux/pkt_cls.h |  3 ++
>   net/sched/cls_flower.c       | 56 +++++++++++++++++++++++++++++++++++-
>   2 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> index 229fc925ec3a..b6d38f5fd7c0 100644
> --- a/include/uapi/linux/pkt_cls.h
> +++ b/include/uapi/linux/pkt_cls.h
> @@ -554,6 +554,9 @@ enum {
>   	TCA_FLOWER_KEY_SPI,		/* be32 */
>   	TCA_FLOWER_KEY_SPI_MASK,	/* be32 */
>   
> +	TCA_FLOWER_KEY_ENC_FLAGS,	/* u32 */
> +	TCA_FLOWER_KEY_ENC_FLAGS_MASK,	/* u32 */
> +
>   	__TCA_FLOWER_MAX,
>   };
>   
> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> index fd9a6f20b60b..eef570c577ac 100644
> --- a/net/sched/cls_flower.c
> +++ b/net/sched/cls_flower.c
> @@ -41,6 +41,12 @@
>   #define TCA_FLOWER_KEY_CT_FLAGS_MASK \
>   		(TCA_FLOWER_KEY_CT_FLAGS_MAX - 1)
>   
> +#define TUNNEL_FLAGS_PRESENT (\
> +	_BITUL(IP_TUNNEL_CSUM_BIT) |		\
> +	_BITUL(IP_TUNNEL_DONT_FRAGMENT_BIT) |	\
> +	_BITUL(IP_TUNNEL_OAM_BIT) |		\
> +	_BITUL(IP_TUNNEL_CRIT_OPT_BIT))
> +
>   struct fl_flow_key {
>   	struct flow_dissector_key_meta meta;
>   	struct flow_dissector_key_control control;
> @@ -75,6 +81,7 @@ struct fl_flow_key {
>   	struct flow_dissector_key_l2tpv3 l2tpv3;
>   	struct flow_dissector_key_ipsec ipsec;
>   	struct flow_dissector_key_cfm cfm;
> +	struct flow_dissector_key_enc_flags enc_flags;
>   } __aligned(BITS_PER_LONG / 8); /* Ensure that we can do comparisons as longs. */
>   
>   struct fl_flow_mask_range {
> @@ -732,6 +739,10 @@ static const struct nla_policy fl_policy[TCA_FLOWER_MAX + 1] = {
>   	[TCA_FLOWER_KEY_SPI_MASK]	= { .type = NLA_U32 },
>   	[TCA_FLOWER_L2_MISS]		= NLA_POLICY_MAX(NLA_U8, 1),
>   	[TCA_FLOWER_KEY_CFM]		= { .type = NLA_NESTED },
> +	[TCA_FLOWER_KEY_ENC_FLAGS]	= NLA_POLICY_MASK(NLA_U32,
> +							  TUNNEL_FLAGS_PRESENT),
> +`	[TCA_FLOWER_KEY_ENC_FLAGS_MASK]	= NLA_POLICY_MASK(NLA_U32,
> +							  TUNNEL_FLAGS_PRESENT),
>   };
>   
>   static const struct nla_policy
> @@ -1825,6 +1836,21 @@ static int fl_set_key_cfm(struct nlattr **tb,
>   	return 0;
>   }
>   
> +static int fl_set_key_enc_flags(struct nlattr **tb, u32 *flags_key,
> +				u32 *flags_mask, struct netlink_ext_ack *extack)
> +{
> +	/* mask is mandatory for flags */
> +	if (NL_REQ_ATTR_CHECK(extack, NULL, tb, TCA_FLOWER_KEY_ENC_FLAGS_MASK)) {
> +		NL_SET_ERR_MSG(extack, "missing enc_flags mask");
> +		return -EINVAL;
> +	}
> +
> +	*flags_key = nla_get_u32(tb[TCA_FLOWER_KEY_ENC_FLAGS]);
> +	*flags_mask = nla_get_u32(tb[TCA_FLOWER_KEY_ENC_FLAGS_MASK]);
> +
> +	return 0;
> +}
> +
>   static int fl_set_key(struct net *net, struct nlattr **tb,
>   		      struct fl_flow_key *key, struct fl_flow_key *mask,
>   		      struct netlink_ext_ack *extack)
> @@ -2059,9 +2085,16 @@ static int fl_set_key(struct net *net, struct nlattr **tb,
>   	if (ret)
>   		return ret;
>   
> -	if (tb[TCA_FLOWER_KEY_FLAGS])
> +	if (tb[TCA_FLOWER_KEY_FLAGS]) {
>   		ret = fl_set_key_flags(tb, &key->control.flags,
>   				       &mask->control.flags, extack);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (tb[TCA_FLOWER_KEY_ENC_FLAGS])
> +		ret = fl_set_key_enc_flags(tb, &key->enc_flags.flags,
> +					   &mask->enc_flags.flags, extack);
>   
>   	return ret;

Sorry, that I am late to the party, I have been away camping at
Electromagnetic Field in the UK.

Why not use the already existing key->enc_control.flags with dissector
key FLOW_DISSECTOR_KEY_ENC_CONTROL for storing the flags?

Currently key->enc_control.flags are unused.

I haven't fixed the drivers to validate that field yet, so currently
only sfc does so.

Look at include/uapi/linux/pkt_cls.h for netlink flags:

enum {
         TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT = (1 << 0),
         TCA_FLOWER_KEY_FLAGS_FRAG_IS_FIRST = (1 << 1),
};

and at include/net/flow_dissector.h for the dissector flags:

#define FLOW_DIS_IS_FRAGMENT    BIT(0)
#define FLOW_DIS_FIRST_FRAG     BIT(1)
#define FLOW_DIS_ENCAPSULATION  BIT(2)

I would like to keep FLOW_DIS_ENCAPSULATION as the last flag, in order to
keep parity with the netlink flags, since the dissector flags field is
exposed to user space when some flags are not supported.

I realize that since this series is now merged, then fixing this up will
have to go in another series, are you up for that?

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541