netdev - Re: [RFC net-next v2 3/5] net: psample: add user cookie

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Date: Mon, 8 Apr 2024 15:19:35 +0200
From: Ilya Maximets <i.maximets@....org>
To: Adrian Moreno <amorenoz@...hat.com>, netdev@...r.kernel.org
Cc: i.maximets@....org, jiri@...nulli.us, xiyou.wangcong@...il.com,
 cmi@...dia.com, yotam.gi@...il.com, aconole@...hat.com, echaudro@...hat.com,
 horms@...nel.org
Subject: Re: [RFC net-next v2 3/5] net: psample: add user cookie

[copying my previous reply since this version actually has netdev@ in Cc]

On 4/8/24 14:57, Adrian Moreno wrote:
> Add a user cookie to the sample metadata so that sample emitters can
> provide more contextual information to samples.
> 
> If present, send the user cookie in a new attribute:
> PSAMPLE_ATTR_USER_COOKIE.
> 
> Signed-off-by: Adrian Moreno <amorenoz@...hat.com>
> ---
>  include/net/psample.h        |  2 ++
>  include/uapi/linux/psample.h |  1 +
>  net/psample/psample.c        | 12 +++++++++++-
>  3 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/psample.h b/include/net/psample.h
> index 0509d2d6be67..2503ab3c92a5 100644
> --- a/include/net/psample.h
> +++ b/include/net/psample.h
> @@ -25,6 +25,8 @@ struct psample_metadata {
>  	   out_tc_occ_valid:1,
>  	   latency_valid:1,
>  	   unused:5;
> +	u8 *user_cookie;

The code doesn't take ownership of this data.  It should probably
be a const pointer in this case.

This should also allow us to avoid a double copy first to the
psample_metadata and then to netlink skb, as users will know that
it is a const pointer and so they can hand the data directly.

> +	u32 user_cookie_len;
>  };
>  
>  struct psample_group *psample_group_get(struct net *net, u32 group_num);
> diff --git a/include/uapi/linux/psample.h b/include/uapi/linux/psample.h
> index 5e0305b1520d..1f61fd7ef7fd 100644
> --- a/include/uapi/linux/psample.h
> +++ b/include/uapi/linux/psample.h
> @@ -19,6 +19,7 @@ enum {
>  	PSAMPLE_ATTR_LATENCY,		/* u64, nanoseconds */
>  	PSAMPLE_ATTR_TIMESTAMP,		/* u64, nanoseconds */
>  	PSAMPLE_ATTR_PROTO,		/* u16 */
> +	PSAMPLE_ATTR_USER_COOKIE,

A comment would be nice.

>  
>  	__PSAMPLE_ATTR_MAX
>  };
> diff --git a/net/psample/psample.c b/net/psample/psample.c
> index a0cef63dfdec..9fdb88e01f21 100644
> --- a/net/psample/psample.c
> +++ b/net/psample/psample.c
> @@ -497,7 +497,8 @@ void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
>  		   nla_total_size(sizeof(u32)) +	/* group_num */
>  		   nla_total_size(sizeof(u32)) +	/* seq */
>  		   nla_total_size_64bit(sizeof(u64)) +	/* timestamp */
> -		   nla_total_size(sizeof(u16));		/* protocol */
> +		   nla_total_size(sizeof(u16)) +	/* protocol */
> +		   nla_total_size(md->user_cookie_len);	/* user_cookie */
>  
>  #ifdef CONFIG_INET
>  	tun_info = skb_tunnel_info(skb);
> @@ -596,6 +597,15 @@ void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
>  			goto error;
>  	}
>  #endif
> +	if (md->user_cookie && md->user_cookie_len) {
> +		int nla_len = nla_total_size(md->user_cookie_len);
> +		struct nlattr *nla;
> +
> +		nla = skb_put(nl_skb, nla_len);
> +		nla->nla_type = PSAMPLE_ATTR_USER_COOKIE;
> +		nla->nla_len = nla_attr_size(md->user_cookie_len);
> +		memcpy(nla_data(nla), md->user_cookie, md->user_cookie_len);
> +	}
>  
>  	genlmsg_end(nl_skb, data);
>  	psample_nl_obj_desc_init(&desc, group->group_num);