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

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Date: Mon, 8 Apr 2024 21:28:23 +0200
From: Adrian Moreno <amorenoz@...hat.com>
To: Ilya Maximets <i.maximets@....org>, netdev@...r.kernel.org
Cc: 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



On 4/8/24 15:19, Ilya Maximets wrote:
> [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.
> 

Yep. You're right.


>> +	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.
> 

Definitely.

>>   
>>   	__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);
>