Subject: Re: Network RX per process per interface statistics

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 24 Mar 2023 13:19:58 -0700

On 03/24, Kamil Zaripov wrote:
> Hi everyone,

> I trying to make a BPF program that can collect per process per interface  
> statistics of network data consumption. Right now most difficult part for  
> me is RX traffic.

> I have tried to find some point in the sk_buff's way up to network stack  
> where I can extract info both about the network interface which captured  
> package and the process that will consume this data but failed. So I have  
> to listen events in several points and somehow merge collected data.

> The last point I found at which sk_buff still contains information about  
> network device that captured this sk_buff is netif_receive_skb  
> tracepoint. The first point where I can found information about process  
> is protocol's rcv handlers (like tcp_v4_do_rcv). But I have some  
> questions, to finish my program:

> 1. It seems that sk_buff modifies during handling, so how can I "match"  
> sk_buff with same data in netif_receive_skb and in tcp_v4_do_rcv?

By "modifies" - do you mean the payload/headers? You can probably use
the skb pointer address as a unique identifier to connect across different
tracepoints?

> 2. Maybe there is some good point where I can attach listener and where I  
> can extract both process and interface info for each package?

Nothing pops to my mind. But I think that if you store skbaddr=dev from
netif_receive_skb, you should be able to look this up at a later point
where you know skb->process association?

> Regards
> Zaripov Kamil.