From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH net-next] net: add network device notifier trace points Date: Wed, 19 Dec 2018 17:40:49 +0100 Message-ID: <20181219174049.36952782@redhat.com> References: <20181219022706.10611-1-sthemmin@microsoft.com> <20181219083643.7f724e59@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , netdev@vger.kernel.org, Stephen Hemminger , Alexei Starovoitov , Arnaldo Carvalho de Melo , Steven Rostedt , brouer@redhat.com To: Daniel Borkmann Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33135 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727383AbeLSQk5 (ORCPT ); Wed, 19 Dec 2018 11:40:57 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 19 Dec 2018 16:46:05 +0100 Daniel Borkmann wrote: > Hmm, why not just doing something as in your example below with napi_poll() > where you pass in the napi pointer, and then use bpf_probe_read_str() on > ctx->dev for fetching the name? At least there this should work and should > be okay given it's rather slow-path event. > > > [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/samples/bpf/napi_monitor_kern.c#L34-L130 I didn't try to use bpf_probe_read_str() in [1], but that is also not what I want in my use-case. I don't want the name, but the ifindex to filter on, as it will be faster. My use-case is allowing my napi_monitor program to filter on a specific net_device, inside the kernel via BPF. E.g. this didn't work: bpf_probe_read(&ifindex, 4, &ctx->napi->dev->ifindex); Perhaps you know how I can do this deref correctly? My napi_monitor use-case is not a slow-path event, even-though in optimal cases we should handle 64 packets per tracepoint invocation, but I'm using this for 100G NICs with >20Mpps. And I mostly use the tool when something looks wrong and I don't see 64 packet bulks, which is also why I detect when this gets invoked from idle task or from ksoftirqd. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer