From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.mhcomputing.net (master.mhcomputing.net [74.208.228.170]) by dpdk.org (Postfix) with ESMTP id AC82C2716 for ; Mon, 14 Dec 2015 23:36:15 +0100 (CET) Received: by mail.mhcomputing.net (Postfix, from userid 1000) id 81C2F419; Mon, 14 Dec 2015 17:36:13 -0500 (EST) Date: Mon, 14 Dec 2015 17:36:13 -0500 From: Matthew Hall To: Kyle Larose Message-ID: <20151214223613.GC21163@mhcomputing.net> References: <98CBD80474FA8B44BF855DF32C47DC358AF758@smartserver.smartshare.dk> <20151214182931.GA17279@mhcomputing.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: dev@dpdk.org, Morten B Subject: Re: [dpdk-dev] tcpdump support in DPDK 2.3 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 14 Dec 2015 22:36:15 -0000 On Mon, Dec 14, 2015 at 04:29:41PM -0500, Kyle Larose wrote: > I've seen lots of ideas and options tossed around which would solve > some or all of the above items, but nobody actually committing to > anything. What can we do to actually agree on a solution to go and > implement? I'm relatively new to the community, so I don't really know > how this stuff works. Do people typically form a working group where > they go off and discuss the problem, and then come back to the main > community with a proposal? Or do people just submit RFCs independently > with their own ideas? > > Thanks, > Kyle I am getting the impression of a misplaced sense of urgency / panic. I don't think anybody came up with a reason why we have to answer all these questions tremendously quickly. It will take some more time, particularly with the holidays, for the developers to finish the last bug fixes on the current release before they have time to discuss 2.3 features. When that happens, someone working on DPDK full time will be identified as the leader for the feature, that will lead the effort on PCAP, and help us formulate the plan. Until then, what we really could use at this point is not necessarily more writings and speculation, but an answer on some key tech questions, particularly from some kernel guys: 1) How do we get the pcap filter string and/or BPF opcode vector from libpcap / tcpdump / tshark / wireshark, into the DPDK application? There we can compile it using the user-space bpfjit, so we can filter the packets at very high speeds and not end up breaking everything doing a ton of stupid copies when somebody does a capture of one flow on his i40e device or such. libpcap is crappy about this, as it sends it all over syscalls which are always assuming the kernel is on the other end, which is a bad assumption on their part but many decades old and not so easy to fix. 2) How do we get the matched packets back out to the extcap or libpcap? From what I saw extcap is tshark / wireshark only, which are 1) GPL licensed in various ways, 2) not as widely used as libpcap. So using only extcap might be kind of crappy. 3) For libpcap to work, maybe it will help if some of our kernel guys can help us find out how to "detect" the kernel put a BPF capture filter onto a TUN / TAP interface, and copy that filter to the DPDK app. Then, take any matched packets and write them back onto the TUN / TAP. This would also be super efficient and work with more off-the-shelf tools besides just tshark / wireshark. If we don't find the answers for these items I don't think we have a path to a working solution, forgetting about all the nice-to-have points such as UX issues, troubleshooting, debugging, etc. Matthew.