From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [PATCH v2 0/2] Tracepoint for tcp retransmission Date: Mon, 06 Feb 2012 11:18:09 -0500 Message-ID: <1328545089.2200.13.camel@gandalf.stny.rr.com> References: <20120120.135028.1359677274445012541.davem@davemloft.net> <65795E11DBF1E645A09CEC7EAEE94B9CB8D3EA7B@USINDEVS02.corp.hds.com> <20120204142823.GA7000@neilslaptop.think-freely.org> <20120204155807.GA2657@nuttenaction> <20120204200937.GA2670@neilslaptop.think-freely.org> <20120205125325.GA31578@elastic.org> <20120205191708.GA5337@neilslaptop.think-freely.org> <20120205200428.GB2816@nuttenaction> <20120206013247.GA5681@neilslaptop.think-freely.org> <20120206152019.GG27935@redhat.com> <20120206155305.GB3620@hmsreliant.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit Cc: "Frank Ch. Eigler" , Hagen Paul Pfeifer , "Frank Ch. Eigler" , Satoru Moriya , David Miller , "netdev@vger.kernel.org" , "tgraf@infradead.org" , "stephen.hemminger@vyatta.com" , "eric.dumazet@gmail.com" , Seiji Aguchi , fche@sourceware.org, mathieu.desnoyers@polymtl.ca To: Neil Horman Return-path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:59693 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755247Ab2BFQSQ (ORCPT ); Mon, 6 Feb 2012 11:18:16 -0500 In-Reply-To: <20120206155305.GB3620@hmsreliant.think-freely.org> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2012-02-06 at 10:53 -0500, Neil Horman wrote: > Yes, that was his point. Mine was that, given Satoru's needs, a netfilter hook > provides 90% of what they need (as its been described here). If you're > unfamiliar with them, netfilter hooks are those standard points in the network > input/output/forwarding paths at which we can watch and maniupulate network > traffic. They're what iptables/ip6tables/ebtables/etc use to do everything they > do. I'm suggesting that they use those existing hooks to monitor outgoing > traffic for whatever information they want (in this case retransmitted unacked > tcp sequence numbers). Or whatever else their interested in. > > As for the other 10% (recording failed retransmits, which don't generate > traffic), we have existing tracepoints that can be used. I haven't looked at the details here, but I'm wondering if netfilter could benefit from static_branch() calls (aka jump-labels). I'm sure selinux could too. Basically, when netfilter is disabled, the fast path would just include a nop, with no if() branch testing at all. When you enable netfilters, it would then add a jmp to the code that actually does the tests. -- Steve