From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH net-next RFC 1/5] net-timestamp: no-payload option Date: Fri, 9 Jan 2015 12:55:56 -0800 Message-ID: References: <1420824719-28848-1-git-send-email-willemb@google.com> <1420824719-28848-2-git-send-email-willemb@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Network Development , "David S. Miller" , Richard Cochran , Eric Dumazet To: Willem de Bruijn Return-path: Received: from mail-la0-f41.google.com ([209.85.215.41]:59252 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757485AbbAIU4S (ORCPT ); Fri, 9 Jan 2015 15:56:18 -0500 Received: by mail-la0-f41.google.com with SMTP id hv19so16466386lab.0 for ; Fri, 09 Jan 2015 12:56:16 -0800 (PST) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Jan 9, 2015 at 12:33 PM, Willem de Bruijn wrote: > On Fri, Jan 9, 2015 at 3:02 PM, Andy Lutomirski wrote: >> On Fri, Jan 9, 2015 at 11:47 AM, Willem de Bruijn wrote: >>> On Fri, Jan 9, 2015 at 2:43 PM, Andy Lutomirski wrote: >>>> On Fri, Jan 9, 2015 at 9:31 AM, Willem de Bruijn wrote: >>>>> From: Willem de Bruijn >>>>> >>>>> Add timestamping option SOF_TIMESTAMPING_OPT_TSONLY. For transmit >>>>> timestamps, this loops timestamps on top of empty packets. >>>>> >>>>> Doing so reduces the pressure on SO_RCVBUF. Payload inspection and >>>>> cmsg reception (aside from timestamps) are no longer possible. This >>>>> works together with a follow on patch that allows administrators to >>>>> only allow tx timestamping if it does not loop payload or metadata. >>>> >>>> If this loses IP_PKTINFO, that will be a bit unfortunate. >>>> >>> >>> If it doesn't, then we might as well loop the entire payload. For applications >>> that need pktinfo or other cmsg, do not select the option. >> >> Right, but it loses the ability to get the ifindex if the sysctl is >> set to the conservative option, which I don't think is desirable. > > Understood. I just find the alternative, where the no-data policy is > weakened by exceptions, even less desirable. That makes it > harder to explain what the sysctl/option do and what the security > implications are. Agreed. If there was no-payload but not no-cmsg, then it would be a nice middle ground, but I guess that's bad for some reason involving accounting? --Andy -- Andy Lutomirski AMA Capital Management, LLC