From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC][PATCH 1/3] net: per skb control messages Date: Thu, 24 Jul 2008 14:58:11 -0700 Message-ID: <20080724145811.2d2b9ec6@extreme> References: <200807241922.57361.opurdila@ixiacom.com> <20080724.132821.212118602.davem@davemloft.net> <200807250049.46939.opurdila@ixiacom.com> <20080724.145600.30988015.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: opurdila@ixiacom.com, herbert@gondor.apana.org.au, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([216.93.170.194]:48686 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751864AbYGXV6N (ORCPT ); Thu, 24 Jul 2008 17:58:13 -0400 In-Reply-To: <20080724.145600.30988015.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 24 Jul 2008 14:56:00 -0700 (PDT) David Miller wrote: > From: Octavian Purdila > Date: Fri, 25 Jul 2008 00:49:46 +0300 > > > On Thursday 24 July 2008, David Miller wrote: > > > > > Adding new fields to struct sk_buff that take up space is generally > > > not allowed unless the new field adds substantially to the benefit of > > > a large group of users of Linus. > > > > > > I don't think that applied here for this hw-tstamps stuff. > > > > What about the approach proposed in the patch? Is it ok to add a pointer which > > may resolve other future similar issues? > > Traversing the list and maintaining the reference counting and sharing > issues is expensive and error prone. > > This is what OpenBSD uses for their IPSEC state attached to MBUFs and > it's a nightmare. > > We have a timestamp in the SKB already, why don't you simply override > it when your feature is enable and set a single flag bit that > indicates you used a HW timestamp to set that timestamp? How hard would it be to add PLL support to use same kind of timestamp. Enlist the help of some NTP/clock experts to help.