From owner-freebsd-hackers Fri Sep 17 16:16:52 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from proxy2.ba.best.com (proxy2.ba.best.com [206.184.139.14]) by hub.freebsd.org (Postfix) with ESMTP id 3FDA415567; Fri, 17 Sep 1999 16:16:21 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com ([209.157.86.2]) by proxy2.ba.best.com (8.9.3/8.9.2/best.out) with ESMTP id QAA04468; Fri, 17 Sep 1999 16:12:41 -0700 (PDT) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id NAA25509; Mon, 13 Sep 1999 13:17:56 -0700 (PDT) (envelope-from dillon) Date: Mon, 13 Sep 1999 13:17:56 -0700 (PDT) From: Matthew Dillon Message-Id: <199909132017.NAA25509@apollo.backplane.com> To: Garrett Wollman Cc: Bosko Milekic , Stas Kisel , avalon@coombs.anu.edu.au, freebsd-hackers@FreeBSD.ORG, freebsd-security@FreeBSD.ORG Subject: Re: mbuf shortage situations (followup) References: <199909091447.SAA24055@sonet.crimea.ua> <199909131840.OAA31048@khavrinen.lcs.mit.edu> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :In 4.3, the code was able to deal with cluster allocation failing. We :have a somewhat different situation now, because many network :interface devices have less-flexible DMA mechanisms which don't allow :packet reception into non-contiguous buffers, so we need to have at :least a certain number of clusters available for this purpose. : :-GAWollman : :-- :Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same This is an interrupt level mechanism. The mbuf code is *already* allowed to (and does) return NULL in this case so I don't think it applies to the problem under discussion. The case that is causing the panics is with the non-interrupt mbuf allocation mechanism. Specifically, the case where M_WAIT is used. The second problem under discussion, which really ought to be separated out from the mbuf panic problem, is the potential for a deadlock or denial of service attack when the system is attacked in a manner that eats all available mbufs. :wollman@lcs.mit.edu | O Siem / The fires of freedom :Opinions not those of| Dance in the burning flame -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message