Date: Fri, 29 Aug 2008 18:41:45 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Sam Leffler <sam@freebsd.org> Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, gnn@freebsd.org, net@freebsd.org Subject: Re: Small patch to multicast code... Message-ID: <20080829164145.GA47030@onelab2.iet.unipi.it> In-Reply-To: <48B8248A.3060103@freebsd.org> References: <48AF330B.4010802@FreeBSD.org> <m28wuohfm5.wl%gnn@neville-neil.com> <20080825190207.GA73478@zibbi.meraka.csir.co.za> <20080825194038.GA75840@zibbi.meraka.csir.co.za> <m2y72jx33z.wl%gnn@neville-neil.com> <20080826144130.S66593@maildrop.int.zabbadoz.net> <m2abezwojl.wl%gnn@neville-neil.com> <48B4A62D.3080300@freebsd.org> <20080829162853.GB46693@onelab2.iet.unipi.it> <48B8248A.3060103@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Aug 29, 2008 at 09:32:10AM -0700, Sam Leffler wrote: > Luigi Rizzo wrote: ... > >and to be more explicit - the result of m_pullup is that > >the number of bytes specified as m_pullup argument are in > >a private piece of memory -- the 'data' region within the mbuf -- so > >you can freely play with them without trouble. > > > >That is why i suggested to just increase the argument to m_pullup > >by the size of the udp header so one can overwrite the checksum > >within the mbuf without touching the shared part in the cluster > >(if any). > > > > Hmm, never considered the m_pullup guaranteed a private copy (but I see > it in the code). The original semantics were just that the data was > contiguous. funny, i thought the guarantee of a writable copy was also part of the original semantics :) cheers luigi
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20080829164145.GA47030>