On Thu, Dec 13, 2012 at 11:05 AM, Tomas Pospisek <tpo@xxxxxxxxxxxxx> wrote: > On Thu, 13 Dec 2012, Michael Kerrisk (man-pages) wrote: > >> Do you have a revised version of this page taking into account the >> comments of Eric and Pavel? > > > No I don't. I got trampled down by a horde of rabid real life tasks and am > slowly recovering from it. I'll make a new effort at some point, Eric's and > Pavel's emails still have their cosy place in my INBOX and are waiting to be > groomed. Good, because I would be happy to add that page to the set. MfG, Michael >> On Mon, Nov 5, 2012 at 5:11 AM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> >> wrote: >>> >>> Pavel Emelyanov <xemul@xxxxxxxxxxxxx> writes: >>> >>>> On 11/04/2012 04:35 AM, Eric W. Biederman wrote: >>>>> >>>>> Tomas Pospisek <tpo@xxxxxxxxxxxxx> writes: >>>>> >>>>>> Hi again Michael, Pavel, Eric and mailing list >>>>>> >>>>>> (Cc: to Eric, Pavel and Linux Netdev List on behalf of Michael asking >>>>>> for comment) >>>>>> >>>>>> Here's the revised veth(4) man page (the inline replies to Michael's >>>>>> critique are following the man page): >>>>>> >>>>>> ******************************************************************** >>>>>> .\" Copyright (c) 2012 Tomáš Pospíšek (tpo_deb@xxxxxxxxxxxxx), >>>>>> .\" Fri, 03 Nov 2012 22:35:33 +0100 >>>>>> .\" >>>>>> .\" This is free documentation; you can redistribute it and/or >>>>>> .\" modify it under the terms of the GNU General Public License as >>>>>> .\" published by the Free Software Foundation; either version 2 of >>>>>> .\" the License, or (at your option) any later version. >>>>>> .\" >>>>>> .\" The GNU General Public License's references to "object code" >>>>>> .\" and "executables" are to be interpreted as the output of any >>>>>> .\" document formatting or typesetting system, including >>>>>> .\" intermediate and printed output. >>>>>> .\" >>>>>> .\" This manual is distributed in the hope that it will be useful, >>>>>> .\" but WITHOUT ANY WARRANTY; without even the implied warranty of >>>>>> .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>>>> .\" GNU General Public License for more details. >>>>>> .\" >>>>>> .\" You should have received a copy of the GNU General Public >>>>>> .\" License along with this manual; if not, write to the Free >>>>>> .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA >>>>>> 02111, >>>>>> .\" USA. >>>>>> .\" >>>>>> .\" >>>>>> .TH veth 4 2012-11-02 "Linux" "Linux Programmer's Manual" >>>>>> .SH NAME >>>>>> veth \- Virtual Ethernet Device >>>>>> .SH DESCRIPTION >>>>>> The >>>>>> .B veth >>>>>> devices are virtual Ethernet devices. >>>>>> >>>>>> They can act as tunnels between network namespaces to create >>>>>> a bridge to a physical network device in another namespace, but >>>>>> can also be used as standalone network devices. >>>>> >>>>> >>>>> As far as understanding and using them I think this text is a bit weak. >>>>> Perhaps something like: >>>>> >>>>> ip link add type veth creates a pair of directly connected ethernet >>>>> devices. What is transmited on one device is immediately received on >>>>> the other device. When either devices is down the link state of the >>>>> pair is down. veth device pairs are useful for combining the network >>>>> facilities of the kernel together in interesting ways. A particularly >>>>> interesting use case is to place one end of a veth pair in one network >>>>> namespace and another end of the veth pair in another network namespace >>>>> allowing communication between network namespaces. >>>> >>>> >>>> Ack >>>> >>>>> ethtool can be used to test if a networking device is a veth device, >>>>> and to find the peer network interface. >>>> >>>> >>>> This one requires clarification, I think. The ethtool will report you >>>> just and ifindex of the peer, and the caller can do something useful >>>> with it if the peer is still in the same net namespace as the original >>>> device. But how would you find the peer device in case it already sits >>>> in some other network namespace? >>> >>> >>> Until just recently the ifindex of networking devices was universally >>> unique so finding the other end of the device could be done with a brute >>> force search through network namespaces. Even without a guarantee of >>> global uniqueness in the ifindex performing a bidirectional comparison >>> of the return ifindicies of veth devices can give a strong hint that you >>> have found both ends of the tunnel. >>> >>> For checkpoint/restart we may need to implement something better at some >>> point. >>> >>> >>> Eric >>> >> >> >> >> -- >> Michael Kerrisk >> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ >> Author of "The Linux Programming Interface"; http://man7.org/tlpi/ >> > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
