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hotpluggable member of a bridge

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  hotpluggable member of a bridge Stefan Monnier <monnier@iro.umontreal.ca> - 2017-01-05 04:40 +0100
    Re: hotpluggable member of a bridge Nicolas George <george@nsup.org> - 2017-01-05 10:10 +0100
      Re: hotpluggable member of a bridge <tomas@tuxteam.de> - 2017-01-05 10:30 +0100
        Re: hotpluggable member of a bridge Michael Biebl <biebl@debian.org> - 2017-01-05 16:30 +0100
          Re: hotpluggable member of a bridge Sven Hartge <sven@svenhartge.de> - 2017-01-06 03:00 +0100
            Re: hotpluggable member of a bridge <tomas@tuxteam.de> - 2017-01-06 09:40 +0100
      Re: hotpluggable member of a bridge Stefan Monnier <monnier@iro.umontreal.ca> - 2017-01-05 16:30 +0100
        Re: hotpluggable member of a bridge Nicolas George <george@nsup.org> - 2017-01-05 16:40 +0100
          Re: hotpluggable member of a bridge Stefan Monnier <monnier@IRO.UMontreal.CA> - 2017-01-05 18:30 +0100
          Re: Congratulations Danielle , Your Roof is Covered - FREE!GYfb Danielle Gregory <danielle.k.gregory@gmail.com> - 2017-01-05 22:10 +0100
          Re: Congratulations Aileen , Your Roof is Covered - FREE!PHYi tazzygirl tazzygirl <saratazmtz77@gmail.com> - 2017-01-05 22:10 +0100
          RE: Congratulations Emmanuel , Your Roof is Covered - FREE!44OO Jennyetta Washington <manolofimbres@gmail.com> - 2017-01-05 22:20 +0100
    Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-05 17:10 +0100
      Re: hotpluggable member of a bridge Joshua Schaeffer <jschaeffer0922@gmail.com> - 2017-01-05 17:20 +0100
        Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-05 17:40 +0100
          Re: hotpluggable member of a bridge Joshua Schaeffer <jschaeffer0922@gmail.com> - 2017-01-05 18:10 +0100
          Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-05 22:20 +0100
            Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-05 22:30 +0100
            Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-05 22:40 +0100
              Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-08 16:50 +0100
                Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-08 17:20 +0100
                  Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-08 18:00 +0100
      Re: hotpluggable member of a bridge Stefan Monnier <monnier@iro.umontreal.ca> - 2017-01-06 02:20 +0100
        Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-06 12:40 +0100
          Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-06 13:20 +0100
            Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-08 17:00 +0100
              Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-08 17:20 +0100
                Re: hotpluggable member of a bridge Reco <recoverym4n@gmail.com> - 2017-01-08 17:30 +0100
                Re: hotpluggable member of a bridge Pascal Hambourg <pascal@plouf.fr.eu.org> - 2017-01-08 17:30 +0100
          Re: hotpluggable member of a bridge Stefan Monnier <monnier@iro.umontreal.ca> - 2017-01-06 22:50 +0100
    Re: hotpluggable member of a bridge Jonathan Dowland <jmtd@debian.org> - 2017-01-06 18:20 +0100

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#176455

	Hi.

On Sun, 8 Jan 2017 16:48:02 +0100
Pascal Hambourg <pascal@plouf.fr.eu.org> wrote:

> Le 05/01/2017 à 22:36, Reco a écrit :
> >
> > Pascal Hambourg <pascal@plouf.fr.eu.org> wrote:
> >
> >>> Bridged interfaces retain their MACs, so they would get different IPv6
> >>> ULAs, which are provided by radvd from the different host.
> >>
> >> Not if they are bridged before they are brought UP
> >
> > I'm not that familiar with openvswitch to make claims about the order
> > in which an interface brought up and bridged.
> >
> > If you have such knowledge then feel free to share it with the list
> > please.
> 
> Actually I had in mind the behaviour of Linux bridge, not openvswitch. I 
> have no knowledge nor experience with openvswitch. However, I can see 
> that the openvswitch package adds a script in /etc/network/if-pre-up.d, 
> so it is likely that the interface is bridged before it is brought up.

Seems to be the case with openvswitch indeed. I conclude that from
(failed) experiment involving openvswitch bridge, hostapd, wireless
interface and a plain ethernet one. hostapd was unoperational unless I
forced the bugger to start up first, and add an interface to the
bridge second. 

Reco

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#176458

Le 08/01/2017 à 17:15, Reco a écrit :
>
> Pascal Hambourg <pascal@plouf.fr.eu.org> wrote:
>>
>> Actually I had in mind the behaviour of Linux bridge, not openvswitch. I
>> have no knowledge nor experience with openvswitch. However, I can see
>> that the openvswitch package adds a script in /etc/network/if-pre-up.d,
>> so it is likely that the interface is bridged before it is brought up.
>
> Seems to be the case with openvswitch indeed. I conclude that from
> (failed) experiment involving openvswitch bridge, hostapd, wireless
> interface and a plain ethernet one. hostapd was unoperational unless I
> forced the bugger to start up first, and add an interface to the
> bridge second.

That reminds me of my own experiments with hostapd and the Linux bridge.
Hostapd needed an extra parameter to declare the bridge, and the Linux 
bridge refused to add the wireless interface until the interface mode 
was changed to master mode (AP), so hostapd had to be started first.

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#176351

> But, it all changes if you replace conventional bridge with
> openvswitch, which *can* add new interfaces (ports as they call it) to
> its own bridges dynamically *and* it can be configured via interfaces(5).

Interesting.  Would it work if the IP address of the bridge is acquired
dynamically via DHCP?

E.g. at boot, the bridge contains only eth0, but it can't get an IP
address because there's no DHCP server on that network (or maybe eth0
is not even connected to anything yet).

Later, someone connects an ethernet dongle that appears as usb0 and that
one should be added to br0 and since it is connected to a network that
has a DHCP server, I'd want the br0 to acquire an IP at that moment.


        Stefan

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#176360

	Hi.

On Thu, 05 Jan 2017 20:17:39 -0500
Stefan Monnier <monnier@iro.umontreal.ca> wrote:

> > But, it all changes if you replace conventional bridge with
> > openvswitch, which *can* add new interfaces (ports as they call it) to
> > its own bridges dynamically *and* it can be configured via interfaces(5).
> 
> Interesting.  Would it work if the IP address of the bridge is acquired
> dynamically via DHCP?

Yes, it should. DHCP is L4, IP is L3 and openvswitch cares about L2
mostly.


> E.g. at boot, the bridge contains only eth0, but it can't get an IP
> address because there's no DHCP server on that network (or maybe eth0
> is not even connected to anything yet).
> 
> Later, someone connects an ethernet dongle that appears as usb0 and that
> one should be added to br0 and since it is connected to a network that
> has a DHCP server, I'd want the br0 to acquire an IP at that moment.

It should be possible to obtain a single IPv4 on a bridge even in this
case *if* you run dhclient on a bridge (not on the ports) the whole
time.

To speedup obtaining a lease you should probably restart dhclient on
usb0 addition/removal.

Reco

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#176362

On Fri, 6 Jan 2017 14:30:53 +0300
Reco <recoverym4n@gmail.com> wrote:

> 	Hi.
> 
> On Thu, 05 Jan 2017 20:17:39 -0500
> Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
> > > But, it all changes if you replace conventional bridge with
> > > openvswitch, which *can* add new interfaces (ports as they call it) to
> > > its own bridges dynamically *and* it can be configured via interfaces(5).
> > 
> > Interesting.  Would it work if the IP address of the bridge is acquired
> > dynamically via DHCP?
> 
> Yes, it should. DHCP is L4, IP is L3 and openvswitch cares about L2
> mostly.

Self-correction. DHCP is L7.

Reco

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#176453

Le 06/01/2017 à 13:15, Reco a écrit :
>>
>> DHCP is L4, IP is L3 and openvswitch cares about L2
>> mostly.
>
> Self-correction. DHCP is L7.

Why ? DHCP deals with IP configuration, so I'd rather classify it as 
part of layer 3, with IP and ICMP. AFAIK, it does not provide any 
service to any application but to the IP layer itself, just like ICMP.

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#176454

	Hi.

On Sun, 8 Jan 2017 16:59:39 +0100
Pascal Hambourg <pascal@plouf.fr.eu.org> wrote:

> Le 06/01/2017 à 13:15, Reco a écrit :
> >>
> >> DHCP is L4, IP is L3 and openvswitch cares about L2
> >> mostly.
> >
> > Self-correction. DHCP is L7.
> 
> Why ? DHCP deals with IP configuration, so I'd rather classify it as 
> part of layer 3, with IP and ICMP. AFAIK, it does not provide any 
> service to any application but to the IP layer itself, just like ICMP.

[1] lists is as an application level protocol. My original thought was
UDP, hence L4. 

Furthermore, there are lots of dhcp options (ntp-server,
local-proxy-config to name a few that are actually used) that deal with
client's configuration that's not related to IP configuration directly. 

Reco

[1] https://en.wikipedia.org/wiki/DHCP

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#176456

On Sun, 8 Jan 2017 19:10:31 +0300
Reco <recoverym4n@gmail.com> wrote:

> Furthermore, there are lots of dhcp options (ntp-server,
> local-proxy-config to name a few that are actually used) that deal with
> client's configuration that's not related to IP configuration directly. 

And dns-servers, of course. Should not forget about that one.

Reco

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#176457

Le 08/01/2017 à 17:10, Reco a écrit :
>
> Pascal Hambourg <pascal@plouf.fr.eu.org> wrote:
>
>> Le 06/01/2017 à 13:15, Reco a écrit :
>>>>
>>>> DHCP is L4, IP is L3 and openvswitch cares about L2
>>>> mostly.
>>>
>>> Self-correction. DHCP is L7.
>>
>> Why ? DHCP deals with IP configuration, so I'd rather classify it as
>> part of layer 3, with IP and ICMP. AFAIK, it does not provide any
>> service to any application but to the IP layer itself, just like ICMP.
>
> [1] lists is as an application level protocol.

Wikipedia is not an authoritative source.
However RFC1122 lists BOOTP, the predecessor of DHCP, among the support 
protocols of the application layer. So be it...

> My original thought was UDP, hence L4.

Common mistake. A protocol layer is defined by the service it provides, 
not the protocol layer it is based upon. For example NDP is based on 
ICMPv6 (network layer), itself based on IPv6 (also network layer) but is 
in the link layer.

> Furthermore, there are lots of dhcp options (ntp-server,
> local-proxy-config to name a few that are actually used) that deal with
> client's configuration that's not related to IP configuration directly.

Agreed.

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#176392

> To speedup obtaining a lease you should probably restart dhclient on
> usb0 addition/removal.

Right, that's basically the issue.  I know I can write all this with
enough post-up scripting in /etc/network/interfaces (or even udev
.rules files), but I was hoping there was something already written
which would then take care of all those various cases.


        Stefan

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#176380

[Multipart message — attachments visible in raw view] — view raw

On Wed, Jan 04, 2017 at 10:34:16PM -0500, Stefan Monnier wrote:
> I have a bridge interface `br0` which usually contains jut `eth0` but
> occasionally also needs to contain `usb0`, which is an ethernet-dongle
> kind of thing.
> 
> How do I setup /etc/network/interfaces for that?
> 
> Currently, I just setup everything "manually": `br0` is setup `static`,
> and `usb0` is setup as `manual` with post-up scripts that add it to
> the bridge.

Fairly sure I've done this with "allow-hotplug usb0" rather than manual
and putting some brctl commands in the "post-up" stanza for usb0, e.g.

	post-up brctl addif br0 usb0

(and possibly corresponding for pre-down) but I have lost the specifics.


-- 
Jonathan Dowland
Please do not CC me, I am subscribed to the list.

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