Re: howto disable default multiple device activation?

[Marc Herbert]

Marc Herbert a écrit :
> Stephen J. Gowdy a écrit :
>> When in the office I could previously 
>> do 50MB/s from my laptop. If I don't manually disable the wireless 
>> connection I only get 3MB/s. The routing table looks okay;
>>
>> [r...@antonia ~]# route
>> Kernel IP routing table
>> Destination Gateway Genmask Flags Metric RefUse Iface
>> 128.141.0.0 *   255.255.0.0 U 1  00 eth0
>> 128.141.0.0 *   255.255.0.0 U 2  00 wlan0
>> default default-route-2 0.0.0.0 UG0  00 eth0
>>
>> but somehow it slows everything down.
> 

> Your own routing table decides where you _send_ packets, not where
> you receive them. Basically you cannot tell others "please send to
> me using Fedex rather than UPS". Each IP node has its own routing
> table to decide independently

Oups sorry did not pay attention and realized that the two interfaces
are on the same network. In this case tricks like this should solve your
problem:

echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore

Also check arp_filter in the documentation here:


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Re: howto disable default multiple device activation?

[Marc Herbert]

Stephen J. Gowdy a écrit :
> When in the office I could previously 
> do 50MB/s from my laptop. If I don't manually disable the wireless 
> connection I only get 3MB/s. The routing table looks okay;
> 
> [r...@antonia ~]# route
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric RefUse Iface
> 128.141.0.0 *   255.255.0.0 U 1  00 eth0
> 128.141.0.0 *   255.255.0.0 U 2  00 wlan0
> default default-route-2 0.0.0.0 UG0  00 eth0
> 
> but somehow it slows everything down.

Your own routing table decides where you _send_ packets, not where you receive 
them. Basically you cannot tell others "please send to me using Fedex rather 
than UPS". Each IP node has its own routing table to decide independently (OK, 
full blown routers are admittedly able to discuss about their routing tables, 
but that really does not seem to be your case).

> Perhaps it decides to use wlan0 to send ACK packets?

In theory anything is possible but in practice I have never heard about an IP 
routing table handling TCP ACK specially...

I realize this does not answer your main question.

Cheers,

Marc

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Re: howto disable default multiple device activation?

[Stephen J. Gowdy]

Hi All,
This was a thread in November last year;

http://mail.gnome.org/archives/networkmanager-list/2008-November/msg00242.html

I'm in more-or-less the same situation as the original poster (except I 
don't have a girl friend to visit). When in the office I could previously 
do 50MB/s from my laptop. If I don't manually disable the wireless 
connection I only get 3MB/s. The routing table looks okay;


[r...@antonia ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric RefUse Iface
128.141.0.0 *   255.255.0.0 U 1  00 eth0
128.141.0.0 *   255.255.0.0 U 2  00 wlan0
default default-route-2 0.0.0.0 UG0  00 eth0

but somehow it slows everything down. Perhaps it decides to use wlan0 to 
send ACK packets?
	So to reiterate the question that wasn't answered in that thread: 
is there a way to turn this off so that once the Ethernet is connected it 
will automatically bring down the wireless network?


regards,

Stephen.

--
 /+-\
|Stephen J. Gowdy | CERN   Office: 8-1-11|
|http://cern.ch/gowdy/| CH-1211 Geneva 23|
| | Switzerland  |
|EMail: go...@cern.ch | Tel: +41 76 487 2215 |
 \+-/
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Re: Re: howto disable default multiple device activation?

[Alexander Sack]

On Wed, Nov 26, 2008 at 02:06:23PM +, [EMAIL PROTECTED] wrote:
> 
> >Do you have any reasons to hate it, 
> 
> I for instance would - although much less on a unixoid OS than on *eew* 
> Windoze. With multiple IP interfaces, there 
> is a strong tendency for nonunicast IP packets leaving the box via the 
> "wrong" interface - regardless of the source 
> address being written into the packet. So in general, I would see use cases 
> for not automatically having a wired and a 
> wireless interfaces active at the same time. Some Laptop firmwares even have 
> such a "Wifi XOR LAN" switch you can 
> activate in their BIOSs.
> 
> >The fastest device is always used for new TCP connections, so it's not like 
> >it'll slow anything down.
> 
> How does TCP know about an interface's speed? I would assume that it just 
> passes it's segments to the IP layer - 
> which will then forward packets according to what the routing table says.

NM tweaks the routing table in such a way that traffic is going
through faster devices. So TCP doesnt know; instead NM guesses what is
a the best interface.

 - Alexander

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AW: Re: howto disable default multiple device activation?

[[EMAIL PROTECTED]]

>Do you have any reasons to hate it, 

I for instance would - although much less on a unixoid OS than on *eew* 
Windoze. With multiple IP interfaces, there 
is a strong tendency for nonunicast IP packets leaving the box via the "wrong" 
interface - regardless of the source 
address being written into the packet. So in general, I would see use cases for 
not automatically having a wired and a 
wireless interfaces active at the same time. Some Laptop firmwares even have 
such a "Wifi XOR LAN" switch you can 
activate in their BIOSs.

>The fastest device is always used for new TCP connections, so it's not like 
>it'll slow anything down.

How does TCP know about an interface's speed? I would assume that it just 
passes it's segments to the IP layer - 
which will then forward packets according to what the routing table says.

>Here's a specific example why it's good: I'm connected through my wifi
>device only and have a bunch of open TCP connections (ssh, irc, ...).
>Then I need to transfer a large file from the local network. I plug in
>the cable (to make it faster) and start the transfer. 

The way you describe it, it sounds like a small setup witha single 
router/firewall towards the internet, with some 
(file) server on your internal LAN. So both your WiFi and LAN NICs will 
probably have addresses from the same subnet 
and use the same router/firewall to reach non-local networks. As soon as your 
LAN NIC is up, the routing table gets 
modified to reach the local LAN via that interface and maybe another default 
route, pointing to the same 
router/firewall. Like this, TCP connections to the outside world will survive 
and not seem out-of-state to that 
firewall. 

But what happens to your routing table once you get DHCP lease and default 
route from a completely different LAN? 
Will the new default route take precedence over the existing one? How do you 
prevent problems if your now dual-homed 
hosts needs to talk to hosts beyond the respective local subnet - on both 
interfaces simultaneously?  


>My point is, there's simply no reason to deactivate the previously active 
>device,

Yes. There are use cases where this is mandatory. As you pointed out - this 
needs to be taken care of by the 
administrator.

regards

Marc



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Re: howto disable default multiple device activation?

[Tambet Ingo]

On Tue, Nov 25, 2008 at 6:42 PM, Nikolaus Filus <[EMAIL PROTECTED]> wrote:
> Tony Espy wrote:
>> What about 3g?  Does it also stay connected when an Ethernet cable is
>> plugged in?  If so, couldn't that have financial implications to the
>> end-user?

Yes, 3g is handled the same way. Modems are different though, they are
not activated automatically, so if you remember to activate it when
you need it, you should remember to deactivate it as well. Plus,
(AFAIK) there's no financial implications when you have the modem
activated but not used for any traffic, so in case of active 3g device
and ethernet device, all the traffic goes through ethernet device
(unless it's specifically to the IP network of your modem).

> I'm responsible for a little office network and I never saw a use case for
> connection sharing in office environments. This is also one of those things I
> disallow for all users. In my eyes only some end users need this for their 
> home
> networks in rare cases.

If you so strongly feel it's bad, then it's your responsibility to
pre-configure your office laptops (machines with wifi devices) to have
a connection profile for your local wifi network with property
"connect automatically" not set.

> Besides that I always hated the default windows behaviour of acquiring IP
> adresses on all interfaces, what means everyone gets 1 ethernet and 1 wireless
> address. I don't want to have this on linux.

Do you have any reasons to hate it, other than "I have a gut feeling
that this is bad"? The fastest device is always used for new TCP
connections, so it's not like it'll slow anything down.

Here's a specific example why it's good: I'm connected through my wifi
device only and have a bunch of open TCP connections (ssh, irc, ...).
Then I need to transfer a large file from the local network. I plug in
the cable (to make it faster) and start the transfer. When it's done
(or whenever I feel like it), I unplug the cable. With 0.6 behavior,
I'd need to start my processes 3 times. My point is, there's simply no
reason to deactivate the previously active device, it's used until
it's necessary and then just stays there until it's needed again.

Tambet
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Re: howto disable default multiple device activation?

[Nikolaus Filus]

Hi,

Tony Espy wrote:
> Dan Williams wrote:
>> On Tue, 2008-11-25 at 09:50 +0100, Nikolaus Filus wrote:
>>> Hello,
>>>
>>> with the switch to Intrepid I finally got the long awaited NM 0.7 features 
>>> and
>>> although it incorporates several enhancements I would really like to set it 
>>> back
>>> to the 0.6 behaviour of 1 active (physical) device.
>> Note that this behavior would prohibit Internet connection sharing and
>> instant failover when you pull the cable or whatever.
> 
> Dan --
> 
> To follow-up on the original question, is it possible to restore the 
> single active connection behavior of NM 0.6.6 w/out changing code?
> 
> In my opinion, unless someone is actively using connection sharing, 
> keeping Wi-Fi connected while Ethernet is active is just burning a slot 
> in the AP that someone else could be utilizing...
> 
> What about 3g?  Does it also stay connected when an Ethernet cable is 
> plugged in?  If so, couldn't that have financial implications to the 
> end-user?

Thank you for sharing my point of view.

I'm responsible for a little office network and I never saw a use case for
connection sharing in office environments. This is also one of those things I
disallow for all users. In my eyes only some end users need this for their home
networks in rare cases.
Besides that I always hated the default windows behaviour of acquiring IP
adresses on all interfaces, what means everyone gets 1 ethernet and 1 wireless
address. I don't want to have this on linux.

I have no problem with a short re-orientation period when switching from wlan to
ethernet or the other way round.

Just my 2¢

Nikolaus
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Re: howto disable default multiple device activation?

[Tony Espy]

Dan Williams wrote:

On Tue, 2008-11-25 at 09:50 +0100, Nikolaus Filus wrote:

Hello,

with the switch to Intrepid I finally got the long awaited NM 0.7 features and
although it incorporates several enhancements I would really like to set it back
to the 0.6 behaviour of 1 active (physical) device.


Note that this behavior would prohibit Internet connection sharing and
instant failover when you pull the cable or whatever.


Dan --

To follow-up on the original question, is it possible to restore the 
single active connection behavior of NM 0.6.6 w/out changing code?


In my opinion, unless someone is actively using connection sharing, 
keeping Wi-Fi connected while Ethernet is active is just burning a slot 
in the AP that someone else could be utilizing...


What about 3g?  Does it also stay connected when an Ethernet cable is 
plugged in?  If so, couldn't that have financial implications to the 
end-user?


Ciao,
/tony
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Re: howto disable default multiple device activation?

[Dan Williams]

On Tue, 2008-11-25 at 09:50 +0100, Nikolaus Filus wrote:
> Hello,
> 
> with the switch to Intrepid I finally got the long awaited NM 0.7 features and
> although it incorporates several enhancements I would really like to set it 
> back
> to the 0.6 behaviour of 1 active (physical) device.

Note that this behavior would prohibit Internet connection sharing and
instant failover when you pull the cable or whatever.

> My current current use case is:
> 
> office - work on ethernet only
> suspend, go home
> home - work wireless only
> suspend, visit girl friend
> home2 - work wireless only
> ...
> 
> After every resume NM seems very confused about its location and shows a lot 
> of
> old entries in the applet. Sometimes I see SSIDs from all 3 locations in the

The old entries are sent from the supplicant or the kernel driver.  I
have verified that NetworkManager itself correctly clears the scan list
of the device when it is told to sleep, and that on resume when it
queries the supplicant for scan results, it gets a lot of older ones.
So this bug is elsewhere.

> list and although I'm already connected to ethernet NM tries to associate with
> an old SSID, times out and prompts for a new WPA key.
> 
> I tried to disable automatic connection to known networks, but I didn't find a
> switch for "exclusive connection" - this way is annoying, as I would have to
> redo this for every new network. I'm looking for a global "1 physical only,
> prefer wired over wireless".

Again, exclusive active device prohibits some key features of
NetworkManager 0.7, and most of the time shouldn't be a problem.  I
think the annoying behavior you're seeing is simply a bug in the
supplicant or driver that needs to be fixed, not a symptom of multiple
device support.

Dan

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