[gentoo-user] the user mode linux can't access network..

[gentoo-user] the user mode linux can't access network..

[fei huang]

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I have my user mode kernel running on my gentoo box following the gentoo's
guide: http://www.gentoo.org/doc/en/uml.xml
but can not access the Internet,  pinging my host system appears to be no
problem though..

my host system has a ADSL connection to the Internet, and "eth0" has been
assigned with IP 192.168.0.1.
here is my command line that brings up the user mode linux:

UML> linux ubd0=root_fs ubd1=swap_fs eth0=tuntap,,,192.168.0.1

I assigned 192.168.0.2 to my UML, added default route entry; copyed
over my resolv.conf.
but still can't contact with my name servers nor other Internet hosts.

did I miss something? or the guide is just incomplete?

thanks.
daniel




<http://www.gentoo.org/doc/en/uml.xml>

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Re: [gentoo-user] the user mode linux can't access network..

[Etaoin Shrdlu]

On Monday 21 August 2006 08:38, fei huang wrote:

> did I miss something? or the guide is just incomplete?

I see you are directly connecting the real host to the virtual host using 
tuntap (eg, you don't use uml_switch).

You probably need to enable forwarding (and possibly masquerading) on the 
real box:

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
echo 1 > /proc/sys/net/ipv4/ip_forward

The guide DOES mention this, in the section "using an existing network".

HTH
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] the user mode linux can't access network..

[fei huang]

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On 8/21/06, Etaoin Shrdlu <shrdlu@unlimitedmail.org> wrote:
>
> On Monday 21 August 2006 08:38, fei huang wrote:
>
> > did I miss something? or the guide is just incomplete?
>
> I see you are directly connecting the real host to the virtual host using
> tuntap (eg, you don't use uml_switch).


I would like the most direct and easy way to access the network, seems the
uml_switch needs just a lot more steps to set up the network... not sure
though.

You probably need to enable forwarding (and possibly masquerading) on the
> real box:
>
> iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
> echo 1 > /proc/sys/net/ipv4/ip_forward
>
> The guide DOES mention this, in the section "using an existing network".


yep, that's why I get so frustrated, I did exactly the same as what the
guide instructs..
any other posibilities that may cause the problem?

HTH
> --
> gentoo-user@gentoo.org mailing list
>
> thank you so much..
daniel

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Re: [gentoo-user] the user mode linux can't access network..

[Etaoin Shrdlu]

On Monday 21 August 2006 11:24, fei huang wrote:

> yep, that's why I get so frustrated, I did exactly the same as what
> the guide instructs..
> any other posibilities that may cause the problem?

Ok, let's see: you say that your eth0 (which I guess is the interface 
connected to the ADSL and thus to the Internet) has ip address 
192.168.0.1. Then, you use this command to start uml:

UML> linux ubd0=root_fs ubd1=swap_fs eth0=tuntap,,,192.168.0.1

this means that the *host's* tun/tap interface gets ip address 
192.168.0.1 as well. So, the host ends up with its two interfaces having 
the same ip address (do "ip addr" or "ifconfig" when uml is running to 
confirm this) . 
If the above is true, try using different addresses for the tun/tap<->uml 
network, for example from the 10.0.0.0 pool.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] the user mode linux can't access network..

[fei huang]

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On 8/21/06, Etaoin Shrdlu <shrdlu@unlimitedmail.org> wrote:
>
> On Monday 21 August 2006 11:24, fei huang wrote:
>
> > yep, that's why I get so frustrated, I did exactly the same as what
> > the guide instructs..
> > any other posibilities that may cause the problem?
>
> Ok, let's see: you say that your eth0 (which I guess is the interface
> connected to the ADSL and thus to the Internet) has ip address
> 192.168.0.1. Then, you use this command to start uml:
>
> UML> linux ubd0=root_fs ubd1=swap_fs eth0=tuntap,,,192.168.0.1
>
> this means that the *host's* tun/tap interface gets ip address
> 192.168.0.1 as well. So, the host ends up with its two interfaces having
> the same ip address (do "ip addr" or "ifconfig" when uml is running to
> confirm this) .


yep, I did notice this problem, and tried to change the tun/tap  interface
to 192.168.0.3,
I guess this must be the same network with eth0 of my host system,, but no
luck...

If the above is true, try using different addresses for the tun/tap<->uml
> network, for example from the 10.0.0.0 pool.
> --


I'll try it out... hope this works.  thanks.

gentoo-user@gentoo.org mailing list


regards.

daniel.

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Re: [gentoo-user] the user mode linux can't access network..

[fei huang]

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still no luck... I tried to build everything in kernel, and later build
additional iptable_filter as module, add iptable to my default run level,,
neither of them works..

I found there is a warning message after emerge iptables says: ip forwarding
is not included in iptables any more. what does it mean? is that related
with the issue?

any hints ?...

thanks

daniel

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Re: [gentoo-user] the user mode linux can't access network..

[Etaoin Shrdlu]

On Monday 21 August 2006 16:22, fei huang wrote:

> still no luck... I tried to build everything in kernel, and later
> build additional iptable_filter as module, add iptable to my default
> run level,, neither of them works..

I'd try first with iptables filters *disabled*, to make sure it's not a 
firewall issue. Once it works, enable packet filtering (if you need it). 
But until you are sure it works, make sure nothing prevents traffic 
flow, so disable iptables filters.

> I found there is a warning message after emerge iptables says: ip
> forwarding is not included in iptables any more. what does it mean? is
> that related with the issue?

It means that, if you want ip forwarding, you have to enable it manually 
using the command

echo 1 > /proc/sys/net/ipv4/ip_forward

To verify that forwarding is working, simply do

cat /proc/sys/net/ipv4/ip_forward

and it should print "1".
Keep in mind that if you reboot, you have to re-enable forwarding if you 
want it again.

Finally, run a network analyzer like wireshark and see for yourself 
what's happening. I'd look at ARP packets first: make sure ARP is 
working correctly.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] the user mode linux can't access network..

[fei huang]

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On 8/21/06, Etaoin Shrdlu <shrdlu@unlimitedmail.org> wrote:
>
> On Monday 21 August 2006 16:22, fei huang wrote:
>
> > still no luck... I tried to build everything in kernel, and later
> > build additional iptable_filter as module, add iptable to my default
> > run level,, neither of them works..
>
> I'd try first with iptables filters *disabled*, to make sure it's not a
> firewall issue. Once it works, enable packet filtering (if you need it).
> But until you are sure it works, make sure nothing prevents traffic
> flow, so disable iptables filters.


mm, I  disabled it from  auto  loading.

> I found there is a warning message after emerge iptables says: ip
> > forwarding is not included in iptables any more. what does it mean? is
> > that related with the issue?
>
> It means that, if you want ip forwarding, you have to enable it manually
> using the command
>
> echo 1 > /proc/sys/net/ipv4/ip_forward
>
> To verify that forwarding is working, simply do
>
> cat /proc/sys/net/ipv4/ip_forward
>
> and it should print "1".
> Keep in mind that if you reboot, you have to re-enable forwarding if you
> want it again.


gentoo might do that trick for me, everytime I  check  that value, it shows
1.

Finally, run a network analyzer like wireshark and see for yourself
> what's happening. I'd look at ARP packets first: make sure ARP is
> working correctly.
> --
> gentoo-user@gentoo.org mailing list


uh, that's a good idea, I'll emege wireshark and see what's happening, the
most annoying thing is that there's no log for troubleshooting, I wonder why
iptable never write anything to syslog?  that's wierd.


regards

daniel

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Re: [gentoo-user] the user mode linux can't access network..

[Etaoin Shrdlu]

On Monday 21 August 2006 17:11, fei huang wrote:

> uh, that's a good idea, I'll emege wireshark and see what's happening,
> the most annoying thing is that there's no log for troubleshooting, I
> wonder why iptable never write anything to syslog?  that's wierd.

It will, if you tell it. Look at the LOG/ULOG targets.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] the user mode linux can't access network..

[fei huang]

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thanks for helping...
the problem has been solved by applying iptable rules on my ppp0 instead of
eth0. since ppp0 is the real device that conncts to the Internet.


tks again.

daniel

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