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From: Laszlo Ersek <lersek@redhat.com>
Message-ID: <57209BFD.7010601@redhat.com>
Date: Wed, 27 Apr 2016 13:01:17 +0200
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Subject: Re: [Qemu-devel] Is anyone able to load a web page from a guest
 operating system?
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To: Thomas Huth <thuth@redhat.com>, Programmingkid <programmingkidx@gmail.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>, qemu-devel qemu-devel <qemu-devel@nongnu.org>

On 04/27/16 12:26, Thomas Huth wrote:
> On 27.04.2016 12:05, Laszlo Ersek wrote:
>> On 04/26/16 22:12, Thomas Huth wrote:
>>> On 26.04.2016 21:25, Programmingkid wrote:
>>>> On Apr 26, 2016, at 3:00 PM, Dr. David Alan Gilbert wrote:
>>
>>>>> Does ping work?
>>>> I can ping the virtual router at 10.0.2.2. Any other ip address fails. 
>>>
>>> That's normal for user-mode / slirp networking. You can't ping external
>>> hosts with this mode.
>>
>> Side note: yes, you can.
>>
>> I do it whenever I want to check network connectivity from within ad-hoc
>> OVMF guests, using the PING command of the UEFI shell. ("Ad-hoc guest"
>> implies user-mode / slirp.)
>>
>> It can be enabled with the following steps:
>>
>> (1) Determine the main group ID (or one supplementary group ID) of the
>> user that will run QEMU with slirp.
>>
>> (2) In /etc/sysctl.conf (or whatever is appropriate for your host
>> distro), make sure that the whitespace separated inclusive group ID
>> range in the "net.ipv4.ping_group_range" sysctl includes the above group ID.
> 
> Wow, thanks for that hint, I just tried by temporarily enabling it with
> 
>  sudo sysctl net.ipv4.ping_group_range=...
> 
> and indeed it works!
> 
> Maybe we should document that somewhere?
> For example  http://qemu-project.org/Documentation/Networking currently
> only says: "ICMP traffic does not work (so you cannot use ping within a
> guest)" ...

Done.

Laszlo