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Jean-Pierre Ribeauville

2015-Aug-27 13:48 UTC

[libvirt-users] Using unix-type channel ....

Hi,

I'm trying to use unix-type channel to send/receive datas between host and
guest .

Here are the steps I follow :

1) Adding these lines to expose a channel unix type to my guest
 <channel type='unix'>
      <source mode='bind'
path='/var/lib/libvirt/qemu/omnivision_1.agent'/>
      <target type='virtio'
name='org.qemu.guest_agent.0'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0'
bus='0' port='2'/>
    </channel>


2) the VM_Orion-1 Guest, exposing a channel "unix" omnivision_1.agent 
is started, then netstat shows these new things :

netstat -apn | grep qemu
unix  2      [ ACC ]     STREAM     LISTENING     37214  19124/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor
unix  2      [ ACC ]     STREAM     LISTENING     37219  19124/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     37242  19124/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     37240  19124/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor

3) I start  , on the host , a simple test in order to send datas to the guest:

.....
     sock = socket(AF_UNIX, SOCK_STREAM, 0);
     if (sock < 0) {
         perror("opening stream socket");
         return(1);
     }
     server.sun_family = AF_UNIX;
     strcpy(server.sun_path, argv[1]);

     printf("connecting to socket number : %d \n",sock);
     fflush(stdout);

     if (connect(sock, (struct sockaddr *) &server, sizeof(struct
sockaddr_un)) < 0) {
         close(sock);
         perror("connecting stream socket");
         return(1);
     }
     printf("writing data on stream socket");
     if (write(sock, DATA, sizeof(DATA)) < 0)
         perror("writing on stream socket");
     close(sock);
.....

4) invoking  > test "/var/lib/libvirt/qemu/omnivision_1.agent"

then I got  :

connecting to socket number : 3
writing data on stream socket

and following netstat result :

netstat -apn | grep qemu
unix  2      [ ACC ]     STREAM     LISTENING     39348  20587/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor
unix  2      [ ACC ]     STREAM     LISTENING     39353  20587/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  2      [ ]         STREAM     CONNECTING    0      -                  
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     39375  20587/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     39373  20587/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor



5) if I try to re-invoke test
"/var/lib/libvirt/qemu/omnivision_1.agent"  then :

netstat -apn | grep qemu
tcp        0      0 127.0.0.1:5902              0.0.0.0:*                  
LISTEN      20587/qemu-kvm
tcp        0      0 127.0.0.1:5902              127.0.0.1:57772            
ESTABLISHED 20587/qemu-kvm
unix  2      [ ACC ]     STREAM     LISTENING     39348  20587/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor
unix  2      [ ACC ]     STREAM     LISTENING     39353  20587/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  2      [ ]         STREAM     CONNECTING    0      -                  
/var/lib/libvirt/qemu/omnivision_1.agent
unix  2      [ ]         STREAM     CONNECTING    0      -                  
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     39375  20587/qemu-kvm     
/var/lib/libvirt/qemu/omnivision_1.agent
unix  3      [ ]         STREAM     CONNECTED     39373  20587/qemu-kvm     
/var/lib/libvirt/qemu/VM_Orion-1.monitor


on the guest side , I try to retrieve datas sent by host , by using this kind of
thing  :

...
int fd = open("/dev/virtio-ports/org.qemu.guest_agent.0", O_RDWR |
O_NONBLOCK);
    ssize_t size = read(fd, &buffer, 100);
...


As you can imagine , I never receive any data from the host .


Is it the right way to use this "unix-type"  channel ?

Thx for your patience.

Regards,

J.P. Ribeauville


P: +33.(0).1.47.17.27.87


Puteaux 3 Etage 5  Bureau 4

jpribeauville@axway.com<mailto:jpribeauville@axway.com>
http://www.axway.com<http://www.axway.com/>



P Pensez à l'environnement avant d'imprimer.

Michal Privoznik

2015-Aug-28 04:28 UTC

head link

Re: [libvirt-users] Using unix-type channel ....

On 27.08.2015 15:48, Jean-Pierre Ribeauville wrote:> Hi,
> 
> I'm trying to use unix-type channel to send/receive datas between host
and guest .
> 
> Here are the steps I follow :
> 
> 1) Adding these lines to expose a channel unix type to my guest
>  <channel type='unix'>
>       <source mode='bind'
path='/var/lib/libvirt/qemu/omnivision_1.agent'/>
>       <target type='virtio'
name='org.qemu.guest_agent.0'/>
>       <alias name='channel0'/>
>       <address type='virtio-serial' controller='0'
bus='0' port='2'/>
>     </channel>
> 
This won't fly. A channel with that name is special. It's guest agent
socket that libvirt automatically connects to once domain is starting
up. You need to provide a different name and everything should just work.

Michal

Michal Privoznik

2015-Aug-28 06:41 UTC

head link

Re: [libvirt-users] Using unix-type channel ....

On 28.08.2015 08:34, Jean-Pierre Ribeauville wrote:> HI,
> 
> 
> 
> Thx for your hint.
> 
> 
> 
> I've tried this instead :
> 
> 
> 
> <channel type='unix'>
> 
>       <source mode='bind'
path='/opt/omnivision_1.agent'/>
> 
>       <target type='virtio'
name='omnivision_1.agent'/>
> 
>       <address type='virtio-serial' controller='0'
bus='0' port='2'/>
> 
>     </channel>
> 
> 
> 
> Then,  when starting the Guest I get this error message :
[It's better to send just text via e-mail]

So, the error message is telling you, that qemu process does not have
enough permissions to bind to the unix socket under the given path.
Either you should level up qemu permissions (e.g. run it as root), or
use path that qemu will have access to. Or set correct permissions on
the socket target.

Michal

Jean-Pierre Ribeauville

2015-Aug-28 06:45 UTC

head link

Re: [libvirt-users] Using unix-type channel ....

Hi,


Thx for your hint.



I've tried this instead :



<channel type='unix'>

      <source mode='bind' path='/opt/omnivision_1.agent'/>

      <target type='virtio' name='omnivision_1.agent'/>

      <address type='virtio-serial' controller='0'
bus='0' port='2'/>

    </channel>



Then,  when starting the Guest I get  a pop up window showing this error message
:

Error starting domain : internal error : process exited while connecting to
monitor
Quemu-kvm -chardev socket id=channel1,path=/opt/omnivision_1_agent,server,nowait
Failed to bind socket : Permission denied


Did I miss something ?

Regards,

J.P.




-----Message d'origine-----
De : Michal Privoznik [mailto:mprivozn@redhat.com]
Envoyé : vendredi 28 août 2015 06:28
À : Jean-Pierre Ribeauville;
libvirt-users@redhat.com<mailto:libvirt-users@redhat.com>
Objet : Re: [libvirt-users] Using unix-type channel ....



On 27.08.2015 15:48, Jean-Pierre Ribeauville wrote:
> Hi,
>
> I'm trying to use unix-type channel to send/receive datas between host
and guest .
>
> Here are the steps I follow :
>
> 1) Adding these lines to expose a channel unix type to my guest
> <channel type='unix'>
>       <source mode='bind'
path='/var/lib/libvirt/qemu/omnivision_1.agent'/>
>       <target type='virtio'
name='org.qemu.guest_agent.0'/>
>       <alias name='channel0'/>
>       <address type='virtio-serial' controller='0'
bus='0' port='2'/>
>     </channel>
>


This won't fly. A channel with that name is special. It's guest agent
socket that libvirt automatically connects to once domain is starting up. You
need to provide a different name and everything should just work.



Michal

Jean-Pierre Ribeauville

2015-Aug-28 07:57 UTC

head link

Re: [libvirt-users] Using unix-type channel ....

Hi,

By using an "qemu"  accessible path , bi -directional  exchanges are
working fine.

Thx for help.

J.P.

-----Message d'origine-----
De : Michal Privoznik [mailto:mprivozn@redhat.com] 
Envoyé : vendredi 28 août 2015 08:41
À : Jean-Pierre Ribeauville; libvirt-users@redhat.com
Objet : Re: [libvirt-users] Using unix-type channel ....

On 28.08.2015 08:34, Jean-Pierre Ribeauville wrote:> HI,
> 
> 
> 
> Thx for your hint.
> 
> 
> 
> I've tried this instead :
> 
> 
> 
> <channel type='unix'>
> 
>       <source mode='bind'
path='/opt/omnivision_1.agent'/>
> 
>       <target type='virtio'
name='omnivision_1.agent'/>
> 
>       <address type='virtio-serial' controller='0'
bus='0' port='2'/>
> 
>     </channel>
> 
> 
> 
> Then,  when starting the Guest I get this error message :
[It's better to send just text via e-mail]

So, the error message is telling you, that qemu process does not have enough
permissions to bind to the unix socket under the given path.
Either you should level up qemu permissions (e.g. run it as root), or use path
that qemu will have access to. Or set correct permissions on the socket target.

Michal

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