[libvirt] [PATCH 1/2] qemu: Remove network type limitation for qemuARPGetInterfaces

[Chen Hanxiao]

At 2018-09-11 13:51:43, "Lin Ma" <lma at suse.com> wrote:   
>On 09/10/2018 02:55 PM, Chen Hanxiao   wrote:  
>        
>At 2018-09-07 18:44:53, "Lin Ma" <lma at suse.com> wrote:
>>When we call qemuARPGetInterfaces to get IP from host's arp table, The
>>iface's type has nothing to do with it, We should allow all of type.
>>
>>Signed-off-by: Lin Ma <lma at suse.com>
>
>Hi,
>   with my limited tests, 
>   we can't get useful info by arp query from other kind of interface types.
>      
>    
>    
>
>    IMO, As long as the host interface and the guest interface
>      communicated
>
>    through osi layer3 or above, Host kernel will maintaince
>      the corresponding
>
>      ip <-> mac entry in arp able.
>
>    

A lot of network backend, such as vrouter, dpdk, the package from guest os
did not come back to the host's protocol stack.
We can't see them in host's arp table.

>
>    What you mentioned above remind me one thing: I forgot to
>      mention that
>
>    if the switch doesn't support hairpin mode, then the
>      virtual interfaces
>
>    which backend is mactap can't communicate with host,
>      that means the host
>
>    arp table won't include the ip <-> mac information
>      of such virtual interfaces.
>
>    In this case, the qemuARPGetInterfaces
>      can't get IP.
>
>    
>
>    So I'd like to change the code to only ignore
>      VIR_DOMAIN_NET_TYPE_DIRECT

Maybe adding VIR_DOMAIN_NET_TYPE_ETHERNET and VIR_DOMAIN_NET_TYPE_VHOSTUSER?

Regards,
- Chen

>
>    in patch V2, For anyelse net types, the
>      code will iterate the arp table for
>
>    loop to try to search if there is a
>      matched entry.
>
>    
>
>    what do you think?
>
>    
>
>    Thanks,
>
>    Lin