[ovirt-users] R: R: PXE boot of a VM on vdsm don't read DHCP offer

[Dan Kenigsberg]

On Fri, May 08, 2015 at 03:11:25PM +0200, NUNIN Roberto wrote:
> Hi Dan
> Thanks for answering
> 
> 
> 
> > Which kernel does the el7 host run? I think that Ido has seen a case
> > where `brctl showmacs` was not populated with the VM mac, despite a
> > packet coming out of it.
> 
> Kernel is: 3.10.0-123.20.1.el7.x86_64, package is vdsm only. Brctl isn't available within vdsm only package.

Could you try upgrading to a more up-to-date
http://mirror.centos.org/centos-7/7.1.1503/updates/x86_64/Packages/kernel-3.10.0-229.4.2.el7.x86_64.rpm
?

bridge-utils is a vdsm dependency. It must exist on your host. Please
see if the mac of the vNIC shows up on `brctl showmacs` as it should.

> >
> > Can you tcpdump and check whether the bridge propogated the DHCP offer
> > to the tap device of the said VM? Does the packet generated by
> > `ether-wake MAC-of-VM` reach the tap device?
> 
> Yes: host "see" the broadcast :
>         0.000000    0.0.0.0               255.255.255.255       DHCP     346    DHCP Discover - Transaction ID 0x69267b67
> It came from the right MAC:
>         Source: Qumranet_15:81:03 (00:1a:4a:15:81:03)
> And it is tagged correctly:
>         802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 3500
> 
> This is the offer, on the bond interface:
>         1.012355    10.155.124.2          10.155.124.246        DHCP     346    DHCP Offer    - Transaction ID 0x69267b67
> Layer 2 info:
>         Ethernet II, Src: Cisco_56:83:c3 (84:78:ac:56:83:c3), Dst: Qumranet_15:81:03 (00:1a:4a:15:81:03)
> Tagging on the bond:
>         802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 3500
> 
> The tag is correctly removed when DHCP offer is forwarded over the bond.3500.
> Here's the offer content, seems everything right:
> 
>     Client IP address: 0.0.0.0 (0.0.0.0)
>     Your (client) IP address: 10.155.124.246 (10.155.124.246)
>     Next server IP address: 10.155.124.223 (10.155.124.223)
>     Relay agent IP address: 10.155.124.2 (10.155.124.2)
>     Client MAC address: Qumranet_15:81:03 (00:1a:4a:15:81:03)
>     Client hardware address padding: 00000000000000000000
>     Server host name: 10.155.124.223
>     Boot file name: pxelinux.0
>     Magic cookie: DHCP
> 
> Nothing of this offer appear on the VM side.

But does it show on the host's bridge? on the tap device?

> 
> ether-wake -i bond0.3500 00:1a:4a:15:81:03 (started from the host)
> reach the VM eth0 interface:
>         2.002028   HewlettP_4a:47:b0     Qumranet_15:81:03     WOL      116    MagicPacket for Qumranet_15:81:03 (00:1a:4a:15:81:03)
> 
> Really strange behavior.
> 
> Roberto