Re: [libvirt] [PATCH] lxc: support <interface type='ethernet'>

2016-05-25 18:00 GMT+03:00 Laine Stump <laine(a)laine.org&gt;: > So $VM_GW is on the same subnet as $VM_IP/24 ? Is that also the same subnet > as $HOST_IP? Or is that on a completely different network? > > (This is all very useful, because it's pointing out that the config of the > two ends definitely aren't mirror images, so we really do need independent > settings for both). > VM_GW on the same subnet as PEER , but on host side i apply /32 address, but inside vm /24. >> peer only used on host machine to determine on which interface kernel >> needs to send traffic > > Well, you *could* do the same thing with a /30 subnet for each tap (so that > your routing daemon would get a bunch of /30 routes pointing to your host > for all of them), but that would use up a lot more address space. > >>> (I'm not sure what the guest does with 169.254.169.254) >>> >>> What if you instead set the host to: >>> >>> $HOST_IP peer $VM_IP/32 >>> >>> and set the guest to: >>> >>> $VM_IP peer $HOST_IP/32 >>> route add default $HOST_IP >>> >>> ?? >>> >> I don't use this scheme... If i set $VM_IP peer $HOST_IP/32 on host >> machine i think kernel recieves packet and drop it =) > > No - you would set that on the *guest*, not the host. I setup an LXC > container in this manner and everything seemed to work properly. > May be, but in case of qemu i use simple dhcp server and on vm simple dhcp client. It can't assign peer addresses

may be this is works. I don't try. In my setup guest vm does not know host side of network, so it does not need know about peer... Also i can live migrate guest without changing.... (Changes only host side of network) >>> Anyway, it's important to know if you set the IP config on host and guest >>> to >>> exact mirrors of each other. It seems like the answer is "no", though, so >>> i'm going to make a patch that allows what I was talking about last week: >>> >>> >>> <interface type='ethernet'> >>> <source> >>> <ip address='HOST_IP' family='ipv4' peer='VM_IP' >>> prefix='32'/> >>> <ip address='VM_GW' family='ipv4' prefix='32'/> >>> </source> >>> <ip address='VM_IP' family='ipv4' peer='HOST_IP' prefix='24'/> >>> <route family='ipv4' address='0.0.0.0' gateway='HOST_IP'/> >>> ... >>> </interface> >>> >>> On qemu only the address info inside <source> would be used, since we >>> don't >>> have control over the guest's network config. On LXC, we can set both. >>> >>> Does that sound usable? >> Yes, but don't cleanup please <ip address='VM_IP' family='ipv4' >> peer='HOST_IP' prefix='24'/> in qemu case, because on somedays we can >> launch dnsmasq or orhet software that can provide dhcp and use this >> element.. > > An interesting point - even if libvirt itself doesn't launch the dnsmasq, it > could be done by a more intelligent script (one that received the full > interface XML on stdin, as I discussed in my last mail), so we should > probably just ignore it rather than complaining that it's unsupported... > > Thanks for the info! Yes, i handmade my own dhcp server on golang what listens libvirt hooks and serves needed addresses for needed tap devices.

So i have only one daemon that have stateless config (it get it via libvirt xml). So i don't need database or something else.