[Engine-devel] network features review

[Dan Kenigsberg]

On Tue, May 22, 2012 at 03:53:56PM +0300, avi tal wrote:
> On 05/22/2012 03:06 PM, Livnat Peer wrote:
> >On 22/05/12 14:35, avi tal wrote:
> >>On 05/22/2012 11:45 AM, Livnat Peer wrote:
> >>>Hi All,
> >>>
> >>>This is a summary of comments we(*) gathered while reviewing the current
> >>>network related functionality in oVirt, we'll open the relevant RFE/Bugs
> >>>but wanted to share first to get comments:
> >>>
> >>>
> >>>Default Gateway:
> >>>----------------
> >>>current status -
> >>>    In the UI/API we expose to the user the possibility to configure the
> >>>    default gateway for the host. We expose this option only when editing
> >>>    the management network.
> >>>
> >>>comments -
> >>>Apparently we do not configure the host default gateway but the
> >>>network gateway.
> >>>
> >>>1. We need to fix the phrasing to gateway (not default gateway)
> >>not true. especially in linux we configure "default gateway". unlike
> >>windows which holds gateway for each interface, linux holds only one
> >>default gateway.
> >I'll leave this one to Danken.
> 
> Running POC in my machine:
> # cat ifcfg-eth1
> DEVICE=eth1
> ONBOOT=yes
> BOOTPROTO=static
> IPADDR=X.Y.129.10
> NETMASK=255.255.255.0
> GATEWAY=X.Y.129.254
> 
> # cat ifcfg-eth2
> DEVICE=eth2
> ONBOOT=yes
> BOOTPROTO=static
> IPADDR=X.Y.127.10
> NETMASK=255.255.255.0
> GATEWAY=X.Y.127.254
> 
> # cat /etc/sysconfig/network
> NETWORKING=yes
> HOSTNAME=...
> GATEWAY=X.Y.128.254
> 
> # service network restart
> # route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref
> Use Iface
> X.Y.129.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
> X.Y.127.0     0.0.0.0         255.255.255.0   U     0      0        0 eth2
> 169.254.0.0     0.0.0.0         255.255.0.0     U     1003   0        0 eth1
> 169.254.0.0     0.0.0.0         255.255.0.0     U     1004   0        0 eth2
> 169.254.0.0     0.0.0.0         255.255.0.0     U     1005   0        0 eth3
> 0.0.0.0         X.Y.127.254   0.0.0.0         UG    0      0        0 eth2
> 
> 
> NOTE: we can add static routing to each interface using route-<interface>

I am afraid that I've been misleading Livnat and Simon in private
communications. I've repressed this fact for a long while, but apparently
initscripts's usage of GATEWAY, be it in interface or hostwide config, is to
set the host's default gateway. /etc/sysconfig/network-scripts/ifup-eth :

       if [ -n "${GATEWAY}" ] ...; then
            ip route replace default ${METRIC:+metric $METRIC} \
                via ${GATEWAY} ${WINDOW:+window $WINDOW} ${SRC} \
                ${GATEWAYDEV:+dev $GATEWAYDEV} ...


This means that oVirt's current behavior is ok as it is - we set GATEWAY
for a single network that is always on, and thus control the host's
default gateway.