[libvirt] Re: [netcf-devel] [RFC] Reporting host interface status/statistics via netcf/libvirt, and listing active vs. inactive interfaces
On Tue, 2009-06-16 at 15:12 -0400, Laine Stump wrote:
I've already been working on incorporating physical host
interface
configuration into libvirt by way of using libnetcf on the backend. It's
becoming apparent that, in addition to modifying and reporting the
current configuration of interfaces, libvirt users also want to query
current status of each interface (up/down, possibly other flags,
packet/byte/error counts, current IP address, etc).
There are two possible ways of doing this:
1) maintain libnetcf's focus on just interface configuration, and
add code directly into libvirt to grab this information via
appropriate ioctls
or
2) add the functionality to libnetcf, and have libvirt call the
new libnetcf API.
(2) seems to make the most sense, because likely other libnetcf
consumers will want this capability too.
I agree that netcf is the right place for this functionality; the
downside either way is that we'll wind up reimplementing a good bit of
ifconfig's functionality. But seeing how net-tools does not expose a
library that's inevitable (and it's mostly an exercise in calling ioctl
anyway).
I'm thinking of a single API, something like:
int netcf_if_status(netcf_if *, netcf_if_stats *);
(or maybe int netcf_if_info(netcf_if *, netcf_if_info *))
I haven't really put much thought into the details of what should be in
netcf_if_stats yet (beyond what I listed above), but wanted to get this
idea out there so people can start sounding off (if I'm going down the
wrong road, I'd rather be put on the right path before I get too far along!)
There should really be multiple API's to cover the functionality;
rolling it all into one giant struct seems too inflexible. I am thinking
there should be at least 3 calls
* int netcf_if_operstate(netcf_if *) - return 1 if interface is
up, 0 if not
* int netcf_if_stats(netcf_if *, netcf_if_stats *) - get rx/tx
statistics; which ones needs to be figured out in detail
* int netcf_if_addrinfo(netcf_if *, netcf_if_addrinfo *) - get
address info, i.e. IPv4 and/or IPv6 addresses assigned to the
interface
One wrinkle is that netcf operates at the level of 'connections', not
with individual interfaces, e.g. when a physical NIC eth0 is enslaved to
a bridge br0, only the bridge is currently visible through the netcf
API. So for statistics gathering, you'd only see the statistics for br0
- if statistics for individual devices on the bridge are needed, we can
either report all of them in netcf_if_stats, or provide a mechanism to
get at the subinterfaces so that netcf_if_stats etc. can be called
separately for br0 and eth0.
But netcf could do it with an extra argument to
ncf_list_interfaces().
If the latter, should the default behavior be to list all interfaces,
with flags set to eliminate up or down interfaces?
0 (list all)
NETCF_NOLIST_UP
NETCF_NOLIST_DOWN
Or should the values be something like this:
0 (list all)
NETCF_LIST_UP_ONLY
NETCF_LIST_DOWN_ONLY
(UP_ONLY + DOWN_ONLY would be equivalent to 0. As long as nobody came up
with a good reason for "0".
So should we do one of those, or should we mimic libirt's virNetwork API
in libnetcf too?
I'd lean towards the flag approach, but without the special meaning for
0 - if you specify any flags, you won't get any interfaces ;)
Since we're dealing with compound interfaces, we also need to define
what it means for a bridge to be up - e.g., the bridge device and all
enslaved physical NICs need to be up.
David