Re: [libvirt] [PATCH-v4 2/2] Support for static routes on a virtual bridge
On 04/25/2013 04:13 PM, Gene Czarcinski wrote:
On 04/25/2013 03:13 PM, Gene Czarcinski wrote:
> On 04/22/2013 11:59 AM, Laine Stump wrote:
>> address should be optional unless prefix or netmask is non-0, although
>> I've now noticed that won't be handled properly due to
>> virSocketAddrGetIpPrefix returning -1 when there is no address or
>> prefix
>> or netmask (I'm fixing that before I push that patch, so you can just
>> toss your 1/2 patch, rebase, and assume it's fixed).
> I have most of the stuff reworked except for the address, gateway,
> netmask, and prefix code. Getting all of those balanced so they work
> correctly is a bit tricky..
>
> 1. For <route>, I am requiring that both address= and gateway= be
> specified with address='0.0.0.0' and address='::' being valid
> addresses. For IPv4, netmask='0.0.0.0' works correctly but prefix=0
> does not.
>
> For IPv4, address='0.0.0.0' results in a default route. I am not
> sure what all these extra default routes are going to do to things
> but lets not get in the way of the experimenter.
>
> For IPv6, this address='::', prefix='0' is a slightly different
> matter as default routes are usually handled differently. I am going
> to go ahead and implement it but I am not sure it is a good idea.
> "Normally," if you do not specify a prefix for IPv6, the default is
> 64. But if you do specify one, then it will be used.
>
> It is getting real close and it should be ready "real soon now" ;))
>
AARRRRGH!!!!
With IPv4 using address='0.0.0.0' and netmask='0.0.0.0' things work
just fine but with prefix not so much. The problem is that with
prefix=0, it is not in the xml which then results it it defaulting at
a later time. This is an extreme corner case. Usually a zero prefix
is just ignored.
Defaulting to what? I thought that when I pushed the utility function
for that, I modified it to return a prefix of 0 if the address was
0.0.0.0 and neither netmask nor prefix was set.
I guess it might be problematic if address was *not* 0 and you wanted an
explicit 0 prefix, but I don't think that would ever be useful.
If you really want prefix to show up in the xml if someone explicitly
puts "prefix='0'" in there, you can add a "bool
prefix_specified;" to
the object, and set that when you see a prefix, even if it's 0. Then in
the formatter you'll know that you should write out the value of prefix,
even if it's 0.
There are a few examples of doing this in either the network or domain
xml parser/formatter - just search for occurrences of the word
"_specified" in src/conf/*.[ch] and you'll find them.