[libvirt] [PATCH-v4.2] Support for static routes on a virtual bridge

[Gene Czarcinski]

On 04/29/2013 11:55 AM, Laine Stump wrote:
> (I wanted a separate message to comment on this part...)
>
> On 04/26/2013 07:22 PM, Gene Czarcinski wrote:
>> +/* add an IP (static) route to a bridge */
>> +static int
>> +networkAddRouteToBridge(virNetworkObjPtr network,
>> +                        virNetworkRouteDefPtr routedef)
>> +{
>> +    bool done = false;
>> +    int prefix = 0;
>> +    virSocketAddrPtr addr = &routedef->address;
>> +    virSocketAddrPtr mask = &routedef->netmask;
>> +
>> +    if (VIR_SOCKET_ADDR_IS_FAMILY(addr, AF_INET)) {
>> +        long val4 = ntohl(addr->data.inet4.sin_addr.s_addr);
>> +        long msk4 = -1;
>> +        if  (VIR_SOCKET_ADDR_IS_FAMILY(mask, AF_INET)) {
>> +            msk4 = ntohl(mask->data.inet4.sin_addr.s_addr);
>> +        }
>> +        if (msk4 == -1) {
>> +            if (val4 == 0 && routedef->prefix == 0)
>> +                done = true;
>> +        } else {
>> +            if (val4 == 0 && msk4 == 0)
>> +                done = true;
>> +        }
>> +    }
> I'll try and decode this...
>
>    if ((address == 0.0.0.0)
>        and ((((netmask is unspecified) and (prefix is (0 or unspecified)))
>             or (netmask is 0.0.0.0)))
>
>       then use 0 for prefix when adding the route
>
> Is that correct?
>
> First - I would like to avoid references to the internal data structures
> of a virSocketAddr, and calling ntohnl at this level. virSocketAddr
> should be able to handle any bit twiddling we need.
>
> Now, let's see how much of that we can get rid of:
>
> 1) If netmask is 0.0.0.0, virSocketAddrGetIpPrefix will anyway return
> virSocketAddrGetNumNetmaskBits(0.0.0.0), which is conveniently 0.
>
>
> 2) if neither netmask nor prefix is specified, virSocketAddrGetIpPrefix
> will return 0 anyway (regardless of address), *but only if address
> wasn't specified*. If an address *was* specified and it was 0.0.0.0, it
> returns 8 (treating it as a Class A network)
>
> I had actually intended that my modification to
> virSocketAddrGetIpPrefix() to return
> 0 would eliminate the need for such code in bridge_driver.c, but didn't
> do it quite right, and it's just as well, because I just checked and
> RFCs say that there *is* some valid use for 0.0.0.0/8.
>
>
>
>> +    else if (VIR_SOCKET_ADDR_IS_FAMILY(addr, AF_INET6)) {
>> +        int i, val6 = 0;
>> +        for (i = 0;i < 4;i++) {
>> +            val6 += ((addr->data.inet6.sin6_addr.s6_addr[2 * i] << 8) |
>> +                     addr->data.inet6.sin6_addr.s6_addr[2 * i + 1]);
>> +        }
>> +        if (val6 == 0 && routedef->prefix == 0) {
>> +            char *addr = virSocketAddrFormat(&routedef->address);
>> +            virReportError(VIR_ERR_INTERNAL_ERROR,
>> +                           _("bridge '%s' has prefix=0 for address='%s' which is not supported"),
>> +                           network->def->bridge, addr);
>> +            VIR_FREE(addr);
>> +            return -1;
>> +        }
>> +    }
>
> and here - if the address is 0 and the prefix is 0/unspecified, then log
> an error. But if this is really something that's always illegal
> according to the IPv6 RFCs, then we can/should do that validation in the
> parser, not here.
>
>
>> +
>> +    if (done) {
>> +        prefix = 0;
>> +    } else {
>> +        prefix = virSocketAddrGetIpPrefix(&routedef->address,
>> +                                          &routedef->netmask,
>> +                                          routedef->prefix);
>> +
>> +        if (prefix < 0) {
>> +            virReportError(VIR_ERR_INTERNAL_ERROR,
>> +                           _("bridge '%s' has an invalid netmask or IP address for route definition"),
>> +                           network->def->bridge);
>> +            return -1;
>> +        }
>> +    }
>> +
>> +    if (virNetDevSetGateway(network->def->bridge,
>> +                            &routedef->address,
>> +                            prefix,
>> +                            &routedef->gateway) < 0)
>> +        return -1;
>> +    return 0;
>> +}
>>
>
> So here's my opinion:
>
> 1) remove all that code above (I did that in my interdiff to your patch)
>
> 2) Make a new patch that adds something like this:
>
>
>      virSocketAddr zero;
>
>      /* this creates an all-0 address of the appropriate family */
>      ignore_value(virSocketAddrParse(&zero,
>                                      (VIR_SOCKET_ADDR_IS_FAMILY(addr,AF_INET)
>                                       ? "0.0.0.0" : "::"),
>                                      VIR_SOCKET_ADDR_FAMILY(addr));
>
>      if (routedef->prefix ||
>          VIR_SOCKET_ADDR_IS_FAMILY(mask, AF_INET) ||
>          virSocketAddrEqual(addr, zero)) {
>          prefix = virSocketAddrGetIpPrefix(addr, mask, routedef->prefix);
>      } else {
>          /* neither specified. check for a match with an address of all
> 0's */
>          if (virSocketAddrEqual(addr, zero))
>              prefix = 0;
>          else
>              prefix = virSocketAddrGetIpPrefix(addr, mask, routedef->prefix);
>      }
>
>              virReportError(VIR_ERR_INTERNAL_ERROR,
>                             _("bridge '%s' has prefix=0 for address='%s' which is not supported"),
>                             network->def->bridge, addr);
>
>                 
>              }
>          } else {
>              /* no prefix given, but address was non-zero, so get default
> prefix */
>              prefix = virSocketAddrGetIpPrefix(addr, mask, routedef->prefix);
>          }
>      }
>
>      if (prefix < 0) {
>          virReportError(VIR_ERR_INTERNAL_ERROR,
>                         _("bridge '%s' has an invalid netmask or IP address for route definition"),
>                         network->def->bridge);
>          return -1;
>      }
>
>      if (virNetDevSetGateway(network->def->bridge, addr, prefix, &routedef->gateway) < 0)
>          return -1;
>      return 0;
>
> }
>
> 3) If an ipv6 route for "::/0" really is illegal, then check for that in
> the parser and disallow it there.
>
>
First of all, I am back from my new home inspection trip.  The submittal 
of this patch was a little rushed and suffered as a result.

As you may have noticed, I sometimes (often?) over-engineer my solutions 
(belt, suspenders, elastic waistband, glue-on pants and make sure to 
check them every time you stand up).

I am in complete agreement with you suggested changes for network_conf.* 
and appreciate your patch since you did all of the work.  My plan is to 
roll all of the changes into a single patch which will be resubmitted 
(for v1.0.6 since I missed 1.0.5).

Concerning the patch for bridge_driver.c ... I did not like it when I 
submitted it.

The first thing is that I need to find out why ::/0 is getting an 
error.  The error message is "RTNETLINK answers: File exists" and this 
is exactly the same error message you get if you try to do a second 
static route for an existing route (address + prefix). "/sbin/ip -6 
route" provides little info but "sbin/route -A inet6" is a little more 
helpful.  However, although there are multiple [::]/0 routes, none of 
them are defined for the virtual bridge .... maybe I found a bug ... 
wishful thinking [?]

Next, if ::/0 is invalid, then this needs to be addressed in the parser.

I will re-work and run this up the flag pole again.

Gene