Linux Ethernet Bridging - Apr 2007 - [Bridge] Problem in changed VLAN code can cause systems to hang.

On Thu, 09 Sep 2004 15:16:33 +0200
Mark Ruijter <bridge@siennax.com> wrote:
> I noticed that the VLAN code of kernels >=2.6.8 contain the patch needed
> to mirror link state information from the real device to the vlan device.
> 
> This however causes the system to hang in combination with net-snmpd.
> The last thing that I see is an ioctl(0x8947...
What kind of ethernet devices do you have making use of VLAN?

Stephen,

I noticed that the VLAN code of kernels >=2.6.8 contain the patch needed 
to mirror link state information from the real device to the vlan device.

This however causes the system to hang in combination with net-snmpd.
The last thing that I see is an ioctl(0x8947...

 From the net-snmp code:
---

         if (ioctl(fd, 0x8947, &ifr) >= 0) {
                 new_ioctl_nums = 1;
         } else if (ioctl(fd, SIOCDEVPRIVATE, &ifr) >= 0) {
                 new_ioctl_nums = 0;
         } else {
                 DEBUGMSGTL(("mibII/interfaces", "SIOCGMIIPHY on
%s
failed\n", ifr.ifr_name));
                 return retspeed;
         }

---

I suspected the code below so I commented out the SIOCGMIIPHY line:


  int vlan_dev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
         struct net_device *real_dev = VLAN_DEV_INFO(dev)->real_dev;
         struct ifreq ifrr;
         int err = -EOPNOTSUPP;

         strncpy(ifrr.ifr_name, real_dev->name, IFNAMSIZ);
         ifrr.ifr_ifru = ifr->ifr_ifru;

         switch(cmd) {
         //case SIOCGMIIPHY:
         case SIOCGMIIREG:
         case SIOCSMIIREG:
                 if (real_dev->do_ioctl &&
netif_device_present(real_dev))
                         err = real_dev->do_ioctl(dev, &ifrr, cmd);
                 break;

         case SIOCETHTOOL:
                 err = dev_ethtool(&ifrr);
         }

         if (!err)
                 ifr->ifr_ifru = ifrr.ifr_ifru;

         return err;
}

This fixes the problem. I didn't bother to check what this call actually 
does and why it doesn't work.

Mark.

On Thu, 2004-09-09 at 15:16, Mark Ruijter wrote:
>                  if (real_dev->do_ioctl &&
netif_device_present(real_dev))
>                          err = real_dev->do_ioctl(dev, &ifrr, cmd);
I guess do_ioctl should be called with real_dev as parameter here.

-Tommy

> On Thu, 09 Sep 2004 15:16:33 +0200
> Mark Ruijter <bridge@siennax.com> wrote:
>
>> I noticed that the VLAN code of kernels >=2.6.8 contain the patch
needed
>> to mirror link state information from the real device to the vlan
>> device.
>>
>> This however causes the system to hang in combination with net-snmpd.
>> The last thing that I see is an ioctl(0x8947...
>
> What kind of ethernet devices do you have making use of VLAN?
I suspect the underlying device doesn't support mii interface.
If that is true, then the code is doing the right thing (and net-snmp)
is being too dependant on MII.