I am currently working with multiple Vlan stacking and the behaviour of QinQ in the kernel is not always consistent. On some hardware I have to use set the reorder flag to 0 for the QinQ to be working, while on other, it just work whether this flag is 1 or 0.
I tested with the Fedora core 7 (kernel 2.6.21) on the following machines
Dell PC with Intel Corporation 82540EM Gigabit Ethernet Controller (rev 02)
Compaq laptop with Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10)
On the Dell, I don't need to set the reorder flag to 0 but on the Compaq I need to do it.
Another even stranger thing is that on kernel 2.6.9 I need to set the reorder flag to 0 if I want to stack 3 VLAN but I don't need to do it when I stack only 2 VLAN...
What is the default behaviour ? Is there a bug for the support of one of those network adapter ?
is QinQ officially supported by the Linux kernel ? Someone posted a patch for 2.6.11, is it needed for 2.6.21 ?
The other problem I have is the fragmentation and MTU behaviour: the MTU of a vlan device is the same as the MTU of its ethernet device (1500 in my case), I think it should be less to reflect the size use by the vlan header, no ?
When I use the command "ping -t 2000 <ip address>":
-on a network interface : it works
-on a level 1 vlan: it works
-on a level 2 or higher vlan: it fails
When I use the command "ping -t 1468 <ip address>":
-on a network interface : it works
-on a level 1 vlan: it works
-on a level 2 vlan: it works
-on a level 3 vlan: it fails
When I use the command "ping -t 1464 <ip address>":
-on a network interface : it works
-on a level 1 vlan: it works
-on a level 2 vlan: it works
-on a level 3 vlan: it works
A level 3 vlan has a maximum packet size 4 bytes smaller than a level 2 vlan.
When I change the MTU manually the "ping -t 2000 <ip address>" command works on level 3 vlan, so it should make sense to reduce it when a VLAN device is created, no ?
I am trying to modify a 2.4 kernel to do so, and it seems to work, may I by breaking something else ?
Regards,
Jean-Gregoire
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