in kernel 2.6.x, tun/tap nic supports vlan packets

[zhuyj]

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Hi, all

In kernel 2.6.x, linux depends on nic vlan hardware acceleration to 
insert/extract
vlan tag. In this scene, in kernel 2.6.x

                 _____        ________
    A           |     | B    |        | C
 vlan packets-->| tap |----->|vlan nic|--->
                |_____|      |________|

We hope vlan packets pass through tap and vlan nic from A to c.
But in kernel 2.6.x, linux kernel can not extract vlan tag. It depends
on nic vlan hardware acceleration. It is well known that tap nic has no
vlan acceleration. So in the above scene, vlan packets can not be handled by
tap nic. These vlan packets will be discarded in B. They can not arrive 
at C.

In kernel 3.x, linux can handle vlan packets. It does not depend on nic vlan
hardware acceleration. So the above scene can work well in kernel 3.x.

To resolve the above in kernel 2.6.x, we simulated vlan hardware 
acceleration in
tun/tap driver. Then followed the logic of commit commit 4fba4ca4
[vlan: Centralize handling of hardware acceleration] to modify the vlan 
packets
process in kernel 2.6.x. In the end, the above scene can work well in 
patched
kernel 2.6.x.

Please comment on it. Any reply is appreciated.

Hi, Willy

These 2 patches are for linux2.6.x. These can work well here. Please 
help to merge
linux 2.6.32.x. Thanks a lot.

Best Regards!
Zhu Yanjun