tc u32 --- how to match L2 protocols in recent kernels?
- by brownian
I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I mean, no VLAN interfaces are there).
Now, different kernels do it differently. I can be wrong with exact kernel verions ranges, please forgive me. Thanks.
2.6.26
So, in debian, 2.6.26 and up (up to 2.6.32, I believe) --- this works:
tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \
u32 ht 1:64 match ip dst 192.168.1.100 flowid 1:200
Here, "kernel" matches two bytes in "protocol" field with 0x8100, but counts the beginning of ip packet as a "zero position" (sorry for my English, if I'm a bit unclear).
2.6.32
Again, in debian (I've not built vanilla kernel), 2.6.32-5 --- this works:
tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \
u32 ht 1:64 match ip dst 192.168.1.100 at 20 flowid 1:200
Here, "kernel" matches the same for protocol, but counts offset from the beginning of this protocol's header --- I have to add 4 bytes to offset (20, not 16 for dst address). It's ok, seems more logical, as for me.
3.2.11, the latest stable now
This works --- as if there is no 802.1q tag at all:
tc filter add dev internal protocol ip parent 1:0 prio 100 \
u32 ht 1:64 match ip dst 192.168.1.100 flowid 1:200
The problem is that I couldn't find a way to match 802.1q tag so far.
Matching 802.1q tag at past
I could do this before as follows:
tc filter add dev internal protocol 802.1q parent 1:0 prio 100 \
u32 match u16 0x0ed8 0x0fff at -4 flowid 1:300
Now I'm unable to match 802.1q tag with at 0, at -2, at -4, at -6 or like that. The main issue that I have zero hits count --- this filter is not being checked at all, "wrong protocol", in other words.
Please, anyone, help me :-)
Thanks!
