On Mar 15, 2013, at 2:22 AM, NGUYEN Xuan Nam wrote:
> However I cannot insert a flow entry with mod_nw_tos:
>
> root@namnx-HP-Z400-Workstation:/home/namnx# ovs-ofctl add-flow system@s1
> priority=65535,idle_timeout=50000,dl_type=0x0800,nw_proto=17,in_port=1,actions=mod_nw_tos:10,output:2
> ovs-ofctl: 10: not a valid TOS
> root@namnx-HP-Z400-Workstation:/home/namnx# ovs-ofctl add-flow system@s1
> priority=65535,idle_timeout=50000,dl_type=0x0800,nw_proto=17,in_port=1,actions=mod_nw_tos:2,output:2
> ovs-ofctl: 2: not a valid TOS
> root@namnx-HP-Z400-Workstation:/home/namnx# ovs-ofctl add-flow system@s1
> priority=65535,idle_timeout=50000,dl_type=0x0800,nw_proto=17,in_port=1,actions=mod_nw_tos:3,output:2
> ovs-ofctl: 3: not a valid TOS
>
>
> In doc file, I see that ToS are between 0 and 255,.
> What did I forget ?
The ovs-ofctl man page does say that, but it also mentions that the bottom two
bits are reserved. The way it says it sort of makes it sound like they will be
ignored (which I believe used to be the case), but it actually gives you the
error you see.
So this is pretty much the same issue you had two weeks ago when Jesse pointed
out that you couldn't use a ToS of 1 because it is an ECN bit. If you read the
OpenFlow spec, you'll see that the mod_nw_tos action is really meant for
modifying the DSCP field, which is only the upper six bits of the former ToS
field. The bottom two bits are used for ECN, and OpenFlow 1.0 specifies no way
to modify these. The values you are trying here -- 10, 2, and 3 -- all use at
least one of those bottom two (ECN) bits.
Short version: Instead of using a number between 0 and 255, try using any
number between 0 and 63 and then multiplying it by 4.
-- Murphy
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