Dear mailing list, I would like to manage the VLAN priority in Wireless QOS (WMM). I get the VLAN tag from skb->vlan_tci and I extract the VLAN priority. How I should handle the priority value 0. - Handle this value as no priority request, In this case the frame will sent with the DSCP priority or default (Best effort) - Handle this value as a lowest priority, in this case I Map it to the WMM. For your information, you can found below a discussion on this point with Johannes Berg. Regards. Cedric Voncken. -----Message d'origine----- De : Johannes Berg [mailto:johannes@xxxxxxxxxxxxxxxx] Envoyé : lundi 8 juillet 2013 14:16 À : voncken Cc : linux-wireless@xxxxxxxxxxxxxxx Objet : Re: [PATCH V2] vlan priority handling in WMM On Mon, 2013-07-08 at 12:39 +0200, voncken wrote: > > > The vlan Tag contain three bit for priority. The value 0 indicate > no > > > priority (on this case the VLAN tag contain only VID). The > vlan_tci > > > field is set to zero if the frame do not contain the vlan tag. So > if > > > we have not a vlan tag or no priority in VLAN tag the priority > value > > > is always 0. > > > Yes but don't we know that the vlan_tci field is valid? > > > I don't think you're correct in that 0 means "no priority present", > it actually means "best effort" as far as I can tell. Ignoring the > VLAN tag when the field is 0 would mean we could use a higher priority > from the contents of the frame, which would not be desired? > > I can add a test with the macro vlan_tx_tag_present() to verify if the > vlan_tci field is valid. > I test the value 0 to skip the VLAN priority and use the dscp priority > in this case. The priority 0 in VLAN tag is often use to turn off the > QOS, because not bit is allowed for it. What do you mean by "is often used"? I don't see how that would be the case? Are you saying routers commonly ignore the VLAN priority value if it's 0? That would seem odd? > For me is it correct. Nevertheless, if you prefer, I can test only the > vlan_tci validity and in this case always use the VLAN priority. I don't know! Since you don't seem to really know either, we should ask somebody who knows, I think. Maybe you should Cc netdev with this question on the patch or so? > Sorry I made a mistake 0xE000 >>13 = 0x0007 and not 0x0003, and 7 is > a 3 bits value. Ah yes, I made the same mistake, sorry. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
