On Thu, 2011-12-15 at 17:30 +0100, Helmut Schaa wrote:
> just noticed a problem with QoS frames in AP mode when mac80211
> relays for example a VOIP frame from STA1 to STA2 the frame will be
> sent out on AC_BE and not on AC_VO.
Hm. You want (T)DLS ;-)
> When the frame is processed in the rx path we will send it to the wireless media
> with the code path below (from rx.c):
>
> if (xmit_skb) {
> /* send to wireless media */
> xmit_skb->protocol = htons(ETH_P_802_3);
> skb_reset_network_header(xmit_skb);
> skb_reset_mac_header(xmit_skb);
> dev_queue_xmit(xmit_skb);
> }
>
> So, skb->priority is the same as the received frame but will be overwritten
> because the the netstack will call ieee80211_select_queue to select the
> appropriate queue which in turn will use cfg80211_classify8021d to select
> the skb->priority and the according queue (from net/wireless/util.c):
>
> unsigned int cfg80211_classify8021d(struct sk_buff *skb)
> {
> unsigned int dscp;
>
> /* skb->priority values from 256->263 are magic values to
> * directly indicate a specific 802.1d priority. This is used
> * to allow 802.1d priority to be passed directly in from VLAN
> * tags, etc.
> */
> if (skb->priority >= 256 && skb->priority <= 263)
> return skb->priority - 256;
>
> switch (skb->protocol) {
> case htons(ETH_P_IP):
> dscp = ip_hdr(skb)->tos & 0xfc;
> break;
> default:
> return 0;
> }
>
> return dscp >> 5;
> }
>
> Unfortunately we don't have an skb priority between 256 and 263 and
> we don't have skb->protocol set to ETH_P_IP here since we've just set
> it to ETH_P_802_3.
>
> I tried using eth_type_trans on the frame but that will "pull" the ethernet
> header and adding an skb_push afterwards seems a little bit ugly to me.
>
> Is it possible to just shortcut the classification if the priority is
> already set?
> Or should we just add 256 to the priority before sending the frame to
> dev_queue_xmit?
>
> What would be an appropriate fix for this?
The >= 256 is already a shortcut, so just adding 256 seems reasonable?
johannes
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