On Fri, Dec 16, 2011 at 10:42 AM, Helmut Schaa <helmut.schaa@xxxxxxxxxxxxxx> wrote: > On Fri, Dec 16, 2011 at 10:35 AM, Dave Taht <dave.taht@xxxxxxxxx> wrote: >> On Fri, Dec 16, 2011 at 9:45 AM, Helmut Schaa >> <helmut.schaa@xxxxxxxxxxxxxx> wrote: >>> [Adding netdev] >>> >>> Maybe someone from the netdev people can shed some light on this. >>> We've got the following code in net/wireless/util.c for frame classification >>> (cfg80211_classify8021d): >>> >>> /* 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; >>> >>> I was just thinking about making use of this for some internal mac80211 >>> QoS handling. But is this code still valid? At least I haven't found anything >>> in the 802.1q code :( >> >> I made use of the above 'feature' while prototyping some Diffserv work >> with iptables. I have no idea if there are users of this obscure >> overloading of priority in userspace.... >> >> The vlan code at least used to do something like this: >> >> net/8021q/vlan.h: * @vlan_qos: vlan priority: (skb->priority << 13) & 0xE000 > > Yeah, I saw that too but +256 would be << 8 and not << 13. Exactly. It's why I used the word 'overload'. Someone in the distant past saw >> 8 was 'reserved', and figured >> 13 was a safe place to stick some valuable bits... or vice versa. > Helmut -- Dave Täht SKYPE: davetaht US Tel: 1-239-829-5608 FR Tel: 0638645374 http://www.bufferbloat.net -- 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
