DSCP & Default Linux routing

Hi all,
I'd appreciate if someone can clarify this for me.

From the source code (ip_forward.c), it seems that skb->priority is
set from the "TOS bits" (mask 0x1E) in the TOS byte. Assume that an end
point application sets the value 0xb8 in the TOS byte (for expedited
forwarding). When this packet passes through a Linux router with
default configuration, it will set the skb->priority to 4 (TOS bits
will be binary 1100), as calculated by the function rt_tos2priority().

If the egress link has 4 priority queues (for example IEEE 802.11e
has 4 access categories), then skb->priority of 4 will map to access
category #2 (Video). But expedited forwarding means it should map onto
access category #3 (Voice), which means skb->priority should be set to
6 or 7. Is this a bug or am I missing something?

Thanks in advance.

-Anand



itsanandr@gmail.com