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Tobias Waldekranz
366cc4c8e7
By default, Linux will map an IP packet's TOS field into skb->priority
when acting as a router. Unfortunately this is only globally
configurable (per network namespace), which leaves us with the
following dilemma:
If we keep reclassification enabled, then a setup like this...
vlan1 vlan2
\ /
br0
/ \
e1 e2
...would likely not work as expected because any priority information
from hardware, that might be mapped to skb->priority via vlan1's
ingress-qos-map, would then be replaced by the standard TOS-mapping on
the routing boundary.
On the other hand, if we disable reclassification, then we won't be
able to source priority information from the TOS field when no other
source is available, as is the case when the source interface is a
regular NIC.
Given that the primary use-case is to run on switchdev ports, we will
most likely always have priority information available from hardware,
which is why we opt to disable the reclassification.
If this ever becomes configurable per interface, then we could open up
the configuration to let users define the policy of which layer's
priority should take precedence.