This is a fun example showing how to use BPF to preserve DSCP values across
an encapsulating interface, such as Wireguard. It relies on the
encapsulation layer preserving the skb->hash value across the
encapsulation, which is commonly the case on kernel encapsulation
protocols (including Wireguard), and uses a pair of TC BPF programs and a
map to re-match the packets after encapsulation and add back the DSCP
value.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
