Those following my recent journey on trying to get dcsp info from inner
ipv6 headers to the outer ipv4 tunnel headers and as a result get cake
to classify traffic correctly, may be interested in the following solution:

add "option tos 'inherit'" to the 'wan6' interface definition in
/etc/config/network


I can't find any documentation covering this on the openwrt site which
lead to quite an investigation starting from 'sit.c' in the kernel,
iproute2, busybox, openwrt's netifd and finally the '6in4.sh' that it calls.

The odd thing is that I swear this used to work by default!