pf: Retrieve DSCP value from the IPv6 header

[kp]

Summary

Teach pf to read the DSCP value from the IPv6 header so that we can
match on them.

MFC after: 2 weeks
Sponsored by: Rubicon Communications, LLC ("Netgate")

[donner]

sys/netpfil/pf/pf.c

6387

So you are extracting "DSCP" and "Currently unused" but you mask out the unused bits without shifting them away? If the CU bits are kept, but masked, that is fine.

It might be more easily readable by

pd.tos = (ntohl(h->ip6_flow) >> 20) & 0xfc;

[kp]

sys/netpfil/pf/pf.c

6387

Grabbing the DSCP bits and ignoring the ECN bits, yes.

I think I agree that your way is more readable. so I'll update that.

[ae]

sys/netpfil/pf/pf.c

6387

This variant of

6387

We have several places in the code where the same expression are used, probably it would be good to add some macros to get and set this value.

[kp]

Simplify retrieving the DSCP bits