Question on VLAN

[Gregory Nou]

Hi,

What is the difference between
if (m->m_flags & M_VLANTAG)
and
if (ether_type == ETHERTYPE_VLAN) ?

I suppose that m->m_flags are set using ether_type at one point. Still, 
I was not able to find a location in the source where it would happen.

The fact is, I do not understand the difference between these two 
things, nor do I understand why we need the code in if_ethersubr.c[691-717]

Thanks a lot !

-- 
Gregory