Handling flags on vlan(4)

[Gleb Smirnoff]

On Mon, Jan 30, 2006 at 10:39:38PM +0300, Yar Tikhiy wrote:
Y> Presently our vlan(4) driver sets interface's flags to 0 initially
Y> and copies a subset of them from the parent interface when the vlan
Y> interface is attached to its parent.  In particular, copied are flags
Y> IFF_BROADCAST and IFF_MULTICAST.  This approach has an unpleasant
Y> consequence: if you assign IP to vlan before attaching the latter to
Y> its parent, IP won't be properly set up on vlanX because the IP code
Y> does some special things for IFF_BROADCAST and IFF_MULTICAST
Y> interfaces; at least it sets up a broadcast address and joins the
Y> all-hosts group.
Y> 
Y> I can see two ways to deal with the problem.  The ideal and hard
Y> way is to provide hooks to notify upper network stack layers of
Y> changes in interface properties.  However, I doubt if such feature
Y> is called for.  The easy and practical way is to set IFF_BROADCAST
Y> and IFF_MULTICAST on vlan from the beginning and prohibit vlan from
Y> attaching to a non-bcast or non-mcast parent (which wouldn't work
Y> anyway.)

For now we can use the second way. I see no problems with it.

-- 
Totus tuus, Glebius.
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