Re: [PATCH 3/3] vxlan: virtual extensible lan

On Thu, 04 Oct 2012 08:34:50 +0200
Eric Dumazet [off-list ref] wrote:

On Wed, 2012-10-03 at 21:02 -0700, Stephen Hemminger wrote:

quoted

Since port is always a pair, there is no need to restrict range, unless
there was a broken firewall in the way. One bug there is that random32()
can return 0 which is not a valid port number.  A better fallback
would be a hash of the MAC header.

But using up to 65536 values for the port means that if vxlan traffic
crosses a statefull firewall (eg netfilter with conntrack), this might
need 65536 contexts/sessions.

This is UDP, there is no usable state to be found.
But as a practical matter it only needs to be wide enough to hit the
number of receive channels. Therefore even 64 is probably enough for
most people.

So random32() is not needed.

What might be needed is additional parameters for a vxlan tunnel, to
give an optional range for the source port.

It could be per vxlan without a lot of pain. or just derive it value
from existing ephermeral port range.