Dave Marquardt <[EMAIL PROTECTED]> writes:
> > What about associating a flow-label with each open socket (which is
> > used for all outgoing packets), and supporting these three operations:
> >
> > 1. Make up a new, unique, flow-label and associate it with the given
> > socket.
> >
> > 2. Copy the flow-label association from one socket to another.
> >
> > 3. Reset the flow-label for a socket to zero.
>
> I can think of a couple of others:
>
> 4. Retrieve the flow label from a socket.
>
> 5. Set the flow label on a socket to a specific value.
The problem with (5), I think, is that it makes it really difficult for
the networking code to know when a flow-label is no longer used, so
that it can be reused safely during (1) processing.
> These together should allow UDP servers to associate flow labels with
> particular traffic.
You *can* do the same thing with only 1-3. Whenever you want to copy a
flow-label and use it later, you create a new socket, use (2) to save
the flow-label you are interested in, and you can use (2) to restore
it again later.
If you allow (5), if I can somehow discover the flow-labels used by
other users' processes (by magic or by passive sniffing of some
intermediate cable or something), then I can use (5) to assign the
same flow-label to my own sockets and cause trouble by violating any
requirements on flow-label use that the other user's processes and
friendly routers try to enforce. Is that a problem worth worrying
about?
Not doing (5) helps the network code to stay in full control of the
flow-label allocation; there would be no way to collide with the
flow-labels allocated to unrelated processes, neither by mistake or by
malice.
/Niels
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