[PATCH] SO_REUSEADDR and SO_REUSEPORT behaviour

[Oleg Moskalenko]

Tim, you are wrong. Read what is "multicast" definition, and read how UDP
and TCP sockets work in Linux 3.9+ kernels.

Oleg .


On Fri, Nov 29, 2013 at 9:59 AM, Tim Kientzle <kientzle at freebsd.org> wrote:

>
> On Nov 29, 2013, at 4:04 AM, Ermal Luçi <eri at freebsd.org> wrote:
>
> > Hello,
> >
> > since SO_REUSEADDR and SO_REUSEPORT are supposed to allow two daemons to
> > share the same port and possibly listening ip …
>
> These flags are used with TCP-based servers.
>
> I’ve used them to make software upgrades go more smoothly.
> Without them, the following often happens:
>
> * Old server stops.  In the process, all of its TCP connections are closed.
>
> * Connections to old server remain in the TCP connection table until the
> remote end can acknowledge.
>
> * New server starts.
>
> * New server tries to open port but fails because that port is “still in
> use” by connections in the TCP connection table.
>
> With these flags, the new server can open the port even though
> it is “still in use” by existing connections.
>
>
> > This is not the case today.
> > Only multicast sockets seem to have the behaviour of broadcasting the
> data
> > to all sockets sharing the same properties through these options!
>
> That is what multicast is for.
>
> If you want the same data sent to all listeners, then
> that is multicast behavior and you should be using
> a multicast socket.
>
> > The patch at [1] implements/corrects the behaviour for UDP sockets.
>
> You’re trying to turn all UDP sockets with those options
> into multicast sockets.
>
> If you want a multicast socket, you should ask for one.
>
> Tim
>
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