Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Tue, 17 Apr 2012 11:53:35 -0500

Hi Jeff,

On 2012-04-17 Hill, Jeffrey O wrote:
> > I think we should change the way that the RSRV sends out beacon packets
> > from calling connect() followed by send() to just calling sendto().
> 
> As I recall, the determining factor is the "connect"ed state of the
> UDP socket, and not which call send/recv/sendto/recvfrom/etc are used,

True; my suggestion is that by not calling connect() at all we would never see 
the ICMP errors, which I don't believe we're reporting correctly anyway.  IIRC 
RSRV always reports the error giving the IP address that it just connected to, 
whereas an ICMP error must come from an older UDP packet which may have been 
from a different address if we have more than one in the beacon list.

> BTW, in the new server I have allocated a dedicated UDP socket for
> each of the network interfaces that are discovered on the local host,
> and during initialization the list of beacon destination addresses is
> traversed with each of them being assigned to one of these dedicated
> UDP sockets. This avoids any need to connect a UDP socket to a
> destination at any time except, using as I recall a temporary UDP
> socket to determine a local interface used for the beacon's destination,
> during initialization.

Sounds like a better setup, although if you still report errors that wouldn't 
help on subnets that have a (possibly incorrectly configured) machine which is 
sending ICMP responses to broadcast packets.

- Andrew
-- 
Never interrupt your enemy when he is making a mistake.
-- Napoleon Bonaparte

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System