Re: Fwd: Wrong beacon source IP address

[Michael Davidsaver <mdavidsaver@gmail.com>]

On 12/18/2015 03:13 AM, Ralph Lange wrote:
> Dear colleagues,
> 
> I think Anze's got a point here.

Agreed.  Beacons should appear to come from the appropriate source address.  I should note that RSRV tries to put the correct interface address in the message body (and succeeds in at least some cases).

http://bazaar.launchpad.net/~epics-core/epics-base/3.16/view/head:/src/ioc/rsrv/online_notify.c#L263

> What are the consequences? Are there any?

I doubt there are any real consequences either to the present behavior, or to fixing it.



> Cheers,
> ~Ralph
> 
> 
> -------- Forwarded Message --------
> Subject: 	Wrong beacon source IP address
> From: 	Anze Zagar <anze.zagar@cosylab.com>
> 
> 
> I was playing around with CA beacons a little bit, and observed some
> surprising behaviour.
> 
> On my system I have three network interfaces:
> 
> eth0
>   inet addr:10.5.4.190  Bcast:10.5.7.255  Mask:255.255.248.0
> 
> vmnet1
>   inet addr:192.168.103.1  Bcast:192.168.103.255  Mask:255.255.255.0
> 
> vmnet8
>   inet addr:172.16.209.1  Bcast:172.16.209.255  Mask:255.255.255.0
> 
> 
> Now if I run EPICS IOC, it will send beacons to all three broadcast
> addresses, however the source address (in the IP frame of the beacon UDP
> packet) will in all three cases correspond to the IP address of the
> first interface. Thus with EPICS_CA_AUTO_ADDR_LIST=yes, source IP is
> always 10.5.4.190.
> 
> And if I configure, e.g.:
> 
> export EPICS_CA_AUTO_ADDR_LIST=no
> export EPICS_CA_ADDR_LIST="192.168.103.255 172.16.209.255 10.5.7.255"
> 
> source IP is 192.168.103.1 for all three subnets (see also the attached
> wireshark screenshot).
> 
> I noticed that this may impact some CA client implementations, because
> they expect beacon to have the source address corresponding to existing
> CA connections (which will obviously not be the case for second and
> third subnet). Effectively, it will ignore all beacons and check for the
> IOC availability by pinging them instead. Additionally, it will also not
> reuse CA connections for multiple PVs hosted on the same server.
> 
> I observed this on EPICS 3.14.12.5. Do you know, if this is something
> known or expected?
>

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