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Re: [Samba] Network Meltdown after Samba 4.9.0 Upgrade

On 15/09/2018 6:40 pm, Rowland Penny via samba wrote:
On Sat, 15 Sep 2018 12:52:52 +1000
Reuben Farrelly via samba <samba@xxxxxxxxxxxxxxx> wrote:
thunderstorm ~ # testparm
Load smb config files from /etc/samba/smb.conf
rlimit_max: increasing rlimit_max (1024) to minimum Windows limit
(16384) Processing section "[homes]"
Processing section "[root]"
Processing section "[photos]"
Processing section "[store]"
Loaded services file OK.

Press enter to see a dump of your service definitions

# Global parameters
          domain master = Yes
          security = USER
          server role = standalone server

NOTE: I have shrunk your smb.conf for clarity.

It is undoubtedly for a 'standalone server', so why does it also have
the line 'domain master = Yes' ??
It cannot be both, I would suggest removing this line.

Sure - valid point. I've removed that statement now as you're right, it's not needed, and things are much better. Fingers crossed!

What I have observed now was:

- Upon startup of Samba 4.9.0 again I saw again a repeated burst of broadcast packets
- Switches once again went into storm-control mode and shut ports down
- The environment recovered, but this time things stabilised and has been OK for the last hour since. Things seem to be working fine now.

Regardless of if the config was right or not (I agree that the setting in my case was wrong and unnecessary), this is a regression, because it causes an unexpected and undocumented change in behaviour compared to previous versions of the code.

I also wonder why network broadcasts don't seem to be rate limited by Samba. I can't imagine any valid use case where any application would blast thousands of broadcasts per second out onto the wire, regardless of the configuration or misconfiguration of the application.

At the very least this needs a mention in the release notes, especially given the potential this has to cause an outage. Things may have changed (and change is usually good), but the least that can be done is people are given a one line heads up.


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