[Samba] Network Meltdown after Samba 4.9.0 Upgrade

Jeremy Allison jra at samba.org
Mon Sep 17 19:50:13 UTC 2018

On Sat, Sep 15, 2018 at 12:52:52PM +1000, Reuben Farrelly via samba wrote:
> Hi,
> Last night I attempted to upgrade from Samba 4.8.5 to 4.9.0, with disastrous
> results.  Upon starting Samba 4.9.0 my entire network came to a screaming
> halt a few seconds later, and upon shutting Samba down it came back to life
> again.
> Just to be sure this wasn't a coincidence, I then started Samba again. Once
> again all connectivity stopped, but came back as soon as I was able to shut
> down Samba.
> Network switches were all logging that they were shutting down physical
> ports due excessive numbers of broadcast packets being seen, and a Wireshark
> capture from my PC verified that indeed there really was a broadcast storm
> happening that was triggering this.
> The capture showed that upon startup Samba 4.9.0 was sending thousands and
> thousands of broadcast packets onto the wire in very quick succession.
> Wireshark counted around 6500 broadcasts in about 300ms. The packets are all
> Host Announcement packets sent from the IPv4 address of the host to the
> broadcast address of the subnet the Samba is on.
> Upon reverting back to 4.8.5 with no other config changes, everything is
> back to normal again.

Reuben, Andrew and I think that the following is the correct
patch rather than the simple revert (it keeps the compiler overflow fix
in place).

Can you test and confirm ?


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