[pve-devel] hetzner bug with pve-firewall

alexandre derumier aderumier at odiso.com
Tue Sep 14 02:27:33 CEST 2021


Hi, I just send another patch,

without ebtables, but with disabling unicast_flood on vm bridge ports. 

maybe can you try it ?


Le dimanche 12 septembre 2021 à 12:37 +0200, Josef Per Johansson a
écrit :
> Hi,
> 
> Yeah sure! It seems a bit better than my hack!
> 
> Yeah I meant the mac-address-table, my bad.
> 
> Sent from Nine
> ________________________________
> From: alexandre derumier <aderumier at odiso.com>
> Sent: Friday, 10 September 2021 18:19
> To: Proxmox VE development discussion
> Subject: Re: [pve-devel] hetzner bug with pve-firewall
> 
> 
> Hi,
> 
> Le vendredi 10 septembre 2021 à 12:53 +0200, Josef Johansson a
> écrit :
> > 
> > 
> > I have a patch for the source code regarding only allowing the VMs
> > MAC
> > in ebtables for incoming traffic also.
> 
> I just send a patch too for incoming traffic, maybe could you try it
> ?
> 
> 
> 
> > > Traffic is only broadcasted to MAC B if the ARP-table in the
> > > switch
> > > times out.
> > > 
> > > Which makes this problem a hell to diagnose :-)
> 
> to be exact, if the mac-address-table timeout in the switch. (switch
> don't have arp, until it's a router)
> That's why in general, switch need to be configured with mac-address-
> table aging-time (2h for exemple)  > than arp timeout on servers.
> 
> Like this, if no traffic occur on servers, and arp is timeout out,
> server is sending a new arp request, and the switch see the arp reply
> with the mac address,
> (and no expiration in mac-address-table).
> 
> Looking at hetzner problem, the tcpdump send by users show really
> stranges mac address vendor. (sound like forged flood).
> Anyway, they should fix this, with static mac in their switch, as
> they
> known allowed mac by server anyway.
> (Until they have poor cheap switch without mac filtering ....)
> I wonder if they are not only filtering/detecting the wrong mac on
> their gateway. (as here, we send tcp reset to an external ip, going
> through the gateway)
> 
> 
> 
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