[SOLVED] Re: Multiple ARP replies for same address on openwrt module 6.6.69.2024.3-r3

[Matteo Fortini <matteo.fortini@gmail.com>]

Turns out during some updates I had re-installed mesh11sd and, even with 
default config, it was messing with the network configuration in many 
ways. I found it complaining in the logs at some time.

Thank you for your support


Il 09/01/25 12:32, Matteo Fortini ha scritto:
> I apologize, the issue is still present even if I downgrade everything 
> to 23.05.
>
> I don't recollect having modified any batman config. Maybe it's been 
> sometime since I hadn't tried a nmap
>
> DAT is disabled, I've always had issues with "incoming packet with 
> same mac address" and that was the only way to make it go away.
>
> Here's the batctl mj output on all batman nodes.
>
> {"version":"2023.1-openwrt-7","algo_name":"BATMAN_V","mesh_ifindex":12,"mesh_ifname":"bat0","mesh_address":"02:00:06:aa:00:00","hard_ifindex":16,"hard_ifname":"m-11s-0","hard_address":"b4:4b:d6:22:55:1c","tt_ttvn":6,"bla_crc":24857,"mcast_flags":{"all_unsnoopables": 
> false,"want_all_ipv4": false,"want_all_ipv6": 
> false,"want_no_rtr_ipv4": true,"want_no_rtr_ipv6": true,"raw": 
> 24},"mcast_flags_priv":{"bridged": false,"querier_ipv4_exists": 
> false,"querier_ipv6_exists": false,"querier_ipv4_shadowing": 
> false,"querier_ipv6_shadowing": false,"raw": 
> 0},"aggregated_ogms_enabled":true,"ap_isolation_enabled":false,"isolation_mark":0,"isolation_mask":0,"bonding_enabled":false,"bridge_loop_avoidance_enabled":true,"distributed_arp_table_enabled":false,"fragmentation_enabled":false,"gw_bandwidth_down":100,"gw_bandwidth_up":20,"gw_mode":"client","gw_sel_class":50,"hop_penalty":30,"multicast_forceflood_enabled":false,"orig_interval":1000,"multicast_fanout":16}
>
> {"version":"2023.1-openwrt-7","algo_name":"BATMAN_V","mesh_ifindex":13,"mesh_ifname":"bat0","mesh_address":"02:00:03:aa:00:00","hard_ifindex":18,"hard_ifname":"phy1-mesh0","hard_address":"86:af:ca:1a:6b:3b","tt_ttvn":37,"bla_crc":17083,"mcast_flags":{"all_unsnoopables": 
> false,"want_all_ipv4": false,"want_all_ipv6": 
> false,"want_no_rtr_ipv4": true,"want_no_rtr_ipv6": true,"raw": 
> 24},"mcast_flags_priv":{"bridged": false,"querier_ipv4_exists": 
> false,"querier_ipv6_exists": false,"querier_ipv4_shadowing": 
> false,"querier_ipv6_shadowing": false,"raw": 
> 0},"aggregated_ogms_enabled":true,"ap_isolation_enabled":false,"isolation_mark":0,"isolation_mask":0,"bonding_enabled":false,"bridge_loop_avoidance_enabled":true,"distributed_arp_table_enabled":false,"fragmentation_enabled":false,"gw_bandwidth_down":100,"gw_bandwidth_up":20,"gw_mode":"client","gw_sel_class":50,"hop_penalty":30,"multicast_forceflood_enabled":false,"orig_interval":1000,"multicast_fanout":16}
>
> Il 09/01/25 11:55, Sven Eckelmann ha scritto:
>> On Thursday, 9 January 2025 11:31:06 CET Matteo Fortini wrote:
>>> I am noticing random unreachability of hosts in my network, in
>>> particular if I just nmap -sP the whole range.
>>>
>>> I traced it down to ARP poisoning, and the source seems to be two hosts
>>> running batman-adv which are claiming the same address.
>> [...]
>>> issue is, 02:00:06:bb:00:07 is not the right node and the host is
>>> unreachable. The other MAC is the right one.
>>>
>>> If I clear the ARP cache in my source host, then the remote host is
>>> reachable again as it gets the right answer.
>> Might be DAT related. But I am not sure of it. Can you please add the 
>> output
>> of
>>
>> $ batctl mj
>>
>> to see the (batadv interface specific) configuration.
>>
>> This might be helpful for Antonio/Linus. If it is enabled, you could 
>> also try
>> to disable it on all involved hosts via:
>>
>> $ batctl dat disable
>>
>> Just to see if it has any influence on the behavior (to see if there 
>> is any
>> ARP poisoning in the long run - not to solve the intermediate problem).
>>
>>
>>> The problem started after updating to the 24.10RC series of openwrt.
>> When you used 23.05.x before, then this would suggest that it was 
>> introduced
>> somewhere between 2023.1 and 2024.3 (or OpenWrt) somehow.
>>
>> I didn't test it but a quick check in the sources suggest that the 23.05
>> batman-adv sources (from the routing feed) should also work with 
>> 24.10 - so
>> you could actually git-bisect openwrt routing from
>> 6afc0452c2534ed0bc65b59b1fb6fd74439ddf27 to
>> eaa4aba30b017de66bece8ef9d3dde5299fc787d
>>
>> Kind regards,
>>     Sven