On 01/15/2014 06:15 AM, Antonio Quartulli wrote:
> On 15/01/14 12:13, cmsv wrote:
>> inline:
>>
>> On 01/15/2014 02:00 AM, Martin Hundebøll wrote:
>>> Hi,
>>>
>>> On 2014-01-14 23:04, cmsv wrote:
>>>> batman_adv: bat0: The MTU of interface adhoc0 is too small (1528) to
>>>> handle the transport of batman-adv packets. Packets going over this
>>>> interface will be fragmented on layer2 which could impact the
>>>> performance. Setting the MTU to 1546 would solve the problem.
>>>
>>> Did you enable network coding? That would explain the message, as NC
>>> uses a larger header to make decoding possible at the receiver side.
>> Yes it is enabled by default as it was with batavd 2013.4.0 with 1528 mtu
>>>
>>> As far as I can tell from a quick look in packet.h, the required MTU
>>> should be 1532 now. (10 bytes unicast + 8 bytes extra for unicast_4addr
>>> + 14 ethernet = 32 bytes). Or am I bad at counting bytes?
>>
>> Regardless of being properly counted or not; dmesg outputs the message
>> complaining about the need to make mtu 1546.
> 
> If you disable network coding the message will change.
> 
> The overhead is dynamic depending on NC being enabled or not and now the
> message in dmesg tells you exactly what MTU you need.


Yes i understand that but it keeps on increasing.
[   28.600000] batman_adv: bat0: The MTU of interface adhoc0 is too
small (1546) to handle the transport of batman-adv packets. Packets
going over this interface will be fragmented on layer2 which could
impact the performance. Setting the MTU to 1560 would solve the problem.

> 
> Cheers,
> 
>