[Olsr-users] Received message to big to be forwarded

[Ferry Huberts]

On 17/04/15 16:41, Henning Rogge wrote:
> Jernej,
>
> can you test the following patch?
>
> diff --git a/src/net_olsr.c b/src/net_olsr.c
> index afd24ec..4db54b1 100644
> --- a/src/net_olsr.c
> +++ b/src/net_olsr.c
> @@ -258,7 +258,14 @@ net_outbuffer_push_reserved(struct interface_olsr
> *ifp, const void *data, const
>   int
>   net_outbuffer_bytes_left(const struct interface_olsr *ifp)
>   {
> -  return ifp->netbuf.maxsize - ifp->netbuf.pending;
> +  /* IPv6 minimum MTU - IPv6 header - UDP header - VLAN-Tag */
> +  static int MAX_REMAINING = 1280 - 40 - 8 - 4;
> +  int remaining = ifp->netbuf.maxsize - ifp->netbuf.pending;
> +
> +  if (remaining > MAX_REMAINING) {
> +    return MAX_REMAINING;
> +  }
> +  return remaining;
>   }
>

I don't fully agree with this.
I see why you do it this way but it feels like a band-aid instead of a 
real fix.

This will limit the packet size by about 15% causing more overhead and 
significant more media access for the same traffic volume.

>
>
> Henning
>
> On Fri, Apr 17, 2015 at 4:32 PM, Henning Rogge <(spam-protected)> wrote:
>> Sure,
>>
>> but that is not really a good idea for UDP Multicast... especially in
>> networks with some amount of multicast packet loss.
>>
>> Henning
>>
>> On Fri, Apr 17, 2015 at 4:31 PM, Teco Boot <(spam-protected)> wrote:
>>> Clearing the DF bit enables IP stack fragmenting.
>>>
>>> Teco
>>>
>>>> Op 17 apr. 2015, om 16:08 heeft Henning Rogge <(spam-protected)> het volgende geschreven:
>>>>
>>>> That is what I mentioned earlier... limiting the maximum size of a
>>>> message independent of the packet/MTU size.
>>>>
>>>> Henning
>>>>
>>>> On Fri, Apr 17, 2015 at 4:07 PM, Ferry Huberts <(spam-protected)> wrote:
>>>>>
>>>>>
>>>>> On 17/04/15 16:04, Henning Rogge wrote:
>>>>>>
>>>>>> Yes,
>>>>>>
>>>>>> but the fix does not handle mesh networks with different MTUs.
>>>>>>
>>>>>> the 160 neighbor nodes produces a TC as large as it can... according
>>>>>> to the local MTU. when this message is forwarded (within UDP and olsr
>>>>>> packets) it reaches a node with a link where the MTU is small enough
>>>>>> that the message does not fit through.
>>>>>>
>>>>>
>>>>> Which is what I meant earlier: olsrd should split the packet.
>>>>>
>>>>>
>>>>>
>>>>>> Henning
>>>>>>
>>>>>> On Fri, Apr 17, 2015 at 3:16 PM, Ferry Huberts <(spam-protected)> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 17/04/15 15:11, Jernej Kos wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Hello!
>>>>>>>>
>>>>>>>> On 17. 04. 2015 15:08, Ferry Huberts wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Which version of olsrd are you running?
>>>>>>>>> The 160+ number is suspiciously like a problem that Henning fixed a
>>>>>>>>> while ago.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> We are running olsrd version 0.6.7.1.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> That includes Henning's fix.
>>>>>
>>>>>
>>>>> --
>>>>> Ferry Huberts
>>>>
>>>> --
>>>> Olsr-users mailing list
>>>> (spam-protected)
>>>> https://lists.olsr.org/mailman/listinfo/olsr-users
>>>

-- 
Ferry Huberts