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Re: [lwip-users] LWIP problems


From: Trampas Stern
Subject: Re: [lwip-users] LWIP problems
Date: Mon, 22 Jun 2020 14:31:43 -0400

I got a wireshark dump from customer and it looks like there is a lot of ARP messages on their network.

Does the ARP broadcast consume a connection? 

In the image below our device is 10.2.65.250 and it is looking like we are getting duplicate requests (line 116,129)  from the client. 
image.png

The network has lots of ARP requests... 
image.png

It appears that a device is asking for 10.2.65.1, which might be a mistake as the gateway is 10.2.64.1 with  netmask of 255.255.254.0 

I am wondering if the ARP traffic is overwhelming lwip... 

Thanks




On Tue, Jun 16, 2020 at 9:12 AM Terry Barnaby <terry@beam.ltd.uk> wrote:
Hi,

We did see an issue like this on one of our LWIP systems. Our system's networking was going very slow on a customers site.

In our case it was due to the customers network having a lot of video multicast packets and a simplistic LWIP Ethernet driver. The LWIP Ethernet driver was enabling the use of multicast packets (which we were using for auto discovery), but it did so by allowing any packet through for LWIP processing.
We fixed this by modifying the LWIP Ethernet driver to only allow the particular multicast packets through (appropriate IP address).

Terry
On 15/06/2020 18:30, Trampas Stern wrote:
I can not access the customer network to root cause so I am working on modifying LWIP to get some stats on the various packet types to see if the issue is the broadcast messages, or something else. 

I just find that LWIP code so confusing it takes me forever to figure out the N layers of abstraction and such to understand what is going on.  

Trampas

On Mon, Jun 15, 2020 at 1:18 PM Stephen Cowell <s.cowell@plasmability.com> wrote:
We have asked customers to reduce the mask and create a smaller subnet... this has worked for us. 
--
Stephen Cowell
Project Manager/Engineer
Plasmability LLC
Office (512) 267-7087
Cell  (512) 632-8593
www.plasmability.com
On 6/15/2020 11:05 AM, Trampas Stern wrote:
We finally shipped the product using LWIP and now customers are complaining that the network interface is not working properly on their network.  They can not load webpages as it appears too slow of a connection. 

The only thing I can figure out is they have enough broadcast and ARP packages that it overwhelms our ability in LWIP to handle the messages but I am not sure.   

Has anyone encountered these problems before? 

Thanks
Trampas

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-- 
Dr Terry Barnaby            BEAM Ltd
Phone: +44 1454 324512      Northavon Business Center,
Email: terry@beam.ltd.uk    Dean Rd, Yate
Web: www.beam.ltd.uk        Bristol, BS37 5NH, UK
BEAM Engineering: Instrumentation, Electronics/Software/Systems
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