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Re: [lwip-users] pbuf_alloc failed after sometime at driver side.

From: Slava Zilberfayn
Subject: Re: [lwip-users] pbuf_alloc failed after sometime at driver side.
Date: Wed, 15 Oct 2014 21:33:44 -0500

Hello Slava,

Hm, the driver was missing error handling, naturally the missing
packets returned some error. Looking further...

Regards, Slava

Wednesday, October 15, 2014, 3:54:16 PM, you wrote:

SZ> Hello,

SZ> I'm having some issues with lwip stack, or rather with the system as
SZ> whole. At this point I studied the stack relatively well at seems to
SZ> work as intended. However I might be still mistaken, so I'm posting
SZ> here.

SZ> The root of the problems is that sometimes packets are being
SZ> lost for no reason. This can happen even if I connect my PC directly
SZ> to the lwip device.

SZ> When I look at the WireShark trace, it shows as "TCP Previous Segment
SZ> not captured". See attachment. It is certainly not just "not captured", as 
this is
SZ> always accompanied by problems on receiving end and netconn_write
SZ> takes longer time to be completed. Eventually the packets are
SZ> retransmitted, but it could take like 10 seconds, which is not very
SZ> good.

SZ> I already instrumented the driver (lpc17_emac), and logs confirm that all 
SZ> are leaving my device strictly in order. What could be the reason for
SZ> router to ignore my packets? I also tried with two different routers and it
SZ> is the same. Could the problem be with MAC-PHY link?

SZ> Can anybody suggest further steps for debugging?

SZ> Thanks, Slava

Slava Zilberfayn mailto:address@hidden
Phone: 416 7289367

Home Electronics, www.home-electro.com
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