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

From: Vincent Cui
Subject: Re: [lwip-users] pbuf_alloc failed after sometime at driver side.
Date: Thu, 16 Oct 2014 05:12:06 +0000

This is LPC driver issue ...


Vincent Cui
Firmware Engineer Leader
Shanghai Enlogic Electric Technology Co., Ltd.
Room1106, Building A, New Caohejing Business Centre, No.391, Guiping Road, 
Xuhui District, Shanghai, P.R.China
T: +86 21 34612525, M: +86 13482482211
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-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Slava Zilberfayn
Sent: 2014年10月16日 10:34
To: Mailing list for lwIP users
Subject: Re: [lwip-users] pbuf_alloc failed after sometime at driver side.

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 lost
SZ> for no reason. This can happen even if I connect my PC directly to
SZ> the lwip device.

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

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

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
100 Drumlin Circle,
Suite 205
Concord, ON, L4K 3E6

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