LPC1769 LWIP stack assert pbuf->ref=1 fail

[lpcware]

Content originally posted in LPCWare by guc on Mon Jul 22 12:58:14 MST 2013
Hi,
I am running LWIP stack on LPC1769, compiler is IAR, source code is from LPCOpen 1.03 echo sample without RTOS. board is LPCXpresso board. I modified the sample to open 6 tcp server and 6 tcp client socket. the stack assert fail at pbuf->ref==1 (ip.c ln 865 ) after running a while. the timing is random, sometime after send/receive several thousand packet, sometime after several 10K packet. Is there anybody know the reason of it? attached is the opt.h and lwipopts.h Thanks.
Best
Gu

[lpcware]

Content originally posted in LPCWare by guc on Tue Jul 23 13:44:09 MST 2013
Hi, Kevin:
attached is the call stack of this problem. it happens in ip.c ln 825. the pbuf->ref is 2 when this problem happens. I suspect this problem has something to do with tcp retransmit. I found a post similar to my problem http://lists.gnu.org/archive/html/lwip-devel/2012-10/msg00028.html. thanks.
Best
Gu

[lpcware]

Content originally posted in LPCWare by wellsk on Mon Jul 22 15:00:00 MST 2013
The next time this issue happens, can you post the call stack here for when it hit the assertion so I can get an idea of how this happened?
And also - if possible - can you tell me what the number assigned to pbuf->ref is?