[lwip-users] low_level_output() tries to send data bigger than MSS

[Simeon Trifonov]

Hello,

I have a problem with the usage of LWIP and I cannot find a solution 
alone. My function low_level_output() sometimes tries to send data 
bigger than MSS. The function copies in the send buffer of the device 
all chained buffers from type pbuf. In the most cases all works fine. 
But sporadically, the size of all the data becomes bigger than MSS. Here 
is one example what I have seen when I debugged the problem. The pointer 
p of my function low_level_output() points to a buffer that has a len = 
54 and tot_len = 1514. The pointer next also is valid (not NULL) and 
points to the next pbuf. But this next pbuf has a len = 1460 and tot_len 
= 1460. It doesn't match to the precious buffer.
Here are some settings in my code:
TCP_MSS = 1460
TCP_WND = 8 * TCP_MSS
TCP_SND_BUF = 8 * TCP_MSS
I'm using RAW API without OS.
Probably more information from me will be needed, but I don't know what 
is important in this case...
Please, help!
Best regards!

--
Simeon Trifonov
Head of department "Development"

AMK Drives and Controls Ltd.
Bulgaria / Gabrovo

Phone:   +359 (0)66 819125
Fax:     +359 (0)66 819101
E-Mail:  address@hidden
Web:     www.amk-drives.bg