[lwip-devel] [bug #36153] TCP Cheksum error if LWIP_CHECKSUM_ON_COPY=1

[Alexander]

Follow-up Comment #6, bug #36153 (project lwip):

About Endianness. STM32F103 Reference manual says:

"The bytes are coded in memory in Little Endian format. The lowest numbered
byte in a word
is considered the word’s least significant byte and the highest numbered
byte the most
significant."

I even checked it out with debugger.
I think yes - my STM32 supporting only little-endian.

About Hardware. My CPU does not have any MAC module. 
I use ENC28J60 SPI Stand-Alone Ethernet Controller, all checksum calculations
are made by the software.

About LWIP_CHKSUM_ALGORITHM. I test with 1 and 2 and 3, bug reproduced with
100%. now it set by default (2).

About LWIP_CHKSUM, LWIP_CHKSUM_COPY, LWIP_CHKSUM_COPY_ALGORITHM
I have not defined any user versions of this.

About bug reproducing.
Are you sure that you set TCP_MSS set to 1460?
some info about my reproducing:
100% probability,
if send one packet of 1417 bytes checksum is good
if send two packets 1460 + 1417 checksum is good too.
if last packet has even length (for e.g 1418) checksum is good too.
no matter how many full 1460 packets were sent before this 3 packets. checksum
is incorrect

I will try reproduce bug with a small MSS. In this case it will be more easily
to debug.

and some more info:
I use tcpip_thread (FreeRTOS port from FreeRTOS team). Everything work
perfect
(if LWIP_CHECKSUM_ON_COPY=0) - netif_api, ICMP, DHCP, TCP(test web server) .
I do not think that the problem in porting.



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