Re: [lwip-users] Re: Checksum calculations

[Jonathan Larmour]

Sourath Roy wrote:
> Hello!
> I am porting some network applications from Linux to lwIP stack. So far
> the progress has been good, but while some stress tests I often see
> checksum errors being reported by the network sniffer.

I presume this occurs only with data sent from lwIP to linux.

> The ethernet chip
> does not have any checksum generation support, and so we rely on the
> software algorithms available inside lwIP library. Have you guys seen
> such a problem before? Endianness on the system is little-endian, but I
> believe the algorithm already takes care of that.

The checksum generation has not changed and has been working fine for a
long time, including under stress. More likely it is not the checksum that
is the problem, but rather the data being checksummed. For example, if you
are changing data after it was sent, but did not tell the stack to copy the
data. Or of course something in the ethernet driver implementation.

I would suggest you check the payload for corruption, and if there is
corruption, what pattern does the corruption have e.g. random, only after a
certain point in the packet, etc.

Jifl
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