[lwip-devel] [task #6849] Test how checksum on copy could be integrated into the stack

[Bill Auerbach]

Follow-up Comment #23, task #6849 (project lwip):

>I disagree: logically a checksum should belong to the segment not the buffer
(of which there may be many).

Don't these many segments have pbufs or pbuf chains?  You'll find there's
less code and computation with the checksum in the pbuf.  Adding the pbuf's
checksums falls out as does the even/odd aspect.  When it's in the segment, is
has to be updated with every segment change.  If segment manipulation is with
chaining pbufs, the checksum moves with the pbuf and there's no overhead to
segment handling.  But your view and knowledge are better than mine - I only
speak from what I did.

I guess it's in Simon's court and when he implements it and it will fall out.
 I've done it already and with 4 or 5 lines of code for full-sized MSS
packets. I think it would work for segments that are chains of pbufs too.  I
didn't do what I didn't need to do (or couldn't test).  Ultimately I had to
move to UDP because TCP still wasn't fast enough.  There was little change to
this move with the checksum in the pbuf.

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