hi,

> > > i think you also need zero ui->ui_sum in the else {}, otherwise you could
> > > just have garbage.
> > 
> > for what?
> > in that case, the ui_sum should never used by anyone, afaik.
> 
> you still want it to "hit the wire" as zero don't you,

no.

> otherwise the receive
> side (including things like tcpdump) thinks you're doing checksums.

can you explain why it's a problem?
"receive side" should be ourselves.  it should know about checksum omission.

YAMAMOTO Takashi