the "redirect to localhost" bug


just updating the IP address is fine - part of the pseudo hdr cksum

changing a port / something in the protocol header -> update the csum for sth it doesn't cover (yet)!
software engine doesn't care, does full recalculation
sane hardware doesn't care, does full recalculation
the hw relying on the pseudo hdr cksum is doomed
just "updating" it

result: proto cksum offloading disabled on that hw
last not least em, bge, bnx