[Winpcap-users] TCP CHECKSUM OFFLOAD
guy at alum.mit.edu
Tue Aug 16 21:22:08 GMT 2005
On Aug 16, 2005, at 1:46 PM, Sabbiolina wrote:
> Sending appropriate OID to NIC can I switch to offload checksum ?
You'd have to see what the Microsoft documentation, or the vendor for
the NIC, says. WinPcap doesn't turn offloading on or off.
> How to analyze those packets ?
"Analyze" in what sense?
If you capture them with WinPcap, then:
if the packet was sent *to* the machine running the WinPcap-based
application (WinDump, Analyzer, Ethereal, etc.) from another machine
with a network adapter that does checksum offloading, then the packet
will look like any other TCP segment, as the adapter added a checksum
if the packet was sent *by* the machine running the WinPcap-based
application on an adapter that does checksum offloading, then the
packet will (as per my mail) probably not have a valid TCP checksum,
so you can't check the checksum, but everything else about the packet
should be normal.
> I see an extra word after TCP packet captured and original tcp
> checksum changed,
What do you mean by "an extra word"? Do you mean the packet is a
"word" (2 bytes? 4 bytes?) longer than you expect it to be?
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