svn commit: r280971 - in head: contrib/ipfilter/tools share/man/man4 sys/contrib/ipfilter/netinet sys/netinet sys/netipsec sys/netpfil/pf

Andrew Gallatin gallatin at cs.duke.edu
Thu May 14 20:18:44 UTC 2015


On 04/02/2015 11:24 AM, Hans Petter Selasky wrote:

> If we are transmitting using TSO, will the network adapter increment the 
> IP ID field somehow? What happens if an outgoing IP packet resulting 

Sorry for the delayed reply; I was just catching up on FreeBSD email,
and I'm not sure that the above question was ever answered.

The NIC is *required* to increment the IP ID by the Microsoft NDIS LSO
spec.  As I recall, this is checked for by WHQL tests.  So any NIC
whose vendor ships Windows drivers & supports TSO should be
incrementing the IP ID.  Even vendors who do not ship Windows drivers
often refer to these NDIS specs, since they are the best documentation
of many stateless offloads.

Also note that NICs which support the "newer" LSOv2 spec only use the
lower 15 bits of the IP ID space.

See: "Offloading the Segmentation of Large TCP Packets" at
https://msdn.microsoft.com/en-us/library/windows/hardware/ff568840(v=vs.85).aspx

Best regards,

Drew


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