On Fri, Mar 11, 2016 at 11:20 AM, Edward Cree <ec...@solarflare.com> wrote: > On 20/02/16 19:51, Tom Herbert wrote: >> Right. To use LCO with TSO we would need to ensure that all packets >> are the same size so that the UDP length field and thus checksum are >> constant for all created segments. But this property this would also >> make any payload lengths in headers constant for all packets so that >> the only fields that need be set per generated packet would be the TCP >> sequence number and checksum. This simplifying assumption could be >> used to make a very protocol-generic GSO/TSO (up to the transport >> header)! >> >> Conceptually, a device would just need to know the start of the >> packet, the offset of the transport header, and the size of each >> segment. Any bits from the start of the packet to the beginning of the >> transport header are just copied to each segment, so any combination >> of encapsulation/network protocols is supported as long as they are >> constant for each segment (e.g. MPLS, NSH, etc. are on the horizon for >> needing TSO support). > Tom, > > Are you planning to / working on implementing this? If not, I might have a > crack at it; I've talked to our firmware guys and (provisionally) we think > we can support it in current sfc hardware. > Or were there any blocking problems raised in the thread? My understanding > of the IP ID issue was that it only matters for the inner frame, because > the rest aren't TCP (so hopefully no-one is doing SLHC on them). But I may > have missed something. > Right, then the interface would need to just include the offset of the IP ID. But doesn't this break using LCO with GSO though-- i.e. the outer checksum and inner checksum still need to be updated per packet so we need to tell device where outer checksum(s) is.
Thanks, Tom > -Ed
