On Tue, May 29, 2007 at 01:58:13PM -0700, Stephen Hemminger wrote: > The flag NETIF_F_HW_SUM is being misused. The definition says that the device > is capable of checksumming any packet. When in fact from usage it seems to > imply that the device is capable of doing IPV6 as well as IPV4.
That would be a problem. > Some devices like 8139too do "fake checksum offloading" because they always > have to copy > the packet. > > Some devices like via-rhine, don't really checksum but if they see > CHECKSUM_PARTIAL then they > copy. This is bogus, they should just let higher layer do checksum/copy. Actually this is OK because if they have to copy it then it's cheaper to checksum it there. Both of these should be able to support all protocols. > Devices like e1000, and bnx2 are broken because they assume only TCP/UDP and > IPV4/IPV6. > The definition of the flag says other protocols should work, but they > probably send the > hardware into a state of confusion. I just checked e1000 and it's correct as it does use the csum_offset when doing TX offload. However, you're definitely right that bnx2 seems to be broken. > A few devices take a offset, starting point, and insertion point. This looks > like > the correct model. But no upper layer protocols other than IPV4/IPV6 can do > checksum > offload at present, so it seems moot. I could easily whip up a patch to get GRE to use it for a start :) > IMHO the correct solution would be to get rid if NETIF_F_HW_SUM and make a > new flag > NETIF_F_IPV6_SUM. Devices that can checksum both could do > NETIF_F_IPV4_SUM|NETI_F_IPV6_SUM. We should definitely keep NETIF_F_HW_SUM for sane hardware such as the e1000. Unfortunately we may just have to invent IPV6_SUM for the broken ones. Ccing Michael to see if the bnx2 chip can actually do offset-based checksum offload. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
