On Thu, Nov 06, 2003 at 01:39:31PM +0100, francois donzet wrote: > > I've studied the hardware checksum computation. i've > read in include/linux/skbuff.h that when ip->summed is > set to CHECKSUM_HW, skb->csum contains the checksum on > all the packet (as seen by the device). > > The fact is, the ip layer does'nt care about skb->csum > (the checksum is verified from the scratch) but > skb->csum ne is used to compute the final checksum of > tcp (completed with the pseudo header checksum). > > As mentionned in the skbuff.h file, as the skb->csum > covers all the packet, i think skb->csum can't be used > for tcp computing "as is". (as we cover ip header by > this checksum). The comments in "skbuff.h" regarding checksum offloading are a bit confusing. I have posted a detailed description of what really goes on. You can either get it from the list's archives, or from: http://efault.net/npat/docs_and_postings/net_device-features/net_device-features.txt Read this, and if you still have questions, don't hesitate to ask /npat -- As for systems that are not like Unix, such as MSDOS, Windows, the Macintosh, VMS, and MVS, supporting them is usually so much work that it is better if you don't. -- Richard Stallman "GNU Coding Standards" - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
