[NET]: Update comments for skb checksums
Rusty (whose comments we should all study and emulate :) pointed out that our comments for skb checksums are no longer up-to-date. So here is a patch to 1) add the case of partial checksums on input; 2) update partial checksum case to mention csum_start/csum_offset; 3) mention the new IPv6 feature bit. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -65,13 +65,20 @@
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* is able to produce some skb->csum, it MUST use COMPLETE,
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* not UNNECESSARY.
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*
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* PARTIAL: identical to the case for output below. This may occur
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* on a packet received directly from another Linux OS, e.g.,
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* a virtualised Linux kernel on the same host. The packet can
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* be treated in the same way as UNNECESSARY except that on
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* output (i.e., forwarding) the checksum must be filled in
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* by the OS or the hardware.
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*
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* B. Checksumming on output.
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*
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* NONE: skb is checksummed by protocol or csum is not required.
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*
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* PARTIAL: device is required to csum packet as seen by hard_start_xmit
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* from skb->transport_header to the end and to record the checksum
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* at skb->transport_header + skb->csum.
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* from skb->csum_start to the end and to record the checksum
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* at skb->csum_start + skb->csum_offset.
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*
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* Device must show its capabilities in dev->features, set
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* at device setup time.
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@ -82,6 +89,7 @@
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* TCP/UDP over IPv4. Sigh. Vendors like this
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* way by an unknown reason. Though, see comment above
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* about CHECKSUM_UNNECESSARY. 8)
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* NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
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*
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* Any questions? No questions, good. --ANK
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*/
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