* Rx checksum offload for fragments
@ 2010-07-27 22:56 Dimitris Michailidis
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From: Dimitris Michailidis @ 2010-07-27 22:56 UTC (permalink / raw)
To: David Miller, netdev
I am looking at a problem with the cxgb4 driver related to Rx checksum
offload and IPv6 fragments. For IP/IPv6 fragments the device provides the
L4 checksum without the pseudo-header, which the driver passes in skb->csum
and sets CHECKSUM_COMPLETE. This works for IP fragments but triggers errors
from netdev_rx_csum_fault for IPv6. The errors are because of this code
in ip6_frag_queue:
if (skb->ip_summed == CHECKSUM_COMPLETE) {
const unsigned char *nh = skb_network_header(skb);
skb->csum = csum_sub(skb->csum,
csum_partial(nh, (u8 *)(fhdr + 1) - nh,
0));
}
which subtracts the checksum for the L3 headers (that HW does not include in
the first place). AFAICS IPv4 does not make a similar adjustment to
skb->csum for its header. Am I missing something here or do IP and IPv6
interpret CHECKSUM_COMPLETE differently? And what should the driver do?
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