On 17/12/15 18:06, Tom Herbert wrote: > I'm not sure that we need bits in VXLAN or any other encapsulation. It > should be sufficient in udp_set_csum that if we already have > CHECKSUM_PARTIAL that can always be used to do local checksum offload. My understandingis that otherwise iptunnel_handle_offloads() will do the inner checksum in sw, because csum_help will be passed as true. It will call skb_checksum_help(). > This is also should be independent as to whether the device does > NETIF_F_HW_CSUM or can offload NETIF_F_IP[V6]_CSUM for encapsulated > packets. I was wary of drivers that declare NETIF_F_IP[V6]_CSUM but don't cope with encapsulated packets. Would they do the right thing if the inner_csum bool in patch 2 just tested for NETIF_F_CSUM_MASK, or do I need to test things like NETIF_F_GSO_UDP_TUNNEL_CSUM? I'm afraid I don't entirely understand the infrastructure here, so I just did the minimal thing I was sure worked, i.e. testing for NETIF_F_HW_CSUM. > It would be nice to have a more formal documentation also. This is a > very powerful mechanism but the math behind it and requirements are > subtle. > > Tom What would be a good place to put such documentation? In Documentation/networking, or as part of the big checksums comment at the top of skbuff.h?
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