• Tom Herbert's avatar
    net: Fix remcsum in GRO path to not change packet · 26c4f7da
    Tom Herbert authored
    Remote checksum offload processing is currently the same for both
    the GRO and non-GRO path. When the remote checksum offload option
    is encountered, the checksum field referred to is modified in
    the packet. So in the GRO case, the packet is modified in the
    GRO path and then the operation is skipped when the packet goes
    through the normal path based on skb->remcsum_offload. There is
    a problem in that the packet may be modified in the GRO path, but
    then forwarded off host still containing the remote checksum option.
    A remote host will again perform RCO but now the checksum verification
    will fail since GRO RCO already modified the checksum.
    
    To fix this, we ensure that GRO restores a packet to it's original
    state before returning. In this model, when GRO processes a remote
    checksum option it still changes the checksum per the algorithm
    but on return from lower layer processing the checksum is restored
    to its original value.
    
    In this patch we add define gro_remcsum structure which is passed
    to skb_gro_remcsum_process to save offset and delta for the checksum
    being changed. After lower layer processing, skb_gro_remcsum_cleanup
    is called to restore the checksum before returning from GRO.
    Signed-off-by: default avatarTom Herbert <therbert@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    26c4f7da
vxlan.c 77.4 KB