MFC 295296,295297,295298,295299,295300,295301

MFC 295296,295297,295298,295299,295300,295301

295296
    hyperv/hn: Avoid duplicate csum features settings

    - Record csum features in softc, so we don't need to duplicate the
      logic from attach path to ioctl path.
    - Protect if_capenable and if_hwassist changes by main lock.
    - Prefer turn on/off bits in if_hwassist explicitly instead of using
      XOR.

    Reviewed by:        adrian, Hongjiang Zhang <honzhan microsoft com>
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5085

295297
    hyperv/hn: Reorganize TX csum offloading

    - For non-TSO offloading, we don't need to access mbuf to know
      which csum offloading is requested, we can just use the
      CSUM_{IP,TCP,UDP} in the csum_flags.
    - For TSO offloading, we still can depend on CSUM_{TSO4,TSO6}
      in the csum_flags to tell whether the TSO packet is an IPv4
      TSO packet or an IPv6 TSO packet.

    This streamlines csum offloading handling (remove the two goto)
    and allows us the nuke the unnecessary get_transport_proto_type().

    Reviewed by:        adrian, Hongjiang Zhang <honzhan microsoft com>
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5098

295298
    hyperv/hn: Enable IP header checksum offloading

    So that:
    - TCP/IP stack will not do unnecessary IP header checksum for TSO
      packets.
    - Reduce guest load for non-TSO IP packets.

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5099

295299
    hyperv/hn: Enable UDP RXCSUM

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5102

295300
    hyperv/hn: Add sysctls to trust host side UDP and IP csum verification

    Reviewed by:        adrian, Hongjiang Zhang <honzhan microsoft com>
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5103

295301
    hyperv/hn: Obey IFCAP_RXCSUM configure

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5104

git-svn-id: svn://svn.freebsd.org/base/stable/10@301856 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f