Re: [PATCH net-next 2/4] virtio-net: reprobe csum related fields for skb passed by XDP

[kernel test robot <lkp@intel.com>]

Hi Heng,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Heng-Qi/virtio-net-a-helper-for-probing-the-pseudo-header-checksum/20230619-190212
base:   net-next/main
patch link:    https://lore.kernel.org/r/20230619105738.117733-3-hengqi%40linux.alibaba.com
patch subject: [PATCH net-next 2/4] virtio-net: reprobe csum related fields for skb passed by XDP
config: x86_64-randconfig-r014-20230619 (https://download.01.org/0day-ci/archive/20230619/202306192151.YMz3NiKw-lkp@intel.com/config)
compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project.git 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
reproduce: (https://download.01.org/0day-ci/archive/20230619/202306192151.YMz3NiKw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306192151.YMz3NiKw-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/net/virtio_net.c:1648:17: error: call to undeclared function 'csum_ipv6_magic'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
                           uh->check = ~csum_ipv6_magic((const struct in6_addr *)&ip6h->saddr,
                                        ^
   drivers/net/virtio_net.c:1648:17: note: did you mean 'csum_tcpudp_magic'?
   include/asm-generic/checksum.h:52:1: note: 'csum_tcpudp_magic' declared here
   csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
   ^
   drivers/net/virtio_net.c:1657:17: error: call to undeclared function 'csum_ipv6_magic'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
                           th->check = ~csum_ipv6_magic((const struct in6_addr *)&ip6h->saddr,
                                        ^
>> drivers/net/virtio_net.c:1695:19: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand]
           } else if (flags && VIRTIO_NET_HDR_F_DATA_VALID) {
                            ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/virtio_net.c:1695:19: note: use '&' for a bitwise operation
           } else if (flags && VIRTIO_NET_HDR_F_DATA_VALID) {
                            ^~
                            &
   drivers/net/virtio_net.c:1695:19: note: remove constant to silence this warning
           } else if (flags && VIRTIO_NET_HDR_F_DATA_VALID) {
                           ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning and 2 errors generated.


vim +1695 drivers/net/virtio_net.c

  1667	
  1668	static int virtnet_set_csum_after_xdp(struct virtnet_info *vi,
  1669					      struct sk_buff *skb,
  1670					      __u8 flags)
  1671	{
  1672		int err;
  1673	
  1674		/* When XDP program is loaded, for example, the vm-vm scenario
  1675		 * on the same host, packets marked as VIRTIO_NET_HDR_F_NEEDS_CSUM
  1676		 * will travel. Although these packets are safe from the point of
  1677		 * view of the vm, to avoid modification by XDP and successful
  1678		 * forwarding in the upper layer, we re-probe the necessary checksum
  1679		 * related information: skb->csum_{start, offset}, pseudo-header csum.
  1680		 *
  1681		 * This benefits us:
  1682		 * 1. XDP can be loaded when there's _F_GUEST_CSUM.
  1683		 * 2. The device verifies the checksum of packets , especially
  1684		 *    benefiting for large packets.
  1685		 * 3. In the same-host vm-vm scenario, packets marked as
  1686		 *    VIRTIO_NET_HDR_F_NEEDS_CSUM are no longer dropped after being
  1687		 *    processed by XDP.
  1688		 */
  1689		if (flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
  1690			err = virtnet_flow_dissect_udp_tcp(vi, skb);
  1691			if (err < 0)
  1692				return -EINVAL;
  1693	
  1694			skb->ip_summed = CHECKSUM_PARTIAL;
> 1695		} else if (flags && VIRTIO_NET_HDR_F_DATA_VALID) {
  1696			/* We want to benefit from this: XDP guarantees that packets marked
  1697			 * as VIRTIO_NET_HDR_F_DATA_VALID still have correct csum after they
  1698			 * are processed.
  1699			 */
  1700			skb->ip_summed = CHECKSUM_UNNECESSARY;
  1701		}
  1702	
  1703		return 0;
  1704	}
  1705	

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