Hi Pablo,

I love your patch! Yet something to improve:

[auto build test ERROR on nf/master]

url:    https://github.com/0day-ci/linux/commits/Pablo-Neira-Ayuso/netfilter-nft_exthdr-check-for-IPv6-packet-before-further-processing/20210616-144640
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git master
config: i386-randconfig-s001-20210615 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-341-g8af24329-dirty
        # https://github.com/0day-ci/linux/commit/3e2206f7e73972c0cb8a3b6b8a8e0b636a959c96
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Pablo-Neira-Ayuso/netfilter-nft_exthdr-check-for-IPv6-packet-before-further-processing/20210616-144640
        git checkout 3e2206f7e73972c0cb8a3b6b8a8e0b636a959c96
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   net/netfilter/nft_exthdr.c: In function 'nft_exthdr_ipv6_eval':
>> net/netfilter/nft_exthdr.c:45:6: error: 'skb' undeclared (first use in this function)
      45 |  if (skb->protocol != htons(ETH_P_IPV6))
         |      ^~~
   net/netfilter/nft_exthdr.c:45:6: note: each undeclared identifier is reported only once for each function it appears in


vim +/skb +45 net/netfilter/nft_exthdr.c

    35	
    36	static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
    37					 struct nft_regs *regs,
    38					 const struct nft_pktinfo *pkt)
    39	{
    40		struct nft_exthdr *priv = nft_expr_priv(expr);
    41		u32 *dest = &regs->data[priv->dreg];
    42		unsigned int offset = 0;
    43		int err;
    44	
  > 45		if (skb->protocol != htons(ETH_P_IPV6))
    46			goto err;
    47	
    48		err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL);
    49		if (priv->flags & NFT_EXTHDR_F_PRESENT) {
    50			nft_reg_store8(dest, err >= 0);
    51			return;
    52		} else if (err < 0) {
    53			goto err;
    54		}
    55		offset += priv->offset;
    56	
    57		dest[priv->len / NFT_REG32_SIZE] = 0;
    58		if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
    59			goto err;
    60		return;
    61	err:
    62		regs->verdict.code = NFT_BREAK;
    63	}
    64	

---
0-DAY CI Kernel Test Service, Intel Corporation
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