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_... 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/3e2206f7e73972c0cb8a3b6b8a8e0b636... 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(a)intel.com&gt; All errors (new ones prefixed by >>): net/netfilter/nft_exthdr.c: In function 'nft_exthdr_ipv6_eval': 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 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 https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org