tree: https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git pr/bpf-tc-misc head: e9a9577c7e49d2e122576b4066f156d8c83556ef commit: 72a4e02bd0f8299a3fae97459ffa3bd3cd1ba1c3 [3/4] bpf, poc: redirect into neigh config: x86_64-randconfig-r034-20200820 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b587ca93be114d07ec3bf654add97d7872325281) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu git checkout 72a4e02bd0f8299a3fae97459ffa3bd3cd1ba1c3 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb) ^ net/ipv4/ip_output.c:185:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb) ^ static 1 warning generated. # https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git/commit/?... git remote add dborkman https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git git fetch --no-tags dborkman pr/bpf-tc-misc git checkout 72a4e02bd0f8299a3fae97459ffa3bd3cd1ba1c3 vim +/ip_finish_output2 +185 net/ipv4/ip_output.c 184 186 { 187 struct dst_entry *dst = skb_dst(skb); 188 struct rtable *rt = (struct rtable *)dst; 189 struct net_device *dev = dst->dev; 190 unsigned int hh_len = LL_RESERVED_SPACE(dev); 191 struct neighbour *neigh; 192 bool is_v6gw = false; 193 194 if (rt->rt_type == RTN_MULTICAST) { 195 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len); 196 } else if (rt->rt_type == RTN_BROADCAST) 197 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len); 198 199 /* Be paranoid, rather than too clever. */ 200 if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) { 201 struct sk_buff *skb2; 202 203 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev)); 204 if (!skb2) { 205 kfree_skb(skb); 206 return -ENOMEM; 207 } 208 if (skb->sk) 209 skb_set_owner_w(skb2, skb->sk); 210 consume_skb(skb); 211 skb = skb2; 212 } 213 214 if (lwtunnel_xmit_redirect(dst->lwtstate)) { 215 int res = lwtunnel_xmit(skb); 216 217 if (res < 0 || res == LWTUNNEL_XMIT_DONE) 218 return res; 219 } 220 221 rcu_read_lock_bh(); 222 neigh = ip_neigh_for_gw(rt, skb, &is_v6gw); 223 if (!IS_ERR(neigh)) { 224 int res; 225 226 sock_confirm_neigh(skb, neigh); 227 /* if crossing protocols, can not use the cached header */ 228 res = neigh_output(neigh, skb, is_v6gw); 229 rcu_read_unlock_bh(); 230 return res; 231 } 232 rcu_read_unlock_bh(); 233 234 net_dbg_ratelimited("%s: No header cache and no neighbour!\n", 235 __func__); 236 kfree_skb(skb); 237 return -EINVAL; 238 } 239 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org