[linux-next:master 845/1131] net/core/dev.c:6015:33: error: implicit declaration of function 'skb_ext_find'; did you mean 'skb_ext_copy'?

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   db503865b9ba6284edfee3825846a464cc4f4c61
commit: 8550ff8d8c75416e984d9c4b082845e57e560984 [845/1131] skbuff: Release nfct refcount on napi stolen or re-used skbs
config: um-x86_64_defconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=8550ff8d8c75416e984d9c4b082845e57e560984
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout 8550ff8d8c75416e984d9c4b082845e57e560984
        # save the attached .config to linux build tree
        make W=1 ARCH=um SUBARCH=x86_64

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

Note: the linux-next/master HEAD db503865b9ba6284edfee3825846a464cc4f4c61 builds fine.
      It may have been fixed somewhere.

All errors (new ones prefixed by >>):

   net/core/dev.c: In function 'gro_list_prepare':

quoted

net/core/dev.c:6015:33: error: implicit declaration of function 'skb_ext_find'; did you mean 'skb_ext_copy'? [-Werror=implicit-function-declaration]

    6015 |    struct tc_skb_ext *skb_ext = skb_ext_find(skb, TC_SKB_EXT);
         |                                 ^~~~~~~~~~~~
         |                                 skb_ext_copy
   net/core/dev.c:6015:51: error: 'TC_SKB_EXT' undeclared (first use in this function)
    6015 |    struct tc_skb_ext *skb_ext = skb_ext_find(skb, TC_SKB_EXT);
         |                                                   ^~~~~~~~~~
   net/core/dev.c:6015:51: note: each undeclared identifier is reported only once for each function it appears in
   net/core/dev.c:6020:19: error: dereferencing pointer to incomplete type 'struct tc_skb_ext'
    6020 |     diffs |= p_ext->chain ^ skb_ext->chain;
         |                   ^~
   cc1: some warnings being treated as errors


vim +6015 net/core/dev.c

  5980	
  5981	static void gro_list_prepare(const struct list_head *head,
  5982				     const struct sk_buff *skb)
  5983	{
  5984		unsigned int maclen = skb->dev->hard_header_len;
  5985		u32 hash = skb_get_hash_raw(skb);
  5986		struct sk_buff *p;
  5987	
  5988		list_for_each_entry(p, head, list) {
  5989			unsigned long diffs;
  5990	
  5991			NAPI_GRO_CB(p)->flush = 0;
  5992	
  5993			if (hash != skb_get_hash_raw(p)) {
  5994				NAPI_GRO_CB(p)->same_flow = 0;
  5995				continue;
  5996			}
  5997	
  5998			diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
  5999			diffs |= skb_vlan_tag_present(p) ^ skb_vlan_tag_present(skb);
  6000			if (skb_vlan_tag_present(p))
  6001				diffs |= skb_vlan_tag_get(p) ^ skb_vlan_tag_get(skb);
  6002			diffs |= skb_metadata_dst_cmp(p, skb);
  6003			diffs |= skb_metadata_differs(p, skb);
  6004			if (maclen == ETH_HLEN)
  6005				diffs |= compare_ether_header(skb_mac_header(p),
  6006							      skb_mac_header(skb));
  6007			else if (!diffs)
  6008				diffs = memcmp(skb_mac_header(p),
  6009					       skb_mac_header(skb),
  6010					       maclen);
  6011	
  6012			diffs |= skb_get_nfct(p) ^ skb_get_nfct(skb);
  6013	
  6014			if (!diffs) {

6015				struct tc_skb_ext *skb_ext = skb_ext_find(skb, TC_SKB_EXT);

  6016				struct tc_skb_ext *p_ext = skb_ext_find(p, TC_SKB_EXT);
  6017	
  6018				diffs |= (!!p_ext) ^ (!!skb_ext);
  6019				if (!diffs && unlikely(skb_ext))
  6020					diffs |= p_ext->chain ^ skb_ext->chain;
  6021			}
  6022	
  6023			NAPI_GRO_CB(p)->same_flow = !diffs;
  6024		}
  6025	}
  6026	

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