Re: [PATCH nf-next 5/8] net: netfilter: add IPv4 over IPv6 tunnel flowtable acceleration

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

Hi Lorenzo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 734bef548a96e8774d6eef5dfa2026c6edc4e80b]

url:    https://github.com/intel-lab-lkp/linux/commits/Lorenzo-Bianconi/net-netfilter-nf_flow_table-recognize-IPv4-IPv6-in-tunnel-proto-matching/20261029-143512
base:   734bef548a96e8774d6eef5dfa2026c6edc4e80b
patch link:    https://lore.kernel.org/r/20261029-flowtable-sw-accel-ip6ip-sit-v1-5-6a17c54f9fb7%40oss.qualcomm.com
patch subject: [PATCH nf-next 5/8] net: netfilter: add IPv4 over IPv6 tunnel flowtable acceleration
config: m68k-defconfig (https://download.01.org/0day-ci/archive/20261030/202610301255.BRNUBmqH-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 16.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261030/202610301255.BRNUBmqH-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/202610301255.BRNUBmqH-lkp@intel.com/

All warnings (new ones prefixed by >>):

   net/netfilter/nf_flow_table_ip.c: In function 'nf_flow_queue_xmit4':
>> net/netfilter/nf_flow_table_ip.c:891:35: warning: variable 'dst' set but not used [-Wunused-but-set-variable=]
     891 |                 struct dst_entry *dst;
         |                                   ^~~
   net/netfilter/nf_flow_table_ip.c: In function 'nf_flow_queue_xmit6':
   net/netfilter/nf_flow_table_ip.c:1237:35: warning: variable 'dst' set but not used [-Wunused-but-set-variable=]
    1237 |                 struct dst_entry *dst;
         |                                   ^~~


vim +/dst +891 net/netfilter/nf_flow_table_ip.c

   858	
   859	static int nf_flow_queue_xmit4(struct nf_flowtable_ctx *ctx,
   860				       struct sk_buff *skb,
   861				       struct flow_offload_tuple_rhash *tuplehash,
   862				       const struct nf_hook_state *state)
   863	{
   864		struct flow_offload_tuple *other_tuple;
   865		enum flow_offload_tuple_dir dir;
   866		struct nf_flow_xmit xmit = {};
   867		union nf_inet_addr *ip_addr;
   868		struct flow_offload *flow;
   869		struct neighbour *neigh;
   870		struct rtable *rt;
   871	
   872		if (unlikely(tuplehash->tuple.xmit_type == FLOW_OFFLOAD_XMIT_XFRM)) {
   873			rt = dst_rtable(tuplehash->tuple.dst_cache);
   874			memset(skb->cb, 0, sizeof(struct inet_skb_parm));
   875			IPCB(skb)->iif = skb->dev->ifindex;
   876			IPCB(skb)->flags = IPSKB_FORWARDED;
   877			return nf_flow_xmit_xfrm(skb, state, &rt->dst);
   878		}
   879	
   880		dir = tuplehash->tuple.dir;
   881		flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
   882		other_tuple = &flow->tuplehash[!dir].tuple;
   883		ip_addr = (union nf_inet_addr *)&other_tuple->src_v4;
   884	
   885		if (nf_flow_tunnel_push(state->net, skb, other_tuple,
   886					tuplehash->tuple.dst_cache, &ip_addr) < 0)
   887			return NF_DROP;
   888	
   889		switch (tuplehash->tuple.xmit_type) {
   890		case FLOW_OFFLOAD_XMIT_NEIGH: {
 > 891			struct dst_entry *dst;
   892	
   893			xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.ifidx);
   894			if (!xmit.outdev) {
   895				flow_offload_teardown(flow);
   896				return NF_DROP;
   897			}
   898			if (other_tuple->tun.encap_proto ?
   899			    other_tuple->tun.encap_proto == AF_INET6 :
   900			    ctx->tun.inner_proto == IPPROTO_IPV6) {
   901				struct rt6_info *rt6;
   902	
   903				rt6 = dst_rt6_info(tuplehash->tuple.dst_cache);
   904				neigh = ip_neigh_gw6(rt6->dst.dev,
   905						     rt6_nexthop(rt6, &ip_addr->in6));
   906				dst = &rt6->dst;
   907			} else {
   908				rt = dst_rtable(tuplehash->tuple.dst_cache);
   909				neigh = ip_neigh_gw4(rt->dst.dev,
   910						     rt_nexthop(rt, ip_addr->ip));
   911				dst = &rt->dst;
   912			}
   913			if (IS_ERR(neigh)) {
   914				flow_offload_teardown(flow);
   915				return NF_DROP;
   916			}
   917			xmit.dest = neigh->ha;
   918			skb_dst_drop(skb);
   919			skb_dst_set_noref(skb, &rt->dst);
   920			break;
   921		}
   922		case FLOW_OFFLOAD_XMIT_DIRECT:
   923			xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.out.ifidx);
   924			if (!xmit.outdev) {
   925				flow_offload_teardown(flow);
   926				return NF_DROP;
   927			}
   928			xmit.dest = tuplehash->tuple.out.h_dest;
   929			xmit.source = tuplehash->tuple.out.h_source;
   930			break;
   931		default:
   932			WARN_ON_ONCE(1);
   933			return NF_DROP;
   934		}
   935		xmit.tuple = other_tuple;
   936		xmit.needs_gso_segment = tuplehash->tuple.needs_gso_segment;
   937	
   938		return nf_flow_queue_xmit(state->net, skb, &xmit);
   939	}
   940	

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https://github.com/intel/lkp-tests/wiki