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

[Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>]

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> 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;
>          |                                   ^~~

ack, I will fix it in v2.

Regards,
Lorenzo

> 
> 
> 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	
> 
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

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