netfilter: use actual socket sk for REJECT action

True to the message of commit v5.10-rc1-105-g46d6c5ae953c, _do_
actually make use of state->sk when possible, such as in the REJECT
modules.

Reported-by: Minqiang Chen <[e-mail]>
Cc: Jason A. Donenfeld <[e-mail]>
Signed-off-by: Jan Engelhardt <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/ipv4/nf_reject.h

···
 #include <net/netfilter/nf_reject.h>
 
 void nf_send_unreach(struct sk_buff *skb_in, int code, int hook);
-void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook);
-
+void nf_send_reset(struct net *net, struct sock *, struct sk_buff *oldskb,
+		   int hook);
 const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
 					     struct tcphdr *_oth, int hook);
 struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,

include/net/netfilter/ipv6/nf_reject.h

···
 
 void nf_send_unreach6(struct net *net, struct sk_buff *skb_in, unsigned char code,
 		      unsigned int hooknum);
-
-void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook);
-
+void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
+		    int hook);
 const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
 					      struct tcphdr *otcph,
 					      unsigned int *otcplen, int hook);

net/ipv4/netfilter/ipt_REJECT.c

···
 		nf_send_unreach(skb, ICMP_PKT_FILTERED, hook);
 		break;
 	case IPT_TCP_RESET:
-		nf_send_reset(xt_net(par), skb, hook);
+		nf_send_reset(xt_net(par), par->state->sk, skb, hook);
+		break;
 	case IPT_ICMP_ECHOREPLY:
 		/* Doesn't happen. */
 		break;

net/ipv4/netfilter/nf_reject_ipv4.c

···
 }
 
 /* Send RST reply */
-void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
+void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
+		   int hook)
 {
 	struct net_device *br_indev __maybe_unused;
 	struct sk_buff *nskb;
···
 	niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
 				   ip4_dst_hoplimit(skb_dst(nskb)));
 	nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
-
-	if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
+	if (ip_route_me_harder(net, sk, nskb, RTN_UNSPEC))
 		goto free_nskb;
 
 	niph = ip_hdr(nskb);

net/ipv4/netfilter/nft_reject_ipv4.c

···
 		nf_send_unreach(pkt->skb, priv->icmp_code, nft_hook(pkt));
 		break;
 	case NFT_REJECT_TCP_RST:
-		nf_send_reset(nft_net(pkt), pkt->skb, nft_hook(pkt));
+		nf_send_reset(nft_net(pkt), pkt->xt.state->sk, pkt->skb,
+			      nft_hook(pkt));
 		break;
 	default:
 		break;

net/ipv6/netfilter/ip6t_REJECT.c

···
 		/* Do nothing */
 		break;
 	case IP6T_TCP_RESET:
-		nf_send_reset6(net, skb, xt_hooknum(par));
+		nf_send_reset6(net, par->state->sk, skb, xt_hooknum(par));
 		break;
 	case IP6T_ICMP6_POLICY_FAIL:
 		nf_send_unreach6(net, skb, ICMPV6_POLICY_FAIL, xt_hooknum(par));

net/ipv6/netfilter/nf_reject_ipv6.c

···
 	return 0;
 }
 
-void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
+void nf_send_reset6(struct net *net, struct sock *sk, struct sk_buff *oldskb,
+		    int hook)
 {
 	struct net_device *br_indev __maybe_unused;
 	struct sk_buff *nskb;
···
 		dev_queue_xmit(nskb);
 	} else
 #endif
-		ip6_local_out(net, nskb->sk, nskb);
+		ip6_local_out(net, sk, nskb);
 }
 EXPORT_SYMBOL_GPL(nf_send_reset6);
 

net/ipv6/netfilter/nft_reject_ipv6.c

···
 				 nft_hook(pkt));
 		break;
 	case NFT_REJECT_TCP_RST:
-		nf_send_reset6(nft_net(pkt), pkt->skb, nft_hook(pkt));
+		nf_send_reset6(nft_net(pkt), pkt->xt.state->sk, pkt->skb,
+			       nft_hook(pkt));
 		break;
 	default:
 		break;

net/netfilter/nft_reject_inet.c

···
 					nft_hook(pkt));
 			break;
 		case NFT_REJECT_TCP_RST:
-			nf_send_reset(nft_net(pkt), pkt->skb, nft_hook(pkt));
+			nf_send_reset(nft_net(pkt), pkt->xt.state->sk,
+				      pkt->skb, nft_hook(pkt));
 			break;
 		case NFT_REJECT_ICMPX_UNREACH:
 			nf_send_unreach(pkt->skb,
···
 					 priv->icmp_code, nft_hook(pkt));
 			break;
 		case NFT_REJECT_TCP_RST:
-			nf_send_reset6(nft_net(pkt), pkt->skb, nft_hook(pkt));
+			nf_send_reset6(nft_net(pkt), pkt->xt.state->sk,
+				       pkt->skb, nft_hook(pkt));
 			break;
 		case NFT_REJECT_ICMPX_UNREACH:
 			nf_send_unreach6(nft_net(pkt), pkt->skb,