ipv6: tcp_ipv6 policy route issue

The issue raises when adding policy route, specify a particular
NIC as oif, the policy route did not take effect. The reason is
that fl6.oif is not set and route map failed. From the
tcp_v6_send_response function, if the binding address is linklocal,
fl6.oif is set, but not for global address.

Acked-by: Hannes Frederic Sowa <[e-mail]>
Signed-off-by: Wang Yufen <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv6/tcp_ipv6.c

···
 #endif
 
 static void tcp_v6_send_response(struct sk_buff *skb, u32 seq, u32 ack, u32 win,
-				 u32 tsval, u32 tsecr,
+				 u32 tsval, u32 tsecr, int oif,
 				 struct tcp_md5sig_key *key, int rst, u8 tclass,
 				 u32 label)
 {
···
 	__tcp_v6_send_check(buff, &fl6.saddr, &fl6.daddr);
 
 	fl6.flowi6_proto = IPPROTO_TCP;
-	if (ipv6_addr_type(&fl6.daddr) & IPV6_ADDR_LINKLOCAL)
+	if (rt6_need_strict(&fl6.daddr) || !oif)
 		fl6.flowi6_oif = inet6_iif(skb);
+	else
+		fl6.flowi6_oif = oif;
 	fl6.fl6_dport = t1->dest;
 	fl6.fl6_sport = t1->source;
 	security_skb_classify_flow(skb, flowi6_to_flowi(&fl6));
···
 	int genhash;
 	struct sock *sk1 = NULL;
 #endif
+	int oif;
 
 	if (th->rst)
 		return;
···
 		ack_seq = ntohl(th->seq) + th->syn + th->fin + skb->len -
 			  (th->doff << 2);
 
-	tcp_v6_send_response(skb, seq, ack_seq, 0, 0, 0, key, 1, 0, 0);
+	oif = sk ? sk->sk_bound_dev_if : 0;
+	tcp_v6_send_response(skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
 
 #ifdef CONFIG_TCP_MD5SIG
 release_sk1:
···
 }
 
 static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
-			    u32 win, u32 tsval, u32 tsecr,
+			    u32 win, u32 tsval, u32 tsecr, int oif,
 			    struct tcp_md5sig_key *key, u8 tclass,
 			    u32 label)
 {
-	tcp_v6_send_response(skb, seq, ack, win, tsval, tsecr, key, 0, tclass,
+	tcp_v6_send_response(skb, seq, ack, win, tsval, tsecr, oif, key, 0, tclass,
 			     label);
 }
 
···
 	tcp_v6_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
 			tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
 			tcp_time_stamp + tcptw->tw_ts_offset,
-			tcptw->tw_ts_recent, tcp_twsk_md5_key(tcptw),
+			tcptw->tw_ts_recent, tw->tw_bound_dev_if, tcp_twsk_md5_key(tcptw),
 			tw->tw_tclass, (tw->tw_flowlabel << 12));
 
 	inet_twsk_put(tw);
···
 				  struct request_sock *req)
 {
 	tcp_v6_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1,
-			req->rcv_wnd, tcp_time_stamp, req->ts_recent,
+			req->rcv_wnd, tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
 			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
 			0, 0);
 }