tcp: pass fl6 to inet6_csk_route_req()

This commit changes inet_csk_route_req() so that it uses a pointer to
a struct flowi6, rather than allocating its own on the stack. This
brings its behavior in line with its IPv4 cousin,
inet_csk_route_req(), and allows a follow-on patch to fix a dst leak.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index fc0b96b..4e5fa5f 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -477,7 +477,8 @@
 }
 
 
-static int tcp_v6_send_synack(struct sock *sk, struct request_sock *req,
+static int tcp_v6_send_synack(struct sock *sk,
+			      struct request_sock *req,
 			      struct request_values *rvp,
 			      u16 queue_mapping)
 {
@@ -1058,6 +1059,7 @@
 	struct tcp_sock *tp = tcp_sk(sk);
 	__u32 isn = TCP_SKB_CB(skb)->when;
 	struct dst_entry *dst = NULL;
+	struct flowi6 fl6;
 	bool want_cookie = false;
 
 	if (skb->protocol == htons(ETH_P_IP))
@@ -1177,7 +1179,7 @@
 		 */
 		if (tmp_opt.saw_tstamp &&
 		    tcp_death_row.sysctl_tw_recycle &&
-		    (dst = inet6_csk_route_req(sk, req)) != NULL &&
+		    (dst = inet6_csk_route_req(sk, &fl6, req)) != NULL &&
 		    (peer = rt6_get_peer((struct rt6_info *)dst)) != NULL &&
 		    ipv6_addr_equal((struct in6_addr *)peer->daddr.addr.a6,
 				    &treq->rmt_addr)) {
@@ -1247,6 +1249,7 @@
 #ifdef CONFIG_TCP_MD5SIG
 	struct tcp_md5sig_key *key;
 #endif
+	struct flowi6 fl6;
 
 	if (skb->protocol == htons(ETH_P_IP)) {
 		/*
@@ -1309,7 +1312,7 @@
 		goto out_overflow;
 
 	if (!dst) {
-		dst = inet6_csk_route_req(sk, req);
+		dst = inet6_csk_route_req(sk, &fl6, req);
 		if (!dst)
 			goto out;
 	}