ipv4: Use cork flow in ip_queue_xmit()

All invokers of ip_queue_xmit() must make certain that the
socket is locked. All of SCTP, TCP, DCCP, and L2TP now make
sure this is the case.

Therefore we can use the cork flow during output route lookup in
ip_queue_xmit() when the socket route check fails.

Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ip_output.c

···
 	struct sock *sk = skb->sk;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ip_options_rcu *inet_opt;
+	struct flowi4 *fl4;
 	struct rtable *rt;
 	struct iphdr *iph;
 	int res;
···
 		goto packet_routed;
 
 	/* Make sure we can route this packet. */
+	fl4 = &inet->cork.fl.u.ip4;
 	rt = (struct rtable *)__sk_dst_check(sk, 0);
 	if (rt == NULL) {
-		struct flowi4 fl4;
 		__be32 daddr;
 
 		/* Use correct destination address if we have options. */
···
 		 * keep trying until route appears or the connection times
 		 * itself out.
 		 */
-		rt = ip_route_output_ports(sock_net(sk), &fl4, sk,
+		rt = ip_route_output_ports(sock_net(sk), fl4, sk,
 					   daddr, inet->inet_saddr,
 					   inet->inet_dport,
 					   inet->inet_sport,