inet: factor out inet_send_prepare()

The same code is replicated verbatim in multiple places, and the next
patches will introduce an additional user for it. Factor out a
helper and use it where appropriate. No functional change intended.

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

include/net/inet_common.h

···
 		       int addr_len, int flags);
 int inet_accept(struct socket *sock, struct socket *newsock, int flags,
 		bool kern);
+int inet_send_prepare(struct sock *sk);
 int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size);
 ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
 		      size_t size, int flags);

net/ipv4/af_inet.c

···
 }
 EXPORT_SYMBOL(inet_getname);
 
-int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
+int inet_send_prepare(struct sock *sk)
 {
-	struct sock *sk = sock->sk;
-
 	sock_rps_record_flow(sk);
 
 	/* We may need to bind the socket. */
 	if (!inet_sk(sk)->inet_num && !sk->sk_prot->no_autobind &&
 	    inet_autobind(sk))
+		return -EAGAIN;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(inet_send_prepare);
+
+int inet_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
+{
+	struct sock *sk = sock->sk;
+
+	if (unlikely(inet_send_prepare(sk)))
 		return -EAGAIN;
 
 	return sk->sk_prot->sendmsg(sk, msg, size);
···
 {
 	struct sock *sk = sock->sk;
 
-	sock_rps_record_flow(sk);
-
-	/* We may need to bind the socket. */
-	if (!inet_sk(sk)->inet_num && !sk->sk_prot->no_autobind &&
-	    inet_autobind(sk))
+	if (unlikely(inet_send_prepare(sk)))
 		return -EAGAIN;
 
 	if (sk->sk_prot->sendpage)