inet: makes syn_ack_timeout mandatory

There are two struct request_sock_ops providers, tcp and dccp.

inet_csk_reqsk_queue_prune() can avoid testing syn_ack_timeout being
NULL if we make it non NULL like syn_ack_timeout

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Cc: dccp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/dccp.h

@@ -549,6 +549,8 @@ static inline const char *dccp_role(const struct sock *sk)
 	return NULL;
 }
 
+extern void dccp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
+
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_DCCP_H */

net/dccp/ipv4.c

@@ -574,6 +574,11 @@ static void dccp_v4_reqsk_destructor(struct request_sock *req)
 	kfree(inet_rsk(req)->opt);
 }
 
+void dccp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
+{
+}
+EXPORT_SYMBOL(dccp_syn_ack_timeout);
+
 static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 	.family		= PF_INET,
 	.obj_size	= sizeof(struct dccp_request_sock),
@@ -581,6 +586,7 @@ static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
 	.send_ack	= dccp_reqsk_send_ack,
 	.destructor	= dccp_v4_reqsk_destructor,
 	.send_reset	= dccp_v4_ctl_send_reset,
+	.syn_ack_timeout = dccp_syn_ack_timeout,
 };
 
 int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)

net/dccp/ipv6.c

@@ -343,6 +343,7 @@ static struct request_sock_ops dccp6_request_sock_ops = {
 	.send_ack	= dccp_reqsk_send_ack,
 	.destructor	= dccp_v6_reqsk_destructor,
 	.send_reset	= dccp_v6_ctl_send_reset,
+	.syn_ack_timeout = dccp_syn_ack_timeout,
 };
 
 static struct sock *dccp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)

net/ipv4/inet_connection_sock.c

@@ -555,8 +555,7 @@ void inet_csk_reqsk_queue_prune(struct sock *parent,
 				syn_ack_recalc(req, thresh, max_retries,
 					       queue->rskq_defer_accept,
 					       &expire, &resend);
-				if (req->rsk_ops->syn_ack_timeout)
-					req->rsk_ops->syn_ack_timeout(parent, req);
+				req->rsk_ops->syn_ack_timeout(parent, req);
 				if (!expire &&
 				    (!resend ||
 				     !req->rsk_ops->rtx_syn_ack(parent, req, NULL) ||