tcp: remove rtx_syn_ack field

Now inet_rtx_syn_ack() is only used by TCP, it can directly
call tcp_rtx_synack() instead of using an indirect call
to req->rsk_ops->rtx_syn_ack().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250626153017.2156274-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

include/net/request_sock.h

@@ -30,8 +30,6 @@ struct request_sock_ops {
 	unsigned int	obj_size;
 	struct kmem_cache	*slab;
 	char		*slab_name;
-	int		(*rtx_syn_ack)(const struct sock *sk,
-				       struct request_sock *req);
 	void		(*send_ack)(const struct sock *sk, struct sk_buff *skb,
 				    struct request_sock *req);
 	void		(*send_reset)(const struct sock *sk,

net/ipv4/inet_connection_sock.c

@@ -886,7 +886,7 @@ static void syn_ack_recalc(struct request_sock *req,
 
 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)
 {
-	int err = req->rsk_ops->rtx_syn_ack(parent, req);
+	int err = tcp_rtx_synack(parent, req);
 
 	if (!err)
 		req->num_retrans++;

net/ipv4/tcp_ipv4.c

@@ -1703,7 +1703,6 @@ static struct dst_entry *tcp_v4_route_req(const struct sock *sk,
 struct request_sock_ops tcp_request_sock_ops __read_mostly = {
 	.family		=	PF_INET,
 	.obj_size	=	sizeof(struct tcp_request_sock),
-	.rtx_syn_ack	=	tcp_rtx_synack,
 	.send_ack	=	tcp_v4_reqsk_send_ack,
 	.destructor	=	tcp_v4_reqsk_destructor,
 	.send_reset	=	tcp_v4_send_reset,

net/ipv6/tcp_ipv6.c

@@ -835,7 +835,6 @@ static struct dst_entry *tcp_v6_route_req(const struct sock *sk,
 struct request_sock_ops tcp6_request_sock_ops __read_mostly = {
 	.family		=	AF_INET6,
 	.obj_size	=	sizeof(struct tcp6_request_sock),
-	.rtx_syn_ack	=	tcp_rtx_synack,
 	.send_ack	=	tcp_v6_reqsk_send_ack,
 	.destructor	=	tcp_v6_reqsk_destructor,
 	.send_reset	=	tcp_v6_send_reset,