/* SPDX-License-Identifier: GPL-2.0-or-later */

#ifndef _REQUEST_SOCK_H
#define _REQUEST_SOCK_H

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/refcount.h>

#include <net/sock.h>
#include <net/rstreason.h>

struct request_sock;
struct sk_buff;
struct dst_entry;
struct proto;

struct request_sock_ops {
	int		family;
	unsigned int	obj_size;
	struct kmem_cache	*slab;
	char		*slab_name;
	void		(*send_ack)(const struct sock *sk, struct sk_buff *skb,
				    struct request_sock *req);
	void		(*send_reset)(const struct sock *sk,
				      struct sk_buff *skb,
				      enum sk_rst_reason reason);
	void		(*destructor)(struct request_sock *req);
};

struct saved_syn {
	u32 mac_hdrlen;
	u32 network_hdrlen;
	u32 tcp_hdrlen;
	u8 data[];
};


struct request_sock {
	struct sock_common		__req_common;
#define rsk_refcnt			__req_common.skc_refcnt
#define rsk_hash			__req_common.skc_hash
#define rsk_listener			__req_common.skc_listener
#define rsk_window_clamp		__req_common.skc_window_clamp
#define rsk_rcv_wnd			__req_common.skc_rcv_wnd

	struct request_sock		*dl_next;
	u16				mss;
	u8				num_retrans; 
	u8				syncookie:1; 
	u8				num_timeout:7; 
	u32				ts_recent;
	struct timer_list		rsk_timer;
	const struct request_sock_ops	*rsk_ops;
	struct sock			*sk;
	struct saved_syn		*saved_syn;
	u32				secid;
	u32				peer_secid;
	u32				timeout;
};

static inline struct request_sock *inet_reqsk(const struct sock *sk)
{
	return (struct request_sock *)sk;
}

static inline struct sock *req_to_sk(struct request_sock *req)
{
	return (struct sock *)req;
}


static inline struct sock *skb_steal_sock(struct sk_buff *skb,
					  bool *refcounted, bool *prefetched)
{
	struct sock *sk = skb->sk;

	if (!sk) {
		*prefetched = false;
		*refcounted = false;
		return NULL;
	}

	*prefetched = skb_sk_is_prefetched(skb);
	if (*prefetched) {
#if IS_ENABLED(CONFIG_SYN_COOKIES)
		if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) {
			struct request_sock *req = inet_reqsk(sk);

			*refcounted = false;
			sk = req->rsk_listener;
			req->rsk_listener = NULL;
			return sk;
		}
#endif
		*refcounted = sk_is_refcounted(sk);
	} else {
		*refcounted = true;
	}

	skb->destructor = NULL;
	skb->sk = NULL;
	return sk;
}

void __reqsk_free(struct request_sock *req);

static inline void reqsk_free(struct request_sock *req)
{
	DEBUG_NET_WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
	__reqsk_free(req);
}

static inline void reqsk_put(struct request_sock *req)
{
	if (refcount_dec_and_test(&req->rsk_refcnt))
		__reqsk_free(req);
}


struct fastopen_queue {
	struct request_sock	*rskq_rst_head; 
	struct request_sock	*rskq_rst_tail; 
	spinlock_t	lock;
	int		qlen;		
	int		max_qlen;	

	struct tcp_fastopen_context __rcu *ctx; 
};


struct request_sock_queue {
	spinlock_t		rskq_lock;
	u8			rskq_defer_accept;
	u8			synflood_warned;

	atomic_t		qlen;
	atomic_t		young;

	struct request_sock	*rskq_accept_head;
	struct request_sock	*rskq_accept_tail;
	struct fastopen_queue	fastopenq;  
};

void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
			   bool reset);

static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
{
	return READ_ONCE(queue->rskq_accept_head) == NULL;
}

static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
						      struct sock *parent)
{
	struct request_sock *req;

	spin_lock_bh(&queue->rskq_lock);
	req = queue->rskq_accept_head;
	if (req) {
		sk_acceptq_removed(parent);
		WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
		if (queue->rskq_accept_head == NULL)
			queue->rskq_accept_tail = NULL;
	}
	spin_unlock_bh(&queue->rskq_lock);
	return req;
}

static inline void reqsk_queue_removed(struct request_sock_queue *queue,
				       const struct request_sock *req)
{
	if (req->num_timeout == 0)
		atomic_dec(&queue->young);
	atomic_dec(&queue->qlen);
}

static inline void reqsk_queue_added(struct request_sock_queue *queue)
{
	atomic_inc(&queue->young);
	atomic_inc(&queue->qlen);
}

static inline int reqsk_queue_len(const struct request_sock_queue *queue)
{
	return atomic_read(&queue->qlen);
}

static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
{
	return atomic_read(&queue->young);
}


static inline u32 tcp_synack_window(const struct request_sock *req)
{
	return min(req->rsk_rcv_wnd, 65535U);
}
#endif 
