kernel/include/net/inet_connection_sock.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * NET		Generic infrastructure for INET connection oriented protocols.
 *
 *		Definitions for inet_connection_sock 
 *
 * Authors:	Many people, see the TCP sources
 *
 * 		From code originally in TCP
 */
#ifndef _INET_CONNECTION_SOCK_H
#define _INET_CONNECTION_SOCK_H

#include <linux/compiler.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/poll.h>
#include <linux/kernel.h>
#include <linux/sockptr.h>

#include <net/inet_sock.h>
#include <net/request_sock.h>

/* Cancel timers, when they are not required. */
#undef INET_CSK_CLEAR_TIMERS

struct inet_bind_bucket;
struct inet_bind2_bucket;
struct tcp_congestion_ops;

/*
 * Pointers to address related TCP functions
 * (i.e. things that depend on the address family)
 */
struct inet_connection_sock_af_ops {
	int	    (*queue_xmit)(struct sock *sk, struct sk_buff *skb, struct flowi *fl);
	void	    (*send_check)(struct sock *sk, struct sk_buff *skb);
	int	    (*rebuild_header)(struct sock *sk);
	void	    (*sk_rx_dst_set)(struct sock *sk, const struct sk_buff *skb);
	int	    (*conn_request)(struct sock *sk, struct sk_buff *skb);
	struct sock *(*syn_recv_sock)(const struct sock *sk, struct sk_buff *skb,
				      struct request_sock *req,
				      struct dst_entry *dst,
				      struct request_sock *req_unhash,
				      bool *own_req);
	u16	    net_header_len;
	int	    (*setsockopt)(struct sock *sk, int level, int optname,
				  sockptr_t optval, unsigned int optlen);
	int	    (*getsockopt)(struct sock *sk, int level, int optname,
				  char __user *optval, int __user *optlen);
	void	    (*mtu_reduced)(struct sock *sk);
};

/** inet_connection_sock - INET connection oriented sock
 *
 * @icsk_accept_queue:	   FIFO of established children
 * @icsk_bind_hash:	   Bind node
 * @icsk_bind2_hash:	   Bind node in the bhash2 table
 * @icsk_retransmit_timer: Resend (no ack)
 * @icsk_rto:		   Retransmit timeout
 * @icsk_pmtu_cookie	   Last pmtu seen by socket
 * @icsk_ca_ops		   Pluggable congestion control hook
 * @icsk_af_ops		   Operations which are AF_INET{4,6} specific
 * @icsk_ulp_ops	   Pluggable ULP control hook
 * @icsk_ulp_data	   ULP private data
 * @icsk_ca_state:	   Congestion control state
 * @icsk_retransmits:	   Number of unrecovered [RTO] timeouts
 * @icsk_pending:	   Scheduled timer event
 * @icsk_backoff:	   Backoff
 * @icsk_syn_retries:      Number of allowed SYN (or equivalent) retries
 * @icsk_probes_out:	   unanswered 0 window probes
 * @icsk_ext_hdr_len:	   Network protocol overhead (IP/IPv6 options)
 * @icsk_ack:		   Delayed ACK control data
 * @icsk_mtup;		   MTU probing control data
 * @icsk_probes_tstamp:    Probe timestamp (cleared by non-zero window ack)
 * @icsk_user_timeout:	   TCP_USER_TIMEOUT value
 */
struct inet_connection_sock {
	/* inet_sock has to be the first member! */
	struct inet_sock	  icsk_inet;
	struct request_sock_queue icsk_accept_queue;
	struct inet_bind_bucket	  *icsk_bind_hash;
	struct inet_bind2_bucket  *icsk_bind2_hash;
 	struct timer_list	  icsk_retransmit_timer;
 	struct timer_list	  icsk_delack_timer;
	__u32			  icsk_rto;
	__u32                     icsk_rto_min;
	u32			  icsk_rto_max;
	__u32                     icsk_delack_max;
	__u32			  icsk_pmtu_cookie;
	const struct tcp_congestion_ops *icsk_ca_ops;
	const struct inet_connection_sock_af_ops *icsk_af_ops;
	const struct tcp_ulp_ops  *icsk_ulp_ops;
	void __rcu		  *icsk_ulp_data;
	unsigned int		  (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
	__u8			  icsk_ca_state:5,
				  icsk_ca_initialized:1,
				  icsk_ca_setsockopt:1,
				  icsk_ca_dst_locked:1;
	__u8			  icsk_retransmits;
	__u8			  icsk_pending;
	__u8			  icsk_backoff;
	__u8			  icsk_syn_retries;
	__u8			  icsk_probes_out;
	__u16			  icsk_ext_hdr_len;
	struct {
		__u8		  pending;	 /* ACK is pending			   */
		__u8		  quick;	 /* Scheduled number of quick acks	   */
		__u8		  pingpong;	 /* The session is interactive		   */
		__u8		  retry;	 /* Number of attempts			   */
		#define ATO_BITS 8
		__u32		  ato:ATO_BITS,	 /* Predicted tick of soft clock	   */
				  lrcv_flowlabel:20, /* last received ipv6 flowlabel	   */
				  dst_quick_ack:1, /* cache dst RTAX_QUICKACK		   */
				  unused:3;
		__u32		  lrcvtime;	 /* timestamp of last received data packet */
		__u16		  last_seg_size; /* Size of last incoming segment	   */
		__u16		  rcv_mss;	 /* MSS used for delayed ACK decisions	   */
	} icsk_ack;
	struct {
		/* Range of MTUs to search */
		int		  search_high;
		int		  search_low;

		/* Information on the current probe. */
		u32		  probe_size:31,
		/* Is the MTUP feature enabled for this connection? */
				  enabled:1;

		u32		  probe_timestamp;
	} icsk_mtup;
	u32			  icsk_probes_tstamp;
	u32			  icsk_user_timeout;

	u64			  icsk_ca_priv[104 / sizeof(u64)];
#define ICSK_CA_PRIV_SIZE	  sizeof_field(struct inet_connection_sock, icsk_ca_priv)
};

#define ICSK_TIME_RETRANS	1	/* Retransmit timer */
#define ICSK_TIME_DACK		2	/* Delayed ack timer */
#define ICSK_TIME_PROBE0	3	/* Zero window probe timer */
#define ICSK_TIME_LOSS_PROBE	5	/* Tail loss probe timer */
#define ICSK_TIME_REO_TIMEOUT	6	/* Reordering timer */

#define inet_csk(ptr) container_of_const(ptr, struct inet_connection_sock, icsk_inet.sk)

static inline void *inet_csk_ca(const struct sock *sk)
{
	return (void *)inet_csk(sk)->icsk_ca_priv;
}

struct sock *inet_csk_clone_lock(const struct sock *sk,
				 const struct request_sock *req,
				 const gfp_t priority);

enum inet_csk_ack_state_t {
	ICSK_ACK_SCHED	= 1,
	ICSK_ACK_TIMER  = 2,
	ICSK_ACK_PUSHED = 4,
	ICSK_ACK_PUSHED2 = 8,
	ICSK_ACK_NOW = 16,	/* Send the next ACK immediately (once) */
	ICSK_ACK_NOMEM = 32,
};

void inet_csk_init_xmit_timers(struct sock *sk,
			       void (*retransmit_handler)(struct timer_list *),
			       void (*delack_handler)(struct timer_list *),
			       void (*keepalive_handler)(struct timer_list *));
void inet_csk_clear_xmit_timers(struct sock *sk);
void inet_csk_clear_xmit_timers_sync(struct sock *sk);

static inline void inet_csk_schedule_ack(struct sock *sk)
{
	inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_SCHED;
}

static inline int inet_csk_ack_scheduled(const struct sock *sk)
{
	return inet_csk(sk)->icsk_ack.pending & ICSK_ACK_SCHED;
}

static inline void inet_csk_delack_init(struct sock *sk)
{
	memset(&inet_csk(sk)->icsk_ack, 0, sizeof(inet_csk(sk)->icsk_ack));
}

static inline unsigned long
icsk_timeout(const struct inet_connection_sock *icsk)
{
	return READ_ONCE(icsk->icsk_retransmit_timer.expires);
}

static inline unsigned long
icsk_delack_timeout(const struct inet_connection_sock *icsk)
{
	return READ_ONCE(icsk->icsk_delack_timer.expires);
}

static inline void inet_csk_clear_xmit_timer(struct sock *sk, const int what)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (what == ICSK_TIME_RETRANS || what == ICSK_TIME_PROBE0) {
		smp_store_release(&icsk->icsk_pending, 0);
#ifdef INET_CSK_CLEAR_TIMERS
		sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
#endif
	} else if (what == ICSK_TIME_DACK) {
		smp_store_release(&icsk->icsk_ack.pending, 0);
		icsk->icsk_ack.retry = 0;
#ifdef INET_CSK_CLEAR_TIMERS
		sk_stop_timer(sk, &icsk->icsk_delack_timer);
#endif
	} else {
		pr_debug("inet_csk BUG: unknown timer value\n");
	}
}

/*
 *	Reset the retransmission timer
 */
static inline void inet_csk_reset_xmit_timer(struct sock *sk, const int what,
					     unsigned long when,
					     const unsigned long max_when)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (when > max_when) {
		pr_debug("reset_xmit_timer: sk=%p %d when=0x%lx, caller=%p\n",
			 sk, what, when, (void *)_THIS_IP_);
		when = max_when;
	}

	when += jiffies;
	if (what == ICSK_TIME_RETRANS || what == ICSK_TIME_PROBE0 ||
	    what == ICSK_TIME_LOSS_PROBE || what == ICSK_TIME_REO_TIMEOUT) {
		smp_store_release(&icsk->icsk_pending, what);
		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, when);
	} else if (what == ICSK_TIME_DACK) {
		smp_store_release(&icsk->icsk_ack.pending,
				  icsk->icsk_ack.pending | ICSK_ACK_TIMER);
		sk_reset_timer(sk, &icsk->icsk_delack_timer, when);
	} else {
		pr_debug("inet_csk BUG: unknown timer value\n");
	}
}

static inline unsigned long
inet_csk_rto_backoff(const struct inet_connection_sock *icsk,
		     unsigned long max_when)
{
        u64 when = (u64)icsk->icsk_rto << icsk->icsk_backoff;

        return (unsigned long)min_t(u64, when, max_when);
}

struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg);

int inet_csk_get_port(struct sock *sk, unsigned short snum);

struct dst_entry *inet_csk_route_req(const struct sock *sk, struct flowi4 *fl4,
				     const struct request_sock *req);
struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
					    struct sock *newsk,
					    const struct request_sock *req);

struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
				      struct request_sock *req,
				      struct sock *child);
bool inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
				   unsigned long timeout);
struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
					 struct request_sock *req,
					 bool own_req);

static inline void inet_csk_reqsk_queue_added(struct sock *sk)
{
	reqsk_queue_added(&inet_csk(sk)->icsk_accept_queue);
}

static inline int inet_csk_reqsk_queue_len(const struct sock *sk)
{
	return reqsk_queue_len(&inet_csk(sk)->icsk_accept_queue);
}

static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk)
{
	return inet_csk_reqsk_queue_len(sk) > READ_ONCE(sk->sk_max_ack_backlog);
}

bool inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req);
void inet_csk_reqsk_queue_drop_and_put(struct sock *sk, struct request_sock *req);

static inline unsigned long
reqsk_timeout(struct request_sock *req, unsigned long max_timeout)
{
	u64 timeout = (u64)req->timeout << req->num_timeout;

	return (unsigned long)min_t(u64, timeout, max_timeout);
}

static inline void inet_csk_prepare_for_destroy_sock(struct sock *sk)
{
	/* The below has to be done to allow calling inet_csk_destroy_sock */
	sock_set_flag(sk, SOCK_DEAD);
	this_cpu_inc(*sk->sk_prot->orphan_count);
}

void inet_csk_destroy_sock(struct sock *sk);
void inet_csk_prepare_forced_close(struct sock *sk);

/*
 * LISTEN is a special case for poll..
 */
static inline __poll_t inet_csk_listen_poll(const struct sock *sk)
{
	return !reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue) ?
			(EPOLLIN | EPOLLRDNORM) : 0;
}

int inet_csk_listen_start(struct sock *sk);
void inet_csk_listen_stop(struct sock *sk);

/* update the fast reuse flag when adding a socket */
void inet_csk_update_fastreuse(struct inet_bind_bucket *tb,
			       struct sock *sk);

struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu);

static inline void inet_csk_enter_pingpong_mode(struct sock *sk)
{
	inet_csk(sk)->icsk_ack.pingpong =
		READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pingpong_thresh);
}

static inline void inet_csk_exit_pingpong_mode(struct sock *sk)
{
	inet_csk(sk)->icsk_ack.pingpong = 0;
}

static inline bool inet_csk_in_pingpong_mode(struct sock *sk)
{
	return inet_csk(sk)->icsk_ack.pingpong >=
	       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pingpong_thresh);
}

static inline void inet_csk_inc_pingpong_cnt(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (icsk->icsk_ack.pingpong < U8_MAX)
		icsk->icsk_ack.pingpong++;
}

static inline bool inet_csk_has_ulp(const struct sock *sk)
{
	return inet_test_bit(IS_ICSK, sk) && !!inet_csk(sk)->icsk_ulp_ops;
}

static inline void inet_init_csk_locks(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	spin_lock_init(&icsk->icsk_accept_queue.rskq_lock);
	spin_lock_init(&icsk->icsk_accept_queue.fastopenq.lock);
}

#endif /* _INET_CONNECTION_SOCK_H */