Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2217 insertions, 0 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
new file mode 100644
index 000000000..5c5807ed6
--- /dev/null
+++ b/include/net/tcp.h
@@ -0,0 +1,2217 @@
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Definitions for the TCP module.
+ *
+ * Version:	@(#)tcp.h	1.0.5	05/23/93
+ *
+ * Authors:	Ross Biro
+ *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ */
+#ifndef _TCP_H
+#define _TCP_H
+
+#define FASTRETRANS_DEBUG 1
+
+#include <linux/list.h>
+#include <linux/tcp.h>
+#include <linux/bug.h>
+#include <linux/slab.h>
+#include <linux/cache.h>
+#include <linux/percpu.h>
+#include <linux/skbuff.h>
+#include <linux/cryptohash.h>
+#include <linux/kref.h>
+#include <linux/ktime.h>
+
+#include <net/inet_connection_sock.h>
+#include <net/inet_timewait_sock.h>
+#include <net/inet_hashtables.h>
+#include <net/checksum.h>
+#include <net/request_sock.h>
+#include <net/sock_reuseport.h>
+#include <net/sock.h>
+#include <net/snmp.h>
+#include <net/ip.h>
+#include <net/tcp_states.h>
+#include <net/inet_ecn.h>
+#include <net/dst.h>
+
+#include <linux/seq_file.h>
+#include <linux/memcontrol.h>
+#include <linux/bpf-cgroup.h>
+
+extern struct inet_hashinfo tcp_hashinfo;
+
+extern struct percpu_counter tcp_orphan_count;
+void tcp_time_wait(struct sock *sk, int state, int timeo);
+
+#define MAX_TCP_HEADER	L1_CACHE_ALIGN(128 + MAX_HEADER)
+#define MAX_TCP_OPTION_SPACE 40
+#define TCP_MIN_SND_MSS		48
+#define TCP_MIN_GSO_SIZE	(TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
+
+/*
+ * Never offer a window over 32767 without using window scaling. Some
+ * poor stacks do signed 16bit maths!
+ */
+#define MAX_TCP_WINDOW		32767U
+
+/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
+#define TCP_MIN_MSS		88U
+
+/* The least MTU to use for probing */
+#define TCP_BASE_MSS		1024
+
+/* probing interval, default to 10 minutes as per RFC4821 */
+#define TCP_PROBE_INTERVAL	600
+
+/* Specify interval when tcp mtu probing will stop */
+#define TCP_PROBE_THRESHOLD	8
+
+/* After receiving this amount of duplicate ACKs fast retransmit starts. */
+#define TCP_FASTRETRANS_THRESH 3
+
+/* Maximal number of ACKs sent quickly to accelerate slow-start. */
+#define TCP_MAX_QUICKACKS	16U
+
+/* Maximal number of window scale according to RFC1323 */
+#define TCP_MAX_WSCALE		14U
+
+/* urg_data states */
+#define TCP_URG_VALID	0x0100
+#define TCP_URG_NOTYET	0x0200
+#define TCP_URG_READ	0x0400
+
+#define TCP_RETR1	3	/*
+				 * This is how many retries it does before it
+				 * tries to figure out if the gateway is
+				 * down. Minimal RFC value is 3; it corresponds
+				 * to ~3sec-8min depending on RTO.
+				 */
+
+#define TCP_RETR2	15	/*
+				 * This should take at least
+				 * 90 minutes to time out.
+				 * RFC1122 says that the limit is 100 sec.
+				 * 15 is ~13-30min depending on RTO.
+				 */
+
+#define TCP_SYN_RETRIES	 6	/* This is how many retries are done
+				 * when active opening a connection.
+				 * RFC1122 says the minimum retry MUST
+				 * be at least 180secs.  Nevertheless
+				 * this value is corresponding to
+				 * 63secs of retransmission with the
+				 * current initial RTO.
+				 */
+
+#define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
+				 * when passive opening a connection.
+				 * This is corresponding to 31secs of
+				 * retransmission with the current
+				 * initial RTO.
+				 */
+
+#define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
+				  * state, about 60 seconds	*/
+#define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
+                                 /* BSD style FIN_WAIT2 deadlock breaker.
+				  * It used to be 3min, new value is 60sec,
+				  * to combine FIN-WAIT-2 timeout with
+				  * TIME-WAIT timer.
+				  */
+
+#define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
+#if HZ >= 100
+#define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
+#define TCP_ATO_MIN	((unsigned)(HZ/25))
+#else
+#define TCP_DELACK_MIN	4U
+#define TCP_ATO_MIN	4U
+#endif
+#define TCP_RTO_MAX	((unsigned)(120*HZ))
+#define TCP_RTO_MIN	((unsigned)(HZ/5))
+#define TCP_TIMEOUT_MIN	(2U) /* Min timeout for TCP timers in jiffies */
+#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
+#define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
+						 * used as a fallback RTO for the
+						 * initial data transmission if no
+						 * valid RTT sample has been acquired,
+						 * most likely due to retrans in 3WHS.
+						 */
+
+#define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
+					                 * for local resources.
+					                 */
+#define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
+#define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
+#define TCP_KEEPALIVE_INTVL	(75*HZ)
+
+#define MAX_TCP_KEEPIDLE	32767
+#define MAX_TCP_KEEPINTVL	32767
+#define MAX_TCP_KEEPCNT		127
+#define MAX_TCP_SYNCNT		127
+
+#define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
+
+#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
+#define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
+					 * after this time. It should be equal
+					 * (or greater than) TCP_TIMEWAIT_LEN
+					 * to provide reliability equal to one
+					 * provided by timewait state.
+					 */
+#define TCP_PAWS_WINDOW	1		/* Replay window for per-host
+					 * timestamps. It must be less than
+					 * minimal timewait lifetime.
+					 */
+/*
+ *	TCP option
+ */
+
+#define TCPOPT_NOP		1	/* Padding */
+#define TCPOPT_EOL		0	/* End of options */
+#define TCPOPT_MSS		2	/* Segment size negotiating */
+#define TCPOPT_WINDOW		3	/* Window scaling */
+#define TCPOPT_SACK_PERM        4       /* SACK Permitted */
+#define TCPOPT_SACK             5       /* SACK Block */
+#define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
+#define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
+#define TCPOPT_FASTOPEN		34	/* Fast open (RFC7413) */
+#define TCPOPT_EXP		254	/* Experimental */
+/* Magic number to be after the option value for sharing TCP
+ * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
+ */
+#define TCPOPT_FASTOPEN_MAGIC	0xF989
+#define TCPOPT_SMC_MAGIC	0xE2D4C3D9
+
+/*
+ *     TCP option lengths
+ */
+
+#define TCPOLEN_MSS            4
+#define TCPOLEN_WINDOW         3
+#define TCPOLEN_SACK_PERM      2
+#define TCPOLEN_TIMESTAMP      10
+#define TCPOLEN_MD5SIG         18
+#define TCPOLEN_FASTOPEN_BASE  2
+#define TCPOLEN_EXP_FASTOPEN_BASE  4
+#define TCPOLEN_EXP_SMC_BASE   6
+
+/* But this is what stacks really send out. */
+#define TCPOLEN_TSTAMP_ALIGNED		12
+#define TCPOLEN_WSCALE_ALIGNED		4
+#define TCPOLEN_SACKPERM_ALIGNED	4
+#define TCPOLEN_SACK_BASE		2
+#define TCPOLEN_SACK_BASE_ALIGNED	4
+#define TCPOLEN_SACK_PERBLOCK		8
+#define TCPOLEN_MD5SIG_ALIGNED		20
+#define TCPOLEN_MSS_ALIGNED		4
+#define TCPOLEN_EXP_SMC_BASE_ALIGNED	8
+
+/* Flags in tp->nonagle */
+#define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
+#define TCP_NAGLE_CORK		2	/* Socket is corked	    */
+#define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
+
+/* TCP thin-stream limits */
+#define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
+
+/* TCP initial congestion window as per rfc6928 */
+#define TCP_INIT_CWND		10
+
+/* Bit Flags for sysctl_tcp_fastopen */
+#define	TFO_CLIENT_ENABLE	1
+#define	TFO_SERVER_ENABLE	2
+#define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
+
+/* Accept SYN data w/o any cookie option */
+#define	TFO_SERVER_COOKIE_NOT_REQD	0x200
+
+/* Force enable TFO on all listeners, i.e., not requiring the
+ * TCP_FASTOPEN socket option.
+ */
+#define	TFO_SERVER_WO_SOCKOPT1	0x400
+
+
+/* sysctl variables for tcp */
+extern int sysctl_tcp_max_orphans;
+extern long sysctl_tcp_mem[3];
+
+#define TCP_RACK_LOSS_DETECTION  0x1 /* Use RACK to detect losses */
+#define TCP_RACK_STATIC_REO_WND  0x2 /* Use static RACK reo wnd */
+#define TCP_RACK_NO_DUPTHRESH    0x4 /* Do not use DUPACK threshold in RACK */
+
+extern atomic_long_t tcp_memory_allocated;
+extern struct percpu_counter tcp_sockets_allocated;
+extern unsigned long tcp_memory_pressure;
+
+/* optimized version of sk_under_memory_pressure() for TCP sockets */
+static inline bool tcp_under_memory_pressure(const struct sock *sk)
+{
+	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
+	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
+		return true;
+
+	return READ_ONCE(tcp_memory_pressure);
+}
+/*
+ * The next routines deal with comparing 32 bit unsigned ints
+ * and worry about wraparound (automatic with unsigned arithmetic).
+ */
+
+static inline bool before(__u32 seq1, __u32 seq2)
+{
+        return (__s32)(seq1-seq2) < 0;
+}
+#define after(seq2, seq1) 	before(seq1, seq2)
+
+/* is s2<=s1<=s3 ? */
+static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
+{
+	return seq3 - seq2 >= seq1 - seq2;
+}
+
+static inline bool tcp_out_of_memory(struct sock *sk)
+{
+	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
+	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
+		return true;
+	return false;
+}
+
+void sk_forced_mem_schedule(struct sock *sk, int size);
+
+static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
+{
+	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
+	int orphans = percpu_counter_read_positive(ocp);
+
+	if (orphans << shift > sysctl_tcp_max_orphans) {
+		orphans = percpu_counter_sum_positive(ocp);
+		if (orphans << shift > sysctl_tcp_max_orphans)
+			return true;
+	}
+	return false;
+}
+
+bool tcp_check_oom(struct sock *sk, int shift);
+
+
+extern struct proto tcp_prot;
+
+#define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
+#define __TCP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.tcp_statistics, field)
+#define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
+#define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
+
+void tcp_tasklet_init(void);
+
+void tcp_v4_err(struct sk_buff *skb, u32);
+
+void tcp_shutdown(struct sock *sk, int how);
+
+int tcp_v4_early_demux(struct sk_buff *skb);
+int tcp_v4_rcv(struct sk_buff *skb);
+
+int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
+int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
+int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
+int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
+		 int flags);
+int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
+			size_t size, int flags);
+ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
+		 size_t size, int flags);
+void tcp_release_cb(struct sock *sk);
+void tcp_wfree(struct sk_buff *skb);
+void tcp_write_timer_handler(struct sock *sk);
+void tcp_delack_timer_handler(struct sock *sk);
+int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
+int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
+void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
+void tcp_rcv_space_adjust(struct sock *sk);
+int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
+void tcp_twsk_destructor(struct sock *sk);
+ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
+			struct pipe_inode_info *pipe, size_t len,
+			unsigned int flags);
+
+void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks);
+static inline void tcp_dec_quickack_mode(struct sock *sk,
+					 const unsigned int pkts)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (icsk->icsk_ack.quick) {
+		if (pkts >= icsk->icsk_ack.quick) {
+			icsk->icsk_ack.quick = 0;
+			/* Leaving quickack mode we deflate ATO. */
+			icsk->icsk_ack.ato   = TCP_ATO_MIN;
+		} else
+			icsk->icsk_ack.quick -= pkts;
+	}
+}
+
+#define	TCP_ECN_OK		1
+#define	TCP_ECN_QUEUE_CWR	2
+#define	TCP_ECN_DEMAND_CWR	4
+#define	TCP_ECN_SEEN		8
+
+enum tcp_tw_status {
+	TCP_TW_SUCCESS = 0,
+	TCP_TW_RST = 1,
+	TCP_TW_ACK = 2,
+	TCP_TW_SYN = 3
+};
+
+
+enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
+					      struct sk_buff *skb,
+					      const struct tcphdr *th);
+struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
+			   struct request_sock *req, bool fastopen,
+			   bool *lost_race);
+int tcp_child_process(struct sock *parent, struct sock *child,
+		      struct sk_buff *skb);
+void tcp_enter_loss(struct sock *sk);
+void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag);
+void tcp_clear_retrans(struct tcp_sock *tp);
+void tcp_update_metrics(struct sock *sk);
+void tcp_init_metrics(struct sock *sk);
+void tcp_metrics_init(void);
+bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
+void tcp_close(struct sock *sk, long timeout);
+void tcp_init_sock(struct sock *sk);
+void tcp_init_transfer(struct sock *sk, int bpf_op);
+__poll_t tcp_poll(struct file *file, struct socket *sock,
+		      struct poll_table_struct *wait);
+int tcp_getsockopt(struct sock *sk, int level, int optname,
+		   char __user *optval, int __user *optlen);
+int tcp_setsockopt(struct sock *sk, int level, int optname,
+		   char __user *optval, unsigned int optlen);
+int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
+			  char __user *optval, int __user *optlen);
+int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
+			  char __user *optval, unsigned int optlen);
+void tcp_set_keepalive(struct sock *sk, int val);
+void tcp_syn_ack_timeout(const struct request_sock *req);
+int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
+		int flags, int *addr_len);
+int tcp_set_rcvlowat(struct sock *sk, int val);
+void tcp_data_ready(struct sock *sk);
+int tcp_mmap(struct file *file, struct socket *sock,
+	     struct vm_area_struct *vma);
+void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
+		       struct tcp_options_received *opt_rx,
+		       int estab, struct tcp_fastopen_cookie *foc);
+const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
+
+/*
+ *	TCP v4 functions exported for the inet6 API
+ */
+
+void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
+void tcp_v4_mtu_reduced(struct sock *sk);
+void tcp_req_err(struct sock *sk, u32 seq, bool abort);
+int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
+struct sock *tcp_create_openreq_child(const struct sock *sk,
+				      struct request_sock *req,
+				      struct sk_buff *skb);
+void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
+struct sock *tcp_v4_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);
+int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
+int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
+int tcp_connect(struct sock *sk);
+enum tcp_synack_type {
+	TCP_SYNACK_NORMAL,
+	TCP_SYNACK_FASTOPEN,
+	TCP_SYNACK_COOKIE,
+};
+struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
+				struct request_sock *req,
+				struct tcp_fastopen_cookie *foc,
+				enum tcp_synack_type synack_type);
+int tcp_disconnect(struct sock *sk, int flags);
+
+void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
+int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
+void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
+
+/* From syncookies.c */
+struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
+				 struct request_sock *req,
+				 struct dst_entry *dst, u32 tsoff);
+int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
+		      u32 cookie);
+struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
+#ifdef CONFIG_SYN_COOKIES
+
+/* Syncookies use a monotonic timer which increments every 60 seconds.
+ * This counter is used both as a hash input and partially encoded into
+ * the cookie value.  A cookie is only validated further if the delta
+ * between the current counter value and the encoded one is less than this,
+ * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
+ * the counter advances immediately after a cookie is generated).
+ */
+#define MAX_SYNCOOKIE_AGE	2
+#define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
+#define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
+
+/* syncookies: remember time of last synqueue overflow
+ * But do not dirty this field too often (once per second is enough)
+ * It is racy as we do not hold a lock, but race is very minor.
+ */
+static inline void tcp_synq_overflow(const struct sock *sk)
+{
+	unsigned int last_overflow;
+	unsigned int now = jiffies;
+
+	if (sk->sk_reuseport) {
+		struct sock_reuseport *reuse;
+
+		reuse = rcu_dereference(sk->sk_reuseport_cb);
+		if (likely(reuse)) {
+			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
+			if (!time_between32(now, last_overflow,
+					    last_overflow + HZ))
+				WRITE_ONCE(reuse->synq_overflow_ts, now);
+			return;
+		}
+	}
+
+	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
+	if (!time_between32(now, last_overflow, last_overflow + HZ))
+		WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now);
+}
+
+/* syncookies: no recent synqueue overflow on this listening socket? */
+static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
+{
+	unsigned int last_overflow;
+	unsigned int now = jiffies;
+
+	if (sk->sk_reuseport) {
+		struct sock_reuseport *reuse;
+
+		reuse = rcu_dereference(sk->sk_reuseport_cb);
+		if (likely(reuse)) {
+			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
+			return !time_between32(now, last_overflow - HZ,
+					       last_overflow +
+					       TCP_SYNCOOKIE_VALID);
+		}
+	}
+
+	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
+
+	/* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID,
+	 * then we're under synflood. However, we have to use
+	 * 'last_overflow - HZ' as lower bound. That's because a concurrent
+	 * tcp_synq_overflow() could update .ts_recent_stamp after we read
+	 * jiffies but before we store .ts_recent_stamp into last_overflow,
+	 * which could lead to rejecting a valid syncookie.
+	 */
+	return !time_between32(now, last_overflow - HZ,
+			       last_overflow + TCP_SYNCOOKIE_VALID);
+}
+
+static inline u32 tcp_cookie_time(void)
+{
+	u64 val = get_jiffies_64();
+
+	do_div(val, TCP_SYNCOOKIE_PERIOD);
+	return val;
+}
+
+u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
+			      u16 *mssp);
+__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
+u64 cookie_init_timestamp(struct request_sock *req);
+bool cookie_timestamp_decode(const struct net *net,
+			     struct tcp_options_received *opt);
+bool cookie_ecn_ok(const struct tcp_options_received *opt,
+		   const struct net *net, const struct dst_entry *dst);
+
+/* From net/ipv6/syncookies.c */
+int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
+		      u32 cookie);
+struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
+
+u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
+			      const struct tcphdr *th, u16 *mssp);
+__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
+#endif
+/* tcp_output.c */
+
+void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
+			       int nonagle);
+int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
+int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
+void tcp_retransmit_timer(struct sock *sk);
+void tcp_xmit_retransmit_queue(struct sock *);
+void tcp_simple_retransmit(struct sock *);
+void tcp_enter_recovery(struct sock *sk, bool ece_ack);
+int tcp_trim_head(struct sock *, struct sk_buff *, u32);
+enum tcp_queue {
+	TCP_FRAG_IN_WRITE_QUEUE,
+	TCP_FRAG_IN_RTX_QUEUE,
+};
+int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+		 struct sk_buff *skb, u32 len,
+		 unsigned int mss_now, gfp_t gfp);
+
+void tcp_send_probe0(struct sock *);
+void tcp_send_partial(struct sock *);
+int tcp_write_wakeup(struct sock *, int mib);
+void tcp_send_fin(struct sock *sk);
+void tcp_send_active_reset(struct sock *sk, gfp_t priority);
+int tcp_send_synack(struct sock *);
+void tcp_push_one(struct sock *, unsigned int mss_now);
+void __tcp_send_ack(struct sock *sk, u32 rcv_nxt);
+void tcp_send_ack(struct sock *sk);
+void tcp_send_delayed_ack(struct sock *sk);
+void tcp_send_loss_probe(struct sock *sk);
+bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto);
+void tcp_skb_collapse_tstamp(struct sk_buff *skb,
+			     const struct sk_buff *next_skb);
+
+/* tcp_input.c */
+void tcp_rearm_rto(struct sock *sk);
+void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
+void tcp_reset(struct sock *sk);
+void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
+void tcp_fin(struct sock *sk);
+void tcp_check_space(struct sock *sk);
+
+/* tcp_timer.c */
+void tcp_init_xmit_timers(struct sock *);
+static inline void tcp_clear_xmit_timers(struct sock *sk)
+{
+	if (hrtimer_try_to_cancel(&tcp_sk(sk)->pacing_timer) == 1)
+		__sock_put(sk);
+
+	if (hrtimer_try_to_cancel(&tcp_sk(sk)->compressed_ack_timer) == 1)
+		__sock_put(sk);
+
+	inet_csk_clear_xmit_timers(sk);
+}
+
+unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
+unsigned int tcp_current_mss(struct sock *sk);
+
+/* Bound MSS / TSO packet size with the half of the window */
+static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
+{
+	int cutoff;
+
+	/* When peer uses tiny windows, there is no use in packetizing
+	 * to sub-MSS pieces for the sake of SWS or making sure there
+	 * are enough packets in the pipe for fast recovery.
+	 *
+	 * On the other hand, for extremely large MSS devices, handling
+	 * smaller than MSS windows in this way does make sense.
+	 */
+	if (tp->max_window > TCP_MSS_DEFAULT)
+		cutoff = (tp->max_window >> 1);
+	else
+		cutoff = tp->max_window;
+
+	if (cutoff && pktsize > cutoff)
+		return max_t(int, cutoff, 68U - tp->tcp_header_len);
+	else
+		return pktsize;
+}
+
+/* tcp.c */
+void tcp_get_info(struct sock *, struct tcp_info *);
+
+/* Read 'sendfile()'-style from a TCP socket */
+int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+		  sk_read_actor_t recv_actor);
+
+void tcp_initialize_rcv_mss(struct sock *sk);
+
+int tcp_mtu_to_mss(struct sock *sk, int pmtu);
+int tcp_mss_to_mtu(struct sock *sk, int mss);
+void tcp_mtup_init(struct sock *sk);
+void tcp_init_buffer_space(struct sock *sk);
+
+static inline void tcp_bound_rto(const struct sock *sk)
+{
+	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
+		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
+}
+
+static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
+{
+	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
+}
+
+static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
+{
+	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
+			       ntohl(TCP_FLAG_ACK) |
+			       snd_wnd);
+}
+
+static inline void tcp_fast_path_on(struct tcp_sock *tp)
+{
+	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
+}
+
+static inline void tcp_fast_path_check(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
+	    tp->rcv_wnd &&
+	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
+	    !tp->urg_data)
+		tcp_fast_path_on(tp);
+}
+
+/* Compute the actual rto_min value */
+static inline u32 tcp_rto_min(struct sock *sk)
+{
+	const struct dst_entry *dst = __sk_dst_get(sk);
+	u32 rto_min = TCP_RTO_MIN;
+
+	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
+		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
+	return rto_min;
+}
+
+static inline u32 tcp_rto_min_us(struct sock *sk)
+{
+	return jiffies_to_usecs(tcp_rto_min(sk));
+}
+
+static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
+{
+	return dst_metric_locked(dst, RTAX_CC_ALGO);
+}
+
+/* Minimum RTT in usec. ~0 means not available. */
+static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
+{
+	return minmax_get(&tp->rtt_min);
+}
+
+/* Compute the actual receive window we are currently advertising.
+ * Rcv_nxt can be after the window if our peer push more data
+ * than the offered window.
+ */
+static inline u32 tcp_receive_window(const struct tcp_sock *tp)
+{
+	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
+
+	if (win < 0)
+		win = 0;
+	return (u32) win;
+}
+
+/* Choose a new window, without checks for shrinking, and without
+ * scaling applied to the result.  The caller does these things
+ * if necessary.  This is a "raw" window selection.
+ */
+u32 __tcp_select_window(struct sock *sk);
+
+void tcp_send_window_probe(struct sock *sk);
+
+/* TCP uses 32bit jiffies to save some space.
+ * Note that this is different from tcp_time_stamp, which
+ * historically has been the same until linux-4.13.
+ */
+#define tcp_jiffies32 ((u32)jiffies)
+
+/*
+ * Deliver a 32bit value for TCP timestamp option (RFC 7323)
+ * It is no longer tied to jiffies, but to 1 ms clock.
+ * Note: double check if you want to use tcp_jiffies32 instead of this.
+ */
+#define TCP_TS_HZ	1000
+
+static inline u64 tcp_clock_ns(void)
+{
+	return local_clock();
+}
+
+static inline u64 tcp_clock_us(void)
+{
+	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
+}
+
+/* This should only be used in contexts where tp->tcp_mstamp is up to date */
+static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
+{
+	return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
+}
+
+/* Could use tcp_clock_us() / 1000, but this version uses a single divide */
+static inline u32 tcp_time_stamp_raw(void)
+{
+	return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
+}
+
+
+/* Refresh 1us clock of a TCP socket,
+ * ensuring monotically increasing values.
+ */
+static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
+{
+	u64 val = tcp_clock_us();
+
+	if (val > tp->tcp_mstamp)
+		tp->tcp_mstamp = val;
+}
+
+static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
+{
+	return max_t(s64, t1 - t0, 0);
+}
+
+static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
+{
+	return div_u64(skb->skb_mstamp, USEC_PER_SEC / TCP_TS_HZ);
+}
+
+
+#define tcp_flag_byte(th) (((u_int8_t *)th)[13])
+
+#define TCPHDR_FIN 0x01
+#define TCPHDR_SYN 0x02
+#define TCPHDR_RST 0x04
+#define TCPHDR_PSH 0x08
+#define TCPHDR_ACK 0x10
+#define TCPHDR_URG 0x20
+#define TCPHDR_ECE 0x40
+#define TCPHDR_CWR 0x80
+
+#define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
+
+/* This is what the send packet queuing engine uses to pass
+ * TCP per-packet control information to the transmission code.
+ * We also store the host-order sequence numbers in here too.
+ * This is 44 bytes if IPV6 is enabled.
+ * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
+ */
+struct tcp_skb_cb {
+	__u32		seq;		/* Starting sequence number	*/
+	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
+	union {
+		/* Note : tcp_tw_isn is used in input path only
+		 *	  (isn chosen by tcp_timewait_state_process())
+		 *
+		 * 	  tcp_gso_segs/size are used in write queue only,
+		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
+		 */
+		__u32		tcp_tw_isn;
+		struct {
+			u16	tcp_gso_segs;
+			u16	tcp_gso_size;
+		};
+	};
+	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
+
+	__u8		sacked;		/* State flags for SACK.	*/
+#define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
+#define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
+#define TCPCB_LOST		0x04	/* SKB is lost			*/
+#define TCPCB_TAGBITS		0x07	/* All tag bits			*/
+#define TCPCB_REPAIRED		0x10	/* SKB repaired (no skb_mstamp)	*/
+#define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
+#define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
+				TCPCB_REPAIRED)
+
+	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
+	__u8		txstamp_ack:1,	/* Record TX timestamp for ack? */
+			eor:1,		/* Is skb MSG_EOR marked? */
+			has_rxtstamp:1,	/* SKB has a RX timestamp	*/
+			unused:5;
+	__u32		ack_seq;	/* Sequence number ACK'd	*/
+	union {
+		struct {
+			/* There is space for up to 24 bytes */
+			__u32 in_flight:30,/* Bytes in flight at transmit */
+			      is_app_limited:1, /* cwnd not fully used? */
+			      unused:1;
+			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
+			__u32 delivered;
+			/* start of send pipeline phase */
+			u64 first_tx_mstamp;
+			/* when we reached the "delivered" count */
+			u64 delivered_mstamp;
+		} tx;   /* only used for outgoing skbs */
+		union {
+			struct inet_skb_parm	h4;
+#if IS_ENABLED(CONFIG_IPV6)
+			struct inet6_skb_parm	h6;
+#endif
+		} header;	/* For incoming skbs */
+		struct {
+			__u32 flags;
+			struct sock *sk_redir;
+			void *data_end;
+		} bpf;
+	};
+};
+
+#define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
+
+static inline void bpf_compute_data_end_sk_skb(struct sk_buff *skb)
+{
+	TCP_SKB_CB(skb)->bpf.data_end = skb->data + skb_headlen(skb);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/* This is the variant of inet6_iif() that must be used by TCP,
+ * as TCP moves IP6CB into a different location in skb->cb[]
+ */
+static inline int tcp_v6_iif(const struct sk_buff *skb)
+{
+	return TCP_SKB_CB(skb)->header.h6.iif;
+}
+
+static inline int tcp_v6_iif_l3_slave(const struct sk_buff *skb)
+{
+	bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
+
+	return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
+}
+
+/* TCP_SKB_CB reference means this can not be used from early demux */
+static inline int tcp_v6_sdif(const struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+	if (skb && ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags))
+		return TCP_SKB_CB(skb)->header.h6.iif;
+#endif
+	return 0;
+}
+#endif
+
+static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+	if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
+	    skb && ipv4_l3mdev_skb(IPCB(skb)->flags))
+		return true;
+#endif
+	return false;
+}
+
+/* TCP_SKB_CB reference means this can not be used from early demux */
+static inline int tcp_v4_sdif(struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+	if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
+		return TCP_SKB_CB(skb)->header.h4.iif;
+#endif
+	return 0;
+}
+
+/* Due to TSO, an SKB can be composed of multiple actual
+ * packets.  To keep these tracked properly, we use this.
+ */
+static inline int tcp_skb_pcount(const struct sk_buff *skb)
+{
+	return TCP_SKB_CB(skb)->tcp_gso_segs;
+}
+
+static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
+{
+	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
+}
+
+static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
+{
+	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
+}
+
+/* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
+static inline int tcp_skb_mss(const struct sk_buff *skb)
+{
+	return TCP_SKB_CB(skb)->tcp_gso_size;
+}
+
+static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
+{
+	return likely(!TCP_SKB_CB(skb)->eor);
+}
+
+/* Events passed to congestion control interface */
+enum tcp_ca_event {
+	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
+	CA_EVENT_CWND_RESTART,	/* congestion window restart */
+	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
+	CA_EVENT_LOSS,		/* loss timeout */
+	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
+	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
+};
+
+/* Information about inbound ACK, passed to cong_ops->in_ack_event() */
+enum tcp_ca_ack_event_flags {
+	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
+	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
+	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
+};
+
+/*
+ * Interface for adding new TCP congestion control handlers
+ */
+#define TCP_CA_NAME_MAX	16
+#define TCP_CA_MAX	128
+#define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
+
+#define TCP_CA_UNSPEC	0
+
+/* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
+#define TCP_CONG_NON_RESTRICTED 0x1
+/* Requires ECN/ECT set on all packets */
+#define TCP_CONG_NEEDS_ECN	0x2
+
+union tcp_cc_info;
+
+struct ack_sample {
+	u32 pkts_acked;
+	s32 rtt_us;
+	u32 in_flight;
+};
+
+/* A rate sample measures the number of (original/retransmitted) data
+ * packets delivered "delivered" over an interval of time "interval_us".
+ * The tcp_rate.c code fills in the rate sample, and congestion
+ * control modules that define a cong_control function to run at the end
+ * of ACK processing can optionally chose to consult this sample when
+ * setting cwnd and pacing rate.
+ * A sample is invalid if "delivered" or "interval_us" is negative.
+ */
+struct rate_sample {
+	u64  prior_mstamp; /* starting timestamp for interval */
+	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
+	s32  delivered;		/* number of packets delivered over interval */
+	long interval_us;	/* time for tp->delivered to incr "delivered" */
+	u32 snd_interval_us;	/* snd interval for delivered packets */
+	u32 rcv_interval_us;	/* rcv interval for delivered packets */
+	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
+	int  losses;		/* number of packets marked lost upon ACK */
+	u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
+	u32  prior_in_flight;	/* in flight before this ACK */
+	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
+	bool is_retrans;	/* is sample from retransmission? */
+	bool is_ack_delayed;	/* is this (likely) a delayed ACK? */
+};
+
+struct tcp_congestion_ops {
+	struct list_head	list;
+	u32 key;
+	u32 flags;
+
+	/* initialize private data (optional) */
+	void (*init)(struct sock *sk);
+	/* cleanup private data  (optional) */
+	void (*release)(struct sock *sk);
+
+	/* return slow start threshold (required) */
+	u32 (*ssthresh)(struct sock *sk);
+	/* do new cwnd calculation (required) */
+	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
+	/* call before changing ca_state (optional) */
+	void (*set_state)(struct sock *sk, u8 new_state);
+	/* call when cwnd event occurs (optional) */
+	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
+	/* call when ack arrives (optional) */
+	void (*in_ack_event)(struct sock *sk, u32 flags);
+	/* new value of cwnd after loss (required) */
+	u32  (*undo_cwnd)(struct sock *sk);
+	/* hook for packet ack accounting (optional) */
+	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
+	/* override sysctl_tcp_min_tso_segs */
+	u32 (*min_tso_segs)(struct sock *sk);
+	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
+	u32 (*sndbuf_expand)(struct sock *sk);
+	/* call when packets are delivered to update cwnd and pacing rate,
+	 * after all the ca_state processing. (optional)
+	 */
+	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
+	/* get info for inet_diag (optional) */
+	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
+			   union tcp_cc_info *info);
+
+	char 		name[TCP_CA_NAME_MAX];
+	struct module 	*owner;
+};
+
+int tcp_register_congestion_control(struct tcp_congestion_ops *type);
+void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
+
+void tcp_assign_congestion_control(struct sock *sk);
+void tcp_init_congestion_control(struct sock *sk);
+void tcp_cleanup_congestion_control(struct sock *sk);
+int tcp_set_default_congestion_control(struct net *net, const char *name);
+void tcp_get_default_congestion_control(struct net *net, char *name);
+void tcp_get_available_congestion_control(char *buf, size_t len);
+void tcp_get_allowed_congestion_control(char *buf, size_t len);
+int tcp_set_allowed_congestion_control(char *allowed);
+int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
+			       bool reinit, bool cap_net_admin);
+u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
+void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
+
+u32 tcp_reno_ssthresh(struct sock *sk);
+u32 tcp_reno_undo_cwnd(struct sock *sk);
+void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
+extern struct tcp_congestion_ops tcp_reno;
+
+struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
+u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca);
+#ifdef CONFIG_INET
+char *tcp_ca_get_name_by_key(u32 key, char *buffer);
+#else
+static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
+{
+	return NULL;
+}
+#endif
+
+static inline bool tcp_ca_needs_ecn(const struct sock *sk)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
+}
+
+static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (icsk->icsk_ca_ops->set_state)
+		icsk->icsk_ca_ops->set_state(sk, ca_state);
+	icsk->icsk_ca_state = ca_state;
+}
+
+static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (icsk->icsk_ca_ops->cwnd_event)
+		icsk->icsk_ca_ops->cwnd_event(sk, event);
+}
+
+/* From tcp_rate.c */
+void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
+void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
+			    struct rate_sample *rs);
+void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
+		  bool is_sack_reneg, struct rate_sample *rs);
+void tcp_rate_check_app_limited(struct sock *sk);
+
+/* These functions determine how the current flow behaves in respect of SACK
+ * handling. SACK is negotiated with the peer, and therefore it can vary
+ * between different flows.
+ *
+ * tcp_is_sack - SACK enabled
+ * tcp_is_reno - No SACK
+ */
+static inline int tcp_is_sack(const struct tcp_sock *tp)
+{
+	return tp->rx_opt.sack_ok;
+}
+
+static inline bool tcp_is_reno(const struct tcp_sock *tp)
+{
+	return !tcp_is_sack(tp);
+}
+
+static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
+{
+	return tp->sacked_out + tp->lost_out;
+}
+
+/* This determines how many packets are "in the network" to the best
+ * of our knowledge.  In many cases it is conservative, but where
+ * detailed information is available from the receiver (via SACK
+ * blocks etc.) we can make more aggressive calculations.
+ *
+ * Use this for decisions involving congestion control, use just
+ * tp->packets_out to determine if the send queue is empty or not.
+ *
+ * Read this equation as:
+ *
+ *	"Packets sent once on transmission queue" MINUS
+ *	"Packets left network, but not honestly ACKed yet" PLUS
+ *	"Packets fast retransmitted"
+ */
+static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
+{
+	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
+}
+
+#define TCP_INFINITE_SSTHRESH	0x7fffffff
+
+static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
+{
+	return tp->snd_cwnd < tp->snd_ssthresh;
+}
+
+static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
+{
+	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
+}
+
+static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
+{
+	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
+	       (1 << inet_csk(sk)->icsk_ca_state);
+}
+
+/* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
+ * The exception is cwnd reduction phase, when cwnd is decreasing towards
+ * ssthresh.
+ */
+static inline __u32 tcp_current_ssthresh(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+
+	if (tcp_in_cwnd_reduction(sk))
+		return tp->snd_ssthresh;
+	else
+		return max(tp->snd_ssthresh,
+			   ((tp->snd_cwnd >> 1) +
+			    (tp->snd_cwnd >> 2)));
+}
+
+/* Use define here intentionally to get WARN_ON location shown at the caller */
+#define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
+
+void tcp_enter_cwr(struct sock *sk);
+__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
+
+/* The maximum number of MSS of available cwnd for which TSO defers
+ * sending if not using sysctl_tcp_tso_win_divisor.
+ */
+static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
+{
+	return 3;
+}
+
+/* Returns end sequence number of the receiver's advertised window */
+static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
+{
+	return tp->snd_una + tp->snd_wnd;
+}
+
+/* We follow the spirit of RFC2861 to validate cwnd but implement a more
+ * flexible approach. The RFC suggests cwnd should not be raised unless
+ * it was fully used previously. And that's exactly what we do in
+ * congestion avoidance mode. But in slow start we allow cwnd to grow
+ * as long as the application has used half the cwnd.
+ * Example :
+ *    cwnd is 10 (IW10), but application sends 9 frames.
+ *    We allow cwnd to reach 18 when all frames are ACKed.
+ * This check is safe because it's as aggressive as slow start which already
+ * risks 100% overshoot. The advantage is that we discourage application to
+ * either send more filler packets or data to artificially blow up the cwnd
+ * usage, and allow application-limited process to probe bw more aggressively.
+ */
+static inline bool tcp_is_cwnd_limited(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+
+	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
+	if (tcp_in_slow_start(tp))
+		return tp->snd_cwnd < 2 * tp->max_packets_out;
+
+	return tp->is_cwnd_limited;
+}
+
+/* BBR congestion control needs pacing.
+ * Same remark for SO_MAX_PACING_RATE.
+ * sch_fq packet scheduler is efficiently handling pacing,
+ * but is not always installed/used.
+ * Return true if TCP stack should pace packets itself.
+ */
+static inline bool tcp_needs_internal_pacing(const struct sock *sk)
+{
+	return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED;
+}
+
+/* Something is really bad, we could not queue an additional packet,
+ * because qdisc is full or receiver sent a 0 window.
+ * We do not want to add fuel to the fire, or abort too early,
+ * so make sure the timer we arm now is at least 200ms in the future,
+ * regardless of current icsk_rto value (as it could be ~2ms)
+ */
+static inline unsigned long tcp_probe0_base(const struct sock *sk)
+{
+	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
+}
+
+/* Variant of inet_csk_rto_backoff() used for zero window probes */
+static inline unsigned long tcp_probe0_when(const struct sock *sk,
+					    unsigned long max_when)
+{
+	u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
+
+	return (unsigned long)min_t(u64, when, max_when);
+}
+
+static inline void tcp_check_probe_timer(struct sock *sk)
+{
+	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
+		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
+					  tcp_probe0_base(sk), TCP_RTO_MAX);
+}
+
+static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
+{
+	tp->snd_wl1 = seq;
+}
+
+static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
+{
+	tp->snd_wl1 = seq;
+}
+
+/*
+ * Calculate(/check) TCP checksum
+ */
+static inline __sum16 tcp_v4_check(int len, __be32 saddr,
+				   __be32 daddr, __wsum base)
+{
+	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
+}
+
+static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
+{
+	return __skb_checksum_complete(skb);
+}
+
+static inline bool tcp_checksum_complete(struct sk_buff *skb)
+{
+	return !skb_csum_unnecessary(skb) &&
+		__tcp_checksum_complete(skb);
+}
+
+bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
+int tcp_filter(struct sock *sk, struct sk_buff *skb);
+
+#undef STATE_TRACE
+
+#ifdef STATE_TRACE
+static const char *statename[]={
+	"Unused","Established","Syn Sent","Syn Recv",
+	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
+	"Close Wait","Last ACK","Listen","Closing"
+};
+#endif
+void tcp_set_state(struct sock *sk, int state);
+
+void tcp_done(struct sock *sk);
+
+int tcp_abort(struct sock *sk, int err);
+
+static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
+{
+	rx_opt->dsack = 0;
+	rx_opt->num_sacks = 0;
+}
+
+u32 tcp_default_init_rwnd(u32 mss);
+void tcp_cwnd_restart(struct sock *sk, s32 delta);
+
+static inline void tcp_slow_start_after_idle_check(struct sock *sk)
+{
+	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
+	struct tcp_sock *tp = tcp_sk(sk);
+	s32 delta;
+
+	if (!sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle || tp->packets_out ||
+	    ca_ops->cong_control)
+		return;
+	delta = tcp_jiffies32 - tp->lsndtime;
+	if (delta > inet_csk(sk)->icsk_rto)
+		tcp_cwnd_restart(sk, delta);
+}
+
+/* Determine a window scaling and initial window to offer. */
+void tcp_select_initial_window(const struct sock *sk, int __space,
+			       __u32 mss, __u32 *rcv_wnd,
+			       __u32 *window_clamp, int wscale_ok,
+			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
+
+static inline int tcp_win_from_space(const struct sock *sk, int space)
+{
+	int tcp_adv_win_scale = sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale;
+
+	return tcp_adv_win_scale <= 0 ?
+		(space>>(-tcp_adv_win_scale)) :
+		space - (space>>tcp_adv_win_scale);
+}
+
+/* Note: caller must be prepared to deal with negative returns */
+static inline int tcp_space(const struct sock *sk)
+{
+	return tcp_win_from_space(sk, sk->sk_rcvbuf - sk->sk_backlog.len -
+				  atomic_read(&sk->sk_rmem_alloc));
+}
+
+static inline int tcp_full_space(const struct sock *sk)
+{
+	return tcp_win_from_space(sk, sk->sk_rcvbuf);
+}
+
+/* We provision sk_rcvbuf around 200% of sk_rcvlowat.
+ * If 87.5 % (7/8) of the space has been consumed, we want to override
+ * SO_RCVLOWAT constraint, since we are receiving skbs with too small
+ * len/truesize ratio.
+ */
+static inline bool tcp_rmem_pressure(const struct sock *sk)
+{
+	int rcvbuf, threshold;
+
+	if (tcp_under_memory_pressure(sk))
+		return true;
+
+	rcvbuf = READ_ONCE(sk->sk_rcvbuf);
+	threshold = rcvbuf - (rcvbuf >> 3);
+
+	return atomic_read(&sk->sk_rmem_alloc) > threshold;
+}
+
+extern void tcp_openreq_init_rwin(struct request_sock *req,
+				  const struct sock *sk_listener,
+				  const struct dst_entry *dst);
+
+void tcp_enter_memory_pressure(struct sock *sk);
+void tcp_leave_memory_pressure(struct sock *sk);
+
+static inline int keepalive_intvl_when(const struct tcp_sock *tp)
+{
+	struct net *net = sock_net((struct sock *)tp);
+
+	return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
+}
+
+static inline int keepalive_time_when(const struct tcp_sock *tp)
+{
+	struct net *net = sock_net((struct sock *)tp);
+
+	return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
+}
+
+static inline int keepalive_probes(const struct tcp_sock *tp)
+{
+	struct net *net = sock_net((struct sock *)tp);
+
+	return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
+}
+
+static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
+{
+	const struct inet_connection_sock *icsk = &tp->inet_conn;
+
+	return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
+			  tcp_jiffies32 - tp->rcv_tstamp);
+}
+
+static inline int tcp_fin_time(const struct sock *sk)
+{
+	int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
+	const int rto = inet_csk(sk)->icsk_rto;
+
+	if (fin_timeout < (rto << 2) - (rto >> 1))
+		fin_timeout = (rto << 2) - (rto >> 1);
+
+	return fin_timeout;
+}
+
+static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
+				  int paws_win)
+{
+	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
+		return true;
+	if (unlikely(!time_before32(ktime_get_seconds(),
+				    rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)))
+		return true;
+	/*
+	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
+	 * then following tcp messages have valid values. Ignore 0 value,
+	 * or else 'negative' tsval might forbid us to accept their packets.
+	 */
+	if (!rx_opt->ts_recent)
+		return true;
+	return false;
+}
+
+static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
+				   int rst)
+{
+	if (tcp_paws_check(rx_opt, 0))
+		return false;
+
+	/* RST segments are not recommended to carry timestamp,
+	   and, if they do, it is recommended to ignore PAWS because
+	   "their cleanup function should take precedence over timestamps."
+	   Certainly, it is mistake. It is necessary to understand the reasons
+	   of this constraint to relax it: if peer reboots, clock may go
+	   out-of-sync and half-open connections will not be reset.
+	   Actually, the problem would be not existing if all
+	   the implementations followed draft about maintaining clock
+	   via reboots. Linux-2.2 DOES NOT!
+
+	   However, we can relax time bounds for RST segments to MSL.
+	 */
+	if (rst && !time_before32(ktime_get_seconds(),
+				  rx_opt->ts_recent_stamp + TCP_PAWS_MSL))
+		return false;
+	return true;
+}
+
+bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
+			  int mib_idx, u32 *last_oow_ack_time);
+
+static inline void tcp_mib_init(struct net *net)
+{
+	/* See RFC 2012 */
+	TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
+	TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
+	TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
+	TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
+}
+
+/* from STCP */
+static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
+{
+	tp->lost_skb_hint = NULL;
+}
+
+static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
+{
+	tcp_clear_retrans_hints_partial(tp);
+	tp->retransmit_skb_hint = NULL;
+}
+
+union tcp_md5_addr {
+	struct in_addr  a4;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct in6_addr	a6;
+#endif
+};
+
+/* - key database */
+struct tcp_md5sig_key {
+	struct hlist_node	node;
+	u8			keylen;
+	u8			family; /* AF_INET or AF_INET6 */
+	union tcp_md5_addr	addr;
+	u8			prefixlen;
+	u8			key[TCP_MD5SIG_MAXKEYLEN];
+	struct rcu_head		rcu;
+};
+
+/* - sock block */
+struct tcp_md5sig_info {
+	struct hlist_head	head;
+	struct rcu_head		rcu;
+};
+
+/* - pseudo header */
+struct tcp4_pseudohdr {
+	__be32		saddr;
+	__be32		daddr;
+	__u8		pad;
+	__u8		protocol;
+	__be16		len;
+};
+
+struct tcp6_pseudohdr {
+	struct in6_addr	saddr;
+	struct in6_addr daddr;
+	__be32		len;
+	__be32		protocol;	/* including padding */
+};
+
+union tcp_md5sum_block {
+	struct tcp4_pseudohdr ip4;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct tcp6_pseudohdr ip6;
+#endif
+};
+
+/* - pool: digest algorithm, hash description and scratch buffer */
+struct tcp_md5sig_pool {
+	struct ahash_request	*md5_req;
+	void			*scratch;
+};
+
+/* - functions */
+int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
+			const struct sock *sk, const struct sk_buff *skb);
+int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
+		   int family, u8 prefixlen, const u8 *newkey, u8 newkeylen,
+		   gfp_t gfp);
+int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
+		   int family, u8 prefixlen);
+struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
+					 const struct sock *addr_sk);
+
+#ifdef CONFIG_TCP_MD5SIG
+struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
+					 const union tcp_md5_addr *addr,
+					 int family);
+#define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
+#else
+static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
+					 const union tcp_md5_addr *addr,
+					 int family)
+{
+	return NULL;
+}
+#define tcp_twsk_md5_key(twsk)	NULL
+#endif
+
+bool tcp_alloc_md5sig_pool(void);
+
+struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
+static inline void tcp_put_md5sig_pool(void)
+{
+	local_bh_enable();
+}
+
+int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
+			  unsigned int header_len);
+int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
+		     const struct tcp_md5sig_key *key);
+
+/* From tcp_fastopen.c */
+void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
+			    struct tcp_fastopen_cookie *cookie);
+void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
+			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
+			    u16 try_exp);
+struct tcp_fastopen_request {
+	/* Fast Open cookie. Size 0 means a cookie request */
+	struct tcp_fastopen_cookie	cookie;
+	struct msghdr			*data;  /* data in MSG_FASTOPEN */
+	size_t				size;
+	int				copied;	/* queued in tcp_connect() */
+};
+void tcp_free_fastopen_req(struct tcp_sock *tp);
+void tcp_fastopen_destroy_cipher(struct sock *sk);
+void tcp_fastopen_ctx_destroy(struct net *net);
+int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
+			      void *key, unsigned int len);
+void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
+struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
+			      struct request_sock *req,
+			      struct tcp_fastopen_cookie *foc,
+			      const struct dst_entry *dst);
+void tcp_fastopen_init_key_once(struct net *net);
+bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
+			     struct tcp_fastopen_cookie *cookie);
+bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
+#define TCP_FASTOPEN_KEY_LENGTH 16
+
+/* Fastopen key context */
+struct tcp_fastopen_context {
+	struct crypto_cipher	*tfm;
+	__u8			key[TCP_FASTOPEN_KEY_LENGTH];
+	struct rcu_head		rcu;
+};
+
+extern unsigned int sysctl_tcp_fastopen_blackhole_timeout;
+void tcp_fastopen_active_disable(struct sock *sk);
+bool tcp_fastopen_active_should_disable(struct sock *sk);
+void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
+void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired);
+
+/* Latencies incurred by various limits for a sender. They are
+ * chronograph-like stats that are mutually exclusive.
+ */
+enum tcp_chrono {
+	TCP_CHRONO_UNSPEC,
+	TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
+	TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
+	TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
+	__TCP_CHRONO_MAX,
+};
+
+void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
+void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
+
+/* This helper is needed, because skb->tcp_tsorted_anchor uses
+ * the same memory storage than skb->destructor/_skb_refdst
+ */
+static inline void tcp_skb_tsorted_anchor_cleanup(struct sk_buff *skb)
+{
+	skb->destructor = NULL;
+	skb->_skb_refdst = 0UL;
+}
+
+#define tcp_skb_tsorted_save(skb) {		\
+	unsigned long _save = skb->_skb_refdst;	\
+	skb->_skb_refdst = 0UL;
+
+#define tcp_skb_tsorted_restore(skb)		\
+	skb->_skb_refdst = _save;		\
+}
+
+void tcp_write_queue_purge(struct sock *sk);
+
+static inline struct sk_buff *tcp_rtx_queue_head(const struct sock *sk)
+{
+	return skb_rb_first(&sk->tcp_rtx_queue);
+}
+
+static inline struct sk_buff *tcp_rtx_queue_tail(const struct sock *sk)
+{
+	return skb_rb_last(&sk->tcp_rtx_queue);
+}
+
+static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
+{
+	return skb_peek(&sk->sk_write_queue);
+}
+
+static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
+{
+	return skb_peek_tail(&sk->sk_write_queue);
+}
+
+#define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
+	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
+
+static inline struct sk_buff *tcp_send_head(const struct sock *sk)
+{
+	return skb_peek(&sk->sk_write_queue);
+}
+
+static inline bool tcp_skb_is_last(const struct sock *sk,
+				   const struct sk_buff *skb)
+{
+	return skb_queue_is_last(&sk->sk_write_queue, skb);
+}
+
+static inline bool tcp_write_queue_empty(const struct sock *sk)
+{
+	return skb_queue_empty(&sk->sk_write_queue);
+}
+
+static inline bool tcp_rtx_queue_empty(const struct sock *sk)
+{
+	return RB_EMPTY_ROOT(&sk->tcp_rtx_queue);
+}
+
+static inline bool tcp_rtx_and_write_queues_empty(const struct sock *sk)
+{
+	return tcp_rtx_queue_empty(sk) && tcp_write_queue_empty(sk);
+}
+
+static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
+{
+	if (tcp_write_queue_empty(sk))
+		tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
+}
+
+static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
+{
+	__skb_queue_tail(&sk->sk_write_queue, skb);
+}
+
+static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
+{
+	__tcp_add_write_queue_tail(sk, skb);
+
+	/* Queue it, remembering where we must start sending. */
+	if (sk->sk_write_queue.next == skb)
+		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
+}
+
+/* Insert new before skb on the write queue of sk.  */
+static inline void tcp_insert_write_queue_before(struct sk_buff *new,
+						  struct sk_buff *skb,
+						  struct sock *sk)
+{
+	__skb_queue_before(&sk->sk_write_queue, skb, new);
+}
+
+static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
+{
+	tcp_skb_tsorted_anchor_cleanup(skb);
+	__skb_unlink(skb, &sk->sk_write_queue);
+}
+
+void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb);
+
+static inline void tcp_rtx_queue_unlink(struct sk_buff *skb, struct sock *sk)
+{
+	tcp_skb_tsorted_anchor_cleanup(skb);
+	rb_erase(&skb->rbnode, &sk->tcp_rtx_queue);
+}
+
+static inline void tcp_rtx_queue_unlink_and_free(struct sk_buff *skb, struct sock *sk)
+{
+	list_del(&skb->tcp_tsorted_anchor);
+	tcp_rtx_queue_unlink(skb, sk);
+	sk_wmem_free_skb(sk, skb);
+}
+
+static inline void tcp_push_pending_frames(struct sock *sk)
+{
+	if (tcp_send_head(sk)) {
+		struct tcp_sock *tp = tcp_sk(sk);
+
+		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
+	}
+}
+
+/* Start sequence of the skb just after the highest skb with SACKed
+ * bit, valid only if sacked_out > 0 or when the caller has ensured
+ * validity by itself.
+ */
+static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
+{
+	if (!tp->sacked_out)
+		return tp->snd_una;
+
+	if (tp->highest_sack == NULL)
+		return tp->snd_nxt;
+
+	return TCP_SKB_CB(tp->highest_sack)->seq;
+}
+
+static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
+{
+	tcp_sk(sk)->highest_sack = skb_rb_next(skb);
+}
+
+static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
+{
+	return tcp_sk(sk)->highest_sack;
+}
+
+static inline void tcp_highest_sack_reset(struct sock *sk)
+{
+	tcp_sk(sk)->highest_sack = tcp_rtx_queue_head(sk);
+}
+
+/* Called when old skb is about to be deleted and replaced by new skb */
+static inline void tcp_highest_sack_replace(struct sock *sk,
+					    struct sk_buff *old,
+					    struct sk_buff *new)
+{
+	if (old == tcp_highest_sack(sk))
+		tcp_sk(sk)->highest_sack = new;
+}
+
+/* This helper checks if socket has IP_TRANSPARENT set */
+static inline bool inet_sk_transparent(const struct sock *sk)
+{
+	switch (sk->sk_state) {
+	case TCP_TIME_WAIT:
+		return inet_twsk(sk)->tw_transparent;
+	case TCP_NEW_SYN_RECV:
+		return inet_rsk(inet_reqsk(sk))->no_srccheck;
+	}
+	return inet_sk(sk)->transparent;
+}
+
+/* Determines whether this is a thin stream (which may suffer from
+ * increased latency). Used to trigger latency-reducing mechanisms.
+ */
+static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
+{
+	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
+}
+
+/* /proc */
+enum tcp_seq_states {
+	TCP_SEQ_STATE_LISTENING,
+	TCP_SEQ_STATE_ESTABLISHED,
+};
+
+void *tcp_seq_start(struct seq_file *seq, loff_t *pos);
+void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos);
+void tcp_seq_stop(struct seq_file *seq, void *v);
+
+struct tcp_seq_afinfo {
+	sa_family_t			family;
+};
+
+struct tcp_iter_state {
+	struct seq_net_private	p;
+	enum tcp_seq_states	state;
+	struct sock		*syn_wait_sk;
+	int			bucket, offset, sbucket, num;
+	loff_t			last_pos;
+};
+
+extern struct request_sock_ops tcp_request_sock_ops;
+extern struct request_sock_ops tcp6_request_sock_ops;
+
+void tcp_v4_destroy_sock(struct sock *sk);
+
+struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
+				netdev_features_t features);
+struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb);
+int tcp_gro_complete(struct sk_buff *skb);
+
+void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
+
+static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
+{
+	struct net *net = sock_net((struct sock *)tp);
+	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
+}
+
+static inline bool tcp_stream_memory_free(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	u32 notsent_bytes = READ_ONCE(tp->write_seq) - tp->snd_nxt;
+
+	return notsent_bytes < tcp_notsent_lowat(tp);
+}
+
+#ifdef CONFIG_PROC_FS
+int tcp4_proc_init(void);
+void tcp4_proc_exit(void);
+#endif
+
+int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
+int tcp_conn_request(struct request_sock_ops *rsk_ops,
+		     const struct tcp_request_sock_ops *af_ops,
+		     struct sock *sk, struct sk_buff *skb);
+
+/* TCP af-specific functions */
+struct tcp_sock_af_ops {
+#ifdef CONFIG_TCP_MD5SIG
+	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
+						const struct sock *addr_sk);
+	int		(*calc_md5_hash)(char *location,
+					 const struct tcp_md5sig_key *md5,
+					 const struct sock *sk,
+					 const struct sk_buff *skb);
+	int		(*md5_parse)(struct sock *sk,
+				     int optname,
+				     char __user *optval,
+				     int optlen);
+#endif
+};
+
+struct tcp_request_sock_ops {
+	u16 mss_clamp;
+#ifdef CONFIG_TCP_MD5SIG
+	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
+						 const struct sock *addr_sk);
+	int		(*calc_md5_hash) (char *location,
+					  const struct tcp_md5sig_key *md5,
+					  const struct sock *sk,
+					  const struct sk_buff *skb);
+#endif
+	void (*init_req)(struct request_sock *req,
+			 const struct sock *sk_listener,
+			 struct sk_buff *skb);
+#ifdef CONFIG_SYN_COOKIES
+	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
+				 __u16 *mss);
+#endif
+	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
+				       const struct request_sock *req);
+	u32 (*init_seq)(const struct sk_buff *skb);
+	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
+	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
+			   struct flowi *fl, struct request_sock *req,
+			   struct tcp_fastopen_cookie *foc,
+			   enum tcp_synack_type synack_type);
+};
+
+extern const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops;
+#if IS_ENABLED(CONFIG_IPV6)
+extern const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops;
+#endif
+
+#ifdef CONFIG_SYN_COOKIES
+static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
+					 const struct sock *sk, struct sk_buff *skb,
+					 __u16 *mss)
+{
+	tcp_synq_overflow(sk);
+	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
+	return ops->cookie_init_seq(skb, mss);
+}
+#else
+static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
+					 const struct sock *sk, struct sk_buff *skb,
+					 __u16 *mss)
+{
+	return 0;
+}
+#endif
+
+int tcpv4_offload_init(void);
+
+void tcp_v4_init(void);
+void tcp_init(void);
+
+/* tcp_recovery.c */
+void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb);
+void tcp_newreno_mark_lost(struct sock *sk, bool snd_una_advanced);
+extern s32 tcp_rack_skb_timeout(struct tcp_sock *tp, struct sk_buff *skb,
+				u32 reo_wnd);
+extern bool tcp_rack_mark_lost(struct sock *sk);
+extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
+			     u64 xmit_time);
+extern void tcp_rack_reo_timeout(struct sock *sk);
+extern void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs);
+
+/* At how many usecs into the future should the RTO fire? */
+static inline s64 tcp_rto_delta_us(const struct sock *sk)
+{
+	const struct sk_buff *skb = tcp_rtx_queue_head(sk);
+	u32 rto = inet_csk(sk)->icsk_rto;
+	u64 rto_time_stamp_us = skb->skb_mstamp + jiffies_to_usecs(rto);
+
+	return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
+}
+
+/*
+ * Save and compile IPv4 options, return a pointer to it
+ */
+static inline struct ip_options_rcu *tcp_v4_save_options(struct net *net,
+							 struct sk_buff *skb)
+{
+	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
+	struct ip_options_rcu *dopt = NULL;
+
+	if (opt->optlen) {
+		int opt_size = sizeof(*dopt) + opt->optlen;
+
+		dopt = kmalloc(opt_size, GFP_ATOMIC);
+		if (dopt && __ip_options_echo(net, &dopt->opt, skb, opt)) {
+			kfree(dopt);
+			dopt = NULL;
+		}
+	}
+	return dopt;
+}
+
+/* locally generated TCP pure ACKs have skb->truesize == 2
+ * (check tcp_send_ack() in net/ipv4/tcp_output.c )
+ * This is much faster than dissecting the packet to find out.
+ * (Think of GRE encapsulations, IPv4, IPv6, ...)
+ */
+static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
+{
+	return skb->truesize == 2;
+}
+
+static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
+{
+	skb->truesize = 2;
+}
+
+static inline int tcp_inq(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int answ;
+
+	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+		answ = 0;
+	} else if (sock_flag(sk, SOCK_URGINLINE) ||
+		   !tp->urg_data ||
+		   before(tp->urg_seq, tp->copied_seq) ||
+		   !before(tp->urg_seq, tp->rcv_nxt)) {
+
+		answ = tp->rcv_nxt - tp->copied_seq;
+
+		/* Subtract 1, if FIN was received */
+		if (answ && sock_flag(sk, SOCK_DONE))
+			answ--;
+	} else {
+		answ = tp->urg_seq - tp->copied_seq;
+	}
+
+	return answ;
+}
+
+int tcp_peek_len(struct socket *sock);
+
+static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
+{
+	u16 segs_in;
+
+	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
+	tp->segs_in += segs_in;
+	if (skb->len > tcp_hdrlen(skb))
+		tp->data_segs_in += segs_in;
+}
+
+/*
+ * TCP listen path runs lockless.
+ * We forced "struct sock" to be const qualified to make sure
+ * we don't modify one of its field by mistake.
+ * Here, we increment sk_drops which is an atomic_t, so we can safely
+ * make sock writable again.
+ */
+static inline void tcp_listendrop(const struct sock *sk)
+{
+	atomic_inc(&((struct sock *)sk)->sk_drops);
+	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
+}
+
+enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
+
+/*
+ * Interface for adding Upper Level Protocols over TCP
+ */
+
+#define TCP_ULP_NAME_MAX	16
+#define TCP_ULP_MAX		128
+#define TCP_ULP_BUF_MAX		(TCP_ULP_NAME_MAX*TCP_ULP_MAX)
+
+enum {
+	TCP_ULP_TLS,
+	TCP_ULP_BPF,
+};
+
+struct tcp_ulp_ops {
+	struct list_head	list;
+
+	/* initialize ulp */
+	int (*init)(struct sock *sk);
+	/* cleanup ulp */
+	void (*release)(struct sock *sk);
+
+	int		uid;
+	char		name[TCP_ULP_NAME_MAX];
+	bool		user_visible;
+	struct module	*owner;
+};
+int tcp_register_ulp(struct tcp_ulp_ops *type);
+void tcp_unregister_ulp(struct tcp_ulp_ops *type);
+int tcp_set_ulp(struct sock *sk, const char *name);
+int tcp_set_ulp_id(struct sock *sk, const int ulp);
+void tcp_get_available_ulp(char *buf, size_t len);
+void tcp_cleanup_ulp(struct sock *sk);
+
+#define MODULE_ALIAS_TCP_ULP(name)				\
+	__MODULE_INFO(alias, alias_userspace, name);		\
+	__MODULE_INFO(alias, alias_tcp_ulp, "tcp-ulp-" name)
+
+/* Call BPF_SOCK_OPS program that returns an int. If the return value
+ * is < 0, then the BPF op failed (for example if the loaded BPF
+ * program does not support the chosen operation or there is no BPF
+ * program loaded).
+ */
+#ifdef CONFIG_BPF
+static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	struct bpf_sock_ops_kern sock_ops;
+	int ret;
+
+	memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
+	if (sk_fullsock(sk)) {
+		sock_ops.is_fullsock = 1;
+		sock_owned_by_me(sk);
+	}
+
+	sock_ops.sk = sk;
+	sock_ops.op = op;
+	if (nargs > 0)
+		memcpy(sock_ops.args, args, nargs * sizeof(*args));
+
+	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
+	if (ret == 0)
+		ret = sock_ops.reply;
+	else
+		ret = -1;
+	return ret;
+}
+
+static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
+{
+	u32 args[2] = {arg1, arg2};
+
+	return tcp_call_bpf(sk, op, 2, args);
+}
+
+static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+				    u32 arg3)
+{
+	u32 args[3] = {arg1, arg2, arg3};
+
+	return tcp_call_bpf(sk, op, 3, args);
+}
+
+#else
+static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
+{
+	return -EPERM;
+}
+
+static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
+{
+	return -EPERM;
+}
+
+static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+				    u32 arg3)
+{
+	return -EPERM;
+}
+
+#endif
+
+static inline u32 tcp_timeout_init(struct sock *sk)
+{
+	int timeout;
+
+	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT, 0, NULL);
+
+	if (timeout <= 0)
+		timeout = TCP_TIMEOUT_INIT;
+	return timeout;
+}
+
+static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
+{
+	int rwnd;
+
+	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT, 0, NULL);
+
+	if (rwnd < 0)
+		rwnd = 0;
+	return rwnd;
+}
+
+static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
+{
+	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN, 0, NULL) == 1);
+}
+
+#if IS_ENABLED(CONFIG_SMC)
+extern struct static_key_false tcp_have_smc;
+#endif
+
+#if IS_ENABLED(CONFIG_TLS_DEVICE)
+void clean_acked_data_enable(struct inet_connection_sock *icsk,
+			     void (*cad)(struct sock *sk, u32 ack_seq));
+void clean_acked_data_disable(struct inet_connection_sock *icsk);
+
+#endif
+
+#endif	/* _TCP_H */