Initial import

1 files changed, 3225 insertions, 0 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
new file mode 100644
index 000000000..ca6faeb44
--- /dev/null
+++ b/net/ipv4/tcp.c
@@ -0,0 +1,3225 @@
+/*
+ * 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.
+ *
+ *		Implementation of the Transmission Control Protocol(TCP).
+ *
+ * Authors:	Ross Biro
+ *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *		Mark Evans, <evansmp@uhura.aston.ac.uk>
+ *		Corey Minyard <wf-rch!minyard@relay.EU.net>
+ *		Florian La Roche, <flla@stud.uni-sb.de>
+ *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
+ *		Linus Torvalds, <torvalds@cs.helsinki.fi>
+ *		Alan Cox, <gw4pts@gw4pts.ampr.org>
+ *		Matthew Dillon, <dillon@apollo.west.oic.com>
+ *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *		Jorge Cwik, <jorge@laser.satlink.net>
+ *
+ * Fixes:
+ *		Alan Cox	:	Numerous verify_area() calls
+ *		Alan Cox	:	Set the ACK bit on a reset
+ *		Alan Cox	:	Stopped it crashing if it closed while
+ *					sk->inuse=1 and was trying to connect
+ *					(tcp_err()).
+ *		Alan Cox	:	All icmp error handling was broken
+ *					pointers passed where wrong and the
+ *					socket was looked up backwards. Nobody
+ *					tested any icmp error code obviously.
+ *		Alan Cox	:	tcp_err() now handled properly. It
+ *					wakes people on errors. poll
+ *					behaves and the icmp error race
+ *					has gone by moving it into sock.c
+ *		Alan Cox	:	tcp_send_reset() fixed to work for
+ *					everything not just packets for
+ *					unknown sockets.
+ *		Alan Cox	:	tcp option processing.
+ *		Alan Cox	:	Reset tweaked (still not 100%) [Had
+ *					syn rule wrong]
+ *		Herp Rosmanith  :	More reset fixes
+ *		Alan Cox	:	No longer acks invalid rst frames.
+ *					Acking any kind of RST is right out.
+ *		Alan Cox	:	Sets an ignore me flag on an rst
+ *					receive otherwise odd bits of prattle
+ *					escape still
+ *		Alan Cox	:	Fixed another acking RST frame bug.
+ *					Should stop LAN workplace lockups.
+ *		Alan Cox	: 	Some tidyups using the new skb list
+ *					facilities
+ *		Alan Cox	:	sk->keepopen now seems to work
+ *		Alan Cox	:	Pulls options out correctly on accepts
+ *		Alan Cox	:	Fixed assorted sk->rqueue->next errors
+ *		Alan Cox	:	PSH doesn't end a TCP read. Switched a
+ *					bit to skb ops.
+ *		Alan Cox	:	Tidied tcp_data to avoid a potential
+ *					nasty.
+ *		Alan Cox	:	Added some better commenting, as the
+ *					tcp is hard to follow
+ *		Alan Cox	:	Removed incorrect check for 20 * psh
+ *	Michael O'Reilly	:	ack < copied bug fix.
+ *	Johannes Stille		:	Misc tcp fixes (not all in yet).
+ *		Alan Cox	:	FIN with no memory -> CRASH
+ *		Alan Cox	:	Added socket option proto entries.
+ *					Also added awareness of them to accept.
+ *		Alan Cox	:	Added TCP options (SOL_TCP)
+ *		Alan Cox	:	Switched wakeup calls to callbacks,
+ *					so the kernel can layer network
+ *					sockets.
+ *		Alan Cox	:	Use ip_tos/ip_ttl settings.
+ *		Alan Cox	:	Handle FIN (more) properly (we hope).
+ *		Alan Cox	:	RST frames sent on unsynchronised
+ *					state ack error.
+ *		Alan Cox	:	Put in missing check for SYN bit.
+ *		Alan Cox	:	Added tcp_select_window() aka NET2E
+ *					window non shrink trick.
+ *		Alan Cox	:	Added a couple of small NET2E timer
+ *					fixes
+ *		Charles Hedrick :	TCP fixes
+ *		Toomas Tamm	:	TCP window fixes
+ *		Alan Cox	:	Small URG fix to rlogin ^C ack fight
+ *		Charles Hedrick	:	Rewrote most of it to actually work
+ *		Linus		:	Rewrote tcp_read() and URG handling
+ *					completely
+ *		Gerhard Koerting:	Fixed some missing timer handling
+ *		Matthew Dillon  :	Reworked TCP machine states as per RFC
+ *		Gerhard Koerting:	PC/TCP workarounds
+ *		Adam Caldwell	:	Assorted timer/timing errors
+ *		Matthew Dillon	:	Fixed another RST bug
+ *		Alan Cox	:	Move to kernel side addressing changes.
+ *		Alan Cox	:	Beginning work on TCP fastpathing
+ *					(not yet usable)
+ *		Arnt Gulbrandsen:	Turbocharged tcp_check() routine.
+ *		Alan Cox	:	TCP fast path debugging
+ *		Alan Cox	:	Window clamping
+ *		Michael Riepe	:	Bug in tcp_check()
+ *		Matt Dillon	:	More TCP improvements and RST bug fixes
+ *		Matt Dillon	:	Yet more small nasties remove from the
+ *					TCP code (Be very nice to this man if
+ *					tcp finally works 100%) 8)
+ *		Alan Cox	:	BSD accept semantics.
+ *		Alan Cox	:	Reset on closedown bug.
+ *	Peter De Schrijver	:	ENOTCONN check missing in tcp_sendto().
+ *		Michael Pall	:	Handle poll() after URG properly in
+ *					all cases.
+ *		Michael Pall	:	Undo the last fix in tcp_read_urg()
+ *					(multi URG PUSH broke rlogin).
+ *		Michael Pall	:	Fix the multi URG PUSH problem in
+ *					tcp_readable(), poll() after URG
+ *					works now.
+ *		Michael Pall	:	recv(...,MSG_OOB) never blocks in the
+ *					BSD api.
+ *		Alan Cox	:	Changed the semantics of sk->socket to
+ *					fix a race and a signal problem with
+ *					accept() and async I/O.
+ *		Alan Cox	:	Relaxed the rules on tcp_sendto().
+ *		Yury Shevchuk	:	Really fixed accept() blocking problem.
+ *		Craig I. Hagan  :	Allow for BSD compatible TIME_WAIT for
+ *					clients/servers which listen in on
+ *					fixed ports.
+ *		Alan Cox	:	Cleaned the above up and shrank it to
+ *					a sensible code size.
+ *		Alan Cox	:	Self connect lockup fix.
+ *		Alan Cox	:	No connect to multicast.
+ *		Ross Biro	:	Close unaccepted children on master
+ *					socket close.
+ *		Alan Cox	:	Reset tracing code.
+ *		Alan Cox	:	Spurious resets on shutdown.
+ *		Alan Cox	:	Giant 15 minute/60 second timer error
+ *		Alan Cox	:	Small whoops in polling before an
+ *					accept.
+ *		Alan Cox	:	Kept the state trace facility since
+ *					it's handy for debugging.
+ *		Alan Cox	:	More reset handler fixes.
+ *		Alan Cox	:	Started rewriting the code based on
+ *					the RFC's for other useful protocol
+ *					references see: Comer, KA9Q NOS, and
+ *					for a reference on the difference
+ *					between specifications and how BSD
+ *					works see the 4.4lite source.
+ *		A.N.Kuznetsov	:	Don't time wait on completion of tidy
+ *					close.
+ *		Linus Torvalds	:	Fin/Shutdown & copied_seq changes.
+ *		Linus Torvalds	:	Fixed BSD port reuse to work first syn
+ *		Alan Cox	:	Reimplemented timers as per the RFC
+ *					and using multiple timers for sanity.
+ *		Alan Cox	:	Small bug fixes, and a lot of new
+ *					comments.
+ *		Alan Cox	:	Fixed dual reader crash by locking
+ *					the buffers (much like datagram.c)
+ *		Alan Cox	:	Fixed stuck sockets in probe. A probe
+ *					now gets fed up of retrying without
+ *					(even a no space) answer.
+ *		Alan Cox	:	Extracted closing code better
+ *		Alan Cox	:	Fixed the closing state machine to
+ *					resemble the RFC.
+ *		Alan Cox	:	More 'per spec' fixes.
+ *		Jorge Cwik	:	Even faster checksumming.
+ *		Alan Cox	:	tcp_data() doesn't ack illegal PSH
+ *					only frames. At least one pc tcp stack
+ *					generates them.
+ *		Alan Cox	:	Cache last socket.
+ *		Alan Cox	:	Per route irtt.
+ *		Matt Day	:	poll()->select() match BSD precisely on error
+ *		Alan Cox	:	New buffers
+ *		Marc Tamsky	:	Various sk->prot->retransmits and
+ *					sk->retransmits misupdating fixed.
+ *					Fixed tcp_write_timeout: stuck close,
+ *					and TCP syn retries gets used now.
+ *		Mark Yarvis	:	In tcp_read_wakeup(), don't send an
+ *					ack if state is TCP_CLOSED.
+ *		Alan Cox	:	Look up device on a retransmit - routes may
+ *					change. Doesn't yet cope with MSS shrink right
+ *					but it's a start!
+ *		Marc Tamsky	:	Closing in closing fixes.
+ *		Mike Shaver	:	RFC1122 verifications.
+ *		Alan Cox	:	rcv_saddr errors.
+ *		Alan Cox	:	Block double connect().
+ *		Alan Cox	:	Small hooks for enSKIP.
+ *		Alexey Kuznetsov:	Path MTU discovery.
+ *		Alan Cox	:	Support soft errors.
+ *		Alan Cox	:	Fix MTU discovery pathological case
+ *					when the remote claims no mtu!
+ *		Marc Tamsky	:	TCP_CLOSE fix.
+ *		Colin (G3TNE)	:	Send a reset on syn ack replies in
+ *					window but wrong (fixes NT lpd problems)
+ *		Pedro Roque	:	Better TCP window handling, delayed ack.
+ *		Joerg Reuter	:	No modification of locked buffers in
+ *					tcp_do_retransmit()
+ *		Eric Schenk	:	Changed receiver side silly window
+ *					avoidance algorithm to BSD style
+ *					algorithm. This doubles throughput
+ *					against machines running Solaris,
+ *					and seems to result in general
+ *					improvement.
+ *	Stefan Magdalinski	:	adjusted tcp_readable() to fix FIONREAD
+ *	Willy Konynenberg	:	Transparent proxying support.
+ *	Mike McLagan		:	Routing by source
+ *		Keith Owens	:	Do proper merging with partial SKB's in
+ *					tcp_do_sendmsg to avoid burstiness.
+ *		Eric Schenk	:	Fix fast close down bug with
+ *					shutdown() followed by close().
+ *		Andi Kleen 	:	Make poll agree with SIGIO
+ *	Salvatore Sanfilippo	:	Support SO_LINGER with linger == 1 and
+ *					lingertime == 0 (RFC 793 ABORT Call)
+ *	Hirokazu Takahashi	:	Use copy_from_user() instead of
+ *					csum_and_copy_from_user() if possible.
+ *
+ *		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.
+ *
+ * Description of States:
+ *
+ *	TCP_SYN_SENT		sent a connection request, waiting for ack
+ *
+ *	TCP_SYN_RECV		received a connection request, sent ack,
+ *				waiting for final ack in three-way handshake.
+ *
+ *	TCP_ESTABLISHED		connection established
+ *
+ *	TCP_FIN_WAIT1		our side has shutdown, waiting to complete
+ *				transmission of remaining buffered data
+ *
+ *	TCP_FIN_WAIT2		all buffered data sent, waiting for remote
+ *				to shutdown
+ *
+ *	TCP_CLOSING		both sides have shutdown but we still have
+ *				data we have to finish sending
+ *
+ *	TCP_TIME_WAIT		timeout to catch resent junk before entering
+ *				closed, can only be entered from FIN_WAIT2
+ *				or CLOSING.  Required because the other end
+ *				may not have gotten our last ACK causing it
+ *				to retransmit the data packet (which we ignore)
+ *
+ *	TCP_CLOSE_WAIT		remote side has shutdown and is waiting for
+ *				us to finish writing our data and to shutdown
+ *				(we have to close() to move on to LAST_ACK)
+ *
+ *	TCP_LAST_ACK		out side has shutdown after remote has
+ *				shutdown.  There may still be data in our
+ *				buffer that we have to finish sending
+ *
+ *	TCP_CLOSE		socket is finished
+ */
+
+#define pr_fmt(fmt) "TCP: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/poll.h>
+#include <linux/inet_diag.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/skbuff.h>
+#include <linux/scatterlist.h>
+#include <linux/splice.h>
+#include <linux/net.h>
+#include <linux/socket.h>
+#include <linux/random.h>
+#include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <linux/swap.h>
+#include <linux/cache.h>
+#include <linux/err.h>
+#include <linux/crypto.h>
+#include <linux/time.h>
+#include <linux/slab.h>
+
+#include <net/icmp.h>
+#include <net/inet_common.h>
+#include <net/tcp.h>
+#include <net/xfrm.h>
+#include <net/ip.h>
+#include <net/sock.h>
+
+#include <asm/uaccess.h>
+#include <asm/ioctls.h>
+#include <net/busy_poll.h>
+
+int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;
+
+int sysctl_tcp_min_tso_segs __read_mostly = 2;
+
+int sysctl_tcp_autocorking __read_mostly = 1;
+
+struct percpu_counter tcp_orphan_count;
+EXPORT_SYMBOL_GPL(tcp_orphan_count);
+
+long sysctl_tcp_mem[3] __read_mostly;
+int sysctl_tcp_wmem[3] __read_mostly;
+int sysctl_tcp_rmem[3] __read_mostly;
+
+EXPORT_SYMBOL(sysctl_tcp_mem);
+EXPORT_SYMBOL(sysctl_tcp_rmem);
+EXPORT_SYMBOL(sysctl_tcp_wmem);
+
+atomic_long_t tcp_memory_allocated;	/* Current allocated memory. */
+EXPORT_SYMBOL(tcp_memory_allocated);
+
+/*
+ * Current number of TCP sockets.
+ */
+struct percpu_counter tcp_sockets_allocated;
+EXPORT_SYMBOL(tcp_sockets_allocated);
+
+/*
+ * TCP splice context
+ */
+struct tcp_splice_state {
+	struct pipe_inode_info *pipe;
+	size_t len;
+	unsigned int flags;
+};
+
+/*
+ * Pressure flag: try to collapse.
+ * Technical note: it is used by multiple contexts non atomically.
+ * All the __sk_mem_schedule() is of this nature: accounting
+ * is strict, actions are advisory and have some latency.
+ */
+int tcp_memory_pressure __read_mostly;
+EXPORT_SYMBOL(tcp_memory_pressure);
+
+void tcp_enter_memory_pressure(struct sock *sk)
+{
+	if (!tcp_memory_pressure) {
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES);
+		tcp_memory_pressure = 1;
+	}
+}
+EXPORT_SYMBOL(tcp_enter_memory_pressure);
+
+/* Convert seconds to retransmits based on initial and max timeout */
+static u8 secs_to_retrans(int seconds, int timeout, int rto_max)
+{
+	u8 res = 0;
+
+	if (seconds > 0) {
+		int period = timeout;
+
+		res = 1;
+		while (seconds > period && res < 255) {
+			res++;
+			timeout <<= 1;
+			if (timeout > rto_max)
+				timeout = rto_max;
+			period += timeout;
+		}
+	}
+	return res;
+}
+
+/* Convert retransmits to seconds based on initial and max timeout */
+static int retrans_to_secs(u8 retrans, int timeout, int rto_max)
+{
+	int period = 0;
+
+	if (retrans > 0) {
+		period = timeout;
+		while (--retrans) {
+			timeout <<= 1;
+			if (timeout > rto_max)
+				timeout = rto_max;
+			period += timeout;
+		}
+	}
+	return period;
+}
+
+/* Address-family independent initialization for a tcp_sock.
+ *
+ * NOTE: A lot of things set to zero explicitly by call to
+ *       sk_alloc() so need not be done here.
+ */
+void tcp_init_sock(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	__skb_queue_head_init(&tp->out_of_order_queue);
+	tcp_init_xmit_timers(sk);
+	tcp_prequeue_init(tp);
+	INIT_LIST_HEAD(&tp->tsq_node);
+
+	icsk->icsk_rto = TCP_TIMEOUT_INIT;
+	tp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
+
+	/* So many TCP implementations out there (incorrectly) count the
+	 * initial SYN frame in their delayed-ACK and congestion control
+	 * algorithms that we must have the following bandaid to talk
+	 * efficiently to them.  -DaveM
+	 */
+	tp->snd_cwnd = TCP_INIT_CWND;
+
+	/* See draft-stevens-tcpca-spec-01 for discussion of the
+	 * initialization of these values.
+	 */
+	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
+	tp->snd_cwnd_clamp = ~0;
+	tp->mss_cache = TCP_MSS_DEFAULT;
+	u64_stats_init(&tp->syncp);
+
+	tp->reordering = sysctl_tcp_reordering;
+	tcp_enable_early_retrans(tp);
+	tcp_assign_congestion_control(sk);
+
+	tp->tsoffset = 0;
+
+	sk->sk_state = TCP_CLOSE;
+
+	sk->sk_write_space = sk_stream_write_space;
+	sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
+
+	icsk->icsk_sync_mss = tcp_sync_mss;
+
+	sk->sk_sndbuf = sysctl_tcp_wmem[1];
+	sk->sk_rcvbuf = sysctl_tcp_rmem[1];
+
+	local_bh_disable();
+	sock_update_memcg(sk);
+	sk_sockets_allocated_inc(sk);
+	local_bh_enable();
+}
+EXPORT_SYMBOL(tcp_init_sock);
+
+static void tcp_tx_timestamp(struct sock *sk, struct sk_buff *skb)
+{
+	if (sk->sk_tsflags) {
+		struct skb_shared_info *shinfo = skb_shinfo(skb);
+
+		sock_tx_timestamp(sk, &shinfo->tx_flags);
+		if (shinfo->tx_flags & SKBTX_ANY_TSTAMP)
+			shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
+	}
+}
+
+/*
+ *	Wait for a TCP event.
+ *
+ *	Note that we don't need to lock the socket, as the upper poll layers
+ *	take care of normal races (between the test and the event) and we don't
+ *	go look at any of the socket buffers directly.
+ */
+unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
+{
+	unsigned int mask;
+	struct sock *sk = sock->sk;
+	const struct tcp_sock *tp = tcp_sk(sk);
+
+	sock_rps_record_flow(sk);
+
+	sock_poll_wait(file, sk_sleep(sk), wait);
+	if (sk->sk_state == TCP_LISTEN)
+		return inet_csk_listen_poll(sk);
+
+	/* Socket is not locked. We are protected from async events
+	 * by poll logic and correct handling of state changes
+	 * made by other threads is impossible in any case.
+	 */
+
+	mask = 0;
+
+	/*
+	 * POLLHUP is certainly not done right. But poll() doesn't
+	 * have a notion of HUP in just one direction, and for a
+	 * socket the read side is more interesting.
+	 *
+	 * Some poll() documentation says that POLLHUP is incompatible
+	 * with the POLLOUT/POLLWR flags, so somebody should check this
+	 * all. But careful, it tends to be safer to return too many
+	 * bits than too few, and you can easily break real applications
+	 * if you don't tell them that something has hung up!
+	 *
+	 * Check-me.
+	 *
+	 * Check number 1. POLLHUP is _UNMASKABLE_ event (see UNIX98 and
+	 * our fs/select.c). It means that after we received EOF,
+	 * poll always returns immediately, making impossible poll() on write()
+	 * in state CLOSE_WAIT. One solution is evident --- to set POLLHUP
+	 * if and only if shutdown has been made in both directions.
+	 * Actually, it is interesting to look how Solaris and DUX
+	 * solve this dilemma. I would prefer, if POLLHUP were maskable,
+	 * then we could set it on SND_SHUTDOWN. BTW examples given
+	 * in Stevens' books assume exactly this behaviour, it explains
+	 * why POLLHUP is incompatible with POLLOUT.	--ANK
+	 *
+	 * NOTE. Check for TCP_CLOSE is added. The goal is to prevent
+	 * blocking on fresh not-connected or disconnected socket. --ANK
+	 */
+	if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == TCP_CLOSE)
+		mask |= POLLHUP;
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLIN | POLLRDNORM | POLLRDHUP;
+
+	/* Connected or passive Fast Open socket? */
+	if (sk->sk_state != TCP_SYN_SENT &&
+	    (sk->sk_state != TCP_SYN_RECV || tp->fastopen_rsk)) {
+		int target = sock_rcvlowat(sk, 0, INT_MAX);
+
+		if (tp->urg_seq == tp->copied_seq &&
+		    !sock_flag(sk, SOCK_URGINLINE) &&
+		    tp->urg_data)
+			target++;
+
+		/* Potential race condition. If read of tp below will
+		 * escape above sk->sk_state, we can be illegally awaken
+		 * in SYN_* states. */
+		if (tp->rcv_nxt - tp->copied_seq >= target)
+			mask |= POLLIN | POLLRDNORM;
+
+		if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
+			if (sk_stream_is_writeable(sk)) {
+				mask |= POLLOUT | POLLWRNORM;
+			} else {  /* send SIGIO later */
+				set_bit(SOCK_ASYNC_NOSPACE,
+					&sk->sk_socket->flags);
+				set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+
+				/* Race breaker. If space is freed after
+				 * wspace test but before the flags are set,
+				 * IO signal will be lost. Memory barrier
+				 * pairs with the input side.
+				 */
+				smp_mb__after_atomic();
+				if (sk_stream_is_writeable(sk))
+					mask |= POLLOUT | POLLWRNORM;
+			}
+		} else
+			mask |= POLLOUT | POLLWRNORM;
+
+		if (tp->urg_data & TCP_URG_VALID)
+			mask |= POLLPRI;
+	}
+	/* This barrier is coupled with smp_wmb() in tcp_reset() */
+	smp_rmb();
+	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
+		mask |= POLLERR;
+
+	return mask;
+}
+EXPORT_SYMBOL(tcp_poll);
+
+int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int answ;
+	bool slow;
+
+	switch (cmd) {
+	case SIOCINQ:
+		if (sk->sk_state == TCP_LISTEN)
+			return -EINVAL;
+
+		slow = lock_sock_fast(sk);
+		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;
+		unlock_sock_fast(sk, slow);
+		break;
+	case SIOCATMARK:
+		answ = tp->urg_data && tp->urg_seq == tp->copied_seq;
+		break;
+	case SIOCOUTQ:
+		if (sk->sk_state == TCP_LISTEN)
+			return -EINVAL;
+
+		if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+			answ = 0;
+		else
+			answ = tp->write_seq - tp->snd_una;
+		break;
+	case SIOCOUTQNSD:
+		if (sk->sk_state == TCP_LISTEN)
+			return -EINVAL;
+
+		if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+			answ = 0;
+		else
+			answ = tp->write_seq - tp->snd_nxt;
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return put_user(answ, (int __user *)arg);
+}
+EXPORT_SYMBOL(tcp_ioctl);
+
+static inline void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb)
+{
+	TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
+	tp->pushed_seq = tp->write_seq;
+}
+
+static inline bool forced_push(const struct tcp_sock *tp)
+{
+	return after(tp->write_seq, tp->pushed_seq + (tp->max_window >> 1));
+}
+
+static void skb_entail(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
+
+	skb->csum    = 0;
+	tcb->seq     = tcb->end_seq = tp->write_seq;
+	tcb->tcp_flags = TCPHDR_ACK;
+	tcb->sacked  = 0;
+	__skb_header_release(skb);
+	tcp_add_write_queue_tail(sk, skb);
+	sk->sk_wmem_queued += skb->truesize;
+	sk_mem_charge(sk, skb->truesize);
+	if (tp->nonagle & TCP_NAGLE_PUSH)
+		tp->nonagle &= ~TCP_NAGLE_PUSH;
+}
+
+static inline void tcp_mark_urg(struct tcp_sock *tp, int flags)
+{
+	if (flags & MSG_OOB)
+		tp->snd_up = tp->write_seq;
+}
+
+/* If a not yet filled skb is pushed, do not send it if
+ * we have data packets in Qdisc or NIC queues :
+ * Because TX completion will happen shortly, it gives a chance
+ * to coalesce future sendmsg() payload into this skb, without
+ * need for a timer, and with no latency trade off.
+ * As packets containing data payload have a bigger truesize
+ * than pure acks (dataless) packets, the last checks prevent
+ * autocorking if we only have an ACK in Qdisc/NIC queues,
+ * or if TX completion was delayed after we processed ACK packet.
+ */
+static bool tcp_should_autocork(struct sock *sk, struct sk_buff *skb,
+				int size_goal)
+{
+	return skb->len < size_goal &&
+	       sysctl_tcp_autocorking &&
+	       skb != tcp_write_queue_head(sk) &&
+	       atomic_read(&sk->sk_wmem_alloc) > skb->truesize;
+}
+
+static void tcp_push(struct sock *sk, int flags, int mss_now,
+		     int nonagle, int size_goal)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+
+	if (!tcp_send_head(sk))
+		return;
+
+	skb = tcp_write_queue_tail(sk);
+	if (!(flags & MSG_MORE) || forced_push(tp))
+		tcp_mark_push(tp, skb);
+
+	tcp_mark_urg(tp, flags);
+
+	if (tcp_should_autocork(sk, skb, size_goal)) {
+
+		/* avoid atomic op if TSQ_THROTTLED bit is already set */
+		if (!test_bit(TSQ_THROTTLED, &tp->tsq_flags)) {
+			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTOCORKING);
+			set_bit(TSQ_THROTTLED, &tp->tsq_flags);
+		}
+		/* It is possible TX completion already happened
+		 * before we set TSQ_THROTTLED.
+		 */
+		if (atomic_read(&sk->sk_wmem_alloc) > skb->truesize)
+			return;
+	}
+
+	if (flags & MSG_MORE)
+		nonagle = TCP_NAGLE_CORK;
+
+	__tcp_push_pending_frames(sk, mss_now, nonagle);
+}
+
+static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
+				unsigned int offset, size_t len)
+{
+	struct tcp_splice_state *tss = rd_desc->arg.data;
+	int ret;
+
+	ret = skb_splice_bits(skb, offset, tss->pipe, min(rd_desc->count, len),
+			      tss->flags);
+	if (ret > 0)
+		rd_desc->count -= ret;
+	return ret;
+}
+
+static int __tcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
+{
+	/* Store TCP splice context information in read_descriptor_t. */
+	read_descriptor_t rd_desc = {
+		.arg.data = tss,
+		.count	  = tss->len,
+	};
+
+	return tcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
+}
+
+/**
+ *  tcp_splice_read - splice data from TCP socket to a pipe
+ * @sock:	socket to splice from
+ * @ppos:	position (not valid)
+ * @pipe:	pipe to splice to
+ * @len:	number of bytes to splice
+ * @flags:	splice modifier flags
+ *
+ * Description:
+ *    Will read pages from given socket and fill them into a pipe.
+ *
+ **/
+ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
+			struct pipe_inode_info *pipe, size_t len,
+			unsigned int flags)
+{
+	struct sock *sk = sock->sk;
+	struct tcp_splice_state tss = {
+		.pipe = pipe,
+		.len = len,
+		.flags = flags,
+	};
+	long timeo;
+	ssize_t spliced;
+	int ret;
+
+	sock_rps_record_flow(sk);
+	/*
+	 * We can't seek on a socket input
+	 */
+	if (unlikely(*ppos))
+		return -ESPIPE;
+
+	ret = spliced = 0;
+
+	lock_sock(sk);
+
+	timeo = sock_rcvtimeo(sk, sock->file->f_flags & O_NONBLOCK);
+	while (tss.len) {
+		ret = __tcp_splice_read(sk, &tss);
+		if (ret < 0)
+			break;
+		else if (!ret) {
+			if (spliced)
+				break;
+			if (sock_flag(sk, SOCK_DONE))
+				break;
+			if (sk->sk_err) {
+				ret = sock_error(sk);
+				break;
+			}
+			if (sk->sk_shutdown & RCV_SHUTDOWN)
+				break;
+			if (sk->sk_state == TCP_CLOSE) {
+				/*
+				 * This occurs when user tries to read
+				 * from never connected socket.
+				 */
+				if (!sock_flag(sk, SOCK_DONE))
+					ret = -ENOTCONN;
+				break;
+			}
+			if (!timeo) {
+				ret = -EAGAIN;
+				break;
+			}
+			sk_wait_data(sk, &timeo);
+			if (signal_pending(current)) {
+				ret = sock_intr_errno(timeo);
+				break;
+			}
+			continue;
+		}
+		tss.len -= ret;
+		spliced += ret;
+
+		if (!timeo)
+			break;
+		release_sock(sk);
+		lock_sock(sk);
+
+		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
+		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
+		    signal_pending(current))
+			break;
+	}
+
+	release_sock(sk);
+
+	if (spliced)
+		return spliced;
+
+	return ret;
+}
+EXPORT_SYMBOL(tcp_splice_read);
+
+struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
+{
+	struct sk_buff *skb;
+
+	/* The TCP header must be at least 32-bit aligned.  */
+	size = ALIGN(size, 4);
+
+	skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp);
+	if (skb) {
+		if (sk_wmem_schedule(sk, skb->truesize)) {
+			skb_reserve(skb, sk->sk_prot->max_header);
+			/*
+			 * Make sure that we have exactly size bytes
+			 * available to the caller, no more, no less.
+			 */
+			skb->reserved_tailroom = skb->end - skb->tail - size;
+			return skb;
+		}
+		__kfree_skb(skb);
+	} else {
+		sk->sk_prot->enter_memory_pressure(sk);
+		sk_stream_moderate_sndbuf(sk);
+	}
+	return NULL;
+}
+
+static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now,
+				       int large_allowed)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 new_size_goal, size_goal;
+
+	if (!large_allowed || !sk_can_gso(sk))
+		return mss_now;
+
+	/* Note : tcp_tso_autosize() will eventually split this later */
+	new_size_goal = sk->sk_gso_max_size - 1 - MAX_TCP_HEADER;
+	new_size_goal = tcp_bound_to_half_wnd(tp, new_size_goal);
+
+	/* We try hard to avoid divides here */
+	size_goal = tp->gso_segs * mss_now;
+	if (unlikely(new_size_goal < size_goal ||
+		     new_size_goal >= size_goal + mss_now)) {
+		tp->gso_segs = min_t(u16, new_size_goal / mss_now,
+				     sk->sk_gso_max_segs);
+		size_goal = tp->gso_segs * mss_now;
+	}
+
+	return max(size_goal, mss_now);
+}
+
+static int tcp_send_mss(struct sock *sk, int *size_goal, int flags)
+{
+	int mss_now;
+
+	mss_now = tcp_current_mss(sk);
+	*size_goal = tcp_xmit_size_goal(sk, mss_now, !(flags & MSG_OOB));
+
+	return mss_now;
+}
+
+static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
+				size_t size, int flags)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int mss_now, size_goal;
+	int err;
+	ssize_t copied;
+	long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
+
+	/* Wait for a connection to finish. One exception is TCP Fast Open
+	 * (passive side) where data is allowed to be sent before a connection
+	 * is fully established.
+	 */
+	if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+	    !tcp_passive_fastopen(sk)) {
+		if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
+			goto out_err;
+	}
+
+	clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+
+	mss_now = tcp_send_mss(sk, &size_goal, flags);
+	copied = 0;
+
+	err = -EPIPE;
+	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
+		goto out_err;
+
+	while (size > 0) {
+		struct sk_buff *skb = tcp_write_queue_tail(sk);
+		int copy, i;
+		bool can_coalesce;
+
+		if (!tcp_send_head(sk) || (copy = size_goal - skb->len) <= 0) {
+new_segment:
+			if (!sk_stream_memory_free(sk))
+				goto wait_for_sndbuf;
+
+			skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation);
+			if (!skb)
+				goto wait_for_memory;
+
+			skb_entail(sk, skb);
+			copy = size_goal;
+		}
+
+		if (copy > size)
+			copy = size;
+
+		i = skb_shinfo(skb)->nr_frags;
+		can_coalesce = skb_can_coalesce(skb, i, page, offset);
+		if (!can_coalesce && i >= MAX_SKB_FRAGS) {
+			tcp_mark_push(tp, skb);
+			goto new_segment;
+		}
+		if (!sk_wmem_schedule(sk, copy))
+			goto wait_for_memory;
+
+		if (can_coalesce) {
+			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
+		} else {
+			get_page(page);
+			skb_fill_page_desc(skb, i, page, offset, copy);
+		}
+		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+
+		skb->len += copy;
+		skb->data_len += copy;
+		skb->truesize += copy;
+		sk->sk_wmem_queued += copy;
+		sk_mem_charge(sk, copy);
+		skb->ip_summed = CHECKSUM_PARTIAL;
+		tp->write_seq += copy;
+		TCP_SKB_CB(skb)->end_seq += copy;
+		tcp_skb_pcount_set(skb, 0);
+
+		if (!copied)
+			TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
+
+		copied += copy;
+		offset += copy;
+		if (!(size -= copy)) {
+			tcp_tx_timestamp(sk, skb);
+			goto out;
+		}
+
+		if (skb->len < size_goal || (flags & MSG_OOB))
+			continue;
+
+		if (forced_push(tp)) {
+			tcp_mark_push(tp, skb);
+			__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_PUSH);
+		} else if (skb == tcp_send_head(sk))
+			tcp_push_one(sk, mss_now);
+		continue;
+
+wait_for_sndbuf:
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+wait_for_memory:
+		tcp_push(sk, flags & ~MSG_MORE, mss_now,
+			 TCP_NAGLE_PUSH, size_goal);
+
+		if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
+			goto do_error;
+
+		mss_now = tcp_send_mss(sk, &size_goal, flags);
+	}
+
+out:
+	if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
+		tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
+	return copied;
+
+do_error:
+	if (copied)
+		goto out;
+out_err:
+	return sk_stream_error(sk, flags, err);
+}
+
+int tcp_sendpage(struct sock *sk, struct page *page, int offset,
+		 size_t size, int flags)
+{
+	ssize_t res;
+
+	if (!(sk->sk_route_caps & NETIF_F_SG) ||
+	    !(sk->sk_route_caps & NETIF_F_ALL_CSUM))
+		return sock_no_sendpage(sk->sk_socket, page, offset, size,
+					flags);
+
+	lock_sock(sk);
+	res = do_tcp_sendpages(sk, page, offset, size, flags);
+	release_sock(sk);
+	return res;
+}
+EXPORT_SYMBOL(tcp_sendpage);
+
+static inline int select_size(const struct sock *sk, bool sg)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	int tmp = tp->mss_cache;
+
+	if (sg) {
+		if (sk_can_gso(sk)) {
+			/* Small frames wont use a full page:
+			 * Payload will immediately follow tcp header.
+			 */
+			tmp = SKB_WITH_OVERHEAD(2048 - MAX_TCP_HEADER);
+		} else {
+			int pgbreak = SKB_MAX_HEAD(MAX_TCP_HEADER);
+
+			if (tmp >= pgbreak &&
+			    tmp <= pgbreak + (MAX_SKB_FRAGS - 1) * PAGE_SIZE)
+				tmp = pgbreak;
+		}
+	}
+
+	return tmp;
+}
+
+void tcp_free_fastopen_req(struct tcp_sock *tp)
+{
+	if (tp->fastopen_req) {
+		kfree(tp->fastopen_req);
+		tp->fastopen_req = NULL;
+	}
+}
+
+static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
+				int *copied, size_t size)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int err, flags;
+
+	if (!(sysctl_tcp_fastopen & TFO_CLIENT_ENABLE))
+		return -EOPNOTSUPP;
+	if (tp->fastopen_req)
+		return -EALREADY; /* Another Fast Open is in progress */
+
+	tp->fastopen_req = kzalloc(sizeof(struct tcp_fastopen_request),
+				   sk->sk_allocation);
+	if (unlikely(!tp->fastopen_req))
+		return -ENOBUFS;
+	tp->fastopen_req->data = msg;
+	tp->fastopen_req->size = size;
+
+	flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
+	err = __inet_stream_connect(sk->sk_socket, msg->msg_name,
+				    msg->msg_namelen, flags);
+	*copied = tp->fastopen_req->copied;
+	tcp_free_fastopen_req(tp);
+	return err;
+}
+
+int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+	int flags, err, copied = 0;
+	int mss_now = 0, size_goal, copied_syn = 0;
+	bool sg;
+	long timeo;
+
+	lock_sock(sk);
+
+	flags = msg->msg_flags;
+	if (flags & MSG_FASTOPEN) {
+		err = tcp_sendmsg_fastopen(sk, msg, &copied_syn, size);
+		if (err == -EINPROGRESS && copied_syn > 0)
+			goto out;
+		else if (err)
+			goto out_err;
+	}
+
+	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
+
+	/* Wait for a connection to finish. One exception is TCP Fast Open
+	 * (passive side) where data is allowed to be sent before a connection
+	 * is fully established.
+	 */
+	if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+	    !tcp_passive_fastopen(sk)) {
+		if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
+			goto do_error;
+	}
+
+	if (unlikely(tp->repair)) {
+		if (tp->repair_queue == TCP_RECV_QUEUE) {
+			copied = tcp_send_rcvq(sk, msg, size);
+			goto out_nopush;
+		}
+
+		err = -EINVAL;
+		if (tp->repair_queue == TCP_NO_QUEUE)
+			goto out_err;
+
+		/* 'common' sending to sendq */
+	}
+
+	/* This should be in poll */
+	clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+
+	mss_now = tcp_send_mss(sk, &size_goal, flags);
+
+	/* Ok commence sending. */
+	copied = 0;
+
+	err = -EPIPE;
+	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
+		goto out_err;
+
+	sg = !!(sk->sk_route_caps & NETIF_F_SG);
+
+	while (msg_data_left(msg)) {
+		int copy = 0;
+		int max = size_goal;
+
+		skb = tcp_write_queue_tail(sk);
+		if (tcp_send_head(sk)) {
+			if (skb->ip_summed == CHECKSUM_NONE)
+				max = mss_now;
+			copy = max - skb->len;
+		}
+
+		if (copy <= 0) {
+new_segment:
+			/* Allocate new segment. If the interface is SG,
+			 * allocate skb fitting to single page.
+			 */
+			if (!sk_stream_memory_free(sk))
+				goto wait_for_sndbuf;
+
+			skb = sk_stream_alloc_skb(sk,
+						  select_size(sk, sg),
+						  sk->sk_allocation);
+			if (!skb)
+				goto wait_for_memory;
+
+			/*
+			 * Check whether we can use HW checksum.
+			 */
+			if (sk->sk_route_caps & NETIF_F_ALL_CSUM)
+				skb->ip_summed = CHECKSUM_PARTIAL;
+
+			skb_entail(sk, skb);
+			copy = size_goal;
+			max = size_goal;
+
+			/* All packets are restored as if they have
+			 * already been sent. skb_mstamp isn't set to
+			 * avoid wrong rtt estimation.
+			 */
+			if (tp->repair)
+				TCP_SKB_CB(skb)->sacked |= TCPCB_REPAIRED;
+		}
+
+		/* Try to append data to the end of skb. */
+		if (copy > msg_data_left(msg))
+			copy = msg_data_left(msg);
+
+		/* Where to copy to? */
+		if (skb_availroom(skb) > 0) {
+			/* We have some space in skb head. Superb! */
+			copy = min_t(int, copy, skb_availroom(skb));
+			err = skb_add_data_nocache(sk, skb, &msg->msg_iter, copy);
+			if (err)
+				goto do_fault;
+		} else {
+			bool merge = true;
+			int i = skb_shinfo(skb)->nr_frags;
+			struct page_frag *pfrag = sk_page_frag(sk);
+
+			if (!sk_page_frag_refill(sk, pfrag))
+				goto wait_for_memory;
+
+			if (!skb_can_coalesce(skb, i, pfrag->page,
+					      pfrag->offset)) {
+				if (i == MAX_SKB_FRAGS || !sg) {
+					tcp_mark_push(tp, skb);
+					goto new_segment;
+				}
+				merge = false;
+			}
+
+			copy = min_t(int, copy, pfrag->size - pfrag->offset);
+
+			if (!sk_wmem_schedule(sk, copy))
+				goto wait_for_memory;
+
+			err = skb_copy_to_page_nocache(sk, &msg->msg_iter, skb,
+						       pfrag->page,
+						       pfrag->offset,
+						       copy);
+			if (err)
+				goto do_error;
+
+			/* Update the skb. */
+			if (merge) {
+				skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
+			} else {
+				skb_fill_page_desc(skb, i, pfrag->page,
+						   pfrag->offset, copy);
+				get_page(pfrag->page);
+			}
+			pfrag->offset += copy;
+		}
+
+		if (!copied)
+			TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
+
+		tp->write_seq += copy;
+		TCP_SKB_CB(skb)->end_seq += copy;
+		tcp_skb_pcount_set(skb, 0);
+
+		copied += copy;
+		if (!msg_data_left(msg)) {
+			tcp_tx_timestamp(sk, skb);
+			goto out;
+		}
+
+		if (skb->len < max || (flags & MSG_OOB) || unlikely(tp->repair))
+			continue;
+
+		if (forced_push(tp)) {
+			tcp_mark_push(tp, skb);
+			__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_PUSH);
+		} else if (skb == tcp_send_head(sk))
+			tcp_push_one(sk, mss_now);
+		continue;
+
+wait_for_sndbuf:
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+wait_for_memory:
+		if (copied)
+			tcp_push(sk, flags & ~MSG_MORE, mss_now,
+				 TCP_NAGLE_PUSH, size_goal);
+
+		if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
+			goto do_error;
+
+		mss_now = tcp_send_mss(sk, &size_goal, flags);
+	}
+
+out:
+	if (copied)
+		tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
+out_nopush:
+	release_sock(sk);
+	return copied + copied_syn;
+
+do_fault:
+	if (!skb->len) {
+		tcp_unlink_write_queue(skb, sk);
+		/* It is the one place in all of TCP, except connection
+		 * reset, where we can be unlinking the send_head.
+		 */
+		tcp_check_send_head(sk, skb);
+		sk_wmem_free_skb(sk, skb);
+	}
+
+do_error:
+	if (copied + copied_syn)
+		goto out;
+out_err:
+	err = sk_stream_error(sk, flags, err);
+	release_sock(sk);
+	return err;
+}
+EXPORT_SYMBOL(tcp_sendmsg);
+
+/*
+ *	Handle reading urgent data. BSD has very simple semantics for
+ *	this, no blocking and very strange errors 8)
+ */
+
+static int tcp_recv_urg(struct sock *sk, struct msghdr *msg, int len, int flags)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* No URG data to read. */
+	if (sock_flag(sk, SOCK_URGINLINE) || !tp->urg_data ||
+	    tp->urg_data == TCP_URG_READ)
+		return -EINVAL;	/* Yes this is right ! */
+
+	if (sk->sk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DONE))
+		return -ENOTCONN;
+
+	if (tp->urg_data & TCP_URG_VALID) {
+		int err = 0;
+		char c = tp->urg_data;
+
+		if (!(flags & MSG_PEEK))
+			tp->urg_data = TCP_URG_READ;
+
+		/* Read urgent data. */
+		msg->msg_flags |= MSG_OOB;
+
+		if (len > 0) {
+			if (!(flags & MSG_TRUNC))
+				err = memcpy_to_msg(msg, &c, 1);
+			len = 1;
+		} else
+			msg->msg_flags |= MSG_TRUNC;
+
+		return err ? -EFAULT : len;
+	}
+
+	if (sk->sk_state == TCP_CLOSE || (sk->sk_shutdown & RCV_SHUTDOWN))
+		return 0;
+
+	/* Fixed the recv(..., MSG_OOB) behaviour.  BSD docs and
+	 * the available implementations agree in this case:
+	 * this call should never block, independent of the
+	 * blocking state of the socket.
+	 * Mike <pall@rz.uni-karlsruhe.de>
+	 */
+	return -EAGAIN;
+}
+
+static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
+{
+	struct sk_buff *skb;
+	int copied = 0, err = 0;
+
+	/* XXX -- need to support SO_PEEK_OFF */
+
+	skb_queue_walk(&sk->sk_write_queue, skb) {
+		err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
+		if (err)
+			break;
+
+		copied += skb->len;
+	}
+
+	return err ?: copied;
+}
+
+/* Clean up the receive buffer for full frames taken by the user,
+ * then send an ACK if necessary.  COPIED is the number of bytes
+ * tcp_recvmsg has given to the user so far, it speeds up the
+ * calculation of whether or not we must ACK for the sake of
+ * a window update.
+ */
+static void tcp_cleanup_rbuf(struct sock *sk, int copied)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	bool time_to_ack = false;
+
+	struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
+
+	WARN(skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq),
+	     "cleanup rbuf bug: copied %X seq %X rcvnxt %X\n",
+	     tp->copied_seq, TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt);
+
+	if (inet_csk_ack_scheduled(sk)) {
+		const struct inet_connection_sock *icsk = inet_csk(sk);
+		   /* Delayed ACKs frequently hit locked sockets during bulk
+		    * receive. */
+		if (icsk->icsk_ack.blocked ||
+		    /* Once-per-two-segments ACK was not sent by tcp_input.c */
+		    tp->rcv_nxt - tp->rcv_wup > icsk->icsk_ack.rcv_mss ||
+		    /*
+		     * If this read emptied read buffer, we send ACK, if
+		     * connection is not bidirectional, user drained
+		     * receive buffer and there was a small segment
+		     * in queue.
+		     */
+		    (copied > 0 &&
+		     ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED2) ||
+		      ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED) &&
+		       !icsk->icsk_ack.pingpong)) &&
+		      !atomic_read(&sk->sk_rmem_alloc)))
+			time_to_ack = true;
+	}
+
+	/* We send an ACK if we can now advertise a non-zero window
+	 * which has been raised "significantly".
+	 *
+	 * Even if window raised up to infinity, do not send window open ACK
+	 * in states, where we will not receive more. It is useless.
+	 */
+	if (copied > 0 && !time_to_ack && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
+		__u32 rcv_window_now = tcp_receive_window(tp);
+
+		/* Optimize, __tcp_select_window() is not cheap. */
+		if (2*rcv_window_now <= tp->window_clamp) {
+			__u32 new_window = __tcp_select_window(sk);
+
+			/* Send ACK now, if this read freed lots of space
+			 * in our buffer. Certainly, new_window is new window.
+			 * We can advertise it now, if it is not less than current one.
+			 * "Lots" means "at least twice" here.
+			 */
+			if (new_window && new_window >= 2 * rcv_window_now)
+				time_to_ack = true;
+		}
+	}
+	if (time_to_ack)
+		tcp_send_ack(sk);
+}
+
+static void tcp_prequeue_process(struct sock *sk)
+{
+	struct sk_buff *skb;
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	NET_INC_STATS_USER(sock_net(sk), LINUX_MIB_TCPPREQUEUED);
+
+	/* RX process wants to run with disabled BHs, though it is not
+	 * necessary */
+	local_bh_disable();
+	while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
+		sk_backlog_rcv(sk, skb);
+	local_bh_enable();
+
+	/* Clear memory counter. */
+	tp->ucopy.memory = 0;
+}
+
+static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
+{
+	struct sk_buff *skb;
+	u32 offset;
+
+	while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
+		offset = seq - TCP_SKB_CB(skb)->seq;
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+			offset--;
+		if (offset < skb->len || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) {
+			*off = offset;
+			return skb;
+		}
+		/* This looks weird, but this can happen if TCP collapsing
+		 * splitted a fat GRO packet, while we released socket lock
+		 * in skb_splice_bits()
+		 */
+		sk_eat_skb(sk, skb);
+	}
+	return NULL;
+}
+
+/*
+ * This routine provides an alternative to tcp_recvmsg() for routines
+ * that would like to handle copying from skbuffs directly in 'sendfile'
+ * fashion.
+ * Note:
+ *	- It is assumed that the socket was locked by the caller.
+ *	- The routine does not block.
+ *	- At present, there is no support for reading OOB data
+ *	  or for 'peeking' the socket using this routine
+ *	  (although both would be easy to implement).
+ */
+int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
+		  sk_read_actor_t recv_actor)
+{
+	struct sk_buff *skb;
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 seq = tp->copied_seq;
+	u32 offset;
+	int copied = 0;
+
+	if (sk->sk_state == TCP_LISTEN)
+		return -ENOTCONN;
+	while ((skb = tcp_recv_skb(sk, seq, &offset)) != NULL) {
+		if (offset < skb->len) {
+			int used;
+			size_t len;
+
+			len = skb->len - offset;
+			/* Stop reading if we hit a patch of urgent data */
+			if (tp->urg_data) {
+				u32 urg_offset = tp->urg_seq - seq;
+				if (urg_offset < len)
+					len = urg_offset;
+				if (!len)
+					break;
+			}
+			used = recv_actor(desc, skb, offset, len);
+			if (used <= 0) {
+				if (!copied)
+					copied = used;
+				break;
+			} else if (used <= len) {
+				seq += used;
+				copied += used;
+				offset += used;
+			}
+			/* If recv_actor drops the lock (e.g. TCP splice
+			 * receive) the skb pointer might be invalid when
+			 * getting here: tcp_collapse might have deleted it
+			 * while aggregating skbs from the socket queue.
+			 */
+			skb = tcp_recv_skb(sk, seq - 1, &offset);
+			if (!skb)
+				break;
+			/* TCP coalescing might have appended data to the skb.
+			 * Try to splice more frags
+			 */
+			if (offset + 1 != skb->len)
+				continue;
+		}
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
+			sk_eat_skb(sk, skb);
+			++seq;
+			break;
+		}
+		sk_eat_skb(sk, skb);
+		if (!desc->count)
+			break;
+		tp->copied_seq = seq;
+	}
+	tp->copied_seq = seq;
+
+	tcp_rcv_space_adjust(sk);
+
+	/* Clean up data we have read: This will do ACK frames. */
+	if (copied > 0) {
+		tcp_recv_skb(sk, seq, &offset);
+		tcp_cleanup_rbuf(sk, copied);
+	}
+	return copied;
+}
+EXPORT_SYMBOL(tcp_read_sock);
+
+/*
+ *	This routine copies from a sock struct into the user buffer.
+ *
+ *	Technical note: in 2.3 we work on _locked_ socket, so that
+ *	tricks with *seq access order and skb->users are not required.
+ *	Probably, code can be easily improved even more.
+ */
+
+int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
+		int flags, int *addr_len)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int copied = 0;
+	u32 peek_seq;
+	u32 *seq;
+	unsigned long used;
+	int err;
+	int target;		/* Read at least this many bytes */
+	long timeo;
+	struct task_struct *user_recv = NULL;
+	struct sk_buff *skb;
+	u32 urg_hole = 0;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return inet_recv_error(sk, msg, len, addr_len);
+
+	if (sk_can_busy_loop(sk) && skb_queue_empty(&sk->sk_receive_queue) &&
+	    (sk->sk_state == TCP_ESTABLISHED))
+		sk_busy_loop(sk, nonblock);
+
+	lock_sock(sk);
+
+	err = -ENOTCONN;
+	if (sk->sk_state == TCP_LISTEN)
+		goto out;
+
+	timeo = sock_rcvtimeo(sk, nonblock);
+
+	/* Urgent data needs to be handled specially. */
+	if (flags & MSG_OOB)
+		goto recv_urg;
+
+	if (unlikely(tp->repair)) {
+		err = -EPERM;
+		if (!(flags & MSG_PEEK))
+			goto out;
+
+		if (tp->repair_queue == TCP_SEND_QUEUE)
+			goto recv_sndq;
+
+		err = -EINVAL;
+		if (tp->repair_queue == TCP_NO_QUEUE)
+			goto out;
+
+		/* 'common' recv queue MSG_PEEK-ing */
+	}
+
+	seq = &tp->copied_seq;
+	if (flags & MSG_PEEK) {
+		peek_seq = tp->copied_seq;
+		seq = &peek_seq;
+	}
+
+	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
+
+	do {
+		u32 offset;
+
+		/* Are we at urgent data? Stop if we have read anything or have SIGURG pending. */
+		if (tp->urg_data && tp->urg_seq == *seq) {
+			if (copied)
+				break;
+			if (signal_pending(current)) {
+				copied = timeo ? sock_intr_errno(timeo) : -EAGAIN;
+				break;
+			}
+		}
+
+		/* Next get a buffer. */
+
+		skb_queue_walk(&sk->sk_receive_queue, skb) {
+			/* Now that we have two receive queues this
+			 * shouldn't happen.
+			 */
+			if (WARN(before(*seq, TCP_SKB_CB(skb)->seq),
+				 "recvmsg bug: copied %X seq %X rcvnxt %X fl %X\n",
+				 *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
+				 flags))
+				break;
+
+			offset = *seq - TCP_SKB_CB(skb)->seq;
+			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
+				offset--;
+			if (offset < skb->len)
+				goto found_ok_skb;
+			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+				goto found_fin_ok;
+			WARN(!(flags & MSG_PEEK),
+			     "recvmsg bug 2: copied %X seq %X rcvnxt %X fl %X\n",
+			     *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt, flags);
+		}
+
+		/* Well, if we have backlog, try to process it now yet. */
+
+		if (copied >= target && !sk->sk_backlog.tail)
+			break;
+
+		if (copied) {
+			if (sk->sk_err ||
+			    sk->sk_state == TCP_CLOSE ||
+			    (sk->sk_shutdown & RCV_SHUTDOWN) ||
+			    !timeo ||
+			    signal_pending(current))
+				break;
+		} else {
+			if (sock_flag(sk, SOCK_DONE))
+				break;
+
+			if (sk->sk_err) {
+				copied = sock_error(sk);
+				break;
+			}
+
+			if (sk->sk_shutdown & RCV_SHUTDOWN)
+				break;
+
+			if (sk->sk_state == TCP_CLOSE) {
+				if (!sock_flag(sk, SOCK_DONE)) {
+					/* This occurs when user tries to read
+					 * from never connected socket.
+					 */
+					copied = -ENOTCONN;
+					break;
+				}
+				break;
+			}
+
+			if (!timeo) {
+				copied = -EAGAIN;
+				break;
+			}
+
+			if (signal_pending(current)) {
+				copied = sock_intr_errno(timeo);
+				break;
+			}
+		}
+
+		tcp_cleanup_rbuf(sk, copied);
+
+		if (!sysctl_tcp_low_latency && tp->ucopy.task == user_recv) {
+			/* Install new reader */
+			if (!user_recv && !(flags & (MSG_TRUNC | MSG_PEEK))) {
+				user_recv = current;
+				tp->ucopy.task = user_recv;
+				tp->ucopy.msg = msg;
+			}
+
+			tp->ucopy.len = len;
+
+			WARN_ON(tp->copied_seq != tp->rcv_nxt &&
+				!(flags & (MSG_PEEK | MSG_TRUNC)));
+
+			/* Ugly... If prequeue is not empty, we have to
+			 * process it before releasing socket, otherwise
+			 * order will be broken at second iteration.
+			 * More elegant solution is required!!!
+			 *
+			 * Look: we have the following (pseudo)queues:
+			 *
+			 * 1. packets in flight
+			 * 2. backlog
+			 * 3. prequeue
+			 * 4. receive_queue
+			 *
+			 * Each queue can be processed only if the next ones
+			 * are empty. At this point we have empty receive_queue.
+			 * But prequeue _can_ be not empty after 2nd iteration,
+			 * when we jumped to start of loop because backlog
+			 * processing added something to receive_queue.
+			 * We cannot release_sock(), because backlog contains
+			 * packets arrived _after_ prequeued ones.
+			 *
+			 * Shortly, algorithm is clear --- to process all
+			 * the queues in order. We could make it more directly,
+			 * requeueing packets from backlog to prequeue, if
+			 * is not empty. It is more elegant, but eats cycles,
+			 * unfortunately.
+			 */
+			if (!skb_queue_empty(&tp->ucopy.prequeue))
+				goto do_prequeue;
+
+			/* __ Set realtime policy in scheduler __ */
+		}
+
+		if (copied >= target) {
+			/* Do not sleep, just process backlog. */
+			release_sock(sk);
+			lock_sock(sk);
+		} else
+			sk_wait_data(sk, &timeo);
+
+		if (user_recv) {
+			int chunk;
+
+			/* __ Restore normal policy in scheduler __ */
+
+			if ((chunk = len - tp->ucopy.len) != 0) {
+				NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMBACKLOG, chunk);
+				len -= chunk;
+				copied += chunk;
+			}
+
+			if (tp->rcv_nxt == tp->copied_seq &&
+			    !skb_queue_empty(&tp->ucopy.prequeue)) {
+do_prequeue:
+				tcp_prequeue_process(sk);
+
+				if ((chunk = len - tp->ucopy.len) != 0) {
+					NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
+					len -= chunk;
+					copied += chunk;
+				}
+			}
+		}
+		if ((flags & MSG_PEEK) &&
+		    (peek_seq - copied - urg_hole != tp->copied_seq)) {
+			net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
+					    current->comm,
+					    task_pid_nr(current));
+			peek_seq = tp->copied_seq;
+		}
+		continue;
+
+	found_ok_skb:
+		/* Ok so how much can we use? */
+		used = skb->len - offset;
+		if (len < used)
+			used = len;
+
+		/* Do we have urgent data here? */
+		if (tp->urg_data) {
+			u32 urg_offset = tp->urg_seq - *seq;
+			if (urg_offset < used) {
+				if (!urg_offset) {
+					if (!sock_flag(sk, SOCK_URGINLINE)) {
+						++*seq;
+						urg_hole++;
+						offset++;
+						used--;
+						if (!used)
+							goto skip_copy;
+					}
+				} else
+					used = urg_offset;
+			}
+		}
+
+		if (!(flags & MSG_TRUNC)) {
+			err = skb_copy_datagram_msg(skb, offset, msg, used);
+			if (err) {
+				/* Exception. Bailout! */
+				if (!copied)
+					copied = -EFAULT;
+				break;
+			}
+		}
+
+		*seq += used;
+		copied += used;
+		len -= used;
+
+		tcp_rcv_space_adjust(sk);
+
+skip_copy:
+		if (tp->urg_data && after(tp->copied_seq, tp->urg_seq)) {
+			tp->urg_data = 0;
+			tcp_fast_path_check(sk);
+		}
+		if (used + offset < skb->len)
+			continue;
+
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+			goto found_fin_ok;
+		if (!(flags & MSG_PEEK))
+			sk_eat_skb(sk, skb);
+		continue;
+
+	found_fin_ok:
+		/* Process the FIN. */
+		++*seq;
+		if (!(flags & MSG_PEEK))
+			sk_eat_skb(sk, skb);
+		break;
+	} while (len > 0);
+
+	if (user_recv) {
+		if (!skb_queue_empty(&tp->ucopy.prequeue)) {
+			int chunk;
+
+			tp->ucopy.len = copied > 0 ? len : 0;
+
+			tcp_prequeue_process(sk);
+
+			if (copied > 0 && (chunk = len - tp->ucopy.len) != 0) {
+				NET_ADD_STATS_USER(sock_net(sk), LINUX_MIB_TCPDIRECTCOPYFROMPREQUEUE, chunk);
+				len -= chunk;
+				copied += chunk;
+			}
+		}
+
+		tp->ucopy.task = NULL;
+		tp->ucopy.len = 0;
+	}
+
+	/* According to UNIX98, msg_name/msg_namelen are ignored
+	 * on connected socket. I was just happy when found this 8) --ANK
+	 */
+
+	/* Clean up data we have read: This will do ACK frames. */
+	tcp_cleanup_rbuf(sk, copied);
+
+	release_sock(sk);
+	return copied;
+
+out:
+	release_sock(sk);
+	return err;
+
+recv_urg:
+	err = tcp_recv_urg(sk, msg, len, flags);
+	goto out;
+
+recv_sndq:
+	err = tcp_peek_sndq(sk, msg, len);
+	goto out;
+}
+EXPORT_SYMBOL(tcp_recvmsg);
+
+void tcp_set_state(struct sock *sk, int state)
+{
+	int oldstate = sk->sk_state;
+
+	switch (state) {
+	case TCP_ESTABLISHED:
+		if (oldstate != TCP_ESTABLISHED)
+			TCP_INC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
+		break;
+
+	case TCP_CLOSE:
+		if (oldstate == TCP_CLOSE_WAIT || oldstate == TCP_ESTABLISHED)
+			TCP_INC_STATS(sock_net(sk), TCP_MIB_ESTABRESETS);
+
+		sk->sk_prot->unhash(sk);
+		if (inet_csk(sk)->icsk_bind_hash &&
+		    !(sk->sk_userlocks & SOCK_BINDPORT_LOCK))
+			inet_put_port(sk);
+		/* fall through */
+	default:
+		if (oldstate == TCP_ESTABLISHED)
+			TCP_DEC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
+	}
+
+	/* Change state AFTER socket is unhashed to avoid closed
+	 * socket sitting in hash tables.
+	 */
+	sk->sk_state = state;
+
+#ifdef STATE_TRACE
+	SOCK_DEBUG(sk, "TCP sk=%p, State %s -> %s\n", sk, statename[oldstate], statename[state]);
+#endif
+}
+EXPORT_SYMBOL_GPL(tcp_set_state);
+
+/*
+ *	State processing on a close. This implements the state shift for
+ *	sending our FIN frame. Note that we only send a FIN for some
+ *	states. A shutdown() may have already sent the FIN, or we may be
+ *	closed.
+ */
+
+static const unsigned char new_state[16] = {
+  /* current state:        new state:      action:	*/
+  [0 /* (Invalid) */]	= TCP_CLOSE,
+  [TCP_ESTABLISHED]	= TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+  [TCP_SYN_SENT]	= TCP_CLOSE,
+  [TCP_SYN_RECV]	= TCP_FIN_WAIT1 | TCP_ACTION_FIN,
+  [TCP_FIN_WAIT1]	= TCP_FIN_WAIT1,
+  [TCP_FIN_WAIT2]	= TCP_FIN_WAIT2,
+  [TCP_TIME_WAIT]	= TCP_CLOSE,
+  [TCP_CLOSE]		= TCP_CLOSE,
+  [TCP_CLOSE_WAIT]	= TCP_LAST_ACK  | TCP_ACTION_FIN,
+  [TCP_LAST_ACK]	= TCP_LAST_ACK,
+  [TCP_LISTEN]		= TCP_CLOSE,
+  [TCP_CLOSING]		= TCP_CLOSING,
+  [TCP_NEW_SYN_RECV]	= TCP_CLOSE,	/* should not happen ! */
+};
+
+static int tcp_close_state(struct sock *sk)
+{
+	int next = (int)new_state[sk->sk_state];
+	int ns = next & TCP_STATE_MASK;
+
+	tcp_set_state(sk, ns);
+
+	return next & TCP_ACTION_FIN;
+}
+
+/*
+ *	Shutdown the sending side of a connection. Much like close except
+ *	that we don't receive shut down or sock_set_flag(sk, SOCK_DEAD).
+ */
+
+void tcp_shutdown(struct sock *sk, int how)
+{
+	/*	We need to grab some memory, and put together a FIN,
+	 *	and then put it into the queue to be sent.
+	 *		Tim MacKenzie(tym@dibbler.cs.monash.edu.au) 4 Dec '92.
+	 */
+	if (!(how & SEND_SHUTDOWN))
+		return;
+
+	/* If we've already sent a FIN, or it's a closed state, skip this. */
+	if ((1 << sk->sk_state) &
+	    (TCPF_ESTABLISHED | TCPF_SYN_SENT |
+	     TCPF_SYN_RECV | TCPF_CLOSE_WAIT)) {
+		/* Clear out any half completed packets.  FIN if needed. */
+		if (tcp_close_state(sk))
+			tcp_send_fin(sk);
+	}
+}
+EXPORT_SYMBOL(tcp_shutdown);
+
+bool tcp_check_oom(struct sock *sk, int shift)
+{
+	bool too_many_orphans, out_of_socket_memory;
+
+	too_many_orphans = tcp_too_many_orphans(sk, shift);
+	out_of_socket_memory = tcp_out_of_memory(sk);
+
+	if (too_many_orphans)
+		net_info_ratelimited("too many orphaned sockets\n");
+	if (out_of_socket_memory)
+		net_info_ratelimited("out of memory -- consider tuning tcp_mem\n");
+	return too_many_orphans || out_of_socket_memory;
+}
+
+void tcp_close(struct sock *sk, long timeout)
+{
+	struct sk_buff *skb;
+	int data_was_unread = 0;
+	int state;
+
+	lock_sock(sk);
+	sk->sk_shutdown = SHUTDOWN_MASK;
+
+	if (sk->sk_state == TCP_LISTEN) {
+		tcp_set_state(sk, TCP_CLOSE);
+
+		/* Special case. */
+		inet_csk_listen_stop(sk);
+
+		goto adjudge_to_death;
+	}
+
+	/*  We need to flush the recv. buffs.  We do this only on the
+	 *  descriptor close, not protocol-sourced closes, because the
+	 *  reader process may not have drained the data yet!
+	 */
+	while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		u32 len = TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq;
+
+		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
+			len--;
+		data_was_unread += len;
+		__kfree_skb(skb);
+	}
+
+	sk_mem_reclaim(sk);
+
+	/* If socket has been already reset (e.g. in tcp_reset()) - kill it. */
+	if (sk->sk_state == TCP_CLOSE)
+		goto adjudge_to_death;
+
+	/* As outlined in RFC 2525, section 2.17, we send a RST here because
+	 * data was lost. To witness the awful effects of the old behavior of
+	 * always doing a FIN, run an older 2.1.x kernel or 2.0.x, start a bulk
+	 * GET in an FTP client, suspend the process, wait for the client to
+	 * advertise a zero window, then kill -9 the FTP client, wheee...
+	 * Note: timeout is always zero in such a case.
+	 */
+	if (unlikely(tcp_sk(sk)->repair)) {
+		sk->sk_prot->disconnect(sk, 0);
+	} else if (data_was_unread) {
+		/* Unread data was tossed, zap the connection. */
+		NET_INC_STATS_USER(sock_net(sk), LINUX_MIB_TCPABORTONCLOSE);
+		tcp_set_state(sk, TCP_CLOSE);
+		tcp_send_active_reset(sk, sk->sk_allocation);
+	} else if (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime) {
+		/* Check zero linger _after_ checking for unread data. */
+		sk->sk_prot->disconnect(sk, 0);
+		NET_INC_STATS_USER(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
+	} else if (tcp_close_state(sk)) {
+		/* We FIN if the application ate all the data before
+		 * zapping the connection.
+		 */
+
+		/* RED-PEN. Formally speaking, we have broken TCP state
+		 * machine. State transitions:
+		 *
+		 * TCP_ESTABLISHED -> TCP_FIN_WAIT1
+		 * TCP_SYN_RECV	-> TCP_FIN_WAIT1 (forget it, it's impossible)
+		 * TCP_CLOSE_WAIT -> TCP_LAST_ACK
+		 *
+		 * are legal only when FIN has been sent (i.e. in window),
+		 * rather than queued out of window. Purists blame.
+		 *
+		 * F.e. "RFC state" is ESTABLISHED,
+		 * if Linux state is FIN-WAIT-1, but FIN is still not sent.
+		 *
+		 * The visible declinations are that sometimes
+		 * we enter time-wait state, when it is not required really
+		 * (harmless), do not send active resets, when they are
+		 * required by specs (TCP_ESTABLISHED, TCP_CLOSE_WAIT, when
+		 * they look as CLOSING or LAST_ACK for Linux)
+		 * Probably, I missed some more holelets.
+		 * 						--ANK
+		 * XXX (TFO) - To start off we don't support SYN+ACK+FIN
+		 * in a single packet! (May consider it later but will
+		 * probably need API support or TCP_CORK SYN-ACK until
+		 * data is written and socket is closed.)
+		 */
+		tcp_send_fin(sk);
+	}
+
+	sk_stream_wait_close(sk, timeout);
+
+adjudge_to_death:
+	state = sk->sk_state;
+	sock_hold(sk);
+	sock_orphan(sk);
+
+	/* It is the last release_sock in its life. It will remove backlog. */
+	release_sock(sk);
+
+
+	/* Now socket is owned by kernel and we acquire BH lock
+	   to finish close. No need to check for user refs.
+	 */
+	local_bh_disable();
+	bh_lock_sock(sk);
+	WARN_ON(sock_owned_by_user(sk));
+
+	percpu_counter_inc(sk->sk_prot->orphan_count);
+
+	/* Have we already been destroyed by a softirq or backlog? */
+	if (state != TCP_CLOSE && sk->sk_state == TCP_CLOSE)
+		goto out;
+
+	/*	This is a (useful) BSD violating of the RFC. There is a
+	 *	problem with TCP as specified in that the other end could
+	 *	keep a socket open forever with no application left this end.
+	 *	We use a 1 minute timeout (about the same as BSD) then kill
+	 *	our end. If they send after that then tough - BUT: long enough
+	 *	that we won't make the old 4*rto = almost no time - whoops
+	 *	reset mistake.
+	 *
+	 *	Nope, it was not mistake. It is really desired behaviour
+	 *	f.e. on http servers, when such sockets are useless, but
+	 *	consume significant resources. Let's do it with special
+	 *	linger2	option.					--ANK
+	 */
+
+	if (sk->sk_state == TCP_FIN_WAIT2) {
+		struct tcp_sock *tp = tcp_sk(sk);
+		if (tp->linger2 < 0) {
+			tcp_set_state(sk, TCP_CLOSE);
+			tcp_send_active_reset(sk, GFP_ATOMIC);
+			NET_INC_STATS_BH(sock_net(sk),
+					LINUX_MIB_TCPABORTONLINGER);
+		} else {
+			const int tmo = tcp_fin_time(sk);
+
+			if (tmo > TCP_TIMEWAIT_LEN) {
+				inet_csk_reset_keepalive_timer(sk,
+						tmo - TCP_TIMEWAIT_LEN);
+			} else {
+				tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
+				goto out;
+			}
+		}
+	}
+	if (sk->sk_state != TCP_CLOSE) {
+		sk_mem_reclaim(sk);
+		if (tcp_check_oom(sk, 0)) {
+			tcp_set_state(sk, TCP_CLOSE);
+			tcp_send_active_reset(sk, GFP_ATOMIC);
+			NET_INC_STATS_BH(sock_net(sk),
+					LINUX_MIB_TCPABORTONMEMORY);
+		}
+	}
+
+	if (sk->sk_state == TCP_CLOSE) {
+		struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+		/* We could get here with a non-NULL req if the socket is
+		 * aborted (e.g., closed with unread data) before 3WHS
+		 * finishes.
+		 */
+		if (req)
+			reqsk_fastopen_remove(sk, req, false);
+		inet_csk_destroy_sock(sk);
+	}
+	/* Otherwise, socket is reprieved until protocol close. */
+
+out:
+	bh_unlock_sock(sk);
+	local_bh_enable();
+	sock_put(sk);
+}
+EXPORT_SYMBOL(tcp_close);
+
+/* These states need RST on ABORT according to RFC793 */
+
+static inline bool tcp_need_reset(int state)
+{
+	return (1 << state) &
+	       (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_FIN_WAIT1 |
+		TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
+}
+
+int tcp_disconnect(struct sock *sk, int flags)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	int err = 0;
+	int old_state = sk->sk_state;
+
+	if (old_state != TCP_CLOSE)
+		tcp_set_state(sk, TCP_CLOSE);
+
+	/* ABORT function of RFC793 */
+	if (old_state == TCP_LISTEN) {
+		inet_csk_listen_stop(sk);
+	} else if (unlikely(tp->repair)) {
+		sk->sk_err = ECONNABORTED;
+	} else if (tcp_need_reset(old_state) ||
+		   (tp->snd_nxt != tp->write_seq &&
+		    (1 << old_state) & (TCPF_CLOSING | TCPF_LAST_ACK))) {
+		/* The last check adjusts for discrepancy of Linux wrt. RFC
+		 * states
+		 */
+		tcp_send_active_reset(sk, gfp_any());
+		sk->sk_err = ECONNRESET;
+	} else if (old_state == TCP_SYN_SENT)
+		sk->sk_err = ECONNRESET;
+
+	tcp_clear_xmit_timers(sk);
+	__skb_queue_purge(&sk->sk_receive_queue);
+	tcp_write_queue_purge(sk);
+	__skb_queue_purge(&tp->out_of_order_queue);
+
+	inet->inet_dport = 0;
+
+	if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
+		inet_reset_saddr(sk);
+
+	sk->sk_shutdown = 0;
+	sock_reset_flag(sk, SOCK_DONE);
+	tp->srtt_us = 0;
+	if ((tp->write_seq += tp->max_window + 2) == 0)
+		tp->write_seq = 1;
+	icsk->icsk_backoff = 0;
+	tp->snd_cwnd = 2;
+	icsk->icsk_probes_out = 0;
+	tp->packets_out = 0;
+	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
+	tp->snd_cwnd_cnt = 0;
+	tp->window_clamp = 0;
+	tcp_set_ca_state(sk, TCP_CA_Open);
+	tcp_clear_retrans(tp);
+	inet_csk_delack_init(sk);
+	tcp_init_send_head(sk);
+	memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
+	__sk_dst_reset(sk);
+
+	WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
+
+	sk->sk_error_report(sk);
+	return err;
+}
+EXPORT_SYMBOL(tcp_disconnect);
+
+void tcp_sock_destruct(struct sock *sk)
+{
+	inet_sock_destruct(sk);
+
+	kfree(inet_csk(sk)->icsk_accept_queue.fastopenq);
+}
+
+static inline bool tcp_can_repair_sock(const struct sock *sk)
+{
+	return ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN) &&
+		((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_ESTABLISHED));
+}
+
+static int tcp_repair_options_est(struct tcp_sock *tp,
+		struct tcp_repair_opt __user *optbuf, unsigned int len)
+{
+	struct tcp_repair_opt opt;
+
+	while (len >= sizeof(opt)) {
+		if (copy_from_user(&opt, optbuf, sizeof(opt)))
+			return -EFAULT;
+
+		optbuf++;
+		len -= sizeof(opt);
+
+		switch (opt.opt_code) {
+		case TCPOPT_MSS:
+			tp->rx_opt.mss_clamp = opt.opt_val;
+			break;
+		case TCPOPT_WINDOW:
+			{
+				u16 snd_wscale = opt.opt_val & 0xFFFF;
+				u16 rcv_wscale = opt.opt_val >> 16;
+
+				if (snd_wscale > 14 || rcv_wscale > 14)
+					return -EFBIG;
+
+				tp->rx_opt.snd_wscale = snd_wscale;
+				tp->rx_opt.rcv_wscale = rcv_wscale;
+				tp->rx_opt.wscale_ok = 1;
+			}
+			break;
+		case TCPOPT_SACK_PERM:
+			if (opt.opt_val != 0)
+				return -EINVAL;
+
+			tp->rx_opt.sack_ok |= TCP_SACK_SEEN;
+			if (sysctl_tcp_fack)
+				tcp_enable_fack(tp);
+			break;
+		case TCPOPT_TIMESTAMP:
+			if (opt.opt_val != 0)
+				return -EINVAL;
+
+			tp->rx_opt.tstamp_ok = 1;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_TCP_STEALTH
+int tcp_stealth_integrity(__be16 *hash, u8 *secret, u8 *payload, int len)
+{
+	struct scatterlist sg[2];
+	struct crypto_hash *tfm;
+	struct hash_desc desc;
+	__be16 h[MD5_DIGEST_WORDS * 2];
+	int i;
+	int err = 0;
+
+	tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(tfm)) {
+		err = -PTR_ERR(tfm);
+		goto out;
+	}
+	desc.tfm = tfm;
+	desc.flags = 0;
+
+	sg_init_table(sg, 2);
+	sg_set_buf(&sg[0], secret, MD5_MESSAGE_BYTES);
+	sg_set_buf(&sg[1], payload, len);
+
+	if (crypto_hash_digest(&desc, sg, MD5_MESSAGE_BYTES + len, (u8 *)h)) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	*hash = be16_to_cpu(h[0]);
+	for (i = 1; i < MD5_DIGEST_WORDS * 2; i++)
+		*hash ^= be16_to_cpu(h[i]);
+
+out:
+	crypto_free_hash(tfm);
+	return err;
+}
+#endif
+
+/*
+ *	Socket option code for TCP.
+ */
+static int do_tcp_setsockopt(struct sock *sk, int level,
+		int optname, char __user *optval, unsigned int optlen)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	int val;
+	int err = 0;
+
+	/* These are data/string values, all the others are ints */
+	switch (optname) {
+	case TCP_CONGESTION: {
+		char name[TCP_CA_NAME_MAX];
+
+		if (optlen < 1)
+			return -EINVAL;
+
+		val = strncpy_from_user(name, optval,
+					min_t(long, TCP_CA_NAME_MAX-1, optlen));
+		if (val < 0)
+			return -EFAULT;
+		name[val] = 0;
+
+		lock_sock(sk);
+		err = tcp_set_congestion_control(sk, name);
+		release_sock(sk);
+		return err;
+	}
+#ifdef CONFIG_TCP_STEALTH
+	case TCP_STEALTH: {
+		u8 secret[MD5_MESSAGE_BYTES] = { 0 };
+
+		val = copy_from_user(secret, optval,
+				     min_t(unsigned int, optlen,
+					   MD5_MESSAGE_BYTES));
+		if (val != 0)
+			return -EFAULT;
+
+		lock_sock(sk);
+		memcpy(tp->stealth.secret, secret, MD5_MESSAGE_BYTES);
+		tp->stealth.mode = TCP_STEALTH_MODE_AUTH;
+		tp->stealth.mstamp.v64 = 0;
+		tp->stealth.saw_tsval = false;
+		release_sock(sk);
+		return err;
+	}
+	case TCP_STEALTH_INTEGRITY: {
+		u8 *payload;
+
+		lock_sock(sk);
+
+		if (!(tp->stealth.mode & TCP_STEALTH_MODE_AUTH)) {
+			err = -EOPNOTSUPP;
+			goto stealth_integrity_out_1;
+		}
+
+		if (optlen < 1 || optlen > USHRT_MAX) {
+			err = -EINVAL;
+			goto stealth_integrity_out_1;
+		}
+
+		payload = vmalloc(optlen);
+		if (!payload) {
+			err = -ENOMEM;
+			goto stealth_integrity_out_1;
+		}
+
+		val = copy_from_user(payload, optval, optlen);
+		if (val != 0) {
+			err = -EFAULT;
+			goto stealth_integrity_out_2;
+		}
+
+		err = tcp_stealth_integrity(&tp->stealth.integrity_hash,
+					    tp->stealth.secret, payload,
+					    optlen);
+		if (err)
+			goto stealth_integrity_out_2;
+
+		tp->stealth.mode |= TCP_STEALTH_MODE_INTEGRITY;
+
+stealth_integrity_out_2:
+		vfree(payload);
+stealth_integrity_out_1:
+		release_sock(sk);
+		return err;
+	}
+#endif
+	default:
+		/* fallthru */
+		break;
+	}
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (get_user(val, (int __user *)optval))
+		return -EFAULT;
+
+	lock_sock(sk);
+
+	switch (optname) {
+	case TCP_MAXSEG:
+		/* Values greater than interface MTU won't take effect. However
+		 * at the point when this call is done we typically don't yet
+		 * know which interface is going to be used */
+		if (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW) {
+			err = -EINVAL;
+			break;
+		}
+		tp->rx_opt.user_mss = val;
+		break;
+
+	case TCP_NODELAY:
+		if (val) {
+			/* TCP_NODELAY is weaker than TCP_CORK, so that
+			 * this option on corked socket is remembered, but
+			 * it is not activated until cork is cleared.
+			 *
+			 * However, when TCP_NODELAY is set we make
+			 * an explicit push, which overrides even TCP_CORK
+			 * for currently queued segments.
+			 */
+			tp->nonagle |= TCP_NAGLE_OFF|TCP_NAGLE_PUSH;
+			tcp_push_pending_frames(sk);
+		} else {
+			tp->nonagle &= ~TCP_NAGLE_OFF;
+		}
+		break;
+
+	case TCP_THIN_LINEAR_TIMEOUTS:
+		if (val < 0 || val > 1)
+			err = -EINVAL;
+		else
+			tp->thin_lto = val;
+		break;
+
+	case TCP_THIN_DUPACK:
+		if (val < 0 || val > 1)
+			err = -EINVAL;
+		else {
+			tp->thin_dupack = val;
+			if (tp->thin_dupack)
+				tcp_disable_early_retrans(tp);
+		}
+		break;
+
+	case TCP_REPAIR:
+		if (!tcp_can_repair_sock(sk))
+			err = -EPERM;
+		else if (val == 1) {
+			tp->repair = 1;
+			sk->sk_reuse = SK_FORCE_REUSE;
+			tp->repair_queue = TCP_NO_QUEUE;
+		} else if (val == 0) {
+			tp->repair = 0;
+			sk->sk_reuse = SK_NO_REUSE;
+			tcp_send_window_probe(sk);
+		} else
+			err = -EINVAL;
+
+		break;
+
+	case TCP_REPAIR_QUEUE:
+		if (!tp->repair)
+			err = -EPERM;
+		else if (val < TCP_QUEUES_NR)
+			tp->repair_queue = val;
+		else
+			err = -EINVAL;
+		break;
+
+	case TCP_QUEUE_SEQ:
+		if (sk->sk_state != TCP_CLOSE)
+			err = -EPERM;
+		else if (tp->repair_queue == TCP_SEND_QUEUE)
+			tp->write_seq = val;
+		else if (tp->repair_queue == TCP_RECV_QUEUE)
+			tp->rcv_nxt = val;
+		else
+			err = -EINVAL;
+		break;
+
+	case TCP_REPAIR_OPTIONS:
+		if (!tp->repair)
+			err = -EINVAL;
+		else if (sk->sk_state == TCP_ESTABLISHED)
+			err = tcp_repair_options_est(tp,
+					(struct tcp_repair_opt __user *)optval,
+					optlen);
+		else
+			err = -EPERM;
+		break;
+
+	case TCP_CORK:
+		/* When set indicates to always queue non-full frames.
+		 * Later the user clears this option and we transmit
+		 * any pending partial frames in the queue.  This is
+		 * meant to be used alongside sendfile() to get properly
+		 * filled frames when the user (for example) must write
+		 * out headers with a write() call first and then use
+		 * sendfile to send out the data parts.
+		 *
+		 * TCP_CORK can be set together with TCP_NODELAY and it is
+		 * stronger than TCP_NODELAY.
+		 */
+		if (val) {
+			tp->nonagle |= TCP_NAGLE_CORK;
+		} else {
+			tp->nonagle &= ~TCP_NAGLE_CORK;
+			if (tp->nonagle&TCP_NAGLE_OFF)
+				tp->nonagle |= TCP_NAGLE_PUSH;
+			tcp_push_pending_frames(sk);
+		}
+		break;
+
+	case TCP_KEEPIDLE:
+		if (val < 1 || val > MAX_TCP_KEEPIDLE)
+			err = -EINVAL;
+		else {
+			tp->keepalive_time = val * HZ;
+			if (sock_flag(sk, SOCK_KEEPOPEN) &&
+			    !((1 << sk->sk_state) &
+			      (TCPF_CLOSE | TCPF_LISTEN))) {
+				u32 elapsed = keepalive_time_elapsed(tp);
+				if (tp->keepalive_time > elapsed)
+					elapsed = tp->keepalive_time - elapsed;
+				else
+					elapsed = 0;
+				inet_csk_reset_keepalive_timer(sk, elapsed);
+			}
+		}
+		break;
+	case TCP_KEEPINTVL:
+		if (val < 1 || val > MAX_TCP_KEEPINTVL)
+			err = -EINVAL;
+		else
+			tp->keepalive_intvl = val * HZ;
+		break;
+	case TCP_KEEPCNT:
+		if (val < 1 || val > MAX_TCP_KEEPCNT)
+			err = -EINVAL;
+		else
+			tp->keepalive_probes = val;
+		break;
+	case TCP_SYNCNT:
+		if (val < 1 || val > MAX_TCP_SYNCNT)
+			err = -EINVAL;
+		else
+			icsk->icsk_syn_retries = val;
+		break;
+
+	case TCP_LINGER2:
+		if (val < 0)
+			tp->linger2 = -1;
+		else if (val > sysctl_tcp_fin_timeout / HZ)
+			tp->linger2 = 0;
+		else
+			tp->linger2 = val * HZ;
+		break;
+
+	case TCP_DEFER_ACCEPT:
+		/* Translate value in seconds to number of retransmits */
+		icsk->icsk_accept_queue.rskq_defer_accept =
+			secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ,
+					TCP_RTO_MAX / HZ);
+		break;
+
+	case TCP_WINDOW_CLAMP:
+		if (!val) {
+			if (sk->sk_state != TCP_CLOSE) {
+				err = -EINVAL;
+				break;
+			}
+			tp->window_clamp = 0;
+		} else
+			tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
+						SOCK_MIN_RCVBUF / 2 : val;
+		break;
+
+	case TCP_QUICKACK:
+		if (!val) {
+			icsk->icsk_ack.pingpong = 1;
+		} else {
+			icsk->icsk_ack.pingpong = 0;
+			if ((1 << sk->sk_state) &
+			    (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT) &&
+			    inet_csk_ack_scheduled(sk)) {
+				icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
+				tcp_cleanup_rbuf(sk, 1);
+				if (!(val & 1))
+					icsk->icsk_ack.pingpong = 1;
+			}
+		}
+		break;
+
+#ifdef CONFIG_TCP_MD5SIG
+	case TCP_MD5SIG:
+		/* Read the IP->Key mappings from userspace */
+		err = tp->af_specific->md5_parse(sk, optval, optlen);
+		break;
+#endif
+	case TCP_USER_TIMEOUT:
+		/* Cap the max time in ms TCP will retry or probe the window
+		 * before giving up and aborting (ETIMEDOUT) a connection.
+		 */
+		if (val < 0)
+			err = -EINVAL;
+		else
+			icsk->icsk_user_timeout = msecs_to_jiffies(val);
+		break;
+
+	case TCP_FASTOPEN:
+		if (val >= 0 && ((1 << sk->sk_state) & (TCPF_CLOSE |
+		    TCPF_LISTEN))) {
+			tcp_fastopen_init_key_once(true);
+
+			err = fastopen_init_queue(sk, val);
+		} else {
+			err = -EINVAL;
+		}
+		break;
+	case TCP_TIMESTAMP:
+		if (!tp->repair)
+			err = -EPERM;
+		else
+			tp->tsoffset = val - tcp_time_stamp;
+		break;
+	case TCP_NOTSENT_LOWAT:
+		tp->notsent_lowat = val;
+		sk->sk_write_space(sk);
+		break;
+#ifdef CONFIG_TCP_STEALTH
+	case TCP_STEALTH_INTEGRITY_LEN:
+		if (!(tp->stealth.mode & TCP_STEALTH_MODE_AUTH)) {
+			err = -EOPNOTSUPP;
+		} else if (val < 1 || val > USHRT_MAX) {
+			err = -EINVAL;
+		} else {
+			tp->stealth.integrity_len = val;
+			tp->stealth.mode |= TCP_STEALTH_MODE_INTEGRITY_LEN;
+		}
+		break;
+#endif
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+	release_sock(sk);
+	return err;
+}
+
+int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
+		   unsigned int optlen)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (level != SOL_TCP)
+		return icsk->icsk_af_ops->setsockopt(sk, level, optname,
+						     optval, optlen);
+	return do_tcp_setsockopt(sk, level, optname, optval, optlen);
+}
+EXPORT_SYMBOL(tcp_setsockopt);
+
+#ifdef CONFIG_COMPAT
+int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
+			  char __user *optval, unsigned int optlen)
+{
+	if (level != SOL_TCP)
+		return inet_csk_compat_setsockopt(sk, level, optname,
+						  optval, optlen);
+	return do_tcp_setsockopt(sk, level, optname, optval, optlen);
+}
+EXPORT_SYMBOL(compat_tcp_setsockopt);
+#endif
+
+/* Return information about state of tcp endpoint in API format. */
+void tcp_get_info(struct sock *sk, struct tcp_info *info)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+	u32 now = tcp_time_stamp;
+	unsigned int start;
+	u32 rate;
+
+	memset(info, 0, sizeof(*info));
+
+	info->tcpi_state = sk->sk_state;
+	info->tcpi_ca_state = icsk->icsk_ca_state;
+	info->tcpi_retransmits = icsk->icsk_retransmits;
+	info->tcpi_probes = icsk->icsk_probes_out;
+	info->tcpi_backoff = icsk->icsk_backoff;
+
+	if (tp->rx_opt.tstamp_ok)
+		info->tcpi_options |= TCPI_OPT_TIMESTAMPS;
+	if (tcp_is_sack(tp))
+		info->tcpi_options |= TCPI_OPT_SACK;
+	if (tp->rx_opt.wscale_ok) {
+		info->tcpi_options |= TCPI_OPT_WSCALE;
+		info->tcpi_snd_wscale = tp->rx_opt.snd_wscale;
+		info->tcpi_rcv_wscale = tp->rx_opt.rcv_wscale;
+	}
+
+	if (tp->ecn_flags & TCP_ECN_OK)
+		info->tcpi_options |= TCPI_OPT_ECN;
+	if (tp->ecn_flags & TCP_ECN_SEEN)
+		info->tcpi_options |= TCPI_OPT_ECN_SEEN;
+	if (tp->syn_data_acked)
+		info->tcpi_options |= TCPI_OPT_SYN_DATA;
+
+	info->tcpi_rto = jiffies_to_usecs(icsk->icsk_rto);
+	info->tcpi_ato = jiffies_to_usecs(icsk->icsk_ack.ato);
+	info->tcpi_snd_mss = tp->mss_cache;
+	info->tcpi_rcv_mss = icsk->icsk_ack.rcv_mss;
+
+	if (sk->sk_state == TCP_LISTEN) {
+		info->tcpi_unacked = sk->sk_ack_backlog;
+		info->tcpi_sacked = sk->sk_max_ack_backlog;
+	} else {
+		info->tcpi_unacked = tp->packets_out;
+		info->tcpi_sacked = tp->sacked_out;
+	}
+	info->tcpi_lost = tp->lost_out;
+	info->tcpi_retrans = tp->retrans_out;
+	info->tcpi_fackets = tp->fackets_out;
+
+	info->tcpi_last_data_sent = jiffies_to_msecs(now - tp->lsndtime);
+	info->tcpi_last_data_recv = jiffies_to_msecs(now - icsk->icsk_ack.lrcvtime);
+	info->tcpi_last_ack_recv = jiffies_to_msecs(now - tp->rcv_tstamp);
+
+	info->tcpi_pmtu = icsk->icsk_pmtu_cookie;
+	info->tcpi_rcv_ssthresh = tp->rcv_ssthresh;
+	info->tcpi_rtt = tp->srtt_us >> 3;
+	info->tcpi_rttvar = tp->mdev_us >> 2;
+	info->tcpi_snd_ssthresh = tp->snd_ssthresh;
+	info->tcpi_snd_cwnd = tp->snd_cwnd;
+	info->tcpi_advmss = tp->advmss;
+	info->tcpi_reordering = tp->reordering;
+
+	info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3;
+	info->tcpi_rcv_space = tp->rcvq_space.space;
+
+	info->tcpi_total_retrans = tp->total_retrans;
+
+	rate = READ_ONCE(sk->sk_pacing_rate);
+	info->tcpi_pacing_rate = rate != ~0U ? rate : ~0ULL;
+
+	rate = READ_ONCE(sk->sk_max_pacing_rate);
+	info->tcpi_max_pacing_rate = rate != ~0U ? rate : ~0ULL;
+
+	do {
+		start = u64_stats_fetch_begin_irq(&tp->syncp);
+		info->tcpi_bytes_acked = tp->bytes_acked;
+		info->tcpi_bytes_received = tp->bytes_received;
+	} while (u64_stats_fetch_retry_irq(&tp->syncp, start));
+}
+EXPORT_SYMBOL_GPL(tcp_get_info);
+
+static int do_tcp_getsockopt(struct sock *sk, int level,
+		int optname, char __user *optval, int __user *optlen)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	int val, len;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	len = min_t(unsigned int, len, sizeof(int));
+
+	if (len < 0)
+		return -EINVAL;
+
+	switch (optname) {
+	case TCP_MAXSEG:
+		val = tp->mss_cache;
+		if (!val && ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
+			val = tp->rx_opt.user_mss;
+		if (tp->repair)
+			val = tp->rx_opt.mss_clamp;
+		break;
+	case TCP_NODELAY:
+		val = !!(tp->nonagle&TCP_NAGLE_OFF);
+		break;
+	case TCP_CORK:
+		val = !!(tp->nonagle&TCP_NAGLE_CORK);
+		break;
+	case TCP_KEEPIDLE:
+		val = keepalive_time_when(tp) / HZ;
+		break;
+	case TCP_KEEPINTVL:
+		val = keepalive_intvl_when(tp) / HZ;
+		break;
+	case TCP_KEEPCNT:
+		val = keepalive_probes(tp);
+		break;
+	case TCP_SYNCNT:
+		val = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
+		break;
+	case TCP_LINGER2:
+		val = tp->linger2;
+		if (val >= 0)
+			val = (val ? : sysctl_tcp_fin_timeout) / HZ;
+		break;
+	case TCP_DEFER_ACCEPT:
+		val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,
+				      TCP_TIMEOUT_INIT / HZ, TCP_RTO_MAX / HZ);
+		break;
+	case TCP_WINDOW_CLAMP:
+		val = tp->window_clamp;
+		break;
+	case TCP_INFO: {
+		struct tcp_info info;
+
+		if (get_user(len, optlen))
+			return -EFAULT;
+
+		tcp_get_info(sk, &info);
+
+		len = min_t(unsigned int, len, sizeof(info));
+		if (put_user(len, optlen))
+			return -EFAULT;
+		if (copy_to_user(optval, &info, len))
+			return -EFAULT;
+		return 0;
+	}
+	case TCP_CC_INFO: {
+		const struct tcp_congestion_ops *ca_ops;
+		union tcp_cc_info info;
+		size_t sz = 0;
+		int attr;
+
+		if (get_user(len, optlen))
+			return -EFAULT;
+
+		ca_ops = icsk->icsk_ca_ops;
+		if (ca_ops && ca_ops->get_info)
+			sz = ca_ops->get_info(sk, ~0U, &attr, &info);
+
+		len = min_t(unsigned int, len, sz);
+		if (put_user(len, optlen))
+			return -EFAULT;
+		if (copy_to_user(optval, &info, len))
+			return -EFAULT;
+		return 0;
+	}
+	case TCP_QUICKACK:
+		val = !icsk->icsk_ack.pingpong;
+		break;
+
+	case TCP_CONGESTION:
+		if (get_user(len, optlen))
+			return -EFAULT;
+		len = min_t(unsigned int, len, TCP_CA_NAME_MAX);
+		if (put_user(len, optlen))
+			return -EFAULT;
+		if (copy_to_user(optval, icsk->icsk_ca_ops->name, len))
+			return -EFAULT;
+		return 0;
+
+	case TCP_THIN_LINEAR_TIMEOUTS:
+		val = tp->thin_lto;
+		break;
+	case TCP_THIN_DUPACK:
+		val = tp->thin_dupack;
+		break;
+
+	case TCP_REPAIR:
+		val = tp->repair;
+		break;
+
+	case TCP_REPAIR_QUEUE:
+		if (tp->repair)
+			val = tp->repair_queue;
+		else
+			return -EINVAL;
+		break;
+
+	case TCP_QUEUE_SEQ:
+		if (tp->repair_queue == TCP_SEND_QUEUE)
+			val = tp->write_seq;
+		else if (tp->repair_queue == TCP_RECV_QUEUE)
+			val = tp->rcv_nxt;
+		else
+			return -EINVAL;
+		break;
+
+	case TCP_USER_TIMEOUT:
+		val = jiffies_to_msecs(icsk->icsk_user_timeout);
+		break;
+
+	case TCP_FASTOPEN:
+		if (icsk->icsk_accept_queue.fastopenq)
+			val = icsk->icsk_accept_queue.fastopenq->max_qlen;
+		else
+			val = 0;
+		break;
+
+	case TCP_TIMESTAMP:
+		val = tcp_time_stamp + tp->tsoffset;
+		break;
+	case TCP_NOTSENT_LOWAT:
+		val = tp->notsent_lowat;
+		break;
+	default:
+		return -ENOPROTOOPT;
+	}
+
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+	return 0;
+}
+
+int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
+		   int __user *optlen)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	if (level != SOL_TCP)
+		return icsk->icsk_af_ops->getsockopt(sk, level, optname,
+						     optval, optlen);
+	return do_tcp_getsockopt(sk, level, optname, optval, optlen);
+}
+EXPORT_SYMBOL(tcp_getsockopt);
+
+#ifdef CONFIG_COMPAT
+int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
+			  char __user *optval, int __user *optlen)
+{
+	if (level != SOL_TCP)
+		return inet_csk_compat_getsockopt(sk, level, optname,
+						  optval, optlen);
+	return do_tcp_getsockopt(sk, level, optname, optval, optlen);
+}
+EXPORT_SYMBOL(compat_tcp_getsockopt);
+#endif
+
+#ifdef CONFIG_TCP_MD5SIG
+static DEFINE_PER_CPU(struct tcp_md5sig_pool, tcp_md5sig_pool);
+static DEFINE_MUTEX(tcp_md5sig_mutex);
+static bool tcp_md5sig_pool_populated = false;
+
+static void __tcp_alloc_md5sig_pool(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		if (!per_cpu(tcp_md5sig_pool, cpu).md5_desc.tfm) {
+			struct crypto_hash *hash;
+
+			hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
+			if (IS_ERR_OR_NULL(hash))
+				return;
+			per_cpu(tcp_md5sig_pool, cpu).md5_desc.tfm = hash;
+		}
+	}
+	/* before setting tcp_md5sig_pool_populated, we must commit all writes
+	 * to memory. See smp_rmb() in tcp_get_md5sig_pool()
+	 */
+	smp_wmb();
+	tcp_md5sig_pool_populated = true;
+}
+
+bool tcp_alloc_md5sig_pool(void)
+{
+	if (unlikely(!tcp_md5sig_pool_populated)) {
+		mutex_lock(&tcp_md5sig_mutex);
+
+		if (!tcp_md5sig_pool_populated)
+			__tcp_alloc_md5sig_pool();
+
+		mutex_unlock(&tcp_md5sig_mutex);
+	}
+	return tcp_md5sig_pool_populated;
+}
+EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
+
+
+/**
+ *	tcp_get_md5sig_pool - get md5sig_pool for this user
+ *
+ *	We use percpu structure, so if we succeed, we exit with preemption
+ *	and BH disabled, to make sure another thread or softirq handling
+ *	wont try to get same context.
+ */
+struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
+{
+	local_bh_disable();
+
+	if (tcp_md5sig_pool_populated) {
+		/* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */
+		smp_rmb();
+		return this_cpu_ptr(&tcp_md5sig_pool);
+	}
+	local_bh_enable();
+	return NULL;
+}
+EXPORT_SYMBOL(tcp_get_md5sig_pool);
+
+int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
+			const struct tcphdr *th)
+{
+	struct scatterlist sg;
+	struct tcphdr hdr;
+	int err;
+
+	/* We are not allowed to change tcphdr, make a local copy */
+	memcpy(&hdr, th, sizeof(hdr));
+	hdr.check = 0;
+
+	/* options aren't included in the hash */
+	sg_init_one(&sg, &hdr, sizeof(hdr));
+	err = crypto_hash_update(&hp->md5_desc, &sg, sizeof(hdr));
+	return err;
+}
+EXPORT_SYMBOL(tcp_md5_hash_header);
+
+int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
+			  const struct sk_buff *skb, unsigned int header_len)
+{
+	struct scatterlist sg;
+	const struct tcphdr *tp = tcp_hdr(skb);
+	struct hash_desc *desc = &hp->md5_desc;
+	unsigned int i;
+	const unsigned int head_data_len = skb_headlen(skb) > header_len ?
+					   skb_headlen(skb) - header_len : 0;
+	const struct skb_shared_info *shi = skb_shinfo(skb);
+	struct sk_buff *frag_iter;
+
+	sg_init_table(&sg, 1);
+
+	sg_set_buf(&sg, ((u8 *) tp) + header_len, head_data_len);
+	if (crypto_hash_update(desc, &sg, head_data_len))
+		return 1;
+
+	for (i = 0; i < shi->nr_frags; ++i) {
+		const struct skb_frag_struct *f = &shi->frags[i];
+		unsigned int offset = f->page_offset;
+		struct page *page = skb_frag_page(f) + (offset >> PAGE_SHIFT);
+
+		sg_set_page(&sg, page, skb_frag_size(f),
+			    offset_in_page(offset));
+		if (crypto_hash_update(desc, &sg, skb_frag_size(f)))
+			return 1;
+	}
+
+	skb_walk_frags(skb, frag_iter)
+		if (tcp_md5_hash_skb_data(hp, frag_iter, 0))
+			return 1;
+
+	return 0;
+}
+EXPORT_SYMBOL(tcp_md5_hash_skb_data);
+
+int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key)
+{
+	struct scatterlist sg;
+
+	sg_init_one(&sg, key->key, key->keylen);
+	return crypto_hash_update(&hp->md5_desc, &sg, key->keylen);
+}
+EXPORT_SYMBOL(tcp_md5_hash_key);
+
+#endif
+
+void tcp_done(struct sock *sk)
+{
+	struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+
+	if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
+		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
+
+	tcp_set_state(sk, TCP_CLOSE);
+	tcp_clear_xmit_timers(sk);
+	if (req)
+		reqsk_fastopen_remove(sk, req, false);
+
+	sk->sk_shutdown = SHUTDOWN_MASK;
+
+	if (!sock_flag(sk, SOCK_DEAD))
+		sk->sk_state_change(sk);
+	else
+		inet_csk_destroy_sock(sk);
+}
+EXPORT_SYMBOL_GPL(tcp_done);
+
+extern struct tcp_congestion_ops tcp_reno;
+
+static __initdata unsigned long thash_entries;
+static int __init set_thash_entries(char *str)
+{
+	ssize_t ret;
+
+	if (!str)
+		return 0;
+
+	ret = kstrtoul(str, 0, &thash_entries);
+	if (ret)
+		return 0;
+
+	return 1;
+}
+__setup("thash_entries=", set_thash_entries);
+
+static void __init tcp_init_mem(void)
+{
+	unsigned long limit = nr_free_buffer_pages() / 8;
+	limit = max(limit, 128UL);
+	sysctl_tcp_mem[0] = limit / 4 * 3;
+	sysctl_tcp_mem[1] = limit;
+	sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
+}
+
+void __init tcp_init(void)
+{
+	unsigned long limit;
+	int max_rshare, max_wshare, cnt;
+	unsigned int i;
+
+	sock_skb_cb_check_size(sizeof(struct tcp_skb_cb));
+
+	percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL);
+	percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL);
+	tcp_hashinfo.bind_bucket_cachep =
+		kmem_cache_create("tcp_bind_bucket",
+				  sizeof(struct inet_bind_bucket), 0,
+				  SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+
+	/* Size and allocate the main established and bind bucket
+	 * hash tables.
+	 *
+	 * The methodology is similar to that of the buffer cache.
+	 */
+	tcp_hashinfo.ehash =
+		alloc_large_system_hash("TCP established",
+					sizeof(struct inet_ehash_bucket),
+					thash_entries,
+					17, /* one slot per 128 KB of memory */
+					0,
+					NULL,
+					&tcp_hashinfo.ehash_mask,
+					0,
+					thash_entries ? 0 : 512 * 1024);
+	for (i = 0; i <= tcp_hashinfo.ehash_mask; i++)
+		INIT_HLIST_NULLS_HEAD(&tcp_hashinfo.ehash[i].chain, i);
+
+	if (inet_ehash_locks_alloc(&tcp_hashinfo))
+		panic("TCP: failed to alloc ehash_locks");
+	tcp_hashinfo.bhash =
+		alloc_large_system_hash("TCP bind",
+					sizeof(struct inet_bind_hashbucket),
+					tcp_hashinfo.ehash_mask + 1,
+					17, /* one slot per 128 KB of memory */
+					0,
+					&tcp_hashinfo.bhash_size,
+					NULL,
+					0,
+					64 * 1024);
+	tcp_hashinfo.bhash_size = 1U << tcp_hashinfo.bhash_size;
+	for (i = 0; i < tcp_hashinfo.bhash_size; i++) {
+		spin_lock_init(&tcp_hashinfo.bhash[i].lock);
+		INIT_HLIST_HEAD(&tcp_hashinfo.bhash[i].chain);
+	}
+
+
+	cnt = tcp_hashinfo.ehash_mask + 1;
+
+	tcp_death_row.sysctl_max_tw_buckets = cnt / 2;
+	sysctl_tcp_max_orphans = cnt / 2;
+	sysctl_max_syn_backlog = max(128, cnt / 256);
+
+	tcp_init_mem();
+	/* Set per-socket limits to no more than 1/128 the pressure threshold */
+	limit = nr_free_buffer_pages() << (PAGE_SHIFT - 7);
+	max_wshare = min(4UL*1024*1024, limit);
+	max_rshare = min(6UL*1024*1024, limit);
+
+	sysctl_tcp_wmem[0] = SK_MEM_QUANTUM;
+	sysctl_tcp_wmem[1] = 16*1024;
+	sysctl_tcp_wmem[2] = max(64*1024, max_wshare);
+
+	sysctl_tcp_rmem[0] = SK_MEM_QUANTUM;
+	sysctl_tcp_rmem[1] = 87380;
+	sysctl_tcp_rmem[2] = max(87380, max_rshare);
+
+	pr_info("Hash tables configured (established %u bind %u)\n",
+		tcp_hashinfo.ehash_mask + 1, tcp_hashinfo.bhash_size);
+
+	tcp_metrics_init();
+	BUG_ON(tcp_register_congestion_control(&tcp_reno) != 0);
+	tcp_tasklet_init();
+}