diff --git a/src/kernel/linux/v4.14/net/kcm/Kconfig b/src/kernel/linux/v4.14/net/kcm/Kconfig
new file mode 100644
index 0000000..87fca36
--- /dev/null
+++ b/src/kernel/linux/v4.14/net/kcm/Kconfig
@@ -0,0 +1,11 @@
+
+config AF_KCM
+	tristate "KCM sockets"
+	depends on INET
+	select BPF_SYSCALL
+	select STREAM_PARSER
+	---help---
+	  KCM (Kernel Connection Multiplexor) sockets provide a method
+	  for multiplexing messages of a message based application
+	  protocol over kernel connectons (e.g. TCP connections).
+
diff --git a/src/kernel/linux/v4.14/net/kcm/Makefile b/src/kernel/linux/v4.14/net/kcm/Makefile
new file mode 100644
index 0000000..7125613
--- /dev/null
+++ b/src/kernel/linux/v4.14/net/kcm/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_AF_KCM) += kcm.o
+
+kcm-y := kcmsock.o kcmproc.o
diff --git a/src/kernel/linux/v4.14/net/kcm/kcmproc.c b/src/kernel/linux/v4.14/net/kcm/kcmproc.c
new file mode 100644
index 0000000..bd57233
--- /dev/null
+++ b/src/kernel/linux/v4.14/net/kcm/kcmproc.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/proc_fs.h>
+#include <linux/rculist.h>
+#include <linux/seq_file.h>
+#include <linux/socket.h>
+#include <net/inet_sock.h>
+#include <net/kcm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/tcp.h>
+
+#ifdef CONFIG_PROC_FS
+struct kcm_seq_muxinfo {
+	char				*name;
+	const struct file_operations	*seq_fops;
+	const struct seq_operations	seq_ops;
+};
+
+static struct kcm_mux *kcm_get_first(struct seq_file *seq)
+{
+	struct net *net = seq_file_net(seq);
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+
+	return list_first_or_null_rcu(&knet->mux_list,
+				      struct kcm_mux, kcm_mux_list);
+}
+
+static struct kcm_mux *kcm_get_next(struct kcm_mux *mux)
+{
+	struct kcm_net *knet = mux->knet;
+
+	return list_next_or_null_rcu(&knet->mux_list, &mux->kcm_mux_list,
+				     struct kcm_mux, kcm_mux_list);
+}
+
+static struct kcm_mux *kcm_get_idx(struct seq_file *seq, loff_t pos)
+{
+	struct net *net = seq_file_net(seq);
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+	struct kcm_mux *m;
+
+	list_for_each_entry_rcu(m, &knet->mux_list, kcm_mux_list) {
+		if (!pos)
+			return m;
+		--pos;
+	}
+	return NULL;
+}
+
+static void *kcm_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	void *p;
+
+	if (v == SEQ_START_TOKEN)
+		p = kcm_get_first(seq);
+	else
+		p = kcm_get_next(v);
+	++*pos;
+	return p;
+}
+
+static void *kcm_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(rcu)
+{
+	rcu_read_lock();
+
+	if (!*pos)
+		return SEQ_START_TOKEN;
+	else
+		return kcm_get_idx(seq, *pos - 1);
+}
+
+static void kcm_seq_stop(struct seq_file *seq, void *v)
+	__releases(rcu)
+{
+	rcu_read_unlock();
+}
+
+struct kcm_proc_mux_state {
+	struct seq_net_private p;
+	int idx;
+};
+
+static int kcm_seq_open(struct inode *inode, struct file *file)
+{
+	struct kcm_seq_muxinfo *muxinfo = PDE_DATA(inode);
+
+	return seq_open_net(inode, file, &muxinfo->seq_ops,
+			   sizeof(struct kcm_proc_mux_state));
+}
+
+static void kcm_format_mux_header(struct seq_file *seq)
+{
+	struct net *net = seq_file_net(seq);
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+
+	seq_printf(seq,
+		   "*** KCM statistics (%d MUX) ****\n",
+		   knet->count);
+
+	seq_printf(seq,
+		   "%-14s %-10s %-16s %-10s %-16s %-8s %-8s %-8s %-8s %s",
+		   "Object",
+		   "RX-Msgs",
+		   "RX-Bytes",
+		   "TX-Msgs",
+		   "TX-Bytes",
+		   "Recv-Q",
+		   "Rmem",
+		   "Send-Q",
+		   "Smem",
+		   "Status");
+
+	/* XXX: pdsts header stuff here */
+	seq_puts(seq, "\n");
+}
+
+static void kcm_format_sock(struct kcm_sock *kcm, struct seq_file *seq,
+			    int i, int *len)
+{
+	seq_printf(seq,
+		   "   kcm-%-7u %-10llu %-16llu %-10llu %-16llu %-8d %-8d %-8d %-8s ",
+		   kcm->index,
+		   kcm->stats.rx_msgs,
+		   kcm->stats.rx_bytes,
+		   kcm->stats.tx_msgs,
+		   kcm->stats.tx_bytes,
+		   kcm->sk.sk_receive_queue.qlen,
+		   sk_rmem_alloc_get(&kcm->sk),
+		   kcm->sk.sk_write_queue.qlen,
+		   "-");
+
+	if (kcm->tx_psock)
+		seq_printf(seq, "Psck-%u ", kcm->tx_psock->index);
+
+	if (kcm->tx_wait)
+		seq_puts(seq, "TxWait ");
+
+	if (kcm->tx_wait_more)
+		seq_puts(seq, "WMore ");
+
+	if (kcm->rx_wait)
+		seq_puts(seq, "RxWait ");
+
+	seq_puts(seq, "\n");
+}
+
+static void kcm_format_psock(struct kcm_psock *psock, struct seq_file *seq,
+			     int i, int *len)
+{
+	seq_printf(seq,
+		   "   psock-%-5u %-10llu %-16llu %-10llu %-16llu %-8d %-8d %-8d %-8d ",
+		   psock->index,
+		   psock->strp.stats.msgs,
+		   psock->strp.stats.bytes,
+		   psock->stats.tx_msgs,
+		   psock->stats.tx_bytes,
+		   psock->sk->sk_receive_queue.qlen,
+		   atomic_read(&psock->sk->sk_rmem_alloc),
+		   psock->sk->sk_write_queue.qlen,
+		   refcount_read(&psock->sk->sk_wmem_alloc));
+
+	if (psock->done)
+		seq_puts(seq, "Done ");
+
+	if (psock->tx_stopped)
+		seq_puts(seq, "TxStop ");
+
+	if (psock->strp.stopped)
+		seq_puts(seq, "RxStop ");
+
+	if (psock->tx_kcm)
+		seq_printf(seq, "Rsvd-%d ", psock->tx_kcm->index);
+
+	if (!psock->strp.paused && !psock->ready_rx_msg) {
+		if (psock->sk->sk_receive_queue.qlen) {
+			if (psock->strp.need_bytes)
+				seq_printf(seq, "RxWait=%u ",
+					   psock->strp.need_bytes);
+			else
+				seq_printf(seq, "RxWait ");
+		}
+	} else  {
+		if (psock->strp.paused)
+			seq_puts(seq, "RxPause ");
+
+		if (psock->ready_rx_msg)
+			seq_puts(seq, "RdyRx ");
+	}
+
+	seq_puts(seq, "\n");
+}
+
+static void
+kcm_format_mux(struct kcm_mux *mux, loff_t idx, struct seq_file *seq)
+{
+	int i, len;
+	struct kcm_sock *kcm;
+	struct kcm_psock *psock;
+
+	/* mux information */
+	seq_printf(seq,
+		   "%-6s%-8s %-10llu %-16llu %-10llu %-16llu %-8s %-8s %-8s %-8s ",
+		   "mux", "",
+		   mux->stats.rx_msgs,
+		   mux->stats.rx_bytes,
+		   mux->stats.tx_msgs,
+		   mux->stats.tx_bytes,
+		   "-", "-", "-", "-");
+
+	seq_printf(seq, "KCMs: %d, Psocks %d\n",
+		   mux->kcm_socks_cnt, mux->psocks_cnt);
+
+	/* kcm sock information */
+	i = 0;
+	spin_lock_bh(&mux->lock);
+	list_for_each_entry(kcm, &mux->kcm_socks, kcm_sock_list) {
+		kcm_format_sock(kcm, seq, i, &len);
+		i++;
+	}
+	i = 0;
+	list_for_each_entry(psock, &mux->psocks, psock_list) {
+		kcm_format_psock(psock, seq, i, &len);
+		i++;
+	}
+	spin_unlock_bh(&mux->lock);
+}
+
+static int kcm_seq_show(struct seq_file *seq, void *v)
+{
+	struct kcm_proc_mux_state *mux_state;
+
+	mux_state = seq->private;
+	if (v == SEQ_START_TOKEN) {
+		mux_state->idx = 0;
+		kcm_format_mux_header(seq);
+	} else {
+		kcm_format_mux(v, mux_state->idx, seq);
+		mux_state->idx++;
+	}
+	return 0;
+}
+
+static const struct file_operations kcm_seq_fops = {
+	.owner		= THIS_MODULE,
+	.open		= kcm_seq_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release_net,
+};
+
+static struct kcm_seq_muxinfo kcm_seq_muxinfo = {
+	.name		= "kcm",
+	.seq_fops	= &kcm_seq_fops,
+	.seq_ops	= {
+		.show	= kcm_seq_show,
+		.start	= kcm_seq_start,
+		.next	= kcm_seq_next,
+		.stop	= kcm_seq_stop,
+	}
+};
+
+static int kcm_proc_register(struct net *net, struct kcm_seq_muxinfo *muxinfo)
+{
+	struct proc_dir_entry *p;
+	int rc = 0;
+
+	p = proc_create_data(muxinfo->name, S_IRUGO, net->proc_net,
+			     muxinfo->seq_fops, muxinfo);
+	if (!p)
+		rc = -ENOMEM;
+	return rc;
+}
+EXPORT_SYMBOL(kcm_proc_register);
+
+static void kcm_proc_unregister(struct net *net,
+				struct kcm_seq_muxinfo *muxinfo)
+{
+	remove_proc_entry(muxinfo->name, net->proc_net);
+}
+EXPORT_SYMBOL(kcm_proc_unregister);
+
+static int kcm_stats_seq_show(struct seq_file *seq, void *v)
+{
+	struct kcm_psock_stats psock_stats;
+	struct kcm_mux_stats mux_stats;
+	struct strp_aggr_stats strp_stats;
+	struct kcm_mux *mux;
+	struct kcm_psock *psock;
+	struct net *net = seq->private;
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+
+	memset(&mux_stats, 0, sizeof(mux_stats));
+	memset(&psock_stats, 0, sizeof(psock_stats));
+	memset(&strp_stats, 0, sizeof(strp_stats));
+
+	mutex_lock(&knet->mutex);
+
+	aggregate_mux_stats(&knet->aggregate_mux_stats, &mux_stats);
+	aggregate_psock_stats(&knet->aggregate_psock_stats,
+			      &psock_stats);
+	aggregate_strp_stats(&knet->aggregate_strp_stats,
+			     &strp_stats);
+
+	list_for_each_entry_rcu(mux, &knet->mux_list, kcm_mux_list) {
+		spin_lock_bh(&mux->lock);
+		aggregate_mux_stats(&mux->stats, &mux_stats);
+		aggregate_psock_stats(&mux->aggregate_psock_stats,
+				      &psock_stats);
+		aggregate_strp_stats(&mux->aggregate_strp_stats,
+				     &strp_stats);
+		list_for_each_entry(psock, &mux->psocks, psock_list) {
+			aggregate_psock_stats(&psock->stats, &psock_stats);
+			save_strp_stats(&psock->strp, &strp_stats);
+		}
+
+		spin_unlock_bh(&mux->lock);
+	}
+
+	mutex_unlock(&knet->mutex);
+
+	seq_printf(seq,
+		   "%-8s %-10s %-16s %-10s %-16s %-10s %-10s %-10s %-10s %-10s\n",
+		   "MUX",
+		   "RX-Msgs",
+		   "RX-Bytes",
+		   "TX-Msgs",
+		   "TX-Bytes",
+		   "TX-Retries",
+		   "Attach",
+		   "Unattach",
+		   "UnattchRsvd",
+		   "RX-RdyDrops");
+
+	seq_printf(seq,
+		   "%-8s %-10llu %-16llu %-10llu %-16llu %-10u %-10u %-10u %-10u %-10u\n",
+		   "",
+		   mux_stats.rx_msgs,
+		   mux_stats.rx_bytes,
+		   mux_stats.tx_msgs,
+		   mux_stats.tx_bytes,
+		   mux_stats.tx_retries,
+		   mux_stats.psock_attach,
+		   mux_stats.psock_unattach_rsvd,
+		   mux_stats.psock_unattach,
+		   mux_stats.rx_ready_drops);
+
+	seq_printf(seq,
+		   "%-8s %-10s %-16s %-10s %-16s %-10s %-10s %-10s %-10s %-10s %-10s %-10s %-10s %-10s %-10s %-10s\n",
+		   "Psock",
+		   "RX-Msgs",
+		   "RX-Bytes",
+		   "TX-Msgs",
+		   "TX-Bytes",
+		   "Reserved",
+		   "Unreserved",
+		   "RX-Aborts",
+		   "RX-Intr",
+		   "RX-Unrecov",
+		   "RX-MemFail",
+		   "RX-NeedMor",
+		   "RX-BadLen",
+		   "RX-TooBig",
+		   "RX-Timeout",
+		   "TX-Aborts");
+
+	seq_printf(seq,
+		   "%-8s %-10llu %-16llu %-10llu %-16llu %-10llu %-10llu %-10u %-10u %-10u %-10u %-10u %-10u %-10u %-10u %-10u\n",
+		   "",
+		   strp_stats.msgs,
+		   strp_stats.bytes,
+		   psock_stats.tx_msgs,
+		   psock_stats.tx_bytes,
+		   psock_stats.reserved,
+		   psock_stats.unreserved,
+		   strp_stats.aborts,
+		   strp_stats.interrupted,
+		   strp_stats.unrecov_intr,
+		   strp_stats.mem_fail,
+		   strp_stats.need_more_hdr,
+		   strp_stats.bad_hdr_len,
+		   strp_stats.msg_too_big,
+		   strp_stats.msg_timeouts,
+		   psock_stats.tx_aborts);
+
+	return 0;
+}
+
+static int kcm_stats_seq_open(struct inode *inode, struct file *file)
+{
+	return single_open_net(inode, file, kcm_stats_seq_show);
+}
+
+static const struct file_operations kcm_stats_seq_fops = {
+	.owner   = THIS_MODULE,
+	.open    = kcm_stats_seq_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = single_release_net,
+};
+
+static int kcm_proc_init_net(struct net *net)
+{
+	int err;
+
+	if (!proc_create("kcm_stats", S_IRUGO, net->proc_net,
+			 &kcm_stats_seq_fops)) {
+		err = -ENOMEM;
+		goto out_kcm_stats;
+	}
+
+	err = kcm_proc_register(net, &kcm_seq_muxinfo);
+	if (err)
+		goto out_kcm;
+
+	return 0;
+
+out_kcm:
+	remove_proc_entry("kcm_stats", net->proc_net);
+out_kcm_stats:
+	return err;
+}
+
+static void kcm_proc_exit_net(struct net *net)
+{
+	kcm_proc_unregister(net, &kcm_seq_muxinfo);
+	remove_proc_entry("kcm_stats", net->proc_net);
+}
+
+static struct pernet_operations kcm_net_ops = {
+	.init = kcm_proc_init_net,
+	.exit = kcm_proc_exit_net,
+};
+
+int __init kcm_proc_init(void)
+{
+	return register_pernet_subsys(&kcm_net_ops);
+}
+
+void __exit kcm_proc_exit(void)
+{
+	unregister_pernet_subsys(&kcm_net_ops);
+}
+
+#endif /* CONFIG_PROC_FS */
diff --git a/src/kernel/linux/v4.14/net/kcm/kcmsock.c b/src/kernel/linux/v4.14/net/kcm/kcmsock.c
new file mode 100644
index 0000000..7b4f3f8
--- /dev/null
+++ b/src/kernel/linux/v4.14/net/kcm/kcmsock.c
@@ -0,0 +1,2112 @@
+/*
+ * Kernel Connection Multiplexor
+ *
+ * Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ */
+
+#include <linux/bpf.h>
+#include <linux/errno.h>
+#include <linux/errqueue.h>
+#include <linux/file.h>
+#include <linux/in.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <linux/netdevice.h>
+#include <linux/poll.h>
+#include <linux/rculist.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/uaccess.h>
+#include <linux/workqueue.h>
+#include <linux/syscalls.h>
+#include <linux/sched/signal.h>
+
+#include <net/kcm.h>
+#include <net/netns/generic.h>
+#include <net/sock.h>
+#include <uapi/linux/kcm.h>
+
+unsigned int kcm_net_id;
+
+static struct kmem_cache *kcm_psockp __read_mostly;
+static struct kmem_cache *kcm_muxp __read_mostly;
+static struct workqueue_struct *kcm_wq;
+
+static inline struct kcm_sock *kcm_sk(const struct sock *sk)
+{
+	return (struct kcm_sock *)sk;
+}
+
+static inline struct kcm_tx_msg *kcm_tx_msg(struct sk_buff *skb)
+{
+	return (struct kcm_tx_msg *)skb->cb;
+}
+
+static void report_csk_error(struct sock *csk, int err)
+{
+	csk->sk_err = EPIPE;
+	csk->sk_error_report(csk);
+}
+
+static void kcm_abort_tx_psock(struct kcm_psock *psock, int err,
+			       bool wakeup_kcm)
+{
+	struct sock *csk = psock->sk;
+	struct kcm_mux *mux = psock->mux;
+
+	/* Unrecoverable error in transmit */
+
+	spin_lock_bh(&mux->lock);
+
+	if (psock->tx_stopped) {
+		spin_unlock_bh(&mux->lock);
+		return;
+	}
+
+	psock->tx_stopped = 1;
+	KCM_STATS_INCR(psock->stats.tx_aborts);
+
+	if (!psock->tx_kcm) {
+		/* Take off psocks_avail list */
+		list_del(&psock->psock_avail_list);
+	} else if (wakeup_kcm) {
+		/* In this case psock is being aborted while outside of
+		 * write_msgs and psock is reserved. Schedule tx_work
+		 * to handle the failure there. Need to commit tx_stopped
+		 * before queuing work.
+		 */
+		smp_mb();
+
+		queue_work(kcm_wq, &psock->tx_kcm->tx_work);
+	}
+
+	spin_unlock_bh(&mux->lock);
+
+	/* Report error on lower socket */
+	report_csk_error(csk, err);
+}
+
+/* RX mux lock held. */
+static void kcm_update_rx_mux_stats(struct kcm_mux *mux,
+				    struct kcm_psock *psock)
+{
+	STRP_STATS_ADD(mux->stats.rx_bytes,
+		       psock->strp.stats.bytes -
+		       psock->saved_rx_bytes);
+	mux->stats.rx_msgs +=
+		psock->strp.stats.msgs - psock->saved_rx_msgs;
+	psock->saved_rx_msgs = psock->strp.stats.msgs;
+	psock->saved_rx_bytes = psock->strp.stats.bytes;
+}
+
+static void kcm_update_tx_mux_stats(struct kcm_mux *mux,
+				    struct kcm_psock *psock)
+{
+	KCM_STATS_ADD(mux->stats.tx_bytes,
+		      psock->stats.tx_bytes - psock->saved_tx_bytes);
+	mux->stats.tx_msgs +=
+		psock->stats.tx_msgs - psock->saved_tx_msgs;
+	psock->saved_tx_msgs = psock->stats.tx_msgs;
+	psock->saved_tx_bytes = psock->stats.tx_bytes;
+}
+
+static int kcm_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
+
+/* KCM is ready to receive messages on its queue-- either the KCM is new or
+ * has become unblocked after being blocked on full socket buffer. Queue any
+ * pending ready messages on a psock. RX mux lock held.
+ */
+static void kcm_rcv_ready(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+	struct kcm_psock *psock;
+	struct sk_buff *skb;
+
+	if (unlikely(kcm->rx_wait || kcm->rx_psock || kcm->rx_disabled))
+		return;
+
+	while (unlikely((skb = __skb_dequeue(&mux->rx_hold_queue)))) {
+		if (kcm_queue_rcv_skb(&kcm->sk, skb)) {
+			/* Assuming buffer limit has been reached */
+			skb_queue_head(&mux->rx_hold_queue, skb);
+			WARN_ON(!sk_rmem_alloc_get(&kcm->sk));
+			return;
+		}
+	}
+
+	while (!list_empty(&mux->psocks_ready)) {
+		psock = list_first_entry(&mux->psocks_ready, struct kcm_psock,
+					 psock_ready_list);
+
+		if (kcm_queue_rcv_skb(&kcm->sk, psock->ready_rx_msg)) {
+			/* Assuming buffer limit has been reached */
+			WARN_ON(!sk_rmem_alloc_get(&kcm->sk));
+			return;
+		}
+
+		/* Consumed the ready message on the psock. Schedule rx_work to
+		 * get more messages.
+		 */
+		list_del(&psock->psock_ready_list);
+		psock->ready_rx_msg = NULL;
+		/* Commit clearing of ready_rx_msg for queuing work */
+		smp_mb();
+
+		strp_unpause(&psock->strp);
+		strp_check_rcv(&psock->strp);
+	}
+
+	/* Buffer limit is okay now, add to ready list */
+	list_add_tail(&kcm->wait_rx_list,
+		      &kcm->mux->kcm_rx_waiters);
+	kcm->rx_wait = true;
+}
+
+static void kcm_rfree(struct sk_buff *skb)
+{
+	struct sock *sk = skb->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+	struct kcm_mux *mux = kcm->mux;
+	unsigned int len = skb->truesize;
+
+	sk_mem_uncharge(sk, len);
+	atomic_sub(len, &sk->sk_rmem_alloc);
+
+	/* For reading rx_wait and rx_psock without holding lock */
+	smp_mb__after_atomic();
+
+	if (!kcm->rx_wait && !kcm->rx_psock &&
+	    sk_rmem_alloc_get(sk) < sk->sk_rcvlowat) {
+		spin_lock_bh(&mux->rx_lock);
+		kcm_rcv_ready(kcm);
+		spin_unlock_bh(&mux->rx_lock);
+	}
+}
+
+static int kcm_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
+{
+	struct sk_buff_head *list = &sk->sk_receive_queue;
+
+	if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
+		return -ENOMEM;
+
+	if (!sk_rmem_schedule(sk, skb, skb->truesize))
+		return -ENOBUFS;
+
+	skb->dev = NULL;
+
+	skb_orphan(skb);
+	skb->sk = sk;
+	skb->destructor = kcm_rfree;
+	atomic_add(skb->truesize, &sk->sk_rmem_alloc);
+	sk_mem_charge(sk, skb->truesize);
+
+	skb_queue_tail(list, skb);
+
+	if (!sock_flag(sk, SOCK_DEAD))
+		sk->sk_data_ready(sk);
+
+	return 0;
+}
+
+/* Requeue received messages for a kcm socket to other kcm sockets. This is
+ * called with a kcm socket is receive disabled.
+ * RX mux lock held.
+ */
+static void requeue_rx_msgs(struct kcm_mux *mux, struct sk_buff_head *head)
+{
+	struct sk_buff *skb;
+	struct kcm_sock *kcm;
+
+	while ((skb = __skb_dequeue(head))) {
+		/* Reset destructor to avoid calling kcm_rcv_ready */
+		skb->destructor = sock_rfree;
+		skb_orphan(skb);
+try_again:
+		if (list_empty(&mux->kcm_rx_waiters)) {
+			skb_queue_tail(&mux->rx_hold_queue, skb);
+			continue;
+		}
+
+		kcm = list_first_entry(&mux->kcm_rx_waiters,
+				       struct kcm_sock, wait_rx_list);
+
+		if (kcm_queue_rcv_skb(&kcm->sk, skb)) {
+			/* Should mean socket buffer full */
+			list_del(&kcm->wait_rx_list);
+			kcm->rx_wait = false;
+
+			/* Commit rx_wait to read in kcm_free */
+			smp_wmb();
+
+			goto try_again;
+		}
+	}
+}
+
+/* Lower sock lock held */
+static struct kcm_sock *reserve_rx_kcm(struct kcm_psock *psock,
+				       struct sk_buff *head)
+{
+	struct kcm_mux *mux = psock->mux;
+	struct kcm_sock *kcm;
+
+	WARN_ON(psock->ready_rx_msg);
+
+	if (psock->rx_kcm)
+		return psock->rx_kcm;
+
+	spin_lock_bh(&mux->rx_lock);
+
+	if (psock->rx_kcm) {
+		spin_unlock_bh(&mux->rx_lock);
+		return psock->rx_kcm;
+	}
+
+	kcm_update_rx_mux_stats(mux, psock);
+
+	if (list_empty(&mux->kcm_rx_waiters)) {
+		psock->ready_rx_msg = head;
+		strp_pause(&psock->strp);
+		list_add_tail(&psock->psock_ready_list,
+			      &mux->psocks_ready);
+		spin_unlock_bh(&mux->rx_lock);
+		return NULL;
+	}
+
+	kcm = list_first_entry(&mux->kcm_rx_waiters,
+			       struct kcm_sock, wait_rx_list);
+	list_del(&kcm->wait_rx_list);
+	kcm->rx_wait = false;
+
+	psock->rx_kcm = kcm;
+	kcm->rx_psock = psock;
+
+	spin_unlock_bh(&mux->rx_lock);
+
+	return kcm;
+}
+
+static void kcm_done(struct kcm_sock *kcm);
+
+static void kcm_done_work(struct work_struct *w)
+{
+	kcm_done(container_of(w, struct kcm_sock, done_work));
+}
+
+/* Lower sock held */
+static void unreserve_rx_kcm(struct kcm_psock *psock,
+			     bool rcv_ready)
+{
+	struct kcm_sock *kcm = psock->rx_kcm;
+	struct kcm_mux *mux = psock->mux;
+
+	if (!kcm)
+		return;
+
+	spin_lock_bh(&mux->rx_lock);
+
+	psock->rx_kcm = NULL;
+	kcm->rx_psock = NULL;
+
+	/* Commit kcm->rx_psock before sk_rmem_alloc_get to sync with
+	 * kcm_rfree
+	 */
+	smp_mb();
+
+	if (unlikely(kcm->done)) {
+		spin_unlock_bh(&mux->rx_lock);
+
+		/* Need to run kcm_done in a task since we need to qcquire
+		 * callback locks which may already be held here.
+		 */
+		INIT_WORK(&kcm->done_work, kcm_done_work);
+		schedule_work(&kcm->done_work);
+		return;
+	}
+
+	if (unlikely(kcm->rx_disabled)) {
+		requeue_rx_msgs(mux, &kcm->sk.sk_receive_queue);
+	} else if (rcv_ready || unlikely(!sk_rmem_alloc_get(&kcm->sk))) {
+		/* Check for degenerative race with rx_wait that all
+		 * data was dequeued (accounted for in kcm_rfree).
+		 */
+		kcm_rcv_ready(kcm);
+	}
+	spin_unlock_bh(&mux->rx_lock);
+}
+
+/* Lower sock lock held */
+static void psock_data_ready(struct sock *sk)
+{
+	struct kcm_psock *psock;
+
+	read_lock_bh(&sk->sk_callback_lock);
+
+	psock = (struct kcm_psock *)sk->sk_user_data;
+	if (likely(psock))
+		strp_data_ready(&psock->strp);
+
+	read_unlock_bh(&sk->sk_callback_lock);
+}
+
+/* Called with lower sock held */
+static void kcm_rcv_strparser(struct strparser *strp, struct sk_buff *skb)
+{
+	struct kcm_psock *psock = container_of(strp, struct kcm_psock, strp);
+	struct kcm_sock *kcm;
+
+try_queue:
+	kcm = reserve_rx_kcm(psock, skb);
+	if (!kcm) {
+		 /* Unable to reserve a KCM, message is held in psock and strp
+		  * is paused.
+		  */
+		return;
+	}
+
+	if (kcm_queue_rcv_skb(&kcm->sk, skb)) {
+		/* Should mean socket buffer full */
+		unreserve_rx_kcm(psock, false);
+		goto try_queue;
+	}
+}
+
+static int kcm_parse_func_strparser(struct strparser *strp, struct sk_buff *skb)
+{
+	struct kcm_psock *psock = container_of(strp, struct kcm_psock, strp);
+	struct bpf_prog *prog = psock->bpf_prog;
+
+	return (*prog->bpf_func)(skb, prog->insnsi);
+}
+
+static int kcm_read_sock_done(struct strparser *strp, int err)
+{
+	struct kcm_psock *psock = container_of(strp, struct kcm_psock, strp);
+
+	unreserve_rx_kcm(psock, true);
+
+	return err;
+}
+
+static void psock_state_change(struct sock *sk)
+{
+	/* TCP only does a POLLIN for a half close. Do a POLLHUP here
+	 * since application will normally not poll with POLLIN
+	 * on the TCP sockets.
+	 */
+
+	report_csk_error(sk, EPIPE);
+}
+
+static void psock_write_space(struct sock *sk)
+{
+	struct kcm_psock *psock;
+	struct kcm_mux *mux;
+	struct kcm_sock *kcm;
+
+	read_lock_bh(&sk->sk_callback_lock);
+
+	psock = (struct kcm_psock *)sk->sk_user_data;
+	if (unlikely(!psock))
+		goto out;
+	mux = psock->mux;
+
+	spin_lock_bh(&mux->lock);
+
+	/* Check if the socket is reserved so someone is waiting for sending. */
+	kcm = psock->tx_kcm;
+	if (kcm && !unlikely(kcm->tx_stopped))
+		queue_work(kcm_wq, &kcm->tx_work);
+
+	spin_unlock_bh(&mux->lock);
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
+}
+
+static void unreserve_psock(struct kcm_sock *kcm);
+
+/* kcm sock is locked. */
+static struct kcm_psock *reserve_psock(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+	struct kcm_psock *psock;
+
+	psock = kcm->tx_psock;
+
+	smp_rmb(); /* Must read tx_psock before tx_wait */
+
+	if (psock) {
+		WARN_ON(kcm->tx_wait);
+		if (unlikely(psock->tx_stopped))
+			unreserve_psock(kcm);
+		else
+			return kcm->tx_psock;
+	}
+
+	spin_lock_bh(&mux->lock);
+
+	/* Check again under lock to see if psock was reserved for this
+	 * psock via psock_unreserve.
+	 */
+	psock = kcm->tx_psock;
+	if (unlikely(psock)) {
+		WARN_ON(kcm->tx_wait);
+		spin_unlock_bh(&mux->lock);
+		return kcm->tx_psock;
+	}
+
+	if (!list_empty(&mux->psocks_avail)) {
+		psock = list_first_entry(&mux->psocks_avail,
+					 struct kcm_psock,
+					 psock_avail_list);
+		list_del(&psock->psock_avail_list);
+		if (kcm->tx_wait) {
+			list_del(&kcm->wait_psock_list);
+			kcm->tx_wait = false;
+		}
+		kcm->tx_psock = psock;
+		psock->tx_kcm = kcm;
+		KCM_STATS_INCR(psock->stats.reserved);
+	} else if (!kcm->tx_wait) {
+		list_add_tail(&kcm->wait_psock_list,
+			      &mux->kcm_tx_waiters);
+		kcm->tx_wait = true;
+	}
+
+	spin_unlock_bh(&mux->lock);
+
+	return psock;
+}
+
+/* mux lock held */
+static void psock_now_avail(struct kcm_psock *psock)
+{
+	struct kcm_mux *mux = psock->mux;
+	struct kcm_sock *kcm;
+
+	if (list_empty(&mux->kcm_tx_waiters)) {
+		list_add_tail(&psock->psock_avail_list,
+			      &mux->psocks_avail);
+	} else {
+		kcm = list_first_entry(&mux->kcm_tx_waiters,
+				       struct kcm_sock,
+				       wait_psock_list);
+		list_del(&kcm->wait_psock_list);
+		kcm->tx_wait = false;
+		psock->tx_kcm = kcm;
+
+		/* Commit before changing tx_psock since that is read in
+		 * reserve_psock before queuing work.
+		 */
+		smp_mb();
+
+		kcm->tx_psock = psock;
+		KCM_STATS_INCR(psock->stats.reserved);
+		queue_work(kcm_wq, &kcm->tx_work);
+	}
+}
+
+/* kcm sock is locked. */
+static void unreserve_psock(struct kcm_sock *kcm)
+{
+	struct kcm_psock *psock;
+	struct kcm_mux *mux = kcm->mux;
+
+	spin_lock_bh(&mux->lock);
+
+	psock = kcm->tx_psock;
+
+	if (WARN_ON(!psock)) {
+		spin_unlock_bh(&mux->lock);
+		return;
+	}
+
+	smp_rmb(); /* Read tx_psock before tx_wait */
+
+	kcm_update_tx_mux_stats(mux, psock);
+
+	WARN_ON(kcm->tx_wait);
+
+	kcm->tx_psock = NULL;
+	psock->tx_kcm = NULL;
+	KCM_STATS_INCR(psock->stats.unreserved);
+
+	if (unlikely(psock->tx_stopped)) {
+		if (psock->done) {
+			/* Deferred free */
+			list_del(&psock->psock_list);
+			mux->psocks_cnt--;
+			sock_put(psock->sk);
+			fput(psock->sk->sk_socket->file);
+			kmem_cache_free(kcm_psockp, psock);
+		}
+
+		/* Don't put back on available list */
+
+		spin_unlock_bh(&mux->lock);
+
+		return;
+	}
+
+	psock_now_avail(psock);
+
+	spin_unlock_bh(&mux->lock);
+}
+
+static void kcm_report_tx_retry(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+
+	spin_lock_bh(&mux->lock);
+	KCM_STATS_INCR(mux->stats.tx_retries);
+	spin_unlock_bh(&mux->lock);
+}
+
+/* Write any messages ready on the kcm socket.  Called with kcm sock lock
+ * held.  Return bytes actually sent or error.
+ */
+static int kcm_write_msgs(struct kcm_sock *kcm)
+{
+	struct sock *sk = &kcm->sk;
+	struct kcm_psock *psock;
+	struct sk_buff *skb, *head;
+	struct kcm_tx_msg *txm;
+	unsigned short fragidx, frag_offset;
+	unsigned int sent, total_sent = 0;
+	int ret = 0;
+
+	kcm->tx_wait_more = false;
+	psock = kcm->tx_psock;
+	if (unlikely(psock && psock->tx_stopped)) {
+		/* A reserved psock was aborted asynchronously. Unreserve
+		 * it and we'll retry the message.
+		 */
+		unreserve_psock(kcm);
+		kcm_report_tx_retry(kcm);
+		if (skb_queue_empty(&sk->sk_write_queue))
+			return 0;
+
+		kcm_tx_msg(skb_peek(&sk->sk_write_queue))->sent = 0;
+
+	} else if (skb_queue_empty(&sk->sk_write_queue)) {
+		return 0;
+	}
+
+	head = skb_peek(&sk->sk_write_queue);
+	txm = kcm_tx_msg(head);
+
+	if (txm->sent) {
+		/* Send of first skbuff in queue already in progress */
+		if (WARN_ON(!psock)) {
+			ret = -EINVAL;
+			goto out;
+		}
+		sent = txm->sent;
+		frag_offset = txm->frag_offset;
+		fragidx = txm->fragidx;
+		skb = txm->frag_skb;
+
+		goto do_frag;
+	}
+
+try_again:
+	psock = reserve_psock(kcm);
+	if (!psock)
+		goto out;
+
+	do {
+		skb = head;
+		txm = kcm_tx_msg(head);
+		sent = 0;
+
+do_frag_list:
+		if (WARN_ON(!skb_shinfo(skb)->nr_frags)) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		for (fragidx = 0; fragidx < skb_shinfo(skb)->nr_frags;
+		     fragidx++) {
+			skb_frag_t *frag;
+
+			frag_offset = 0;
+do_frag:
+			frag = &skb_shinfo(skb)->frags[fragidx];
+			if (WARN_ON(!frag->size)) {
+				ret = -EINVAL;
+				goto out;
+			}
+
+			ret = kernel_sendpage(psock->sk->sk_socket,
+					      frag->page.p,
+					      frag->page_offset + frag_offset,
+					      frag->size - frag_offset,
+					      MSG_DONTWAIT);
+			if (ret <= 0) {
+				if (ret == -EAGAIN) {
+					/* Save state to try again when there's
+					 * write space on the socket
+					 */
+					txm->sent = sent;
+					txm->frag_offset = frag_offset;
+					txm->fragidx = fragidx;
+					txm->frag_skb = skb;
+
+					ret = 0;
+					goto out;
+				}
+
+				/* Hard failure in sending message, abort this
+				 * psock since it has lost framing
+				 * synchonization and retry sending the
+				 * message from the beginning.
+				 */
+				kcm_abort_tx_psock(psock, ret ? -ret : EPIPE,
+						   true);
+				unreserve_psock(kcm);
+
+				txm->sent = 0;
+				kcm_report_tx_retry(kcm);
+				ret = 0;
+
+				goto try_again;
+			}
+
+			sent += ret;
+			frag_offset += ret;
+			KCM_STATS_ADD(psock->stats.tx_bytes, ret);
+			if (frag_offset < frag->size) {
+				/* Not finished with this frag */
+				goto do_frag;
+			}
+		}
+
+		if (skb == head) {
+			if (skb_has_frag_list(skb)) {
+				skb = skb_shinfo(skb)->frag_list;
+				goto do_frag_list;
+			}
+		} else if (skb->next) {
+			skb = skb->next;
+			goto do_frag_list;
+		}
+
+		/* Successfully sent the whole packet, account for it. */
+		skb_dequeue(&sk->sk_write_queue);
+		kfree_skb(head);
+		sk->sk_wmem_queued -= sent;
+		total_sent += sent;
+		KCM_STATS_INCR(psock->stats.tx_msgs);
+	} while ((head = skb_peek(&sk->sk_write_queue)));
+out:
+	if (!head) {
+		/* Done with all queued messages. */
+		WARN_ON(!skb_queue_empty(&sk->sk_write_queue));
+		unreserve_psock(kcm);
+	}
+
+	/* Check if write space is available */
+	sk->sk_write_space(sk);
+
+	return total_sent ? : ret;
+}
+
+static void kcm_tx_work(struct work_struct *w)
+{
+	struct kcm_sock *kcm = container_of(w, struct kcm_sock, tx_work);
+	struct sock *sk = &kcm->sk;
+	int err;
+
+	lock_sock(sk);
+
+	/* Primarily for SOCK_DGRAM sockets, also handle asynchronous tx
+	 * aborts
+	 */
+	err = kcm_write_msgs(kcm);
+	if (err < 0) {
+		/* Hard failure in write, report error on KCM socket */
+		pr_warn("KCM: Hard failure on kcm_write_msgs %d\n", err);
+		report_csk_error(&kcm->sk, -err);
+		goto out;
+	}
+
+	/* Primarily for SOCK_SEQPACKET sockets */
+	if (likely(sk->sk_socket) &&
+	    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
+		clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+		sk->sk_write_space(sk);
+	}
+
+out:
+	release_sock(sk);
+}
+
+static void kcm_push(struct kcm_sock *kcm)
+{
+	if (kcm->tx_wait_more)
+		kcm_write_msgs(kcm);
+}
+
+static ssize_t kcm_sendpage(struct socket *sock, struct page *page,
+			    int offset, size_t size, int flags)
+
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+	struct sk_buff *skb = NULL, *head = NULL;
+	long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
+	bool eor;
+	int err = 0;
+	int i;
+
+	if (flags & MSG_SENDPAGE_NOTLAST)
+		flags |= MSG_MORE;
+
+	/* No MSG_EOR from splice, only look at MSG_MORE */
+	eor = !(flags & MSG_MORE);
+
+	lock_sock(sk);
+
+	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
+
+	err = -EPIPE;
+	if (sk->sk_err)
+		goto out_error;
+
+	if (kcm->seq_skb) {
+		/* Previously opened message */
+		head = kcm->seq_skb;
+		skb = kcm_tx_msg(head)->last_skb;
+		i = skb_shinfo(skb)->nr_frags;
+
+		if (skb_can_coalesce(skb, i, page, offset)) {
+			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size);
+			skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+			goto coalesced;
+		}
+
+		if (i >= MAX_SKB_FRAGS) {
+			struct sk_buff *tskb;
+
+			tskb = alloc_skb(0, sk->sk_allocation);
+			while (!tskb) {
+				kcm_push(kcm);
+				err = sk_stream_wait_memory(sk, &timeo);
+				if (err)
+					goto out_error;
+			}
+
+			if (head == skb)
+				skb_shinfo(head)->frag_list = tskb;
+			else
+				skb->next = tskb;
+
+			skb = tskb;
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+			i = 0;
+		}
+	} else {
+		/* Call the sk_stream functions to manage the sndbuf mem. */
+		if (!sk_stream_memory_free(sk)) {
+			kcm_push(kcm);
+			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+			err = sk_stream_wait_memory(sk, &timeo);
+			if (err)
+				goto out_error;
+		}
+
+		head = alloc_skb(0, sk->sk_allocation);
+		while (!head) {
+			kcm_push(kcm);
+			err = sk_stream_wait_memory(sk, &timeo);
+			if (err)
+				goto out_error;
+		}
+
+		skb = head;
+		i = 0;
+	}
+
+	get_page(page);
+	skb_fill_page_desc(skb, i, page, offset, size);
+	skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
+
+coalesced:
+	skb->len += size;
+	skb->data_len += size;
+	skb->truesize += size;
+	sk->sk_wmem_queued += size;
+	sk_mem_charge(sk, size);
+
+	if (head != skb) {
+		head->len += size;
+		head->data_len += size;
+		head->truesize += size;
+	}
+
+	if (eor) {
+		bool not_busy = skb_queue_empty(&sk->sk_write_queue);
+
+		/* Message complete, queue it on send buffer */
+		__skb_queue_tail(&sk->sk_write_queue, head);
+		kcm->seq_skb = NULL;
+		KCM_STATS_INCR(kcm->stats.tx_msgs);
+
+		if (flags & MSG_BATCH) {
+			kcm->tx_wait_more = true;
+		} else if (kcm->tx_wait_more || not_busy) {
+			err = kcm_write_msgs(kcm);
+			if (err < 0) {
+				/* We got a hard error in write_msgs but have
+				 * already queued this message. Report an error
+				 * in the socket, but don't affect return value
+				 * from sendmsg
+				 */
+				pr_warn("KCM: Hard failure on kcm_write_msgs\n");
+				report_csk_error(&kcm->sk, -err);
+			}
+		}
+	} else {
+		/* Message not complete, save state */
+		kcm->seq_skb = head;
+		kcm_tx_msg(head)->last_skb = skb;
+	}
+
+	KCM_STATS_ADD(kcm->stats.tx_bytes, size);
+
+	release_sock(sk);
+	return size;
+
+out_error:
+	kcm_push(kcm);
+
+	err = sk_stream_error(sk, flags, err);
+
+	/* make sure we wake any epoll edge trigger waiter */
+	if (unlikely(skb_queue_len(&sk->sk_write_queue) == 0 && err == -EAGAIN))
+		sk->sk_write_space(sk);
+
+	release_sock(sk);
+	return err;
+}
+
+static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+	struct sk_buff *skb = NULL, *head = NULL;
+	size_t copy, copied = 0;
+	long timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
+	int eor = (sock->type == SOCK_DGRAM) ?
+		  !(msg->msg_flags & MSG_MORE) : !!(msg->msg_flags & MSG_EOR);
+	int err = -EPIPE;
+
+	lock_sock(sk);
+
+	/* Per tcp_sendmsg this should be in poll */
+	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
+
+	if (sk->sk_err)
+		goto out_error;
+
+	if (kcm->seq_skb) {
+		/* Previously opened message */
+		head = kcm->seq_skb;
+		skb = kcm_tx_msg(head)->last_skb;
+		goto start;
+	}
+
+	/* Call the sk_stream functions to manage the sndbuf mem. */
+	if (!sk_stream_memory_free(sk)) {
+		kcm_push(kcm);
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+		err = sk_stream_wait_memory(sk, &timeo);
+		if (err)
+			goto out_error;
+	}
+
+	if (msg_data_left(msg)) {
+		/* New message, alloc head skb */
+		head = alloc_skb(0, sk->sk_allocation);
+		while (!head) {
+			kcm_push(kcm);
+			err = sk_stream_wait_memory(sk, &timeo);
+			if (err)
+				goto out_error;
+
+			head = alloc_skb(0, sk->sk_allocation);
+		}
+
+		skb = head;
+
+		/* Set ip_summed to CHECKSUM_UNNECESSARY to avoid calling
+		 * csum_and_copy_from_iter from skb_do_copy_data_nocache.
+		 */
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
+	}
+
+start:
+	while (msg_data_left(msg)) {
+		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) {
+				struct sk_buff *tskb;
+
+				tskb = alloc_skb(0, sk->sk_allocation);
+				if (!tskb)
+					goto wait_for_memory;
+
+				if (head == skb)
+					skb_shinfo(head)->frag_list = tskb;
+				else
+					skb->next = tskb;
+
+				skb = tskb;
+				skb->ip_summed = CHECKSUM_UNNECESSARY;
+				continue;
+			}
+			merge = false;
+		}
+
+		copy = min_t(int, msg_data_left(msg),
+			     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 out_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;
+		copied += copy;
+		if (head != skb) {
+			head->len += copy;
+			head->data_len += copy;
+		}
+
+		continue;
+
+wait_for_memory:
+		kcm_push(kcm);
+		err = sk_stream_wait_memory(sk, &timeo);
+		if (err)
+			goto out_error;
+	}
+
+	if (eor) {
+		bool not_busy = skb_queue_empty(&sk->sk_write_queue);
+
+		if (head) {
+			/* Message complete, queue it on send buffer */
+			__skb_queue_tail(&sk->sk_write_queue, head);
+			kcm->seq_skb = NULL;
+			KCM_STATS_INCR(kcm->stats.tx_msgs);
+		}
+
+		if (msg->msg_flags & MSG_BATCH) {
+			kcm->tx_wait_more = true;
+		} else if (kcm->tx_wait_more || not_busy) {
+			err = kcm_write_msgs(kcm);
+			if (err < 0) {
+				/* We got a hard error in write_msgs but have
+				 * already queued this message. Report an error
+				 * in the socket, but don't affect return value
+				 * from sendmsg
+				 */
+				pr_warn("KCM: Hard failure on kcm_write_msgs\n");
+				report_csk_error(&kcm->sk, -err);
+			}
+		}
+	} else {
+		/* Message not complete, save state */
+partial_message:
+		if (head) {
+			kcm->seq_skb = head;
+			kcm_tx_msg(head)->last_skb = skb;
+		}
+	}
+
+	KCM_STATS_ADD(kcm->stats.tx_bytes, copied);
+
+	release_sock(sk);
+	return copied;
+
+out_error:
+	kcm_push(kcm);
+
+	if (copied && sock->type == SOCK_SEQPACKET) {
+		/* Wrote some bytes before encountering an
+		 * error, return partial success.
+		 */
+		goto partial_message;
+	}
+
+	if (head != kcm->seq_skb)
+		kfree_skb(head);
+
+	err = sk_stream_error(sk, msg->msg_flags, err);
+
+	/* make sure we wake any epoll edge trigger waiter */
+	if (unlikely(skb_queue_len(&sk->sk_write_queue) == 0 && err == -EAGAIN))
+		sk->sk_write_space(sk);
+
+	release_sock(sk);
+	return err;
+}
+
+static struct sk_buff *kcm_wait_data(struct sock *sk, int flags,
+				     long timeo, int *err)
+{
+	struct sk_buff *skb;
+
+	while (!(skb = skb_peek(&sk->sk_receive_queue))) {
+		if (sk->sk_err) {
+			*err = sock_error(sk);
+			return NULL;
+		}
+
+		if (sock_flag(sk, SOCK_DONE))
+			return NULL;
+
+		if ((flags & MSG_DONTWAIT) || !timeo) {
+			*err = -EAGAIN;
+			return NULL;
+		}
+
+		sk_wait_data(sk, &timeo, NULL);
+
+		/* Handle signals */
+		if (signal_pending(current)) {
+			*err = sock_intr_errno(timeo);
+			return NULL;
+		}
+	}
+
+	return skb;
+}
+
+static int kcm_recvmsg(struct socket *sock, struct msghdr *msg,
+		       size_t len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm = kcm_sk(sk);
+	int err = 0;
+	long timeo;
+	struct strp_msg *stm;
+	int copied = 0;
+	struct sk_buff *skb;
+
+	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+
+	lock_sock(sk);
+
+	skb = kcm_wait_data(sk, flags, timeo, &err);
+	if (!skb)
+		goto out;
+
+	/* Okay, have a message on the receive queue */
+
+	stm = strp_msg(skb);
+
+	if (len > stm->full_len)
+		len = stm->full_len;
+
+	err = skb_copy_datagram_msg(skb, stm->offset, msg, len);
+	if (err < 0)
+		goto out;
+
+	copied = len;
+	if (likely(!(flags & MSG_PEEK))) {
+		KCM_STATS_ADD(kcm->stats.rx_bytes, copied);
+		if (copied < stm->full_len) {
+			if (sock->type == SOCK_DGRAM) {
+				/* Truncated message */
+				msg->msg_flags |= MSG_TRUNC;
+				goto msg_finished;
+			}
+			stm->offset += copied;
+			stm->full_len -= copied;
+		} else {
+msg_finished:
+			/* Finished with message */
+			msg->msg_flags |= MSG_EOR;
+			KCM_STATS_INCR(kcm->stats.rx_msgs);
+			skb_unlink(skb, &sk->sk_receive_queue);
+			kfree_skb(skb);
+		}
+	}
+
+out:
+	release_sock(sk);
+
+	return copied ? : err;
+}
+
+static ssize_t kcm_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 kcm_sock *kcm = kcm_sk(sk);
+	long timeo;
+	struct strp_msg *stm;
+	int err = 0;
+	ssize_t copied;
+	struct sk_buff *skb;
+
+	/* Only support splice for SOCKSEQPACKET */
+
+	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+
+	lock_sock(sk);
+
+	skb = kcm_wait_data(sk, flags, timeo, &err);
+	if (!skb)
+		goto err_out;
+
+	/* Okay, have a message on the receive queue */
+
+	stm = strp_msg(skb);
+
+	if (len > stm->full_len)
+		len = stm->full_len;
+
+	copied = skb_splice_bits(skb, sk, stm->offset, pipe, len, flags);
+	if (copied < 0) {
+		err = copied;
+		goto err_out;
+	}
+
+	KCM_STATS_ADD(kcm->stats.rx_bytes, copied);
+
+	stm->offset += copied;
+	stm->full_len -= copied;
+
+	/* We have no way to return MSG_EOR. If all the bytes have been
+	 * read we still leave the message in the receive socket buffer.
+	 * A subsequent recvmsg needs to be done to return MSG_EOR and
+	 * finish reading the message.
+	 */
+
+	release_sock(sk);
+
+	return copied;
+
+err_out:
+	release_sock(sk);
+
+	return err;
+}
+
+/* kcm sock lock held */
+static void kcm_recv_disable(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+
+	if (kcm->rx_disabled)
+		return;
+
+	spin_lock_bh(&mux->rx_lock);
+
+	kcm->rx_disabled = 1;
+
+	/* If a psock is reserved we'll do cleanup in unreserve */
+	if (!kcm->rx_psock) {
+		if (kcm->rx_wait) {
+			list_del(&kcm->wait_rx_list);
+			kcm->rx_wait = false;
+		}
+
+		requeue_rx_msgs(mux, &kcm->sk.sk_receive_queue);
+	}
+
+	spin_unlock_bh(&mux->rx_lock);
+}
+
+/* kcm sock lock held */
+static void kcm_recv_enable(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+
+	if (!kcm->rx_disabled)
+		return;
+
+	spin_lock_bh(&mux->rx_lock);
+
+	kcm->rx_disabled = 0;
+	kcm_rcv_ready(kcm);
+
+	spin_unlock_bh(&mux->rx_lock);
+}
+
+static int kcm_setsockopt(struct socket *sock, int level, int optname,
+			  char __user *optval, unsigned int optlen)
+{
+	struct kcm_sock *kcm = kcm_sk(sock->sk);
+	int val, valbool;
+	int err = 0;
+
+	if (level != SOL_KCM)
+		return -ENOPROTOOPT;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (get_user(val, (int __user *)optval))
+		return -EINVAL;
+
+	valbool = val ? 1 : 0;
+
+	switch (optname) {
+	case KCM_RECV_DISABLE:
+		lock_sock(&kcm->sk);
+		if (valbool)
+			kcm_recv_disable(kcm);
+		else
+			kcm_recv_enable(kcm);
+		release_sock(&kcm->sk);
+		break;
+	default:
+		err = -ENOPROTOOPT;
+	}
+
+	return err;
+}
+
+static int kcm_getsockopt(struct socket *sock, int level, int optname,
+			  char __user *optval, int __user *optlen)
+{
+	struct kcm_sock *kcm = kcm_sk(sock->sk);
+	int val, len;
+
+	if (level != SOL_KCM)
+		return -ENOPROTOOPT;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	len = min_t(unsigned int, len, sizeof(int));
+	if (len < 0)
+		return -EINVAL;
+
+	switch (optname) {
+	case KCM_RECV_DISABLE:
+		val = kcm->rx_disabled;
+		break;
+	default:
+		return -ENOPROTOOPT;
+	}
+
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+	return 0;
+}
+
+static void init_kcm_sock(struct kcm_sock *kcm, struct kcm_mux *mux)
+{
+	struct kcm_sock *tkcm;
+	struct list_head *head;
+	int index = 0;
+
+	/* For SOCK_SEQPACKET sock type, datagram_poll checks the sk_state, so
+	 * we set sk_state, otherwise epoll_wait always returns right away with
+	 * POLLHUP
+	 */
+	kcm->sk.sk_state = TCP_ESTABLISHED;
+
+	/* Add to mux's kcm sockets list */
+	kcm->mux = mux;
+	spin_lock_bh(&mux->lock);
+
+	head = &mux->kcm_socks;
+	list_for_each_entry(tkcm, &mux->kcm_socks, kcm_sock_list) {
+		if (tkcm->index != index)
+			break;
+		head = &tkcm->kcm_sock_list;
+		index++;
+	}
+
+	list_add(&kcm->kcm_sock_list, head);
+	kcm->index = index;
+
+	mux->kcm_socks_cnt++;
+	spin_unlock_bh(&mux->lock);
+
+	INIT_WORK(&kcm->tx_work, kcm_tx_work);
+
+	spin_lock_bh(&mux->rx_lock);
+	kcm_rcv_ready(kcm);
+	spin_unlock_bh(&mux->rx_lock);
+}
+
+static int kcm_attach(struct socket *sock, struct socket *csock,
+		      struct bpf_prog *prog)
+{
+	struct kcm_sock *kcm = kcm_sk(sock->sk);
+	struct kcm_mux *mux = kcm->mux;
+	struct sock *csk;
+	struct kcm_psock *psock = NULL, *tpsock;
+	struct list_head *head;
+	int index = 0;
+	static const struct strp_callbacks cb = {
+		.rcv_msg = kcm_rcv_strparser,
+		.parse_msg = kcm_parse_func_strparser,
+		.read_sock_done = kcm_read_sock_done,
+	};
+	int err = 0;
+
+	csk = csock->sk;
+	if (!csk)
+		return -EINVAL;
+
+	lock_sock(csk);
+
+	/* Only allow TCP sockets to be attached for now */
+	if ((csk->sk_family != AF_INET && csk->sk_family != AF_INET6) ||
+	    csk->sk_protocol != IPPROTO_TCP) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	/* Don't allow listeners or closed sockets */
+	if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);
+	if (!psock) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	psock->mux = mux;
+	psock->sk = csk;
+	psock->bpf_prog = prog;
+
+	err = strp_init(&psock->strp, csk, &cb);
+	if (err) {
+		kmem_cache_free(kcm_psockp, psock);
+		goto out;
+	}
+
+	write_lock_bh(&csk->sk_callback_lock);
+
+	/* Check if sk_user_data is aready by KCM or someone else.
+	 * Must be done under lock to prevent race conditions.
+	 */
+	if (csk->sk_user_data) {
+		write_unlock_bh(&csk->sk_callback_lock);
+		strp_stop(&psock->strp);
+		strp_done(&psock->strp);
+		kmem_cache_free(kcm_psockp, psock);
+		err = -EALREADY;
+		goto out;
+	}
+
+	psock->save_data_ready = csk->sk_data_ready;
+	psock->save_write_space = csk->sk_write_space;
+	psock->save_state_change = csk->sk_state_change;
+	csk->sk_user_data = psock;
+	csk->sk_data_ready = psock_data_ready;
+	csk->sk_write_space = psock_write_space;
+	csk->sk_state_change = psock_state_change;
+
+	write_unlock_bh(&csk->sk_callback_lock);
+
+	sock_hold(csk);
+
+	/* Finished initialization, now add the psock to the MUX. */
+	spin_lock_bh(&mux->lock);
+	head = &mux->psocks;
+	list_for_each_entry(tpsock, &mux->psocks, psock_list) {
+		if (tpsock->index != index)
+			break;
+		head = &tpsock->psock_list;
+		index++;
+	}
+
+	list_add(&psock->psock_list, head);
+	psock->index = index;
+
+	KCM_STATS_INCR(mux->stats.psock_attach);
+	mux->psocks_cnt++;
+	psock_now_avail(psock);
+	spin_unlock_bh(&mux->lock);
+
+	/* Schedule RX work in case there are already bytes queued */
+	strp_check_rcv(&psock->strp);
+
+out:
+	release_sock(csk);
+
+	return err;
+}
+
+static int kcm_attach_ioctl(struct socket *sock, struct kcm_attach *info)
+{
+	struct socket *csock;
+	struct bpf_prog *prog;
+	int err;
+
+	csock = sockfd_lookup(info->fd, &err);
+	if (!csock)
+		return -ENOENT;
+
+	prog = bpf_prog_get_type(info->bpf_fd, BPF_PROG_TYPE_SOCKET_FILTER);
+	if (IS_ERR(prog)) {
+		err = PTR_ERR(prog);
+		goto out;
+	}
+
+	err = kcm_attach(sock, csock, prog);
+	if (err) {
+		bpf_prog_put(prog);
+		goto out;
+	}
+
+	/* Keep reference on file also */
+
+	return 0;
+out:
+	fput(csock->file);
+	return err;
+}
+
+static void kcm_unattach(struct kcm_psock *psock)
+{
+	struct sock *csk = psock->sk;
+	struct kcm_mux *mux = psock->mux;
+
+	lock_sock(csk);
+
+	/* Stop getting callbacks from TCP socket. After this there should
+	 * be no way to reserve a kcm for this psock.
+	 */
+	write_lock_bh(&csk->sk_callback_lock);
+	csk->sk_user_data = NULL;
+	csk->sk_data_ready = psock->save_data_ready;
+	csk->sk_write_space = psock->save_write_space;
+	csk->sk_state_change = psock->save_state_change;
+	strp_stop(&psock->strp);
+
+	if (WARN_ON(psock->rx_kcm)) {
+		write_unlock_bh(&csk->sk_callback_lock);
+		release_sock(csk);
+		return;
+	}
+
+	spin_lock_bh(&mux->rx_lock);
+
+	/* Stop receiver activities. After this point psock should not be
+	 * able to get onto ready list either through callbacks or work.
+	 */
+	if (psock->ready_rx_msg) {
+		list_del(&psock->psock_ready_list);
+		kfree_skb(psock->ready_rx_msg);
+		psock->ready_rx_msg = NULL;
+		KCM_STATS_INCR(mux->stats.rx_ready_drops);
+	}
+
+	spin_unlock_bh(&mux->rx_lock);
+
+	write_unlock_bh(&csk->sk_callback_lock);
+
+	/* Call strp_done without sock lock */
+	release_sock(csk);
+	strp_done(&psock->strp);
+	lock_sock(csk);
+
+	bpf_prog_put(psock->bpf_prog);
+
+	spin_lock_bh(&mux->lock);
+
+	aggregate_psock_stats(&psock->stats, &mux->aggregate_psock_stats);
+	save_strp_stats(&psock->strp, &mux->aggregate_strp_stats);
+
+	KCM_STATS_INCR(mux->stats.psock_unattach);
+
+	if (psock->tx_kcm) {
+		/* psock was reserved.  Just mark it finished and we will clean
+		 * up in the kcm paths, we need kcm lock which can not be
+		 * acquired here.
+		 */
+		KCM_STATS_INCR(mux->stats.psock_unattach_rsvd);
+		spin_unlock_bh(&mux->lock);
+
+		/* We are unattaching a socket that is reserved. Abort the
+		 * socket since we may be out of sync in sending on it. We need
+		 * to do this without the mux lock.
+		 */
+		kcm_abort_tx_psock(psock, EPIPE, false);
+
+		spin_lock_bh(&mux->lock);
+		if (!psock->tx_kcm) {
+			/* psock now unreserved in window mux was unlocked */
+			goto no_reserved;
+		}
+		psock->done = 1;
+
+		/* Commit done before queuing work to process it */
+		smp_mb();
+
+		/* Queue tx work to make sure psock->done is handled */
+		queue_work(kcm_wq, &psock->tx_kcm->tx_work);
+		spin_unlock_bh(&mux->lock);
+	} else {
+no_reserved:
+		if (!psock->tx_stopped)
+			list_del(&psock->psock_avail_list);
+		list_del(&psock->psock_list);
+		mux->psocks_cnt--;
+		spin_unlock_bh(&mux->lock);
+
+		sock_put(csk);
+		fput(csk->sk_socket->file);
+		kmem_cache_free(kcm_psockp, psock);
+	}
+
+	release_sock(csk);
+}
+
+static int kcm_unattach_ioctl(struct socket *sock, struct kcm_unattach *info)
+{
+	struct kcm_sock *kcm = kcm_sk(sock->sk);
+	struct kcm_mux *mux = kcm->mux;
+	struct kcm_psock *psock;
+	struct socket *csock;
+	struct sock *csk;
+	int err;
+
+	csock = sockfd_lookup(info->fd, &err);
+	if (!csock)
+		return -ENOENT;
+
+	csk = csock->sk;
+	if (!csk) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = -ENOENT;
+
+	spin_lock_bh(&mux->lock);
+
+	list_for_each_entry(psock, &mux->psocks, psock_list) {
+		if (psock->sk != csk)
+			continue;
+
+		/* Found the matching psock */
+
+		if (psock->unattaching || WARN_ON(psock->done)) {
+			err = -EALREADY;
+			break;
+		}
+
+		psock->unattaching = 1;
+
+		spin_unlock_bh(&mux->lock);
+
+		/* Lower socket lock should already be held */
+		kcm_unattach(psock);
+
+		err = 0;
+		goto out;
+	}
+
+	spin_unlock_bh(&mux->lock);
+
+out:
+	fput(csock->file);
+	return err;
+}
+
+static struct proto kcm_proto = {
+	.name	= "KCM",
+	.owner	= THIS_MODULE,
+	.obj_size = sizeof(struct kcm_sock),
+};
+
+/* Clone a kcm socket. */
+static struct file *kcm_clone(struct socket *osock)
+{
+	struct socket *newsock;
+	struct sock *newsk;
+	struct file *file;
+
+	newsock = sock_alloc();
+	if (!newsock)
+		return ERR_PTR(-ENFILE);
+
+	newsock->type = osock->type;
+	newsock->ops = osock->ops;
+
+	__module_get(newsock->ops->owner);
+
+	newsk = sk_alloc(sock_net(osock->sk), PF_KCM, GFP_KERNEL,
+			 &kcm_proto, false);
+	if (!newsk) {
+		sock_release(newsock);
+		return ERR_PTR(-ENOMEM);
+	}
+	sock_init_data(newsock, newsk);
+	init_kcm_sock(kcm_sk(newsk), kcm_sk(osock->sk)->mux);
+
+	file = sock_alloc_file(newsock, 0, osock->sk->sk_prot_creator->name);
+	if (IS_ERR(file))
+		sock_release(newsock);
+
+	return file;
+}
+
+static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	int err;
+
+	switch (cmd) {
+	case SIOCKCMATTACH: {
+		struct kcm_attach info;
+
+		if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
+			return -EFAULT;
+
+		err = kcm_attach_ioctl(sock, &info);
+
+		break;
+	}
+	case SIOCKCMUNATTACH: {
+		struct kcm_unattach info;
+
+		if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
+			return -EFAULT;
+
+		err = kcm_unattach_ioctl(sock, &info);
+
+		break;
+	}
+	case SIOCKCMCLONE: {
+		struct kcm_clone info;
+		struct file *file;
+
+		info.fd = get_unused_fd_flags(0);
+		if (unlikely(info.fd < 0))
+			return info.fd;
+
+		file = kcm_clone(sock);
+		if (IS_ERR(file)) {
+			put_unused_fd(info.fd);
+			return PTR_ERR(file);
+		}
+		if (copy_to_user((void __user *)arg, &info,
+				 sizeof(info))) {
+			put_unused_fd(info.fd);
+			fput(file);
+			return -EFAULT;
+		}
+		fd_install(info.fd, file);
+		err = 0;
+		break;
+	}
+	default:
+		err = -ENOIOCTLCMD;
+		break;
+	}
+
+	return err;
+}
+
+static void free_mux(struct rcu_head *rcu)
+{
+	struct kcm_mux *mux = container_of(rcu,
+	    struct kcm_mux, rcu);
+
+	kmem_cache_free(kcm_muxp, mux);
+}
+
+static void release_mux(struct kcm_mux *mux)
+{
+	struct kcm_net *knet = mux->knet;
+	struct kcm_psock *psock, *tmp_psock;
+
+	/* Release psocks */
+	list_for_each_entry_safe(psock, tmp_psock,
+				 &mux->psocks, psock_list) {
+		if (!WARN_ON(psock->unattaching))
+			kcm_unattach(psock);
+	}
+
+	if (WARN_ON(mux->psocks_cnt))
+		return;
+
+	__skb_queue_purge(&mux->rx_hold_queue);
+
+	mutex_lock(&knet->mutex);
+	aggregate_mux_stats(&mux->stats, &knet->aggregate_mux_stats);
+	aggregate_psock_stats(&mux->aggregate_psock_stats,
+			      &knet->aggregate_psock_stats);
+	aggregate_strp_stats(&mux->aggregate_strp_stats,
+			     &knet->aggregate_strp_stats);
+	list_del_rcu(&mux->kcm_mux_list);
+	knet->count--;
+	mutex_unlock(&knet->mutex);
+
+	call_rcu(&mux->rcu, free_mux);
+}
+
+static void kcm_done(struct kcm_sock *kcm)
+{
+	struct kcm_mux *mux = kcm->mux;
+	struct sock *sk = &kcm->sk;
+	int socks_cnt;
+
+	spin_lock_bh(&mux->rx_lock);
+	if (kcm->rx_psock) {
+		/* Cleanup in unreserve_rx_kcm */
+		WARN_ON(kcm->done);
+		kcm->rx_disabled = 1;
+		kcm->done = 1;
+		spin_unlock_bh(&mux->rx_lock);
+		return;
+	}
+
+	if (kcm->rx_wait) {
+		list_del(&kcm->wait_rx_list);
+		kcm->rx_wait = false;
+	}
+	/* Move any pending receive messages to other kcm sockets */
+	requeue_rx_msgs(mux, &sk->sk_receive_queue);
+
+	spin_unlock_bh(&mux->rx_lock);
+
+	if (WARN_ON(sk_rmem_alloc_get(sk)))
+		return;
+
+	/* Detach from MUX */
+	spin_lock_bh(&mux->lock);
+
+	list_del(&kcm->kcm_sock_list);
+	mux->kcm_socks_cnt--;
+	socks_cnt = mux->kcm_socks_cnt;
+
+	spin_unlock_bh(&mux->lock);
+
+	if (!socks_cnt) {
+		/* We are done with the mux now. */
+		release_mux(mux);
+	}
+
+	WARN_ON(kcm->rx_wait);
+
+	sock_put(&kcm->sk);
+}
+
+/* Called by kcm_release to close a KCM socket.
+ * If this is the last KCM socket on the MUX, destroy the MUX.
+ */
+static int kcm_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct kcm_sock *kcm;
+	struct kcm_mux *mux;
+	struct kcm_psock *psock;
+
+	if (!sk)
+		return 0;
+
+	kcm = kcm_sk(sk);
+	mux = kcm->mux;
+
+	sock_orphan(sk);
+	kfree_skb(kcm->seq_skb);
+
+	lock_sock(sk);
+	/* Purge queue under lock to avoid race condition with tx_work trying
+	 * to act when queue is nonempty. If tx_work runs after this point
+	 * it will just return.
+	 */
+	__skb_queue_purge(&sk->sk_write_queue);
+
+	/* Set tx_stopped. This is checked when psock is bound to a kcm and we
+	 * get a writespace callback. This prevents further work being queued
+	 * from the callback (unbinding the psock occurs after canceling work.
+	 */
+	kcm->tx_stopped = 1;
+
+	release_sock(sk);
+
+	spin_lock_bh(&mux->lock);
+	if (kcm->tx_wait) {
+		/* Take of tx_wait list, after this point there should be no way
+		 * that a psock will be assigned to this kcm.
+		 */
+		list_del(&kcm->wait_psock_list);
+		kcm->tx_wait = false;
+	}
+	spin_unlock_bh(&mux->lock);
+
+	/* Cancel work. After this point there should be no outside references
+	 * to the kcm socket.
+	 */
+	cancel_work_sync(&kcm->tx_work);
+
+	lock_sock(sk);
+	psock = kcm->tx_psock;
+	if (psock) {
+		/* A psock was reserved, so we need to kill it since it
+		 * may already have some bytes queued from a message. We
+		 * need to do this after removing kcm from tx_wait list.
+		 */
+		kcm_abort_tx_psock(psock, EPIPE, false);
+		unreserve_psock(kcm);
+	}
+	release_sock(sk);
+
+	WARN_ON(kcm->tx_wait);
+	WARN_ON(kcm->tx_psock);
+
+	sock->sk = NULL;
+
+	kcm_done(kcm);
+
+	return 0;
+}
+
+static const struct proto_ops kcm_dgram_ops = {
+	.family =	PF_KCM,
+	.owner =	THIS_MODULE,
+	.release =	kcm_release,
+	.bind =		sock_no_bind,
+	.connect =	sock_no_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	sock_no_accept,
+	.getname =	sock_no_getname,
+	.poll =		datagram_poll,
+	.ioctl =	kcm_ioctl,
+	.listen =	sock_no_listen,
+	.shutdown =	sock_no_shutdown,
+	.setsockopt =	kcm_setsockopt,
+	.getsockopt =	kcm_getsockopt,
+	.sendmsg =	kcm_sendmsg,
+	.recvmsg =	kcm_recvmsg,
+	.mmap =		sock_no_mmap,
+	.sendpage =	kcm_sendpage,
+};
+
+static const struct proto_ops kcm_seqpacket_ops = {
+	.family =	PF_KCM,
+	.owner =	THIS_MODULE,
+	.release =	kcm_release,
+	.bind =		sock_no_bind,
+	.connect =	sock_no_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	sock_no_accept,
+	.getname =	sock_no_getname,
+	.poll =		datagram_poll,
+	.ioctl =	kcm_ioctl,
+	.listen =	sock_no_listen,
+	.shutdown =	sock_no_shutdown,
+	.setsockopt =	kcm_setsockopt,
+	.getsockopt =	kcm_getsockopt,
+	.sendmsg =	kcm_sendmsg,
+	.recvmsg =	kcm_recvmsg,
+	.mmap =		sock_no_mmap,
+	.sendpage =	kcm_sendpage,
+	.splice_read =	kcm_splice_read,
+};
+
+/* Create proto operation for kcm sockets */
+static int kcm_create(struct net *net, struct socket *sock,
+		      int protocol, int kern)
+{
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+	struct sock *sk;
+	struct kcm_mux *mux;
+
+	switch (sock->type) {
+	case SOCK_DGRAM:
+		sock->ops = &kcm_dgram_ops;
+		break;
+	case SOCK_SEQPACKET:
+		sock->ops = &kcm_seqpacket_ops;
+		break;
+	default:
+		return -ESOCKTNOSUPPORT;
+	}
+
+	if (protocol != KCMPROTO_CONNECTED)
+		return -EPROTONOSUPPORT;
+
+	sk = sk_alloc(net, PF_KCM, GFP_KERNEL, &kcm_proto, kern);
+	if (!sk)
+		return -ENOMEM;
+
+	/* Allocate a kcm mux, shared between KCM sockets */
+	mux = kmem_cache_zalloc(kcm_muxp, GFP_KERNEL);
+	if (!mux) {
+		sk_free(sk);
+		return -ENOMEM;
+	}
+
+	spin_lock_init(&mux->lock);
+	spin_lock_init(&mux->rx_lock);
+	INIT_LIST_HEAD(&mux->kcm_socks);
+	INIT_LIST_HEAD(&mux->kcm_rx_waiters);
+	INIT_LIST_HEAD(&mux->kcm_tx_waiters);
+
+	INIT_LIST_HEAD(&mux->psocks);
+	INIT_LIST_HEAD(&mux->psocks_ready);
+	INIT_LIST_HEAD(&mux->psocks_avail);
+
+	mux->knet = knet;
+
+	/* Add new MUX to list */
+	mutex_lock(&knet->mutex);
+	list_add_rcu(&mux->kcm_mux_list, &knet->mux_list);
+	knet->count++;
+	mutex_unlock(&knet->mutex);
+
+	skb_queue_head_init(&mux->rx_hold_queue);
+
+	/* Init KCM socket */
+	sock_init_data(sock, sk);
+	init_kcm_sock(kcm_sk(sk), mux);
+
+	return 0;
+}
+
+static const struct net_proto_family kcm_family_ops = {
+	.family = PF_KCM,
+	.create = kcm_create,
+	.owner  = THIS_MODULE,
+};
+
+static __net_init int kcm_init_net(struct net *net)
+{
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+
+	INIT_LIST_HEAD_RCU(&knet->mux_list);
+	mutex_init(&knet->mutex);
+
+	return 0;
+}
+
+static __net_exit void kcm_exit_net(struct net *net)
+{
+	struct kcm_net *knet = net_generic(net, kcm_net_id);
+
+	/* All KCM sockets should be closed at this point, which should mean
+	 * that all multiplexors and psocks have been destroyed.
+	 */
+	WARN_ON(!list_empty(&knet->mux_list));
+}
+
+static struct pernet_operations kcm_net_ops = {
+	.init = kcm_init_net,
+	.exit = kcm_exit_net,
+	.id   = &kcm_net_id,
+	.size = sizeof(struct kcm_net),
+};
+
+static int __init kcm_init(void)
+{
+	int err = -ENOMEM;
+
+	kcm_muxp = kmem_cache_create("kcm_mux_cache",
+				     sizeof(struct kcm_mux), 0,
+				     SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+	if (!kcm_muxp)
+		goto fail;
+
+	kcm_psockp = kmem_cache_create("kcm_psock_cache",
+				       sizeof(struct kcm_psock), 0,
+					SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+	if (!kcm_psockp)
+		goto fail;
+
+	kcm_wq = create_singlethread_workqueue("kkcmd");
+	if (!kcm_wq)
+		goto fail;
+
+	err = proto_register(&kcm_proto, 1);
+	if (err)
+		goto fail;
+
+	err = register_pernet_device(&kcm_net_ops);
+	if (err)
+		goto net_ops_fail;
+
+	err = sock_register(&kcm_family_ops);
+	if (err)
+		goto sock_register_fail;
+
+	err = kcm_proc_init();
+	if (err)
+		goto proc_init_fail;
+
+	return 0;
+
+proc_init_fail:
+	sock_unregister(PF_KCM);
+
+sock_register_fail:
+	unregister_pernet_device(&kcm_net_ops);
+
+net_ops_fail:
+	proto_unregister(&kcm_proto);
+
+fail:
+	kmem_cache_destroy(kcm_muxp);
+	kmem_cache_destroy(kcm_psockp);
+
+	if (kcm_wq)
+		destroy_workqueue(kcm_wq);
+
+	return err;
+}
+
+static void __exit kcm_exit(void)
+{
+	kcm_proc_exit();
+	sock_unregister(PF_KCM);
+	unregister_pernet_device(&kcm_net_ops);
+	proto_unregister(&kcm_proto);
+	destroy_workqueue(kcm_wq);
+
+	kmem_cache_destroy(kcm_muxp);
+	kmem_cache_destroy(kcm_psockp);
+}
+
+module_init(kcm_init);
+module_exit(kcm_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_NETPROTO(PF_KCM);
+