Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 2053 insertions, 0 deletions

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
new file mode 100644
index 000000000..72f34f96d
--- /dev/null
+++ b/fs/dlm/lowcomms.c
@@ -0,0 +1,2053 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2009 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+/*
+ * lowcomms.c
+ *
+ * This is the "low-level" comms layer.
+ *
+ * It is responsible for sending/receiving messages
+ * from other nodes in the cluster.
+ *
+ * Cluster nodes are referred to by their nodeids. nodeids are
+ * simply 32 bit numbers to the locking module - if they need to
+ * be expanded for the cluster infrastructure then that is its
+ * responsibility. It is this layer's
+ * responsibility to resolve these into IP address or
+ * whatever it needs for inter-node communication.
+ *
+ * The comms level is two kernel threads that deal mainly with
+ * the receiving of messages from other nodes and passing them
+ * up to the mid-level comms layer (which understands the
+ * message format) for execution by the locking core, and
+ * a send thread which does all the setting up of connections
+ * to remote nodes and the sending of data. Threads are not allowed
+ * to send their own data because it may cause them to wait in times
+ * of high load. Also, this way, the sending thread can collect together
+ * messages bound for one node and send them in one block.
+ *
+ * lowcomms will choose to use either TCP or SCTP as its transport layer
+ * depending on the configuration variable 'protocol'. This should be set
+ * to 0 (default) for TCP or 1 for SCTP. It should be configured using a
+ * cluster-wide mechanism as it must be the same on all nodes of the cluster
+ * for the DLM to function.
+ *
+ */
+
+#include <asm/ioctls.h>
+#include <net/sock.h>
+#include <net/tcp.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/mutex.h>
+#include <linux/sctp.h>
+#include <linux/slab.h>
+#include <net/sctp/sctp.h>
+#include <net/ipv6.h>
+
+#include <trace/events/dlm.h>
+
+#include "dlm_internal.h"
+#include "lowcomms.h"
+#include "midcomms.h"
+#include "memory.h"
+#include "config.h"
+
+#define NEEDED_RMEM (4*1024*1024)
+
+/* Number of messages to send before rescheduling */
+#define MAX_SEND_MSG_COUNT 25
+#define DLM_SHUTDOWN_WAIT_TIMEOUT msecs_to_jiffies(10000)
+
+struct connection {
+	struct socket *sock;	/* NULL if not connected */
+	uint32_t nodeid;	/* So we know who we are in the list */
+	struct mutex sock_mutex;
+	unsigned long flags;
+#define CF_READ_PENDING 1
+#define CF_WRITE_PENDING 2
+#define CF_INIT_PENDING 4
+#define CF_IS_OTHERCON 5
+#define CF_CLOSE 6
+#define CF_APP_LIMITED 7
+#define CF_CLOSING 8
+#define CF_SHUTDOWN 9
+#define CF_CONNECTED 10
+#define CF_RECONNECT 11
+#define CF_DELAY_CONNECT 12
+#define CF_EOF 13
+	struct list_head writequeue;  /* List of outgoing writequeue_entries */
+	spinlock_t writequeue_lock;
+	atomic_t writequeue_cnt;
+	int retries;
+#define MAX_CONNECT_RETRIES 3
+	struct hlist_node list;
+	struct connection *othercon;
+	struct connection *sendcon;
+	struct work_struct rwork; /* Receive workqueue */
+	struct work_struct swork; /* Send workqueue */
+	wait_queue_head_t shutdown_wait; /* wait for graceful shutdown */
+	unsigned char *rx_buf;
+	int rx_buflen;
+	int rx_leftover;
+	struct rcu_head rcu;
+};
+#define sock2con(x) ((struct connection *)(x)->sk_user_data)
+
+struct listen_connection {
+	struct socket *sock;
+	struct work_struct rwork;
+};
+
+#define DLM_WQ_REMAIN_BYTES(e) (PAGE_SIZE - e->end)
+#define DLM_WQ_LENGTH_BYTES(e) (e->end - e->offset)
+
+/* An entry waiting to be sent */
+struct writequeue_entry {
+	struct list_head list;
+	struct page *page;
+	int offset;
+	int len;
+	int end;
+	int users;
+	bool dirty;
+	struct connection *con;
+	struct list_head msgs;
+	struct kref ref;
+};
+
+struct dlm_msg {
+	struct writequeue_entry *entry;
+	struct dlm_msg *orig_msg;
+	bool retransmit;
+	void *ppc;
+	int len;
+	int idx; /* new()/commit() idx exchange */
+
+	struct list_head list;
+	struct kref ref;
+};
+
+struct dlm_node_addr {
+	struct list_head list;
+	int nodeid;
+	int mark;
+	int addr_count;
+	int curr_addr_index;
+	struct sockaddr_storage *addr[DLM_MAX_ADDR_COUNT];
+};
+
+struct dlm_proto_ops {
+	bool try_new_addr;
+	const char *name;
+	int proto;
+
+	int (*connect)(struct connection *con, struct socket *sock,
+		       struct sockaddr *addr, int addr_len);
+	void (*sockopts)(struct socket *sock);
+	int (*bind)(struct socket *sock);
+	int (*listen_validate)(void);
+	void (*listen_sockopts)(struct socket *sock);
+	int (*listen_bind)(struct socket *sock);
+	/* What to do to shutdown */
+	void (*shutdown_action)(struct connection *con);
+	/* What to do to eof check */
+	bool (*eof_condition)(struct connection *con);
+};
+
+static struct listen_sock_callbacks {
+	void (*sk_error_report)(struct sock *);
+	void (*sk_data_ready)(struct sock *);
+	void (*sk_state_change)(struct sock *);
+	void (*sk_write_space)(struct sock *);
+} listen_sock;
+
+static LIST_HEAD(dlm_node_addrs);
+static DEFINE_SPINLOCK(dlm_node_addrs_spin);
+
+static struct listen_connection listen_con;
+static struct sockaddr_storage *dlm_local_addr[DLM_MAX_ADDR_COUNT];
+static int dlm_local_count;
+int dlm_allow_conn;
+
+/* Work queues */
+static struct workqueue_struct *recv_workqueue;
+static struct workqueue_struct *send_workqueue;
+
+static struct hlist_head connection_hash[CONN_HASH_SIZE];
+static DEFINE_SPINLOCK(connections_lock);
+DEFINE_STATIC_SRCU(connections_srcu);
+
+static const struct dlm_proto_ops *dlm_proto_ops;
+
+static void process_recv_sockets(struct work_struct *work);
+static void process_send_sockets(struct work_struct *work);
+
+static void writequeue_entry_ctor(void *data)
+{
+	struct writequeue_entry *entry = data;
+
+	INIT_LIST_HEAD(&entry->msgs);
+}
+
+struct kmem_cache *dlm_lowcomms_writequeue_cache_create(void)
+{
+	return kmem_cache_create("dlm_writequeue", sizeof(struct writequeue_entry),
+				 0, 0, writequeue_entry_ctor);
+}
+
+struct kmem_cache *dlm_lowcomms_msg_cache_create(void)
+{
+	return kmem_cache_create("dlm_msg", sizeof(struct dlm_msg), 0, 0, NULL);
+}
+
+/* need to held writequeue_lock */
+static struct writequeue_entry *con_next_wq(struct connection *con)
+{
+	struct writequeue_entry *e;
+
+	if (list_empty(&con->writequeue))
+		return NULL;
+
+	e = list_first_entry(&con->writequeue, struct writequeue_entry,
+			     list);
+	/* if len is zero nothing is to send, if there are users filling
+	 * buffers we wait until the users are done so we can send more.
+	 */
+	if (e->users || e->len == 0)
+		return NULL;
+
+	return e;
+}
+
+static struct connection *__find_con(int nodeid, int r)
+{
+	struct connection *con;
+
+	hlist_for_each_entry_rcu(con, &connection_hash[r], list) {
+		if (con->nodeid == nodeid)
+			return con;
+	}
+
+	return NULL;
+}
+
+static bool tcp_eof_condition(struct connection *con)
+{
+	return atomic_read(&con->writequeue_cnt);
+}
+
+static int dlm_con_init(struct connection *con, int nodeid)
+{
+	con->rx_buflen = dlm_config.ci_buffer_size;
+	con->rx_buf = kmalloc(con->rx_buflen, GFP_NOFS);
+	if (!con->rx_buf)
+		return -ENOMEM;
+
+	con->nodeid = nodeid;
+	mutex_init(&con->sock_mutex);
+	INIT_LIST_HEAD(&con->writequeue);
+	spin_lock_init(&con->writequeue_lock);
+	atomic_set(&con->writequeue_cnt, 0);
+	INIT_WORK(&con->swork, process_send_sockets);
+	INIT_WORK(&con->rwork, process_recv_sockets);
+	init_waitqueue_head(&con->shutdown_wait);
+
+	return 0;
+}
+
+/*
+ * If 'allocation' is zero then we don't attempt to create a new
+ * connection structure for this node.
+ */
+static struct connection *nodeid2con(int nodeid, gfp_t alloc)
+{
+	struct connection *con, *tmp;
+	int r, ret;
+
+	r = nodeid_hash(nodeid);
+	con = __find_con(nodeid, r);
+	if (con || !alloc)
+		return con;
+
+	con = kzalloc(sizeof(*con), alloc);
+	if (!con)
+		return NULL;
+
+	ret = dlm_con_init(con, nodeid);
+	if (ret) {
+		kfree(con);
+		return NULL;
+	}
+
+	spin_lock(&connections_lock);
+	/* Because multiple workqueues/threads calls this function it can
+	 * race on multiple cpu's. Instead of locking hot path __find_con()
+	 * we just check in rare cases of recently added nodes again
+	 * under protection of connections_lock. If this is the case we
+	 * abort our connection creation and return the existing connection.
+	 */
+	tmp = __find_con(nodeid, r);
+	if (tmp) {
+		spin_unlock(&connections_lock);
+		kfree(con->rx_buf);
+		kfree(con);
+		return tmp;
+	}
+
+	hlist_add_head_rcu(&con->list, &connection_hash[r]);
+	spin_unlock(&connections_lock);
+
+	return con;
+}
+
+/* Loop round all connections */
+static void foreach_conn(void (*conn_func)(struct connection *c))
+{
+	int i;
+	struct connection *con;
+
+	for (i = 0; i < CONN_HASH_SIZE; i++) {
+		hlist_for_each_entry_rcu(con, &connection_hash[i], list)
+			conn_func(con);
+	}
+}
+
+static struct dlm_node_addr *find_node_addr(int nodeid)
+{
+	struct dlm_node_addr *na;
+
+	list_for_each_entry(na, &dlm_node_addrs, list) {
+		if (na->nodeid == nodeid)
+			return na;
+	}
+	return NULL;
+}
+
+static int addr_compare(const struct sockaddr_storage *x,
+			const struct sockaddr_storage *y)
+{
+	switch (x->ss_family) {
+	case AF_INET: {
+		struct sockaddr_in *sinx = (struct sockaddr_in *)x;
+		struct sockaddr_in *siny = (struct sockaddr_in *)y;
+		if (sinx->sin_addr.s_addr != siny->sin_addr.s_addr)
+			return 0;
+		if (sinx->sin_port != siny->sin_port)
+			return 0;
+		break;
+	}
+	case AF_INET6: {
+		struct sockaddr_in6 *sinx = (struct sockaddr_in6 *)x;
+		struct sockaddr_in6 *siny = (struct sockaddr_in6 *)y;
+		if (!ipv6_addr_equal(&sinx->sin6_addr, &siny->sin6_addr))
+			return 0;
+		if (sinx->sin6_port != siny->sin6_port)
+			return 0;
+		break;
+	}
+	default:
+		return 0;
+	}
+	return 1;
+}
+
+static int nodeid_to_addr(int nodeid, struct sockaddr_storage *sas_out,
+			  struct sockaddr *sa_out, bool try_new_addr,
+			  unsigned int *mark)
+{
+	struct sockaddr_storage sas;
+	struct dlm_node_addr *na;
+
+	if (!dlm_local_count)
+		return -1;
+
+	spin_lock(&dlm_node_addrs_spin);
+	na = find_node_addr(nodeid);
+	if (na && na->addr_count) {
+		memcpy(&sas, na->addr[na->curr_addr_index],
+		       sizeof(struct sockaddr_storage));
+
+		if (try_new_addr) {
+			na->curr_addr_index++;
+			if (na->curr_addr_index == na->addr_count)
+				na->curr_addr_index = 0;
+		}
+	}
+	spin_unlock(&dlm_node_addrs_spin);
+
+	if (!na)
+		return -EEXIST;
+
+	if (!na->addr_count)
+		return -ENOENT;
+
+	*mark = na->mark;
+
+	if (sas_out)
+		memcpy(sas_out, &sas, sizeof(struct sockaddr_storage));
+
+	if (!sa_out)
+		return 0;
+
+	if (dlm_local_addr[0]->ss_family == AF_INET) {
+		struct sockaddr_in *in4  = (struct sockaddr_in *) &sas;
+		struct sockaddr_in *ret4 = (struct sockaddr_in *) sa_out;
+		ret4->sin_addr.s_addr = in4->sin_addr.s_addr;
+	} else {
+		struct sockaddr_in6 *in6  = (struct sockaddr_in6 *) &sas;
+		struct sockaddr_in6 *ret6 = (struct sockaddr_in6 *) sa_out;
+		ret6->sin6_addr = in6->sin6_addr;
+	}
+
+	return 0;
+}
+
+static int addr_to_nodeid(struct sockaddr_storage *addr, int *nodeid,
+			  unsigned int *mark)
+{
+	struct dlm_node_addr *na;
+	int rv = -EEXIST;
+	int addr_i;
+
+	spin_lock(&dlm_node_addrs_spin);
+	list_for_each_entry(na, &dlm_node_addrs, list) {
+		if (!na->addr_count)
+			continue;
+
+		for (addr_i = 0; addr_i < na->addr_count; addr_i++) {
+			if (addr_compare(na->addr[addr_i], addr)) {
+				*nodeid = na->nodeid;
+				*mark = na->mark;
+				rv = 0;
+				goto unlock;
+			}
+		}
+	}
+unlock:
+	spin_unlock(&dlm_node_addrs_spin);
+	return rv;
+}
+
+/* caller need to held dlm_node_addrs_spin lock */
+static bool dlm_lowcomms_na_has_addr(const struct dlm_node_addr *na,
+				     const struct sockaddr_storage *addr)
+{
+	int i;
+
+	for (i = 0; i < na->addr_count; i++) {
+		if (addr_compare(na->addr[i], addr))
+			return true;
+	}
+
+	return false;
+}
+
+int dlm_lowcomms_addr(int nodeid, struct sockaddr_storage *addr, int len)
+{
+	struct sockaddr_storage *new_addr;
+	struct dlm_node_addr *new_node, *na;
+	bool ret;
+
+	new_node = kzalloc(sizeof(struct dlm_node_addr), GFP_NOFS);
+	if (!new_node)
+		return -ENOMEM;
+
+	new_addr = kzalloc(sizeof(struct sockaddr_storage), GFP_NOFS);
+	if (!new_addr) {
+		kfree(new_node);
+		return -ENOMEM;
+	}
+
+	memcpy(new_addr, addr, len);
+
+	spin_lock(&dlm_node_addrs_spin);
+	na = find_node_addr(nodeid);
+	if (!na) {
+		new_node->nodeid = nodeid;
+		new_node->addr[0] = new_addr;
+		new_node->addr_count = 1;
+		new_node->mark = dlm_config.ci_mark;
+		list_add(&new_node->list, &dlm_node_addrs);
+		spin_unlock(&dlm_node_addrs_spin);
+		return 0;
+	}
+
+	ret = dlm_lowcomms_na_has_addr(na, addr);
+	if (ret) {
+		spin_unlock(&dlm_node_addrs_spin);
+		kfree(new_addr);
+		kfree(new_node);
+		return -EEXIST;
+	}
+
+	if (na->addr_count >= DLM_MAX_ADDR_COUNT) {
+		spin_unlock(&dlm_node_addrs_spin);
+		kfree(new_addr);
+		kfree(new_node);
+		return -ENOSPC;
+	}
+
+	na->addr[na->addr_count++] = new_addr;
+	spin_unlock(&dlm_node_addrs_spin);
+	kfree(new_node);
+	return 0;
+}
+
+/* Data available on socket or listen socket received a connect */
+static void lowcomms_data_ready(struct sock *sk)
+{
+	struct connection *con;
+
+	con = sock2con(sk);
+	if (con && !test_and_set_bit(CF_READ_PENDING, &con->flags))
+		queue_work(recv_workqueue, &con->rwork);
+}
+
+static void lowcomms_listen_data_ready(struct sock *sk)
+{
+	if (!dlm_allow_conn)
+		return;
+
+	queue_work(recv_workqueue, &listen_con.rwork);
+}
+
+static void lowcomms_write_space(struct sock *sk)
+{
+	struct connection *con;
+
+	con = sock2con(sk);
+	if (!con)
+		return;
+
+	if (!test_and_set_bit(CF_CONNECTED, &con->flags)) {
+		log_print("connected to node %d", con->nodeid);
+		queue_work(send_workqueue, &con->swork);
+		return;
+	}
+
+	clear_bit(SOCK_NOSPACE, &con->sock->flags);
+
+	if (test_and_clear_bit(CF_APP_LIMITED, &con->flags)) {
+		con->sock->sk->sk_write_pending--;
+		clear_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags);
+	}
+
+	queue_work(send_workqueue, &con->swork);
+}
+
+static inline void lowcomms_connect_sock(struct connection *con)
+{
+	if (test_bit(CF_CLOSE, &con->flags))
+		return;
+	queue_work(send_workqueue, &con->swork);
+	cond_resched();
+}
+
+static void lowcomms_state_change(struct sock *sk)
+{
+	/* SCTP layer is not calling sk_data_ready when the connection
+	 * is done, so we catch the signal through here. Also, it
+	 * doesn't switch socket state when entering shutdown, so we
+	 * skip the write in that case.
+	 */
+	if (sk->sk_shutdown) {
+		if (sk->sk_shutdown == RCV_SHUTDOWN)
+			lowcomms_data_ready(sk);
+	} else if (sk->sk_state == TCP_ESTABLISHED) {
+		lowcomms_write_space(sk);
+	}
+}
+
+int dlm_lowcomms_connect_node(int nodeid)
+{
+	struct connection *con;
+	int idx;
+
+	if (nodeid == dlm_our_nodeid())
+		return 0;
+
+	idx = srcu_read_lock(&connections_srcu);
+	con = nodeid2con(nodeid, GFP_NOFS);
+	if (!con) {
+		srcu_read_unlock(&connections_srcu, idx);
+		return -ENOMEM;
+	}
+
+	lowcomms_connect_sock(con);
+	srcu_read_unlock(&connections_srcu, idx);
+
+	return 0;
+}
+
+int dlm_lowcomms_nodes_set_mark(int nodeid, unsigned int mark)
+{
+	struct dlm_node_addr *na;
+
+	spin_lock(&dlm_node_addrs_spin);
+	na = find_node_addr(nodeid);
+	if (!na) {
+		spin_unlock(&dlm_node_addrs_spin);
+		return -ENOENT;
+	}
+
+	na->mark = mark;
+	spin_unlock(&dlm_node_addrs_spin);
+
+	return 0;
+}
+
+static void lowcomms_error_report(struct sock *sk)
+{
+	struct connection *con;
+	void (*orig_report)(struct sock *) = NULL;
+	struct inet_sock *inet;
+
+	con = sock2con(sk);
+	if (con == NULL)
+		goto out;
+
+	orig_report = listen_sock.sk_error_report;
+
+	inet = inet_sk(sk);
+	switch (sk->sk_family) {
+	case AF_INET:
+		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
+				   "sending to node %d at %pI4, dport %d, "
+				   "sk_err=%d/%d\n", dlm_our_nodeid(),
+				   con->nodeid, &inet->inet_daddr,
+				   ntohs(inet->inet_dport), sk->sk_err,
+				   sk->sk_err_soft);
+		break;
+#if IS_ENABLED(CONFIG_IPV6)
+	case AF_INET6:
+		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
+				   "sending to node %d at %pI6c, "
+				   "dport %d, sk_err=%d/%d\n", dlm_our_nodeid(),
+				   con->nodeid, &sk->sk_v6_daddr,
+				   ntohs(inet->inet_dport), sk->sk_err,
+				   sk->sk_err_soft);
+		break;
+#endif
+	default:
+		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
+				   "invalid socket family %d set, "
+				   "sk_err=%d/%d\n", dlm_our_nodeid(),
+				   sk->sk_family, sk->sk_err, sk->sk_err_soft);
+		goto out;
+	}
+
+	/* below sendcon only handling */
+	if (test_bit(CF_IS_OTHERCON, &con->flags))
+		con = con->sendcon;
+
+	switch (sk->sk_err) {
+	case ECONNREFUSED:
+		set_bit(CF_DELAY_CONNECT, &con->flags);
+		break;
+	default:
+		break;
+	}
+
+	if (!test_and_set_bit(CF_RECONNECT, &con->flags))
+		queue_work(send_workqueue, &con->swork);
+
+out:
+	if (orig_report)
+		orig_report(sk);
+}
+
+/* Note: sk_callback_lock must be locked before calling this function. */
+static void save_listen_callbacks(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	listen_sock.sk_data_ready = sk->sk_data_ready;
+	listen_sock.sk_state_change = sk->sk_state_change;
+	listen_sock.sk_write_space = sk->sk_write_space;
+	listen_sock.sk_error_report = sk->sk_error_report;
+}
+
+static void restore_callbacks(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	lock_sock(sk);
+	sk->sk_user_data = NULL;
+	sk->sk_data_ready = listen_sock.sk_data_ready;
+	sk->sk_state_change = listen_sock.sk_state_change;
+	sk->sk_write_space = listen_sock.sk_write_space;
+	sk->sk_error_report = listen_sock.sk_error_report;
+	release_sock(sk);
+}
+
+static void add_listen_sock(struct socket *sock, struct listen_connection *con)
+{
+	struct sock *sk = sock->sk;
+
+	lock_sock(sk);
+	save_listen_callbacks(sock);
+	con->sock = sock;
+
+	sk->sk_user_data = con;
+	sk->sk_allocation = GFP_NOFS;
+	/* Install a data_ready callback */
+	sk->sk_data_ready = lowcomms_listen_data_ready;
+	release_sock(sk);
+}
+
+/* Make a socket active */
+static void add_sock(struct socket *sock, struct connection *con)
+{
+	struct sock *sk = sock->sk;
+
+	lock_sock(sk);
+	con->sock = sock;
+
+	sk->sk_user_data = con;
+	/* Install a data_ready callback */
+	sk->sk_data_ready = lowcomms_data_ready;
+	sk->sk_write_space = lowcomms_write_space;
+	sk->sk_state_change = lowcomms_state_change;
+	sk->sk_allocation = GFP_NOFS;
+	sk->sk_error_report = lowcomms_error_report;
+	release_sock(sk);
+}
+
+/* Add the port number to an IPv6 or 4 sockaddr and return the address
+   length */
+static void make_sockaddr(struct sockaddr_storage *saddr, uint16_t port,
+			  int *addr_len)
+{
+	saddr->ss_family =  dlm_local_addr[0]->ss_family;
+	if (saddr->ss_family == AF_INET) {
+		struct sockaddr_in *in4_addr = (struct sockaddr_in *)saddr;
+		in4_addr->sin_port = cpu_to_be16(port);
+		*addr_len = sizeof(struct sockaddr_in);
+		memset(&in4_addr->sin_zero, 0, sizeof(in4_addr->sin_zero));
+	} else {
+		struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)saddr;
+		in6_addr->sin6_port = cpu_to_be16(port);
+		*addr_len = sizeof(struct sockaddr_in6);
+	}
+	memset((char *)saddr + *addr_len, 0, sizeof(struct sockaddr_storage) - *addr_len);
+}
+
+static void dlm_page_release(struct kref *kref)
+{
+	struct writequeue_entry *e = container_of(kref, struct writequeue_entry,
+						  ref);
+
+	__free_page(e->page);
+	dlm_free_writequeue(e);
+}
+
+static void dlm_msg_release(struct kref *kref)
+{
+	struct dlm_msg *msg = container_of(kref, struct dlm_msg, ref);
+
+	kref_put(&msg->entry->ref, dlm_page_release);
+	dlm_free_msg(msg);
+}
+
+static void free_entry(struct writequeue_entry *e)
+{
+	struct dlm_msg *msg, *tmp;
+
+	list_for_each_entry_safe(msg, tmp, &e->msgs, list) {
+		if (msg->orig_msg) {
+			msg->orig_msg->retransmit = false;
+			kref_put(&msg->orig_msg->ref, dlm_msg_release);
+		}
+
+		list_del(&msg->list);
+		kref_put(&msg->ref, dlm_msg_release);
+	}
+
+	list_del(&e->list);
+	atomic_dec(&e->con->writequeue_cnt);
+	kref_put(&e->ref, dlm_page_release);
+}
+
+static void dlm_close_sock(struct socket **sock)
+{
+	if (*sock) {
+		restore_callbacks(*sock);
+		sock_release(*sock);
+		*sock = NULL;
+	}
+}
+
+/* Close a remote connection and tidy up */
+static void close_connection(struct connection *con, bool and_other,
+			     bool tx, bool rx)
+{
+	bool closing = test_and_set_bit(CF_CLOSING, &con->flags);
+	struct writequeue_entry *e;
+
+	if (tx && !closing && cancel_work_sync(&con->swork)) {
+		log_print("canceled swork for node %d", con->nodeid);
+		clear_bit(CF_WRITE_PENDING, &con->flags);
+	}
+	if (rx && !closing && cancel_work_sync(&con->rwork)) {
+		log_print("canceled rwork for node %d", con->nodeid);
+		clear_bit(CF_READ_PENDING, &con->flags);
+	}
+
+	mutex_lock(&con->sock_mutex);
+	dlm_close_sock(&con->sock);
+
+	if (con->othercon && and_other) {
+		/* Will only re-enter once. */
+		close_connection(con->othercon, false, tx, rx);
+	}
+
+	/* if we send a writequeue entry only a half way, we drop the
+	 * whole entry because reconnection and that we not start of the
+	 * middle of a msg which will confuse the other end.
+	 *
+	 * we can always drop messages because retransmits, but what we
+	 * cannot allow is to transmit half messages which may be processed
+	 * at the other side.
+	 *
+	 * our policy is to start on a clean state when disconnects, we don't
+	 * know what's send/received on transport layer in this case.
+	 */
+	spin_lock(&con->writequeue_lock);
+	if (!list_empty(&con->writequeue)) {
+		e = list_first_entry(&con->writequeue, struct writequeue_entry,
+				     list);
+		if (e->dirty)
+			free_entry(e);
+	}
+	spin_unlock(&con->writequeue_lock);
+
+	con->rx_leftover = 0;
+	con->retries = 0;
+	clear_bit(CF_APP_LIMITED, &con->flags);
+	clear_bit(CF_CONNECTED, &con->flags);
+	clear_bit(CF_DELAY_CONNECT, &con->flags);
+	clear_bit(CF_RECONNECT, &con->flags);
+	clear_bit(CF_EOF, &con->flags);
+	mutex_unlock(&con->sock_mutex);
+	clear_bit(CF_CLOSING, &con->flags);
+}
+
+static void shutdown_connection(struct connection *con)
+{
+	int ret;
+
+	flush_work(&con->swork);
+
+	mutex_lock(&con->sock_mutex);
+	/* nothing to shutdown */
+	if (!con->sock) {
+		mutex_unlock(&con->sock_mutex);
+		return;
+	}
+
+	set_bit(CF_SHUTDOWN, &con->flags);
+	ret = kernel_sock_shutdown(con->sock, SHUT_WR);
+	mutex_unlock(&con->sock_mutex);
+	if (ret) {
+		log_print("Connection %p failed to shutdown: %d will force close",
+			  con, ret);
+		goto force_close;
+	} else {
+		ret = wait_event_timeout(con->shutdown_wait,
+					 !test_bit(CF_SHUTDOWN, &con->flags),
+					 DLM_SHUTDOWN_WAIT_TIMEOUT);
+		if (ret == 0) {
+			log_print("Connection %p shutdown timed out, will force close",
+				  con);
+			goto force_close;
+		}
+	}
+
+	return;
+
+force_close:
+	clear_bit(CF_SHUTDOWN, &con->flags);
+	close_connection(con, false, true, true);
+}
+
+static void dlm_tcp_shutdown(struct connection *con)
+{
+	if (con->othercon)
+		shutdown_connection(con->othercon);
+	shutdown_connection(con);
+}
+
+static int con_realloc_receive_buf(struct connection *con, int newlen)
+{
+	unsigned char *newbuf;
+
+	newbuf = kmalloc(newlen, GFP_NOFS);
+	if (!newbuf)
+		return -ENOMEM;
+
+	/* copy any leftover from last receive */
+	if (con->rx_leftover)
+		memmove(newbuf, con->rx_buf, con->rx_leftover);
+
+	/* swap to new buffer space */
+	kfree(con->rx_buf);
+	con->rx_buflen = newlen;
+	con->rx_buf = newbuf;
+
+	return 0;
+}
+
+/* Data received from remote end */
+static int receive_from_sock(struct connection *con)
+{
+	struct msghdr msg;
+	struct kvec iov;
+	int ret, buflen;
+
+	mutex_lock(&con->sock_mutex);
+
+	if (con->sock == NULL) {
+		ret = -EAGAIN;
+		goto out_close;
+	}
+
+	/* realloc if we get new buffer size to read out */
+	buflen = dlm_config.ci_buffer_size;
+	if (con->rx_buflen != buflen && con->rx_leftover <= buflen) {
+		ret = con_realloc_receive_buf(con, buflen);
+		if (ret < 0)
+			goto out_resched;
+	}
+
+	for (;;) {
+		/* calculate new buffer parameter regarding last receive and
+		 * possible leftover bytes
+		 */
+		iov.iov_base = con->rx_buf + con->rx_leftover;
+		iov.iov_len = con->rx_buflen - con->rx_leftover;
+
+		memset(&msg, 0, sizeof(msg));
+		msg.msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
+		ret = kernel_recvmsg(con->sock, &msg, &iov, 1, iov.iov_len,
+				     msg.msg_flags);
+		trace_dlm_recv(con->nodeid, ret);
+		if (ret == -EAGAIN)
+			break;
+		else if (ret <= 0)
+			goto out_close;
+
+		/* new buflen according readed bytes and leftover from last receive */
+		buflen = ret + con->rx_leftover;
+		ret = dlm_process_incoming_buffer(con->nodeid, con->rx_buf, buflen);
+		if (ret < 0)
+			goto out_close;
+
+		/* calculate leftover bytes from process and put it into begin of
+		 * the receive buffer, so next receive we have the full message
+		 * at the start address of the receive buffer.
+		 */
+		con->rx_leftover = buflen - ret;
+		if (con->rx_leftover) {
+			memmove(con->rx_buf, con->rx_buf + ret,
+				con->rx_leftover);
+		}
+	}
+
+	dlm_midcomms_receive_done(con->nodeid);
+	mutex_unlock(&con->sock_mutex);
+	return 0;
+
+out_resched:
+	if (!test_and_set_bit(CF_READ_PENDING, &con->flags))
+		queue_work(recv_workqueue, &con->rwork);
+	mutex_unlock(&con->sock_mutex);
+	return -EAGAIN;
+
+out_close:
+	if (ret == 0) {
+		log_print("connection %p got EOF from %d",
+			  con, con->nodeid);
+
+		if (dlm_proto_ops->eof_condition &&
+		    dlm_proto_ops->eof_condition(con)) {
+			set_bit(CF_EOF, &con->flags);
+			mutex_unlock(&con->sock_mutex);
+		} else {
+			mutex_unlock(&con->sock_mutex);
+			close_connection(con, false, true, false);
+
+			/* handling for tcp shutdown */
+			clear_bit(CF_SHUTDOWN, &con->flags);
+			wake_up(&con->shutdown_wait);
+		}
+
+		/* signal to breaking receive worker */
+		ret = -1;
+	} else {
+		mutex_unlock(&con->sock_mutex);
+	}
+	return ret;
+}
+
+/* Listening socket is busy, accept a connection */
+static int accept_from_sock(struct listen_connection *con)
+{
+	int result;
+	struct sockaddr_storage peeraddr;
+	struct socket *newsock;
+	int len, idx;
+	int nodeid;
+	struct connection *newcon;
+	struct connection *addcon;
+	unsigned int mark;
+
+	if (!con->sock)
+		return -ENOTCONN;
+
+	result = kernel_accept(con->sock, &newsock, O_NONBLOCK);
+	if (result < 0)
+		goto accept_err;
+
+	/* Get the connected socket's peer */
+	memset(&peeraddr, 0, sizeof(peeraddr));
+	len = newsock->ops->getname(newsock, (struct sockaddr *)&peeraddr, 2);
+	if (len < 0) {
+		result = -ECONNABORTED;
+		goto accept_err;
+	}
+
+	/* Get the new node's NODEID */
+	make_sockaddr(&peeraddr, 0, &len);
+	if (addr_to_nodeid(&peeraddr, &nodeid, &mark)) {
+		switch (peeraddr.ss_family) {
+		case AF_INET: {
+			struct sockaddr_in *sin = (struct sockaddr_in *)&peeraddr;
+
+			log_print("connect from non cluster IPv4 node %pI4",
+				  &sin->sin_addr);
+			break;
+		}
+#if IS_ENABLED(CONFIG_IPV6)
+		case AF_INET6: {
+			struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&peeraddr;
+
+			log_print("connect from non cluster IPv6 node %pI6c",
+				  &sin6->sin6_addr);
+			break;
+		}
+#endif
+		default:
+			log_print("invalid family from non cluster node");
+			break;
+		}
+
+		sock_release(newsock);
+		return -1;
+	}
+
+	log_print("got connection from %d", nodeid);
+
+	/*  Check to see if we already have a connection to this node. This
+	 *  could happen if the two nodes initiate a connection at roughly
+	 *  the same time and the connections cross on the wire.
+	 *  In this case we store the incoming one in "othercon"
+	 */
+	idx = srcu_read_lock(&connections_srcu);
+	newcon = nodeid2con(nodeid, GFP_NOFS);
+	if (!newcon) {
+		srcu_read_unlock(&connections_srcu, idx);
+		result = -ENOMEM;
+		goto accept_err;
+	}
+
+	sock_set_mark(newsock->sk, mark);
+
+	mutex_lock(&newcon->sock_mutex);
+	if (newcon->sock) {
+		struct connection *othercon = newcon->othercon;
+
+		if (!othercon) {
+			othercon = kzalloc(sizeof(*othercon), GFP_NOFS);
+			if (!othercon) {
+				log_print("failed to allocate incoming socket");
+				mutex_unlock(&newcon->sock_mutex);
+				srcu_read_unlock(&connections_srcu, idx);
+				result = -ENOMEM;
+				goto accept_err;
+			}
+
+			result = dlm_con_init(othercon, nodeid);
+			if (result < 0) {
+				kfree(othercon);
+				mutex_unlock(&newcon->sock_mutex);
+				srcu_read_unlock(&connections_srcu, idx);
+				goto accept_err;
+			}
+
+			lockdep_set_subclass(&othercon->sock_mutex, 1);
+			set_bit(CF_IS_OTHERCON, &othercon->flags);
+			newcon->othercon = othercon;
+			othercon->sendcon = newcon;
+		} else {
+			/* close other sock con if we have something new */
+			close_connection(othercon, false, true, false);
+		}
+
+		mutex_lock(&othercon->sock_mutex);
+		add_sock(newsock, othercon);
+		addcon = othercon;
+		mutex_unlock(&othercon->sock_mutex);
+	}
+	else {
+		/* accept copies the sk after we've saved the callbacks, so we
+		   don't want to save them a second time or comm errors will
+		   result in calling sk_error_report recursively. */
+		add_sock(newsock, newcon);
+		addcon = newcon;
+	}
+
+	set_bit(CF_CONNECTED, &addcon->flags);
+	mutex_unlock(&newcon->sock_mutex);
+
+	/*
+	 * Add it to the active queue in case we got data
+	 * between processing the accept adding the socket
+	 * to the read_sockets list
+	 */
+	if (!test_and_set_bit(CF_READ_PENDING, &addcon->flags))
+		queue_work(recv_workqueue, &addcon->rwork);
+
+	srcu_read_unlock(&connections_srcu, idx);
+
+	return 0;
+
+accept_err:
+	if (newsock)
+		sock_release(newsock);
+
+	if (result != -EAGAIN)
+		log_print("error accepting connection from node: %d", result);
+	return result;
+}
+
+/*
+ * writequeue_entry_complete - try to delete and free write queue entry
+ * @e: write queue entry to try to delete
+ * @completed: bytes completed
+ *
+ * writequeue_lock must be held.
+ */
+static void writequeue_entry_complete(struct writequeue_entry *e, int completed)
+{
+	e->offset += completed;
+	e->len -= completed;
+	/* signal that page was half way transmitted */
+	e->dirty = true;
+
+	if (e->len == 0 && e->users == 0)
+		free_entry(e);
+}
+
+/*
+ * sctp_bind_addrs - bind a SCTP socket to all our addresses
+ */
+static int sctp_bind_addrs(struct socket *sock, uint16_t port)
+{
+	struct sockaddr_storage localaddr;
+	struct sockaddr *addr = (struct sockaddr *)&localaddr;
+	int i, addr_len, result = 0;
+
+	for (i = 0; i < dlm_local_count; i++) {
+		memcpy(&localaddr, dlm_local_addr[i], sizeof(localaddr));
+		make_sockaddr(&localaddr, port, &addr_len);
+
+		if (!i)
+			result = kernel_bind(sock, addr, addr_len);
+		else
+			result = sock_bind_add(sock->sk, addr, addr_len);
+
+		if (result < 0) {
+			log_print("Can't bind to %d addr number %d, %d.\n",
+				  port, i + 1, result);
+			break;
+		}
+	}
+	return result;
+}
+
+/* Get local addresses */
+static void init_local(void)
+{
+	struct sockaddr_storage sas, *addr;
+	int i;
+
+	dlm_local_count = 0;
+	for (i = 0; i < DLM_MAX_ADDR_COUNT; i++) {
+		if (dlm_our_addr(&sas, i))
+			break;
+
+		addr = kmemdup(&sas, sizeof(*addr), GFP_NOFS);
+		if (!addr)
+			break;
+		dlm_local_addr[dlm_local_count++] = addr;
+	}
+}
+
+static void deinit_local(void)
+{
+	int i;
+
+	for (i = 0; i < dlm_local_count; i++)
+		kfree(dlm_local_addr[i]);
+}
+
+static struct writequeue_entry *new_writequeue_entry(struct connection *con)
+{
+	struct writequeue_entry *entry;
+
+	entry = dlm_allocate_writequeue();
+	if (!entry)
+		return NULL;
+
+	entry->page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
+	if (!entry->page) {
+		dlm_free_writequeue(entry);
+		return NULL;
+	}
+
+	entry->offset = 0;
+	entry->len = 0;
+	entry->end = 0;
+	entry->dirty = false;
+	entry->con = con;
+	entry->users = 1;
+	kref_init(&entry->ref);
+	return entry;
+}
+
+static struct writequeue_entry *new_wq_entry(struct connection *con, int len,
+					     char **ppc, void (*cb)(void *data),
+					     void *data)
+{
+	struct writequeue_entry *e;
+
+	spin_lock(&con->writequeue_lock);
+	if (!list_empty(&con->writequeue)) {
+		e = list_last_entry(&con->writequeue, struct writequeue_entry, list);
+		if (DLM_WQ_REMAIN_BYTES(e) >= len) {
+			kref_get(&e->ref);
+
+			*ppc = page_address(e->page) + e->end;
+			if (cb)
+				cb(data);
+
+			e->end += len;
+			e->users++;
+			goto out;
+		}
+	}
+
+	e = new_writequeue_entry(con);
+	if (!e)
+		goto out;
+
+	kref_get(&e->ref);
+	*ppc = page_address(e->page);
+	e->end += len;
+	atomic_inc(&con->writequeue_cnt);
+	if (cb)
+		cb(data);
+
+	list_add_tail(&e->list, &con->writequeue);
+
+out:
+	spin_unlock(&con->writequeue_lock);
+	return e;
+};
+
+static struct dlm_msg *dlm_lowcomms_new_msg_con(struct connection *con, int len,
+						gfp_t allocation, char **ppc,
+						void (*cb)(void *data),
+						void *data)
+{
+	struct writequeue_entry *e;
+	struct dlm_msg *msg;
+
+	msg = dlm_allocate_msg(allocation);
+	if (!msg)
+		return NULL;
+
+	kref_init(&msg->ref);
+
+	e = new_wq_entry(con, len, ppc, cb, data);
+	if (!e) {
+		dlm_free_msg(msg);
+		return NULL;
+	}
+
+	msg->retransmit = false;
+	msg->orig_msg = NULL;
+	msg->ppc = *ppc;
+	msg->len = len;
+	msg->entry = e;
+
+	return msg;
+}
+
+/* avoid false positive for nodes_srcu, unlock happens in
+ * dlm_lowcomms_commit_msg which is a must call if success
+ */
+#ifndef __CHECKER__
+struct dlm_msg *dlm_lowcomms_new_msg(int nodeid, int len, gfp_t allocation,
+				     char **ppc, void (*cb)(void *data),
+				     void *data)
+{
+	struct connection *con;
+	struct dlm_msg *msg;
+	int idx;
+
+	if (len > DLM_MAX_SOCKET_BUFSIZE ||
+	    len < sizeof(struct dlm_header)) {
+		BUILD_BUG_ON(PAGE_SIZE < DLM_MAX_SOCKET_BUFSIZE);
+		log_print("failed to allocate a buffer of size %d", len);
+		WARN_ON(1);
+		return NULL;
+	}
+
+	idx = srcu_read_lock(&connections_srcu);
+	con = nodeid2con(nodeid, allocation);
+	if (!con) {
+		srcu_read_unlock(&connections_srcu, idx);
+		return NULL;
+	}
+
+	msg = dlm_lowcomms_new_msg_con(con, len, allocation, ppc, cb, data);
+	if (!msg) {
+		srcu_read_unlock(&connections_srcu, idx);
+		return NULL;
+	}
+
+	/* for dlm_lowcomms_commit_msg() */
+	kref_get(&msg->ref);
+	/* we assume if successful commit must called */
+	msg->idx = idx;
+	return msg;
+}
+#endif
+
+static void _dlm_lowcomms_commit_msg(struct dlm_msg *msg)
+{
+	struct writequeue_entry *e = msg->entry;
+	struct connection *con = e->con;
+	int users;
+
+	spin_lock(&con->writequeue_lock);
+	kref_get(&msg->ref);
+	list_add(&msg->list, &e->msgs);
+
+	users = --e->users;
+	if (users)
+		goto out;
+
+	e->len = DLM_WQ_LENGTH_BYTES(e);
+	spin_unlock(&con->writequeue_lock);
+
+	queue_work(send_workqueue, &con->swork);
+	return;
+
+out:
+	spin_unlock(&con->writequeue_lock);
+	return;
+}
+
+/* avoid false positive for nodes_srcu, lock was happen in
+ * dlm_lowcomms_new_msg
+ */
+#ifndef __CHECKER__
+void dlm_lowcomms_commit_msg(struct dlm_msg *msg)
+{
+	_dlm_lowcomms_commit_msg(msg);
+	srcu_read_unlock(&connections_srcu, msg->idx);
+	/* because dlm_lowcomms_new_msg() */
+	kref_put(&msg->ref, dlm_msg_release);
+}
+#endif
+
+void dlm_lowcomms_put_msg(struct dlm_msg *msg)
+{
+	kref_put(&msg->ref, dlm_msg_release);
+}
+
+/* does not held connections_srcu, usage workqueue only */
+int dlm_lowcomms_resend_msg(struct dlm_msg *msg)
+{
+	struct dlm_msg *msg_resend;
+	char *ppc;
+
+	if (msg->retransmit)
+		return 1;
+
+	msg_resend = dlm_lowcomms_new_msg_con(msg->entry->con, msg->len,
+					      GFP_ATOMIC, &ppc, NULL, NULL);
+	if (!msg_resend)
+		return -ENOMEM;
+
+	msg->retransmit = true;
+	kref_get(&msg->ref);
+	msg_resend->orig_msg = msg;
+
+	memcpy(ppc, msg->ppc, msg->len);
+	_dlm_lowcomms_commit_msg(msg_resend);
+	dlm_lowcomms_put_msg(msg_resend);
+
+	return 0;
+}
+
+/* Send a message */
+static void send_to_sock(struct connection *con)
+{
+	const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
+	struct writequeue_entry *e;
+	int len, offset, ret;
+	int count = 0;
+
+	mutex_lock(&con->sock_mutex);
+	if (con->sock == NULL)
+		goto out_connect;
+
+	spin_lock(&con->writequeue_lock);
+	for (;;) {
+		e = con_next_wq(con);
+		if (!e)
+			break;
+
+		len = e->len;
+		offset = e->offset;
+		BUG_ON(len == 0 && e->users == 0);
+		spin_unlock(&con->writequeue_lock);
+
+		ret = kernel_sendpage(con->sock, e->page, offset, len,
+				      msg_flags);
+		trace_dlm_send(con->nodeid, ret);
+		if (ret == -EAGAIN || ret == 0) {
+			if (ret == -EAGAIN &&
+			    test_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags) &&
+			    !test_and_set_bit(CF_APP_LIMITED, &con->flags)) {
+				/* Notify TCP that we're limited by the
+				 * application window size.
+				 */
+				set_bit(SOCK_NOSPACE, &con->sock->flags);
+				con->sock->sk->sk_write_pending++;
+			}
+			cond_resched();
+			goto out;
+		} else if (ret < 0)
+			goto out;
+
+		/* Don't starve people filling buffers */
+		if (++count >= MAX_SEND_MSG_COUNT) {
+			cond_resched();
+			count = 0;
+		}
+
+		spin_lock(&con->writequeue_lock);
+		writequeue_entry_complete(e, ret);
+	}
+	spin_unlock(&con->writequeue_lock);
+
+	/* close if we got EOF */
+	if (test_and_clear_bit(CF_EOF, &con->flags)) {
+		mutex_unlock(&con->sock_mutex);
+		close_connection(con, false, false, true);
+
+		/* handling for tcp shutdown */
+		clear_bit(CF_SHUTDOWN, &con->flags);
+		wake_up(&con->shutdown_wait);
+	} else {
+		mutex_unlock(&con->sock_mutex);
+	}
+
+	return;
+
+out:
+	mutex_unlock(&con->sock_mutex);
+	return;
+
+out_connect:
+	mutex_unlock(&con->sock_mutex);
+	queue_work(send_workqueue, &con->swork);
+	cond_resched();
+}
+
+static void clean_one_writequeue(struct connection *con)
+{
+	struct writequeue_entry *e, *safe;
+
+	spin_lock(&con->writequeue_lock);
+	list_for_each_entry_safe(e, safe, &con->writequeue, list) {
+		free_entry(e);
+	}
+	spin_unlock(&con->writequeue_lock);
+}
+
+/* Called from recovery when it knows that a node has
+   left the cluster */
+int dlm_lowcomms_close(int nodeid)
+{
+	struct connection *con;
+	struct dlm_node_addr *na;
+	int idx;
+
+	log_print("closing connection to node %d", nodeid);
+	idx = srcu_read_lock(&connections_srcu);
+	con = nodeid2con(nodeid, 0);
+	if (con) {
+		set_bit(CF_CLOSE, &con->flags);
+		close_connection(con, true, true, true);
+		clean_one_writequeue(con);
+		if (con->othercon)
+			clean_one_writequeue(con->othercon);
+	}
+	srcu_read_unlock(&connections_srcu, idx);
+
+	spin_lock(&dlm_node_addrs_spin);
+	na = find_node_addr(nodeid);
+	if (na) {
+		list_del(&na->list);
+		while (na->addr_count--)
+			kfree(na->addr[na->addr_count]);
+		kfree(na);
+	}
+	spin_unlock(&dlm_node_addrs_spin);
+
+	return 0;
+}
+
+/* Receive workqueue function */
+static void process_recv_sockets(struct work_struct *work)
+{
+	struct connection *con = container_of(work, struct connection, rwork);
+
+	clear_bit(CF_READ_PENDING, &con->flags);
+	receive_from_sock(con);
+}
+
+static void process_listen_recv_socket(struct work_struct *work)
+{
+	int ret;
+
+	do {
+		ret = accept_from_sock(&listen_con);
+	} while (!ret);
+}
+
+static void dlm_connect(struct connection *con)
+{
+	struct sockaddr_storage addr;
+	int result, addr_len;
+	struct socket *sock;
+	unsigned int mark;
+
+	/* Some odd races can cause double-connects, ignore them */
+	if (con->retries++ > MAX_CONNECT_RETRIES)
+		return;
+
+	if (con->sock) {
+		log_print("node %d already connected.", con->nodeid);
+		return;
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	result = nodeid_to_addr(con->nodeid, &addr, NULL,
+				dlm_proto_ops->try_new_addr, &mark);
+	if (result < 0) {
+		log_print("no address for nodeid %d", con->nodeid);
+		return;
+	}
+
+	/* Create a socket to communicate with */
+	result = sock_create_kern(&init_net, dlm_local_addr[0]->ss_family,
+				  SOCK_STREAM, dlm_proto_ops->proto, &sock);
+	if (result < 0)
+		goto socket_err;
+
+	sock_set_mark(sock->sk, mark);
+	dlm_proto_ops->sockopts(sock);
+
+	add_sock(sock, con);
+
+	result = dlm_proto_ops->bind(sock);
+	if (result < 0)
+		goto add_sock_err;
+
+	log_print_ratelimited("connecting to %d", con->nodeid);
+	make_sockaddr(&addr, dlm_config.ci_tcp_port, &addr_len);
+	result = dlm_proto_ops->connect(con, sock, (struct sockaddr *)&addr,
+					addr_len);
+	if (result < 0)
+		goto add_sock_err;
+
+	return;
+
+add_sock_err:
+	dlm_close_sock(&con->sock);
+
+socket_err:
+	/*
+	 * Some errors are fatal and this list might need adjusting. For other
+	 * errors we try again until the max number of retries is reached.
+	 */
+	if (result != -EHOSTUNREACH &&
+	    result != -ENETUNREACH &&
+	    result != -ENETDOWN &&
+	    result != -EINVAL &&
+	    result != -EPROTONOSUPPORT) {
+		log_print("connect %d try %d error %d", con->nodeid,
+			  con->retries, result);
+		msleep(1000);
+		lowcomms_connect_sock(con);
+	}
+}
+
+/* Send workqueue function */
+static void process_send_sockets(struct work_struct *work)
+{
+	struct connection *con = container_of(work, struct connection, swork);
+
+	WARN_ON(test_bit(CF_IS_OTHERCON, &con->flags));
+
+	clear_bit(CF_WRITE_PENDING, &con->flags);
+
+	if (test_and_clear_bit(CF_RECONNECT, &con->flags)) {
+		close_connection(con, false, false, true);
+		dlm_midcomms_unack_msg_resend(con->nodeid);
+	}
+
+	if (con->sock == NULL) {
+		if (test_and_clear_bit(CF_DELAY_CONNECT, &con->flags))
+			msleep(1000);
+
+		mutex_lock(&con->sock_mutex);
+		dlm_connect(con);
+		mutex_unlock(&con->sock_mutex);
+	}
+
+	if (!list_empty(&con->writequeue))
+		send_to_sock(con);
+}
+
+static void work_stop(void)
+{
+	if (recv_workqueue) {
+		destroy_workqueue(recv_workqueue);
+		recv_workqueue = NULL;
+	}
+
+	if (send_workqueue) {
+		destroy_workqueue(send_workqueue);
+		send_workqueue = NULL;
+	}
+}
+
+static int work_start(void)
+{
+	recv_workqueue = alloc_ordered_workqueue("dlm_recv", WQ_MEM_RECLAIM);
+	if (!recv_workqueue) {
+		log_print("can't start dlm_recv");
+		return -ENOMEM;
+	}
+
+	send_workqueue = alloc_ordered_workqueue("dlm_send", WQ_MEM_RECLAIM);
+	if (!send_workqueue) {
+		log_print("can't start dlm_send");
+		destroy_workqueue(recv_workqueue);
+		recv_workqueue = NULL;
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static void shutdown_conn(struct connection *con)
+{
+	if (dlm_proto_ops->shutdown_action)
+		dlm_proto_ops->shutdown_action(con);
+}
+
+void dlm_lowcomms_shutdown(void)
+{
+	int idx;
+
+	/* Set all the flags to prevent any
+	 * socket activity.
+	 */
+	dlm_allow_conn = 0;
+
+	if (recv_workqueue)
+		flush_workqueue(recv_workqueue);
+	if (send_workqueue)
+		flush_workqueue(send_workqueue);
+
+	dlm_close_sock(&listen_con.sock);
+
+	idx = srcu_read_lock(&connections_srcu);
+	foreach_conn(shutdown_conn);
+	srcu_read_unlock(&connections_srcu, idx);
+}
+
+static void _stop_conn(struct connection *con, bool and_other)
+{
+	mutex_lock(&con->sock_mutex);
+	set_bit(CF_CLOSE, &con->flags);
+	set_bit(CF_READ_PENDING, &con->flags);
+	set_bit(CF_WRITE_PENDING, &con->flags);
+	if (con->sock && con->sock->sk) {
+		lock_sock(con->sock->sk);
+		con->sock->sk->sk_user_data = NULL;
+		release_sock(con->sock->sk);
+	}
+	if (con->othercon && and_other)
+		_stop_conn(con->othercon, false);
+	mutex_unlock(&con->sock_mutex);
+}
+
+static void stop_conn(struct connection *con)
+{
+	_stop_conn(con, true);
+}
+
+static void connection_release(struct rcu_head *rcu)
+{
+	struct connection *con = container_of(rcu, struct connection, rcu);
+
+	kfree(con->rx_buf);
+	kfree(con);
+}
+
+static void free_conn(struct connection *con)
+{
+	close_connection(con, true, true, true);
+	spin_lock(&connections_lock);
+	hlist_del_rcu(&con->list);
+	spin_unlock(&connections_lock);
+	if (con->othercon) {
+		clean_one_writequeue(con->othercon);
+		call_srcu(&connections_srcu, &con->othercon->rcu,
+			  connection_release);
+	}
+	clean_one_writequeue(con);
+	call_srcu(&connections_srcu, &con->rcu, connection_release);
+}
+
+static void work_flush(void)
+{
+	int ok;
+	int i;
+	struct connection *con;
+
+	do {
+		ok = 1;
+		foreach_conn(stop_conn);
+		if (recv_workqueue)
+			flush_workqueue(recv_workqueue);
+		if (send_workqueue)
+			flush_workqueue(send_workqueue);
+		for (i = 0; i < CONN_HASH_SIZE && ok; i++) {
+			hlist_for_each_entry_rcu(con, &connection_hash[i],
+						 list) {
+				ok &= test_bit(CF_READ_PENDING, &con->flags);
+				ok &= test_bit(CF_WRITE_PENDING, &con->flags);
+				if (con->othercon) {
+					ok &= test_bit(CF_READ_PENDING,
+						       &con->othercon->flags);
+					ok &= test_bit(CF_WRITE_PENDING,
+						       &con->othercon->flags);
+				}
+			}
+		}
+	} while (!ok);
+}
+
+void dlm_lowcomms_stop(void)
+{
+	int idx;
+
+	idx = srcu_read_lock(&connections_srcu);
+	work_flush();
+	foreach_conn(free_conn);
+	srcu_read_unlock(&connections_srcu, idx);
+	work_stop();
+	deinit_local();
+
+	dlm_proto_ops = NULL;
+}
+
+static int dlm_listen_for_all(void)
+{
+	struct socket *sock;
+	int result;
+
+	log_print("Using %s for communications",
+		  dlm_proto_ops->name);
+
+	result = dlm_proto_ops->listen_validate();
+	if (result < 0)
+		return result;
+
+	result = sock_create_kern(&init_net, dlm_local_addr[0]->ss_family,
+				  SOCK_STREAM, dlm_proto_ops->proto, &sock);
+	if (result < 0) {
+		log_print("Can't create comms socket: %d", result);
+		return result;
+	}
+
+	sock_set_mark(sock->sk, dlm_config.ci_mark);
+	dlm_proto_ops->listen_sockopts(sock);
+
+	result = dlm_proto_ops->listen_bind(sock);
+	if (result < 0)
+		goto out;
+
+	save_listen_callbacks(sock);
+	add_listen_sock(sock, &listen_con);
+
+	INIT_WORK(&listen_con.rwork, process_listen_recv_socket);
+	result = sock->ops->listen(sock, 5);
+	if (result < 0) {
+		dlm_close_sock(&listen_con.sock);
+		return result;
+	}
+
+	return 0;
+
+out:
+	sock_release(sock);
+	return result;
+}
+
+static int dlm_tcp_bind(struct socket *sock)
+{
+	struct sockaddr_storage src_addr;
+	int result, addr_len;
+
+	/* Bind to our cluster-known address connecting to avoid
+	 * routing problems.
+	 */
+	memcpy(&src_addr, dlm_local_addr[0], sizeof(src_addr));
+	make_sockaddr(&src_addr, 0, &addr_len);
+
+	result = kernel_bind(sock, (struct sockaddr *)&src_addr,
+			     addr_len);
+	if (result < 0) {
+		/* This *may* not indicate a critical error */
+		log_print("could not bind for connect: %d", result);
+	}
+
+	return 0;
+}
+
+static int dlm_tcp_connect(struct connection *con, struct socket *sock,
+			   struct sockaddr *addr, int addr_len)
+{
+	int ret;
+
+	ret = kernel_connect(sock, addr, addr_len, O_NONBLOCK);
+	switch (ret) {
+	case -EINPROGRESS:
+		fallthrough;
+	case 0:
+		return 0;
+	}
+
+	return ret;
+}
+
+static int dlm_tcp_listen_validate(void)
+{
+	/* We don't support multi-homed hosts */
+	if (dlm_local_count > 1) {
+		log_print("TCP protocol can't handle multi-homed hosts, try SCTP");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void dlm_tcp_sockopts(struct socket *sock)
+{
+	/* Turn off Nagle's algorithm */
+	tcp_sock_set_nodelay(sock->sk);
+}
+
+static void dlm_tcp_listen_sockopts(struct socket *sock)
+{
+	dlm_tcp_sockopts(sock);
+	sock_set_reuseaddr(sock->sk);
+}
+
+static int dlm_tcp_listen_bind(struct socket *sock)
+{
+	int addr_len;
+
+	/* Bind to our port */
+	make_sockaddr(dlm_local_addr[0], dlm_config.ci_tcp_port, &addr_len);
+	return kernel_bind(sock, (struct sockaddr *)&dlm_local_addr[0],
+			   addr_len);
+}
+
+static const struct dlm_proto_ops dlm_tcp_ops = {
+	.name = "TCP",
+	.proto = IPPROTO_TCP,
+	.connect = dlm_tcp_connect,
+	.sockopts = dlm_tcp_sockopts,
+	.bind = dlm_tcp_bind,
+	.listen_validate = dlm_tcp_listen_validate,
+	.listen_sockopts = dlm_tcp_listen_sockopts,
+	.listen_bind = dlm_tcp_listen_bind,
+	.shutdown_action = dlm_tcp_shutdown,
+	.eof_condition = tcp_eof_condition,
+};
+
+static int dlm_sctp_bind(struct socket *sock)
+{
+	return sctp_bind_addrs(sock, 0);
+}
+
+static int dlm_sctp_connect(struct connection *con, struct socket *sock,
+			    struct sockaddr *addr, int addr_len)
+{
+	int ret;
+
+	/*
+	 * Make kernel_connect() function return in specified time,
+	 * since O_NONBLOCK argument in connect() function does not work here,
+	 * then, we should restore the default value of this attribute.
+	 */
+	sock_set_sndtimeo(sock->sk, 5);
+	ret = kernel_connect(sock, addr, addr_len, 0);
+	sock_set_sndtimeo(sock->sk, 0);
+	if (ret < 0)
+		return ret;
+
+	if (!test_and_set_bit(CF_CONNECTED, &con->flags))
+		log_print("connected to node %d", con->nodeid);
+
+	return 0;
+}
+
+static int dlm_sctp_listen_validate(void)
+{
+	if (!IS_ENABLED(CONFIG_IP_SCTP)) {
+		log_print("SCTP is not enabled by this kernel");
+		return -EOPNOTSUPP;
+	}
+
+	request_module("sctp");
+	return 0;
+}
+
+static int dlm_sctp_bind_listen(struct socket *sock)
+{
+	return sctp_bind_addrs(sock, dlm_config.ci_tcp_port);
+}
+
+static void dlm_sctp_sockopts(struct socket *sock)
+{
+	/* Turn off Nagle's algorithm */
+	sctp_sock_set_nodelay(sock->sk);
+	sock_set_rcvbuf(sock->sk, NEEDED_RMEM);
+}
+
+static const struct dlm_proto_ops dlm_sctp_ops = {
+	.name = "SCTP",
+	.proto = IPPROTO_SCTP,
+	.try_new_addr = true,
+	.connect = dlm_sctp_connect,
+	.sockopts = dlm_sctp_sockopts,
+	.bind = dlm_sctp_bind,
+	.listen_validate = dlm_sctp_listen_validate,
+	.listen_sockopts = dlm_sctp_sockopts,
+	.listen_bind = dlm_sctp_bind_listen,
+};
+
+int dlm_lowcomms_start(void)
+{
+	int error = -EINVAL;
+
+	init_local();
+	if (!dlm_local_count) {
+		error = -ENOTCONN;
+		log_print("no local IP address has been set");
+		goto fail;
+	}
+
+	error = work_start();
+	if (error)
+		goto fail_local;
+
+	dlm_allow_conn = 1;
+
+	/* Start listening */
+	switch (dlm_config.ci_protocol) {
+	case DLM_PROTO_TCP:
+		dlm_proto_ops = &dlm_tcp_ops;
+		break;
+	case DLM_PROTO_SCTP:
+		dlm_proto_ops = &dlm_sctp_ops;
+		break;
+	default:
+		log_print("Invalid protocol identifier %d set",
+			  dlm_config.ci_protocol);
+		error = -EINVAL;
+		goto fail_proto_ops;
+	}
+
+	error = dlm_listen_for_all();
+	if (error)
+		goto fail_listen;
+
+	return 0;
+
+fail_listen:
+	dlm_proto_ops = NULL;
+fail_proto_ops:
+	dlm_allow_conn = 0;
+	work_stop();
+fail_local:
+	deinit_local();
+fail:
+	return error;
+}
+
+void dlm_lowcomms_init(void)
+{
+	int i;
+
+	for (i = 0; i < CONN_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&connection_hash[i]);
+
+	INIT_WORK(&listen_con.rwork, process_listen_recv_socket);
+}
+
+void dlm_lowcomms_exit(void)
+{
+	struct dlm_node_addr *na, *safe;
+
+	spin_lock(&dlm_node_addrs_spin);
+	list_for_each_entry_safe(na, safe, &dlm_node_addrs, list) {
+		list_del(&na->list);
+		while (na->addr_count--)
+			kfree(na->addr[na->addr_count]);
+		kfree(na);
+	}
+	spin_unlock(&dlm_node_addrs_spin);
+}