Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 1537 insertions, 0 deletions

diff --git a/fs/dlm/midcomms.c b/fs/dlm/midcomms.c
new file mode 100644
index 000000000..71e426da4
--- /dev/null
+++ b/fs/dlm/midcomms.c
@@ -0,0 +1,1537 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2021 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+/*
+ * midcomms.c
+ *
+ * This is the appallingly named "mid-level" comms layer. It takes care about
+ * deliver an on application layer "reliable" communication above the used
+ * lowcomms transport layer.
+ *
+ * How it works:
+ *
+ * Each nodes keeps track of all send DLM messages in send_queue with a sequence
+ * number. The receive will send an DLM_ACK message back for every DLM message
+ * received at the other side. If a reconnect happens in lowcomms we will send
+ * all unacknowledged dlm messages again. The receiving side might drop any already
+ * received message by comparing sequence numbers.
+ *
+ * How version detection works:
+ *
+ * Due the fact that dlm has pre-configured node addresses on every side
+ * it is in it's nature that every side connects at starts to transmit
+ * dlm messages which ends in a race. However DLM_RCOM_NAMES, DLM_RCOM_STATUS
+ * and their replies are the first messages which are exchanges. Due backwards
+ * compatibility these messages are not covered by the midcomms re-transmission
+ * layer. These messages have their own re-transmission handling in the dlm
+ * application layer. The version field of every node will be set on these RCOM
+ * messages as soon as they arrived and the node isn't yet part of the nodes
+ * hash. There exists also logic to detect version mismatched if something weird
+ * going on or the first messages isn't an expected one.
+ *
+ * Termination:
+ *
+ * The midcomms layer does a 4 way handshake for termination on DLM protocol
+ * like TCP supports it with half-closed socket support. SCTP doesn't support
+ * half-closed socket, so we do it on DLM layer. Also socket shutdown() can be
+ * interrupted by .e.g. tcp reset itself. Additional there exists the othercon
+ * paradigm in lowcomms which cannot be easily without breaking backwards
+ * compatibility. A node cannot send anything to another node when a DLM_FIN
+ * message was send. There exists additional logic to print a warning if
+ * DLM wants to do it. There exists a state handling like RFC 793 but reduced
+ * to termination only. The event "member removal event" describes the cluster
+ * manager removed the node from internal lists, at this point DLM does not
+ * send any message to the other node. There exists two cases:
+ *
+ * 1. The cluster member was removed and we received a FIN
+ * OR
+ * 2. We received a FIN but the member was not removed yet
+ *
+ * One of these cases will do the CLOSE_WAIT to LAST_ACK change.
+ *
+ *
+ *                              +---------+
+ *                              | CLOSED  |
+ *                              +---------+
+ *                                   | add member/receive RCOM version
+ *                                   |            detection msg
+ *                                   V
+ *                              +---------+
+ *                              |  ESTAB  |
+ *                              +---------+
+ *                       CLOSE    |     |    rcv FIN
+ *                      -------   |     |    -------
+ * +---------+          snd FIN  /       \   snd ACK          +---------+
+ * |  FIN    |<-----------------           ------------------>|  CLOSE  |
+ * | WAIT-1  |------------------                              |   WAIT  |
+ * +---------+          rcv FIN  \                            +---------+
+ * | rcv ACK of FIN   -------   |                            CLOSE  | member
+ * | --------------   snd ACK   |                           ------- | removal
+ * V        x                   V                           snd FIN V event
+ * +---------+                  +---------+                   +---------+
+ * |FINWAIT-2|                  | CLOSING |                   | LAST-ACK|
+ * +---------+                  +---------+                   +---------+
+ * |                rcv ACK of FIN |                 rcv ACK of FIN |
+ * |  rcv FIN       -------------- |                 -------------- |
+ * |  -------              x       V                        x       V
+ *  \ snd ACK                 +---------+                   +---------+
+ *   ------------------------>| CLOSED  |                   | CLOSED  |
+ *                            +---------+                   +---------+
+ *
+ * NOTE: any state can interrupted by midcomms_close() and state will be
+ * switched to CLOSED in case of fencing. There exists also some timeout
+ * handling when we receive the version detection RCOM messages which is
+ * made by observation.
+ *
+ * Future improvements:
+ *
+ * There exists some known issues/improvements of the dlm handling. Some
+ * of them should be done in a next major dlm version bump which makes
+ * it incompatible with previous versions.
+ *
+ * Unaligned memory access:
+ *
+ * There exists cases when the dlm message buffer length is not aligned
+ * to 8 byte. However seems nobody detected any problem with it. This
+ * can be fixed in the next major version bump of dlm.
+ *
+ * Version detection:
+ *
+ * The version detection and how it's done is related to backwards
+ * compatibility. There exists better ways to make a better handling.
+ * However this should be changed in the next major version bump of dlm.
+ *
+ * Tail Size checking:
+ *
+ * There exists a message tail payload in e.g. DLM_MSG however we don't
+ * check it against the message length yet regarding to the receive buffer
+ * length. That need to be validated.
+ *
+ * Fencing bad nodes:
+ *
+ * At timeout places or weird sequence number behaviours we should send
+ * a fencing request to the cluster manager.
+ */
+
+/* Debug switch to enable a 5 seconds sleep waiting of a termination.
+ * This can be useful to test fencing while termination is running.
+ * This requires a setup with only gfs2 as dlm user, so that the
+ * last umount will terminate the connection.
+ *
+ * However it became useful to test, while the 5 seconds block in umount
+ * just press the reset button. In a lot of dropping the termination
+ * process can could take several seconds.
+ */
+#define DLM_DEBUG_FENCE_TERMINATION	0
+
+#include <trace/events/dlm.h>
+#include <net/tcp.h>
+
+#include "dlm_internal.h"
+#include "lowcomms.h"
+#include "config.h"
+#include "memory.h"
+#include "lock.h"
+#include "util.h"
+#include "midcomms.h"
+
+/* init value for sequence numbers for testing purpose only e.g. overflows */
+#define DLM_SEQ_INIT		0
+/* 3 minutes wait to sync ending of dlm */
+#define DLM_SHUTDOWN_TIMEOUT	msecs_to_jiffies(3 * 60 * 1000)
+#define DLM_VERSION_NOT_SET	0
+
+struct midcomms_node {
+	int nodeid;
+	uint32_t version;
+	uint32_t seq_send;
+	uint32_t seq_next;
+	/* These queues are unbound because we cannot drop any message in dlm.
+	 * We could send a fence signal for a specific node to the cluster
+	 * manager if queues hits some maximum value, however this handling
+	 * not supported yet.
+	 */
+	struct list_head send_queue;
+	spinlock_t send_queue_lock;
+	atomic_t send_queue_cnt;
+#define DLM_NODE_FLAG_CLOSE	1
+#define DLM_NODE_FLAG_STOP_TX	2
+#define DLM_NODE_FLAG_STOP_RX	3
+#define DLM_NODE_ULP_DELIVERED	4
+	unsigned long flags;
+	wait_queue_head_t shutdown_wait;
+
+	/* dlm tcp termination state */
+#define DLM_CLOSED	1
+#define DLM_ESTABLISHED	2
+#define DLM_FIN_WAIT1	3
+#define DLM_FIN_WAIT2	4
+#define DLM_CLOSE_WAIT	5
+#define DLM_LAST_ACK	6
+#define DLM_CLOSING	7
+	int state;
+	spinlock_t state_lock;
+
+	/* counts how many lockspaces are using this node
+	 * this refcount is necessary to determine if the
+	 * node wants to disconnect.
+	 */
+	int users;
+
+	/* not protected by srcu, node_hash lifetime */
+	void *debugfs;
+
+	struct hlist_node hlist;
+	struct rcu_head rcu;
+};
+
+struct dlm_mhandle {
+	const union dlm_packet *inner_p;
+	struct midcomms_node *node;
+	struct dlm_opts *opts;
+	struct dlm_msg *msg;
+	bool committed;
+	uint32_t seq;
+
+	void (*ack_rcv)(struct midcomms_node *node);
+
+	/* get_mhandle/commit srcu idx exchange */
+	int idx;
+
+	struct list_head list;
+	struct rcu_head rcu;
+};
+
+static struct hlist_head node_hash[CONN_HASH_SIZE];
+static DEFINE_SPINLOCK(nodes_lock);
+DEFINE_STATIC_SRCU(nodes_srcu);
+
+/* This mutex prevents that midcomms_close() is running while
+ * stop() or remove(). As I experienced invalid memory access
+ * behaviours when DLM_DEBUG_FENCE_TERMINATION is enabled and
+ * resetting machines. I will end in some double deletion in nodes
+ * datastructure.
+ */
+static DEFINE_MUTEX(close_lock);
+
+struct kmem_cache *dlm_midcomms_cache_create(void)
+{
+	return kmem_cache_create("dlm_mhandle", sizeof(struct dlm_mhandle),
+				 0, 0, NULL);
+}
+
+static inline const char *dlm_state_str(int state)
+{
+	switch (state) {
+	case DLM_CLOSED:
+		return "CLOSED";
+	case DLM_ESTABLISHED:
+		return "ESTABLISHED";
+	case DLM_FIN_WAIT1:
+		return "FIN_WAIT1";
+	case DLM_FIN_WAIT2:
+		return "FIN_WAIT2";
+	case DLM_CLOSE_WAIT:
+		return "CLOSE_WAIT";
+	case DLM_LAST_ACK:
+		return "LAST_ACK";
+	case DLM_CLOSING:
+		return "CLOSING";
+	default:
+		return "UNKNOWN";
+	}
+}
+
+const char *dlm_midcomms_state(struct midcomms_node *node)
+{
+	return dlm_state_str(node->state);
+}
+
+unsigned long dlm_midcomms_flags(struct midcomms_node *node)
+{
+	return node->flags;
+}
+
+int dlm_midcomms_send_queue_cnt(struct midcomms_node *node)
+{
+	return atomic_read(&node->send_queue_cnt);
+}
+
+uint32_t dlm_midcomms_version(struct midcomms_node *node)
+{
+	return node->version;
+}
+
+static struct midcomms_node *__find_node(int nodeid, int r)
+{
+	struct midcomms_node *node;
+
+	hlist_for_each_entry_rcu(node, &node_hash[r], hlist) {
+		if (node->nodeid == nodeid)
+			return node;
+	}
+
+	return NULL;
+}
+
+static void dlm_mhandle_release(struct rcu_head *rcu)
+{
+	struct dlm_mhandle *mh = container_of(rcu, struct dlm_mhandle, rcu);
+
+	dlm_lowcomms_put_msg(mh->msg);
+	dlm_free_mhandle(mh);
+}
+
+static void dlm_mhandle_delete(struct midcomms_node *node,
+			       struct dlm_mhandle *mh)
+{
+	list_del_rcu(&mh->list);
+	atomic_dec(&node->send_queue_cnt);
+	call_rcu(&mh->rcu, dlm_mhandle_release);
+}
+
+static void dlm_send_queue_flush(struct midcomms_node *node)
+{
+	struct dlm_mhandle *mh;
+
+	pr_debug("flush midcomms send queue of node %d\n", node->nodeid);
+
+	rcu_read_lock();
+	spin_lock(&node->send_queue_lock);
+	list_for_each_entry_rcu(mh, &node->send_queue, list) {
+		dlm_mhandle_delete(node, mh);
+	}
+	spin_unlock(&node->send_queue_lock);
+	rcu_read_unlock();
+}
+
+static void midcomms_node_reset(struct midcomms_node *node)
+{
+	pr_debug("reset node %d\n", node->nodeid);
+
+	node->seq_next = DLM_SEQ_INIT;
+	node->seq_send = DLM_SEQ_INIT;
+	node->version = DLM_VERSION_NOT_SET;
+	node->flags = 0;
+
+	dlm_send_queue_flush(node);
+	node->state = DLM_CLOSED;
+	wake_up(&node->shutdown_wait);
+}
+
+static struct midcomms_node *nodeid2node(int nodeid, gfp_t alloc)
+{
+	struct midcomms_node *node, *tmp;
+	int r = nodeid_hash(nodeid);
+
+	node = __find_node(nodeid, r);
+	if (node || !alloc)
+		return node;
+
+	node = kmalloc(sizeof(*node), alloc);
+	if (!node)
+		return NULL;
+
+	node->nodeid = nodeid;
+	spin_lock_init(&node->state_lock);
+	spin_lock_init(&node->send_queue_lock);
+	atomic_set(&node->send_queue_cnt, 0);
+	INIT_LIST_HEAD(&node->send_queue);
+	init_waitqueue_head(&node->shutdown_wait);
+	node->users = 0;
+	midcomms_node_reset(node);
+
+	spin_lock(&nodes_lock);
+	/* check again if there was somebody else
+	 * earlier here to add the node
+	 */
+	tmp = __find_node(nodeid, r);
+	if (tmp) {
+		spin_unlock(&nodes_lock);
+		kfree(node);
+		return tmp;
+	}
+
+	hlist_add_head_rcu(&node->hlist, &node_hash[r]);
+	spin_unlock(&nodes_lock);
+
+	node->debugfs = dlm_create_debug_comms_file(nodeid, node);
+	return node;
+}
+
+static int dlm_send_ack(int nodeid, uint32_t seq)
+{
+	int mb_len = sizeof(struct dlm_header);
+	struct dlm_header *m_header;
+	struct dlm_msg *msg;
+	char *ppc;
+
+	msg = dlm_lowcomms_new_msg(nodeid, mb_len, GFP_ATOMIC, &ppc,
+				   NULL, NULL);
+	if (!msg)
+		return -ENOMEM;
+
+	m_header = (struct dlm_header *)ppc;
+
+	m_header->h_version = cpu_to_le32(DLM_HEADER_MAJOR | DLM_HEADER_MINOR);
+	m_header->h_nodeid = cpu_to_le32(dlm_our_nodeid());
+	m_header->h_length = cpu_to_le16(mb_len);
+	m_header->h_cmd = DLM_ACK;
+	m_header->u.h_seq = cpu_to_le32(seq);
+
+	dlm_lowcomms_commit_msg(msg);
+	dlm_lowcomms_put_msg(msg);
+
+	return 0;
+}
+
+static int dlm_send_fin(struct midcomms_node *node,
+			void (*ack_rcv)(struct midcomms_node *node))
+{
+	int mb_len = sizeof(struct dlm_header);
+	struct dlm_header *m_header;
+	struct dlm_mhandle *mh;
+	char *ppc;
+
+	mh = dlm_midcomms_get_mhandle(node->nodeid, mb_len, GFP_ATOMIC, &ppc);
+	if (!mh)
+		return -ENOMEM;
+
+	set_bit(DLM_NODE_FLAG_STOP_TX, &node->flags);
+	mh->ack_rcv = ack_rcv;
+
+	m_header = (struct dlm_header *)ppc;
+
+	m_header->h_version = cpu_to_le32(DLM_HEADER_MAJOR | DLM_HEADER_MINOR);
+	m_header->h_nodeid = cpu_to_le32(dlm_our_nodeid());
+	m_header->h_length = cpu_to_le16(mb_len);
+	m_header->h_cmd = DLM_FIN;
+
+	pr_debug("sending fin msg to node %d\n", node->nodeid);
+	dlm_midcomms_commit_mhandle(mh, NULL, 0);
+
+	return 0;
+}
+
+static void dlm_receive_ack(struct midcomms_node *node, uint32_t seq)
+{
+	struct dlm_mhandle *mh;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(mh, &node->send_queue, list) {
+		if (before(mh->seq, seq)) {
+			if (mh->ack_rcv)
+				mh->ack_rcv(node);
+		} else {
+			/* send queue should be ordered */
+			break;
+		}
+	}
+
+	spin_lock(&node->send_queue_lock);
+	list_for_each_entry_rcu(mh, &node->send_queue, list) {
+		if (before(mh->seq, seq)) {
+			dlm_mhandle_delete(node, mh);
+		} else {
+			/* send queue should be ordered */
+			break;
+		}
+	}
+	spin_unlock(&node->send_queue_lock);
+	rcu_read_unlock();
+}
+
+static void dlm_pas_fin_ack_rcv(struct midcomms_node *node)
+{
+	spin_lock(&node->state_lock);
+	pr_debug("receive passive fin ack from node %d with state %s\n",
+		 node->nodeid, dlm_state_str(node->state));
+
+	switch (node->state) {
+	case DLM_LAST_ACK:
+		/* DLM_CLOSED */
+		midcomms_node_reset(node);
+		break;
+	case DLM_CLOSED:
+		/* not valid but somehow we got what we want */
+		wake_up(&node->shutdown_wait);
+		break;
+	default:
+		spin_unlock(&node->state_lock);
+		log_print("%s: unexpected state: %d\n",
+			  __func__, node->state);
+		WARN_ON_ONCE(1);
+		return;
+	}
+	spin_unlock(&node->state_lock);
+}
+
+static void dlm_receive_buffer_3_2_trace(uint32_t seq, union dlm_packet *p)
+{
+	switch (p->header.h_cmd) {
+	case DLM_MSG:
+		trace_dlm_recv_message(seq, &p->message);
+		break;
+	case DLM_RCOM:
+		trace_dlm_recv_rcom(seq, &p->rcom);
+		break;
+	default:
+		break;
+	}
+}
+
+static void dlm_midcomms_receive_buffer(union dlm_packet *p,
+					struct midcomms_node *node,
+					uint32_t seq)
+{
+	if (seq == node->seq_next) {
+		node->seq_next++;
+
+		switch (p->header.h_cmd) {
+		case DLM_FIN:
+			spin_lock(&node->state_lock);
+			pr_debug("receive fin msg from node %d with state %s\n",
+				 node->nodeid, dlm_state_str(node->state));
+
+			switch (node->state) {
+			case DLM_ESTABLISHED:
+				dlm_send_ack(node->nodeid, node->seq_next);
+
+				node->state = DLM_CLOSE_WAIT;
+				pr_debug("switch node %d to state %s\n",
+					 node->nodeid, dlm_state_str(node->state));
+				/* passive shutdown DLM_LAST_ACK case 1
+				 * additional we check if the node is used by
+				 * cluster manager events at all.
+				 */
+				if (node->users == 0) {
+					node->state = DLM_LAST_ACK;
+					pr_debug("switch node %d to state %s case 1\n",
+						 node->nodeid, dlm_state_str(node->state));
+					set_bit(DLM_NODE_FLAG_STOP_RX, &node->flags);
+					dlm_send_fin(node, dlm_pas_fin_ack_rcv);
+				}
+				break;
+			case DLM_FIN_WAIT1:
+				dlm_send_ack(node->nodeid, node->seq_next);
+				node->state = DLM_CLOSING;
+				set_bit(DLM_NODE_FLAG_STOP_RX, &node->flags);
+				pr_debug("switch node %d to state %s\n",
+					 node->nodeid, dlm_state_str(node->state));
+				break;
+			case DLM_FIN_WAIT2:
+				dlm_send_ack(node->nodeid, node->seq_next);
+				midcomms_node_reset(node);
+				pr_debug("switch node %d to state %s\n",
+					 node->nodeid, dlm_state_str(node->state));
+				wake_up(&node->shutdown_wait);
+				break;
+			case DLM_LAST_ACK:
+				/* probably remove_member caught it, do nothing */
+				break;
+			default:
+				spin_unlock(&node->state_lock);
+				log_print("%s: unexpected state: %d\n",
+					  __func__, node->state);
+				WARN_ON_ONCE(1);
+				return;
+			}
+			spin_unlock(&node->state_lock);
+			break;
+		default:
+			WARN_ON_ONCE(test_bit(DLM_NODE_FLAG_STOP_RX, &node->flags));
+			dlm_receive_buffer_3_2_trace(seq, p);
+			dlm_receive_buffer(p, node->nodeid);
+			set_bit(DLM_NODE_ULP_DELIVERED, &node->flags);
+			break;
+		}
+	} else {
+		/* retry to ack message which we already have by sending back
+		 * current node->seq_next number as ack.
+		 */
+		if (seq < node->seq_next)
+			dlm_send_ack(node->nodeid, node->seq_next);
+
+		log_print_ratelimited("ignore dlm msg because seq mismatch, seq: %u, expected: %u, nodeid: %d",
+				      seq, node->seq_next, node->nodeid);
+	}
+}
+
+static struct midcomms_node *
+dlm_midcomms_recv_node_lookup(int nodeid, const union dlm_packet *p,
+			      uint16_t msglen, int (*cb)(struct midcomms_node *node))
+{
+	struct midcomms_node *node = NULL;
+	gfp_t allocation = 0;
+	int ret;
+
+	switch (p->header.h_cmd) {
+	case DLM_RCOM:
+		if (msglen < sizeof(struct dlm_rcom)) {
+			log_print("rcom msg too small: %u, will skip this message from node %d",
+				  msglen, nodeid);
+			return NULL;
+		}
+
+		switch (p->rcom.rc_type) {
+		case cpu_to_le32(DLM_RCOM_NAMES):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_NAMES_REPLY):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_STATUS):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_STATUS_REPLY):
+			node = nodeid2node(nodeid, 0);
+			if (node) {
+				spin_lock(&node->state_lock);
+				if (node->state != DLM_ESTABLISHED)
+					pr_debug("receive begin RCOM msg from node %d with state %s\n",
+						 node->nodeid, dlm_state_str(node->state));
+
+				switch (node->state) {
+				case DLM_CLOSED:
+					node->state = DLM_ESTABLISHED;
+					pr_debug("switch node %d to state %s\n",
+						 node->nodeid, dlm_state_str(node->state));
+					break;
+				case DLM_ESTABLISHED:
+					break;
+				default:
+					/* some invalid state passive shutdown
+					 * was failed, we try to reset and
+					 * hope it will go on.
+					 */
+					log_print("reset node %d because shutdown stuck",
+						  node->nodeid);
+
+					midcomms_node_reset(node);
+					node->state = DLM_ESTABLISHED;
+					break;
+				}
+				spin_unlock(&node->state_lock);
+			}
+
+			allocation = GFP_NOFS;
+			break;
+		default:
+			break;
+		}
+
+		break;
+	default:
+		break;
+	}
+
+	node = nodeid2node(nodeid, allocation);
+	if (!node) {
+		switch (p->header.h_cmd) {
+		case DLM_OPTS:
+			if (msglen < sizeof(struct dlm_opts)) {
+				log_print("opts msg too small: %u, will skip this message from node %d",
+					  msglen, nodeid);
+				return NULL;
+			}
+
+			log_print_ratelimited("received dlm opts message nextcmd %d from node %d in an invalid sequence",
+					      p->opts.o_nextcmd, nodeid);
+			break;
+		default:
+			log_print_ratelimited("received dlm message cmd %d from node %d in an invalid sequence",
+					      p->header.h_cmd, nodeid);
+			break;
+		}
+
+		return NULL;
+	}
+
+	ret = cb(node);
+	if (ret < 0)
+		return NULL;
+
+	return node;
+}
+
+static int dlm_midcomms_version_check_3_2(struct midcomms_node *node)
+{
+	switch (node->version) {
+	case DLM_VERSION_NOT_SET:
+		node->version = DLM_VERSION_3_2;
+		log_print("version 0x%08x for node %d detected", DLM_VERSION_3_2,
+			  node->nodeid);
+		break;
+	case DLM_VERSION_3_2:
+		break;
+	default:
+		log_print_ratelimited("version mismatch detected, assumed 0x%08x but node %d has 0x%08x",
+				      DLM_VERSION_3_2, node->nodeid, node->version);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int dlm_opts_check_msglen(union dlm_packet *p, uint16_t msglen, int nodeid)
+{
+	int len = msglen;
+
+	/* we only trust outer header msglen because
+	 * it's checked against receive buffer length.
+	 */
+	if (len < sizeof(struct dlm_opts))
+		return -1;
+	len -= sizeof(struct dlm_opts);
+
+	if (len < le16_to_cpu(p->opts.o_optlen))
+		return -1;
+	len -= le16_to_cpu(p->opts.o_optlen);
+
+	switch (p->opts.o_nextcmd) {
+	case DLM_FIN:
+		if (len < sizeof(struct dlm_header)) {
+			log_print("fin too small: %d, will skip this message from node %d",
+				  len, nodeid);
+			return -1;
+		}
+
+		break;
+	case DLM_MSG:
+		if (len < sizeof(struct dlm_message)) {
+			log_print("msg too small: %d, will skip this message from node %d",
+				  msglen, nodeid);
+			return -1;
+		}
+
+		break;
+	case DLM_RCOM:
+		if (len < sizeof(struct dlm_rcom)) {
+			log_print("rcom msg too small: %d, will skip this message from node %d",
+				  len, nodeid);
+			return -1;
+		}
+
+		break;
+	default:
+		log_print("unsupported o_nextcmd received: %u, will skip this message from node %d",
+			  p->opts.o_nextcmd, nodeid);
+		return -1;
+	}
+
+	return 0;
+}
+
+static void dlm_midcomms_receive_buffer_3_2(union dlm_packet *p, int nodeid)
+{
+	uint16_t msglen = le16_to_cpu(p->header.h_length);
+	struct midcomms_node *node;
+	uint32_t seq;
+	int ret, idx;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = dlm_midcomms_recv_node_lookup(nodeid, p, msglen,
+					     dlm_midcomms_version_check_3_2);
+	if (!node)
+		goto out;
+
+	switch (p->header.h_cmd) {
+	case DLM_RCOM:
+		/* these rcom message we use to determine version.
+		 * they have their own retransmission handling and
+		 * are the first messages of dlm.
+		 *
+		 * length already checked.
+		 */
+		switch (p->rcom.rc_type) {
+		case cpu_to_le32(DLM_RCOM_NAMES):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_NAMES_REPLY):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_STATUS):
+			fallthrough;
+		case cpu_to_le32(DLM_RCOM_STATUS_REPLY):
+			break;
+		default:
+			log_print("unsupported rcom type received: %u, will skip this message from node %d",
+				  le32_to_cpu(p->rcom.rc_type), nodeid);
+			goto out;
+		}
+
+		WARN_ON_ONCE(test_bit(DLM_NODE_FLAG_STOP_RX, &node->flags));
+		dlm_receive_buffer(p, nodeid);
+		break;
+	case DLM_OPTS:
+		seq = le32_to_cpu(p->header.u.h_seq);
+
+		ret = dlm_opts_check_msglen(p, msglen, nodeid);
+		if (ret < 0) {
+			log_print("opts msg too small: %u, will skip this message from node %d",
+				  msglen, nodeid);
+			goto out;
+		}
+
+		p = (union dlm_packet *)((unsigned char *)p->opts.o_opts +
+					 le16_to_cpu(p->opts.o_optlen));
+
+		/* recheck inner msglen just if it's not garbage */
+		msglen = le16_to_cpu(p->header.h_length);
+		switch (p->header.h_cmd) {
+		case DLM_RCOM:
+			if (msglen < sizeof(struct dlm_rcom)) {
+				log_print("inner rcom msg too small: %u, will skip this message from node %d",
+					  msglen, nodeid);
+				goto out;
+			}
+
+			break;
+		case DLM_MSG:
+			if (msglen < sizeof(struct dlm_message)) {
+				log_print("inner msg too small: %u, will skip this message from node %d",
+					  msglen, nodeid);
+				goto out;
+			}
+
+			break;
+		case DLM_FIN:
+			if (msglen < sizeof(struct dlm_header)) {
+				log_print("inner fin too small: %u, will skip this message from node %d",
+					  msglen, nodeid);
+				goto out;
+			}
+
+			break;
+		default:
+			log_print("unsupported inner h_cmd received: %u, will skip this message from node %d",
+				  msglen, nodeid);
+			goto out;
+		}
+
+		dlm_midcomms_receive_buffer(p, node, seq);
+		break;
+	case DLM_ACK:
+		seq = le32_to_cpu(p->header.u.h_seq);
+		dlm_receive_ack(node, seq);
+		break;
+	default:
+		log_print("unsupported h_cmd received: %u, will skip this message from node %d",
+			  p->header.h_cmd, nodeid);
+		break;
+	}
+
+out:
+	srcu_read_unlock(&nodes_srcu, idx);
+}
+
+static int dlm_midcomms_version_check_3_1(struct midcomms_node *node)
+{
+	switch (node->version) {
+	case DLM_VERSION_NOT_SET:
+		node->version = DLM_VERSION_3_1;
+		log_print("version 0x%08x for node %d detected", DLM_VERSION_3_1,
+			  node->nodeid);
+		break;
+	case DLM_VERSION_3_1:
+		break;
+	default:
+		log_print_ratelimited("version mismatch detected, assumed 0x%08x but node %d has 0x%08x",
+				      DLM_VERSION_3_1, node->nodeid, node->version);
+		return -1;
+	}
+
+	return 0;
+}
+
+static void dlm_midcomms_receive_buffer_3_1(union dlm_packet *p, int nodeid)
+{
+	uint16_t msglen = le16_to_cpu(p->header.h_length);
+	struct midcomms_node *node;
+	int idx;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = dlm_midcomms_recv_node_lookup(nodeid, p, msglen,
+					     dlm_midcomms_version_check_3_1);
+	if (!node) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+	srcu_read_unlock(&nodes_srcu, idx);
+
+	switch (p->header.h_cmd) {
+	case DLM_RCOM:
+		/* length already checked */
+		break;
+	case DLM_MSG:
+		if (msglen < sizeof(struct dlm_message)) {
+			log_print("msg too small: %u, will skip this message from node %d",
+				  msglen, nodeid);
+			return;
+		}
+
+		break;
+	default:
+		log_print("unsupported h_cmd received: %u, will skip this message from node %d",
+			  p->header.h_cmd, nodeid);
+		return;
+	}
+
+	dlm_receive_buffer(p, nodeid);
+}
+
+/*
+ * Called from the low-level comms layer to process a buffer of
+ * commands.
+ */
+
+int dlm_process_incoming_buffer(int nodeid, unsigned char *buf, int len)
+{
+	const unsigned char *ptr = buf;
+	const struct dlm_header *hd;
+	uint16_t msglen;
+	int ret = 0;
+
+	while (len >= sizeof(struct dlm_header)) {
+		hd = (struct dlm_header *)ptr;
+
+		/* no message should be more than DLM_MAX_SOCKET_BUFSIZE or
+		 * less than dlm_header size.
+		 *
+		 * Some messages does not have a 8 byte length boundary yet
+		 * which can occur in a unaligned memory access of some dlm
+		 * messages. However this problem need to be fixed at the
+		 * sending side, for now it seems nobody run into architecture
+		 * related issues yet but it slows down some processing.
+		 * Fixing this issue should be scheduled in future by doing
+		 * the next major version bump.
+		 */
+		msglen = le16_to_cpu(hd->h_length);
+		if (msglen > DLM_MAX_SOCKET_BUFSIZE ||
+		    msglen < sizeof(struct dlm_header)) {
+			log_print("received invalid length header: %u from node %d, will abort message parsing",
+				  msglen, nodeid);
+			return -EBADMSG;
+		}
+
+		/* caller will take care that leftover
+		 * will be parsed next call with more data
+		 */
+		if (msglen > len)
+			break;
+
+		switch (hd->h_version) {
+		case cpu_to_le32(DLM_VERSION_3_1):
+			dlm_midcomms_receive_buffer_3_1((union dlm_packet *)ptr, nodeid);
+			break;
+		case cpu_to_le32(DLM_VERSION_3_2):
+			dlm_midcomms_receive_buffer_3_2((union dlm_packet *)ptr, nodeid);
+			break;
+		default:
+			log_print("received invalid version header: %u from node %d, will skip this message",
+				  le32_to_cpu(hd->h_version), nodeid);
+			break;
+		}
+
+		ret += msglen;
+		len -= msglen;
+		ptr += msglen;
+	}
+
+	return ret;
+}
+
+void dlm_midcomms_receive_done(int nodeid)
+{
+	struct midcomms_node *node;
+	int idx;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = nodeid2node(nodeid, 0);
+	if (!node) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	/* old protocol, we do nothing */
+	switch (node->version) {
+	case DLM_VERSION_3_2:
+		break;
+	default:
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	/* do nothing if we didn't delivered stateful to ulp */
+	if (!test_and_clear_bit(DLM_NODE_ULP_DELIVERED,
+				&node->flags)) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	spin_lock(&node->state_lock);
+	/* we only ack if state is ESTABLISHED */
+	switch (node->state) {
+	case DLM_ESTABLISHED:
+		spin_unlock(&node->state_lock);
+		dlm_send_ack(node->nodeid, node->seq_next);
+		break;
+	default:
+		spin_unlock(&node->state_lock);
+		/* do nothing FIN has it's own ack send */
+		break;
+	}
+	srcu_read_unlock(&nodes_srcu, idx);
+}
+
+void dlm_midcomms_unack_msg_resend(int nodeid)
+{
+	struct midcomms_node *node;
+	struct dlm_mhandle *mh;
+	int idx, ret;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = nodeid2node(nodeid, 0);
+	if (!node) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	/* old protocol, we don't support to retransmit on failure */
+	switch (node->version) {
+	case DLM_VERSION_3_2:
+		break;
+	default:
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(mh, &node->send_queue, list) {
+		if (!mh->committed)
+			continue;
+
+		ret = dlm_lowcomms_resend_msg(mh->msg);
+		if (!ret)
+			log_print_ratelimited("retransmit dlm msg, seq %u, nodeid %d",
+					      mh->seq, node->nodeid);
+	}
+	rcu_read_unlock();
+	srcu_read_unlock(&nodes_srcu, idx);
+}
+
+static void dlm_fill_opts_header(struct dlm_opts *opts, uint16_t inner_len,
+				 uint32_t seq)
+{
+	opts->o_header.h_cmd = DLM_OPTS;
+	opts->o_header.h_version = cpu_to_le32(DLM_HEADER_MAJOR | DLM_HEADER_MINOR);
+	opts->o_header.h_nodeid = cpu_to_le32(dlm_our_nodeid());
+	opts->o_header.h_length = cpu_to_le16(DLM_MIDCOMMS_OPT_LEN + inner_len);
+	opts->o_header.u.h_seq = cpu_to_le32(seq);
+}
+
+static void midcomms_new_msg_cb(void *data)
+{
+	struct dlm_mhandle *mh = data;
+
+	atomic_inc(&mh->node->send_queue_cnt);
+
+	spin_lock(&mh->node->send_queue_lock);
+	list_add_tail_rcu(&mh->list, &mh->node->send_queue);
+	spin_unlock(&mh->node->send_queue_lock);
+
+	mh->seq = mh->node->seq_send++;
+}
+
+static struct dlm_msg *dlm_midcomms_get_msg_3_2(struct dlm_mhandle *mh, int nodeid,
+						int len, gfp_t allocation, char **ppc)
+{
+	struct dlm_opts *opts;
+	struct dlm_msg *msg;
+
+	msg = dlm_lowcomms_new_msg(nodeid, len + DLM_MIDCOMMS_OPT_LEN,
+				   allocation, ppc, midcomms_new_msg_cb, mh);
+	if (!msg)
+		return NULL;
+
+	opts = (struct dlm_opts *)*ppc;
+	mh->opts = opts;
+
+	/* add possible options here */
+	dlm_fill_opts_header(opts, len, mh->seq);
+
+	*ppc += sizeof(*opts);
+	mh->inner_p = (const union dlm_packet *)*ppc;
+	return msg;
+}
+
+/* avoid false positive for nodes_srcu, unlock happens in
+ * dlm_midcomms_commit_mhandle which is a must call if success
+ */
+#ifndef __CHECKER__
+struct dlm_mhandle *dlm_midcomms_get_mhandle(int nodeid, int len,
+					     gfp_t allocation, char **ppc)
+{
+	struct midcomms_node *node;
+	struct dlm_mhandle *mh;
+	struct dlm_msg *msg;
+	int idx;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = nodeid2node(nodeid, 0);
+	if (!node) {
+		WARN_ON_ONCE(1);
+		goto err;
+	}
+
+	/* this is a bug, however we going on and hope it will be resolved */
+	WARN_ON_ONCE(test_bit(DLM_NODE_FLAG_STOP_TX, &node->flags));
+
+	mh = dlm_allocate_mhandle();
+	if (!mh)
+		goto err;
+
+	mh->committed = false;
+	mh->ack_rcv = NULL;
+	mh->idx = idx;
+	mh->node = node;
+
+	switch (node->version) {
+	case DLM_VERSION_3_1:
+		msg = dlm_lowcomms_new_msg(nodeid, len, allocation, ppc,
+					   NULL, NULL);
+		if (!msg) {
+			dlm_free_mhandle(mh);
+			goto err;
+		}
+
+		break;
+	case DLM_VERSION_3_2:
+		msg = dlm_midcomms_get_msg_3_2(mh, nodeid, len, allocation,
+					       ppc);
+		if (!msg) {
+			dlm_free_mhandle(mh);
+			goto err;
+		}
+
+		break;
+	default:
+		dlm_free_mhandle(mh);
+		WARN_ON_ONCE(1);
+		goto err;
+	}
+
+	mh->msg = msg;
+
+	/* keep in mind that is a must to call
+	 * dlm_midcomms_commit_msg() which releases
+	 * nodes_srcu using mh->idx which is assumed
+	 * here that the application will call it.
+	 */
+	return mh;
+
+err:
+	srcu_read_unlock(&nodes_srcu, idx);
+	return NULL;
+}
+#endif
+
+static void dlm_midcomms_commit_msg_3_2_trace(const struct dlm_mhandle *mh,
+					      const void *name, int namelen)
+{
+	switch (mh->inner_p->header.h_cmd) {
+	case DLM_MSG:
+		trace_dlm_send_message(mh->seq, &mh->inner_p->message,
+				       name, namelen);
+		break;
+	case DLM_RCOM:
+		trace_dlm_send_rcom(mh->seq, &mh->inner_p->rcom);
+		break;
+	default:
+		/* nothing to trace */
+		break;
+	}
+}
+
+static void dlm_midcomms_commit_msg_3_2(struct dlm_mhandle *mh,
+					const void *name, int namelen)
+{
+	/* nexthdr chain for fast lookup */
+	mh->opts->o_nextcmd = mh->inner_p->header.h_cmd;
+	mh->committed = true;
+	dlm_midcomms_commit_msg_3_2_trace(mh, name, namelen);
+	dlm_lowcomms_commit_msg(mh->msg);
+}
+
+/* avoid false positive for nodes_srcu, lock was happen in
+ * dlm_midcomms_get_mhandle
+ */
+#ifndef __CHECKER__
+void dlm_midcomms_commit_mhandle(struct dlm_mhandle *mh,
+				 const void *name, int namelen)
+{
+
+	switch (mh->node->version) {
+	case DLM_VERSION_3_1:
+		srcu_read_unlock(&nodes_srcu, mh->idx);
+
+		dlm_lowcomms_commit_msg(mh->msg);
+		dlm_lowcomms_put_msg(mh->msg);
+		/* mh is not part of rcu list in this case */
+		dlm_free_mhandle(mh);
+		break;
+	case DLM_VERSION_3_2:
+		/* held rcu read lock here, because we sending the
+		 * dlm message out, when we do that we could receive
+		 * an ack back which releases the mhandle and we
+		 * get a use after free.
+		 */
+		rcu_read_lock();
+		dlm_midcomms_commit_msg_3_2(mh, name, namelen);
+		srcu_read_unlock(&nodes_srcu, mh->idx);
+		rcu_read_unlock();
+		break;
+	default:
+		srcu_read_unlock(&nodes_srcu, mh->idx);
+		WARN_ON_ONCE(1);
+		break;
+	}
+}
+#endif
+
+int dlm_midcomms_start(void)
+{
+	return dlm_lowcomms_start();
+}
+
+void dlm_midcomms_stop(void)
+{
+	dlm_lowcomms_stop();
+}
+
+void dlm_midcomms_init(void)
+{
+	int i;
+
+	for (i = 0; i < CONN_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&node_hash[i]);
+
+	dlm_lowcomms_init();
+}
+
+void dlm_midcomms_exit(void)
+{
+	dlm_lowcomms_exit();
+}
+
+static void dlm_act_fin_ack_rcv(struct midcomms_node *node)
+{
+	spin_lock(&node->state_lock);
+	pr_debug("receive active fin ack from node %d with state %s\n",
+		 node->nodeid, dlm_state_str(node->state));
+
+	switch (node->state) {
+	case DLM_FIN_WAIT1:
+		node->state = DLM_FIN_WAIT2;
+		pr_debug("switch node %d to state %s\n",
+			 node->nodeid, dlm_state_str(node->state));
+		break;
+	case DLM_CLOSING:
+		midcomms_node_reset(node);
+		pr_debug("switch node %d to state %s\n",
+			 node->nodeid, dlm_state_str(node->state));
+		wake_up(&node->shutdown_wait);
+		break;
+	case DLM_CLOSED:
+		/* not valid but somehow we got what we want */
+		wake_up(&node->shutdown_wait);
+		break;
+	default:
+		spin_unlock(&node->state_lock);
+		log_print("%s: unexpected state: %d\n",
+			  __func__, node->state);
+		WARN_ON_ONCE(1);
+		return;
+	}
+	spin_unlock(&node->state_lock);
+}
+
+void dlm_midcomms_add_member(int nodeid)
+{
+	struct midcomms_node *node;
+	int idx;
+
+	if (nodeid == dlm_our_nodeid())
+		return;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = nodeid2node(nodeid, GFP_NOFS);
+	if (!node) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	spin_lock(&node->state_lock);
+	if (!node->users) {
+		pr_debug("receive add member from node %d with state %s\n",
+			 node->nodeid, dlm_state_str(node->state));
+		switch (node->state) {
+		case DLM_ESTABLISHED:
+			break;
+		case DLM_CLOSED:
+			node->state = DLM_ESTABLISHED;
+			pr_debug("switch node %d to state %s\n",
+				 node->nodeid, dlm_state_str(node->state));
+			break;
+		default:
+			/* some invalid state passive shutdown
+			 * was failed, we try to reset and
+			 * hope it will go on.
+			 */
+			log_print("reset node %d because shutdown stuck",
+				  node->nodeid);
+
+			midcomms_node_reset(node);
+			node->state = DLM_ESTABLISHED;
+			break;
+		}
+	}
+
+	node->users++;
+	pr_debug("node %d users inc count %d\n", nodeid, node->users);
+	spin_unlock(&node->state_lock);
+
+	srcu_read_unlock(&nodes_srcu, idx);
+}
+
+void dlm_midcomms_remove_member(int nodeid)
+{
+	struct midcomms_node *node;
+	int idx;
+
+	if (nodeid == dlm_our_nodeid())
+		return;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	node = nodeid2node(nodeid, 0);
+	if (!node) {
+		srcu_read_unlock(&nodes_srcu, idx);
+		return;
+	}
+
+	spin_lock(&node->state_lock);
+	node->users--;
+	pr_debug("node %d users dec count %d\n", nodeid, node->users);
+
+	/* hitting users count to zero means the
+	 * other side is running dlm_midcomms_stop()
+	 * we meet us to have a clean disconnect.
+	 */
+	if (node->users == 0) {
+		pr_debug("receive remove member from node %d with state %s\n",
+			 node->nodeid, dlm_state_str(node->state));
+		switch (node->state) {
+		case DLM_ESTABLISHED:
+			break;
+		case DLM_CLOSE_WAIT:
+			/* passive shutdown DLM_LAST_ACK case 2 */
+			node->state = DLM_LAST_ACK;
+			pr_debug("switch node %d to state %s case 2\n",
+				 node->nodeid, dlm_state_str(node->state));
+			set_bit(DLM_NODE_FLAG_STOP_RX, &node->flags);
+			dlm_send_fin(node, dlm_pas_fin_ack_rcv);
+			break;
+		case DLM_LAST_ACK:
+			/* probably receive fin caught it, do nothing */
+			break;
+		case DLM_CLOSED:
+			/* already gone, do nothing */
+			break;
+		default:
+			log_print("%s: unexpected state: %d\n",
+				  __func__, node->state);
+			break;
+		}
+	}
+	spin_unlock(&node->state_lock);
+
+	srcu_read_unlock(&nodes_srcu, idx);
+}
+
+static void midcomms_node_release(struct rcu_head *rcu)
+{
+	struct midcomms_node *node = container_of(rcu, struct midcomms_node, rcu);
+
+	WARN_ON_ONCE(atomic_read(&node->send_queue_cnt));
+	dlm_send_queue_flush(node);
+	kfree(node);
+}
+
+static void midcomms_shutdown(struct midcomms_node *node)
+{
+	int ret;
+
+	/* old protocol, we don't wait for pending operations */
+	switch (node->version) {
+	case DLM_VERSION_3_2:
+		break;
+	default:
+		return;
+	}
+
+	spin_lock(&node->state_lock);
+	pr_debug("receive active shutdown for node %d with state %s\n",
+		 node->nodeid, dlm_state_str(node->state));
+	switch (node->state) {
+	case DLM_ESTABLISHED:
+		node->state = DLM_FIN_WAIT1;
+		pr_debug("switch node %d to state %s case 2\n",
+			 node->nodeid, dlm_state_str(node->state));
+		dlm_send_fin(node, dlm_act_fin_ack_rcv);
+		break;
+	case DLM_CLOSED:
+		/* we have what we want */
+		spin_unlock(&node->state_lock);
+		return;
+	default:
+		/* busy to enter DLM_FIN_WAIT1, wait until passive
+		 * done in shutdown_wait to enter DLM_CLOSED.
+		 */
+		break;
+	}
+	spin_unlock(&node->state_lock);
+
+	if (DLM_DEBUG_FENCE_TERMINATION)
+		msleep(5000);
+
+	/* wait for other side dlm + fin */
+	ret = wait_event_timeout(node->shutdown_wait,
+				 node->state == DLM_CLOSED ||
+				 test_bit(DLM_NODE_FLAG_CLOSE, &node->flags),
+				 DLM_SHUTDOWN_TIMEOUT);
+	if (!ret || test_bit(DLM_NODE_FLAG_CLOSE, &node->flags)) {
+		pr_debug("active shutdown timed out for node %d with state %s\n",
+			 node->nodeid, dlm_state_str(node->state));
+		midcomms_node_reset(node);
+		return;
+	}
+
+	pr_debug("active shutdown done for node %d with state %s\n",
+		 node->nodeid, dlm_state_str(node->state));
+}
+
+void dlm_midcomms_shutdown(void)
+{
+	struct midcomms_node *node;
+	int i, idx;
+
+	mutex_lock(&close_lock);
+	idx = srcu_read_lock(&nodes_srcu);
+	for (i = 0; i < CONN_HASH_SIZE; i++) {
+		hlist_for_each_entry_rcu(node, &node_hash[i], hlist) {
+			midcomms_shutdown(node);
+
+			dlm_delete_debug_comms_file(node->debugfs);
+
+			spin_lock(&nodes_lock);
+			hlist_del_rcu(&node->hlist);
+			spin_unlock(&nodes_lock);
+
+			call_srcu(&nodes_srcu, &node->rcu, midcomms_node_release);
+		}
+	}
+	srcu_read_unlock(&nodes_srcu, idx);
+	mutex_unlock(&close_lock);
+
+	dlm_lowcomms_shutdown();
+}
+
+int dlm_midcomms_close(int nodeid)
+{
+	struct midcomms_node *node;
+	int idx, ret;
+
+	if (nodeid == dlm_our_nodeid())
+		return 0;
+
+	idx = srcu_read_lock(&nodes_srcu);
+	/* Abort pending close/remove operation */
+	node = nodeid2node(nodeid, 0);
+	if (node) {
+		/* let shutdown waiters leave */
+		set_bit(DLM_NODE_FLAG_CLOSE, &node->flags);
+		wake_up(&node->shutdown_wait);
+	}
+	srcu_read_unlock(&nodes_srcu, idx);
+
+	synchronize_srcu(&nodes_srcu);
+
+	idx = srcu_read_lock(&nodes_srcu);
+	mutex_lock(&close_lock);
+	node = nodeid2node(nodeid, 0);
+	if (!node) {
+		mutex_unlock(&close_lock);
+		srcu_read_unlock(&nodes_srcu, idx);
+		return dlm_lowcomms_close(nodeid);
+	}
+
+	ret = dlm_lowcomms_close(nodeid);
+	spin_lock(&node->state_lock);
+	midcomms_node_reset(node);
+	spin_unlock(&node->state_lock);
+	srcu_read_unlock(&nodes_srcu, idx);
+	mutex_unlock(&close_lock);
+
+	return ret;
+}
+
+/* debug functionality to send raw dlm msg from user space */
+struct dlm_rawmsg_data {
+	struct midcomms_node *node;
+	void *buf;
+};
+
+static void midcomms_new_rawmsg_cb(void *data)
+{
+	struct dlm_rawmsg_data *rd = data;
+	struct dlm_header *h = rd->buf;
+
+	switch (h->h_version) {
+	case cpu_to_le32(DLM_VERSION_3_1):
+		break;
+	default:
+		switch (h->h_cmd) {
+		case DLM_OPTS:
+			if (!h->u.h_seq)
+				h->u.h_seq = cpu_to_le32(rd->node->seq_send++);
+			break;
+		default:
+			break;
+		}
+		break;
+	}
+}
+
+int dlm_midcomms_rawmsg_send(struct midcomms_node *node, void *buf,
+			     int buflen)
+{
+	struct dlm_rawmsg_data rd;
+	struct dlm_msg *msg;
+	char *msgbuf;
+
+	rd.node = node;
+	rd.buf = buf;
+
+	msg = dlm_lowcomms_new_msg(node->nodeid, buflen, GFP_NOFS,
+				   &msgbuf, midcomms_new_rawmsg_cb, &rd);
+	if (!msg)
+		return -ENOMEM;
+
+	memcpy(msgbuf, buf, buflen);
+	dlm_lowcomms_commit_msg(msg);
+	return 0;
+}
+