splitted net

7 files changed, 765 insertions, 604 deletions

diff --git a/src/kernel/mq.c b/src/kernel/mq.c
index b1c1e99..94f06f2 100644
--- a/src/kernel/mq.c
+++ b/src/kernel/mq.c
@@ -19,7 +19,7 @@
  */
 
 #include "mq.h"
-#include "net.h"
+#include "net-txrx.h"
 
 #include <linux/wait.h>
 #include <linux/blk-mq.h>
diff --git a/src/kernel/net-txrx.c b/src/kernel/net-txrx.c
new file mode 100644
index 0000000..d905ce9
--- /dev/null
+++ b/src/kernel/net-txrx.c
@@ -0,0 +1,608 @@
+/*
+ * This file is part of the Distributed Network Block Device 3
+ *
+ * Copyright(c) 2019 Frederic Robra <frederic@robra.org>
+ * Parts copyright 2011-2012 Johann Latocha <johann@latocha.de>
+ *
+ * This file may be licensed under the terms of of the
+ * GNU General Public License Version 2 (the ``GPL'').
+ *
+ * Software distributed under the License is distributed
+ * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
+ * express or implied. See the GPL for the specific language
+ * governing rights and limitations.
+ *
+ * You should have received a copy of the GPL along with this
+ * program. If not, go to http://www.gnu.org/licenses/gpl.html
+ * or write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "net-txrx.h"
+#include "utils.h"
+#include "clientconfig.h"
+#include "mq.h"
+
+#include <net/sock.h>
+
+
+
+#define DNBD3_REQ_OP_SPECIAL REQ_OP_DRV_IN
+#define DNBD3_REQ_OP_CONNECT REQ_OP_DRV_OUT
+
+#define dnbd3_cmd_to_op_special(req, cmd) \
+	(req)->cmd_flags = DNBD3_REQ_OP_SPECIAL | ((cmd) << REQ_FLAG_BITS)
+
+#define dnbd3_op_special_to_cmd(req) \
+	((req)->cmd_flags >> REQ_FLAG_BITS)
+
+#define dnbd3_connect_to_req(req) \
+	(req)->cmd_flags = DNBD3_REQ_OP_CONNECT \
+			| ((CMD_SELECT_IMAGE) << REQ_FLAG_BITS)
+
+#define dnbd3_test_block_to_req(req) \
+	do { \
+		(req)->cmd_flags = REQ_OP_READ; \
+		(req)->__data_len = RTT_BLOCK_SIZE; \
+		(req)->__sector = 0; \
+	} while (0)
+
+
+#define REQUEST_TIMEOUT \
+	(HZ * SOCKET_TIMEOUT_CLIENT_DATA)
+
+
+#define dnbd3_init_msghdr(h) \
+	do { \
+		(h).msg_name = NULL; \
+		(h).msg_namelen = 0; \
+		(h).msg_control = NULL; \
+		(h).msg_controllen = 0; \
+		(h).msg_flags = MSG_WAITALL | MSG_NOSIGNAL; \
+	} while (0)
+
+
+
+/*
+ * Methods for request and receive commands
+ */
+
+
+/**
+ * dnbd3_to_handle - convert tag and cookie to handle
+ * @tag: the tag to convert
+ * @cookie: the cookie to convert
+ */
+static inline uint64_t dnbd3_to_handle(uint32_t tag, uint32_t cookie) {
+	return ((uint64_t) tag << 32) | cookie;
+}
+
+/**
+ * dnbd3_tag_from_handle - get tag from handle
+ * @handle: the handle
+ */
+static inline uint32_t dnbd3_tag_from_handle(uint64_t handle) {
+	return (uint32_t)(handle >> 32);
+}
+
+/**
+ * dnbd3_cookie_from_handle - get cookie from handle
+ * @handle: the handle
+ */
+static inline uint32_t dnbd3_cookie_from_handle(uint64_t handle) {
+	return (uint32_t) handle;
+}
+
+/**
+ * dnbd3_send_request - send a request
+ * @sock: the socket where the request is send
+ * @req: the request to send
+ * @cmd: optional - the dnbd3_cmd from mq
+ *
+ * the tx_lock of the socket must be held
+ */
+int dnbd3_send_request(struct dnbd3_sock *sock, struct request *req,
+		struct dnbd3_cmd *cmd)
+{
+	dnbd3_request_t request;
+	struct msghdr msg;
+	struct kvec iov[2];
+	size_t iov_num = 1;
+	size_t lng;
+	int result;
+	uint32_t tag;
+	uint64_t handle;
+	serialized_buffer_t payload_buffer;
+	sock->pending = req;
+	dnbd3_init_msghdr(msg);
+
+	request.magic = dnbd3_packet_magic;
+
+	switch (req_op(req)) {
+	case REQ_OP_READ:
+		debug_sock(sock, "request operation read");
+		request.cmd = CMD_GET_BLOCK;
+		request.offset = blk_rq_pos(req) << 9; // * 512
+		request.size = blk_rq_bytes(req);
+		break;
+	case DNBD3_REQ_OP_SPECIAL:
+		debug_sock(sock, "request operation special");
+		request.cmd = dnbd3_op_special_to_cmd(req);
+		request.size = 0;
+		break;
+	case DNBD3_REQ_OP_CONNECT:
+		debug_sock(sock, "request operation connect to %s",
+				sock->device->imgname);
+		request.cmd = CMD_SELECT_IMAGE;
+		serializer_reset_write(&payload_buffer);
+		serializer_put_uint16(&payload_buffer, PROTOCOL_VERSION);
+		serializer_put_string(&payload_buffer, sock->device->imgname);
+		serializer_put_uint16(&payload_buffer, sock->device->rid);
+		serializer_put_uint8(&payload_buffer, 0); // is_server = false
+		iov[1].iov_base = &payload_buffer;
+		request.size = serializer_get_written_length(&payload_buffer);
+		iov[1].iov_len = request.size;
+		iov_num = 2;
+		break;
+	default:
+		return -EIO;
+	}
+	sock->cookie++;
+	if (cmd != NULL) {
+		cmd->cookie = sock->cookie;
+		tag = blk_mq_unique_tag(req);
+		handle = dnbd3_to_handle(tag, sock->cookie);
+	} else {
+		handle = sock->cookie;
+	}
+	memcpy(&request.handle, &handle, sizeof(handle));
+
+	fixup_request(request);
+	iov[0].iov_base = &request;
+	iov[0].iov_len = sizeof(request);
+	lng = iov_num == 1 ? iov[0].iov_len : iov[0].iov_len + iov[1].iov_len;
+	result = kernel_sendmsg(sock->sock, &msg, iov, iov_num, lng);
+	if (result != lng) {
+		error_sock(sock, "connection to server lost");
+		if (cmd) {
+			dnbd3_requeue_cmd(cmd);
+		}
+		sock->panic = true;
+		sock->server->failures++;
+		goto error;
+	}
+
+error:
+	sock->pending = NULL;
+	return result;
+}
+
+
+/**
+ * dnbd3_send_request_cmd - send a dndb3 cmd
+ * @sock: the socket where the request is send
+ * @dnbd3_cmd: the dnbd3 cmd to send
+ */
+int dnbd3_send_request_cmd(struct dnbd3_sock *sock, uint16_t dnbd3_cmd)
+{
+	int result;
+	struct request *req = kmalloc(sizeof(struct request), GFP_KERNEL);
+	if (!req) {
+		error_sock(sock, "kmalloc failed");
+		result = -EIO;
+		goto error;
+	}
+
+	switch (dnbd3_cmd) {
+	case CMD_KEEPALIVE:
+	case CMD_GET_SERVERS:
+		dnbd3_cmd_to_op_special(req, dnbd3_cmd);
+		break;
+	case CMD_SELECT_IMAGE:
+		dnbd3_connect_to_req(req);
+		break;
+	case CMD_GET_BLOCK:
+		dnbd3_test_block_to_req(req);
+		break;
+	default:
+		warn_sock(sock, "unsupported command %d", dnbd3_cmd);
+		result = -EINVAL;
+		goto error;
+	}
+
+	mutex_lock(&sock->tx_lock);
+	sock->pending = req;
+	result = dnbd3_send_request(sock, req, NULL);
+	mutex_unlock(&sock->tx_lock);
+
+error:
+	if (req) {
+		kfree(req);
+	}
+	return result;
+}
+
+/**
+ * dnbd3_receive_cmd - receive a command
+ * @sock: the socket where the request is received
+ * @reply: an unused reply will be filled with the reply of the server
+ *
+ * this method should be called directly after the dnbd3_send_request_ method
+ */
+int dnbd3_receive_cmd(struct dnbd3_sock *sock, dnbd3_reply_t *reply)
+{
+	int result;
+	struct msghdr msg;
+	struct kvec iov;
+	dnbd3_init_msghdr(msg);
+	iov.iov_base = reply;
+	iov.iov_len = sizeof(dnbd3_reply_t);
+	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
+			msg.msg_flags);
+	if (result <= 0) {
+		return result;
+	}
+	fixup_reply(dnbd3_reply);
+
+	if (reply->magic != dnbd3_packet_magic) {
+		error_sock(sock, "receive cmd wrong magic packet");
+		return -EIO;
+	}
+
+	if (reply->cmd == 0) {
+		error_sock(sock, "receive command was 0");
+		return -EIO;
+	}
+	return result;
+}
+
+static int dnbd3_clear_socket(struct dnbd3_sock *sock, dnbd3_reply_t *reply,
+		int remaining)
+{
+	int result = 0;
+	char *buf;
+	struct kvec iov;
+	struct msghdr msg;
+	dnbd3_init_msghdr(msg);
+	warn_sock(sock, "clearing socket %d bytes", remaining);
+	buf = kmalloc(RTT_BLOCK_SIZE, GFP_KERNEL);
+	if (!buf) {
+		error_sock(sock, "kmalloc failed");
+		return -EIO;
+	}
+	/* hold the tx_lock so no new requests are send */
+	mutex_lock(&sock->tx_lock);
+	iov.iov_base = buf;
+	iov.iov_len = RTT_BLOCK_SIZE;
+	while (remaining > 0) {
+		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
+				msg.msg_flags);
+		if (result <= 0) {
+			goto error;
+		}
+		remaining -= result;
+	}
+
+	debug_sock(sock, "cleared socket");
+error:
+	mutex_unlock(&sock->tx_lock);
+	if (buf) {
+		kfree(buf);
+	}
+	return result;
+}
+
+/**
+ * dnbd3_receive_cmd_get_block_mq - receive a block for mq
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * this method copies the data to user space according to the request which is
+ * encoded in the handle by the send request method and decoded here.
+ */
+int dnbd3_receive_cmd_get_block_mq(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply)
+{
+	struct dnbd3_cmd *cmd;
+	struct msghdr msg;
+	struct request *req = NULL;
+	struct kvec iov;
+	struct req_iterator iter;
+	struct bio_vec bvec_inst;
+	struct dnbd3_device *dev = sock->device;
+	struct bio_vec *bvec = &bvec_inst;
+	sigset_t blocked, oldset;
+	void *kaddr;
+	uint32_t tag, cookie;
+	uint16_t hwq;
+	uint32_t remaining = reply->size;
+	int result = 0;
+	uint64_t handle;
+	dnbd3_init_msghdr(msg);
+
+	memcpy(&handle, &reply->handle, sizeof(handle));
+	cookie = dnbd3_cookie_from_handle(handle);
+	tag = dnbd3_tag_from_handle(handle);
+
+	hwq = blk_mq_unique_tag_to_hwq(tag);
+	if (hwq < dev->tag_set.nr_hw_queues) {
+		req = blk_mq_tag_to_rq(dev->tag_set.tags[hwq],
+				blk_mq_unique_tag_to_tag(tag));
+	}
+	if (!req || !blk_mq_request_started(req)) {
+		error_sock(sock, "unexpected reply (%d) %p", tag, req);
+		if (req) {
+			debug_sock(sock, "requeue request");
+			dnbd3_requeue_cmd(blk_mq_rq_to_pdu(req));
+		}
+		dnbd3_clear_socket(sock, reply, remaining);
+		return -EIO;
+	}
+	cmd = blk_mq_rq_to_pdu(req);
+
+	mutex_lock(&cmd->lock);
+	if (cmd->cookie != cookie) {
+		error_sock(sock, "double reply on req %p, cookie %u, handle cookie %u",
+				req, cmd->cookie, cookie);
+		mutex_unlock(&cmd->lock);
+		dnbd3_clear_socket(sock, reply, remaining);
+		return -EIO;
+	}
+
+	rq_for_each_segment(bvec_inst, req, iter) {
+		siginitsetinv(&blocked, sigmask(SIGKILL));
+		sigprocmask(SIG_SETMASK, &blocked, &oldset);
+
+		kaddr = kmap(bvec->bv_page) + bvec->bv_offset;
+		iov.iov_base = kaddr;
+		iov.iov_len = bvec->bv_len;
+		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, bvec->bv_len,
+				msg.msg_flags);
+		remaining -= result;
+		if (result != bvec->bv_len) {
+			kunmap(bvec->bv_page);
+			sigprocmask(SIG_SETMASK, &oldset, NULL );
+			error_sock(sock, "could not receive from net to block layer");
+			dnbd3_requeue_cmd(cmd);
+			mutex_unlock(&cmd->lock);
+			if (result >= 0) {
+				dnbd3_clear_socket(sock, reply, remaining);
+				return -EIO;
+			} else {
+				return result;
+			}
+		}
+		kunmap(bvec->bv_page);
+
+		sigprocmask(SIG_SETMASK, &oldset, NULL );
+	}
+	mutex_unlock(&cmd->lock);
+	dnbd3_end_cmd(cmd, 0);
+	return result;
+}
+
+
+
+/**
+ * dnbd3_receive_cmd_get_block_test - receive a test block
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * the received data is just thrown away
+ */
+int dnbd3_receive_cmd_get_block_test(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply)
+{
+	struct msghdr msg;
+	struct kvec iov;
+	int result = 0;
+	char *buf = kmalloc(reply->size, GFP_KERNEL);
+	if (!buf) {
+		error_sock(sock, "kmalloc failed");
+		goto error;
+	}
+
+	dnbd3_init_msghdr(msg);
+	iov.iov_base = buf;
+	iov.iov_len = reply->size;
+	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, reply->size,
+			msg.msg_flags);
+	if (result != RTT_BLOCK_SIZE) {
+		error_sock(sock, "receive test block failed");
+		goto error;
+	}
+
+error:
+	if (buf) {
+		kfree(buf);
+	}
+	return result;
+}
+
+/**
+ * dnbd3_receive_cmd_get_servers - receive new servers
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * the new servers are copied to dnbd3_device.new_servers and
+ * dnbd3_device.new_server_num is set accordingly
+ */
+int dnbd3_receive_cmd_get_servers(struct dnbd3_sock *sock, dnbd3_reply_t *reply)
+{
+	struct msghdr msg;
+	struct kvec iov;
+	struct dnbd3_device *dev = sock->device;
+	int result = 1;
+	int count, remaining;
+	dnbd3_init_msghdr(msg);
+
+	debug_sock(sock, "get servers received");
+	mutex_lock(&dev->device_lock);
+	if (!dev->use_server_provided_alts) {
+		remaining = reply->size;
+		goto consume_payload;
+	}
+	dev->new_servers_num = 0;
+	count = MIN(NUMBER_SERVERS, reply->size / sizeof(dnbd3_server_entry_t));
+
+	if (count != 0) {
+		iov.iov_base = dev->new_servers;
+		iov.iov_len = count * sizeof(dnbd3_server_entry_t);
+		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
+				msg.msg_flags);
+		if (result <= 0) {
+			error_sock(sock, "failed to receive get servers %d",
+					result);
+			mutex_unlock(&dev->device_lock);
+			return result;
+		} else if (result != (count * sizeof(dnbd3_server_entry_t))) {
+			error_sock(sock, "failed to get servers");
+			mutex_unlock(&dev->device_lock);
+			return -EIO;
+		}
+		dev->new_servers_num = count;
+	}
+	/*
+	 * if there were more servers than accepted, remove the remaining data
+	 * from the socket buffer
+	 * abuse the reply struct as the receive buffer
+	 */
+	remaining = reply->size - (count * sizeof(dnbd3_server_entry_t));
+consume_payload:
+	while (remaining > 0) {
+		count = MIN(sizeof(dnbd3_reply_t), remaining);
+		iov.iov_base = reply;
+		iov.iov_len = count;
+		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, count,
+				msg.msg_flags);
+		if (result <= 0) {
+			error_sock(sock, "failed to receive payload from get servers");
+			mutex_unlock(&dev->device_lock);
+			return result;
+		}
+		remaining -= result;
+	}
+	mutex_unlock(&dev->device_lock);
+	return result;
+}
+
+/**
+ * dnbd3_receive_cmd_latest_rid - receive latest rid
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * dnbd3_device.update_available is set if a new RID is received
+ */
+int dnbd3_receive_cmd_latest_rid(struct dnbd3_sock *sock, dnbd3_reply_t *reply)
+{
+	struct kvec iov;
+	uint16_t rid;
+	int result;
+	struct msghdr msg;
+	struct dnbd3_device *dev = sock->device;
+	dnbd3_init_msghdr(msg);
+	debug_sock(sock, "latest rid received");
+
+	if (reply->size != 2) {
+		error_sock(sock, "failed to get latest rid, wrong size");
+		return -EIO;
+	}
+	iov.iov_base = &rid;
+	iov.iov_len = sizeof(rid);
+	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
+			msg.msg_flags);
+	if (result <= 0) {
+		error_sock(sock, "failed to receive latest rid");
+		return result;
+	}
+	rid = net_order_16(rid);
+	debug_sock(sock, "latest rid of %s is %d (currently using %d)",
+			dev->imgname, (int)rid, (int)dev->rid);
+	dev->update_available = (rid > dev->rid ? true : false);
+	return result;
+}
+
+
+/**
+ * dnbd3_receive_cmd_latest_rid - select the image
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * if this is the first connection the image name, file size and rid will be set
+ * if this is a further connection image name, file size and rid will be checked
+ */
+int dnbd3_receive_cmd_select_image(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply)
+{
+	struct kvec iov;
+	uint16_t rid;
+	char *name;
+	int result;
+	struct msghdr msg;
+	serialized_buffer_t payload_buffer;
+	uint64_t reported_size;
+	struct dnbd3_device *dev = sock->device;
+	dnbd3_init_msghdr(msg);
+	debug_sock(sock, "select image received");
+	iov.iov_base = &payload_buffer;
+	iov.iov_len = reply->size;
+	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
+			msg.msg_flags);
+	if (result <= 0) {
+		error_sock(sock, "failed to receive select image %d", result);
+		return result;
+	} else if (result != reply->size) {
+		error_sock(sock, "could not read CMD_SELECT_IMAGE payload on handshake, size is %d and should be %d",
+				result, reply->size);
+		return -EIO;
+	}
+
+	/* handle/check reply payload */
+	serializer_reset_read(&payload_buffer, reply->size);
+	sock->server->protocol_version = serializer_get_uint16(&payload_buffer);
+	if (sock->server->protocol_version < MIN_SUPPORTED_SERVER) {
+		error_sock(sock, "server version is lower than min supported version");
+		return -EIO;
+	}
+
+	//TODO compare RID
+
+	name = serializer_get_string(&payload_buffer);
+	rid = serializer_get_uint16(&payload_buffer);
+	if (dev->rid != rid && strcmp(name, dev->imgname) != 0) {
+		error_sock(sock, "server offers image '%s', requested '%s'",
+				name, dev->imgname);
+		return -EIO;
+	}
+
+	reported_size = serializer_get_uint64(&payload_buffer);
+	if (!dev->reported_size) {
+		if (reported_size < 4096) {
+			error_sock(sock, "reported size by server is < 4096");
+			return -EIO;
+		}
+		dev->reported_size = reported_size;
+		set_capacity(dev->disk, dev->reported_size >> 9); /* 512 Byte */
+	} else if (dev->reported_size != reported_size) {
+		error_sock(sock, "reported size by server is %llu but should be %llu",
+				reported_size, dev->reported_size);
+		return -EIO;
+	}
+	return result;
+
+}
+
+
+
+
diff --git a/src/kernel/net-txrx.h b/src/kernel/net-txrx.h
new file mode 100644
index 0000000..3636ffe
--- /dev/null
+++ b/src/kernel/net-txrx.h
@@ -0,0 +1,116 @@
+/*
+ * This file is part of the Distributed Network Block Device 3
+ *
+ * Copyright(c) 2019 Frederic Robra <frederic@robra.org>
+ * Parts copyright 2011-2012 Johann Latocha <johann@latocha.de>
+ *
+ * This file may be licensed under the terms of of the
+ * GNU General Public License Version 2 (the ``GPL'').
+ *
+ * Software distributed under the License is distributed
+ * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
+ * express or implied. See the GPL for the specific language
+ * governing rights and limitations.
+ *
+ * You should have received a copy of the GPL along with this
+ * program. If not, go to http://www.gnu.org/licenses/gpl.html
+ * or write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+
+#ifndef NET_TXRX_H_
+#define NET_TXRX_H_
+
+
+
+#include "dnbd3.h"
+
+#define dnbd3_is_sock_alive(s) ((s).sock && (s).server)
+
+int dnbd3_send_request(struct dnbd3_sock *sock, struct request *req, struct dnbd3_cmd *cmd);
+
+/**
+ * dnbd3_send_request_cmd - send a dndb3 cmd
+ * @sock: the socket where the request is send
+ * @dnbd3_cmd: the dnbd3 cmd to send
+ */
+int dnbd3_send_request_cmd(struct dnbd3_sock *sock, uint16_t dnbd3_cmd);
+
+
+/**
+ * dnbd3_receive_cmd - receive a command
+ * @sock: the socket where the request is received
+ * @reply: an unused reply will be filled with the reply of the server
+ *
+ * this method should be called directly after the dnbd3_send_request_ method
+ */
+int dnbd3_receive_cmd(struct dnbd3_sock *sock, dnbd3_reply_t *reply);
+
+
+/**
+ * dnbd3_receive_cmd_get_block_mq - receive a block for mq
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * this method copies the data to user space according to the request which is
+ * encoded in the handle by the send request method and decoded here.
+ */
+int dnbd3_receive_cmd_get_block_mq(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply);
+
+
+/**
+ * dnbd3_receive_cmd_get_block_test - receive a test block
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * the received data is just thrown away
+ */
+int dnbd3_receive_cmd_get_block_test(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply);
+
+
+/**
+ * dnbd3_receive_cmd_get_servers - receive new servers
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * the new servers are copied to dnbd3_device.new_servers and
+ * dnbd3_device.new_server_num is set accordingly
+ */
+int dnbd3_receive_cmd_get_servers(struct dnbd3_sock *sock, dnbd3_reply_t *reply);
+
+
+/**
+ * dnbd3_receive_cmd_latest_rid - receive latest rid
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * dnbd3_device.update_available is set if a new RID is received
+ */
+int dnbd3_receive_cmd_latest_rid(struct dnbd3_sock *sock, dnbd3_reply_t *reply);
+
+/**
+ * dnbd3_receive_cmd_latest_rid - select the image
+ * @sock: the socket where the request is received
+ * @reply: the reply initialized by dnbd3_receive_cmd
+ *
+ * this method should be called directly after the dnbd3_receive_cmd method
+ *
+ * if this is the first connection the image name, file size and rid will be set
+ * if this is a further connection image name, file size and rid will be checked
+ */
+int dnbd3_receive_cmd_select_image(struct dnbd3_sock *sock,
+		dnbd3_reply_t *reply);
+
+#endif /* KERNEL_NET_TXRX_H_ */
diff --git a/src/kernel/net.c b/src/kernel/net.c
index 1207d0a..cb4e76c 100644
--- a/src/kernel/net.c
+++ b/src/kernel/net.c
@@ -25,613 +25,26 @@
 #include <linux/sort.h>
 
 #include "net.h"
+#include "net-txrx.h"
 #include "utils.h"
 #include "clientconfig.h"
 #include "mq.h"
 
 
-#define DNBD3_REQ_OP_SPECIAL REQ_OP_DRV_IN
-#define DNBD3_REQ_OP_CONNECT REQ_OP_DRV_OUT
-
-#define dnbd3_cmd_to_op_special(req, cmd) \
-	(req)->cmd_flags = DNBD3_REQ_OP_SPECIAL | ((cmd) << REQ_FLAG_BITS)
-
-#define dnbd3_op_special_to_cmd(req) \
-	((req)->cmd_flags >> REQ_FLAG_BITS)
-
-#define dnbd3_connect_to_req(req) \
-	(req)->cmd_flags = DNBD3_REQ_OP_CONNECT \
-			| ((CMD_SELECT_IMAGE) << REQ_FLAG_BITS)
-
-#define dnbd3_test_block_to_req(req) \
-	do { \
-		(req)->cmd_flags = REQ_OP_READ; \
-		(req)->__data_len = RTT_BLOCK_SIZE; \
-		(req)->__sector = 0; \
-	} while (0)
-
 #define dnbd3_sock_create(af,type,proto,sock) \
 	sock_create_kern(&init_net, (af) == HOST_IP4 ? AF_INET : AF_INET6, \
 			type, proto, sock)
 
-#define REQUEST_TIMEOUT \
-	(HZ * SOCKET_TIMEOUT_CLIENT_DATA)
+#define dnbd3_is_sock_alive(s) ((s).sock && (s).server)
 
 
-#define dnbd3_init_msghdr(h) \
-	do { \
-		(h).msg_name = NULL; \
-		(h).msg_namelen = 0; \
-		(h).msg_control = NULL; \
-		(h).msg_controllen = 0; \
-		(h).msg_flags = MSG_WAITALL | MSG_NOSIGNAL; \
-	} while (0)
 
 static int __dnbd3_socket_connect(struct dnbd3_sock *sock,
-		struct dnbd3_server * server);
+		struct dnbd3_server *server);
 static int dnbd3_socket_connect(struct dnbd3_sock *sock,
-		struct dnbd3_server * server);
+		struct dnbd3_server *server);
 static int dnbd3_socket_disconnect(struct dnbd3_sock *sock);
 
-static uint64_t dnbd3_average_rtt(struct dnbd3_server *server)
-{
-	int i, j = 0;
-	uint64_t avg = 0;
-	for (i = 0; i < 4; i++) {
-		avg += server->rtts[i];
-		j += server->rtts[i] == 0 ? 0 : 1;
-	}
-	if (avg == 0) {
-		return RTT_UNKNOWN;
-	} else {
-		avg = avg / j;
-		avg += server->failures * avg / 10;
-		return avg;
-	}
-}
-
-/*
- * Methods for request and receive commands
- */
-
-
-/**
- * dnbd3_to_handle - convert tag and cookie to handle
- * @tag: the tag to convert
- * @cookie: the cookie to convert
- */
-static inline uint64_t dnbd3_to_handle(uint32_t tag, uint32_t cookie) {
-	return ((uint64_t) tag << 32) | cookie;
-}
-
-/**
- * dnbd3_tag_from_handle - get tag from handle
- * @handle: the handle
- */
-static inline uint32_t dnbd3_tag_from_handle(uint64_t handle) {
-	return (uint32_t)(handle >> 32);
-}
-
-/**
- * dnbd3_cookie_from_handle - get cookie from handle
- * @handle: the handle
- */
-static inline uint32_t dnbd3_cookie_from_handle(uint64_t handle) {
-	return (uint32_t) handle;
-}
-
-/**
- * dnbd3_send_request - send a request
- * @sock: the socket where the request is send
- * @req: the request to send
- * @cmd: optional - the dnbd3_cmd from mq
- *
- * the tx_lock of the socket must be held
- */
-int dnbd3_send_request(struct dnbd3_sock *sock, struct request *req,
-		struct dnbd3_cmd *cmd)
-{
-	dnbd3_request_t request;
-	struct msghdr msg;
-	struct kvec iov[2];
-	size_t iov_num = 1;
-	size_t lng;
-	int result;
-	uint32_t tag;
-	uint64_t handle;
-	serialized_buffer_t payload_buffer;
-	sock->pending = req;
-	dnbd3_init_msghdr(msg);
-
-	request.magic = dnbd3_packet_magic;
-
-	switch (req_op(req)) {
-	case REQ_OP_READ:
-		debug_sock(sock, "request operation read");
-		request.cmd = CMD_GET_BLOCK;
-		request.offset = blk_rq_pos(req) << 9; // * 512
-		request.size = blk_rq_bytes(req);
-		break;
-	case DNBD3_REQ_OP_SPECIAL:
-		debug_sock(sock, "request operation special");
-		request.cmd = dnbd3_op_special_to_cmd(req);
-		request.size = 0;
-		break;
-	case DNBD3_REQ_OP_CONNECT:
-		debug_sock(sock, "request operation connect to %s",
-				sock->device->imgname);
-		request.cmd = CMD_SELECT_IMAGE;
-		serializer_reset_write(&payload_buffer);
-		serializer_put_uint16(&payload_buffer, PROTOCOL_VERSION);
-		serializer_put_string(&payload_buffer, sock->device->imgname);
-		serializer_put_uint16(&payload_buffer, sock->device->rid);
-		serializer_put_uint8(&payload_buffer, 0); // is_server = false
-		iov[1].iov_base = &payload_buffer;
-		request.size = serializer_get_written_length(&payload_buffer);
-		iov[1].iov_len = request.size;
-		iov_num = 2;
-		break;
-	default:
-		return -EIO;
-	}
-	sock->cookie++;
-	if (cmd != NULL) {
-		cmd->cookie = sock->cookie;
-		tag = blk_mq_unique_tag(req);
-		handle = dnbd3_to_handle(tag, sock->cookie);
-	} else {
-		handle = sock->cookie;
-	}
-	memcpy(&request.handle, &handle, sizeof(handle));
-
-	fixup_request(request);
-	iov[0].iov_base = &request;
-	iov[0].iov_len = sizeof(request);
-	lng = iov_num == 1 ? iov[0].iov_len : iov[0].iov_len + iov[1].iov_len;
-	result = kernel_sendmsg(sock->sock, &msg, iov, iov_num, lng);
-	if (result != lng) {
-		error_sock(sock, "connection to server lost");
-		if (cmd) {
-			dnbd3_requeue_cmd(cmd);
-		}
-		sock->panic = true;
-		sock->server->failures++;
-		goto error;
-	}
-
-error:
-	sock->pending = NULL;
-	return result;
-}
-
-
-/**
- * dnbd3_send_request_cmd - send a dndb3 cmd
- * @sock: the socket where the request is send
- * @dnbd3_cmd: the dnbd3 cmd to send
- */
-static int dnbd3_send_request_cmd(struct dnbd3_sock *sock, uint16_t dnbd3_cmd)
-{
-	int result;
-	struct request *req = kmalloc(sizeof(struct request), GFP_KERNEL);
-	if (!req) {
-		error_sock(sock, "kmalloc failed");
-		result = -EIO;
-		goto error;
-	}
-
-	switch (dnbd3_cmd) {
-	case CMD_KEEPALIVE:
-	case CMD_GET_SERVERS:
-		dnbd3_cmd_to_op_special(req, dnbd3_cmd);
-		break;
-	case CMD_SELECT_IMAGE:
-		dnbd3_connect_to_req(req);
-		break;
-	case CMD_GET_BLOCK:
-		dnbd3_test_block_to_req(req);
-		break;
-	default:
-		warn_sock(sock, "unsupported command %d", dnbd3_cmd);
-		result = -EINVAL;
-		goto error;
-	}
-
-	mutex_lock(&sock->tx_lock);
-	sock->pending = req;
-	result = dnbd3_send_request(sock, req, NULL);
-	mutex_unlock(&sock->tx_lock);
-
-error:
-	if (req) {
-		kfree(req);
-	}
-	return result;
-}
-
-/**
- * dnbd3_receive_cmd - receive a command
- * @sock: the socket where the request is received
- * @reply: an unused reply will be filled with the reply of the server
- *
- * this method should be called directly after the dnbd3_send_request_ method
- */
-static int dnbd3_receive_cmd(struct dnbd3_sock *sock, dnbd3_reply_t *reply)
-{
-	int result;
-	struct msghdr msg;
-	struct kvec iov;
-	dnbd3_init_msghdr(msg);
-	iov.iov_base = reply;
-	iov.iov_len = sizeof(dnbd3_reply_t);
-	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
-			msg.msg_flags);
-	if (result <= 0) {
-		return result;
-	}
-	fixup_reply(dnbd3_reply);
-
-	if (reply->magic != dnbd3_packet_magic) {
-		error_sock(sock, "receive cmd wrong magic packet");
-		return -EIO;
-	}
-
-	if (reply->cmd == 0) {
-		error_sock(sock, "receive command was 0");
-		return -EIO;
-	}
-	return result;
-}
-
-static int dnbd3_clear_socket(struct dnbd3_sock *sock, dnbd3_reply_t *reply,
-		int remaining)
-{
-	int result = 0;
-	char *buf;
-	struct kvec iov;
-	struct msghdr msg;
-	dnbd3_init_msghdr(msg);
-	warn_sock(sock, "clearing socket %d bytes", remaining);
-	buf = kmalloc(RTT_BLOCK_SIZE, GFP_KERNEL);
-	if (!buf) {
-		error_sock(sock, "kmalloc failed");
-		return -EIO;
-	}
-	/* hold the tx_lock so no new requests are send */
-	mutex_lock(&sock->tx_lock);
-	iov.iov_base = buf;
-	iov.iov_len = RTT_BLOCK_SIZE;
-	while (remaining > 0) {
-		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
-				msg.msg_flags);
-		if (result <= 0) {
-			goto error;
-		}
-		remaining -= result;
-	}
-
-	debug_sock(sock, "cleared socket");
-error:
-	mutex_unlock(&sock->tx_lock);
-	if (buf) {
-		kfree(buf);
-	}
-	return result;
-}
-
-/**
- * dnbd3_receive_cmd_get_block_mq - receive a block for mq
- * @sock: the socket where the request is received
- * @reply: the reply initialized by dnbd3_receive_cmd
- *
- * this method should be called directly after the dnbd3_receive_cmd method
- *
- * this method copies the data to user space according to the request which is
- * encoded in the handle by the send request method and decoded here.
- */
-static int dnbd3_receive_cmd_get_block_mq(struct dnbd3_sock *sock,
-		dnbd3_reply_t *reply)
-{
-	struct dnbd3_cmd *cmd;
-	struct msghdr msg;
-	struct request *req = NULL;
-	struct kvec iov;
-	struct req_iterator iter;
-	struct bio_vec bvec_inst;
-	struct dnbd3_device *dev = sock->device;
-	struct bio_vec *bvec = &bvec_inst;
-	sigset_t blocked, oldset;
-	void *kaddr;
-	uint32_t tag, cookie;
-	uint16_t hwq;
-	uint32_t remaining = reply->size;
-	int result = 0;
-	uint64_t handle;
-	dnbd3_init_msghdr(msg);
-
-	memcpy(&handle, &reply->handle, sizeof(handle));
-	cookie = dnbd3_cookie_from_handle(handle);
-	tag = dnbd3_tag_from_handle(handle);
-
-	hwq = blk_mq_unique_tag_to_hwq(tag);
-	if (hwq < dev->tag_set.nr_hw_queues) {
-		req = blk_mq_tag_to_rq(dev->tag_set.tags[hwq],
-				blk_mq_unique_tag_to_tag(tag));
-	}
-	if (!req || !blk_mq_request_started(req)) {
-		error_sock(sock, "unexpected reply (%d) %p", tag, req);
-		if (req) {
-			debug_sock(sock, "requeue request");
-			dnbd3_requeue_cmd(blk_mq_rq_to_pdu(req));
-		}
-		dnbd3_clear_socket(sock, reply, remaining);
-		return -EIO;
-	}
-	cmd = blk_mq_rq_to_pdu(req);
-
-	mutex_lock(&cmd->lock);
-	if (cmd->cookie != cookie) {
-		error_sock(sock, "double reply on req %p, cookie %u, handle cookie %u",
-				req, cmd->cookie, cookie);
-		mutex_unlock(&cmd->lock);
-		dnbd3_clear_socket(sock, reply, remaining);
-		return -EIO;
-	}
-
-	rq_for_each_segment(bvec_inst, req, iter) {
-		siginitsetinv(&blocked, sigmask(SIGKILL));
-		sigprocmask(SIG_SETMASK, &blocked, &oldset);
-
-		kaddr = kmap(bvec->bv_page) + bvec->bv_offset;
-		iov.iov_base = kaddr;
-		iov.iov_len = bvec->bv_len;
-		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, bvec->bv_len,
-				msg.msg_flags);
-		remaining -= result;
-		if (result != bvec->bv_len) {
-			kunmap(bvec->bv_page);
-			sigprocmask(SIG_SETMASK, &oldset, NULL );
-			error_sock(sock, "could not receive from net to block layer");
-			dnbd3_requeue_cmd(cmd);
-			mutex_unlock(&cmd->lock);
-			if (result >= 0) {
-				dnbd3_clear_socket(sock, reply, remaining);
-				return -EIO;
-			} else {
-				return result;
-			}
-		}
-		kunmap(bvec->bv_page);
-
-		sigprocmask(SIG_SETMASK, &oldset, NULL );
-	}
-	mutex_unlock(&cmd->lock);
-	dnbd3_end_cmd(cmd, 0);
-	return result;
-}
-
-
-
-/**
- * dnbd3_receive_cmd_get_block_test - receive a test block
- * @sock: the socket where the request is received
- * @reply: the reply initialized by dnbd3_receive_cmd
- *
- * this method should be called directly after the dnbd3_receive_cmd method
- *
- * the received data is just thrown away
- */
-static int dnbd3_receive_cmd_get_block_test(struct dnbd3_sock *sock,
-		dnbd3_reply_t *reply)
-{
-	struct msghdr msg;
-	struct kvec iov;
-	int result = 0;
-	char *buf = kmalloc(reply->size, GFP_KERNEL);
-	if (!buf) {
-		error_sock(sock, "kmalloc failed");
-		goto error;
-	}
-
-	dnbd3_init_msghdr(msg);
-	iov.iov_base = buf;
-	iov.iov_len = reply->size;
-	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, reply->size,
-			msg.msg_flags);
-	if (result != RTT_BLOCK_SIZE) {
-		error_sock(sock, "receive test block failed");
-		goto error;
-	}
-
-error:
-	if (buf) {
-		kfree(buf);
-	}
-	return result;
-}
-
-/**
- * dnbd3_receive_cmd_get_servers - receive new servers
- * @sock: the socket where the request is received
- * @reply: the reply initialized by dnbd3_receive_cmd
- *
- * this method should be called directly after the dnbd3_receive_cmd method
- *
- * the new servers are copied to dnbd3_device.new_servers and
- * dnbd3_device.new_server_num is set accordingly
- */
-static int dnbd3_receive_cmd_get_servers(struct dnbd3_sock *sock,
-		dnbd3_reply_t *reply)
-{
-	struct msghdr msg;
-	struct kvec iov;
-	struct dnbd3_device *dev = sock->device;
-	int result = 1;
-	int count, remaining;
-	dnbd3_init_msghdr(msg);
-
-	debug_sock(sock, "get servers received");
-	mutex_lock(&dev->device_lock);
-	if (!dev->use_server_provided_alts) {
-		remaining = reply->size;
-		goto consume_payload;
-	}
-	dev->new_servers_num = 0;
-	count = MIN(NUMBER_SERVERS, reply->size / sizeof(dnbd3_server_entry_t));
-
-	if (count != 0) {
-		iov.iov_base = dev->new_servers;
-		iov.iov_len = count * sizeof(dnbd3_server_entry_t);
-		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
-				msg.msg_flags);
-		if (result <= 0) {
-			error_sock(sock, "failed to receive get servers %d",
-					result);
-			mutex_unlock(&dev->device_lock);
-			return result;
-		} else if (result != (count * sizeof(dnbd3_server_entry_t))) {
-			error_sock(sock, "failed to get servers");
-			mutex_unlock(&dev->device_lock);
-			return -EIO;
-		}
-		dev->new_servers_num = count;
-	}
-	/*
-	 * if there were more servers than accepted, remove the remaining data
-	 * from the socket buffer
-	 * abuse the reply struct as the receive buffer
-	 */
-	remaining = reply->size - (count * sizeof(dnbd3_server_entry_t));
-consume_payload:
-	while (remaining > 0) {
-		count = MIN(sizeof(dnbd3_reply_t), remaining);
-		iov.iov_base = reply;
-		iov.iov_len = count;
-		result = kernel_recvmsg(sock->sock, &msg, &iov, 1, count,
-				msg.msg_flags);
-		if (result <= 0) {
-			error_sock(sock, "failed to receive payload from get servers");
-			mutex_unlock(&dev->device_lock);
-			return result;
-		}
-		remaining -= result;
-	}
-	mutex_unlock(&dev->device_lock);
-	return result;
-}
-
-/**
- * dnbd3_receive_cmd_latest_rid - receive latest rid
- * @sock: the socket where the request is received
- * @reply: the reply initialized by dnbd3_receive_cmd
- *
- * this method should be called directly after the dnbd3_receive_cmd method
- *
- * dnbd3_device.update_available is set if a new RID is received
- */
-static int dnbd3_receive_cmd_latest_rid(struct dnbd3_sock *sock,
-		dnbd3_reply_t *reply)
-{
-	struct kvec iov;
-	uint16_t rid;
-	int result;
-	struct msghdr msg;
-	struct dnbd3_device *dev = sock->device;
-	dnbd3_init_msghdr(msg);
-	debug_sock(sock, "latest rid received");
-
-	if (reply->size != 2) {
-		error_sock(sock, "failed to get latest rid, wrong size");
-		return -EIO;
-	}
-	iov.iov_base = &rid;
-	iov.iov_len = sizeof(rid);
-	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
-			msg.msg_flags);
-	if (result <= 0) {
-		error_sock(sock, "failed to receive latest rid");
-		return result;
-	}
-	rid = net_order_16(rid);
-	debug_sock(sock, "latest rid of %s is %d (currently using %d)",
-			dev->imgname, (int)rid, (int)dev->rid);
-	dev->update_available = (rid > dev->rid ? true : false);
-	return result;
-}
-
-
-/**
- * dnbd3_receive_cmd_latest_rid - select the image
- * @sock: the socket where the request is received
- * @reply: the reply initialized by dnbd3_receive_cmd
- *
- * this method should be called directly after the dnbd3_receive_cmd method
- *
- * if this is the first connection the image name, file size and rid will be set
- * if this is a further connection image name, file size and rid will be checked
- */
-static int dnbd3_receive_cmd_select_image(struct dnbd3_sock *sock,
-		dnbd3_reply_t *reply)
-{
-	struct kvec iov;
-	uint16_t rid;
-	char *name;
-	int result;
-	struct msghdr msg;
-	serialized_buffer_t payload_buffer;
-	uint64_t reported_size;
-	struct dnbd3_device *dev = sock->device;
-	dnbd3_init_msghdr(msg);
-	debug_sock(sock, "select image received");
-	iov.iov_base = &payload_buffer;
-	iov.iov_len = reply->size;
-	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, iov.iov_len,
-			msg.msg_flags);
-	if (result <= 0) {
-		error_sock(sock, "failed to receive select image %d", result);
-		return result;
-	} else if (result != reply->size) {
-		error_sock(sock, "could not read CMD_SELECT_IMAGE payload on handshake, size is %d and should be %d",
-				result, reply->size);
-		return -EIO;
-	}
-
-	/* handle/check reply payload */
-	serializer_reset_read(&payload_buffer, reply->size);
-	sock->server->protocol_version = serializer_get_uint16(&payload_buffer);
-	if (sock->server->protocol_version < MIN_SUPPORTED_SERVER) {
-		error_sock(sock, "server version is lower than min supported version");
-		return -EIO;
-	}
-
-	//TODO compare RID
-
-	name = serializer_get_string(&payload_buffer);
-	rid = serializer_get_uint16(&payload_buffer);
-	if (dev->rid != rid && strcmp(name, dev->imgname) != 0) {
-		error_sock(sock, "server offers image '%s', requested '%s'",
-				name, dev->imgname);
-		return -EIO;
-	}
-
-	reported_size = serializer_get_uint64(&payload_buffer);
-	if (!dev->reported_size) {
-		if (reported_size < 4096) {
-			error_sock(sock, "reported size by server is < 4096");
-			return -EIO;
-		}
-		dev->reported_size = reported_size;
-		set_capacity(dev->disk, dev->reported_size >> 9); /* 512 Byte */
-	} else if (dev->reported_size != reported_size) {
-		error_sock(sock, "reported size by server is %llu but should be %llu",
-				reported_size, dev->reported_size);
-		return -EIO;
-	}
-	return result;
-
-}
-
-
 /*
  * Timer and workers
  */
@@ -838,7 +251,7 @@ static int dnbd3_panic_connect(struct dnbd3_device *dev)
 		}
 	}
 	if (working == NULL) {
-		return -EIO;
+		return -ENOENT;
 	}
 	for (i = 0; i < NUMBER_CONNECTIONS; i++) {
 		if (dev->socks[i].server != working) {
@@ -925,7 +338,8 @@ static void dnbd3_panic_worker(struct work_struct *work)
 	int sock_alive = 0;
 	dev = container_of(work, struct dnbd3_device, panic_worker);
 	for (i = 0; i < NUMBER_CONNECTIONS; i++) {
-		if (dev->socks[i].panic) {
+		if (dev->socks[i].panic
+				|| dev->socks[i].server->failures > 1000) {
 			panic = true;
 			dnbd3_set_rtt_unreachable(dev->socks[i].server);
 			dnbd3_socket_disconnect(&dev->socks[i]);
@@ -962,7 +376,6 @@ static int dnbd3_meassure_rtt(struct dnbd3_device *dev,
 {
 	struct timeval start, end;
 	dnbd3_reply_t reply;
-	struct request req;
 	int result;
 	uint64_t rtt = RTT_UNREACHABLE;
 	struct dnbd3_sock sock = {
@@ -977,7 +390,6 @@ static int dnbd3_meassure_rtt(struct dnbd3_device *dev,
 		error_sock(&sock, "socket connect failed in rtt measurement");
 		goto error;
 	}
-	dnbd3_connect_to_req(&req);
 	result = dnbd3_send_request_cmd(&sock, CMD_SELECT_IMAGE);
 	if (result <= 0) {
 		error_sock(&sock, "request select image failed in rtt measurement");
@@ -1138,8 +550,10 @@ static void dnbd3_discovery_worker(struct work_struct *work)
 	for (i = 0; i < NUMBER_SERVERS; i++) {
 		server = &dev->alt_servers[i];
 		if (server->host.type) {
+			/* failure count is divided*/
+			server->failures = server->failures / 2;
 			if (dnbd3_meassure_rtt(dev, server) <= 0) {
-				server->failures++;
+				server->failures = server->failures * 2;
 				warn_server(dev, server,
 						"failed to meassure rtt");
 			}
@@ -1316,8 +730,6 @@ static int dnbd3_socket_connect(struct dnbd3_sock *sock,
 	if (dnbd3_send_request_cmd(sock, CMD_GET_SERVERS) <= 0) {
 		error_sock(sock, "failed to get servers in discovery");
 	}
-	/* failure count is divided on each successful connect */
-	server->failures = server->failures / 2;
 
 	return 0;
 error:
diff --git a/src/kernel/net.h b/src/kernel/net.h
index 7efe859..b8df66e 100644
--- a/src/kernel/net.h
+++ b/src/kernel/net.h
@@ -25,10 +25,6 @@
 
 #include "dnbd3.h"
 
-#define dnbd3_is_sock_alive(s) ((s).sock && (s).server)
-
-int dnbd3_send_request(struct dnbd3_sock *sock, struct request *req, struct dnbd3_cmd *cmd);
-
 
 int dnbd3_net_connect(struct dnbd3_device *dev);
 int dnbd3_net_disconnect(struct dnbd3_device *dev);
diff --git a/src/kernel/utils.c b/src/kernel/utils.c
index 957d69b..164d51a 100644
--- a/src/kernel/utils.c
+++ b/src/kernel/utils.c
@@ -2,6 +2,7 @@
  * This file is part of the Distributed Network Block Device 3
  *
  * Copyright(c) 2011-2012 Johann Latocha <johann@latocha.de>
+ * Copyright(c) 2019 Frederic Robra <frederic@robra.org>
  *
  * This file may be licensed under the terms of of the
  * GNU General Public License Version 2 (the ``GPL'').
@@ -19,6 +20,7 @@
  */
 
 #include "utils.h"
+#include "clientconfig.h"
 
 #include <linux/kernel.h>
 
@@ -40,3 +42,20 @@ void inet_ntoa(struct in_addr addr, char *str)
 	unsigned char *ptr = (unsigned char *) &addr;
 	sprintf(str, "%d.%d.%d.%d", ptr[0] & 0xff, ptr[1] & 0xff, ptr[2] & 0xff, ptr[3] & 0xff);
 }
+
+uint64_t dnbd3_average_rtt(struct dnbd3_server *server)
+{
+	int i, j = 0;
+	uint64_t avg = 0;
+	for (i = 0; i < 4; i++) {
+		avg += server->rtts[i];
+		j += server->rtts[i] == 0 ? 0 : 1;
+	}
+	if (avg == 0) {
+		return RTT_UNKNOWN;
+	} else {
+		avg = avg / j;
+		avg += server->failures * avg / 10;
+		return avg;
+	}
+}
diff --git a/src/kernel/utils.h b/src/kernel/utils.h
index e54b3cf..d7eb87f 100644
--- a/src/kernel/utils.h
+++ b/src/kernel/utils.h
@@ -1,7 +1,8 @@
 /*
  * This file is part of the Distributed Network Block Device 3
- *
+
  * Copyright(c) 2011-2012 Johann Latocha <johann@latocha.de>
+ * Copyright(c) 2019 Frederic Robra <frederic@robra.org>
  *
  * This file may be licensed under the terms of of the
  * GNU General Public License Version 2 (the ``GPL'').
@@ -21,9 +22,18 @@
 #ifndef UTILS_H_
 #define UTILS_H_
 
+#include "dnbd3.h"
+
 #include <linux/in.h>
 
 unsigned int inet_addr(char *str);
+
 void inet_ntoa(struct in_addr addr, char *str);
 
+/**
+ * dnbd3_average_rtt - calculate the average rtt
+ * @server: the server to calculate the average rtt
+ */
+uint64_t dnbd3_average_rtt(struct dnbd3_server *server);
+
 #endif /* UTILS_H_ */