added first support for connection with more than one server

6 files changed, 245 insertions, 301 deletions

diff --git a/src/kernel/block.c b/src/kernel/block.c
index ade02f0..4295418 100644
--- a/src/kernel/block.c
+++ b/src/kernel/block.c
@@ -22,241 +22,211 @@ void dnbd3_blk_fail_all_requests(dnbd3_device_t *dev)
 }
 
 
-
-int dnbd3_net_connect(dnbd3_device_t *dev)
+int dnbd3_socket_connect(dnbd3_device_t *dev, dnbd3_sock *sock)
 {
+	int result = -EIO;
 	struct request *req1 = NULL;
 	struct timeval timeout;
-
-	printk(KERN_DEBUG "dnbd3: net connect device %i\n", dev->minor);
-
-	if (dev->disconnecting) {
-		printk(KERN_DEBUG "dnbd3: device still disconnecting\n");
-		while (dev->disconnecting)
+	struct dnbd3_server_t *server = sock->server;
+	dnbd3_request_t dnbd3_request;
+	dnbd3_reply_t dnbd3_reply;
+	struct msghdr msg;
+	struct kvec iov[2];
+	uint16_t rid;
+	uint64_t reported_size;
+	char *name;
+	int mlen;
+	serialized_buffer_t payload_buffer;
+
+	printk(KERN_DEBUG "dnbd3: socket connect device %i\n", dev->minor);
+
+	mutex_init(&sock->lock);
+	mutex_lock(&sock->lock);
+	if (sock->pending) {
+		printk(KERN_DEBUG "dnbd3: socket still in request\n");
+		while (sock->pending)
 			schedule();
 	}
-	if (dev->pending) {
-		printk(KERN_DEBUG "dnbd3: device still in request\n");
-		while (dev->disconnecting)
-			schedule();
+	if (server->host.port == 0 || server->host.type == 0) {
+		printk(KERN_ERR "dnbd3: host or port not set\n");
+		goto error;
+	}
+	if (sock->sock) {
+		printk(KERN_WARNING "dnbd3: socket already connected\n");
+		goto error;
 	}
 
 	timeout.tv_sec = SOCKET_TIMEOUT_CLIENT_DATA;
 	timeout.tv_usec = 0;
 
-	// do some checks before connecting
-
 	req1 = kmalloc(sizeof(*req1), GFP_ATOMIC );
 	if (!req1) {
 		printk(KERN_ERR "dnbd3: kmalloc failed\n");
 		goto error;
 	}
-	if (dev->cur_server.host.port == 0 || dev->cur_server.host.type == 0 || dev->imgname == NULL ) {
-		printk(KERN_ERR "dnbd3: host, port or image name not set\n");
-		goto error;
-	}
-	if (dev->sock) {
-		printk(KERN_WARNING "dnbd3: already connected\n");
-		goto error;
-	}
 
-	if (dev->cur_server.host.type != HOST_IP4 && dev->cur_server.host.type != HOST_IP6) {
-		printk(KERN_ERR "dnbd3: unknown address type %d\n", (int)dev->cur_server.host.type);
+	init_msghdr(msg);
+
+	if (dnbd3_sock_create(server->host.type, SOCK_STREAM, IPPROTO_TCP, &sock->sock) < 0) {
+		printk(KERN_ERR "dnbd3: could not create socket\n");
 		goto error;
 	}
 
-	if (dev->better_sock == NULL ) {
-		//  no established connection yet from discovery thread, start new one
-		dnbd3_request_t dnbd3_request;
-		dnbd3_reply_t dnbd3_reply;
-		struct msghdr msg;
-		struct kvec iov[2];
-		uint16_t rid;
-		char *name;
-		int mlen;
-		init_msghdr(msg);
-
-		if (dnbd3_sock_create(dev->cur_server.host.type, SOCK_STREAM, IPPROTO_TCP, &dev->sock) < 0) {
-			printk(KERN_ERR "dnbd3: could not create socket\n");
+	kernel_setsockopt(sock->sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout));
+	kernel_setsockopt(sock->sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));
+	sock->sock->sk->sk_allocation = GFP_NOIO;
+	if (server->host.type == HOST_IP4) {
+		struct sockaddr_in sin;
+		memset(&sin, 0, sizeof(sin));
+		sin.sin_family = AF_INET;
+		memcpy(&(sin.sin_addr), server->host.addr, 4);
+		sin.sin_port = server->host.port;
+		if (kernel_connect(sock->sock, (struct sockaddr *)&sin, sizeof(sin), 0) != 0) {
+			printk(KERN_ERR "dnbd3: connection to host failed (ipv4)\n");
 			goto error;
 		}
-
-		kernel_setsockopt(dev->sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout));
-		kernel_setsockopt(dev->sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));
-		dev->sock->sk->sk_allocation = GFP_NOIO;
-		if (dev->cur_server.host.type == HOST_IP4) {
-			struct sockaddr_in sin;
-			memset(&sin, 0, sizeof(sin));
-			sin.sin_family = AF_INET;
-			memcpy(&(sin.sin_addr), dev->cur_server.host.addr, 4);
-			sin.sin_port = dev->cur_server.host.port;
-			if (kernel_connect(dev->sock, (struct sockaddr *)&sin, sizeof(sin), 0) != 0) {
-				printk(KERN_ERR "dnbd3: connection to host failed (ipv4)\n");
-				goto error;
-			}
-		} else {
-			struct sockaddr_in6 sin;
-			memset(&sin, 0, sizeof(sin));
-			sin.sin6_family = AF_INET6;
-			memcpy(&(sin.sin6_addr), dev->cur_server.host.addr, 16);
-			sin.sin6_port = dev->cur_server.host.port;
-			if (kernel_connect(dev->sock, (struct sockaddr *)&sin, sizeof(sin), 0) != 0){
-				printk(KERN_ERR "dnbd3: connection to host failed (ipv6)\n");
-				goto error;
-			}
-		}
-		// Request filesize
-		dnbd3_request.magic = dnbd3_packet_magic;
-		dnbd3_request.cmd = CMD_SELECT_IMAGE;
-		iov[0].iov_base = &dnbd3_request;
-		iov[0].iov_len = sizeof(dnbd3_request);
-		serializer_reset_write(&dev->payload_buffer);
-		serializer_put_uint16(&dev->payload_buffer, PROTOCOL_VERSION);
-		serializer_put_string(&dev->payload_buffer, dev->imgname);
-		serializer_put_uint16(&dev->payload_buffer, dev->rid);
-		serializer_put_uint8(&dev->payload_buffer, 0); // is_server = false
-		iov[1].iov_base = &dev->payload_buffer;
-		dnbd3_request.size = iov[1].iov_len = serializer_get_written_length(&dev->payload_buffer);
-		fixup_request(dnbd3_request);
-		mlen = sizeof(dnbd3_request) + iov[1].iov_len;
-		if (kernel_sendmsg(dev->sock, &msg, iov, 2, mlen) != mlen) {
-			printk(KERN_ERR "dnbd3: could not send CMD_SIZE_REQUEST\n");
-			goto error;
-		}
-		// receive reply header
-		iov[0].iov_base = &dnbd3_reply;
-		iov[0].iov_len = sizeof(dnbd3_reply);
-		if (kernel_recvmsg(dev->sock, &msg, iov, 1, sizeof(dnbd3_reply), msg.msg_flags) != sizeof(dnbd3_reply)) {
-			printk(KERN_ERR "dnbd3: received corrupted reply header after CMD_SIZE_REQUEST\n");
-			goto error;
-		}
-
-		// check reply header
-		fixup_reply(dnbd3_reply);
-		if (dnbd3_reply.cmd != CMD_SELECT_IMAGE ||
-				dnbd3_reply.size < 3 ||
-				dnbd3_reply.size > MAX_PAYLOAD ||
-				dnbd3_reply.magic != dnbd3_packet_magic) {
-			printk(KERN_ERR "dnbd3: received invalid reply to CMD_SIZE_REQUEST image does not exist on server\n");
+	} else {
+		struct sockaddr_in6 sin;
+		memset(&sin, 0, sizeof(sin));
+		sin.sin6_family = AF_INET6;
+		memcpy(&(sin.sin6_addr), server->host.addr, 16);
+		sin.sin6_port = server->host.port;
+		if (kernel_connect(sock->sock, (struct sockaddr *)&sin, sizeof(sin), 0) != 0){
+			printk(KERN_ERR "dnbd3: connection to host failed (ipv6)\n");
 			goto error;
 		}
+	}
+	// Request filesize
+	dnbd3_request.magic = dnbd3_packet_magic;
+	dnbd3_request.cmd = CMD_SELECT_IMAGE;
+	iov[0].iov_base = &dnbd3_request;
+	iov[0].iov_len = sizeof(dnbd3_request);
+	serializer_reset_write(&payload_buffer);
+	serializer_put_uint16(&payload_buffer, PROTOCOL_VERSION);
+	serializer_put_string(&payload_buffer, dev->imgname);
+	serializer_put_uint16(&payload_buffer, dev->rid);
+	serializer_put_uint8(&payload_buffer, 0); // is_server = false
+	iov[1].iov_base = &payload_buffer;
+	dnbd3_request.size = iov[1].iov_len = serializer_get_written_length(&payload_buffer);
+	fixup_request(dnbd3_request);
+	mlen = sizeof(dnbd3_request) + iov[1].iov_len;
+	if (kernel_sendmsg(sock->sock, &msg, iov, 2, mlen) != mlen) {
+		printk(KERN_ERR "dnbd3: could not send CMD_SIZE_REQUEST\n");
+		goto error;
+	}
+	// receive reply header
+	iov[0].iov_base = &dnbd3_reply;
+	iov[0].iov_len = sizeof(dnbd3_reply);
+	if (kernel_recvmsg(sock->sock, &msg, iov, 1, sizeof(dnbd3_reply), msg.msg_flags) != sizeof(dnbd3_reply)) {
+		printk(KERN_ERR "dnbd3: received corrupted reply header after CMD_SIZE_REQUEST\n");
+		goto error;
+	}
 
-		// receive reply payload
-		iov[0].iov_base = &dev->payload_buffer;
-		iov[0].iov_len = dnbd3_reply.size;
-		if (kernel_recvmsg(dev->sock, &msg, iov, 1, dnbd3_reply.size, msg.msg_flags) != dnbd3_reply.size) {
-			printk(KERN_ERR "dnbd3: could not read CMD_SELECT_IMAGE payload on handshake\n");
-			goto error;
-		}
+	// check reply header
+	fixup_reply(dnbd3_reply);
+	if (dnbd3_reply.cmd != CMD_SELECT_IMAGE ||
+			dnbd3_reply.size < 3 ||
+			dnbd3_reply.size > MAX_PAYLOAD ||
+			dnbd3_reply.magic != dnbd3_packet_magic) {
+		printk(KERN_ERR "dnbd3: received invalid reply to CMD_SIZE_REQUEST image does not exist on server\n");
+		goto error;
+	}
 
-		// handle/check reply payload
-		serializer_reset_read(&dev->payload_buffer, dnbd3_reply.size);
-		dev->cur_server.protocol_version = serializer_get_uint16(&dev->payload_buffer);
-		if (dev->cur_server.protocol_version < MIN_SUPPORTED_SERVER) {
-			printk(KERN_ERR "dnbd3: server version is lower than min supported version\n");
-			goto error;
-		}
+	// receive reply payload
+	iov[0].iov_base = &payload_buffer;
+	iov[0].iov_len = dnbd3_reply.size;
+	if (kernel_recvmsg(sock->sock, &msg, iov, 1, dnbd3_reply.size, msg.msg_flags) != dnbd3_reply.size) {
+		printk(KERN_ERR "dnbd3: could not read CMD_SELECT_IMAGE payload on handshake\n");
+		goto error;
+	}
 
-		name = serializer_get_string(&dev->payload_buffer);
-		if (dev->rid != 0 && strcmp(name, dev->imgname) != 0) {
-			printk(KERN_ERR "dnbd3: server offers image '%s', requested '%s'\n", name, dev->imgname);
-			goto error;
-		}
+	// handle/check reply payload
+	serializer_reset_read(&payload_buffer, dnbd3_reply.size);
+	server->protocol_version = serializer_get_uint16(&payload_buffer);
+	if (server->protocol_version < MIN_SUPPORTED_SERVER) {
+		printk(KERN_ERR "dnbd3: server version is lower than min supported version\n");
+		goto error;
+	}
 
-		if (strlen(dev->imgname) < strlen(name)) {
-			dev->imgname = krealloc(dev->imgname, strlen(name) + 1, GFP_ATOMIC );
-			if (dev->imgname == NULL ) {
-				printk(KERN_ERR "dnbd3: reallocating buffer for new image name failed\n");
-				goto error;
-			}
-		}
-		strcpy(dev->imgname, name);
-		rid = serializer_get_uint16(&dev->payload_buffer);
-		if (dev->rid != 0 && dev->rid != rid) {
-			printk(KERN_ERR "dnbd3: server provides rid %d, requested was %d\n", (int)rid, (int)dev->rid);
-			goto error;
-		}
+	name = serializer_get_string(&payload_buffer);
+	rid = serializer_get_uint16(&payload_buffer);
+	if (dev->rid != rid && strcmp(name, dev->imgname) != 0) {
+		printk(KERN_ERR "dnbd3: server offers image '%s', requested '%s'\n", name, dev->imgname);
+		goto error;
+	}
 
-		dev->rid = rid;
-		dev->reported_size = serializer_get_uint64(&dev->payload_buffer);
-		if (dev->reported_size < 4096) {
+	reported_size = serializer_get_uint64(&payload_buffer);
+	if (dev->reported_size == NULL) {
+		if (reported_size < 4096) {
 			printk(KERN_ERR "dnbd3: reported size by server is < 4096\n");
 			goto error;
 		}
-
-		// store image information
+		dev->reported_size = reported_size;
 		set_capacity(dev->disk, dev->reported_size >> 9); /* 512 Byte blocks */
-		printk(KERN_DEBUG "dnbd3: connected to image %s, filesize %llu\n", dev->imgname, dev->reported_size);
-		dev->update_available = 0;
-	} else { // Switching server, connection is already established and size request was executed
-
-		printk(KERN_DEBUG "dnbd3: changing server\n");
-		dev->sock = dev->better_sock;
-		dev->better_sock = NULL;
-		kernel_setsockopt(dev->sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout, sizeof(timeout));
-		kernel_setsockopt(dev->sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));
+	} else if (dev->reported_size != reported_size) {
+		printk(KERN_ERR "dnbd3: reported size by server is %llu but should be %llu\n", reported_size, dev->reported_size);
 	}
 
-	dev->panic = 0;
-	dev->panic_count = 0;
+	printk(KERN_DEBUG "dnbd3: connected to image %s, filesize %llu\n", dev->imgname, dev->reported_size);
+
+	mutex_unlock(&sock->lock);
 
-	refcount_inc(&dev->config_refs);
-	mutex_init(&dev->socket_lock);
-	// Enqueue request to request_queue_send for a fresh list of alt servers
-	//TODO refresh alt server list
+//	TODO add heartbeat
+	//	timer_setup(&dev->hb_timer, dnbd3_net_heartbeat, 0);
+	//	dev->hb_timer.expires = jiffies + HZ;
+	//	add_timer(&dev->hb_timer);
 
-	// add heartbeat timer
-	//TODO needed anymore=
-//	dev->heartbeat_count = 0;
-//	timer_setup(&dev->hb_timer, dnbd3_net_heartbeat, 0);
-//	dev->hb_timer.expires = jiffies + HZ;
-//	add_timer(&dev->hb_timer);
 	return 0;
 error:
-	if (dev->sock) {
-		sock_release(dev->sock);
-		dev->sock = NULL;
+	if (sock->sock) {
+		sock_release(sock->sock);
+		sock->sock = NULL;
 	}
-	dev->cur_server.host.type = 0;
-	dev->cur_server.host.port = 0;
 	if (req1) {
 		kfree(req1);
 	}
-	return -1;
+	mutex_unlock(&sock->lock);
+	return result;
 }
 
-
-int dnbd3_net_disconnect(dnbd3_device_t *dev)
+int dnbd3_socket_disconnect(dnbd3_device_t *dev, dnbd3_sock *sock)
 {
-	printk(KERN_DEBUG "dnbd3: net disconnect device %i\n", dev->minor);
-	if (dev->disconnecting)  {
-		return 0;
-	}
-
-	dev->disconnecting = 1;
+	printk(KERN_DEBUG "dnbd3: socket disconnect device %i\n", dev->minor);
+	mutex_lock(&sock->lock);
 
 	// clear heartbeat timer
 //	del_timer(&dev->hb_timer);
 
-	dev->discover = 0;
 
-	if (dev->sock) {
-		kernel_sock_shutdown(dev->sock, SHUT_RDWR);
+	if (sock->sock) {
+		kernel_sock_shutdown(sock->sock, SHUT_RDWR);
 	}
 
 	// clear socket
-	if (dev->sock) {
-		sock_release(dev->sock);
-		dev->sock = NULL;
+	if (sock->sock) {
+		sock_release(sock->sock);
+		sock->sock = NULL;
 	}
-	dev->cur_server.host.type = 0;
-	dev->cur_server.host.port = 0;
-
-	dev->disconnecting = 0;
 
+	mutex_unlock(&sock->lock);
+	mutex_destroy(&sock->lock);
 	return 0;
 }
 
+int dnbd3_net_disconnect(struct dnbd3_device_t *dev) {
+	int i;
+	int result;
+	for (i = 0; i < NUMBER_CONNECTIONS; i++) {
+		if (dev->socks[i].sock) {
+			if (dnbd3_socket_disconnect(dev, &dev->socks[i])) {
+				result = -EIO;
+			}
+		}
+	}
+	return result;
+}
+
+
 static void printHost(struct dnbd3_host_t *host, char *msg)
 {
 	if (host->type == HOST_IP4) {
@@ -269,7 +239,7 @@ static void printHost(struct dnbd3_host_t *host, char *msg)
 static void printServerList(struct dnbd3_device_t *dev)
 {
 	int i;
-	printHost(&dev->cur_server.host, "current server is");
+	printHost(&dev->initial_server.host, "initial server is");
 	for (i = 0; i < NUMBER_SERVERS; i++) {
 		if (dev->alt_servers[i].host.addr[0] != 0) {
 			printHost(&dev->alt_servers[i].host, "alternative server is");
@@ -283,13 +253,14 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd
 	dnbd3_device_t *dev = bdev->bd_disk->private_data;
 	char *imgname = NULL;
 	dnbd3_ioctl_t *msg = NULL;
+	int i;
 
 	printk(KERN_DEBUG "dnbd3: ioctl device %i, cmd %i, arg %lu\n", dev->minor, cmd, arg);
 	//unsigned long irqflags;
 
-	while (dev->disconnecting) {
-		// do nothing
-	}
+//	while (dev->disconnecting) {
+//		// do nothing
+//	}
 
 	if (arg != 0) {
 		msg = kmalloc(sizeof(*msg), GFP_KERNEL);
@@ -328,12 +299,12 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd
 		} else if (msg == NULL) {
 			result = -EINVAL;
 		} else {
-			if (sizeof(msg->host) != sizeof(dev->cur_server.host)) {
+			if (sizeof(msg->host) != sizeof(dev->initial_server.host)) {
 				printk(KERN_INFO "dnbd3: odd size bug#1 triggered in ioctl\n");
 			}
-			memcpy(&dev->cur_server.host, &msg->host, sizeof(msg->host));
-			dev->cur_server.failures = 0;
-			memcpy(&dev->initial_server, &dev->cur_server, sizeof(dev->initial_server));
+			memcpy(&dev->initial_server.host, &msg->host, sizeof(msg->host));
+			dev->initial_server.failures = 0;
+//			memcpy(&dev->initial_server, &dev->cur_server, sizeof(dev->initial_server));
 			dev->imgname = imgname;
 			dev->rid = msg->rid;
 			dev->use_server_provided_alts = msg->use_server_provided_alts;
@@ -348,22 +319,26 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd
 //			blk_queue->backing_dev_info.ra_pages = (msg->read_ahead_kb * 1024) / PAGE_SIZE;
 //#endif
 
-			printServerList(dev);
 
-			if (dnbd3_net_connect(dev) == 0) {
+			dev->socks[0].server = &dev->initial_server;
+			if (dnbd3_socket_connect(dev, &dev->socks[0]) == 0) {
+				printServerList(dev);
 				result = 0;
 				imgname = NULL; // Prevent kfree at the end
 			} else {
+				printk(KERN_ERR "dnbd3: failed to connect to initial server\n");
 				result = -ENOENT;
 				dev->imgname = NULL;
+				dev->socks[0].server = NULL;
 			}
+
 		}
 		break;
 
 	case IOCTL_CLOSE:
 		printk(KERN_DEBUG "dnbd3: ioctl close\n");
 		dnbd3_blk_fail_all_requests(dev);
-		result = dnbd3_net_disconnect(dev);
+		dnbd3_net_disconnect(dev);
 		dnbd3_blk_fail_all_requests(dev);
 		set_capacity(dev->disk, 0);
 		if (dev->imgname) {
diff --git a/src/kernel/block.h b/src/kernel/block.h
index 07bf950..49055d5 100644
--- a/src/kernel/block.h
+++ b/src/kernel/block.h
@@ -16,7 +16,7 @@
         h.msg_flags = MSG_WAITALL | MSG_NOSIGNAL; \
 	} while (0)
 
-int dnbd3_net_connect(dnbd3_device_t *dev);
+//int dnbd3_net_connect(dnbd3_device_t *dev);
 
 int dnbd3_net_disconnect(dnbd3_device_t *dev);
 
diff --git a/src/kernel/core.c b/src/kernel/core.c
index e92bd9a..db1f6de 100644
--- a/src/kernel/core.c
+++ b/src/kernel/core.c
@@ -120,16 +120,12 @@ static int dnbd3_add_device(dnbd3_device_t *dev, int minor)
 	blk_queue_max_hw_sectors(disk->queue, 65536);
 	disk->queue->limits.max_sectors = 256;
 
-	mutex_init(&dev->config_lock);
-	refcount_set(&dev->config_refs, 0);
-	refcount_set(&dev->refs, 1);
 	INIT_LIST_HEAD(&dev->list);
 	disk->major = major;
 	disk->first_minor = minor;
 	disk->fops = &dnbd3_fops;
 	disk->private_data = dev;
 	sprintf(disk->disk_name, "dnbd%i", minor);
-//	sprintf(disk->disk_name, "dnbd3%i", minor);
 	printk(KERN_DEBUG "dnbd3: add disk device %s\n", disk->disk_name);
 	add_disk(disk);
 	dnbd3_sysfs_init(dev);
@@ -207,9 +203,7 @@ static void dnbd3_dev_remove(struct dnbd3_device_t *dnbd3)
 		del_gendisk(disk);
 		blk_cleanup_queue(q);
 		blk_mq_free_tag_set(&dnbd3->tag_set);
-		if (dnbd3->sock) {
-			dnbd3_net_disconnect(dnbd3);
-		}
+		dnbd3_net_disconnect(dnbd3);
 		disk->private_data = NULL;
 		put_disk(disk);
 	}
@@ -217,11 +211,10 @@ static void dnbd3_dev_remove(struct dnbd3_device_t *dnbd3)
 
 static void dnbd3_put(struct dnbd3_device_t *dnbd3)
 {
-	if (refcount_dec_and_mutex_lock(&dnbd3->refs, &dnbd3_index_mutex)) {
-		idr_remove(&dnbd3_index_idr, dnbd3->minor);
-		mutex_unlock(&dnbd3_index_mutex);
-		dnbd3_dev_remove(dnbd3);
-	}
+	mutex_lock(&dnbd3_index_mutex);
+	idr_remove(&dnbd3_index_idr, dnbd3->minor);
+	mutex_unlock(&dnbd3_index_mutex);
+	dnbd3_dev_remove(dnbd3);
 }
 
 
@@ -239,9 +232,6 @@ static void __exit dnbd3_exit(void)
 		dnbd3 = list_first_entry(&del_list, struct dnbd3_device_t, list);
 		dnbd3_sysfs_exit(dnbd3);
 		list_del_init(&dnbd3->list);
-		if (refcount_read(&dnbd3->refs) != 1) {
-			printk(KERN_ERR "dnbd3: possibly leaking a device\n");
-		}
 		dnbd3_put(dnbd3);
 	}
 
diff --git a/src/kernel/dnbd3.h b/src/kernel/dnbd3.h
index 0a4ef67..7ad6b2f 100644
--- a/src/kernel/dnbd3.h
+++ b/src/kernel/dnbd3.h
@@ -31,9 +31,9 @@
 #include "serialize.h"
 
 
+#define NUMBER_CONNECTIONS 4
 
-typedef struct
-{
+typedef struct dnbd3_server_t {
 	dnbd3_host_t host;
 	uint64_t rtts[4];		// Last four round trip time measurements in microsecond
 	uint16_t protocol_version;	// dnbd3 protocol version of this server
@@ -41,13 +41,16 @@ typedef struct
 } dnbd3_server_t;
 
 
+typedef struct dnbd3_sock {
+	struct socket *sock;
+	struct mutex lock;
+	struct request *pending;
+	struct dnbd3_server_t *server;
+} dnbd3_sock;
+
 typedef struct dnbd3_device_t {
 	int minor;
 	struct blk_mq_tag_set tag_set;
-//	struct request_queue queue;
-	struct mutex config_lock;
-	refcount_t config_refs;
-	refcount_t refs;
 	struct list_head list;
 
 	// block
@@ -57,23 +60,26 @@ typedef struct dnbd3_device_t {
 	struct kobject kobj;
 
 	// network
+	dnbd3_sock socks[NUMBER_CONNECTIONS];
 	char *imgname;
-	struct socket *sock;
-	struct mutex socket_lock;
-	struct request *pending;
-	dnbd3_server_t cur_server, initial_server;
-	uint64_t cur_rtt;
-	serialized_buffer_t payload_buffer;
+//	struct socket *sock;
+//	struct mutex socket_lock;
+//	struct request *pending;
+	dnbd3_server_t initial_server;
+//	dnbd3_server_t cur_server, initial_server;
+//	uint64_t cur_rtt;
+//	serialized_buffer_t payload_buffer;
 	dnbd3_server_t alt_servers[NUMBER_SERVERS]; // array of alt servers
 	int new_servers_num;	// number of new alt servers that are waiting to be copied to above array
 	dnbd3_server_entry_t new_servers[NUMBER_SERVERS]; // pending new alt servers
-	uint8_t discover, panic, disconnecting, update_available, panic_count;
+//	uint8_t discover, panic, disconnecting, update_available, panic_count;
+	uint8_t update_available;
 	uint8_t use_server_provided_alts;
 	uint16_t rid;
 	uint32_t heartbeat_count;
 	uint64_t reported_size;
 	// server switch
-	struct socket *better_sock;
+//	struct socket *better_sock;
 
 
 	// process
@@ -100,11 +106,5 @@ typedef struct dnbd3_cmd {
 	uint32_t cmd_cookie;
 } dnbd3_cmd;
 
-typedef struct dnbd3_sock {
-	struct socket *sock;
-	struct mutex lock;
-	struct request *pending;
-	struct dnbd3_server_t *server;
-} dnbd3_sock;
 
 #endif /* DNBD_H_ */
diff --git a/src/kernel/mq.c b/src/kernel/mq.c
index 3b0bde5..98e6e14 100644
--- a/src/kernel/mq.c
+++ b/src/kernel/mq.c
@@ -11,27 +11,11 @@
 #include "block.h"
 
 #define DNBD3_CMD_REQUEUED 1
-//
-//static void dnbd3_config_put(struct dnbd3_device_t *dev)
-//{
-//	if (refcount_dec_and_mutex_lock(&dev->config_refs,
-//					&dev->config_lock)) {
-//
-//		dev->tag_set.timeout = 0;
-//		dev->disk->queue->limits.discard_granularity = 0;
-//		dev->disk->queue->limits.discard_alignment = 0;
-//		blk_queue_max_discard_sectors(dev->disk->queue, UINT_MAX);
-//		blk_queue_flag_clear(QUEUE_FLAG_DISCARD, dev->disk->queue);
-//
-//		mutex_unlock(&dev->config_lock);
-//		nbd_put(dev);
-//		module_put(THIS_MODULE);
-//	}
-//}
+
 
 #define dnbd3_priv_to_cmd(req)        ((req)->cmd_flags >> REQ_FLAG_BITS)
 
-static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int index)
+static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_sock *sock, struct dnbd3_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
 	dnbd3_request_t dnbd3_request;
@@ -44,7 +28,7 @@ static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int
 	sigset_t blocked, oldset;
 	void *kaddr;
 	int result;
-	dev->pending = req;
+	sock->pending = req;
 	init_msghdr(msg);
 
 	dnbd3_request.magic = dnbd3_packet_magic;
@@ -79,7 +63,7 @@ static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int
 	fixup_request(dnbd3_request);
 	iov.iov_base = &dnbd3_request;
 	iov.iov_len = sizeof(dnbd3_request);
-	if (kernel_sendmsg(dev->sock, &msg, &iov, 1, sizeof(dnbd3_request)) != sizeof(dnbd3_request)) {
+	if (kernel_sendmsg(sock->sock, &msg, &iov, 1, sizeof(dnbd3_request)) != sizeof(dnbd3_request)) {
 		printk(KERN_ERR "dnbd3: connection to server lost\n");
 		result = -EIO;
 		goto error;
@@ -88,7 +72,7 @@ static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int
 	// receive net reply
 	iov.iov_base = &dnbd3_reply;
 	iov.iov_len = sizeof(dnbd3_reply);
-	result = kernel_recvmsg(dev->sock, &msg, &iov, 1, sizeof(dnbd3_reply), msg.msg_flags);
+	result = kernel_recvmsg(sock->sock, &msg, &iov, 1, sizeof(dnbd3_reply), msg.msg_flags);
 	if (!result) {
 		printk(KERN_ERR "dnbd3: connection to server lost\n");
 		result = -EIO;
@@ -119,7 +103,7 @@ static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int
 		kaddr = kmap(bvec->bv_page) + bvec->bv_offset;
 		iov.iov_base = kaddr;
 		iov.iov_len = bvec->bv_len;
-		if (kernel_recvmsg(dev->sock, &msg, &iov, 1, bvec->bv_len, msg.msg_flags) != bvec->bv_len) {
+		if (kernel_recvmsg(sock->sock, &msg, &iov, 1, bvec->bv_len, msg.msg_flags) != bvec->bv_len) {
 			kunmap(bvec->bv_page);
 			sigprocmask(SIG_SETMASK, &oldset, NULL );
 			printk(KERN_ERR "dnbd3: could not receive form net to block layer\n");
@@ -129,10 +113,8 @@ static int dnbd3_send_cmd(struct dnbd3_device_t *dev, struct dnbd3_cmd *cmd, int
 
 		sigprocmask(SIG_SETMASK, &oldset, NULL );
 	}
-//
-//	__blk_end_request_all(req, 0);
 	blk_mq_end_request(req, 0);
-	dev->pending = NULL;
+	sock->pending = NULL;
 error:
 	return result;
 }
@@ -150,57 +132,54 @@ static int dnbd3_handle_cmd(struct dnbd3_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
 	struct dnbd3_device_t *dev = cmd->dnbd3;
+	struct dnbd3_sock *sock;
 	int ret = -1;
 
 	printk(KERN_DEBUG "dnbd3: handle request at position %lu and size %d, device %i\n", blk_rq_pos(req), blk_rq_bytes(req), dev->minor);
 
-	if (!refcount_inc_not_zero(&dev->config_refs)) {
-		dev_err_ratelimited(disk_to_dev(dev->disk), "socks array is empty\n");
-		blk_mq_start_request(req);
-		return -EINVAL;
-	}
+//	if (index >= 1) { // TODO use next server with good rtt for this request
+//		printk(KERN_INFO "dnbd3: index is %d", index);
+//		dev_err_ratelimited(disk_to_dev(dev->disk), "attempted send on invalid socket\n");
+//		blk_mq_start_request(req);
+//		return -EINVAL;
+//	}
 
-	if (index >= 1) { // TODO use next server with good rtt for this request
-		printk(KERN_INFO "dnbd3: index is %d", index);
+	sock = &dev->socks[index];
+	if (!sock->sock) {
+		printk(KERN_INFO "dnbd3: index is %d but no socket was found\n", index);
 		dev_err_ratelimited(disk_to_dev(dev->disk), "attempted send on invalid socket\n");
-//		nbd_config_put(nbd);
-//		TODO what to do here?
 		blk_mq_start_request(req);
 		return -EINVAL;
 	}
+
+
 	cmd->status = BLK_STS_OK;
 
 again:
 
 
-	mutex_lock(&dev->socket_lock);
-	if (!dev->sock) {
-		mutex_unlock(&dev->socket_lock);
-		printk(KERN_DEBUG "dnbd3: not connected, try to reconnect\n");
-		if (!dnbd3_net_connect(dev)) {
-			printk(KERN_ERR "dnbd3: failed to reconnect\n");
-			blk_mq_start_request(req);
-			return -EIO;
-		}
-		goto again;
+	mutex_lock(&sock->lock);
+	if (unlikely(!sock->sock)) {
+		mutex_unlock(&sock->lock);
+		printk(KERN_DEBUG "dnbd3: not connected\n");
+		return -EIO;
 	}
 
 	blk_mq_start_request(req);
-	if (unlikely(dev->pending && dev->pending != req)) {
+	if (unlikely(sock->pending && sock->pending != req)) {
 		dnbd3_requeue_cmd(cmd);
 		ret = 0;
 		goto out;
 	}
 
-	ret = dnbd3_send_cmd(dev, cmd, index);
+	ret = dnbd3_send_cmd(dev, sock, cmd, index);
 	if (ret == -EAGAIN) {
 		dev_err_ratelimited(disk_to_dev(dev->disk), "request send failed, requeueing\n");
 		dnbd3_requeue_cmd(cmd);
 		ret = 0;
 	}
 out:
-	mutex_unlock(&dev->socket_lock);
-//	nbd_config_put(nbd);
+	mutex_unlock(&sock->lock);
 	return ret;
 }
 
diff --git a/src/kernel/sysfs.c b/src/kernel/sysfs.c
index 4406072..118cbca 100644
--- a/src/kernel/sysfs.c
+++ b/src/kernel/sysfs.c
@@ -27,20 +27,20 @@
 #define MIN(a,b) ((a) < (b) ? (a) : (b))
 #endif
 
-ssize_t show_cur_server_addr(char *buf, dnbd3_device_t *dev)
-{
-	if (dev->cur_server.host.type == HOST_IP4)
-		return MIN(snprintf(buf, PAGE_SIZE, "%pI4,%d\n", dev->cur_server.host.addr, (int)ntohs(dev->cur_server.host.port)), PAGE_SIZE);
-	else if (dev->cur_server.host.type == HOST_IP6)
-		return MIN(snprintf(buf, PAGE_SIZE, "%pI6,%d\n", dev->cur_server.host.addr, (int)ntohs(dev->cur_server.host.port)), PAGE_SIZE);
-	*buf = '\0';
-	return 0;
-}
-
-ssize_t show_cur_server_rtt(char *buf, dnbd3_device_t *dev)
-{
-	return MIN(snprintf(buf, PAGE_SIZE, "%llu\n", (unsigned long long)dev->cur_rtt), PAGE_SIZE);
-}
+//ssize_t show_cur_server_addr(char *buf, dnbd3_device_t *dev)
+//{
+//	if (dev->cur_server.host.type == HOST_IP4)
+//		return MIN(snprintf(buf, PAGE_SIZE, "%pI4,%d\n", dev->cur_server.host.addr, (int)ntohs(dev->cur_server.host.port)), PAGE_SIZE);
+//	else if (dev->cur_server.host.type == HOST_IP6)
+//		return MIN(snprintf(buf, PAGE_SIZE, "%pI6,%d\n", dev->cur_server.host.addr, (int)ntohs(dev->cur_server.host.port)), PAGE_SIZE);
+//	*buf = '\0';
+//	return 0;
+//}
+//
+//ssize_t show_cur_server_rtt(char *buf, dnbd3_device_t *dev)
+//{
+//	return MIN(snprintf(buf, PAGE_SIZE, "%llu\n", (unsigned long long)dev->cur_rtt), PAGE_SIZE);
+//}
 
 ssize_t show_alt_server_num(char *buf, dnbd3_device_t *dev)
 {
@@ -100,19 +100,19 @@ ssize_t show_update_available(char *buf, dnbd3_device_t *dev)
 	return MIN(snprintf(buf, PAGE_SIZE, "%d\n", dev->update_available), PAGE_SIZE);
 }
 
-device_attr_t cur_server_addr =
-{
-	.attr = {.name = "cur_server_addr", .mode = 0444 },
-	.show   = show_cur_server_addr,
-	.store  = NULL,
-};
-
-device_attr_t cur_server_rtt =
-{
-	.attr = {.name = "cur_server_rtt", .mode = 0444 },
-	.show   = show_cur_server_rtt,
-	.store  = NULL,
-};
+//device_attr_t cur_server_addr =
+//{
+//	.attr = {.name = "cur_server_addr", .mode = 0444 },
+//	.show   = show_cur_server_addr,
+//	.store  = NULL,
+//};
+//
+//device_attr_t cur_server_rtt =
+//{
+//	.attr = {.name = "cur_server_rtt", .mode = 0444 },
+//	.show   = show_cur_server_rtt,
+//	.store  = NULL,
+//};
 
 device_attr_t alt_server_num =
 {
@@ -158,8 +158,8 @@ ssize_t device_show(struct kobject *kobj, struct attribute *attr, char *buf)
 
 struct attribute *device_attrs[] =
 {
-	&cur_server_addr.attr,
-	&cur_server_rtt.attr,
+//	&cur_server_addr.attr,
+//	&cur_server_rtt.attr,
 	&alt_server_num.attr,
 	&alt_servers.attr,
 	&image_name.attr,