/*
 * 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/sock.h>
#include <linux/wait.h>
#include <linux/sort.h>

#include "net.h"
#include "net-txrx.h"
#include "utils.h"
#include "clientconfig.h"
#include "mq.h"


#define dnbd3_sock_create(af,type,proto,sock) \
	sock_create_kern(&init_net, (af) == HOST_IP4 ? AF_INET : AF_INET6, \
			type, proto, sock)

#define dnbd3_sock_release(sock) \
	do { \
		sock_release((sock)->sock); \
		sock->sock = NULL; \
	}while (0)

#define dnbd3_is_sock_alive(s) ((s).sock && (s).server)


static int __dnbd3_socket_connect(struct dnbd3_sock *sock,
		struct dnbd3_server *server);
static int dnbd3_socket_connect(struct dnbd3_sock *sock,
		struct dnbd3_server *server);
static int dnbd3_socket_disconnect(struct dnbd3_sock *sock);

/*
 * Timer and workers
 */

/**
 * dnbd3_timer - the timer to start different workers
 * @arg: the timer_list used to get the dnbd3_device
 *
 * workers to start:
 * - panic_worker
 * - keepalive_worker for each connected socket
 * - discovery_worker
 */
static void dnbd3_timer(struct timer_list *arg)
{
	struct dnbd3_device *dev;
	unsigned long busy;
	int i;
	dev = container_of(arg, struct dnbd3_device, timer);
	queue_work(dnbd3_wq, &dev->panic_worker);
	busy = dnbd3_is_mq_busy(dev);

	if (dev->timer_count % TIMER_INTERVAL_KEEPALIVE_PACKET == 0) {
		for (i = 0; i < dev->number_connections; i++) {
			if (!test_bit(i, &busy) && dnbd3_is_sock_alive(dev->socks[i])) {
				queue_work(dnbd3_wq, &dev->socks[i].keepalive_worker);
			}
		}
	}

	/* start after 2 seconds */
	if (dev->timer_count % TIMER_INTERVAL_PROBE_NORMAL == 2) {
		queue_work(dnbd3_wq, &dev->discovery_worker);
	}

	dev->timer_count++;
	dev->timer.expires = jiffies + HZ;
	add_timer(&dev->timer);
}

/**
 * dnbd3_receive_worker - receives data from a socket
 * @work: the work used to get the dndb3_sock
 *
 * receives data until the socket is closed (returns 0)
 */
static void dnbd3_receive_worker(struct work_struct *work)
{
	struct dnbd3_sock *sock;
	dnbd3_reply_t reply;
	int result;
	sock = container_of(work, struct dnbd3_sock, receive_worker);
	debug_sock(sock, "receive worker is starting");

	while(1) { // loop until socket returns 0
		result = dnbd3_receive_cmd(sock, &reply);
		if (result == -EAGAIN) {
			continue;

		} else if (result <= 0) {
			error_sock(sock, "connection to server lost %d", result);
			goto error;

		}

		switch (reply.cmd) {
		case CMD_GET_BLOCK:
			result = dnbd3_receive_cmd_get_block_mq(sock, &reply);
			if (result <= 0) {
				error_sock(sock, "receive cmd get block mq failed %d",
						result);
				goto error;
			}
			continue;
		case CMD_GET_SERVERS:
			result = dnbd3_receive_cmd_get_servers(sock, &reply);
			if (result <= 0) {
				error_sock(sock, "receive cmd get servers failed %d",
						result);
				goto error;
			}
			break;
		case CMD_LATEST_RID:
			result = dnbd3_receive_cmd_latest_rid(sock, &reply);
			if (result <= 0) {
				error_sock(sock, "receive cmd latest rid failed %d",
						result);
				goto error;
			}
			break;
		case CMD_KEEPALIVE:
			if (reply.size != 0) {
				error_sock(sock, "got keep alive packet with payload");
				goto error;
			}
			debug_sock(sock, "keep alive received");
			break;
		case CMD_SELECT_IMAGE:
			result = dnbd3_receive_cmd_select_image(sock, &reply);
			if (result <= 0) {
				error_sock(sock, "receive cmd select image failed %d",
						result);
				goto error;
			}
			break;
		default:
			warn_sock(sock, "unknown command received");
			break;
		}
error:
		if (result == 0) {
			info_sock(sock, "result is 0, socket seems to be down");
			dnbd3_sock_release(sock);
			break;
		} else if (result < 0) {
			/* discovery takes care of to many failures */
			sock->server->failures++;
			warn_sock(sock, "receive error happened %d, total failures %d",
 					result, sock->server->failures);
		}
		debug_sock(sock, "receive completed, waiting for next receive");
	}

	debug_sock(sock, "receive work queue is stopped");
}


/**
 * dnbd3_receive_worker - sends a keepalive
 * @work: the work used to get the dndb3_sock
 */
static void dnbd3_keepalive_worker(struct work_struct *work)
{
	struct dnbd3_sock *sock;
	sock = container_of(work, struct dnbd3_sock, keepalive_worker);
	if (dnbd3_is_sock_alive(*sock)) {
		debug_sock(sock, "starting keepalive worker");
		if (mutex_trylock(&sock->tx_lock)) {
			dnbd3_send_request_cmd(sock, CMD_KEEPALIVE);
			mutex_unlock(&sock->tx_lock);
		}
	}
}

/**
 * dnbd3_compare_servers - comparator for the server
 * @lhs: left hand sign
 * @rhs: right hand sign
 */
static int dnbd3_compare_servers(const void *lhs, const void *rhs) {
	uint64_t l, r;
	struct dnbd3_server *lhs_server = *((struct dnbd3_server **) lhs);
	struct dnbd3_server *rhs_server = *((struct dnbd3_server **) rhs);

	l = lhs_server->host.type != 0 ? lhs_server->avg_rtt
			: RTT_UNREACHABLE * 2;
	r = rhs_server->host.type != 0 ? rhs_server->avg_rtt
			: RTT_UNREACHABLE * 2;
	return l - r;
}

/**
 * dnbd3_sort_server - sort the alt server according to their avg rtt
 * @dev: the dndb3 device
 *
 * the returned array has to be freed with kfree
 */
static struct dnbd3_server **dnbd3_sort_server(struct dnbd3_device *dev) {
	int i;
	struct dnbd3_server **sorted_servers = kmalloc(NUMBER_SERVERS *
			sizeof(struct dnbd3_server *), GFP_KERNEL);
	if (!sorted_servers) {
		debug_dev(dev, "kmalloc failed");
		return NULL;
	}

	for (i = 0; i < NUMBER_SERVERS; i++) {
		sorted_servers[i] = &dev->alt_servers[i];
	}
	sort(sorted_servers, NUMBER_SERVERS, sizeof(struct dnbd3_server *),
			&dnbd3_compare_servers, NULL);

	return sorted_servers;
}

//static int dnbd3_panic_connect(struct dnbd3_device *dev)
//{
//	struct dnbd3_server *working = NULL;
//	int i;
//	debug_dev(dev, "panic connect");
//	for (i = 0; i < NUMBER_CONNECTIONS; i++) {
//		if (dnbd3_is_sock_alive(dev->socks[i])) {
//			working = dev->socks[i].server;
//			debug_server(dev, working, "found server for panic");
//		}
//	}
//	if (working == NULL) {
//		for (i = 0; i < NUMBER_SERVERS; i++) {
//			if (!dnbd3_socket_connect(&dev->socks[0],
//					&dev->alt_servers[i])) {
//				working = &dev->alt_servers[i];
//				debug_server(dev, working, "found server for panic");
//			}
//		}
//	}
//	if (working == NULL) {
//		return -ENOENT;
//	}
//	for (i = 0; i < NUMBER_CONNECTIONS; i++) {
//		if (dev->socks[i].server != working) {
//			dnbd3_socket_connect(&dev->socks[i], working);
//		}
//	}
//	return 0;
//}

/**
 * dnbd3_compare_servers - comparator for the connecion plan
 * @lhs: left hand sign
 * @rhs: right hand sign
 */
static int dnbd3_compare_plan(const void *lhs, const void *rhs)
{
	uint64_t l, r;
	struct dnbd3_server *lhs_server = *((struct dnbd3_server **) lhs);
	struct dnbd3_server *rhs_server = *((struct dnbd3_server **) rhs);
	uint8_t *l_addr = lhs_server->host.addr;
	uint8_t *r_addr = rhs_server->host.addr;
	l = l_addr[0] + l_addr[1] + l_addr[2] + l_addr[3] + l_addr[4] +
			 l_addr[5] + l_addr[6] + l_addr[7] + l_addr[8] +
			 l_addr[9] + l_addr[10] + l_addr[11] + l_addr[12] +
			 l_addr[13] + l_addr[14] + l_addr[15] +
			 lhs_server->host.port;
	r = r_addr[0] + r_addr[1] + r_addr[2] + r_addr[3] + r_addr[4] +
			 r_addr[5] + r_addr[6] + r_addr[7] + r_addr[8] +
			 r_addr[9] + r_addr[10] + r_addr[11] + r_addr[12] +
			 r_addr[13] + r_addr[14] + r_addr[15] +
			 rhs_server->host.port;
	return l - r;
}

static void dnbd3_lock_all_socks(struct dnbd3_device *dev)
{
	int i;
	for (i = 0; i < dev->number_connections; i++) {
		mutex_lock(&dev->socks[i].tx_lock);
	}
}

static void dnbd3_unlock_all_socks(struct dnbd3_device *dev)
{
	int i;
	for (i = 0; i < dev->number_connections; i++) {
		mutex_unlock(&dev->socks[i].tx_lock);
	}
}

static void dnbd3_print_conenction_plan(struct dnbd3_device *dev,
		struct dnbd3_server **plan)
{
	int i;
	debug_dev(dev, "connection plan:");
	for (i = 0; i < dev->number_connections; i++) {
		debug_server(dev, plan[i], "server %d with avg rtt %llu:",
				i, plan[i]->avg_rtt);
	}
}

/**
 * dnbd3_adjust_connections - create a connection plan and connect
 * @dev: the dnbd3 device
 *
 * 1. sort the alt server after the avg rtt
 * 2. create a connection plan
 * 3. connect the plan
 */
static int dnbd3_adjust_connections(struct dnbd3_device *dev) {
	int i, j, fallback, alive;
	struct dnbd3_server **plan;
	struct dnbd3_server **servers = dnbd3_sort_server(dev);

	plan = kmalloc(sizeof(struct dnbd3_server *) * dev->number_connections,
			GFP_KERNEL);
	if (!plan) {
		error_dev(dev, "kmalloc failed");
	}

	if (servers && servers[0]->host.type != 0) {
		plan[0] = servers[0];
		fallback = 0;
		j = 1;
		for (i = 1; i < dev->number_connections; i++) {
			if (servers[j]->host.type != 0 &&
					servers[j]->avg_rtt < RTT_UNKNOWN) {
				if (RTT_FACTOR(plan[i - 1]->avg_rtt) >
						servers[j]->avg_rtt) {
					plan[i] = servers[j];
					j++;
				} else {
					plan[i] = plan[fallback];
					fallback++;
				}
			} else {
				plan[i] = plan[fallback];
				fallback++;
			}
		}
		kfree(servers);

		sort(plan, dev->number_connections, sizeof(struct dnbd3_server *),
			&dnbd3_compare_plan, NULL);
		dnbd3_print_conenction_plan(dev, plan);

		dnbd3_lock_all_socks(dev);
		alive = 0;
		for (i = 0; i < dev->number_connections; i++) {
			if (plan[i] != dev->socks[i].server ||
					!dnbd3_is_sock_alive(dev->socks[i])) {

				if (dnbd3_is_sock_alive(dev->socks[i])) {
					dnbd3_socket_disconnect(&dev->socks[i]);
				}
				if (!dnbd3_socket_connect(&dev->socks[i],
						plan[i])) {
					alive++;
				}
			} else {
				alive++;
			}
		}
		dnbd3_unlock_all_socks(dev);
		if (alive == 0) {
			return -EIO;
		}
		return 0;
	} else { /* there is nothing to connect */
		debug_dev(dev, "failed to adjust connections");
		if (servers) {
			kfree(servers);
		}
		return -ENONET;
	}


}

/**
 * dnbd3_panic_worker - handle panicked sockets
 * @work: the work used to get the dndb3_device
 *
 * 1. disconnect panicked socket
 * 2. reconnect to good alternative
 * 3. if no socket is connected do a panic_connect
 */
static void dnbd3_panic_worker(struct work_struct *work)
{
	struct dnbd3_device *dev;
	bool panic = false;
	int i;
	int sock_alive = 0;
	dev = container_of(work, struct dnbd3_device, panic_worker);
	for (i = 0; i < dev->number_connections; i++) {
		if (!dnbd3_is_sock_alive(dev->socks[i])
				|| dev->socks[i].server->failures > 1000) {
			panic = true;
			dnbd3_set_rtt_unreachable(dev->socks[i].server);
//			dnbd3_socket_disconnect(&dev->socks[i]);

		} else {
			sock_alive++;
		}
	}


	if (panic) {
		warn_dev(dev, "panicked, connections still alive %d",
				sock_alive);

		mutex_lock(&dev->device_lock);
		if (dnbd3_adjust_connections(dev)) {
			error_dev(dev, "failed to connect to any server");
			dev->connected = false;

		}
		mutex_unlock(&dev->device_lock);
	}
}

/**
 * dnbd3_meassure_rtt - meassure the rtt of a server
 * @dev: the device this server belongs to
 * @server: the server to meassure
 */
static int dnbd3_meassure_rtt(struct dnbd3_device *dev,
		struct dnbd3_server *server)
{
	struct timeval start, end;
	dnbd3_reply_t reply;
	int result;
	uint64_t rtt = RTT_UNREACHABLE;
	struct dnbd3_sock sock = {
			.sock_nr = dev->number_connections,
			.sock = NULL,
			.device = dev,
			.server = server
	};

	result = __dnbd3_socket_connect(&sock, server);
	if (result) {
		error_sock(&sock, "socket connect failed in rtt measurement");
		goto error;
	}
	result = dnbd3_send_request_cmd(&sock, CMD_SELECT_IMAGE);
	if (result <= 0) {
		error_sock(&sock, "request select image failed in rtt measurement");
		goto error;
	}

	result = dnbd3_receive_cmd(&sock, &reply);
	if (result <= 0) {
		error_sock(&sock, "receive select image failed in rtt measurement");
		goto error;

	}
	if (reply.magic != dnbd3_packet_magic || reply.cmd != CMD_SELECT_IMAGE
			|| reply.size < 4) {
		error_sock(&sock, "receive select image wrong header in rtt measurement");
		result = -EIO;
		goto error;
	}

	result = dnbd3_receive_cmd_select_image(&sock, &reply);
	if (result <= 0) {
		error_sock(&sock, "receive data select image failed in rtt measurement");
		goto error;
	}


	do_gettimeofday(&start);
	result = dnbd3_send_request_cmd(&sock, CMD_GET_BLOCK);
	if (result <= 0) {
		error_sock(&sock, "request test block failed in rtt measurement");
		goto error;
	}
	result = dnbd3_receive_cmd(&sock, &reply);
	if (reply.magic != dnbd3_packet_magic|| reply.cmd != CMD_GET_BLOCK
			|| reply.size != RTT_BLOCK_SIZE) {
		error_sock(&sock, "receive header cmd test block failed in rtt measurement");
		result = -EIO;
		goto error;
	}
	result =  dnbd3_receive_cmd_get_block_test(&sock, &reply);
	if (result <= 0) {
		error_sock(&sock, "receive test block failed in rtt measurement");
		goto error;
	}
	do_gettimeofday(&end); // end rtt measurement

	rtt = (uint64_t)((end.tv_sec - start.tv_sec) * 1000000ull
			+ (end.tv_usec - start.tv_usec));


error:
	sock.server->rtts[dev->discovery_count % 4] = rtt;
	sock.server->avg_rtt = dnbd3_average_rtt(sock.server);

	debug_sock(&sock, "meassured rrt: %llu; avg_rtt: %llu", rtt,
			sock.server->avg_rtt);
	if (result <= 0) {
		server->failures++;
	}
	if (sock.sock) {
		kernel_sock_shutdown(sock.sock, SHUT_RDWR);
		sock.server = NULL;
		sock_release(sock.sock);
		sock.sock = NULL;
	}
	return result;
}


/**
 * dnbd3_merge_new_server - merge the new server into the alt server list
 * @dev: the device
 * @new_server: the new server list to merge
 */
static void dnbd3_merge_new_server(struct dnbd3_device *dev,
		dnbd3_server_entry_t *new_server)
{
	int i;
	struct dnbd3_server *existing_server, *free_server, *failed_server;
	existing_server = NULL;
	free_server = NULL;
	failed_server = NULL;

	/* find servers in alternative servers */
	for (i = 0; i < NUMBER_SERVERS; i++) {
		if ((new_server->host.type == dev->alt_servers[i].host.type)
				&& (new_server->host.port == dev->alt_servers[i].host.port)
				&& (0 == memcmp(new_server->host.addr,
				   dev->alt_servers[i].host.addr,
				   (new_server->host.type == HOST_IP4 ? 4 : 16)
				   ))) {

			existing_server = &dev->alt_servers[i];
		} else if (dev->alt_servers[i].host.type == 0) {
			free_server = &dev->alt_servers[i];
		} else if (dev->alt_servers[i].failures > 20) {
			failed_server = &dev->alt_servers[i];
		}
	}

	if (existing_server) {
		if (new_server->failures == 1) { /* remove is requested */
			info_server(dev, new_server,
					"remove server is requested");
			// adjust connection will remove it later
			existing_server->host.type = 0;
			dnbd3_set_rtt_unreachable(existing_server);
		}
//		existing_server->failures = 0; // reset failure count
		return;
	} else if (free_server) {
		//TODO disconnect the server if it is connected
		free_server->host = new_server->host;
	} else if (failed_server) {
		failed_server->host = new_server->host;
		free_server = failed_server;
	} else {
		/* no server found to replace */
		return;
	}
	info_server(dev, free_server, "got new alternative server");
	free_server->failures = 0;
	free_server->protocol_version = 0;
	dnbd3_set_rtt_unknown(free_server);
}


/**
 * dnbd3_discovery_worker - handle discovery
 * @work: the work used to get the dndb3_device
 *
 * 1. check if new servers are available and set them to alternative servers
 * 2. meassure the rtt for all available servers
 * 3. adjust the connections
 */
static void dnbd3_discovery_worker(struct work_struct *work)
{
	struct dnbd3_device *dev;
	int i;
	struct dnbd3_server *server;
	dnbd3_server_entry_t *new_server;
	dev = container_of(work, struct dnbd3_device, discovery_worker);


	debug_dev(dev, "starting discovery worker new server num is %d",
			dev->new_servers_num);

	if (dev->new_servers_num) {
		mutex_lock(&dev->device_lock);
		for (i = 0; i < dev->new_servers_num; i++) {
			new_server = &dev->new_servers[i];
			if (new_server->host.type != 0) {
				dnbd3_merge_new_server(dev, new_server);
			}
		}
		dev->new_servers_num = 0;
		mutex_unlock(&dev->device_lock);
	}
	// measure rtt for all alt servers
	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 * 2;
				warn_server(dev, server,
						"failed to meassure rtt");
			}
		}
	}


	mutex_lock(&dev->device_lock);
	if (dnbd3_adjust_connections(dev)) {
		error_dev(dev, "failed to connect to any server");
		dev->connected = false;

	}
	mutex_unlock(&dev->device_lock);

	dev->discovery_count++;
}


/*
 * Connect and disconnect
 */


/**
 * __dnbd3_socket_connect - internal connect a socket to a server
 * @sock: the socket to connect
 * @server: the server
 */
static int __dnbd3_socket_connect(struct dnbd3_sock *sock,
		struct dnbd3_server *server)
{
	int result = 0;
	struct timeval timeout;

	if (server->host.port == 0 || server->host.type == 0) {
		error_sock(sock, "host or port not set");
		return -EIO;
	}
	if (sock->sock) {
		warn_sock(sock, "already connected");
		return -EIO;
	}

	timeout.tv_sec = SOCKET_TIMEOUT_CLIENT_DATA;
	timeout.tv_usec = 0;
	result = dnbd3_sock_create(server->host.type, SOCK_STREAM, IPPROTO_TCP,
			&sock->sock);
	if (result < 0) {
		error_sock(sock, "could not create socket");
		goto error;
	}

	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;
		result = kernel_connect(sock->sock, (struct sockaddr *)&sin,
				sizeof(sin), 0);
		if (result != 0) {
			error_sock(sock, "connection to host failed");
			goto error;
		}
	} 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;
		result = kernel_connect(sock->sock, (struct sockaddr *)&sin,
				sizeof(sin), 0);
		if (result != 0){
			error_sock(sock, "connection to host failed");
			goto error;
		}
	}

	return 0;
error:
	if (sock->sock) {
		dnbd3_sock_release(sock);
	}
	return result;
}

/**
 * dnbd3_socket_connect - connect a socket to a server
 * @sock: the socket
 * @server: the server to connect
 *
 * 1. connects the server to the socket
 * 2. select the image
 * 3. start receiver_worker and keepalive_worker
 */
static int dnbd3_socket_connect(struct dnbd3_sock *sock,
		struct dnbd3_server *server)
{
	int result = -EIO;
	dnbd3_reply_t reply;
	struct dnbd3_device *dev = sock->device;
	sock->server = server;

	debug_sock(sock, "socket connect");

	result = __dnbd3_socket_connect(sock, server);
	if (result) {
		error_sock(sock, "connection to socket failed");
		result = -EIO;
		goto error;
	}

	if (!sock->sock) {
		error_sock(sock, "socket is not connected");
		server->failures++;
		result = -EIO;
		goto error;
	}


	result = dnbd3_send_request_cmd(sock, CMD_SELECT_IMAGE);
	if (result <= 0) {
		error_sock(sock, "connection to image %s failed", dev->imgname);
		result = -EIO;
		goto error;
	}

	result = dnbd3_receive_cmd(sock, &reply);
	if (result <= 0) {
		error_sock(sock, "receive cmd to image %s failed",
				dev->imgname);
		result = -EIO;
		goto error;
	}
	if (reply.magic != dnbd3_packet_magic || reply.cmd != CMD_SELECT_IMAGE
			|| reply.size < 4) {
		error_sock(sock, "receive select image wrong header %s",
				dev->imgname);
		result = -EIO;
		goto error;
	}
	result = dnbd3_receive_cmd_select_image(sock, &reply);
	if (result <= 0) {
		error_sock(sock, "receive cmd select image %s failed",
				dev->imgname);
		result = -EIO;
		goto error;
	}
	debug_sock(sock, "connected to image %s, filesize %llu", dev->imgname,
			dev->reported_size);

	// start the receiver
	INIT_WORK(&sock->receive_worker, dnbd3_receive_worker);
	queue_work(dnbd3_wq, &sock->receive_worker);

	INIT_WORK(&sock->keepalive_worker, dnbd3_keepalive_worker);

	/* request alternative servers receiver will handle this */
	if (dnbd3_send_request_cmd(sock, CMD_GET_SERVERS) <= 0) {
		error_sock(sock, "failed to get servers in discovery");
	}

	return 0;
error:
	server->failures++;
	if (sock->sock) {
		kernel_sock_shutdown(sock->sock, SHUT_RDWR);
		cancel_work_sync(&sock->receive_worker);
		dnbd3_sock_release(sock);
	}
	return result;
}


/**
 * dnbd3_socket_disconnect - disconnect a socket
 * @sock: the socket to disconnect
 */
static int dnbd3_socket_disconnect(struct dnbd3_sock *sock)
{
	cancel_work_sync(&sock->keepalive_worker);

	debug_sock(sock, "socket disconnect");

	/*
	 * Important sequence to shut down socket
	 * 1. kernel_sock_shutdown
	 *      socket shutdown, receiver which block ins socket receive
	 *      returns 0
	 * 2. cancel_work_sync(receiver)
	 *      wait for the receiver to finish, so the socket is not used
	 *      anymore
	 * 3. sock_release
	 *      release the socket and set to NULL
	 */
	if (sock->sock) {
		kernel_sock_shutdown(sock->sock, SHUT_RDWR);
	}

	cancel_work_sync(&sock->receive_worker);

	dndb3_reque_busy_requests(sock);

	if (sock->sock) {
		dnbd3_sock_release(sock);
	}

	sock->server = NULL;
	return 0;
}


/**
 * dnbd3_net_connect - connect device
 * @dev: the device to connect
 *
 * dnbd3_device.alt_servers[0] must be set
 */
int dnbd3_net_connect(struct dnbd3_device *dev)
{
	int i, result;
	debug_dev(dev, "connecting to server");
	dev->socks = kmalloc(sizeof(struct dnbd3_sock) *
			dev->number_connections, GFP_KERNEL);
	if (!dev->socks) {
		error_dev(dev, "kmalloc failed");
	}
	memset(dev->socks, 0, sizeof(struct dnbd3_sock) *
			dev->number_connections);
	for (i = 0; i < dev->number_connections; i++) {
		dev->socks[i].device = dev;
		dev->socks[i].sock_nr = i;
		mutex_init(&dev->socks[i].tx_lock);
	}
	debug_dev(dev, "set nr hw queues to %d", dev->number_connections);
	blk_mq_update_nr_hw_queues(&dev->tag_set, dev->number_connections);

	if (dev->alt_servers[0].host.type == 0) {
		return -ENONET;
	}

	result = dnbd3_adjust_connections(dev);
	if (result) {
		error_dev(dev, "failed to connect to initial server");
		dnbd3_net_disconnect(dev);
		return -ENOENT;
	}
	dev->connected = true;

	debug_dev(dev, "connected, starting workers");
	INIT_WORK(&dev->discovery_worker, dnbd3_discovery_worker);
	INIT_WORK(&dev->panic_worker, dnbd3_panic_worker);
	timer_setup(&dev->timer, dnbd3_timer, 0);
	dev->timer.expires = jiffies + HZ;
	add_timer(&dev->timer);

	// alt_server[0] is the initial server
//	result = dnbd3_server_connect(dev, &dev->alt_servers[0]);
//	if (result) {
//		error_dev(dev, "failed to connect to initial server");
//		result = -ENOENT;
//		dev->imgname = NULL;
//		dev->socks[0].server = NULL;
//	}
	return result;
}

/**
 * dnbd3_net_disconnect - disconnect device
 * @dev: the device to disconnect
 */
int dnbd3_net_disconnect(struct dnbd3_device *dev)
{
	int i;
	int result = 0;

	if (!dev->socks) {
		info_dev(dev, "not connected");
	}

	del_timer_sync(&dev->timer);
	/* be sure it does not recover while disconnecting */
	cancel_work_sync(&dev->discovery_worker);
	cancel_work_sync(&dev->panic_worker);
	for (i = 0; i < dev->number_connections; i++) {
		if (dev->socks[i].sock) {
			mutex_lock(&dev->socks[i].tx_lock);
			if (dnbd3_socket_disconnect(&dev->socks[i])) {
				result = -EIO;
			}
			mutex_unlock(&dev->socks[i].tx_lock);
			mutex_destroy(&dev->socks[i].tx_lock);
		}
	}
	kfree(dev->socks);
	dev->socks = NULL;
	dev->connected = false;
	return result;
}