VILLASnode/lib/nodes/infiniband.cpp

/** Node type: infiniband
 *
 * @author Dennis Potter <dennis@dennispotter.eu>
 * @copyright 2014-2022, Institute for Automation of Complex Power Systems, EONERC
 * @license Apache 2.0
 *********************************************************************************/

#include <cstring>
#include <cmath>
#include <cinttypes>
#include <netdb.h>

#include <villas/node/config.hpp>
#include <villas/node_compat.hpp>
#include <villas/nodes/infiniband.hpp>
#include <villas/utils.hpp>
#include <villas/node/memory.hpp>
#include <villas/memory/ib.h>
#include <villas/timing.hpp>
#include <villas/exceptions.hpp>

using namespace villas;
using namespace villas::node;
using namespace villas::utils;

static
int ib_disconnect(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	struct ibv_wc wc[MAX(ib->recv_cq_size, ib->send_cq_size)];
	int wcs;

	n->logger->debug("Starting to clean up");

	rdma_disconnect(ib->ctx.id);

	/* If there is anything in the Completion Queue, it should be given back to the framework Receive Queue. */
	while (ib->conn.available_recv_wrs) {
		wcs = ibv_poll_cq(ib->ctx.recv_cq, ib->recv_cq_size, wc);

		ib->conn.available_recv_wrs -= wcs;

		for (int j = 0; j < wcs; j++)
			sample_decref((struct Sample *) (intptr_t) (wc[j].wr_id));
	}

	/* Send Queue */
	while ((wcs = ibv_poll_cq(ib->ctx.send_cq, ib->send_cq_size, wc)))
		for (int j = 0; j < wcs; j++)
			if (wc[j].wr_id > 0)
				sample_decref((struct Sample *) (intptr_t) (wc[j].wr_id));

	/* Destroy QP */
	rdma_destroy_qp(ib->ctx.id);

	n->logger->debug("Destroyed QP");

	return ib->stopThreads;
}

static
void ib_build_ibv(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	n->logger->debug("Starting to build IBV components");

	/* Create completion queues (No completion channel!) */
	ib->ctx.recv_cq = ibv_create_cq(ib->ctx.id->verbs, ib->recv_cq_size, nullptr, nullptr, 0);
	if (!ib->ctx.recv_cq)
		throw RuntimeError("Could not create receive completion queue");

	n->logger->debug("Created receive Completion Queue");

	ib->ctx.send_cq = ibv_create_cq(ib->ctx.id->verbs, ib->send_cq_size, nullptr, nullptr, 0);
	if (!ib->ctx.send_cq)
		throw RuntimeError("Could not create send completion queue");

	n->logger->debug("Created send Completion Queue");

	/* Prepare remaining Queue Pair (QP) attributes */
	ib->qp_init.send_cq = ib->ctx.send_cq;
	ib->qp_init.recv_cq = ib->ctx.recv_cq;

	/* Create the actual QP */
	ret = rdma_create_qp(ib->ctx.id, ib->ctx.pd, &ib->qp_init);
	if (ret)
		throw RuntimeError("Failed to create Queue Pair");

	n->logger->debug("Created Queue Pair with {} receive and {} send elements",
		ib->qp_init.cap.max_recv_wr, ib->qp_init.cap.max_send_wr);

	if (ib->conn.send_inline)
		n->logger->info("Maximum inline size is set to {} byte", ib->qp_init.cap.max_inline_data);
}

static
int ib_addr_resolved(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	n->logger->debug("Successfully resolved address");

	/* Build all components from IB Verbs */
	ib_build_ibv(n);

	/* Resolve address */
	ret = rdma_resolve_route(ib->ctx.id, ib->conn.timeout);
	if (ret)
		throw RuntimeError("Failed to resolve route");

	return 0;
}

static
int ib_route_resolved(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	struct rdma_conn_param cm_params;
	memset(&cm_params, 0, sizeof(cm_params));

	/* Send connection request */
	ret = rdma_connect(ib->ctx.id, &cm_params);
	if (ret)
		throw RuntimeError("Failed to connect");

	n->logger->debug("Called rdma_connect");

	return 0;
}

static
int ib_connect_request(NodeCompat *n, struct rdma_cm_id *id)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	n->logger->debug("Received a connection request!");

	ib->ctx.id = id;
	ib_build_ibv(n);

	struct rdma_conn_param cm_params;
	memset(&cm_params, 0, sizeof(cm_params));

	/* Accept connection request */
	ret = rdma_accept(ib->ctx.id, &cm_params);
	if (ret)
		throw RuntimeError("Failed to connect");

	n->logger->info("Successfully accepted connection request");

	return 0;
}

int villas::node::ib_reverse(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();

	SWAP(ib->conn.src_addr, ib->conn.dst_addr);

	return 0;
}

int villas::node::ib_parse(NodeCompat *n, json_t *json)
{
	auto *ib = n->getData<struct infiniband>();

	throw ConfigError(json, "The infiniband node-type is currently broken!");

	int ret;
	char *local = nullptr, *remote = nullptr, *lasts;
	const char *transport_mode = "RC";
	int timeout = 1000;
	int recv_cq_size = 128;
	int send_cq_size = 128;
	int max_send_wr = 128;
	int max_recv_wr = 128;
	int max_inline_data = 0;
	int send_inline = 1;
	int vectorize_in = 1;
	int vectorize_out = 1;
	int buffer_subtraction = 16;
	int use_fallback = 1;

	/* Parse JSON files and copy to local variables */
	json_t *json_in = nullptr;
	json_t *json_out = nullptr;
	json_error_t err;

	ret = json_unpack_ex(json, &err, 0, "{ s?: o, s?: o, s?: s }",
		"in", &json_in,
		"out", &json_out,
		"rdma_transport_mode", &transport_mode
	);
	if (ret)
		throw ConfigError(json, err, "node-config-node-ib");


	if (json_in) {
		ret = json_unpack_ex(json_in, &err, 0, "{ s?: s, s?: i, s?: i, s?: i, s?: i}",
			"address", &local,
			"cq_size", &recv_cq_size,
			"max_wrs", &max_recv_wr,
			"vectorize", &vectorize_in,
			"buffer_subtraction", &buffer_subtraction
		);
		if (ret)
			throw ConfigError(json_in, err, "node-config-node-ib-in");
	}

	if (json_out) {
		ret = json_unpack_ex(json_out, &err, 0, "{ s?: s, s?: i, s?: i, s?: i, s?: i, s?: b, s?: i, s?: b, s?: i}",
			"address", &remote,
			"resolution_timeout", &timeout,
			"cq_size", &send_cq_size,
			"max_wrs", &max_send_wr,
			"max_inline_data", &max_inline_data,
			"send_inline", &send_inline,
			"vectorize", &vectorize_out,
			"use_fallback", &use_fallback,
			"periodic_signaling", &ib->periodic_signaling
		);
		if (ret)
			throw ConfigError(json_out, err, "node-config-node-ib-out");

		if (remote) {
			ib->is_source = 1;

			n->logger->debug("Setup as source and target");
		}
	}
	else {
		ib->is_source = 0;

		n->logger->debug("Setup as target");
	}

	/* Set fallback mode */
	ib->conn.use_fallback = use_fallback;

	/* Set vectorize mode. Do not print, since framework will print this information */
	n->in.vectorize = vectorize_in;
	n->out.vectorize = vectorize_out;

	/* Set buffer subtraction */
	ib->conn.buffer_subtraction = buffer_subtraction;

	n->logger->debug("Set buffer subtraction to {}", buffer_subtraction);

	/* Translate IP:PORT to a struct addrinfo */
	char *ip_adr = strtok_r(local, ":", &lasts);
	char *port = strtok_r(nullptr, ":", &lasts);

	ret = getaddrinfo(ip_adr, port, nullptr, &ib->conn.src_addr);
	if (ret)
		throw RuntimeError("Failed to resolve local address '{}': {}", local, gai_strerror(ret));

	n->logger->debug("Translated {}:{} to a struct addrinfo", ip_adr, port);

	/* Translate port space */
	if (strcmp(transport_mode, "RC") == 0) {
		ib->conn.port_space = RDMA_PS_TCP;
		ib->qp_init.qp_type = IBV_QPT_RC;
	}
	else if (strcmp(transport_mode, "UC") == 0) {
#ifdef RDMA_CMA_H_CUSTOM
		ib->conn.port_space = RDMA_PS_IB;
		ib->qp_init.qp_type = IBV_QPT_UC;
#else
		throw RuntimeError("Unreliable Connected (UC) mode is only available with an adapted version of librdma. "
		                   "Please read the Infiniband node type Documentation for more information on UC!");
#endif
	}
	else if (strcmp(transport_mode, "UD") == 0) {
		ib->conn.port_space = RDMA_PS_UDP;
		ib->qp_init.qp_type = IBV_QPT_UD;
	}
	else
		throw RuntimeError("Invalid transport_mode = '{}'!", transport_mode);

	n->logger->debug("Set transport mode to {}", transport_mode);

	/* Set timeout */
	ib->conn.timeout = timeout;

	n->logger->debug("Set timeout to {}", timeout);

	/* Set completion queue size */
	ib->recv_cq_size = recv_cq_size;
	ib->send_cq_size = send_cq_size;

	n->logger->debug("Set Completion Queue size to {} & {} (in & out)",
		recv_cq_size, send_cq_size);


	/* Translate inline mode */
	ib->conn.send_inline = send_inline;

	n->logger->debug("Set send_inline to {}", send_inline);

	/* Set max. send and receive Work Requests */
	ib->qp_init.cap.max_send_wr = max_send_wr;
	ib->qp_init.cap.max_recv_wr = max_recv_wr;

	n->logger->debug("Set max_send_wr and max_recv_wr to {} and {}, respectively",
		max_send_wr, max_recv_wr);

	/* Set available receive Work Requests to 0 */
	ib->conn.available_recv_wrs = 0;

	/* Set remaining QP attributes */
	ib->qp_init.cap.max_send_sge = 4;
	ib->qp_init.cap.max_recv_sge = (ib->conn.port_space == RDMA_PS_UDP) ? 5 : 4;

	/* Set number of bytes to be send inline */
	ib->qp_init.cap.max_inline_data = max_inline_data;

	/* If node will send data, set remote address */
	if (ib->is_source) {
		/* Translate address info */
		char *ip_adr = strtok_r(remote, ":", &lasts);
		char *port = strtok_r(nullptr, ":", &lasts);

		ret = getaddrinfo(ip_adr, port, nullptr, &ib->conn.dst_addr);
		if (ret)
			throw RuntimeError("Failed to resolve remote address '{}': {}", remote, gai_strerror(ret));

		n->logger->debug("Translated {}:{} to a struct addrinfo", ip_adr, port);
	}

	return 0;
}

int villas::node::ib_check(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();

	/* Check if read substraction makes sense */
	if (ib->conn.buffer_subtraction <  2 * n->in.vectorize)
		throw RuntimeError("The buffer substraction value must be bigger than 2 * in.vectorize");

	if (ib->conn.buffer_subtraction >= ib->qp_init.cap.max_recv_wr - n->in.vectorize)
		throw RuntimeError("The buffer substraction value cannot be bigger than in.max_wrs - in.vectorize");

	/* Check if the set value is a power of 2, and warn the user if this is not the case */
	unsigned max_send_pow = (int) pow(2, ceil(log2(ib->qp_init.cap.max_send_wr)));
	unsigned max_recv_pow = (int) pow(2, ceil(log2(ib->qp_init.cap.max_recv_wr)));

	if (ib->qp_init.cap.max_send_wr != max_send_pow) {
		n->logger->warn("Max nr. of send WRs ({}) is not a power of 2! It will be changed to a power of 2: {}",
			ib->qp_init.cap.max_send_wr, max_send_pow);

		/* Change it now, because otherwise errors are possible in ib_start(). */
		ib->qp_init.cap.max_send_wr = max_send_pow;
	}

	if (ib->qp_init.cap.max_recv_wr != max_recv_pow) {
		n->logger->warn("Max nr. of recv WRs ({}) is not a power of 2! It will be changed to a power of 2: {}",
			ib->qp_init.cap.max_recv_wr, max_recv_pow);

		/* Change it now, because otherwise errors are possible in ib_start(). */
		ib->qp_init.cap.max_recv_wr = max_recv_pow;
	}

	/* Check maximum size of max_recv_wr and max_send_wr */
	if (ib->qp_init.cap.max_send_wr > 8192)
		n->logger->warn("Max number of send WRs ({}) is bigger than send queue!", ib->qp_init.cap.max_send_wr);

	if (ib->qp_init.cap.max_recv_wr > 8192)
		n->logger->warn("Max number of receive WRs ({}) is bigger than send queue!", ib->qp_init.cap.max_recv_wr);

	/* Set periodic signaling
	 * This is done here, so that it uses the checked max_send_wr value */
	if (ib->periodic_signaling == 0)
		ib->periodic_signaling = ib->qp_init.cap.max_send_wr / 2;

	/* Warn user if he changed the default inline value */
	if (ib->qp_init.cap.max_inline_data != 0)
		n->logger->warn("You changed the default value of max_inline_data. This might influence the maximum number "
			"of outstanding Work Requests in the Queue Pair and can be a reason for the Queue Pair creation to fail");

	return 0;
}

char * villas::node::ib_print(NodeCompat *n)
{
	return 0;
}

int villas::node::ib_destroy(NodeCompat *n)
{
	return 0;
}

static
void ib_create_bind_id(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	/* Create rdma_cm_id
	 *
	 * The unreliable connected mode is officially not supported by the rdma_cm library. Only the Reliable
	 * Connected mode (RDMA_PS_TCP) and the Unreliable Datagram mode (RDMA_PS_UDP). Although it is not officially
	 * supported, it is possible to use it with a few small adaptions to the sourcecode. To enable the
	 * support for UC connections follow the steps below:
	 *
	 * 1. git clone https://github.com/linux-rdma/rdma-core
	 * 2. cd rdma-core
	 * 2. Edit librdmacm/cma.c and remove the keyword 'static' in front of:
	 *
	 *     static int rdma_create_id2(struct rdma_event_channel *channel,
	 *         struct rdma_cm_id **id, void *context,
	 *         enum rdma_port_space ps, enum ibv_qp_type qp_type)
	 *
	 * 3. Edit librdmacm/rdma_cma.h and add the following two entries to the file:
	 *
	 *     #define RDMA_CMA_H_CUSTOM
	 *
	 *     int rdma_create_id2(struct rdma_event_channel *channel,
	 *         struct rdma_cm_id **id, void *context,
	 *         enum rdma_port_space ps, enum ibv_qp_type qp_type);
	 *
	 * 4. Edit librdmacm/librdmacm.map and add a new line with:
	 *
	 *     rdma_create_id2
	 *
	 * 5. ./build.sh
	 * 6. cd build && sudo make install
	 *
	 */
#ifdef RDMA_CMA_H_CUSTOM
	ret = rdma_create_id2(ib->ctx.ec, &ib->ctx.id, nullptr, ib->conn.port_space, ib->qp_init.qp_type);
#else
	ret = rdma_create_id(ib->ctx.ec, &ib->ctx.id, nullptr, ib->conn.port_space);
#endif
	if (ret)
		throw RuntimeError("Failed to create rdma_cm_id: {}", gai_strerror(ret));

	n->logger->debug("Created rdma_cm_id");

	/* Bind rdma_cm_id to the HCA */
	ret = rdma_bind_addr(ib->ctx.id, ib->conn.src_addr->ai_addr);
	if (ret)
		throw RuntimeError("Failed to bind to local device: {}", gai_strerror(ret));

	n->logger->debug("Bound rdma_cm_id to Infiniband device");

	/* The ID will be overwritten for the target. If the event type is
	 * RDMA_CM_EVENT_CONNECT_REQUEST, >then this references a new id for
	 * that communication.
	 */
	ib->ctx.listen_id = ib->ctx.id;
}

static
void ib_continue_as_listen(NodeCompat *n, struct rdma_cm_event *event)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	if (ib->conn.use_fallback)
		n->logger->warn("Trying to continue as listening node");
	else
		throw RuntimeError("Cannot establish a connection with remote host! If you want that {} tries to "
			"continue as listening node in such cases, set use_fallback = true in the configuration");

	n->setState(State::STARTED);

	/* Acknowledge event */
	rdma_ack_cm_event(event);

	/* Destroy ID */
	rdma_destroy_id(ib->ctx.listen_id);

	/* Create rdma_cm_id and bind to device */
	ib_create_bind_id(n);

	/* Listen to id for events */
	ret = rdma_listen(ib->ctx.listen_id, 10);
	if (ret)
		throw RuntimeError("Failed to listen to rdma_cm_id");

	/* Node is not a source (and will not send data */
	ib->is_source = 0;

	n->logger->info("Use listening mode");
}

static
void * ib_rdma_cm_event_thread(void *ctx)
{
	auto *n = (NodeCompat *) ctx;
	auto *ib = n->getData<struct infiniband>();
	struct rdma_cm_event *event;
	int ret = 0;

	n->logger->debug("Started rdma_cm_event thread");

	/* Wait until node is completely started */
	while (n->getState() != State::STARTED);

	/* Monitor event channel */
	while (rdma_get_cm_event(ib->ctx.ec, &event) == 0) {
		n->logger->debug("Received communication event: {}", rdma_event_str(event->event));

		switch(event->event) {
			case RDMA_CM_EVENT_ADDR_RESOLVED:
				ret = ib_addr_resolved(n);
				break;

			case RDMA_CM_EVENT_ADDR_ERROR:
				n->logger->warn("Address resolution (rdma_resolve_addr) failed!");

				ib_continue_as_listen(n, event);

				break;

			case RDMA_CM_EVENT_ROUTE_RESOLVED:
				ret = ib_route_resolved(n);
				break;

			case RDMA_CM_EVENT_ROUTE_ERROR:
				n->logger->warn("Route resolution (rdma_resovle_route) failed!");

				ib_continue_as_listen(n, event);

				break;

			case RDMA_CM_EVENT_UNREACHABLE:
				n->logger->warn("Remote server unreachable!");

				ib_continue_as_listen(n, event);
				break;

			case RDMA_CM_EVENT_CONNECT_REQUEST:
				ret = ib_connect_request(n, event->id);

				/* A target UDP node will never really connect. In order to receive data,
				 * we set it to connected after it answered the connection request
				 * with rdma_connect.
				 */
				if (ib->conn.port_space == RDMA_PS_UDP && !ib->is_source)
					n->setState(State::CONNECTED);
				else
					n->setState(State::PENDING_CONNECT);

				break;

			case RDMA_CM_EVENT_CONNECT_ERROR:
				n->logger->warn("An error has occurred trying to establish a connection!");

				ib_continue_as_listen(n, event);

				break;

			case RDMA_CM_EVENT_REJECTED:
				n->logger->warn("Connection request or response was rejected by the remote end point!");

				ib_continue_as_listen(n, event);

				break;

			case RDMA_CM_EVENT_ESTABLISHED:
				/* If the connection is unreliable connectionless, set appropriate variables */
				if (ib->conn.port_space == RDMA_PS_UDP) {
					ib->conn.ud.ud = event->param.ud;
					ib->conn.ud.ah = ibv_create_ah(ib->ctx.pd, &ib->conn.ud.ud.ah_attr);
				}

				n->setState(State::CONNECTED);

				n->logger->info("Connection established");

				break;

			case RDMA_CM_EVENT_DISCONNECTED:
				n->setState(State::STARTED);

				ret = ib_disconnect(n);

				if (!ret)
					n->logger->info("Host disconnected. Ready to accept new connections.");

				break;

			case RDMA_CM_EVENT_TIMEWAIT_EXIT:
				break;

			default:
				throw RuntimeError("Unknown event occurred: {}", event->event);
		}

		rdma_ack_cm_event(event);

		if (ret)
			break;
	}

	return nullptr;
}

int villas::node::ib_start(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	n->logger->debug("Started ib_start");

	/* Create event channel */
	ib->ctx.ec = rdma_create_event_channel();
	if (!ib->ctx.ec)
		throw RuntimeError("Failed to create event channel!");

	n->logger->debug("Created event channel");

	/* Create rdma_cm_id and bind to device */
	ib_create_bind_id(n);

	n->logger->debug("Initialized Work Completion Buffer");

	/* Resolve address or listen to rdma_cm_id */
	if (ib->is_source) {
		/* Resolve address */
		ret = rdma_resolve_addr(ib->ctx.id, nullptr, ib->conn.dst_addr->ai_addr, ib->conn.timeout);
		if (ret)
			throw RuntimeError("Failed to resolve remote address after {}ms: {}", ib->conn.timeout, gai_strerror(ret));
	}
	else {
		/* Listen on rdma_cm_id for events */
		ret = rdma_listen(ib->ctx.listen_id, 10);
		if (ret)
			throw RuntimeError("Failed to listen to rdma_cm_id");

		n->logger->debug("Started to listen to rdma_cm_id");
	}

	/* Allocate protection domain */
	ib->ctx.pd = ibv_alloc_pd(ib->ctx.id->verbs);
	if (!ib->ctx.pd)
		throw RuntimeError("Could not allocate protection domain");

	n->logger->debug("Allocated Protection Domain");

	/* Allocate space for 40 Byte GHR. We don't use this. */
	if (ib->conn.port_space == RDMA_PS_UDP) {
		ib->conn.ud.grh_ptr = new char[GRH_SIZE];
		if (!ib->conn.ud.grh_ptr)
			throw MemoryAllocationError();

		ib->conn.ud.grh_mr = ibv_reg_mr(ib->ctx.pd, ib->conn.ud.grh_ptr, GRH_SIZE, IBV_ACCESS_LOCAL_WRITE);
	}

	/* Several events should occur on the event channel, to make
	 * sure the nodes are succesfully connected.
	 */
	n->logger->debug("Starting to monitor events on rdma_cm_id");

	/* Create thread to monitor rdma_cm_event channel */
	ret = pthread_create(&ib->conn.rdma_cm_event_thread, nullptr, ib_rdma_cm_event_thread, n);
	if (ret)
		throw RuntimeError("Failed to create thread to monitor rdma_cm events: {}", gai_strerror(ret));

	return 0;
}

int villas::node::ib_stop(NodeCompat *n)
{
	auto *ib = n->getData<struct infiniband>();
	int ret;

	n->logger->debug("Called ib_stop");

	ib->stopThreads = 1;

	/* Call RDMA disconnect function
	 * Will flush all outstanding WRs to the Completion Queue and
	 * will call RDMA_CM_EVENT_DISCONNECTED if that is done.
	 */
	if (n->getState() == State::CONNECTED && ib->conn.port_space != RDMA_PS_UDP) {
		ret = rdma_disconnect(ib->ctx.id);

		if (ret)
			throw RuntimeError("Error while calling rdma_disconnect: {}", gai_strerror(ret));

		n->logger->debug("Called rdma_disconnect");
	}
	else {
		pthread_cancel(ib->conn.rdma_cm_event_thread);

		n->logger->debug("Called pthread_cancel() on communication management thread.");
	}

	n->logger->info("Disconnecting... Waiting for threads to join.");

	/* Wait for event thread to join */
	ret = pthread_join(ib->conn.rdma_cm_event_thread, nullptr);
	if (ret)
		throw RuntimeError("Error while joining rdma_cm_event_thread: {}", ret);

	n->logger->debug("Joined rdma_cm_event_thread");

	/* Destroy RDMA CM ID */
	rdma_destroy_id(ib->ctx.id);
	n->logger->debug("Destroyed rdma_cm_id");

	/* Dealloc Protection Domain */
	ibv_dealloc_pd(ib->ctx.pd);
	n->logger->debug("Destroyed protection domain");

	/* Destroy event channel */
	rdma_destroy_event_channel(ib->ctx.ec);
	n->logger->debug("Destroyed event channel");

	n->logger->info("Successfully stopped node");

	return 0;
}

int villas::node::ib_read(NodeCompat *n, struct Sample * const smps[], unsigned cnt)
{
	auto *ib = n->getData<struct infiniband>();
	struct ibv_wc wc[cnt];
	struct ibv_recv_wr wr[cnt], *bad_wr = nullptr;
    	struct ibv_sge sge[cnt][ib->qp_init.cap.max_recv_sge];
	struct ibv_mr *mr;
	struct timespec ts_receive;
	int ret = 0, wcs = 0, read_values = 0, max_wr_post;

	n->logger->debug("ib_read is called");

	if (n->getState() == State::CONNECTED || n->getState() == State::PENDING_CONNECT) {

		max_wr_post = cnt;

		/* Poll Completion Queue
		 * If we've already posted enough receive WRs, try to pull cnt
		 */
		if (ib->conn.available_recv_wrs >= (ib->qp_init.cap.max_recv_wr - ib->conn.buffer_subtraction) ) {
			for (int i = 0; ; i++) {
				if (i % CHK_PER_ITER == CHK_PER_ITER - 1) pthread_testcancel();

				/* If IB node disconnects or if it is still in State::PENDING_CONNECT, ib_read
				 * should return immediately if this condition holds
				 */
				if (n->getState() != State::CONNECTED) return 0;

				wcs = ibv_poll_cq(ib->ctx.recv_cq, cnt, wc);
				if (wcs) {
					/* Get time directly after something arrived in Completion Queue */
					ts_receive = time_now();

					n->logger->debug("Received {} Work Completions", wcs);

					read_values = wcs; /* Value to return */
					max_wr_post = wcs; /* Make space free in smps[] */

					break;
				}
			}

			/* All samples (wcs * received + unposted) should be released. Let
			 * *release be equal to allocated.
			 *
			 * This is set in the framework, before this function was called.
			 */
		}
		else {
			ib->conn.available_recv_wrs += max_wr_post;

			// TODO: fix release logic
			// *release = 0; /* While we fill the receive queue, we always use all samples */
		}

		/* Get Memory Region */
		mr = memory::ib_get_mr(pool_buffer(sample_pool(smps[0])));

		for (int i = 0; i < max_wr_post; i++) {
			int j = 0;

			/* Prepare receive Scatter/Gather element */

			/* First 40 byte of UD data are GRH and unused in our case */
			if (ib->conn.port_space == RDMA_PS_UDP) {
				sge[i][j].addr = (uint64_t) ib->conn.ud.grh_ptr;
    				sge[i][j].length = GRH_SIZE;
    				sge[i][j].lkey = ib->conn.ud.grh_mr->lkey;

				j++;
			}

			/* Sequence */
			sge[i][j].addr = (uint64_t) &smps[i]->sequence;
			sge[i][j].length = sizeof(smps[i]->sequence);
			sge[i][j].lkey = mr->lkey;

			j++;

			/* Timespec origin */
			sge[i][j].addr = (uint64_t) &smps[i]->ts.origin;
			sge[i][j].length = sizeof(smps[i]->ts.origin);
			sge[i][j].lkey = mr->lkey;

			j++;

    			sge[i][j].addr = (uint64_t) &smps[i]->data;
    			sge[i][j].length = SAMPLE_DATA_LENGTH(DEFAULT_SAMPLE_LENGTH);
    			sge[i][j].lkey = mr->lkey;

			j++;

    			/* Prepare a receive Work Request */
    			wr[i].wr_id = (uintptr_t) smps[i];
			wr[i].next = &wr[i+1];
    			wr[i].sg_list = sge[i];
    			wr[i].num_sge = j;
		}

		wr[max_wr_post-1].next = nullptr;

		n->logger->debug("Prepared {} new receive Work Requests", max_wr_post);
		n->logger->debug("{} receive Work Requests in Receive Queue", ib->conn.available_recv_wrs);

		/* Post list of Work Requests */
		ret = ibv_post_recv(ib->ctx.id->qp, &wr[0], &bad_wr);
		if (ret)
			throw RuntimeError("Was unable to post receive WR: {}, bad WR ID: {:#x}", ret, bad_wr->wr_id);

		n->logger->debug("Succesfully posted receive Work Requests");

		/* Doesn't start if wcs == 0 */
		for (int j = 0; j < wcs; j++) {
			if ( !( (wc[j].opcode & IBV_WC_RECV) && wc[j].status == IBV_WC_SUCCESS) ) {
				/* Drop all values, we don't know where the error occured */
				read_values = 0;
			}

			if (wc[j].status == IBV_WC_WR_FLUSH_ERR)
				n->logger->debug("Received IBV_WC_WR_FLUSH_ERR (ib_read). Ignore it.");
			else if (wc[j].status != IBV_WC_SUCCESS)
				n->logger->warn("Work Completion status was not IBV_WC_SUCCESS: {}",
					wc[j].status);

			/* 32 byte of meta data is always transferred. We should substract it.
			 * Furthermore, in case of an unreliable connection, a 40 byte
			 * global routing header is transferred. This should be substracted as well.
			 */
			int correction = (ib->conn.port_space == RDMA_PS_UDP) ? META_GRH_SIZE : META_SIZE;

			// TODO: fix release logic
			// smps[j] = (struct Sample *) (wc[j].wr_id);

			smps[j]->length = SAMPLE_NUMBER_OF_VALUES(wc[j].byte_len - correction);
			smps[j]->ts.received = ts_receive;
			smps[j]->flags = (int) SampleFlags::HAS_TS_ORIGIN | (int) SampleFlags::HAS_TS_RECEIVED | (int) SampleFlags::HAS_SEQUENCE;
			smps[j]->signals = n->getInputSignals(false);
		}

	}
	return read_values;
}

int villas::node::ib_write(NodeCompat *n, struct Sample * const smps[], unsigned cnt)
{
	auto *ib = n->getData<struct infiniband>();
	struct ibv_send_wr wr[cnt], *bad_wr = nullptr;
	struct ibv_sge sge[cnt][ib->qp_init.cap.max_recv_sge];
	struct ibv_wc wc[cnt];
	struct ibv_mr *mr;

	int ret;
	unsigned sent = 0; /* Used for first loop: prepare work requests to post to send queue */

	n->logger->debug("ib_write is called");

	if (n->getState() == State::CONNECTED) {
		// TODO: fix release logic
		// *release = 0;

		/* First, write */

		/* Get Memory Region */
		mr = memory::ib_get_mr(pool_buffer(sample_pool(smps[0])));

		for (sent = 0; sent < cnt; sent++) {
			int j = 0;

			/* Set Scatter/Gather element to data of sample */

			/* Sequence */
			sge[sent][j].addr = (uint64_t) &smps[sent]->sequence;
			sge[sent][j].length = sizeof(smps[sent]->sequence);
			sge[sent][j].lkey = mr->lkey;

			j++;

			/* Timespec origin */
			sge[sent][j].addr = (uint64_t) &smps[sent]->ts.origin;
			sge[sent][j].length = sizeof(smps[sent]->ts.origin);
			sge[sent][j].lkey = mr->lkey;

			j++;

			/* Actual Payload */
			sge[sent][j].addr = (uint64_t) &smps[sent]->data;
			sge[sent][j].length = SAMPLE_DATA_LENGTH(smps[sent]->length);
			sge[sent][j].lkey = mr->lkey;

			j++;

			/* Check if connection is connected or unconnected and set appropriate values */
			if (ib->conn.port_space == RDMA_PS_UDP) {
				wr[sent].wr.ud.ah = ib->conn.ud.ah;
				wr[sent].wr.ud.remote_qkey = ib->conn.ud.ud.qkey;
				wr[sent].wr.ud.remote_qpn = ib->conn.ud.ud.qp_num;
			}

			/* Check if data can be send inline
			 * 32 byte meta data is always send.
			 * Once every max_send_wr iterations a signal must be generated. Since we would need
			 * an additional buffer if we were sending inlines with IBV_SEND_SIGNALED, we prefer
			 * to send one samples every max_send_wr NOT inline (which thus generates a signal).
			 */
			int send_inline = ((sge[sent][j-1].length + META_SIZE) < ib->qp_init.cap.max_inline_data)
				&& ((++ib->signaling_counter % ib->periodic_signaling) != 0)  ?
				ib->conn.send_inline : 0;

			n->logger->debug("Sample will be send inline [0/1]: {}", send_inline);

			/* Set Send Work Request */
			wr[sent].wr_id = (uintptr_t) smps[sent];
			wr[sent].sg_list = sge[sent];
			wr[sent].num_sge = j;
			wr[sent].next = &wr[sent+1];

			wr[sent].send_flags = send_inline ? IBV_SEND_INLINE : IBV_SEND_SIGNALED;
			wr[sent].opcode = IBV_WR_SEND;
		}

		n->logger->debug("Prepared {} send Work Requests", cnt);
		wr[cnt-1].next = nullptr;

		/* Send linked list of Work Requests */
		ret = ibv_post_send(ib->ctx.id->qp, wr, &bad_wr);
		n->logger->debug("Posted send Work Requests");

		/* Reorder list. Place inline and unposted samples to the top
		 * m will always be equal or smaller than *release
		 */
		for (unsigned m = 0; m < cnt; m++) {
			/* We can't use wr_id as identifier, since it is 0 for inline
			 * elements
			 */
			if (ret && (wr[m].sg_list == bad_wr->sg_list)) {
				/* The remaining work requests will be bad. Ripple through list
				 * and prepare them to be released
				 */
				n->logger->debug("Bad WR occured with ID: {:#x} and S/G address: {:#x}: {}",
					bad_wr->wr_id, (void *) bad_wr->sg_list, ret);

				while (1) {
					// TODO: fix release logic
					// smps[*release] = smps[m];
					// (*release)++; /* Increment number of samples to be released */
					sent--; /* Decrement the number of successfully posted elements */

					if (++m == cnt) break;
				}
			}
			else if (wr[m].send_flags & IBV_SEND_INLINE) {
				// TODO: fix release logic
				// smps[*release] = smps[m];
				// (*release)++;
			}
		}

		// TODO: fix release logic
		// n->logger->debug("{} samples will be released (before WC)", *release);

		/* Try to grab as many CQEs from CQ as there is space in *smps[] */
		// ret = ibv_poll_cq(ib->ctx.send_cq, cnt - *release, wc);

		for (int i = 0; i < ret; i++) {
			if (wc[i].status != IBV_WC_SUCCESS && wc[i].status != IBV_WC_WR_FLUSH_ERR)
				n->logger->warn("Work Completion status was not IBV_WC_SUCCESS: {}",
					wc[i].status);

			// TODO: fix release logic
			// smps[*release] = (struct Sample *) (wc[i].wr_id);
			// (*release)++;
		}

		// TODO: fix release logic
		// n->logger->debug("{} samples will be released (after WC)", *release);
	}

	return sent;
}

static NodeCompatType p;

__attribute__((constructor(110)))
static void register_plugin() {
	p.name		= "infiniband";
	p.description	= "Infiniband interface (libibverbs, librdmacm)";
	p.vectorize	= 0;
	p.size		= sizeof(struct infiniband);
	// TODO: fix
	// p.pool_size	= 8192;
	p.destroy	= ib_destroy;
	p.parse		= ib_parse;
	p.check		= ib_check;
	p.print		= ib_print;
	p.start		= ib_start;
	p.stop		= ib_stop;
	p.read		= ib_read;
	p.write		= ib_write;
	p.reverse	= ib_reverse;
	p.memory_type	= memory::ib;

	static NodeCompatFactory ncp(&p);
}