/**
 * collectd - src/ntpd.c
 * Copyright (C) 2006-2012  Florian octo Forster
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; only version 2 of the License is applicable.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * Authors:
 *   Florian octo Forster <octo at collectd.org>
 **/

#define _BSD_SOURCE /* For NI_MAXHOST */

#include "collectd.h"
#include "common.h"
#include "plugin.h"
#include "configfile.h"

#if HAVE_STDINT_H
# include <stdint.h>
#endif
#if HAVE_NETDB_H
# include <netdb.h>
#endif
#if HAVE_SYS_SOCKET_H
# include <sys/socket.h>
#endif
#if HAVE_NETINET_IN_H
# include <netinet/in.h>
#endif
#if HAVE_ARPA_INET_H
# include <arpa/inet.h> /* inet_ntoa */
#endif
#if HAVE_NETINET_TCP_H
# include <netinet/tcp.h>
#endif
#if HAVE_POLL_H
# include <poll.h>
#endif

static const char *config_keys[] =
{
	"Host",
	"Port",
	"ReverseLookups",
	"IncludeUnitID"
};
static int config_keys_num = STATIC_ARRAY_SIZE (config_keys);

static _Bool do_reverse_lookups = 1;

/* This option only exists for backward compatibility. If it is false and two
 * ntpd peers use the same refclock driver, the plugin will try to write
 * simultaneous measurements from both to the same type instance. */
static _Bool include_unit_id = 0;

# define NTPD_DEFAULT_HOST "localhost"
# define NTPD_DEFAULT_PORT "123"
static int   sock_descr = -1;
static char *ntpd_host = NULL;
static char  ntpd_port[16];

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * The following definitions were copied from the NTPd distribution  *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#define MAXFILENAME 128
#define MAXSEQ  127
#define MODE_PRIVATE 7
#define NTP_OLDVERSION ((uint8_t) 1) /* oldest credible version */
#define IMPL_XNTPD 3
#define FP_FRAC 65536.0

#define REFCLOCK_ADDR 0x7f7f0000 /* 127.127.0.0 */
#define REFCLOCK_MASK 0xffff0000 /* 255.255.0.0 */

/* This structure is missing the message authentication code, since collectd
 * doesn't use it. */
struct req_pkt
{
	uint8_t  rm_vn_mode;
	uint8_t  auth_seq;
	uint8_t  implementation;		/* implementation number */
	uint8_t  request;			/* request number */
	uint16_t err_nitems;		/* error code/number of data items */
	uint16_t mbz_itemsize;		/* item size */
	char     data[MAXFILENAME + 48];	/* data area [32 prev](176 byte max) */
					/* struct conf_peer must fit */
};
#define REQ_LEN_NOMAC (sizeof(struct req_pkt))

/*
 * A response packet.  The length here is variable, this is a
 * maximally sized one.  Note that this implementation doesn't
 * authenticate responses.
 */
#define	RESP_HEADER_SIZE	(8)
#define	RESP_DATA_SIZE		(500)

struct resp_pkt
{
	uint8_t  rm_vn_mode;           /* response, more, version, mode */
	uint8_t  auth_seq;             /* key, sequence number */
	uint8_t  implementation;       /* implementation number */
	uint8_t  request;              /* request number */
	uint16_t err_nitems;           /* error code/number of data items */
	uint16_t mbz_itemsize;         /* item size */
	char     data[RESP_DATA_SIZE]; /* data area */
};

/*
 * Bit setting macros for multifield items.
 */
#define	RESP_BIT	0x80
#define	MORE_BIT	0x40

#define	ISRESPONSE(rm_vn_mode)	(((rm_vn_mode)&RESP_BIT)!=0)
#define	ISMORE(rm_vn_mode)	(((rm_vn_mode)&MORE_BIT)!=0)
#define INFO_VERSION(rm_vn_mode) ((uint8_t)(((rm_vn_mode)>>3)&0x7))
#define	INFO_MODE(rm_vn_mode)	((rm_vn_mode)&0x7)

#define	RM_VN_MODE(resp, more, version)		\
				((uint8_t)(((resp)?RESP_BIT:0)\
				|((more)?MORE_BIT:0)\
				|((version?version:(NTP_OLDVERSION+1))<<3)\
				|(MODE_PRIVATE)))

#define	INFO_IS_AUTH(auth_seq)	(((auth_seq) & 0x80) != 0)
#define	INFO_SEQ(auth_seq)	((auth_seq)&0x7f)
#define	AUTH_SEQ(auth, seq)	((uint8_t)((((auth)!=0)?0x80:0)|((seq)&0x7f)))

#define	INFO_ERR(err_nitems)	((uint16_t)((ntohs(err_nitems)>>12)&0xf))
#define	INFO_NITEMS(err_nitems)	((uint16_t)(ntohs(err_nitems)&0xfff))
#define	ERR_NITEMS(err, nitems)	(htons((uint16_t)((((uint16_t)(err)<<12)&0xf000)\
				|((uint16_t)(nitems)&0xfff))))

#define	INFO_MBZ(mbz_itemsize)	((ntohs(mbz_itemsize)>>12)&0xf)
#define	INFO_ITEMSIZE(mbz_itemsize)	((uint16_t)(ntohs(mbz_itemsize)&0xfff))
#define	MBZ_ITEMSIZE(itemsize)	(htons((uint16_t)(itemsize)))

/* negate a long float type */
#define M_NEG(v_i, v_f) \
	do { \
		if ((v_f) == 0) \
		(v_i) = -((uint32_t)(v_i)); \
		else { \
			(v_f) = -((uint32_t)(v_f)); \
			(v_i) = ~(v_i); \
		} \
	} while(0)
/* l_fp to double */
#define M_LFPTOD(r_i, r_uf, d) \
	do { \
		register int32_t  i; \
		register uint32_t f; \
		\
		i = (r_i); \
		f = (r_uf); \
		if (i < 0) { \
			M_NEG(i, f); \
			(d) = -((double) i + ((double) f) / 4294967296.0); \
		} else { \
			(d) = (double) i + ((double) f) / 4294967296.0; \
		} \
	} while (0)

#define REQ_PEER_LIST_SUM 1
struct info_peer_summary
{
	uint32_t dstadr;         /* local address (zero for undetermined) */
	uint32_t srcadr;         /* source address */
	uint16_t srcport;        /* source port */
	uint8_t stratum;         /* stratum of peer */
	int8_t hpoll;            /* host polling interval */
	int8_t ppoll;            /* peer polling interval */
	uint8_t reach;           /* reachability register */
	uint8_t flags;           /* flags, from above */
	uint8_t hmode;           /* peer mode */
	int32_t  delay;          /* peer.estdelay; s_fp */
	int32_t  offset_int;     /* peer.estoffset; integral part */
	int32_t  offset_frc;     /* peer.estoffset; fractional part */
	uint32_t dispersion;     /* peer.estdisp; u_fp */
	uint32_t v6_flag;        /* is this v6 or not */
	uint32_t unused1;        /* (unused) padding for dstadr6 */
	struct in6_addr dstadr6; /* local address (v6) */
	struct in6_addr srcadr6; /* source address (v6) */
};

#define REQ_SYS_INFO 4
struct info_sys
{
	uint32_t peer;           /* system peer address (v4) */
	uint8_t  peer_mode;      /* mode we are syncing to peer in */
	uint8_t  leap;           /* system leap bits */
	uint8_t  stratum;        /* our stratum */
	int8_t   precision;      /* local clock precision */
	int32_t  rootdelay;      /* distance from sync source */
	uint32_t rootdispersion; /* dispersion from sync source */
	uint32_t refid;          /* reference ID of sync source */
	uint64_t reftime;        /* system reference time */
	uint32_t poll;           /* system poll interval */
	uint8_t  flags;          /* system flags */
	uint8_t  unused1;        /* unused */
	uint8_t  unused2;        /* unused */
	uint8_t  unused3;        /* unused */
	int32_t  bdelay;         /* default broadcast offset */
	int32_t  frequency;      /* frequency residual (scaled ppm)  */
	uint64_t authdelay;      /* default authentication delay */
	uint32_t stability;      /* clock stability (scaled ppm) */
	int32_t  v6_flag;        /* is this v6 or not */
	int32_t  unused4;        /* unused, padding for peer6 */
	struct in6_addr peer6;   /* system peer address (v6) */
};

#define REQ_GET_KERNEL 38
struct info_kernel
{
	int32_t  offset;
	int32_t  freq;
	int32_t  maxerror;
	int32_t  esterror;
	uint16_t status;
	uint16_t shift;
	int32_t  constant;
	int32_t  precision;
	int32_t  tolerance;
	/* pps stuff */
	int32_t  ppsfreq;
	int32_t  jitter;
	int32_t  stabil;
	int32_t  jitcnt;
	int32_t  calcnt;
	int32_t  errcnt;
	int32_t  stbcnt;
};

/* List of reference clock names */
static char *refclock_names[] =
{
	"UNKNOWN",    "LOCAL",        "GPS_TRAK",   "WWV_PST",     /*  0- 3 */
	"SPECTRACOM", "TRUETIME",     "IRIG_AUDIO", "CHU_AUDIO",   /*  4- 7 */
	"GENERIC",    "GPS_MX4200",   "GPS_AS2201", "GPS_ARBITER", /*  8-11 */
	"IRIG_TPRO",  "ATOM_LEITCH",  "MSF_EES",    "GPSTM_TRUE",  /* 12-15 */
	"GPS_BANC",   "GPS_DATUM",    "ACTS_NIST",  "WWV_HEATH",   /* 16-19 */
	"GPS_NMEA",   "GPS_VME",      "PPS",        "ACTS_PTB",    /* 20-23 */
	"ACTS_USNO",  "TRUETIME",     "GPS_HP",     "MSF_ARCRON",  /* 24-27 */
	"SHM",        "GPS_PALISADE", "GPS_ONCORE", "GPS_JUPITER", /* 28-31 */
	"CHRONOLOG",  "DUMBCLOCK",    "ULINK_M320", "PCF",         /* 32-35 */
	"WWV_AUDIO",  "GPS_FG",       "HOPF_S",     "HOPF_P",      /* 36-39 */
	"JJY",        "TT_IRIG",      "GPS_ZYFER",  "GPS_RIPENCC", /* 40-43 */
	"NEOCLK4X"                                                 /* 44    */
};
static int refclock_names_num = STATIC_ARRAY_SIZE (refclock_names);
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * End of the copied stuff..                                         *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

static int ntpd_config (const char *key, const char *value)
{
	if (strcasecmp (key, "Host") == 0)
	{
		if (ntpd_host != NULL)
			free (ntpd_host);
		if ((ntpd_host = strdup (value)) == NULL)
			return (1);
	}
	else if (strcasecmp (key, "Port") == 0)
	{
		int port = (int) (atof (value));
		if ((port > 0) && (port <= 65535))
			ssnprintf (ntpd_port, sizeof (ntpd_port),
					"%i", port);
		else
			sstrncpy (ntpd_port, value, sizeof (ntpd_port));
	}
	else if (strcasecmp (key, "ReverseLookups") == 0)
	{
		if (IS_TRUE (value))
			do_reverse_lookups = 1;
		else
			do_reverse_lookups = 0;
	}
	else if (strcasecmp (key, "IncludeUnitID") == 0)
	{
		if (IS_TRUE (value))
			include_unit_id = 1;
		else
			include_unit_id = 0;
	}
	else
	{
		return (-1);
	}

	return (0);
}

static void ntpd_submit (char *type, char *type_inst, double value)
{
	value_t values[1];
	value_list_t vl = VALUE_LIST_INIT;

	values[0].gauge = value;

	vl.values = values;
	vl.values_len = 1;
	sstrncpy (vl.host, hostname_g, sizeof (vl.host));
	sstrncpy (vl.plugin, "ntpd", sizeof (vl.plugin));
	sstrncpy (vl.plugin_instance, "", sizeof (vl.plugin_instance));
	sstrncpy (vl.type, type, sizeof (vl.type));
	sstrncpy (vl.type_instance, type_inst, sizeof (vl.type_instance));

	plugin_dispatch_values (&vl);
}

/* Each time a peer is polled, ntpd shifts the reach register to the left and
 * sets the LSB based on whether the peer was reachable. If the LSB is zero,
 * the values are out of date. */
static void ntpd_submit_reach (char *type, char *type_inst, uint8_t reach,
		double value)
{
	if (!(reach & 1))
		value = NAN;

	ntpd_submit (type, type_inst, value);
}

static int ntpd_connect (void)
{
	char *host;
	char *port;

	struct addrinfo  ai_hints;
	struct addrinfo *ai_list;
	struct addrinfo *ai_ptr;
	int              status;

	if (sock_descr >= 0)
		return (sock_descr);

	DEBUG ("Opening a new socket");

	host = ntpd_host;
	if (host == NULL)
		host = NTPD_DEFAULT_HOST;

	port = ntpd_port;
	if (strlen (port) == 0)
		port = NTPD_DEFAULT_PORT;

	memset (&ai_hints, '\0', sizeof (ai_hints));
	ai_hints.ai_flags    = 0;
#ifdef AI_ADDRCONFIG
	ai_hints.ai_flags   |= AI_ADDRCONFIG;
#endif
	ai_hints.ai_family   = PF_UNSPEC;
	ai_hints.ai_socktype = SOCK_DGRAM;
	ai_hints.ai_protocol = IPPROTO_UDP;

	if ((status = getaddrinfo (host, port, &ai_hints, &ai_list)) != 0)
	{
		char errbuf[1024];
		ERROR ("ntpd plugin: getaddrinfo (%s, %s): %s",
				host, port,
				(status == EAI_SYSTEM)
				? sstrerror (errno, errbuf, sizeof (errbuf))
				: gai_strerror (status));
		return (-1);
	}

	for (ai_ptr = ai_list; ai_ptr != NULL; ai_ptr = ai_ptr->ai_next)
	{
		/* create our socket descriptor */
		if ((sock_descr = socket (ai_ptr->ai_family,
						ai_ptr->ai_socktype,
						ai_ptr->ai_protocol)) < 0)
			continue;

		/* connect to the ntpd */
		if (connect (sock_descr, ai_ptr->ai_addr, ai_ptr->ai_addrlen))
		{
			close (sock_descr);
			sock_descr = -1;
			continue;
		}

		break;
	}

	freeaddrinfo (ai_list);

	if (sock_descr < 0)
	{
		ERROR ("ntpd plugin: Unable to connect to server.");
	}

	return (sock_descr);
}

/* For a description of the arguments see `ntpd_do_query' below. */
static int ntpd_receive_response (int *res_items, int *res_size,
		char **res_data, int res_item_size)
{
	int              sd;
	struct pollfd    poll_s;
	struct resp_pkt  res;
	int              status;
	int              done;
	int              i;

	char            *items;
	size_t           items_num;

	struct timeval   time_end;
	struct timeval   time_now;
	int              timeout;

	int              pkt_item_num;        /* items in this packet */
	int              pkt_item_len;        /* size of the items in this packet */
	int              pkt_sequence;
	char             pkt_recvd[MAXSEQ+1]; /* sequence numbers that have been received */
	int              pkt_recvd_num;       /* number of packets that have been received */
	int              pkt_lastseq;         /* the last sequence number */
	ssize_t          pkt_padding;         /* Padding in this packet */

	if ((sd = ntpd_connect ()) < 0)
		return (-1);

	items = NULL;
	items_num = 0;

	memset (pkt_recvd, '\0', sizeof (pkt_recvd));
	pkt_recvd_num = 0;
	pkt_lastseq   = -1;

	*res_items = 0;
	*res_size  = 0;
	*res_data  = NULL;

	if (gettimeofday (&time_end, NULL) < 0)
	{
		char errbuf[1024];
		ERROR ("ntpd plugin: gettimeofday failed: %s",
				sstrerror (errno, errbuf, sizeof (errbuf)));
		return (-1);
	}
	time_end.tv_sec++; /* wait for a most one second */

	done = 0;
	while (done == 0)
	{
		struct timeval time_left;

		if (gettimeofday (&time_now, NULL) < 0)
		{
			char errbuf[1024];
			ERROR ("ntpd plugin: gettimeofday failed: %s",
					sstrerror (errno, errbuf, sizeof (errbuf)));
			return (-1);
		}

		if (timeval_cmp (time_end, time_now, &time_left) <= 0)
			timeout = 0;
		else
			timeout = 1000 * time_left.tv_sec
				+ ((time_left.tv_usec + 500) / 1000);

		/* timeout reached */
		if (timeout <= 0)
			break;

		poll_s.fd      = sd;
		poll_s.events  = POLLIN | POLLPRI;
		poll_s.revents = 0;
		
		DEBUG ("Polling for %ims", timeout);
		status = poll (&poll_s, 1, timeout);

		if ((status < 0) && ((errno == EAGAIN) || (errno == EINTR)))
			continue;

		if (status < 0)
		{
			char errbuf[1024];
			ERROR ("ntpd plugin: poll failed: %s",
					sstrerror (errno, errbuf, sizeof (errbuf)));
			return (-1);
		}

		if (status == 0) /* timeout */
		{
			DEBUG ("timeout reached.");
			break;
		}

		memset ((void *) &res, '\0', sizeof (res));
		status = recv (sd, (void *) &res, sizeof (res), 0 /* no flags */);

		if ((status < 0) && ((errno == EAGAIN) || (errno == EINTR)))
			continue;

		if (status < 0)
		{
			char errbuf[1024];
			INFO ("recv(2) failed: %s",
					sstrerror (errno, errbuf, sizeof (errbuf)));
			DEBUG ("Closing socket #%i", sd);
			close (sd);
			sock_descr = sd = -1;
			return (-1);
		}

		DEBUG ("recv'd %i bytes", status);

		/* 
		 * Do some sanity checks first
		 */
		if (status < RESP_HEADER_SIZE)
		{
			WARNING ("ntpd plugin: Short (%i bytes) packet received",
					(int) status);
			continue;
		}
		if (INFO_MODE (res.rm_vn_mode) != MODE_PRIVATE)
		{
			NOTICE ("ntpd plugin: Packet received with mode %i",
					INFO_MODE (res.rm_vn_mode));
			continue;
		}
		if (INFO_IS_AUTH (res.auth_seq))
		{
			NOTICE ("ntpd plugin: Encrypted packet received");
			continue;
		}
		if (!ISRESPONSE (res.rm_vn_mode))
		{
			NOTICE ("ntpd plugin: Received request packet, "
					"wanted response");
			continue;
		}
		if (INFO_MBZ (res.mbz_itemsize))
		{
			WARNING ("ntpd plugin: Received packet with nonzero "
					"MBZ field!");
			continue;
		}
		if (res.implementation != IMPL_XNTPD)
		{
			WARNING ("ntpd plugin: Asked for request of type %i, "
					"got %i", (int) IMPL_XNTPD, (int) res.implementation);
			continue;
		}

		/* Check for error code */
		if (INFO_ERR (res.err_nitems) != 0)
		{
			ERROR ("ntpd plugin: Received error code %i",
					(int) INFO_ERR(res.err_nitems));
			return ((int) INFO_ERR (res.err_nitems));
		}

		/* extract number of items in this packet and the size of these items */
		pkt_item_num = INFO_NITEMS (res.err_nitems);
		pkt_item_len = INFO_ITEMSIZE (res.mbz_itemsize);
		DEBUG ("pkt_item_num = %i; pkt_item_len = %i;",
				pkt_item_num, pkt_item_len);

		/* Check if the reported items fit in the packet */
		if ((pkt_item_num * pkt_item_len) > (status - RESP_HEADER_SIZE))
		{
			ERROR ("ntpd plugin: %i items * %i bytes > "
					"%i bytes - %i bytes header",
					(int) pkt_item_num, (int) pkt_item_len,
					(int) status, (int) RESP_HEADER_SIZE);
			continue;
		}

		if (pkt_item_len > res_item_size)
		{
			ERROR ("ntpd plugin: (pkt_item_len = %i) "
					">= (res_item_size = %i)",
					pkt_item_len, res_item_size);
			continue;
		}

		/* If this is the first packet (time wise, not sequence wise),
		 * set `res_size'. If it's not the first packet check if the
		 * items have the same size. Discard invalid packets. */
		if (items_num == 0) /* first packet */
		{
			DEBUG ("*res_size = %i", pkt_item_len);
			*res_size = pkt_item_len;
		}
		else if (*res_size != pkt_item_len)
		{
			DEBUG ("Error: *res_size = %i; pkt_item_len = %i;",
					*res_size, pkt_item_len);
			ERROR ("Item sizes differ.");
			continue;
		}

		/*
		 * Because the items in the packet may be smaller than the
		 * items requested, the following holds true:
		 */
		assert ((*res_size == pkt_item_len)
				&& (pkt_item_len <= res_item_size));

		/* Calculate the padding. No idea why there might be any padding.. */
		pkt_padding = 0;
		if (pkt_item_len < res_item_size)
			pkt_padding = res_item_size - pkt_item_len;
		DEBUG ("res_item_size = %i; pkt_padding = %zi;",
				res_item_size, pkt_padding);

		/* Extract the sequence number */
		pkt_sequence = INFO_SEQ (res.auth_seq);
		if ((pkt_sequence < 0) || (pkt_sequence > MAXSEQ))
		{
			ERROR ("ntpd plugin: Received packet with sequence %i",
					pkt_sequence);
			continue;
		}

		/* Check if this sequence has been received before. If so, discard it. */
		if (pkt_recvd[pkt_sequence] != '\0')
		{
			NOTICE ("ntpd plugin: Sequence %i received twice",
					pkt_sequence);
			continue;
		}

		/* If `pkt_lastseq != -1' another packet without `more bit' has
		 * been received. */
		if (!ISMORE (res.rm_vn_mode))
		{
			if (pkt_lastseq != -1)
			{
				ERROR ("ntpd plugin: Two packets which both "
						"claim to be the last one in the "
						"sequence have been received.");
				continue;
			}
			pkt_lastseq = pkt_sequence;
			DEBUG ("Last sequence = %i;", pkt_lastseq);
		}

		/*
		 * Enough with the checks. Copy the data now.
		 * We start by allocating some more memory.
		 */
		DEBUG ("realloc (%p, %zu)", (void *) *res_data,
				(items_num + pkt_item_num) * res_item_size);
		items = realloc ((void *) *res_data,
				(items_num + pkt_item_num) * res_item_size);
		if (items == NULL)
		{
			items = *res_data;
			ERROR ("ntpd plugin: realloc failed.");
			continue;
		}
		items_num += pkt_item_num;
		*res_data = items;

		for (i = 0; i < pkt_item_num; i++)
		{
			/* dst: There are already `*res_items' items with
			 *      res_item_size bytes each in in `*res_data'. Set
			 *      dst to the first byte after that. */
			void *dst = (void *) (*res_data + ((*res_items) * res_item_size));
			/* src: We use `pkt_item_len' to calculate the offset
			 *      from the beginning of the packet, because the
			 *      items in the packet may be smaller than the
			 *      items that were requested. We skip `i' such
			 *      items. */
			void *src = (void *) (((char *) res.data) + (i * pkt_item_len));

			/* Set the padding to zeros */
			if (pkt_padding != 0)
				memset (dst, '\0', res_item_size);
			memcpy (dst, src, (size_t) pkt_item_len);

			/* Increment `*res_items' by one, so `dst' will end up
			 * one further in the next round. */
			(*res_items)++;
		} /* for (pkt_item_num) */

		pkt_recvd[pkt_sequence] = (char) 1;
		pkt_recvd_num++;

		if ((pkt_recvd_num - 1) == pkt_lastseq)
			done = 1;
	} /* while (done == 0) */

	return (0);
} /* int ntpd_receive_response */

/* For a description of the arguments see `ntpd_do_query' below. */
static int ntpd_send_request (int req_code, int req_items, int req_size, char *req_data)
{
	int             sd;
	struct req_pkt  req;
	size_t          req_data_len;
	int             status;

	assert (req_items >= 0);
	assert (req_size  >= 0);

	if ((sd = ntpd_connect ()) < 0)
		return (-1);

	memset ((void *) &req, '\0', sizeof (req));
	req.rm_vn_mode = RM_VN_MODE(0, 0, 0);
	req.auth_seq   = AUTH_SEQ (0, 0);
	req.implementation = IMPL_XNTPD;
	req.request = (unsigned char) req_code;

	req_data_len = (size_t) (req_items * req_size);

	assert (((req_data != NULL) && (req_data_len > 0))
			|| ((req_data == NULL) && (req_items == 0) && (req_size == 0)));

	req.err_nitems   = ERR_NITEMS (0, req_items);
	req.mbz_itemsize = MBZ_ITEMSIZE (req_size);
	
	if (req_data != NULL)
		memcpy ((void *) req.data, (const void *) req_data, req_data_len);

	DEBUG ("req_items = %i; req_size = %i; req_data = %p;",
			req_items, req_size, (void *) req_data);

	status = swrite (sd, (const char *) &req, REQ_LEN_NOMAC);
	if (status < 0)
	{
		DEBUG ("`swrite' failed. Closing socket #%i", sd);
		close (sd);
		sock_descr = sd = -1;
		return (status);
	}

	return (0);
}

/*
 * ntpd_do_query:
 *
 * req_code:      Type of request packet
 * req_items:     Numver of items in the request
 * req_size:      Size of one item in the request
 * req_data:      Data of the request packet
 * res_items:     Pointer to where the number returned items will be stored.
 * res_size:      Pointer to where the size of one returned item will be stored.
 * res_data:      This is where a pointer to the (allocated) data will be stored.
 * res_item_size: Size of one returned item. (used to calculate padding)
 *
 * returns:       zero upon success, non-zero otherwise.
 */
static int ntpd_do_query (int req_code, int req_items, int req_size, char *req_data,
		int *res_items, int *res_size, char **res_data, int res_item_size)
{
	int status;

	status = ntpd_send_request (req_code, req_items, req_size, req_data);
	if (status != 0)
		return (status);

	status = ntpd_receive_response (res_items, res_size, res_data,
			res_item_size);
	return (status);
}

static double ntpd_read_fp (int32_t val_int)
{
	double val_double;

	val_int = ntohl (val_int);
	val_double = ((double) val_int) / FP_FRAC;

	return (val_double);
}

static uint32_t ntpd_get_refclock_id (struct info_peer_summary const *peer_info)
{
	uint32_t addr = ntohl (peer_info->srcadr);
	uint32_t refclock_id = (addr >> 8) & 0x00FF;

	return (refclock_id);
}

static int ntpd_get_name_from_address (char *buffer, size_t buffer_size,
		struct info_peer_summary const *peer_info, _Bool do_reverse_lookup)
{
	struct sockaddr_storage sa;
	socklen_t sa_len;
	int flags = 0;
	int status;

	memset (&sa, 0, sizeof (sa));

	if (peer_info->v6_flag)
	{
		struct sockaddr_in6 sa6;

		assert (sizeof (sa) >= sizeof (sa6));

		memset (&sa6, 0, sizeof (sa6));
		sa6.sin6_family = AF_INET6;
		sa6.sin6_port = htons (123);
		memcpy (&sa6.sin6_addr, &peer_info->srcadr6,
				sizeof (struct in6_addr));
		sa_len = sizeof (sa6);

		memcpy (&sa, &sa6, sizeof (sa6));
	}
	else
	{
		struct sockaddr_in sa4;

		assert (sizeof (sa) >= sizeof (sa4));

		memset (&sa4, 0, sizeof (sa4));
		sa4.sin_family = AF_INET;
		sa4.sin_port = htons (123);
		memcpy (&sa4.sin_addr, &peer_info->srcadr,
				sizeof (struct in_addr));
		sa_len = sizeof (sa4);

		memcpy (&sa, &sa4, sizeof (sa4));
	}

	if (!do_reverse_lookup)
		flags |= NI_NUMERICHOST;

	status = getnameinfo ((struct sockaddr const *) &sa, sa_len,
			buffer, buffer_size,
			NULL, 0, /* No port name */
			flags);
	if (status != 0)
	{
		char errbuf[1024];
		ERROR ("ntpd plugin: getnameinfo failed: %s",
				(status == EAI_SYSTEM)
				? sstrerror (errno, errbuf, sizeof (errbuf))
				: gai_strerror (status));
		return (-1);
	}

	return (0);
} /* ntpd_get_name_from_address */

static int ntpd_get_name_refclock (char *buffer, size_t buffer_size,
		struct info_peer_summary const *peer_info)
{
	uint32_t refclock_id = ntpd_get_refclock_id (peer_info);
	uint32_t unit_id = ntohl (peer_info->srcadr) & 0x00FF;

	if (refclock_id >= refclock_names_num)
		return (ntpd_get_name_from_address (buffer, buffer_size,
					peer_info,
					/* do_reverse_lookup = */ 0));

	if (include_unit_id)
		ssnprintf (buffer, buffer_size, "%s-%"PRIu32,
				refclock_names[refclock_id], unit_id);
	else
		sstrncpy (buffer, refclock_names[refclock_id], buffer_size);

	return (0);
} /* int ntpd_get_name_refclock */

static int ntpd_get_name (char *buffer, size_t buffer_size,
		struct info_peer_summary const *peer_info)
{
	uint32_t addr = ntohl (peer_info->srcadr);

	if (!peer_info->v6_flag && ((addr & REFCLOCK_MASK) == REFCLOCK_ADDR))
		return (ntpd_get_name_refclock (buffer, buffer_size,
					peer_info));
	else
		return (ntpd_get_name_from_address (buffer, buffer_size,
					peer_info, do_reverse_lookups));
} /* int ntpd_addr_to_name */

static int ntpd_read (void)
{
	struct info_kernel *ik;
	int                 ik_num;
	int                 ik_size;

	struct info_peer_summary *ps;
	int                       ps_num;
	int                       ps_size;

	int status;
	int i;

	ik      = NULL;
	ik_num  = 0;
	ik_size = 0;

	status = ntpd_do_query (REQ_GET_KERNEL,
			0, 0, NULL, /* request data */
			&ik_num, &ik_size, (char **) ((void *) &ik), /* response data */
			sizeof (struct info_kernel));
	if (status != 0)
	{
		ERROR ("ntpd plugin: ntpd_do_query (REQ_GET_KERNEL) failed with status %i", status);
		return (status);
	}
	else if ((ik == NULL) || (ik_num == 0) || (ik_size == 0))
	{
		ERROR ("ntpd plugin: ntpd_do_query returned unexpected data. "
				"(ik = %p; ik_num = %i; ik_size = %i)",
				(void *) ik, ik_num, ik_size);
		return (-1);
	}

	/* kerninfo -> estimated error */

	DEBUG ("info_kernel:\n"
			"  pll offset    = %.8f\n"
			"  pll frequency = %.8f\n" /* drift compensation */
			"  est error     = %.8f\n",
			ntpd_read_fp (ik->offset),
			ntpd_read_fp (ik->freq),
			ntpd_read_fp (ik->esterror));

	ntpd_submit ("frequency_offset", "loop",  ntpd_read_fp (ik->freq));
	ntpd_submit ("time_offset",      "loop",  ntpd_read_fp (ik->offset));
	ntpd_submit ("time_offset",      "error", ntpd_read_fp (ik->esterror));

	free (ik);
	ik = NULL;

	status = ntpd_do_query (REQ_PEER_LIST_SUM,
			0, 0, NULL, /* request data */
			&ps_num, &ps_size, (char **) ((void *) &ps), /* response data */
			sizeof (struct info_peer_summary));
	if (status != 0)
	{
		ERROR ("ntpd plugin: ntpd_do_query (REQ_PEER_LIST_SUM) failed with status %i", status);
		return (status);
	}
	else if ((ps == NULL) || (ps_num == 0) || (ps_size == 0))
	{
		ERROR ("ntpd plugin: ntpd_do_query returned unexpected data. "
				"(ps = %p; ps_num = %i; ps_size = %i)",
				(void *) ps, ps_num, ps_size);
		return (-1);
	}

	for (i = 0; i < ps_num; i++)
	{
		struct info_peer_summary *ptr;
		double offset;

		char peername[NI_MAXHOST];
		uint32_t refclock_id;

		ptr = ps + i;

		status = ntpd_get_name (peername, sizeof (peername), ptr);
		if (status != 0)
		{
			ERROR ("ntpd plugin: Determining name of peer failed.");
			continue;
		}

		refclock_id = ntpd_get_refclock_id (ptr);

		/* Convert the `long floating point' offset value to double */
		M_LFPTOD (ntohl (ptr->offset_int), ntohl (ptr->offset_frc), offset);

		DEBUG ("peer %i:\n"
				"  peername   = %s\n"
				"  srcadr     = 0x%08x\n"
				"  reach      = 0%03o\n"
				"  delay      = %f\n"
				"  offset_int = %i\n"
				"  offset_frc = %i\n"
				"  offset     = %f\n"
				"  dispersion = %f\n",
				i,
				peername,
				ntohl (ptr->srcadr),
				ptr->reach,
				ntpd_read_fp (ptr->delay),
				ntohl (ptr->offset_int),
				ntohl (ptr->offset_frc),
				offset,
				ntpd_read_fp (ptr->dispersion));

		if (refclock_id != 1) /* not the system clock (offset will always be zero.. */
			ntpd_submit_reach ("time_offset", peername, ptr->reach,
					offset);
		ntpd_submit_reach ("time_dispersion", peername, ptr->reach,
				ntpd_read_fp (ptr->dispersion));
		if (refclock_id == 0) /* not a reference clock */
			ntpd_submit_reach ("delay", peername, ptr->reach,
					ntpd_read_fp (ptr->delay));
	}

	free (ps);
	ps = NULL;

	return (0);
} /* int ntpd_read */

void module_register (void)
{
	plugin_register_config ("ntpd", ntpd_config,
			config_keys, config_keys_num);
	plugin_register_read ("ntpd", ntpd_read);
} /* void module_register */
